Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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39005 Publications

Strained GaAs nanowires with high electron mobility on Si substrates

Balaghi, L.; Shan, S.; Fotev, I.; Moebus, F.; Rana, R.; Venanzi, T.; Hübner, R.; Mikolajick, T.; Schneider, H.; Helm, M.; Pashkin, O.; Dimakis, E.

Novel transistor concepts based on semiconductor nanowires promise high performance, lower energy consumption and better integrability in various platforms in nanoscale dimensions. Concerning the intrinsic transport properties of electrons in nanowires, relatively high mobility values that approach those in bulk crystals have been obtained only in core/shell heterostructures, where electrons are confined inside the core and, thus, their scattering on the nanowire surface is suppressed.
Here, we demonstrate that the large strain in core/shell nanowires with significant lattice-mismatch between the core and the shell can affect the effective mass and the scattering of electrons in a way that boosts their mobility to higher levels compared to results obtained by any other means. Specifically, we use GaAs/InAlAs core/shell nanowires with a lattice mismatch in the range of 3%, grown on Si substrates by molecular beam epitaxy. Overgrown with an 80-nm-thick shell, the 22-nm-thick core is hydrostatically tensile-strained as found by both Raman scattering and photoluminescence measurements [1, 2]. The transport properties and dynamