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41356 Publications

Deposition of silicon oxide films on silicon using HelixJet – an atmospheric-pressure plasma jet process below 100 °C

Rebohle, L.; Quade, A.; Schumann, T.; Blaschke, D.; Hübner, R.; Heller, R.; Foest, R.; Schäfer, J.; Skorupa, W.

Silicon oxide films are widely applied for their superior dielectric, chemical and mechanic properties as well as for their resistance against reactive chemicals. Simultaneously, there is an increasing number of applications which demand a low deposition temperature. In this work, we compare the material properties of SiOx layers deposited at ca. 70°C by atmospheric-pressure plasma jet deposition (PA) with those of SiO2 layers thermally grown or deposited by plasma-enhanced chemical vapour deposition. The films were deposited on silicon wafers and analysed using different analysis techniques. According to cross-sectional transmission electron microscopy and high-frequency capacitance-voltage measurements, the interface between the PA oxide and the Si substrate is smooth with no apparent defects and displays an electrically active interface defect density between 3.5-8.0×1012 cm-2 directly after deposition and below 2.0×1012 cm-2 after furnace annealing. Right after deposition, the PA oxide contains carbon and hydrogen in a concentration of several at%, and the SiO2 plasma polymer network comprises several active centres (residual charge, free radicals, non-saturated bonds). The most abundant configuration is the Si(-O)4 tetrahedron, followed by Si(-O)3 with similar intensity. This indicates that there are still dangling Si bonds or bonds terminated by hydroxyl or methyl groups. After furnace annealing, the formation of the SiO2 network is completed and the optical and electrical properties of the PA oxide converge to that of thermal oxide.

Keywords: dielectric coating; insulation; corrosion protection; silicon oxide; atmospheric plasma source; thin films

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Permalink: https://www.hzdr.de/publications/Publ-33040
Publ.-Id: 33040


Data publication: Radiation damage evolution in pure W and W-Cr-Hf alloy caused by 5MeV Au ions in a broad range of dpa

Mackova, A.; Havranek, V.; Fernandes, S.; Matejicek, J.; Vilemova, M.; Holy, V.; Liedke, M. O.; Martan, J.; Vronka, M.; Potocek, M.; Babor, P.; Butterling, M.; Elsherif, A. G. A.; Hirschmann, E.; Wagner, A.

Positron annihilation lifetime spectroscopy data taking for ELBE proposal POS19101496 by Sandrina Fernandes, Rez, CZ. Role of open volume defects in irradiated structural materials for fusion applications. Measurements performed 16.3.2019 at the MePS facility.

Keywords: positron annihilation lifetime spectroscopy; SIMS; alloys; W Tungsten

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Permalink: https://www.hzdr.de/publications/Publ-33039
Publ.-Id: 33039


Rapid synthesis of gold-palladium core-shell aerogels for selective and robust electrochemical CO2 reduction

Du, R.; Jin, W.; Wu, H.; Hübner, R.; Zhou, L.; Xue, G.; Hu, Y.; Eychmüller, A.

Noble metal aerogels (NMAs), one class of the youngest members in the aerogel family, have drawn increasing attention in the last decade. Featuring the high catalytic activity of noble metals and a 3D self-supported porous network of the aerogels, they have displayed profound potential for electrocatalysis. However, considerable challenges reside in the rapid fabrication of NMAs with a well-tailored architecture, constraining the manipulation of their electrochemical properties for optimized performance. Here, a disturbance-assisted dynamic shelling strategy is developed, generating self-supported Au–Pd core–shell gels within 10 min. Based on suitable activation and desorption energies of the involved species as suggested by theoretical calculations, the Au–Pd core–shell aerogel manifests outstanding CO selectivity and stability at low overpotential (faradaic efficiency > 98% at -0.5 V vs. RHE over 12 hours) for the electrochemical CO2 reduction reaction (CO2RR). The present strategy offers a new perspective to facilely design architecture-specified high-performance electrocatalysts for the CO2RR.

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Permalink: https://www.hzdr.de/publications/Publ-33038
Publ.-Id: 33038


Integrated complementary inverters and ring oscillators based on vertical-channel dual-base organic thin-film transistors

Guo, E.; Xing, S.; Dollinger, F.; Hübner, R.; Wang, S.-J.; Wu, Z.; Leo, K.; Kleemann, H.

Lateral-channel dual-gate organic thin-film transistors have been used in pseudo complementary metal-oxide-semiconductor (CMOS) inverters to control switching voltage. However, their relatively long channel lengths, combined with the low charge carrier mobility of organic semiconductors, typically leads to slow inverter operation. Vertical-channel dual-gate organic thin-film transistors are a promising alternative because of their short channel lengths, but the lack of appropriate p- and n-type devices has limited the development of complementary inverter circuits. Here, we show that organic vertical n-channel permeable single- and dual-base transistors, and vertical p-channel permeable base transistors can be used to create integrated complementary inverters and ring oscillators. The vertical dual-base transistors enable switching voltage shift and gain enhancement. The inverters exhibit small switching time constants at 10 MHz, and the seven-stage complementary ring oscillators exhibit short signal propagation delays of 11 ns per stage at a supply voltage of 4 V.

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Permalink: https://www.hzdr.de/publications/Publ-33037
Publ.-Id: 33037


Data for: On Inter-bubble Distances and Bubble Clustering in Bubbly Flows: An Experimental Study

Kipping, R.; Hampel, U.

This data set contains the processed data from ultrafast X-ray tomography measurements in a bubble column. Measurements were performed in a bubble column with 100 mm inner diameter and with deionized water and nitrogen as liquid and gas phase, respectively. This data set contains the measurement from the measurement height located 0.7m above the gas sparger. 

Hydrodynamic data, such as bubble size distribution and gas holdup distribution are provided. Furthermore, inter-bubble distances of gas bubbles (distance of the nearest neighbours) are given.

Further detailes on the experiments and the processed data is provided in the corresponding journal paper.

Keywords: bubbly flows; clustering; UFXCT

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Permalink: https://www.hzdr.de/publications/Publ-33036
Publ.-Id: 33036


Data publication: FPGA-based Real-Time Data Acquisition for Ultrafast X-Ray Computed Tomography

Windisch, D.; Knodel, O.; Juckeland, G.; Hampel, U.; Bieberle, A.

This data contains the firmwares used for all descirbed tests in the paper.

Keywords: Computed tomography; Data acquisition; Field programmable gate arrays

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Permalink: https://www.hzdr.de/publications/Publ-33035
Publ.-Id: 33035


Evidence of collision-induced resuspension of microscopic particles from a monolayer deposit

Banari, A.; Henry, C.; Fank Eidt, R. H.; Pierre, L.; Klaus, Z.; Hampel, U.; Lecrivain, G.

The present Letter addresses the resuspension of microscopic glass particles from a monolayer bed into a turbulent gas flow. With an intermediate surface coverage, here set to about 10% of the field of view, we report two distinct detachment mechanisms. At relatively low flow velocities, few loosely adhering particles move on the wall to eventually collide with neighboring particles resulting in a clustered resuspension. At higher fluid velocities, mostly individual particles resuspend due to their interaction with the turbulent flow. The resuspension curve, showing the remaining particle fraction as a function of the flow velocity, exhibits a strong bimodal character.

Keywords: paticle resuspension; Inter-particle collisions; experimental test

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Permalink: https://www.hzdr.de/publications/Publ-33034
Publ.-Id: 33034


Fabrication and nanophotonic waveguide integration of silicon carbide colour centres with preserved spin-optical coherence

Babin, C.; Stöhr, R.; Morioka, N.; Linkewitz, T.; Steidl, T.; Wörnle, R.; Liu, D.; Hesselmeier, E.; Vorobyov, V.; Denisenko, A.; Hentschel, M.; Gobert, C.; Berwian, P.; Astakhov, G.; Knolle, W.; Majety, S.; Saha, P.; Radulaski, M.; Tien Son, N.; Ul-Hassan, J.; Kaiser, F.; Wrachtrup, J.

Optically addressable spin defects in silicon carbide (SiC) are an emerging platform for quantum information processing. Lending themselves to modern semiconductor nanofabrication, they promise scalable high-efficiency spin-photon interfaces. We demonstrate here nanoscale fabrication of silicon vacancy centres (VSi) in 4H-SiC without deterioration of their intrinsic spin-optical properties. In particular, we show nearly transform limited photon emission and record spin coherence times for single defects generated via ion implantation and in triangular cross section waveguides. For the latter, we show further controlled operations on nearby nuclear spin qubits, which is crucial for fault-tolerant quantum information distribution based on cavity quantum electrodynamics.

Keywords: Qubits; Silicon carbide; Quantum spintronics; Quantum photonics; Point defects

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Permalink: https://www.hzdr.de/publications/Publ-33033
Publ.-Id: 33033


Data and code for: A stable home: Autocorrelated Kernel Density Estimated home ranges of the critically endangered Elongated Tortoise

Montano, Y.; Michael Marshall, B.; Ward, M.; Simoes Silva, I. M.; Artchawakom, T.; Waengsothorn, S.; Strine, C. T.

Supplemental materials for A stable home: Autocorrelated Kernel Density Estimated home ranges of the critically endangered Elongated Tortoise on OSF Preprints, including data, code, figures and tables.

Keywords: ecology; testudine; autocorrelated kernel density estimator; spatial ecology; space use; Thailand; Indotestudo elongata

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  • Reseach data in external data repository
    Publication year 2021
    License: Creative Commons Attribution 4.0 International
    Hosted on OSF: Link to location

Permalink: https://www.hzdr.de/publications/Publ-33032
Publ.-Id: 33032


A stable home: Autocorrelated Kernel Density Estimated home ranges of the critically endangered Elongated Tortoise

Montano, Y.; Michael Marshall, B.; Ward, M.; Simoes Silva, I. M.; Artchawakom, T.; Waengsothorn, S.; Strine, C. T.

Home range is a fundamental concept in ecology used to describe animal space use over their lifetimes. Numerous studies use a variety of metrics to quantify home range; however, most of these treat spatial data inappropriately. Here we re-analyse a publicly available data-set, collected by the authors of this study, using a relatively novel and appropriate home range metric Autocorrelated Kernel Density Estimators (AKDE). Our data includes the movements of 17 Elongated Tortoises (Indotestudo elongata; 12 females, 5 males) located on average once every three days for an average duration of 353.76 ±33.10 days. We found 14 of 17 individuals appear to be occupying a stable home range (using variograms to determine range residency). We made use of AKDEs bias-mitigating measures to counteract the low effective sample sizes stemming from low temporal resolution radio-tracking data. The average AKDE home range for all 14 individuals with range residency was 44.81 ±10.44 ha. Bayesian Regression Models suggest considerable overlap between male and female home range estimates despite males being physically larger than females in both mass and carapace length. These home range estimates have the added utility of being comparable with other studies, less susceptible to errors from a suboptimal tracking regime, and are optimised with code and data for inclusion in future meta-analyses.

Keywords: ecology; testudine; autocorrelated kernel density estimator; spatial ecology; space use; Thailand; Indotestudo elongata

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Permalink: https://www.hzdr.de/publications/Publ-33031
Publ.-Id: 33031


Data and code for: Lots of movement, little progress: A review of reptile home range literature

Crane​, M.; Simoes Silva, I. M.; Marshall, B. M.; Strine​, C. T.

Datasets, R code and figures pertaining to the manuscript: Crane, M., Silva, I., Marshall, B. M., & Strine, C. T. (2021). Lots of movement, little progress: A review of reptile home range literature. PeerJ, 9, e11742. DOI: 10.7717/peerj.11742

Keywords: ecology; reptiles; home range; open science; reproducibility; biotelemetry; space use; spatial ecology

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Permalink: https://www.hzdr.de/publications/Publ-33030
Publ.-Id: 33030


Lots of movement, little progress: A review of reptile home range literature

Crane​, M.; Simoes Silva, I. M.; Marshall, B. M.; Strine​, C. T.

Reptiles are the most species-rich terrestrial vertebrate group with a broad diversity of life history traits. Biotelemetry is an essential methodology for studying reptiles as it compensates for several limitations when studying their natural history. We evaluated trends in terrestrial reptile spatial ecology studies focusing upon quantifying home ranges for the past twenty years. We assessed 290 English-language reptile home range studies published from 2000–2019 via a structured literature review investigating publications’ study location, taxonomic group, methodology, reporting, and analytical techniques. Substantial biases remain in both location and taxonomic groups in the literature, with nearly half of all studies (45%) originating from the USA. Snakes were most often studied, and crocodiles were least often studied, while testudines tended to have the greatest within study sample sizes. More than half of all studies lacked critical methodological details, limiting the number of studies for inclusion in future meta-analyses (55% of studies lacked information on individual tracking durations, and 51% lacked sufficient information on the number of times researchers recorded positions). Studies continue to rely on outdated methods to quantify space-use (including Minimum Convex Polygons and Kernel Density Estimators), often failing to report subtleties regarding decisions that have substantial impact on home range area estimates. Moving forward researchers can select a suite of appropriate analytical techniques tailored to their research question (dynamic Brownian Bridge Movement Models for within sample interpolation, and autocorrelated Kernel Density Estimators for beyond sample extrapolation). Only 1.4% of all evaluated studies linked to available and usable telemetry data, further hindering scientific consensus. We ultimately implore herpetologists to adopt transparent reporting practices and make liberal use of open data platforms to maximize progress in the field of reptile spatial ecology.

Keywords: ecology; reptiles; home range; open science; reproducibility; biotelemetry; space use; spatial ecology

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Permalink: https://www.hzdr.de/publications/Publ-33029
Publ.-Id: 33029


Indirect bandgap, optoelectronic properties, and photoelectrochemical characteristics of high-purity Ta₃N₅ photoelectrodes

Eichhorn, J.; Lechner, S. P.; Jiang, C.-M.; Folchi, G.; Munnik, F.; Sharp, I. D.

The (opto)electronic properties of Ta3N5 photoelectrodes are often dominated by defects, such as oxygen impurities, nitrogen vacancies, and reduced tantalum centers, impeding fundamental studies of its electronic structure, chemical stability, and photocarrier transport. Here, we synthesize high quality Ta3N5 thin films by reactive magnetron sputtering and subsequent NH3 annealing at varying temperatures. The resulting films are characterized by nearly-ideal N/Ta stoichiometry, low O content, and small Urbach energies. Both the crystallinity and material quality improve with increasing annealing temperatures up to 940 °C, while higher annealing temperatures introduce additional disorder within the Ta3N5 lattice, leading to reduced photoelectrochemical performance. These changes are also reflected in the surface and bulk composition, showing the elimination of oxygen impurities at moderate annealing temperatures and the loss of nitrogen at high annealing temperatures. As a consequence, defect-related sub-gap optical absorption initially decreases due to reduced oxygen impurity concentration, and subsequently increases due to increased formation of nitrogen vacancies. The high material quality enables us to unambiguously identify the nature of the Ta3N5 band gap as indirect, thereby resolving a long-standing controversy regarding the most fundamental characteristic of this material as a semiconductor. The assignment of Ta3N5 as indirect semiconductor is further supported by the suppression of disorder-induced band-edge photoluminescence with improved structural order within the Ta3N5 films.

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Permalink: https://www.hzdr.de/publications/Publ-33028
Publ.-Id: 33028


Simulating Multi Layer Targets for Grazing Incidence Small Angle X-ray Scattering

Paschke-Brühl, F.-L.

This bachelor thesis studies the feasibility of grazing-incidence small-angle x-ray scattering
(GISAXS) in the UHI laser-target interaction via computational simulations with SMILEI. In
this work we briefly analyze the front and back of the target. We find predominantly that the
compression of the target becomes apparent in the GISAXS pattern, while we can not observe
ablation. We will mainly focus on the density oscillation, a dynamic that has not been mentio-
ned in literature yet. The density oscillation dynamics depend on a simple pressure gradient
in between the layers. We observe the multi layers inversely oscillating in density and a global
density alteration moving through the target. The density alteration allows to recognize the
dynamic in a GISAXS pattern. We learn, that GISAXS is feasible in the high intensity regime,
but not for the same dynamics as in the lower intensity regime.

Keywords: GISAXS; SAXS; grazing-incidence small-angle x-ray scattering; SMILEI; Simulation; Density Oscialltion

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Permalink: https://www.hzdr.de/publications/Publ-33027
Publ.-Id: 33027


Simulating Multi Layer Targets for Grazing Incidence Small Angle X-ray Scattering

Paschke-Brühl, Franziska-Luise

This bachelor thesis studies the feasibility of grazing-incidence small-angle x-ray scattering
(GISAXS) in the UHI laser-target interaction via computational simulations with SMILEI. In
this work we briefly analyze the front and back of the target. We find predominantly that the
compression of the target becomes apparent in the GISAXS pattern, while we can not observe
ablation. We will mainly focus on the density oscillation, a dynamic that has not been mentio-
ned in literature yet. The density oscillation dynamics depend on a simple pressure gradient
in between the layers. We observe the multi layers inversely oscillating in density and a global
density alteration moving through the target. The density alteration allows to recognize the
dynamic in a GISAXS pattern. We learn, that GISAXS is feasible in the high intensity regime,
but not for the same dynamics as in the lower intensity regime.

Keywords: GISAXS; SAXS; grazing incidence small angle x-ray scattering; SMILEI; Simulation; Density Oscillation

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Permalink: https://www.hzdr.de/publications/Publ-33026
Publ.-Id: 33026


Radiation damage evolution in pure W and W-Cr-Hf alloy caused by 5MeV Au ions in a broad range of dpa

Mackova, A.; Havranek, V.; Fernandes, S.; Matejicek, J.; Vilemova, M.; Holy, V.; Liedke, M. O.; Martan, J.; Vronka, M.; Potocek, M.; Babor, P.; Butterling, M.; Elsherif, A. G. A.; Hirschmann, E.; Wagner, A.

Pure W and W-Cr-Hf alloy which are prospective materials for nuclear fusion reactors, such as DEMO,
were irradiated at room temperature with 5 MeV Au2+ ions with fluences between 4 × 1014 and 1.3
× 1016 ions.cm-2 to generate various levels of lattice damage from about units up to tens of dpa. The distinct
character of radiation damage accumulation, microstructure and defect nature have been observed in
both pure W and W-Cr-Hf alloys, the latter exhibited interesting ability of damage reorganisation and
defect size decrease at the higher ion fluences as determined by positron annihilation spectroscopy (PAS),
X-ray diffraction analysis (XRD) identified vertical grain size modification as a function of the Au-ion
fluence. Originally more strained subsurface layer influenced by polishing procedure exhibited the defect
and strain release with the increased Au-ion irradiation fluence in both materials. Radiation damage
saturation has been observed in the deep buried layer at the lower Au-ion fluences in the W-samples
compared to W-Cr-Hf samples; contrary for the higher Au-ion fluence a slight damage decrease was
evidenced in W-Cr-Hf alloys. The distinct defect accumulation was accompanied with the different Au-ion, implanted distribution in the irradiated layer determined by Secondary Ion Mass Spectrometry (SIMS) as
well as the thermal properties have shown the consequent worsening in the depth in good agreement
with the Au-depth concentration profiles. TEM corroborated above mentioned findings, where the subsurface
layer exhibited defect release after the irradiation, the maximum of dislocation loop density has
been identified in the depth according the predicted dpa (displacement particles per atom) maximum for
the lower Au-ion fluences. Moreover, TEM shows the dislocation density band structure appeared in WCr-
Hf samples exhibiting the high density defect band according the projected range of the Au-ions
simultaneously with the additional layer with larger isolated dislocations pronounced in the higher depth
as a growing function of Au-ion ion fluence. Such phenomenon was not observed in W samples.

Keywords: positron annihilation lifetime spectroscopy; SIMS; alloys; W Tungsten

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Permalink: https://www.hzdr.de/publications/Publ-33025
Publ.-Id: 33025


On Inter-bubble Distances and Bubble Clustering in Bubbly Flows: An Experimental Study

Kipping, R.; Wagner, M.; Hampel, U.

Swarm effects in bubble columns result from the interaction of the bubbles at higher gas holdup. The flow around individual bubbles in a swarm influences the movement of the following bubbles and this has a feedback on the flow regime on a larger scale. That is, hydrodynamics that can no longer be described with models for single rising bubbles. The experimental investigation of the multiscale hydrodynamics in three-dimensional bubble columns was so far limited by the available measurement techniques. In this study, ultrafast X-ray tomography (UFXCT) was applied on bubbly flows in a lab scale bubble column to determine inter-bubble distances and clustering characteristics for different gas holdups and bubble diameters. Applying the pair correlation function reveals a pronounced vertical clustering for large bubbles with Eo ≥ 3.82, whereas no clustering has been observed for bubbles of lower Eo. It was found that clustering orientation mainly depends on deformability of the bubbles but not on gas holdup.

Keywords: bubbly flows; ultrafast X-ray tomography; inter-bubble distances; pair correlation function; bubble clustering

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Permalink: https://www.hzdr.de/publications/Publ-33024
Publ.-Id: 33024


NeuLAND: The High-Resolution Neutron Time-of-Flight Spectrometer for R³B at FAIR

Boretzky, K.; Gašparic, I.; Heil, M.; Mayer, J.; Heinz, A.; Caesar, C.; Kresan, D.; Simon, H.; Törnqvist, H. T.; Körper, D.; Alkhazov, G.; Atar, L.; Aumann, T.; Bemmerer, D.; Bondarev, S. V.; Bott, L. T.; Chakraborty, S.; Cherciu, M. I.; Chulkov, L. V.; Ciobanu, M.; Datta, U.; de Filippo, E.; Douma, C. A.; Dreyer, J.; Elekes, Z.; Enders, J.; Galaviz, D.; Geraci, E.; Gnoffo, B.; Göbel, K.; Golovtsov, V. L.; Gonzalez Diaz, D.; Gruzinsky, N.; Haiduc, M.; Heftrich, T.; Heggen, H.; Hehner, J.; Hensel, T.; Hoemann, E.; Holl, M.; Horvat, A.; Horváth, Á.; Ickert, G.; Ignatov, A.; Jelavi Malencia, D.; Johansson, H. T.; Jonson, B.; Kahlbow, J.; Kalantar-Nayestanaki, N.; Kelic-Heil, A.; Kempe, M.; Koch, K.; Kozlenko, N. G.; Krivshich, A. G.; Kurz, N.; Kuznetsov, V.; Langer, C.; Leifels, Y.; Lihtar, I.; Löher, B.; Machado, J.; Martorana, N. S.; Miki, K.; Nilsson, T.; Nyman, G. H.; Orischin, E. M.; Pagano, E. V.; Pirrone, S.; Politi, G.; Potlog, P.-M.; Rahaman, A.; Reifarth, R.; Rigollet, C.; Röder, M.; Rossi, D. M.; Russotto, P.; Savran, D.; Scheit, H.; Schindler, F.; Stach, D.; Stan, E.; Stomvall Gill, J.; Teubig, P.; Trimarchi, M.; Uvarov, L.; Volknandt, M.; Wagner, A.; Wagner, V.; Wranne, S.; Yakorev, D.; Zanetti, L.; Zilges, A.; Zuber, K.

NeuLAND (New Large-Area Neutron Detector) is the next-generation neutron detector for the R3B (Reactions with Relativistic Radioactive Beams) experiment at FAIR (Facility for Antiproton and Ion Research). NeuLAND detects neutrons with energies from 100 to 1000 MeV, featuring a high detection efficiency, a high spatial and time resolution, and a large multi-neutron reconstruction efficiency. This is achieved by a highly granular design of organic scintillators: 3000 individual submodules with a size of 5x5x250 cm3 are arranged in 30 double planes with 100 submodules each, providing an active area of 250x250 cm2 and a total depth of 3 m. The spatial resolution due to the granularity together with a time resolution of 150 ps ensures high-resolution capabilities. In conjunction with calorimetric properties, a multi-neutron reconstruction efficiency of 50% to 70% for four-neutron events will be achieved, depending on both the emission scenario and the boundary conditions allowed for the reconstruction method. We present in this paper the final design of the detector as well as results from test measurements and simulations on which this design is based.

Keywords: high-energy neutron detection; reactions with relativistic radioactive beams; plastic scintillator scintillator array; multi-neutron detection

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Permalink: https://www.hzdr.de/publications/Publ-33023
Publ.-Id: 33023


Strategic Evaluation of the Traceless Staudinger Ligation for Radiolabeling with the Tricarbonyl Core

Mamat, C.; Jentschel, C.; Köckerling, M.; Steinbach, J.

The traceless Staudinger Ligation with its two variants is a powerful biorthogonal conjugation method not only for the connection of biomolecules, but also for the introduction of fluores-cence or radiolabels under mild reaction conditions. Herein, the strategic evaluation of the traceless Staudinger Ligation for Radiolabeling 99mTc using the [Tc(CO)3] core was presented. A convenient and high-yielding three-step synthesis procedure of dipicolylamine-based phos-phanols as ligands for the mild radiolabeling was developed. The labeling was accomplished using a tricarbonyl kit and 99mTc-pertechnetate generator eluate showing 87% radiochemical conversion. The respective rhenium-based, non-radioactive reference compounds were synthe-sized using (Et4N)2[Re(CO)3Br3] as precursor. All products were analyzed by NMR, MS and ele-mental analysis. Additional XRD analyses were performed.

Permalink: https://www.hzdr.de/publications/Publ-33021
Publ.-Id: 33021


Stability analysis of discrete population balance model for bubble growth and shrinkage

Li, J.; Liao, Y.; Lucas, D.; Zhou, P.

The stability condition for solving the population balance equation (PBE) involving bubble growth and shrinkage within the Eulerian framework is proposed. The particle flux weighted average Courant number, CCFL, which reflects the propagation of particle state of the entire size classes on internal coordinates is first derived. Stability conditions of internal convection for PISO and PIMPLE algorithms are obtained by evaluating a series of tests concerning the constant bubble growth. The proposed stability conditions are then applied to simulate two kinds of laboratory experiments, i.e. the bubble growth in stagnant liquid and condensing steam-water pipe flows. The results show that the stable PBE solutions hold for the cases using either PISO or PIMPLE algorithms combined with the corresponding stability condition. Meanwhile, the conservation of the zeroth and first moments of the number density function can be guaranteed when the stability condition is satisfied. In addition, the effect of heat transfer coefficient correlations is also discussed.

Keywords: Stability analysis; Internal CFL condition; Discretization; Population balance equation; Class method; Phase change

Permalink: https://www.hzdr.de/publications/Publ-33020
Publ.-Id: 33020


Acoustically induced coherent spin trapping

Hernandez-Minguez, A.; Poshakinskiy, A. V.; Hollenbach, M.; Santos, P. V.; Astakhov, G.

Hybrid spin-optomechanical quantum systems offer high flexibility, integrability and applicability for quantum science and technology. Particularly, on-chip surface acoustic waves (SAWs) can efficiently drive spin transitions in the ground states (GSs) of atomic-scale, color centre qubits, which are forbidden in case of the more frequently used electromagnetic fields. Here, we demonstrate that strain-induced spin interactions within their optically excited state (ES) can exceed by two orders of magnitude the ones within the GS. This gives rise to novel physical phenomena, such as the acoustically induced coherent spin trapping (CST) unvealed here. The CST manifests itself as the spin preservation along one particular direction under the coherent drive of the GS and ES by the same acoustic field. Our findings provide new opportunities for the coherent control of spin qubits with dynamically generated strain fields that can lead towards the realization of future spin-acoustic quantum devices.

Keywords: Spin qubits; surface acoustic waves; quantum technology; SiC

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Permalink: https://www.hzdr.de/publications/Publ-33018
Publ.-Id: 33018


Laser-induced ionization of ions from liquid alloy ion sources of high brightness

Machalett, F.; Ying, B.; Wustelt, P.; Huth, V.; Kübel, M.; Bischoff, L.; Klingner, N.; Pilz, W.; Stöhlker, T.; Paulus, G. G.

In this work, we have generated ion beam targets of metal and metalloid ions using a high-brightness liquid metal ion source (LMIS) originally applied in focused ion beam systems. Using an eutectic Au-Si alloy as a low melting point source feed material, ions of different ion species were detected: Si^{2+}, Si^+, Au^{2+}, Au^+, Au^{2+}, Au^{3+} and Au^{32+}. The source current between emitter needle and extractor electrode is in the range of 10 - 60 μA and can be adjusted up to about 150 μA. The ion source is characterized by high ion current stability and a suitable emission lifetime of several days, which is limited by the amount of material and can be further increased.
To study the strong-field laser ionization, we used a E x B filter and selected Si^{2+} and Au+ ions as ionic targets, because of their high beam intensity. We investigated ultrafast laser-induced ionization, which leads to higher charge states after multiple ionization of both ion species. Laser intensities of up to 10^{16} W/cm^2 allow observation of up to 10-fold ionization of Au^+ ions and 3-fold ionization of Si^{2+} ions.
The aim of further work is to extend the available ion beam targets to other elements of the periodic table to study ultrafast laser-induced fragmentation and ionization dynamics of atoms and molecules in strong laser fields. Another goal is the further increase of the density of ion laser targets for more reliable statistics and shorter measurement times. Further steps are technical improvements of ion source and ion optics as well as the investigation of heavy metal dimers such as Au^{2+}.

Keywords: liquid metal ion source; laser intensity; ultrafast laser-induced fragmentation; ionization dynamics

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  • Lecture (Conference) (Online presentation)
    18th SPARC Topical Workshop, 06.-09.09.2021, Darmstadt, Germany

Permalink: https://www.hzdr.de/publications/Publ-33017
Publ.-Id: 33017


Laser-induced ionization of ions from high brightness ion sources

Machalett, F.; Ying, B.; Wustelt, P.; Huth, V.; Kübel, M.; Bischoff, L.; Klingner, N.; Pilz, W.; Stöhlker, T.; Paulus, G. G.

Au and Si ions from high brightness liquid metal ion sources (LMIS) are used as ionic targets for strong-field laser interaction with femtosecond laser beam. Field ionization processes in the field emission source at electrostatic fields of some 10 V/nm allow the generation of various metallic and metalloid ion beams with charge states such as Au^{2+} and Si^{2+}. Studying the ionization in strong femtosecond laser fields with intensities of up to 1E16 W/cm^2, we observed for these elements charge states up to Au^{11+} and Si^{4+}.

Keywords: liquid metal ion sources; femtosecond laser beam; charge states

Related publications

  • Lecture (Conference) (Online presentation)
    32nd International Conference on Photonic, Electronic and Atomic Collisions, ViCPEAC2021, 20.-23.07.2021, European XFEL, Germany

Permalink: https://www.hzdr.de/publications/Publ-33016
Publ.-Id: 33016


Experimental and numerical investigations of Ni–Co–SiO2 alloy films deposited by magnetic-field-assisted jet plating

Jiang, W.; Huang, M.; Lao, Y.; Yang, X.; Wang, C.; Tian, Z.; Zhou, S.; Mutschke, G.; Eckert, K.

A new method of magnetic-field-assisted jet plating is presented to manufacture Ni-Co-SiO2 alloy films. The influence of different concentrations of Co2+ ions of the electrolyte is investigated with and without magnetic field to study the resulting properties of the deposits. The texture orientation, surface morphology, magnetic properties and corrosion resistance of the alloy films were characterized. The results show that with increasing Co2+ concentration in conventional jet-plating, the surface morphology changes from a granular crystal structure to a needle-like structure at 30 g/L caused by the hexagonal close-packed (HCP) structure of a large Co content. Differently, the assistance of the magnetic field leads to lower Co content in the films, even at a high Co2+ concentration of 30 g/L. The deposit layer remains in the face-centered cubic (FCC) structure and shows a granular morphology. The magnetic field in general leads to grain refinement and inhibits the abnormal Ni–Co co-deposition. The Ni–Co–SiO2 alloy films obtained by magnetic-field-assisted jet plating have a smooth and dense surface. The best soft magnetic properties and corrosion resistance are obtained at a Co2+ concentration of 20 g/L. The coercivity is as low as 7.5 Oe, and the corrosion current density is as low as 1.12 μA·cm-2 in 3.5 wt% NaCl solution without agitation and at room temperature, clearly showing the advantages of the method for preparing superior soft magnetic materials. In addition, a physical model of magnetic-field-assisted jet plating is established. The magnetic forces and the resulting electrolyte flow are analyzed with the help of numerical simulations, and the influence of the magnetic field on the deposition process is discussed from the perspective of magnetohydrodynamics.

Keywords: Ni–Co–SiO2 alloy film; Magnetic-field-assisted jet plating; Magnetic properties; Numerical simulation

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Permalink: https://www.hzdr.de/publications/Publ-33014
Publ.-Id: 33014


Increased dephasing length in heavily doped GaAs

Duan, J.; Wang, C.; Vines, L.; Rebohle, L.; Helm, M.; Zeng, Y.-J.; Zhou, S.; Prucnal, S.

Ion implantation of S and Te followed by sub-second flash lamp annealing with peak temperature about 1100 oC is employed to obtain metallic n++-GaAs layers. The electron concentration in annealed GaAs is as high as 5×1019 cm-3, which is several times higher than the doping level achievable by alternative methods. We found that heavily doped n++-GaAs exhibits positive magnetoconductance in the temperature range of 3-80 K, which is attributed to the magnetic field suppressed weak localization. By fitting the magnetoconductance results with Hikami-Larkin-Nagaoka model, it is found that the phase coherence length increases with increasing carrier concentration at low temperature and is as large as 540 nm at 3 K. The temperature dependence of the phase coherence length follows〖 l〗_∅∝T^η (η~0.3), indicating defect-related scattering as the dominant dephasing mechanism. In addition, the high doping level in n-type GaAs provides the possibility to use GaAs as a plasmonic material for chemical sensors operating in the infrared range.

Keywords: ion implantation; heavily doped GaAs; phase coherence length; sub-second annealing; plasmonic

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Permalink: https://www.hzdr.de/publications/Publ-33012
Publ.-Id: 33012


Software publication: Automated coordination corrected enthalpies with AFLOW-CCE

Friedrich, R.; Esters, M.; Oses, C.; Ki, S.; Brenner, M. J.; Hicks, D.; Mehl, M. J.; Toher, C.; Curtarolo, S.

The implementation of the coordination corrected enthalpies (CCE) method is available via the AFLOW software for materials discovery as the AFLOW-CCE module.

Keywords: materials themrodynamics; enthalpy correction; materials design

Related publications

  • Software in external data repository
    Publication year 2021
    Programming language: C++
    System requirements: Unix
    License: GNU General Public License version 3
    Hosted on AFLOW: Link to location

Permalink: https://www.hzdr.de/publications/Publ-33011
Publ.-Id: 33011


Supplementary material: Ph.D. dissertation of Lucas Pereira, TU Bergakademie Freiberg, 2021.

Pereira, L.
Supervisor: Frenzel, Max; Supervisor: Tolosana-Delgado, Raimon; Supervisor: Gutzmer, Jens

This supplementary material supports the Ph.D. dissertation of Lucas Pereira, submitted to the Faculty 3 of the TU Bergakademie Freiberg.

C2.SM1.Percentiles.xlsx: Mentioned in the chapter 2 of the dissertation, this file contains, in terms of percentiles, the distribution of every particle descriptive variable in the different samples used to train the logistic regression models of the case study presented in this chapter.

C2.SM2.Coefficients.xlsx: Mentioned in the chapter 2 of the dissertation, this file contains the complete list of coefficients assigned to each variable, in each separation unit, of the case study presented in this chapter.

C4.SM1.StatWeight.xlsx: Mentioned in the chapter 4 of the dissertation, this file contains a detailed explanation of the statistical weights of particles and how they can be used to integrate a set of particle datasets from different streams and size fractions into a single and balanced training dataset.

Keywords: Geometallurgy; Particle-based separation model

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Permalink: https://www.hzdr.de/publications/Publ-33009
Publ.-Id: 33009


How 5f electron polarizability drives covalency and selectivity in actinide N-donor complexes

Köhler, L.; Patzschke, M.; Schmidt, M.; Stumpf, T.; März, J.

We report a series of isostructural tetravalent actinide (Th, U-Pu) complexes with the N-donor ligand N,N'-ethylene-bis((pyrrole-2-yl)methanimine) (H₂ L, H₂ pyren). Structural data from SC-XRD analysis reveal [An(pyren)₂ ] complexes with different An–N(imine) vs. An–N(pyrrolide) bond lengths, respectively. Quantum chemical calculations elucidate the bonding situation, including differences in covalent character of the coordinative bonds. A comparison to the intensely studied analogous N,N′‐ethylene‐bis(salicylideneimine) (H₂ salen) based complexes [An(salen)₂ ] displays on average almost equal electron sharing of pyren or salen with the An(IV), pointing to a potential ligand-cage-driven complex stabilization. This is shown in the fixed ligand arrangement of pyren and salen in the respective An(IV) complexes. The overall bond strength of the pure N-donor ligand pyren to An(IV) (An=Th, U, Np, Pu) is slightly weaker compared to salen, with the exception of the Pa(IV) complex, which exhibits extraordinarily high electron sharing of pyren with Pa(IV). Such an altered ligand preference within the early An(IV) series points to a specificity of the 5f¹ configuration, which can be explained by polarization effects of the 5f electrons, allowing strongest f electron backbonding from Pa(IV) (5f¹ ) to the N-donors of pyren.

Keywords: actinides; N donor ligands; bonding analysis; f electrons; pyrrole

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Permalink: https://www.hzdr.de/publications/Publ-33008
Publ.-Id: 33008


On the nature of Pb species in Pb-(over)exchanged zeolite: a combined experimental and theoretical study

Roos, D. P.; Scheinost, A.; Churakov, S. V.; Nagashima, M.; Cametti, G.

Structural properties of Pb-exchanged zeolites are of interest because of their applications in environmental remediation and in industrial processes. In this study, we report on a Pb-exchanged aluminosilicate zeolite (Pb-STI), with particular focus on the cationic species, which form inside the zeolitic pores as a result of the exchange experiments. The produced
zeolite had chemical composition Pb13.4(OH)10Al17.4Si54.6O144 ∙38H2O, indicating a Pb2+ overexchange of approximately 50%. The STI framework maintained the Fmmm space group characteristic of the type material. However, the extraframework occupants, Pb2+, H2O and OH-, were characterized by a strong positional-disorder. The latter was resolved and
interpreted combining Extended X-ray Absorption Fine Structure (EXAFS) analysis with Molecular Dynamics (MD) simulations. On average, Pb2+ ions are coordinated by 2 OH- and
1 H2O at distances < 2.5 Å, whereas bonds to framework oxygen-atoms were found only at longer distances (> 2.8 Å). Pb2+ adopts mainly a sided distorted coordination, indicating a
stereochemical activity of the lone pair electrons. The obtained results were compared with those of other mono-cationic forms of STI zeolites. Based on the analysis of the framework
distortion experienced after the incorporation of different metal ions, considerations are drawn on the potential effect of Pb2+ on the thermal stability of STI framework type zeolites.

Keywords: XAFS; Zeolite; XRD; Molecular dynamics; DFT

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Permalink: https://www.hzdr.de/publications/Publ-33007
Publ.-Id: 33007


Automated coordination corrected enthalpies with AFLOW-CCE

Friedrich, R.; Esters, M.; Oses, C.; Ki, S.; Brenner, M. J.; Hicks, D.; Mehl, M. J.; Toher, C.; Curtarolo, S.

The computational design of materials with ionic bonds poses a critical challenge to thermodynamic modeling
since density functional theory yields inaccurate predictions of their formation enthalpies. Progress requires
leveraging physically insightful correction methods. The recently introduced coordination corrected enthalpies
(CCE) method delivers accurate formation enthalpies with mean absolute errors close to room temperature
thermal energy, i.e., ≈25 meV/atom. The CCE scheme, depending on the number of cation-anion bonds and
oxidation state of the cation, requires an automated analysis of the system to determine and apply the correction.
Here, we present AFLOW-CCE—our implementation of CCE into the AFLOW framework for computational
materials design. It features a command line tool, a web interface, and a Python environment. The workflow
includes a structural analysis, automatically determines oxidation numbers, and accounts for temperature effects
by parametrizing vibrational contributions to the formation enthalpy per bond.

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Permalink: https://www.hzdr.de/publications/Publ-33006
Publ.-Id: 33006


Compact spectroscopy of keV to MeV X-rays from a laser wakefield accelerator

Hannasch, A.; Laso García, A.; La Berge, M.; Zgadzaj, R.; Köhler, A.; Couperus Cabadağ, J. P.; Zarini, O.; Kurz, T.; Ferrari, A.; Molodtsova, M.; Naumann, L.; Cowan, T.; Schramm, U.; Irman, A.; Downer, M.

We reconstruct spectra of secondary X‑rays from a tunable 250–350 MeV laser wakefield electron accelerator from single‑shot X‑ray depth‑energy measurements in a compact (7.5 × 7.5 × 15 cm), modular X‑ray calorimeter made of alternating layers of absorbing materials and imaging plates. X‑rays range from few‑keV betatron to few‑MeV inverse Compton to > 100 MeV bremsstrahlung emission, and are characterized both individually and in mixtures. Geant4 simulations of energy deposition of single‑energy X‑rays in the stack generate an energy‑vs‑depth response matrix for a given stack configuration. An iterative reconstruction algorithm based on analytic models of betatron, inverse Compton and bremsstrahlung photon energy distributions then unfolds X‑ray spectra,
typically within a minute. We discuss uncertainties, limitations and extensions of both measurement and reconstruction methods.

Permalink: https://www.hzdr.de/publications/Publ-33005
Publ.-Id: 33005


Data publication: Broadband frequency filters with quantum dot chains

Ehrlich, T.; Schaller, G.

Rohdaten für Abbildungen (*.agr) und Mathematica Notebooks (*.nb) für die Berechnungen

Keywords: thermodynamic uncertainty relation; Levitov-Lesovik formula; transmission; reaction-coordinate mapping

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Permalink: https://www.hzdr.de/publications/Publ-33004
Publ.-Id: 33004


Automated mineralogy particle dataset: dry magnetic separation of skarn ore

Buchmann, M.; Kern, M.; Pereira, L.; Frenzel, M.; Tolosana Delgado, R.; van den Boogaart, K. G.; Gutzmer, J.

This data set origins from the AFK (“Aufbereitung feinkörniger Komplexerze”, BMBF grant number 033R128) project. The main target within this project was to produce a cassiterite concentrate, which is suitable for the subsequent production of tin. Various processing steps and the material specific behaviour were investigated within the progress of the project. The present data set derives from dry magnetic separation tests. More information can be found in the "readme.pdf" file attached.

Keywords: Geometallurgy; Particle-based separation modelling; Magnetic separation; Cassiterite

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Permalink: https://www.hzdr.de/publications/Publ-33003
Publ.-Id: 33003


Data publication: Microscopic and spectroscopic bioassociation study of uranium(VI) with an archaeal Halobacterium isolate

Hilpmann, S.; Bader, M.; Steudtner, R.; Müller, K.; Stumpf, T.; Cherkouk, A.

Bei diesem Datensatz handelt es sich um die Primärdaten der Untersuchung der Wechselwirkungen eines halophilen Archaeons mit Uran(VI). Dazu wurden Konzentrationsbestimmungen mittels ICP-MS durchgeführt, Lumineszenzspektren mittels zeitaufgelöster laserinduzierter Lumineszenzspektroskopie und IR Spektren aufgenommen. Darüber hinaus wurden Bilder der Zellen mit Hilfe der Fluoreszenzmikroskopie aufgenommen.

Keywords: uranium(VI) bioassociation; halophilic archaea; rock salt

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Permalink: https://www.hzdr.de/publications/Publ-33002
Publ.-Id: 33002


Monte Carlo methods in particle and nuclear physics

Müller, S.

Presentation at HZDR's 2021 summer student seminar

Keywords: Monte Carlo; Simulation

  • Lecture (Conference) (Online presentation)
    Summer Student seminar series, 27.07.2021, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-33001
Publ.-Id: 33001


Microscopic and spectroscopic bioassociation study of uranium(VI) with an archaeal Halobacterium isolate

Hilpmann, S.; Bader, M.; Steudtner, R.; Müller, K.; Stumpf, T.; Cherkouk, A.

The safe disposal of high-level radioactive waste in a deep geological repository is a huge social and scientific issue. So far, one of the less considered factors, especially in terms of a long-term risk assessment, is the impact of microorganisms occurring in the different host rocks. Even under the harsh conditions of salt formations different bacterial and archaeal species were found, e. g. Halobacterium sp. GP5 1-1, which has been isolated from a German rock salt sample. The interactions of this archaeon with uranium(VI), one of the major radionuclides of concern for the long-term storage of high-level radioactive waste, were investigated. Different spectroscopic techniques, as well as microscopy, were used to examine the occurring mechanisms on a molecular level leading to a more profound process understanding. Batch experiments with different uranium(VI) concentrations showed that the interaction is not only a simple, but a more complex combination of different processes. With the help of in situ attenuated total reflection Fourier-transform infrared spectroscopic investigations the association of uranium(VI) onto carboxylate groups was verified. In addition, time-resolved laser-induced luminescence spectroscopic investigations revealed the formation of a phosphate and carboxylate species within the cell pellets in dependence on the uranium(VI) concentration and the incubation time. Furthermore, the association behavior differs from another very closely related halophilic archaeon, especially with regard to uranium(VI) concentrations. This clearly demonstrates the importance of studying the interactions of different, at first sight very similar, microorganisms with uranium(VI). Overall, the findings presented in this work provide new insights into the microbe-uranium(VI) interactions at highly saline conditions relevant to the long-term storage of radioactive waste in rock salt.

Keywords: uranium(VI) bioassociation; halophilic archaea; rock salt

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Permalink: https://www.hzdr.de/publications/Publ-33000
Publ.-Id: 33000


FPGA-based Real-Time Data Acquisition for Ultrafast X-Ray Computed Tomography

Windisch, D.; Knodel, O.; Juckeland, G.; Hampel, U.; Bieberle, A.

Ultrafast X-ray computed tomography (UFXCT) is a fast tomographic imaging technique based on the principle of electron beam scanning. It is used for the investigation of transient multiphase flows. A UFXCT scanner comprises of multiple detector modules generating gigabytes of raw data per second for imaging rates of up to 8,000 frames per second. During the data acquisition, this data is stored in RAM on each detector module and can therefore only be accessed after the acquisition. This limits applicability of UFXCT systems because real-time control of the scanned process or the scanner itself is not possible. Using the newly developed FPGA-based data acquisition described in this paper, the data acquisition is enhanced to real-time operation, i.e., streaming the acquired data to the processing computer within microseconds of their acquisition. The developed FPGA firmware handles control of peripherals (such as analog-digital converters), synchronization between detector modules, electron beam deflection, and data transfer via gigabit ethernet.

Keywords: Computed tomography; Data acquisition; Field programmable gate arrays

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Permalink: https://www.hzdr.de/publications/Publ-32999
Publ.-Id: 32999


P2001 - Vorrichtung zur gezielten Anordnung von in einem Analyten gelösten, elektrisch polarisierbaren Materialien, Verfahren zur Bestimmung eines isoelektrischen Punktes eines elektrisch isolierenden Materials, Verfahren zum gezielten Anordnen eines in einem Analyten gelösten elektrisch polarisierbaren Materials

Rebohle, L.; Fischer, C.; Skorupa, I.; Schmidt, H.; Krüger, S.; Blaschke, D.

Es wird eine Vorrichtung (10) zur gezielten Anordnung eines in einem Analyten gelösten, elektrisch polarisierbaren Materials (4), aufweisend eine siliziumhaltige Trägerstruktur (3), eine elektrisch isolierende erste Deckstruktur (1) mit einem ersten isoelektrischen Punkt und eine elektrisch isolierende zweite Deckstruktur (2) mit einem zweiten isoelektrischen Punkt vorgeschlagen, wobei der erste isoelektrische Punkt vom zweiten isoelektrischen Punkt verschieden ist. Weiterhin werden ein Verfahren zur Bestimmung eines ersten isoelektrischen Punktes eines Materials sowie ein Verfahren zum gezielten Anordnen eines in einem Analyten gelösten, elektrisch polarisierbaren Materials (4) vorgeschlagen.

  • Patent
    DE102020200470 - Erteilung 20.05.2021; Nachanmeldungen: WO

Permalink: https://www.hzdr.de/publications/Publ-32998
Publ.-Id: 32998


P1916 - Verfahren und Anordnung zum Charakterisieren der Positionierung eines Objekts

Hampel, U.

Die Erfindung betrifft ein Verfahren und eine Anordnung zum Charakterisieren der Positionierung eines Objekts innerhalb eines Aufenthaltsbereichs, wobei mittels eines Myonenteleskops darauf auftreffende Myonen als Myonenteleskop-Detektionsereignisse und deren Myonentrajektorien als Myonentrajektorien-Daten erfasst werden, wobei zudem mittels eines objektseitigen Myonendetektors darauf auftreffende Myonen als Myonendetektor-Detektionsereignisse erfasst werden, und wobei quasizeitgleiche Myonenteleskop-Detektionsereignisse und Myonendetektor-Detektionsereignisse ermittelt werden und basierend auf den zugehörigen Myonentrajektorien-Daten die Positionierung des Objekts charakterisiert wird.

  • Patent
    DE102019131006 - Erteilung 01.10.2020

Permalink: https://www.hzdr.de/publications/Publ-32997
Publ.-Id: 32997


P1915 - Magnetische Streufeld-Struktur, magnonisches Bauelement und Verfahren zur Herstellung einer magnetischen Streufeldstruktur

Samad, F.; Koch, L.; Arekapudi, S. S. P. K.; Hellwig, O.; Schultheiß, H.

Eine magnetische Struktur (510) weist einen synthetischen antiferromagnetischen Schichtstapel (100) mit senkrechter magnetischer Anisotropie auf. Ein erster und ein zweiter Teilbereich (110, 120) des synthetischen antiferromagnetischen Schichtstapels (100) sind lateral nebeneinander ausgebildet. Eine vertikaler erster Magnetisierungsverlauf im ersten Teilbereich (110) unterscheidet sich nach Betrag und/oder Orientierung von einem vertikalen zweiten Magnetisierungsverlauf im zweiten Teilbereich (120). Auf einer horizontalen Hauptoberfläche (101) des synthetischen antiferromagnetischen Schichtstapels (100) kann eine Entkopplungsschicht (200) ausgebildet sein. Auf der Entkopplungsschicht (200) oder der Hauptoberfläche (101) ist eine Funktionsschicht (300) ausgebildet. Die Funktionsschicht (300) wird lokal durch Kopplung mit dem synthetischen antiferromagnetischen Schichtstapel (100)oder durch die Streufelder des synthetischen antiferromagnetischen Schichtstapels (100)in ihrer Magnetisierung ausgerichtet, wodurch in der Funktionsschicht (300) beispielsweise eine variable und reprogrammierbare Infrastruktur für die Erzeugung, Verarbeitung, Übertragung und Detektion von Spinwellen erzeugt werden kann.

  • Patent
    DE102019129203 - Offenlegung 29.04.2021

Permalink: https://www.hzdr.de/publications/Publ-32996
Publ.-Id: 32996


P1909 - Mehrphasen-Messsystem mit Kalibrierwertnachführung und strömungstechnische Anordnung

Wiedemann, P.; Flaisz, A.; Schleicher, E.

Ein Mehrphasen-Messsystem (100) für ein mehrphasiges Fluid (205) weist eine Referenzwert-Messanordnung (160) und eine Mehrphasen-Messeinrichtung (130) auf. Die Referenzwert-Messanordnung (160) weist mindestens eine Kapillare (110) und eine Kapillaren- Messeinrichtung (120) auf. Innere Querschnittsfläche und Länge der Kapillare (110) sind so bemessen, dass bei Durchströmung der Kapillare (110) Phasen des mehrphasigen Fluids (205) in Durchströmungsrichtung separieren. Die Kapillaren-Messeinrichtung (120) ist zur Bestimmung mindestens einer physikalischen Eigenschaft mindestens einer der durch die Kapillare (110) fließenden Phasen eingerichtet. Das Mehrphasen-Messeinrichtung (130) ist für eine Messung
eines Volumen- und/oder Massenanteils von mindestens einer Phase des mehrphasigen Fluids und/oder für eine Messung eines Volumen- und/oder Massenstromes von mindestens einer der Phasen des mehrphasigen Fluids unter Berücksichtigung der durch die Kapillaren-Messeinrichtung (120) bestimmten physikalischen Eigenschaft(en) eingerichtet.

  • Patent
    DE102019125243 - Offenlegung 25.03.2021; Nachanmeldungen: WO

Permalink: https://www.hzdr.de/publications/Publ-32995
Publ.-Id: 32995


P1908 - Verfahren zum Herstellen eines gedruckten magnetischen Funktionselements und gedrucktes magnetisches Funktionselement

Canon Bermudez, G. S.; Mönch, J. I.; Makarov, D.

Die vorliegende Erfindung betrifft ein Verfahren zum Herstellen eines gedruckten magnetischen Funktionselements, bei dem ein Substrat (1) auf einer Oberfläche mit mindestens einem Kontakt (2) aus einem elektrisch leitfähigen Werkstoff versehen wird. Nachfolgend wird auf den oder an den mindestens einen Kontakt (2) und diesen unmittelbar berührend eine Struktur (3) aus einem einen magnetoresistiven Effekt aufweisenden Werkstoff als Paste, als Gel, als Dispersion oder als Suspension aufgedruckt sowie die Struktur (3) durch eine Bestrahlung mit elektromagnetischer Strahlung über einen Zeitraum im Millisekundenbereich elektrisch leitfähig und magnetfeldempfindlich.

  • Patent
    DE102019211970 - Offenlegung 11.02.2021; Nachanmeldungen: WO

Permalink: https://www.hzdr.de/publications/Publ-32994
Publ.-Id: 32994


P1907 - Deuterierte 7-(3-(4-(2-([18F]Fluor)ethoxy)phenyl)propyl)-2-(furan-2-yl)-7H-pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidin-5-amin-Derivate

Lai, T. H.; Teodoro, R.; Toussaint, M.; Gündel, D.; Deuther-Conrad, W.; Dukic-Stefanovic, S.; Schröder, S.; Moldovan, R.-P.; Brust, P.

Die Erfindung betrifft eine Verbindung der allgemeinen Formel I worin die Reste X1a, X1b, X2a, X2b, X3a, X3b, X4a, X4b, X5a und X5b unabhängig voneinander jeweils Wasserstoff oder Deuterium sind, mit der Maßgabe, dass zumindest einer der Reste X1a, X1b, X2a, X2b, X3a, X3b, X4a, X4b, X5a und X5b Deuterium ist.

  • Patent
    DE102019116986 - Offenlegung 24.12.2020; Nachanmeldungen: WO

Permalink: https://www.hzdr.de/publications/Publ-32993
Publ.-Id: 32993


P1906 - 3-(4-Amino-2-methoxyphenyl)-2-cyanoacrylsäure-Derivate und deren Verwendung als Präkursoren für die Herstellung radiochemischer Verbindungen

Moldovan, R.-P.; Sadeghzadeh, M.; Wenzel, B.; Kranz, M.; Teodoro, R.; Ludwig, F.-A.; Fischer, S.; Toussaint, M.; Deuther-Conrad, W.; Brust, P.

Die Erfindung betrifft eine Verbindung der allgemeinen Formel (E)-I oder (Z)-I worin Y eine Hydroxygruppe oder eine O-M+-Gruppe ist, wobei M+ ein Kation ist; Z1 aus der Gruppe ausgewählt ist, die aus einer substituierten oder unsubstituierten C1-C12-Alkylgruppe, einer substituierten oder unsubstituierten C2-C12-Alkenylgruppe, einer substituierten oder unsubstituierten C2-C12-Alkinylgruppe, einer substituierten oder unsubstituierten Arylgruppe, einer substituierten oder unsubstituierten Heteroarylgruppe, einer substituierten oder unsubstituierten Alkylarylgruppe, einer substituierten oder unsubstituierten Arylalkylgruppe und einer Gruppe -A1-X besteht, worin A1 eine Kohlenwasserstoffkette mit ein bis vier substituierten oder unsubstituierten Methylengruppen ist, wobei in der Kohlenwasserstoffkette zumindest ein Sauerstoffatom unter Ausbildung einer Ethergruppe angeordnet sein kann, und X aus der Gruppe ausgewählt ist, die aus einer Methylgruppe, einem Halogen und einer Hydroxygruppe besteht; und Z2 ein Rest ist, der eine Abgangsgruppe AG trägt, wobei Z2 aus der Gruppe ausgewählt ist, die aus einer substituierten oder unsubstituierten C1-C12-Alkylgruppe, einer substituierten oder unsubstituierten C2-C12-Alkenylgruppe, einer substituierten oder unsubstituierten C2-C12-Alkinylgruppe, einer substituierten oder unsubstituierten Arylgruppe, einer substituierten oder unsubstituierten Heteroarylgruppe, einer substituierten oder unsubstituierten Alkylarylgruppe und einer substituierten...

  • Patent
    DE102019112040 - Offenlegung 12.11.2020; Nachanmeldungen: WO

Permalink: https://www.hzdr.de/publications/Publ-32992
Publ.-Id: 32992


P1905 - N-(4-methoxy-7-morpholinobenzo[d]thiazol-2-yl)-acetamid-Derivate und deren Verwendung

Lai, T. H.; Teodoro, R.; Moldovan, R.-P.; Kranz, M.; Dukic-Stefanovic, S.; Toussaint, M.; Spalholz, T.; Deuther-Conrad, W.; Brust, P.

Die Erfindung betrifft eine Verbindung der allgemeinen Formel I (Formel I)
worin Ar eine Phenylgruppe oder eine Pyridylgruppe ist; R1 Wasserstoff oder eine Nitrogruppe ist; und R2 Fluor oder eine Abgangsgruppe ist, wobei die Abgangsgruppe aus der Gruppe ausgewählt ist, die aus einer Nitrogruppe, einem Halogen, einem Diazoniumion oder -salz, einem Trialkylammoniumion oder -salz, einem Dialkoxyaren, einem Sulfoxid, einer Boronsäure, einem Boronsäureester, Alkylzinn, Arylzinn, einem Iodoniumion oder -salz, einem Iodonium-Ylid und einem Sulfonsäureester besteht.

  • Patent
    DE102019110904 - Offenlegung 29.10.2020

Permalink: https://www.hzdr.de/publications/Publ-32991
Publ.-Id: 32991


P1904 - Verwendung eines Komplexierungsmittels zur Rückgewinnung von Metallionen aus Industrieabwasser sowie ein Verfahren dazu

Jain, R.; Joshi, T.; Pollmann, K.

Die vorliegende Erfindung betrifft ein neues Komplexierungsmittel zur Rückgewinnung von Metallionen aus Industrieabwasser, aufweisend ein Trägermaterial, an dem Siderophore über einen Linker kovalent immobilisiert sind, wobei der Linker eine Polyethylenglykol-Kette enthält, und wobei der Linker eine Masse von 2000-3500 Da aufweist, sowie ein Verfahren zu dessen Herstellung und die Verwendung des Komplexierungsmittels bei der Rückgewinnung von Metallen aus Industrieabwässern.

  • Patent
    DE102019108803 - Offenlegung 08.10.2020; Nachanmeldungen: WO

Permalink: https://www.hzdr.de/publications/Publ-32990
Publ.-Id: 32990


P1903 - Anordnung zur berührungslosen Bestimmung der Geschwindigkeitsverteilung eines Schmelzvolumens in einer Stranggusskokille

Ratajczak, M.; Wondrak, T.; Stefani, F.; Primetals Austria

Die Erfindung betrifft eine Anordnung zur berührungslosen Bestimmung einer Geschwindigkeitsverteilung eines Schmelzvolumens in einer Stranggusskokille. Die erfindungsgemäße Anordnung soll eine Messung mit verbesserten Signal-Rausch-Verhältnis ermöglichen und in bestehende Bauteile integriert werden. Die Anordnung weist mindestens eine ein primäres Magnetfeld erzeugende Spule, deren primäres Magnetfeld das Schmelzvolumen durchdringt, und eine Mehrzahl von Magnetfeldsensoren zur Messung des durch die Wechselwirkung der Schmelzbewegung mit dem erzeugten primären Magnetfeld induzierten Magnetfeldes auf. Die Stranggusskokille weist mindestens ein Kokillenelement auf, welches in mindestens einem Bereich mit einem Anschlusselement verbunden ist. Spule und Magnetfeldsensoren sind derart innerhalb des Anschlusselements angeordnet, dass die Magnetfeldsensoren innerhalb des von der Spule umschlossenen Volumens des Anschlusselements angeordnet sind.

  • Patent
    DE102019105628 - Erteilung 19.03.2020; Nachanmeldungen: WO

Permalink: https://www.hzdr.de/publications/Publ-32989
Publ.-Id: 32989


Data publication: Stretchable Thin Film Mechanical Strain Gated Switches and Logic Gate Functions Based on a Soft Tunneling Barrier

Chae, S.; Jin Choi, W.; Fotev, I.; Bittrich, E.; Uhlmann, P.; Schubert, M.; Makarov, D.; Wagner, J.; Pashkin, O.; Fery, A.

Time-domain THz spectroscopy (raw data) and the analysis of the delay time (Origin file)

Keywords: Strain gated electric switch; logic gates; tunneling; stretchable circuit; thin film

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Permalink: https://www.hzdr.de/publications/Publ-32988
Publ.-Id: 32988


Magnetostructural Phase Transition in Fe₆₀V₄₀ Alloy Thin Films

Anwar, M. S.; Cansever, H.; Böhm, B.; Gallardo, R.; Hübner, R.; Kentsch, U.; Zhou, S.; Eggert, B.; Wende, H.; Potzger, K.; Faßbender, J.; Lenz, K.; Lindner, J.; Hellwig, O.; Bali, R.

The tuning and control over the intrinsic magnetic properties, such as saturation magnetization (Ms) and Gilbert damping (α), can be obtained via systematic rearrangement of the lattice at the nanoscale. In certain binary alloys such as B2 Fe60Al40 [1] and B2 Fe50Rh50 [2], the Ms can be tuned by inducing chemical disorder. The disorder caused by the randomization of site occupancies of the atoms can be achieved by ion-irradiation. Here we explore a magnetic phase transition in Fe60V40 thin films caused by ordering of the lattice structure from short-range order to the crystalline state.
Fe60V40 films (~ 40 nm) were grown onto SiO2/Si substrate. The as-grown films are weakly ferromagnetic with low Ms of 17 kA/m; whereas irradiation with 25 keV Ne+-ions at fluences of ~ 5 × 1015 ions/cm2 leads to a drastic increase of Ms to ~ 750 kA/m, as shown in Fig. 1. X-ray diffraction as well as transmission electron microscopy reveal a structural short-range order in the as-grown films, that transform to A2 Fe60V40 with increasing Ne+-fluence. The A2 region appears to nucleate at the film top surface and with increasing fluence, it propagates deeper down into the film. The effect of the phase transition on the dynamic behaviour has been investigated using ferromagnetic resonance (Fig. 2). The low value of Gilbert damping (~ 0.002) has been obtained from the frequency dependence of the resonance spectra. Furthermore, the transition can be tracked using Conversion electron Mössbauer spectroscopy to shed light on the variation of local magnetic ordering during the transition. The tunable film structure as well as low damping form the basis for further investigations on nanomagnets embedded within Fe60V40 thin films.

Funding by the DFG - 322462997 (BA 5656/1-2 | WE 2623/14-2) is acknowledged. Ion-irradiation was performed at the Ion Beam Centre of the HZDR.

References
[1] J. Ehrler, et al., New J. Phys., 22, 073004 (2020).
[2] B. Eggert, et al., RSC Adv.,10, 14386 (2020).

Keywords: Phase transition; Ferromagnetism; Ion-irradiation

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    Joint MMM-INTERMAG, 10.-14.01.2022, New Orleans, United States
  • Lecture (Conference) (Online presentation)
    The 2021 Around-the-Clock Around-the-Globe Magnetics Conference, 21.08.2021, Online, Online
  • Lecture (Conference) (Online presentation)
    6th International Virtual Conference on Nanostructuring by Ion Beams (ICNIB 2021), 05.-08.10.2021, Bhubaneswar, India
  • Poster (Online presentation)
    DPG 2021 - 84. Jahrestagung der DPG und DPG-Tagung der Sektion Kondensierte Materie (SKM), 27.09.-01.10.2021, online, Germany
  • Lecture (others)
    Joint EuFN and FIT4NANO workshop, 27.-30.09.2021, TU Wien, Austria
  • Poster (Online presentation)
    736. WE-Heraeus-Seminar, 05.-08.01.2021, online, Germany
  • Poster
    22nd International Conference on Ion Beam Modification of Materials (IBMM 2022), 10.-15.07.2022, Lisbon, Portugal
  • Lecture (Conference)
    DPG (Spring) Meetings 2022, 04.-09.09.2022, Regensburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-32987
Publ.-Id: 32987


P1902 - Verfahren und Vorrichtung zur Abtrennung von Kunststoffpartikeln

Nikpay, M.

Die Erfindung betrifft eine Verfahren zur Abtrennung von Kunststoffpartikeln aus einer Flüssigkeit oder einem heterogenen Gemisch, das eine Flüssigkeit enthält oder mit einer Flüssigkeit in Kontakt gebracht wird. Dabei ist vorgesehen, dass (a) die Kunststoffpartikel einem Magnetfeld ausgesetzt werden; (b) an der Oberfläche eines Sammlers Kunststoffpartikel adsorbiert werden; und (c) an der Oberfläche des Sammlers adsorbierte Kunststoffpartikel abgeführt werden.

  • Patent
    DE102019103936 - Offenlegung 20.08.2020

Permalink: https://www.hzdr.de/publications/Publ-32986
Publ.-Id: 32986


P1901 - Durchflussmessanordnung und strömungstechnische Anordnung

Arlit, M.; Hampel, U.; Schroth, C.

Eine Durchflussmessanordnung (400) weist einen Messkanal (100) mit einem Messkanaldurchmesser (D0) auf. In dem Messkanal (100) sind ein Strömungsteiler (300) und ein Anemometrie-Gittersensor (500) angeordnet. Der Anemometrie-Gittersensor (500) weist eine Vielzahl von Sensorelementen (510) mit temperaturabhängigem elektrischen Widerstand auf, die lateral voneinander beabstandet sind. Der Strömungsteiler (300) weist eine Vielzahl von Teilkanälen (310) auf. Eine Kanallänge (L1) der Teilkanäle (310) kann kleiner oder gleich dem Messkanaldurchmesser (D0) sein. Ein Abstand (L2) zwischen dem Anemometrie-Gittersensor (500) und dem Strömungsteiler (300) kann kleiner oder gleich dem Messkanaldurchmesser (D0) sein.

  • Patent
    DE102019103674 - Offenlegung 13.08.2020; Nachanmeldungen: WO, EP

Permalink: https://www.hzdr.de/publications/Publ-32985
Publ.-Id: 32985


P1827 - Microfluidic device, apparatus and method for enrichment and dilution of magnetic molecular entities

Mutschke, G.; Yang, X.; AGH Krakau

A microfluidic device (500) includes a substrate (100) with a fluid channel (250) extending from an inlet opening (210) to a channel branch (270). The fluid channel (250) includes a planar spiral portion (255) and at the channel branch (270) 10 the fluid channel (250) branches in at least two outlet channels (280). A ferromagnetic auxiliary structure (300) is formed in a plane parallel to the planar spiral portion (255).

  • Patent
    EP3669982 - Offenlegung 24.06.2020

Permalink: https://www.hzdr.de/publications/Publ-32984
Publ.-Id: 32984


Comparing Metaflow, MLFlow and DVC

Sultova, N.

Blogpost with additional material covering the comparison of Metaflow, MLFlow and DVC for potential usage at HelmholtzAI.

Keywords: machine learning; mlops; devops; python; version management

Permalink: https://www.hzdr.de/publications/Publ-32983
Publ.-Id: 32983


Data publication: A new system for real-time data acquisition and pulse parameterization for digital positron annihilation lifetime spectrometers with high repetition rates

Hirschmann, E.; Butterling, M.; Hernandez Acosta, U.; Liedke, M. O.; Elsherif, A. G. A.; Petring, P.; Görler, M.; Krause-Rehberg, R.; Wagner, A.

Bei diesem Datensatz handelt es sich um die Bilder zur Publikation und Daten für die Leistungskurven

Keywords: Data reduction methods; Digital signal processing (DSP); Detection of defects; Online farms and online filtering

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Permalink: https://www.hzdr.de/publications/Publ-32980
Publ.-Id: 32980


A new system for real-time data acquisition and pulse parameterization for digital positron annihilation lifetime spectrometers with high repetition rates

Hirschmann, E.; Butterling, M.; Hernandez Acosta, U.; Liedke, M. O.; Elsherif, A. G. A.; Petring, P.; Görler, M.; Krause-Rehberg, R.; Wagner, A.

We present a new system for high repetition rate and real-time pulse analysis imple- mented at the Monoenergetic Positron Source (MePS) at the superconducting electron LINAC ELBE at Helmholtz-Zentrum Dresden-Rossendorf. Dedicated digital signal processing and op- timized algorithms are employed allowing for high bandwidth throughput, online pulse analysis and filtering. Positrons generated from radioisotopes and from bremsstrahlung pair production by means of highly intense accelerator-based positron beams serve as a microstructure probe allowing material characterizations with respect to chemical, mechanical, electrical, and magnetic properties. Positron annihilation lifetime events with up to 13 MHz repetition rate are being processed online without losses while performing signal selections for pile-up reduction, online energy calibration, and - for radioisotope-based measurements - identification of start and stop events.

Keywords: Data reduction methods; Digital signal processing (DSP); Detection of defects; Online farms and online filtering

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Permalink: https://www.hzdr.de/publications/Publ-32979
Publ.-Id: 32979


Numerical dimensioning of a pre-cooler for sCO2 power cycles to utilize industrial waste heat

Unger, S.

These are the the processed data of the paper "Numerical dimensioning of a pre-cooler for sCO2 power cycles to utilize industrial waste heat". The data contain the heat transfer and fluid dynamic values of the simulation performed for the corresponding article.

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Permalink: https://www.hzdr.de/publications/Publ-32978
Publ.-Id: 32978


Transport properties of systematically disordered Cr2AlC films

Salgado Cabaco, J.; Kentsch, U.; Lindner, J.; Faßbender, J.; Leyens, C.; Bali, R.; Boucher, R.

Nano-lamellar composite materials, known as MAX-phases, can possess a combination of ceramic and metallic properties. A prototype compound is Cr2AlC, formed from a unit cell of Cr2C sandwiched between atomic planes of Al, thereby imparting a good electrical conductivity, as well as mechanical stability, radiation and oxidation resistance [1, 2]. These properties rely on the lamellar structure of the compound, and systematic introduction of defects, such as displacing or doping atoms within the layers, has the potential to tune electron transport and modify magnetic properties [3]. An ideal tool for defect implantation is ion-irradiation, available both in the form of a broad-beam for wafer-scale processing as well as focused ion-beams for device prototyping. Here we observe the modifications to the structural, transport and magnetic behavior of 500 nm thick Cr2AlC after irradiation with Co+ ions, and Ar+ noble gas ions as control. The films were irradiated with 450 keV of Co+ ions at fluences varying from 5E12 to 5E15 ions.cm-2, and the control samples with 400 keV Ar+ ions keeping the sample fluences. Structural analysis using XRD shows that ion-irradiation induces a suppression of the 0002 reflection, indicating a gradual decay of the nano-lamellar structure. Increasing ion-fluence also leads to an increase of the saturation magnetization at 1.5 K, whereby both Ar+ and Co+ cause an increased magnetization, respectively to 150 and 190 kA.m-1, for the highest fluences used. Large variations of the transport properties are observed. Magnetoresistance (MR) in the non-irradiated sample shows a classical B2 dependency, even up to high temperatures. At Co+ fluences of 5E13 ions.cm-2 the MR shows a two orders of magnitude increase, up to 3% (10 T) at 100 K. A similar effect also occurs for 5E12 ions.cm-2 Ar+ irradiated films, however with a smaller MR-increase. It appears that resistivity increases and the residual resistance ratio reduces with increasing fluence due to the introduction of disorder. These results show that ion irradiation induces significant changes in the transport properties of MAX phase materials, that will be further investigated. The systematic disordering of nano-laminated MAX phase films may therefore reveal interesting disorder and spin-related transport phenomena.

Funding by the Deutsche Forschungsgemeinschaft (DFG) - Project number 456078299 is acknowledged. Ion-irradiation has been performed at the Ion Beam Centre of the HZDR.
[1] A. S. Ingason, M. Dahlqvist, J. Rosen, Magnetic MAX phases from theory and experiments; a review; J. Phys.: Condens. Matter 28, 433003, (2016). [2] M. W. Barsoum, MAX Phases: Properties of Machinable Ternary Carbides and Nitrides; Weinheim: Willey-VCH (2013). [3] C. Wang, T. Yang, C. L. Tracy, C. Lu, H. Zhang, Y.-J. Hu, L. Wang, L. Qi, L. Gu, Q. Huang, J.Zhang, J. Wang, J. Xue, R. C. Ewing, Y. Wang, Disorder in Mn+1AXn phases at the atomic scale, Nature Communications 10, 622 (2019).

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  • Poster (Online presentation)
    International workshop on functional MAX-materials. 2nd FunMax, 14.-17.09.2021, Krasnoyarsk, Russia

Permalink: https://www.hzdr.de/publications/Publ-32977
Publ.-Id: 32977


Targeting glutamine metabolism and autophagy: the combination for prostate cancer radiosensitization

Mukha, A.; Kahya, U.; Dubrovska, A.

Radiotherapy is one of the curative mainstays of prostate cancer; however, its efficacy is often diminished by tumor radioresistance. Depending on the stage of disease, tumors can relapse in approximately 50% of patients with prostate cancer after radiotherapy. Nevertheless, the mechanisms that drive tumor cell survival are not fully characterized, and reliable molecular prognostic markers of prostate cancer radioresistance are missing. Similar to other tumor entities, prostate cancer cells are heterogeneous in their capability to maintain tumor growth. The populations of cancer stem cells (CSC) with self-renewal and differentiation properties are responsible for tumor development and recurrence after treatment. Eradication of these CSC populations is of utmost importance for efficient tumor cure. In a recently published study, we showed that prostate cancer cells could be radiosensitized by glutamine deprivation, resulting in DNA damage, oxidative stress, epigenetic modifications, and depletion of CSCs. Conversely, prostate cancer cells with resistance to glutamine depletion show an activation of ATG-mediated macroautophagy/autophagy as a survival strategy to withstand radiation-induced damage. Thus, a combination of targeting glutamine metabolism and autophagy blockade lead to more efficient prostate cancer radiosensitization.

Keywords: ATG5; CSC; glutaminase; tricarboxylic acid cycle

Permalink: https://www.hzdr.de/publications/Publ-32974
Publ.-Id: 32974


Experimental characterization of liquid metal bubble-driven flows modeling the situation in a steel ladle

Wondrak, T.; Bruch, C.; Eckert, S.; Gardin, P.; Hackl, G.; Lachmund, H.; Lüngen, H. B.; Odenthal, H.-J.; Timmel, K.; Willers, B.

In metallurgy, gas-liquid two-phase flows are relevant for mixing, degassing and refinement. The reliable prediction of the hydrodynamic performance in gas-stirred ladles is of utmost relevance for optimization and process control. A new experimental facility has been designed and constructed for systematic investigations of gas bubbles rising inside the alloy SnBi, its thermophysical properties are very similar to those of steel. Low operating temperatures (T~200°C) allow the use of powerful measuring techniques. The cylindrical fluid vessel represents a 1:5.25 model of an industrial 185 t ladle and is equipped with a vacuum pump to achieve low-pressure conditions for VOD (Vacuum Oxygen Decarburization) applications as well. The experiments provide a copious data base about the flow regimes, void fraction, liquid and bubble velocities, and bubble properties, which can be used to provide so far unknown boundary conditions for CFD simulations of various metallurgical reactors such as steelmaking converters or steelmaking ladles.

Keywords: two-phase flow; liquid metal; bubble measurement

Permalink: https://www.hzdr.de/publications/Publ-32973
Publ.-Id: 32973


RawData for paper: Mounted Single Particle Characterization for 3D Mineralogical Analysis - MSPaCMAn

Da Assuncao Godinho, J. R.

Raw 3D images of the 3 types of samples used in the paper

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Permalink: https://www.hzdr.de/publications/Publ-32972
Publ.-Id: 32972


Manipulation of antiferromagnetism with electric fields: from fundamentals to memory concepts

Makarov, D.

Thin film antiferromagnets (AF) have potential to revolutionize spintronics due to their inherently magnetic-field stable magnetic order and high-frequency operation. To explore their application potential, it is necessary to understand modifications of the magnetic properties and magnetoelectric responses of AF thin films with respect to their bulk counterparts. Considering grainy morphology of thin films, questions regarding the change of the intergranular exchange, criticality behavior and switching of the order parameter need to be addressed.
Our approach is based on the electron transport characterization of magnetic responses of thin film antiferromagnets [1-4]. This task is difficult as minute uncompensated surface magnetization of antiferromagnets needs to be detected, which imposes strict requirements to the sensitivity of the method. We will outline our developments of zero-offset anomalous Hall magnetometry [1] applied to study the physics of conventional metallic IrMn and insulating magnetoelectric Cr2O3 antiferromagnets. To build a reliable description of the material properties, the analysis of the transport data is backed up by structural characterization and real space imaging of AF domain patterns using NV microscopy [2,5]. Based on this unique and novel combination, we for the first time observe the formation of nanoscale antiferromagnetic domains in thin films of Chromia (Cr2O3) across its ordering temperature at ~300 K. Our quantitative results yield a detailed understanding of the domain formation process in Cr2O3 and allow us to determine the efficiency of inter-granular magnetic exchange coupling [5]. This coupling strength has proven decisive in the decades long development of ferromagnetic memory media and will be of equal importance for future antiferromagnetic spintronics technologies.
The fundamental understanding of the magnetic microstructure of magnetoelectric α-Cr2O3 thin films and the possibility to read-out its antiferromagnetic order parameter all-electrically enabled the entirely new recording concept where a magnetoelectric memory cell can be addressed without using a ferromagnet. With this approach, we opened an appealing topic of purely antiferromagnetic magnetoelectric random access memory (AF-MERAM) [2].
By exploring the interaction of antiferromagnetic domain walls with morphological structures prepared on the surface of Cr2O3 single crystals, we access the nanoscale mechanics of AF domain walls [6,7]. We propose to employ nanoscale patterns as engineered pinning centers for AF domain walls, where binary information is encoded by the direction of the Neel vector. Our results bear significant potential for technological exploitation be it in the form of the proposed antiferromagnetic memory devices, or ultimately for the realisation of DW logic using antiferromagnets.
These recent developments on the fabrication and characterization of Cr2O3-based functional elements will be discussed in this presentation.

[1] T. Kosub, M. Kopte, F. Radu, O. G. Schmidt, D. Makarov, “All-Electric access to the Magnetic-Field-Invariant Magnetization of Antiferromagnets”, Phys. Rev. Lett. 115, 097201 (2015).
[2] T. Kosub, M. Kopte, R. Hühne, P. Appel, B. Shields, P. Maletinsky, R. Hübner, M. O. Liedke, J. Fassbender, O. G. Schmidt, and D. Makarov, “Purely antiferromagnetic magnetoelectric random access memory”, Nature Communications 8, 13985 (2017).
[3] R. Schlitz, T. Kosub, A. Thomas, S. Fabretti, K. Nielsch, D. Makarov, and S. T. B. Goennenwein, “Evolution of the spin hall magnetoresistance in Cr2O3/Pt bilayers close to the Neel temperature”, Appl. Phys. Lett. 112, 132401 (2018).
[4] P. Muduli, R. Schlitz, T. Kosub, R. Hübner, A. Erbe, D. Makarov, and S. T. B. Goennenwein, “Local and nonlocal spin Seebeck effect in lateral Pt-Cr2O3-Pt devices at low temperatures”, Appl. Phys. Lett. Materials 9, 021122 (2021).
[5] P. Appel, B. J. Shields, T. Kosub, R. Hübner, J. Fassbender, D. Makarov, and P. Maletinsky, “Nanomagnetism of magnetoelectric granular thin film antiferromagnets”, Nano Letters 19, 1682 (2019).
[6] O. V. Pylypovskyi, A. V. Tomilo, D. D. Sheka, J. Fassbender, and D. Makarov, “Boundary conditions for the Neel order parameter in a chiral antiferromagnetic slab”, Phys. Rev. B 103, 134413 (2021).
[7] N. Hedrich, K. Wagner, O. V. Pylypovskyi, B. J. Shields, T. Kosub, D. D. Sheka, D. Makarov, and P. Maletinsky, “Nanoscale mechanics of antiferromagnetic domain walls”, Nature Physics (2021). https://doi.org/10.1038/s41567-020-01157-0.

Keywords: antiferromagnetic spintronics; magnetoelectric effect

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  • Invited lecture (Conferences) (Online presentation)
    school in the frame of the COST Action MAGNETOFON – “Ultrafast opto-magneto-electronics for non-dissipative information technology” (https://magnetofon.science.ru.nl), 05.-08.10.2021, Samobor, Croatia

Permalink: https://www.hzdr.de/publications/Publ-32970
Publ.-Id: 32970


Curvilinear magnetism

Makarov, D.

Conventionally, tailoring of the Dzyaloshinskii-Moriya interaction (DMI) is done by optimizing materials, either doping a bulk single crystal or adjusting interface properties of thin films and multilayers. A viable alternative to the conventional material screening approach is to explore the interplay between the sample geometry and topology of the order parameter. The research field in magnetism, which is dealing with the study of the impact of geometrical curvature on magnetic responses of curved 1D wires and 2D shells is known as curvilinear magnetism [1-4]. The lack of the inversion symmetry and the emergence of a curvature induced effective anisotropy and DMI stemming from the exchange interaction [5,6] are characteristic of curved surfaces, leading to curvature-driven magnetochiral effects. Volkov et al. has proven that the exchange-driven chiral effects in curvilinear ferromagnets are experimental observables [7] and can be used to realize nanostructures with tunable magnetochiral properties from standard magnetic materials.
A counterpart of the intrinsic DMI for the case of curvilinear magnets is the mesoscale Dzyaloshinskii-Moriya interaction, which is a result of the interplay between the intrinsic (spin-orbit-driven) and extrinsic (curvature-driven) DMI terms [8]. The mesoscale DMI governs the magnetochiral properties of any curvilinear ferromagnetic nanosystem and depends both on the material and geometrical parameters. Its strength and orientation can be tailored by properly choosing the geometry, which allows stabilizing distinct magnetic chiral textures including skyrmion and skyrmionium states as well as skyrmion lattices [9-11]. Interestingly, skyrmion states can be formed in a material even without an intrinsic DMI [9,11]. Very recently, Sheka et al. discovered a novel non-local chiral symmetry breaking effect, which does not exist in planar thin film magnets: it is essentially non-local and manifests itself even in static spin textures living in curvilinear magnetic nanoshells [6].
The field of curvilinear magnetism was recently extended towards curvilinear antiferromagnets. Pylypovskyi et al. demonstrated that intrinsically achiral one-dimensional curvilinear antiferromagnet behaves as a chiral helimagnet with geometrically tunable DMI, orientation of the Neel vector and the helimagnetic phase transition [12,13]. This positions curvilinear antiferromagnets as a novel platform for the realization of geometrically tunable chiral antiferromagnets for antiferromagnetic spinorbitronics.
The application potential of 3D-shaped magnetic thin films is currently being explored as mechanically shapeable magnetic field sensors [14,15] for automotive applications, magnetoelectrics for memory devices, spin-wave filters, high-speed racetrack memory devices as well as on-skin interactive electronics [16-18].
The fundamentals as well as application relevant aspects of curvilinear ferro- and antiferromagnets will be covered in this presentation.

[1] D. Makarov et al., Adv. Mater. (2021). doi:10.1002/adma.202101758
[2] R. Streubel et al., J. Phys. D: Appl. Phys. 49 (2016), 363001.
[3] D. Sander et al., J. Phys. D: Appl. Phys. 50 (2017), 363001.
[4] E. Vedmedenko et al., J. Phys. D: Appl. Phys. 53 (2020), 453001.
[5] Y. Gaididei et al., Phys. Rev. Lett. 112 (2014), 257203.
[6] D. Sheka et al., Communications Physics 3 (2020), 128.
[7] O. Volkov et al., Phys. Rev. Lett. 123 (2019), 077201.
[8] O. Volkov et al., Scientific Reports 8 (2018), 866.
[9] V. Kravchuk et al., Phys. Rev. B 94 (2016), 144402.
[10] V. Kravchuk et al., Phys. Rev. Lett. 120 (2018), 067201.
[11] O. Pylypovskyi et al., Phys. Rev. Appl. 10 (2018), 064057.
[12] O. Pylypovskyi et al., Nano Letters 20 (2020), 8157.
[13] O. Pylypovskyi et al., Appl. Phys. Lett. 118 (2021), 182405.
[14] S. Canon Bermudez et al., Adv. Funct. Mater. (2021). doi:10.1002/adfm.202007788
[15] D. Makarov et al., Appl. Phys. Rev. 3 (2016), 011101.
[16] S. Canon Bermudez et al., Science Advances 4 (2018), eaao2623.
[17] S. Canon Bermudez et al., Nature Electronics 1 (2018), 589.
[18] J. Ge et al., Nature Communications 10 (2019), 4405.

Keywords: curvature effects in magnetism; flexible magnetic field sensors

Related publications

  • Lecture (others) (Online presentation)
    physics colloquium at the University of Nebraska-Lincoln, 18.11.2021, Lincoln, USA

Permalink: https://www.hzdr.de/publications/Publ-32969
Publ.-Id: 32969


Designing chiral magnetic responses by tailoring geometry of thin films: curvilinear ferro- and antiferromagnets

Makarov, D.

Conventionally, tailoring of the Dzyaloshinskii-Moriya interaction (DMI) is done by optimizing materials, either doping a bulk single crystal or adjusting interface properties of thin films and multilayers. A viable alternative to the conventional material screening approach can be the exploration of the interplay between the sample geometry and topology of the order parameter. The research field in magnetism, which is dealing with the study of the impact of geometrical curvature on magnetic responses of curved 1D wires and 2D shells is known as curvilinear magnetism [1-3]. The lack of the inversion symmetry and the emergence of a curvature induced effective anisotropy and DMI stemming from the exchange interaction [4,5] are characteristic of curved surfaces, leading to curvature-driven magnetochiral effects. Volkov et al. has proven that the exchange-driven chiral effects in curvilinear ferromagnets are experimental observables [6] and can be used to realize nanostructures with tunable magnetochiral properties from standard magnetic materials.
A counterpart of the intrinsic DMI for the case of curvilinear magnets is the mesoscale Dzyaloshinskii-Moriya interaction, which is a result of the interplay between the intrinsic (spin-orbit-driven) and extrinsic (curvature-driven) DMI terms [7]. The mesoscale DMI governs the magnetochiral properties of any curvilinear ferromagnetic nanosystem and depends both on the material and geometrical parameters. Its strength and orientation can be tailored by properly choosing the geometry, which allows stabilizing distinct magnetic chiral textures including skyrmion and skyrmionium states as well as skyrmion lattices [8-10]. Interestingly, skyrmion states can be formed in a material even without an intrinsic DMI [8,10]. Very recently, Sheka et al. discovered a novel non-local chiral symmetry breaking effect, which does not exist in planar thin film magnets: it is essentially non-local and manifests itself even in static spin textures living in curvilinear magnetic nanoshells [5].
The field of curvilinear magnetism was recently extended towards curvilinear antiferromagnets. Pylypovskyi et al. demonstrated that intrinsically achiral one-dimensional curvilinear antiferromagnet behaves as a chiral helimagnet with geometrically tunable DMI, orientation of the Neel vector and the helimagnetic phase transition [11,12]. This positions curvilinear antiferromagnets as a novel platform for the realization of geometrically tunable chiral antiferromagnets for antiferromagnetic spinorbitronics.

[1] R. Streubel et al., J. Phys. D: Appl. Phys. 49 (2016), 363001.
[2] D. Sander et al., J. Phys. D: Appl. Phys. 50 (2017), 363001.
[3] E. Vedmedenko et al., J. Phys. D: Appl. Phys. 53 (2020), 453001.
[4] Y. Gaididei et al., Phys. Rev. Lett. 112 (2014), 257203.
[5] D. Sheka et al., Communications Physics 3 (2020), 128.
[6] O. Volkov et al., Phys. Rev. Lett. 123 (2019), 077201.
[7] O. Volkov et al., Scientific Reports 8 (2018), 866.
[8] V. Kravchuk et al., Phys. Rev. B 94 (2016), 144402.
[9] V. Kravchuk et al., Phys. Rev. Lett. 120 (2018), 067201.
[10] O. Pylypovskyi et al., Phys. Rev. Appl. 10 (2018), 064057.
[11] O. Pylypovskyi et al., Nano Letters 20 (2020), 8157.
[12] O. Pylypovskyi et al., Appl. Phys. Lett. 118 (2021), 182405.

Keywords: flexible magnetic field sensors; curvilinear magnetism

Related publications

  • Invited lecture (Conferences) (Online presentation)
    IEEE Trends in Magnetism, 06.-10.09.2021, Palermo, Italy

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Publ.-Id: 32968


Nanomagnetism and spintronics of Cr2O3 magnetoelectric antiferromagnets

Makarov, D.

Thin film antiferromagnets (AF) have potential to revolutionize spintronics due to their inherently magnetic-field stable magnetic order and high-frequency operation. To explore their application potential, it is necessary to understand modifications of the magnetic properties and magnetoelectric responses of AF thin films with respect to their bulk counterparts. Considering grainy morphology of thin films, questions regarding the change of the intergranular exchange, criticality behavior and switching of the order parameter need to be addressed.
Our approach is based on the electron transport characterization of magnetic responses of thin film antiferromagnets [1-4]. This task is difficult as minute uncompensated surface magnetization of antiferromagnets needs to be detected, which imposes strict requirements to the sensitivity of the method. We will outline our developments of zero-offset anomalous Hall magnetometry [1] applied to study the physics of conventional metallic IrMn and insulating magnetoelectric Cr2O3 antiferromagnets. To build a reliable description of the material properties, the analysis of the transport data is backed up by structural characterization and real space imaging of AF domain patterns using NV microscopy [2,5]. Based on this unique and novel combination, we for the first time observe the formation of nanoscale antiferromagnetic domains in thin films of Chromia (Cr2O3) across its ordering temperature at ~300 K. Our quantitative results yield a detailed understanding of the domain formation process in Cr2O3 and allow us to determine the efficiency of inter-granular magnetic exchange coupling [5]. This coupling strength has proven decisive in the decades long development of ferromagnetic memory media and will be of equal importance for future antiferromagnetic spintronics technologies, for which we here present a powerful new development tool.
The fundamental understanding of the magnetic microstructure of magnetoelectric α-Cr2O3 thin films and the possibility to read-out its antiferromagnetic order parameter all-electrically enabled the entirely new recording concept where a magnetoelectric memory cell can be addressed without using a ferromagnet. With this approach, we opened an appealing topic of purely antiferromagnetic magnetoelectric random access memory (AF-MERAM) [2].
By exploring the interaction of antiferrmagnetic domain walls with morphological structures prepared on the surface of Cr2O3 single crystals, we access the nanoscale mechanics of AF domain walls. We propose to employ nanoscale patterns as engineered pinning centers for AF domain walls,
where binary information is encoded by the direction of the Neel vector. Our results bear significant potential for technological exploitation be it in the form of the proposed antiferromagnetic memory devices, or ultimately for the realisation of DW logic using antiferromagnets.
These recent developments on the fabrication and characterization of Cr2O3-based functional elements will be discussed in this presentation.
REFERENCES
[1] T. Kosub, M. Kopte, F. Radu, O. G. Schmidt, D. Makarov, “All-Electric access to the Magnetic-Field-Invariant Magnetization of Antiferromagnets”, Phys. Rev. Lett. 115, 097201 (2015).
[2] T. Kosub, M. Kopte, R. Hühne, P. Appel, B. Shields, P. Maletinsky, R. Hübner, M. O. Liedke, J. Fassbender, O. G. Schmidt, and D. Makarov, “Purely antiferromagnetic magnetoelectric random access memory”, Nature Communications 8, 13985 (2017).
[3] R. Schlitz, T. Kosub, A. Thomas, S. Fabretti, K. Nielsch, D. Makarov, and S. T. B. Goennenwein, “Evolution of the spin hall magnetoresistance in Cr2O3/Pt bilayers close to the Neel temperature”, Appl. Phys. Lett. 112, 132401 (2018).
[4] P. Muduli, R. Schlitz, T. Kosub, R. Hübner, A. Erbe, D. Makarov, and S. T. B. Goennenwein, “Local and nonlocal spin Seebeck effect in lateral Pt-Cr2O3-Pt devices at low temperatures”, Appl. Phys. Lett. Materials 9, 021122 (2021).
[5] P. Appel, B. J. Shields, T. Kosub, R. Hübner, J. Fassbender, D. Makarov, and P. Maletinsky, “Nanomagnetism of magnetoelectric granular thin film antiferromagnets”, Nano Letters 19, 1682 (2019).
[6] O. V. Pylypovskyi, A. V. Tomilo, D. D. Sheka, J. Fassbender, and D. Makarov, “Boundary conditions for the Neel order parameter in a chiral antiferromagnetic slab”, Phys. Rev. B 103, 134413 (2021).
[7] N. Hedrich, K. Wagner, O. V. Pylypovskyi, B. J. Shields, T. Kosub, D. D. Sheka, D. Makarov, and P. Maletinsky, “Nanoscale mechanics of antiferromagnetic domain walls”, Nature Physics (2021). https://doi.org/10.1038/s41567-020-01157-0.

Keywords: antiferromagnetic spintronics

Related publications

  • Invited lecture (Conferences) (Online presentation)
    2021 IEEE 11th International Conference on "Nanomaterials: Applications & Properties", 05.-11.09.2021, Odesa, Ukraine

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Publ.-Id: 32967


Ecological consequences of large herbivore exclusion in an African savanna: 12 years of data from the UHURU experiment

Alston, J.; Reed, C. G.; Khasoha, L. M.; Brown, B. R. P.; Busienei, G.; Carlson, N.; Coverdale, T. C.; Dudenhoeffer, M.; Dyck, M. A.; Ekeno, J.; Hassan, A. A.; Hohbein, R.; Jakopak, R. P.; Kimiti, B.; Kurukura, S.; Lokeny, P.; Louthan, A. M.; Musila, S.; Musili, P. M.; Tindall, T.; Weiner, S.; Kartzinel, T. R.; Palmer, T. M.; Pringle, R. M.; Goheen, J. R.

Diverse communities of large mammalian herbivores (LMH), once widespread, are now rare. LMH exert strong direct and indirect effects on community structure and ecosystem functions, and measuring these effects is important for testing ecological theory and for understanding past, current, and future environmental change. This in turn requires long-term experimental manipulations, owing to the slow and often nonlinear responses of populations and assemblages to LMH removal. Moreover, the effects of particular species or body-size classes within diverse LMH guilds are difficult to pinpoint, and the magnitude and even direction of these effects often depends on environmental context. Since 2008, we have maintained the Ungulate Herbivory Under Rainfall Uncertainty (UHURU) experiment, a series of size-selective LMH exclosures replicated across a rainfall/productivity gradient in a semi-arid Kenyan savanna. The goals of the UHURU experiment are to measure the effects of removing successively smaller size classes of LMH (mimicking the process of size-biased extirpation) and to establish how these effects are shaped by spatial and temporal variation in rainfall. The UHURU experiment comprises three LMH-exclusion treatments and an unfenced control, applied to 9 randomized blocks of contiguous 1 ha plots (n = 36). The fenced treatments are: “MEGA” (exclusion of megaherbivores, elephant and giraffe); “MESO” (exclusion of herbivores ≥40 kg); and “TOTAL” (exclusion of herbivores ≥5 kg). Each block is replicated three times at three sites across the 20 km rainfall gradient, which has fluctuated over the course of the experiment. The first five years of data were published previously (Ecological Archives E095-064) and have been used in numerous studies. Since publication of this original data paper, we have (a) continued to collect data according to the original protocols, (b) improved the taxonomic resolution and accuracy of plant and small-mammal identifications, and (c) begun collecting several new data sets. Here, we present updated and extended raw data from the first 12 years of the UHURU experiment (2008–2019). Data include daily rainfall data throughout the experiment; annual surveys of understory plant communities; annual censuses of woody-plant communities; annual measurements of individually tagged woody plants; monthly monitoring of flowering and fruiting phenology; every-other-month small-mammal mark-recapture data; and quarterly large-mammal dung surveys.

Keywords: climate change; dik-dik (Madoqua); East African savannas; elephant (Loxodonta africana); extinction; food webs; grazing and browsing herbivores; impala (Aepyceros melampus); long-term ecological field experiments; rangeland ecology

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Publ.-Id: 32965


Complexation of Np(V) with the dicarboxylates malonate and succinate: complex stoichiometry, thermodynamic data and structural information

Maiwald, M. M.; Müller, K.; Heim, K.; Rothe, J.; Dardenne, K.; Roßberg, A.; Koke, C.; Trumm, M.; Skerencak-Frech, A.; Panak, P. J.

The complexation of Np(V) with malonate and succinate is studied by different spectroscopic techniques, namely attenuated total reflection FT-IR (ATR FT-IR) and extended X-ray absorption fine structure (EXAFS) spectroscopy, as well as by quantum chemistry to determine the speciation, thermodynamic data and structural information of the formed complexes. For complex stoichiometries and thermodynamic functions (log beta0n(T), Delta rH0n, Delta rS0n) near infrared absorption spectroscopy (Vis/NIR) is applied. The complexation reactions are investigated as a function of the total ligand concentration ([Mal2-]total, [Succ2-]total), ionic strength (Im = 0.5 – 4.0 mol kg-1 Na+(Cl-/ClO4-)) and temperature (T = 20 – 85 °C). Besides the solvated NpO2+ ion, the formation of two Np(V) species with the stoichiometry NpO2(L)n1-2n (n = 1, 2, L = Mal2-, Succ2-) is observed. With increasing temperature the molar fractions of both complex species increase and the application of the law of mass action yields the temperature dependent conditional stability constants log beta`n(T) at given ionic strengths. The log beta`n(T) are extrapolated to IUPAC reference state conditions (Im = 0) according to the specific ion interaction theory (SIT) revealing thermodynamic log 0n(T) values. For all formed complexes (NpO2(Mal)-: log 01(25 °C) = 3.36 ± 0.11, NpO2(Mal)23-: log 02(25 °C) = 3.95 ± 0.19, NpO2(Succ)-: log 01(25 °C) = 2.05 ± 0.45, NpO2(Succ)23-: log 02(25 °C) = 0.75 ± 1.22) the stability constants increase with increasing temperature confirming an endothermic complexation reaction. The temperature dependence of the thermodynamic stability constants is described by the integrated Van’t Hoff equation yielding the standard reaction enthalpies and entropies for the complexation reactions. In addition, the sum of the specific binary ion-ion interaction coefficients 0n(T) for the complexation reactions are obtained from SIT modelling as a function of the temperature.
The structure of the complexes and the coordination mode of malonate and succinate are investigated using EXAFS spectroscopy, ATR-FT-IR spectroscopy and quantum chemical calculations. The results show, that in case of malonate 6-membered chelate complexes are formed, whereas the formation of 7-membered rings with succinate is energetically unfavourable in the equatorial plane of the Np(V) ion (as NpO2+ cation).

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A contribution to wettability and wetting characterisation of ultrafine particles with varying shape and degree of hydrophobization

Sygusch, J.; Rudolph, M.

Many particle separation processes are based on differences in wettabilities. Therefore, one needs to understand the interfacial properties and micro processes taking place on the material surface. The main quantity to account for wettability is the Young contact angle. However, this method requiring homogeneous flat and smooth sub-strates has drawbacks when analysing particles and is rather system specific as particles are not planar and exhibit rough surfaces. Here, we demonstrate the challenges of proper wettability analysis of particulate material as available methods are influenced strongly by multiple particle properties such as shape and size. Three fractions of glass particles with different shapes are investigated, fibres, fragments, spheres, and their wettability is modified by esterification with alcohols. These particle systems are characterised via analytic particle solvent extraction, static and dynamic contact angle measurements, and inverse gas chromatography. Alcohols with longer alkyl chains result in more hydrophobic particles with more homogeneous wettability characteristics in terms of surface energy. Comparing the characterisation methods reveals the influence of particle morphology on the interfacial wetting behaviour. Applying inverse gas chromatography for wettability characterisation in combination with the other methods underlines its potentials as well as limitations in understanding particulate surface properties.

Keywords: Wettability; Hydrophobicity; Surface heterogeneity; Surface free energy; Inverse gas chromatography; Contact angle

Permalink: https://www.hzdr.de/publications/Publ-32962
Publ.-Id: 32962


Development of machine learning framework for interface force closures based on bubble tracking data

Tai, C.-K.; Bolotnov, I.; Evdokimov, I.; Schlegel, F.; Lucas, D.

Understanding the liquid-water interaction serves as the basis to credibility of two-phase flow models and
safety of light water reactors. The topic is of researchers’ long interest due to the complexity of underlying
physics. Recently, with growing availability to high performance computing resources, interface tracking
direct numerical simulation becomes an advantage measure to probe the two-phase flow. Resulting
accumulation of high-fidelity numerical data also makes data-driven modeling with machine learning
methods an attractive option to gain insight to the phenomena.

This work presents an interfacial force data-driven modeling framework aims to develop a bubble tracking
direct numerical simulation data-based machine learning drag model for application in Euler-Euler
simulations of bubbly flows. Besides technical demonstration, this work also provides a guidance for DNS
data generation for relevant applications.

The data-driven modeling framework is firstly verified by a benchmark problem, where artificial data is
utilized to make feedforward neural network assimilate drag correlation by Tomiyama et al. (1998). The
obtained model is utilized in a Euler-Euler solver for on-the-fly drag coefficient query. In the test case,
resulting velocity and void fraction distribution by machine learning model is consistent with the reference
model.

Secondly, this work utilized direct numerical simulation bubble tracking data set to form machine learning
drag model for bubbly flow based on Reynolds and Eötvös number. Pseudo-steady state filtering in Frenet
frame is carried out to obtain bubble drag coefficient. The machine learning drag model is examined in a
test case by Wang et al. (1987). Results and suggestions for future works are discussed.

Keywords: direct numerical simulation; interfacial force modeling; machine learning

  • Contribution to proceedings
    19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19), 06.-11.03.2022, Brüssel, Belgien
    Proceedings of NURETH-19
  • Open Access Logo Nuclear Engineering and Design 399(2022), 112032
    DOI: 10.1016/j.nucengdes.2022.112032
    Cited 2 times in Scopus

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Publ.-Id: 32961


Organische Synthese einer potenten Leitverbindung zur Entwicklung neuer Radioliganden für die molekulare Bildgebung der mutierten Form der Isocitrat-Dehydrogenase 1 im Gehirn mittels Positronen-Emissions-Tomographie

Linke, J.

Organische Synthese einer potenten Leitverbindung zur Entwicklung neuer Radioliganden für die molekulare Bildgebung der mutierten Form der Isocitrat-Dehydrogenase 1 im Gehirn mittels Positronen-Emissions-Tomographie

Keywords: Isocitrat-Dehydrogenase 1; mIDH1; Ligand; PET; molekulare Bildgebung

  • Master thesis
    Universität Leipzig, 2021
    Mentor: Dr. Rodrigo Teodoro, Dr. Matthias Scheunemann
    80 Seiten

Permalink: https://www.hzdr.de/publications/Publ-32960
Publ.-Id: 32960


Large-scale test facility for modeling bubble behavior and liquid metal two-phase flows in a steel ladle

Wondrak, T.; Timmel, K.; Bruch, C.; Gardin, P.; Hackl, G.; Lachmund, H.; Bodo Lüngen, H.; Odenthal, H.-J.; Eckert, S.

A new experimental facility has been designed and constructed which represents a 1:5.25 model of an industrial 185 t steel ladle. This setup is intended for systematic investigations of complex liquid metal multiphase flows created by gas blowing from the bottom. Two tons of a Sn40wt.%Bi alloy are employed as working fluid, its thermophysical properties are very similar to those of liquid steel. The relatively low operating temperatures (T~200°C) compared to the real industrial process allow the use of powerful measuring techniques for characterizing the behavior of the gas phase and resulting flow regimes. Argon gas is injected through diverse plug systems into a cylindrical fluid vessel which is equipped with a pressure tight lid to achieve low-pressure conditions for vacuum processing. This paper presents first measurements of the gas distribution close to the free liquid metal surface for various gas flow rates, plug positions and types. Moreover, the pressure in the vessel has been varied between 1 mbar and ambient pressure. The experiments provide a copious data base about the flow regimes, void fraction, liquid and bubble velocities, and bubble properties, which can be used to provide so far unknown boundary conditions for numerical simulations of various metallurgical reactors such as steelmaking converters or steelmaking ladles.

Keywords: liquid metal; two-phase flow; bubble measurement; ladle treatment

Permalink: https://www.hzdr.de/publications/Publ-32959
Publ.-Id: 32959


A particle-center-averaged Euler-Euler model for monodisperse bubbly flows

Lyu, H.; Lucas, D.; Rzehak, R.; Schlegel, F.

The standard Euler-Euler model is based on the phase-averaging method. Each bubble force is a function of the local gas volume fraction. As a result, the coherent motion of each bubble as a whole is not enforced when the bubble diameter is larger than the mesh size. However, the bubble force models are typically developed by tracking the bubbles' centers of mass and assuming that the forces act on these locations. In simulations, this inconsistency can lead to a nonphysical gas concentration in the center or near the wall of a pipe when the bubble diameter is larger than the mesh size. Besides, a mesh independent solution may not exist in such cases.

In the present contribution, a particle-center-averaging method is used to average the solution variables for the disperse phase, which allows to represent the bubble forces as forces that act on the bubbles' centers of mass. An approach to simulate bubbly flows is formed by combining the Euler-Euler model framework using the particle-center-averaging method and a diffusion-based method that relates phase-averaged and particle-center-averaged quantities. The remediation of the inconsistency with the standard Euler-Euler model based on phase-averaging method is demonstrated using a simplified two-dimensional test case. The test results illustrate that the particle-center-averaging method can alleviate the over-prediction of the gas volume fraction peak in the channel center and provide mesh independent solutions. Furthermore, a comparison of both approaches is shown for several bubbly pipe flow cases where experimental data are available. The results show that the particle-center-averaging method can alleviate the over-prediction of the gas volume fraction peaks in the wall peaking cases as well.

Keywords: particle-center-averaging; phase-averaging; bubble number density; diffusion equation; wall-contact force model; multiphase flow; Euler-Euler model

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Publ.-Id: 32958


Stretchable Thin Film Mechanical Strain Gated Switches and Logic Gate Functions Based on a Soft Tunneling Barrier

Chae, S.; Jin Choi, W.; Fotev, I.; Bittrich, E.; Uhlmann, P.; Schubert, M.; Makarov, D.; Wagner, J.; Pashkin, O.; Fery, A.

Mechanical strain gated switches are cornerstone components of material embedded circuits that perform logic operations without using conventional electronics. This technology requires a single material system to exhibit three distinct functionalities: strain-invariant conductivity and an increase or decrease of conductivity upon mechanical deformation. Herein, we demonstrate mechanical strain-gated electric switches based on a thin-film architecture that features an insulator-to-conductor transition when mechanically stretched. The conductivity changes by nine orders of magnitude over a wide range of tunable working strains (as high as 130%). Our approach relies on a nanometer-scale sandwiched bi-layer Au thin film with an ultrathin polydimethylsiloxane elastomeric barrier layer applied strain alters the electron tunneling currents through the barrier. Mechanical-force-controlled electric logic circuits are achieved by realizing strain-controlled basic (AND and OR) and universal (NAND and NOR) logic gates in a single system. The proposed material system can be used to fabricate material-embedded logics of arbitrary complexity for wide range of applications including soft robotics, wearable/implantable electronics, human machine interface and internet of things.

Keywords: Strain gated electric switch; logic gates; tunneling; stretchable circuit; thin film

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Permalink: https://www.hzdr.de/publications/Publ-32957
Publ.-Id: 32957


Inverted fine structure of a 6H-SiC qubit enabling robust spin-photon interface

Breev, I. D.; Shang, Z.; Poshakinskiy, A. V.; Singh, H.; Berencen, Y.; Hollenbach, M.; Nagalyuk, S. S.; Mokhov, E. N.; Babunts, R. A.; Baranov, P. G.; Suter, D.; Tarasenko, S. A.; Astakhov, G.; Anisimov, A. N.

Optically controllable solid-state spin qubits are one of the basic building blocks for applied quantum technology. Efficient extraction of emitted photons and a robust spin-photon interface are crucial for the realization of quantum sensing protocols and essential for the implementation of quantum repeaters. Though silicon carbide (SiC) is a very promising material platform hosting highly-coherent silicon vacancy spin qubits, a drawback for their practical application is the unfavorable ordering of the electronic levels in the optically excited state. Here, we demonstrate that due to polytypism of SiC, a particular type of silicon vacancy qubits in 6H-SiC possesses an unusual inverted fine structure. This results in the directional emission of light along the hexagonal crystallographic axis, making photon extraction more efficient and integration into photonic structures technologically straightforward. From the angular polarization dependencies of the emission, we reconstruct the spatial symmetry and determine the optical selection rules depending on the local deformation and spin-orbit interaction, enabling direct implementation of robust spin-photon entanglement schemes. Furthermore, the inverted fine structure leads to unexpected behavior of the spin readout contrast. It vanishes and recovers with lattice cooling due to two competing optical spin pumping mechanisms. Our experimental and theoretical approaches provide a deep insight into the optical and spin properties of atomic-scale qubits in SiC required for quantum communication and distributed quantum information processing.

Keywords: Solid-state spin qubits; Silicon vacancy; 6H-SiC; Quantum communication

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Publ.-Id: 32955


Numerical Investigation of Degasification in an Electrocoagulation Reactor

Höhne, T.; Farhikhteh Asl, V.; Ople Villacorte, L.; Herskind, M.; Momeni, M.; Al-Fayyad, D.; Taș-Koehler, S.; Lerch, A.

In order to enhance retention of particulate and colloidal (organic) matter, chemical coagulation (CC) is often used prior to pressure driven membrane filtration. Electrocoagulation (EC) is an alternative to CC usually carried out in an electrochemical reactor consisting of an electrolytic cell containing at least one anode (sacrificial) and one cathode. The EC combined with a membrane filtration to a hybrid membrane system may be a potential possibility for environmental problems dealing with drinking water treatment, water reuse and rational waste management. In this study, an EC reactor with spiral electrodes was investigated numerically, focusing on modelling with a given design/geometry, configuration and boundary conditions. Two-phase flow interactions between water (liquid) and hydrogen (gas) were modelled via computational fluid dynamics (CFD). Different flow rates (Q=1-1000 l/h) through two batches of the watering stage (Case 1-3) and the degassing stage (Case 4-6) were simulated. Degassing the feed of the membrane system is of high importance in order to achieve stable operation. The results provided information about flow characteristics such as sufficient retention time, water circulation by velocity vectors, undesirable gas penetration into the water inlet channel, gas holdup during watering and degassing, and finally the optimal period for the degasification. The results showed that as the water velocity increases, retention time decreases. The results also showed that thirty seconds seemed the optimal time with the gas holdup of 0.020%, 0.028%, and 0.027% respectively for Case 4, Case 5, and Case 6. Another finding is that the consideration for the most abundant gas holdup for the typical BC was the smallest ratio of water flow to gas flow.

Keywords: hybrid membrane process; electrocoagulation; CFD; hydrogen bubble; degassing optimization

Permalink: https://www.hzdr.de/publications/Publ-32954
Publ.-Id: 32954


An updated strategic research agenda for the integration of radioecology in the european radiation protection research

Gilbin, R.; Arnold, T.; Beresford, N. A.; Berthomieu, C.; Brown, J. E.; de With, G.; Horemans, N.; Madruga, M. J.; Masson, O.; Merroun, M.; Michalik, B.; Muikku, M.; O’Toole, S.; Mrdakovic Popic, J.; Nogueira, P.; Real, A.; Sachs, S.; Salbu, B.; Stark, K.; Steiner, M.; Sweek, L.; Vandenhove, H.; Vidal, M.; Vives I. Batlle, J.

The ALLIANCE Strategic Research Agenda (SRA) for radioecology is a living document that defines a long-term vision (20 years) of the needs for, and implementation of, research in radioecology in Europe. The initial SRA, published in 2012, included consultation with a wide range of stakeholders (Hinton et al., 2013). This revised version is an update of the research strategy for identified research challenges, and includes a strategy to maintain and develop the associated required capacities for workforce (education and training) and research infrastructures and capabilities. Beyond radioecology, this SRA update constitutes a contribution to the implementation of a Joint Roadmap for radiation protection research in Europe (CONCERT, 2019a). This roadmap, established under the H2020 European Joint Programme CONCERT, provides a common and shared vision for radiation protection research, priority areas and strategic objectives for collaboration within a European radiation protection research programme to 2030 and beyond. Considering the advances made since the first SRA, this updated version presents research challenges and priorities including identified scientific issues that, when successfully resolved, have the potential to impact substantially and strengthen the system and/or practice of the overall radiation protection (game changers) in radioecology with regard to their integration into the global vision of European research in radiation protection. An additional aim of this paper is to encourage contribution from research communities, end users, decision makers and other stakeholders in the evaluation, further advancement and accomplishment of the identified priorities.

Keywords: Strategic Research Agenda for radioecology; Environmental exposure to radionuclides; Radiation protection of the environment; Integration of radiation protection research; Education and training; Infrastructures

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Large magnetic entropy change in Nd2In near the boiling temperature of natural gas

Liu, W.; Scheibel, F.; Gottschall, T.; Bykov, E.; Dirba, I.; Skokov, K.; Gutfleisch, O.

Natural gas is useful for the transition from traditional fossil fuels to renewable energies. The consumption of liquid natural gas has been rising, and the demand is predicted to double by 2040. In this context, magnetocaloric gas liquefaction, as an emerging and energy-saving technology, could be an alternative to the traditional gas-compression refrigeration. In this work, we report a large magnetic entropy change of 7.42 J/kg K under a magnetic field change of 2 T in Nd2In at 109 K, which is near the boiling temperature of natural gas of 112 K. The maximum adiabatic temperature change reaches 1.13K under a magnetic field change of 1.95 T and is fully reversible. The magnetic phase transition is confirmed to be of the first-order type with the negligible thermal hysteresis. Further investigations on the thermal expansion and the magnetostriction reveal that the magnetic transition undergoes two stages with a negligible volume change. The longitudinal strain increases with magnetic fields and then decreases. These interesting properties are useful for the practical design of a magnetocaloric natural gas liquefaction system and for the fundamental understanding of the phase transitions in other RE2In intermetallics.

Permalink: https://www.hzdr.de/publications/Publ-32952
Publ.-Id: 32952


Influence of microstructure on the application of Ni-Mn-In Heusler compounds for multicaloric cooling using magnetic field and uniaxial stress

Pfeuffer, L.; Gracia-Condal, A.; Gottschall, T.; Koch, D.; Faske, T.; Bruder, E.; Lemke, J.; Taubel, A.; Ener, S.; Scheibel, F.; Durst, K.; Skokov, K. P.; Manosa, L.; Planes, A.; Gutfleisch, O.

Novel multicaloric cooling utilizing the giant caloric response of Ni-Mn-based metamagnetic shape- memory alloys to different external stimuli such as magnetic field, uniaxial stress and hydrostatic pressure is a promising candidate for energy-efficient and environmentally-friendly refrigeration. However, the role of microstructure when several external fields are applied simultaneously or sequentially has been scarcely discussed in literature. Here, we synthesized ternary Ni-Mn-In alloys by suction casting and arc melting and analyzed the microstructural influence on the response to magnetic fields and uniaxial stress. By combining SEM-EBSD and stress-strain data, a significant effect of texture on the stress- induced martensitic transformation is revealed. It is shown that a <001> texture can strongly reduce the critical transformation stresses. The effect of grain size on the material failure is demonstrated and its influence on the magnetic-field-induced transformation dynamics is investigated. Temperature-stress and temperature-magnetic field phase diagrams are established and single caloric performances are characterized in terms of ΔsT and ΔTad. The cyclic ΔTad values are compared to the ones achieved in the multicaloric exploiting-hysteresis cycle. It turns out that a suction-cast microstructure and the combination of both stimuli enables outstanding caloric effects in moderate external fields which can significantly exceed the single caloric performances. In particular for Ni-Mn-In, the maximum cyclic effect in magnetic fields of 1.9 T is increased by more than 200 % to -4.1 K when a moderate sequential stress of 55 MPa is applied. Our results illustrate the crucial role of microstructure for multicaloric cooling using Ni-Mn- based metamagnetic shape-memory alloys.

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Publ.-Id: 32951


Evaluation of the effective temperature change in Gd-based composite wires assessed by static and pulsed-field magnetic measurements

Beyer, L.; Weise, B.; Freudenberger, J.; Hufenbach, J. K.; Gottschall, T.; Krautz, M.

Gd cladded in a seamless 316L austenitic steel tube has been swaged into wires by the powder-in-tube (PIT) technology, resulting in an outer diameter of 1 mm, a wall thickness of approx. 100 μm and a filling factor of around 62 vol%. Such wires provide an advantageous geometry for heat exchangers and have the benefit to protect the Gadolinium, i.e. from corrosion when being in contact with a heat transfer fluid. The magnetocaloric composite has been studied by static and pulsed magnetic-field measurements in order to evaluate the performance of Gd as a core material. By the analysis of magnetization and heat capacity data, the influences of deformation-induced defects on Gadolinium are presented. The subsequent heat treatment at 773 K for 1 h in Ar atmosphere allowed restoring the magnetic properties of the wire after deformation. Data of the pulsed magnetic-field measurements on the Gd-filled PIT-wires and a Gd–core separated from the jacket are presented, with an achievable temperature change of 1.2 K for the wire and 5.2 K for the Gd in 2 T, respectively. A comparison to previously studied La(Fe, Co, Si)13-filled composite wires is included. It indicates that performance losses due to the passive matrix material cannot be overcome only by an increased adiabatic temperature change of the core material, but instead the wire components need to be chosen regarding an optimized heat capacity ratio, as well.

Permalink: https://www.hzdr.de/publications/Publ-32950
Publ.-Id: 32950


THEREDA – Thermodynamic Reference Database for the nuclear waste disposal in Germany

Bok, F.; Moog, H. C.; Gaona, X.; Freyer, D.; Wissmeier, L.

The disposal of nuclear waste including the assessment of long-term safety is still an open question in Germany. In addition to the pending decision about the repository host rock (salt, granite, or clay) and the associated site selection, the basic necessity of a consistent and obligatory thermodynamic reference database persists. Such a database is essential to assess potential radionuclide migration scenarios accurately and to make well-founded predictions about the long-term safety up to one million years. Specific challenges are comprehensive datasets covering also elevated temperatures and high salinities. Concerning the required elements (actinides, fission products as well as matrix and building materials), no other thermodynamic database is available that is compatible with the expected conditions. Due to these deficiencies THEREDA (Altmaier et al., 2008&&>&&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt> Moog et al., 2015) a joint project of institutions leading in the field of safety research for nuclear waste disposal in Germany and Switzerland, was started in the year 2006.

Database features
THEREDA offers evaluated thermodynamic data for many compounds (solid phases, aqueous species, or constituents of the gaseous phase) of elements relevant according to the present state of research. In particular, all oxidation states expected for disposal site conditions are considered. In the present release, THEREDA includes data for actinides and their chemical analogues (Th, U, Np, Pu, Am, Cm & Nd), fission products (Se, Sr, Tc & Cs) and matrix elements (Na, K, Mg, Ca, Al, Si | Cl, SO4, CO3). For the calculation of cementitious phases the current version of CEMDATA (18.1) was integrated (Lothenbach et al, 2019).
THEREDA is based on a relational databank whose structure intrinsically ensures the internal consistency of thermodynamic data. Data considered respond to the needs of both Gibbs Energy Minimizers (ChemApp, GEMS) and Law-of-Mass-Action codes (Geochemist’s Workbench, PHREEQC, ToughReact). The database is designed generically so that it can store interaction parameters for various models. Namely, the PITZER ion interaction approach to describe activity coefficients of hydrated ions and molecules in saline solutions (Pitzer, 1991) as well as ideal and non-ideal solid solution approaches are considered in the actual dataset.
THEREDA is accessible via internet through www.thereda.de. This is not only a portal to view the data, uncertainties and the primary references of the data&&>&&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt> it provides also additional information on issues concerning the database. Ready-to-use parameter files are available for download in a variety of formats (geochemical code specific formats and generic ASCII type). They are also used for internal test calculations – an essential element of the quality assurance scheme. The capabilities of THEREDA are demonstrated using approx. 400 application case calculations, whose results were compared with experimental values published in literature.

Keywords: THEREDA; Thermodynamic Reference Database; Pitzer; Solubility; thermodynamic data

  • Poster
    3rd Conference on Key Topics in Deep Geological Disposal, 04.-06.07.2022, Köln, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-32949
Publ.-Id: 32949


Plasmonic terahertz nonlinearity in graphene disks

Han, J.; Chin, M. L.; Matschy, S.; Poojali, J.; Seidl, A.; Winnerl, S.; Hafez, H. A.; Turchinovich, D.; Kumar, G.; Myers-Ward, R. L.; Dejarld, M. T.; Daniels, K. M.; Drew, H. D.; Murphy, T. E.; Mittendorff, M.

The discovery of graphene and its unique optical and electronic properties triggered intense developments in a vast number of optoelectronic applications, especially in spectral regions that are not easily accessible with conventional semiconductors. Particularly in the THz regime, where the free-carrier interaction with low energetic photons usually dominates, detectors and modulators based on graphene often feature an improved response time. Nevertheless, the light-matter interaction suffers from the small interaction volume. One way to enhance the efficiency of such devices at elevated frequencies, is patterning graphene into plasmonic structures like disks. In addition to the increased linear absorption, the plasmon resonance also creates a strong, surface-localized field that enhances the nonlinear optical response. While experimental studies so far have focused on hot carrier effects, theoretical studies also suggest an increase of the nonlinearity beyond thermal effects. Here we present polarization dependent pump-probe measurements on graphene disks that enable disentangling the contributions of thermal and plasmonic nonlinearity. An increase of the pump-induced transmission is observed when pump and probe radiation are co-polarized. To further elucidate the interplay of thermal and plasmonic effects, we develop a model that supports the origin of the polarization dependent enhancement of the observed THz nonlinearities.

Keywords: graphene; plasmon; nonlinearity; polarization dependence

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Permalink: https://www.hzdr.de/publications/Publ-32948
Publ.-Id: 32948


Correlated effects of fluorine and hydrogen in fluorinated tin oxide (FTO) transparent electrodes deposited by sputtering at room temperature

Morán-Pedroso, M.; Gago, R.; Julin, J. A.; Salas-Colera, E.; Jimenez, I.; de Andrés, A.; Prieto, C.

The optical and electrical properties of fluorinated tin oxide (FTO) films deposited at room temperature by sputtering have been investigated varying the fluorine content and the hydrogen atmosphere. The complex behavior of the obtained films is disclosed using a wide set of characterization techniques that reveals the combined effects of these two parameters on the generated defects. These defects control the electrical transport (carrier density, mobility and conductivity), the optical properties (band gap and defects-related absorption and photoluminescence) and finally promote the amorphization of the samples. H₂ in the sputtering gas does not modify the H content in the films but induces the partial reduction of tin (from Sn4+ to Sn2+) and the consequent generation of oxygen vacancies with shallow energy levels close to the valence band. A variation of up to four orders of magnitude in electrical conductivity is reported in samples with the appropriate fluorine doping and hydrogen fraction in the sputtering gas, maintaining excellent optical transparency. Optimized room temperature grown electrodes reach sheet resistance ~20 Ω/□ and transparency >90%. This room temperature deposition process enables film preparation on flexible organic substrates, such as polyethylene terephthalate (PET), with identical performance of doubtless interest in flexible and large scale electronics.

Keywords: Transparent conductive materials; Fluorinated tin oxide; Room temperature film preparation

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Permalink: https://www.hzdr.de/publications/Publ-32947
Publ.-Id: 32947


Impact of Si on the high-temperature oxidation of AlCr(Si)N coatings

Jager, N.; Meindlhumer, M.; Zitek, M.; Spor, S.; Hruby, H.; Nahif, F.; Julin, J.; Keckes, J.; Mitterer, C.; Daniel, R.

The resistance of wear protective coatings against oxidation is crucial for their use at high temperatures. Here, three nanocomposite AlCr(Si)N coatings with a fixed Al/Cr atomic ratio of 70/30 and a varying Si-content of 0 at.%, 2.5 at.% and 5 at.% were analyzed by differential scanning calorimetry, thermogravimetric analysis and X-ray in order to understand the oxidation behavior depending on their Si-content. Additionally, a partially oxidized AlCrSiN coating with 5 at.% Si on a sapphire substrate was studied across the coating thickness by depth-resolved cross-sectional X-ray nanodiffraction and scanning trans-mission electron microscopy to investigate the elemental composition, morphology, phases and residual stress evolution of the oxide scale and the non-oxidized coating underneath. The results reveal enhanced oxidation properties of the AlCr(Si)N coatings with increasing Si-content, as demonstrated by a retarded onset of oxidation to higher temperatures from 1100 °C for AlCrN to 1260 °C for the Si containing coatings and a simultaneous deceleration of the oxidation process. After annealing of the AlCrSiN sample with 5 at.% Si at an extraordinary high temperature of 1400 °C for 60 min in ambient air, three zones developed throughout the coating strongly differing in their composition and structure: (i) a dense oxide layer comprising an Al-rich and a Cr-rich zone formed at the very top, followed by (ii) a fine-grained transition zone with incomplete oxidation and (iii) a non-oxidized zone with a porous structure. The varying elemental composition of these zones is furthermore accompanied by micro-structural variations and a complex residual stress development revealed by cross-sectional X-ray nanodiffraction. The results provide a deeper understanding of the oxidation behavior of AlCr(Si)N coatings depending on their Sicontent and the associated elemental, microstructural and residual stress evolution during high-temperature oxidation.

Keywords: AlCrSiN; Nanocomposite; Cathodic arc; Oxidation behaviour; Cross-sectional X-ray nanodiffraction

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Permalink: https://www.hzdr.de/publications/Publ-32946
Publ.-Id: 32946


The application of deep learning on slit-scan images processing and emittance prediction

Ma, S.; Arnold, A.; Ryzhov, A.; Schaber, J.; Petr, M.; Paul, Z.; Teichert, J.; Xiang, R.

The radiation source ELBE (Electron Linac for beams with high Brilliance and low Emittance) delivers multiple secondary beams, both electromagnetic radiation, and particles. To measure beam emittance effectively before user time, a fast and accurate method, the continue moving slit-scan system for high bunch charge has been developed. To accelerate the process of the images, the parallel algorithm, images classification Convolutional Neural Network (CNN), and autoencoder network are used.

Keywords: emittance; slit-scan; deep learning

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  • Open Access Logo Lecture (Conference) (Online presentation)
    DPG-Frühjahrstagung (Dortmund), 15.-19.03.2021, Dortmund, Germany

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Permalink: https://www.hzdr.de/publications/Publ-32945
Publ.-Id: 32945


UDV methods for characterizing flows in liquid metal batteries

Cheng, J.; Wang, B.; Mohammad, I.; Horstmann, G. M.; Kelley, D.

We present ultrasound measurements from a laboratory model of a liquid metal battery (LMB). Two major flow
drivers interact within LMBs: thermal gradients due to the presence of internal heating, and electrovortex flow
(EVF) driven by diverging current densities. The product of these interactions remains poorly characterized. We
approach this problem with ultrasonic Doppler velocimetry (UDV) combined with a laboratory model of an LMB
fluid layer. Using ultrasound probes placed around a liquid gallium vessel, we elucidate typical velocities, flow
structures, and flow statistics in a representative volume of the flow field. UDV measurements reveal that pure
convection takes the form of the recently-discovered ‘jump rope vortex,’ with a characteristic frequency visible in
velocity statistics. They also indicate that EVF goes through stable, unstable, and oscillatory flow regimes. In
progress is an approach for training physics-informed neural networks (PINNs) on UDV data, allowing us to
reconstruct flow in regions where no probe measurements have taken place by leveraging the equations of motion.

  • Contribution to proceedings
    13th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering (ISUD 2021), 13.-15.06.2021, Zürich, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-32944
Publ.-Id: 32944


Highlight selection of radiochemistry and radiopharmacy developments by editorial board

Alves, F.; Antunes, I.; Cazzola, E.; Cleeren, F.; Cornelissen, B.; Denkova, A.; Engle, J.; Faivre-Chauvet, A.; Gillings, N.; Hendrikx, J.; Jalilian, A.; van der Meulen, N.; Mikolajczak, R.; Neels, O.; Pillai, M.; Reilly, R.; Rubow, S.; Seimbille, Y.; Spreckelmeyer, S.; Szymanski, W.; Taddei, C.

Background: The Editorial Board of EJNMMI Radiopharmacy and Chemistry releases a biyearly highlight commentary to update the readership on trends in the field of radiopharmaceutical development.
Results: This commentary of highlights has resulted in 21 different topics selected by each member of the Editorial Board addressing a variety of aspects ranging from novel radiochemistry to first in man application of novel radiopharmaceuticals. Also the first contribution in relation to MRI-agents is included.
Conclusion: Trends in (radio)chemistry and radiopharmacy are highlighted demonstrating the progress in the research field being the scope of EJNMMI Radiopharmacy and Chemistry.

Permalink: https://www.hzdr.de/publications/Publ-32943
Publ.-Id: 32943


Hydrodynamic and efficiency data pertaining to an air-water column mockup (of 0.8 m internal diameter) equipped with sieve trays

Vishwakarma, V.; Marchini, S.; Schleicher, E.; Schubert, M.; Hampel, U.
DataCollector: Vishwakarma, Vineet; DataCollector: Marchini, Sara; RelatedPerson: Schleicher, Eckhard; ContactPerson: Schubert, Markus; Supervisor: Hampel, Uwe

The hydrodynamic data including effective froth height, liquid holdup and tracer flow and patterns related to an operational sieve tray inside a 0.8 m diameter air-water column simulator are provided here. These data were obtained via an advanced multiplex flow profiler at several gas and liquid loadings. The generated data were examined for predicting the tray efficiency using mathematical models. For model validation, the stripping of isobutyl acetate from the aqueous solution over the tray was employed, and the liquid samples at several tray locations were analyzed via UV spectroscopy. The resulting efficiencies and related information are provided here, too. All raw data files, data processing scripts and supporting information with proper indexing and sequencing are uploaded. All these data are intended for non-commercial use only.

Keywords: Column tray; two-phase crossflow; 3D liquid holdup; effective froth height; tracer-response analysis; tray efficiency calculations

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Permalink: https://www.hzdr.de/publications/Publ-32942
Publ.-Id: 32942


Curium(III) speciation in the presence of microbial cell wall components

Moll, H.; Barkleit, A.; Frost, L.; Raff, J.

Trivalent actinides such as Cm(III) are able to strongly interact with microbes and especially with bacterial cell walls. However, detailed knowledge of the influence of different cell wall components is somewhat lacking. For this investigation, we studied the formation of aqueous Cm(III) complexes with cell wall components (e.g., lipopolysaccharide, peptidoglycan, and plasma membranes) using time-resolved laser-induced fluorescence spectroscopy (TRLFS). For all systems, two specific Cm(III) complexes with the biomacromolecules were observed as a function of pH. Specifically, Cm(III) was found to bind to phosphate and carboxyl groups present in the structure of the biomacromolecules. Stability constants and luminescence parameters of the specific Cm(III) complexes were determined and are presented. The pH of the surrounding aqueous solution, the plasma membrane concentration, and proteins included in the crude plasma membrane fraction were found to significantly impact the complexation of Cm(III). The Cm(III) luminescence spectra with plasma membranes, cell wall polymers, as well as Gram-negative (Sporomusa sp. MT-2.99 and Pseudomonas fluorescens) and Gram-positive (Paenibacillus sp. MT-2.2) bacteria will be explained by linear combination fitting using the investigated components.

Keywords: curium; lipopolysaccharide; peptidoglycan; plasma membrane; bacterial cell walls; luminescence spectroscopy

Permalink: https://www.hzdr.de/publications/Publ-32941
Publ.-Id: 32941


Spin pumping at interfaces with ferro- and paramagnetic Fe60Al40 films acting as spin source and spin sink

Strusch, T.; Lenz, K.; Meckenstock, R.; Bali, R.; Ehrler, J.; Lindner, J.; Faßbender, J.; Farle, M.; Potzger, K.; Semisalova, A.

We present a study of spin pumping efficiency and determine the spin mixing conductance and spin diffusion length in thin bilayer films based on 3d transition metal alloy Fe60Al40. Due to its magnetostructural phase transition, Fe60Al40 can be utilized as a ferromagnetic (FM) or paramagnetic (PM) material at the same temperature depending on its structural order, thus thin Fe60Al40 film can act as a spin source or a spin sink when interfaced with a paramagnet or a ferromagnet, correspondingly. Ferromagnetic resonance (FMR) measurements were performed in a frequency range of 5 - 35 GHz on bilayer films composed of FM-Fe60Al40 / Pd and PM-Fe60Al40 / permalloy Ni80Fe20. The increase of damping parameter with the thickness of paramagnetic layer was interpreted as a result of spin pumping into a paramagnet. In the first case, the FM-Fe60Al40 acts as a spin source and in the second case PM-Fe60Al40 serves as a spin sink. We determine the spin mixing conductance 𝑔𝑃𝑑↑↓=(3.8±0.5)×1018 m-2 at the FM-Fe60Al40/Pd interface and the spin diffusion length 𝜆𝑃𝑑=9.1 ±2.0 nm in Pd. For the PM-Fe60Al40/permalloy interface we find a spin mixing conductance 𝑔𝐹𝑒𝐴𝑙↑↓=(2.1±0.2)×1018 m-2 and a spin diffusion length 𝜆𝐹𝑒𝐴𝑙=11.9 ±0.2 nm for PM-Fe60Al40. Demonstrated bi-functionality of Fe60Al40 alloy in spin pumping structures may be promising for spintronic applications

Keywords: Ferromagnetic resonance; spin pumping; ferromagnetic films; ferromagnetism; FeAl alloys; spin diffusion; damping; linewidth

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Permalink: https://www.hzdr.de/publications/Publ-32940
Publ.-Id: 32940


Direct tomographic observation of brine percolation into MgO-shotcrete drill cores

Kulenkampff, J.

Heterogeneity and tightness of the barrier demand particular sensitive and lasting measuring methods, as well as resolution of small details. For this reason we developed a guard-ring surface-packer for process tomography of brine migration into barrier material with positron-emission-tomography (PET). Based on radiolabeling, this method is extremely sensitive, non-destructive and without retroaction.
As example for transport in the engineered barrier, we investigated injection of [²²Na]NaCl-sat – solution from a fluid reservoir with a diameter of 20 mm into the contact zone of adjacent MgO-shotcrete layers. The driving pressure was 2 bar, which caused intrusion of 1 mL of solution over a period of 260 d.
Overlay of the sequence of PET images and the structural CT image shows that deeper penetration (> 10 mm) occurred predominantly along one single pathway that was predetermined by the porous structure. Also, we observed a slowly propagating diffuse front that encompassed only a small portion of the injected fluid.
Although the permeability of the material is very low (1e-20 m²), the major portion of the brine propagates through a very confined channel and thus may reach a significant penetration depth, beyond the predictions based on assumed homogeneous material.

Keywords: radioactive waste disposal; engineered barrier; transport experiments; positron emission tomography; CT; MgO

  • Open Access Logo Lecture (Conference)
    Saltmech X, 05.-08.07.2022, Utrecht, Nederland
    DOI: 10.1201/9781003295808
  • Open Access Logo Contribution to proceedings
    10th Conference on the Mechanical Behavior of Salt (SaltMech X), 05.-08.07.2022, Utrecht, Nederland
    The Mechanical Behavior of Salt X Proceedings of the 10th Conference on the Mechanical Behavior of Salt (SaltMech X), Utrecht, The Netherlands, 06-08 July 2022, London: CRC Press, 9781003295808, 98-106
    DOI: 10.1201/9781003295808

Permalink: https://www.hzdr.de/publications/Publ-32939
Publ.-Id: 32939


Superconducting solenoid field measurement and optimization

Ma, S.; Arnold, A.; Ryzhov, A.; Murcek, P.; Zwartek, P.; Schaber, J.; Qian, H.; Teichert, J.; Xiang, R.

The solenoid is a significant part of an electron injector to provide a proper focusing, and preserve the beam projected emittance. A superconducting solenoid is applied for the SRF photoinjector at HZDR. The solenoid itself can degrade electron beam quality due to magnetic field imperfections like multipole components. In order to determine the field aberrations in the solenoid, we measured the superconducting solenoid magnetic field in the cryomodule. A simple and effective method is used to analyze the multipole field components, which will be presented in this paper.

Keywords: solenoid; magnetic field

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  • Open Access Logo Contribution to proceedings
    12th International Particle Accelerator Conference (IPAC’21), 24.-28.05.2021, Brasília, Brazil
    Proceedings of IPAC’21: JACoW

Permalink: https://www.hzdr.de/publications/Publ-32938
Publ.-Id: 32938


Generalized Landau-Khalatnikov-Fradkin transformations for arbitrary N-point fermion correlators

Ahmadiniaz, N.; Edwards, J. P.; Nicasio, J.; Schubert, C.

We examine the nonperturbative gauge dependence of arbitrary configuration space fermion correlators in quantum electrodynamics (QED). First, we study the dressed electron propagator (allowing for emission or absorption of any number of photons along a fermion line) using the first quantized approach to quantum field theory and analyze its gauge transformation properties induced by virtual photon exchange. This is then extended to the N-point functions where we derive an exact, generalized version of the fully nonperturbative Landau-Khalatnikov-Fradkin (LKF) transformation for these correlators. We discuss some general aspects of the application in perturbation theory and investigate the structure of the LKF factor aboutD¼2dimensions

Keywords: LKFT; Worldline formalism; Non-perturbative QED

Permalink: https://www.hzdr.de/publications/Publ-32937
Publ.-Id: 32937


Transport properties of systematically disordered Cr2AlC films

Salgado Cabaco, J.; Kentsch, U.; Lindner, J.; Faßbender, J.; Leyens, C.; Bali, R.; Boucher, R.

Nano-lamellar composite materials, known as MAX-phases, can possess a combination of ceramic and metallic properties. A prototype compound is Cr2AlC, formed from a unit cell of Cr2C sandwiched be-tween atomic planes of Al. Here we observe the modifications to the structural, transport and magnetic behavior of 500 nm thick Cr2AlC after irradiation with Co+ions, and Ar+noble gas ions as control.X-ray shows that ion-irradiation induces a suppression of the 0002 reflection, indicating a deterioration of the crystal structure. Increasing the ion fluence leads to an increase of the saturation magnetization at 1.5 K, whereby both Ar+ and Co+ cause an increased magnetization, respectively to 150 kA.m−1and 190 kA.m−1, for the highest fluences used. At Co+ fluences of 5E13 ions.cm−2 the magnetoresistance (MR) shows a 2 orders of magnitude increase, up to 3%(10 T) at 100K. A similar effect also occurs for 5E12 ions.cm−2 Ar+ irradiated films, however, with a smaller MR-increase. The disordering of MAX phase films may reveal interesting spin-related transport phenomena.

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  • Poster
    84. Jahrestagung der DPG, 27.09.2021, Online, Germany

Permalink: https://www.hzdr.de/publications/Publ-32936
Publ.-Id: 32936


High-entropy carbons: From high-entropy aromatic species to single-atom catalysts for electrocatalysis

Ding, J.; Wu, D.; Zhu, J.; Rodríguez-Hernández, F.; Chen, Y.; Lu, C.; Zhou, S.; Zhang, J.; Tranca, D.; Zhuang, X.

Single-atom catalysts (SACs) have rapidly entered the field of nanomaterials and demonstrated great potential for energy devices in recent years. Of all types of SACs, porous carbon-based SACs are the most popular species because of their excellent conductivity, large specific surface area, and easily tunable heteroatom and metal components. However, most of the reported cases focus on the metal centers and their coordination environments, while they do not pay much attention to carbon precursors and carbon transformation during high-temperature treatment. In this work, we use a high-entropy aromatic molecule, azulene, for rational synthesis of azulene-enriched, sandwich-like polymer nanosheets and corresponding single-Fe-dispersed porous carbon nanosheets. The azulene-based metal-free polymer nanosheets exhibit a narrow band gap and temperature-dependent magnetism. As proof-of-concept electrocatalysts for CO2 reduction, the prepared carbon nanosheets exhibit high activity and stability. Operando X-ray absorption spectroscopy and density functional theory studies reveal the high activity of Fe-N coordination sites in the presence of 5/7-membered carbon ring-based topological defects in the carbon skeleton. Taken together, this work provides a new method of synthesizing high-entropy carbons using azulene-based high-entropy molecule as precursor and paves the way toward high-efficiency SACs with rich topological defects for energy conversion.

Keywords: High-entropy aromatic molecule; Topological defect; Single-atom catalyst; Porous carbon nanosheet; Carbon dioxide conversion

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Permalink: https://www.hzdr.de/publications/Publ-32934
Publ.-Id: 32934


QE and life time of Cs2Te photocathodes on copper for SRF gun-II at HZDR

Xiang, R.; Arnold, A.; Ma, S.; Murcek, P.; Ryzhov, A.; Schaber, J.; Teichert, J.

The SRF gun-II at HZDR has been stably applied as the electron
source for high power THz radiation since 2018, generating CW beams
with bunch charges up to 300 pC at 100 kHz. It is an excellent demonstration
that SRF guns can work reliably in a high power user facility.
In order to generate higher current beam with MHz repetition rate,
Cs2Te photocathodes are required. However, in last two experiments
with Cs2Te, the Mo substrate plugs were overheated in superconducting
rf cavity. The reason is that different thermal expansion coefficient
of Mo and Cu led to a bad thermal contact between the Mo plug and
Cu holder. Thus we decided to use Cu as new substratum of Cs2Te
cathodes. In last year we prepared several Cs2Te photocathodes on Cu
plugs and improved the vacuum of cathode transfer system in order
to achieve satisfied lifetime. In this contribution, we will present the
study result of QE and life time of Cs2Te photocathodes with different
thickness.

Keywords: SRF gun; photocathode; Cs2Te

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Permalink: https://www.hzdr.de/publications/Publ-32933
Publ.-Id: 32933


Observability of Coulomb-assisted quantum vacuum birefringence

Ahmadiniaz, N.; Bussmann, M.; Cowan, T.; Debus, A.; Kluge, T.; Schützhold, R.

We consider the scattering of an x-ray free-electron laser (XFEL) beam on the superposition of
a strong magnetic field $\bf{B}_{\rm ext}$ with the Coulomb field $\bf{E}_{\rm ext}$
of a nucleus with charge number $Z$. In contrast to Delbr\"uck scattering
(Coulomb field only), the magnetic field $\bf{B}_{\rm ext}$
introduces an asymmetry (i.e., polarization dependence) and renders the effective interaction volume quite
large, while the nuclear Coulomb field facilitates a significant momentum transfer $\Delta\bf k$.
For a field strength of $B_{\rm ext}=10^6 T$ (corresponding to an intensity of order $10^{22}~\rm W/cm^2$)
and an XFEL frequency of 24~keV, we find a differential cross section
$d\sigma/d\Omega\sim10^{-25}~Z^2/(\Delta{\bf k})^2$ in forward direction for one nucleus.
Thus, this effect might be observable in the near future at facilities such as the
Helmholtz International Beamline for Extreme Fields (HIBEF) at the European XFEL.

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Permalink: https://www.hzdr.de/publications/Publ-32932
Publ.-Id: 32932


Caesium-deposition on GaN as a potential Photocathode

Schaber, J.; Xiang, R.; Teichert, J.; Arnold, A.; Ryzhov, A.; Murcek, P.; Zwartek, P.; Ma, S.

SRF injectors need materials which can promise high quantum efficiency, long lifetime and good vacuum stability, fast response time and low thermal emittance.
It is assumed that GaN, like GaAs, as a novel electron source for particle accelerators shows an enormous potential.
P-type GaN on different substrate material is activated by a thin layer of caesium and illuminated at the same time by ultra-violet (UV) light. As a consequence of a NEA surface and photoeffect, the generated photoelectrons enter into vacuum and are collected by an anode. The resulting photocurrent is detected during the whole activation process and stopped when a maximum photocurrent is reached. Quantum efficiency (QE) can be calculated from the photocurrent. Its decay is tracked in the following days after activation. It is also studied to re-activate the sample again by using thermal heat treatment and caesium Deposition once more.
High 11.5% QE can be provided from GaN:Cs on sapphire substrate at the moment. After 600 h of lifetime this photocathode shows still 1.4% QE.
Besides the outstanding experimental results so far further investigations are still required.

Keywords: gallium nitride; photocathode; SRF Gun; ceasium deposition; III-V semiconductor

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Permalink: https://www.hzdr.de/publications/Publ-32931
Publ.-Id: 32931


GaN:Cs Photocathode for SRF Guns

Schaber, J.; Xiang, R.; Teichert, J.; Arnold, A.; Ryzhov, A.; Murcek, P.; Zwartek, P.; Ma, S.

Magnesium bulk cathodes and caesium telluride cathodes work routinely in SRF Gun II at ELBE. However, the particle accelerator community is always looking for new materials which can promise higher quantum efficiency, longer lifetime and good vacuum stability, fast response time and low thermal emittance.
P-type GaN on different substrate material is activated by a thin layer of caesium and illuminated at the same time by ultra-violet light. As a consequence of a negative electron affinity and photoeffect, the generated photoelectrons enter into vacuum and are collected by a copper ring anode. The resulting photocurrent is detected during the activation process and stopped when a maximum photocurrent is reached. Quantum efficiency can be calculated from the photocurrent and its decay is tracked in the following days after activation.
By a comparison of differences in substrate material, chemical pre-cleaning, thermal heat treatment and activation parameters (e.g. caesium-flux), the photocurrent, quantum efficiency and its decay is studied.

Keywords: gallium nitride; photocathode; SRF Gun; caesium deposition

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Permalink: https://www.hzdr.de/publications/Publ-32930
Publ.-Id: 32930


Caesium deposition on GaN to obtain a photocathode for particle accelerator

Schaber, J.; Xiang, R.; Teichert, J.; Arnold, A.; Ryzhov, A.; Murcek, P.; Zwartek, P.; Ma, S.

Negative electron affinity (NEA) GaAs- and GaN-based photocathodes are used in modern night vison detectors and light emitting diodes1. GaAs semiconductors are already used as electron sources in particle accelerators and well- studied2. Like GaAs, GaN belongs to the
III-V semiconductor group with similar properties. It is assumed that GaN, like GaAs, shows enormous potential as a novel electron source for particle accelerators.

P-type GaN on different substrate material (sapphire, silicon, copper or SiC) is activated by a thin layer of caesium and illuminated by ultra-violet (UV) light at the same time. As a consequence of negative electron affinity (NEA) and photoeffect, the generated photoelectrons enter into vacuum and are collected by a copper ring anode. The resulting photocurrent is detected during the whole activation process and stopped when a maximum photocurrent is reached.
The GaN is chemical cleaned and transferred into a UHV chamber where it undergoes a thermal heat treatment at 250°C for 20 min using a halogen lamp. The aim of the thermal treatment is to remove residual adsorbed gas molecules from the sample surface.
Afterwards when the sample is back at room temperature, the thermal-cleaned GaN is activated with a thin layer of caesium. The photocurrent and the QE is observed in the following days until the QE vanishes. Then it is tested to re-activate the cathode again, meaning to thermal clean it again and to activate it with caesium once more.

By a comparison of differences in substrate material, chemical pre-cleaning, thermal heat treatment and activation parameters (e.g. caesium-flux), the photocurrent, quantum efficiency and the re-activation of the photocathode is studied. Additionally the GaN samples are examined by AFM, SEM and EDX.
From the experimental results obtained so far, it appears that GaN:Cs could be used as a photocathode in particle accelerators, but further investigations are still required and needed.

Keywords: gallium nitride; photocathode; caesium deposition; SRF Gun

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    DPG-Frühjahrstagung des Fachverbandes Oberflächenphysik, 01.-04.03.2021, Hannover, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-32929
Publ.-Id: 32929


Status Report of GaN photocathode

Schaber, J.; Xiang, R.; Teichert, J.; Ryzhov, A.; Murcek, P.; Zwartek, P.; Ma, S.

The photocathodes determine the beam quality in linear accelerators and represent a key component for many accelerator projects. Free-electron lasers (FEL), synchrotron- and THz radiation sources require injector systems with high brightness electron beams.

High quantum efficiency, a long lifetime and good vacuum stability, fast response time and low thermal emittance are desirable parameters for a perfect photocathode used in accelerators. Semiconductors such as GaN and GaAs as novel materials for photocathodes are showing an enormous potential.
GaAs is a well-known material for photocathodes. After activation with caesium and oxygen, it has a high QE for visible light (red or green). An advantage of GaAs is the opportunity of the layers to emit spin-polarized electrons.
GaN is a semi-conductive material and well known for its high QE when lighted with UV light. For improving the QE only caesium for activation is required.
At the moment GaN is used for photocathode-based detectors such as photomultipliers or phototubes and for LEDs. They have characteristics of low dark current, high-speed response and high sensitivity. It is very new for application in SRF Guns. It seems to be more robust and achieves higher QE than other photocathodes [1].
Crystallinity and surface parameters define the photoemission properties. Modern analytical methods are used for identification of impurities, dislocations and characterization of the crystallinity of the semiconductors and the right cleaning treatment as well as the right caesium rating.
[1] Uchiyama, Shoichi et al. 2011. “GaN-Based Photocathodes with Extremely High Quantum Efficiency” 103511(2005):1–4.

Keywords: gallium nitride; photocathode; SRF Gun

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Permalink: https://www.hzdr.de/publications/Publ-32928
Publ.-Id: 32928


DNA Based Formation of Nanodisc-Stacks

Subramanian, M.; Kielar, C.; Tsushima, S.; Fahmy, K.; Oertel, J.

We describe here the formation of multimers of membrane-scaffolding protein MSP1D1-bounded nanodiscs using the thiol reactivity of engineered cysteines. The mutated positions N42 and K163 in MSP1D1 were chosen to support chemical modification as evidenced by fluorescent labeling with pyrene. The direct disulphide bond formation of nanodiscs formed by the MSP1D1_N42C variant led to dimers and trimers with low yield. In contrast, transmission electron microscopy revealed that the attachment of oligonucleotides to the engineered cysteines of MSP1D1 allowed the growth of submicron-sized tracts of stacked nanodiscs through the hybridization of nanodisc populations carrying complementary strands and a flexible spacer.

Keywords: membrane-scaffolding protein; nanodisc; membrane protein; lipid bilayer; lipid protein interaction; multimerization; self-assembly; bionanotechnology

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Permalink: https://www.hzdr.de/publications/Publ-32927
Publ.-Id: 32927


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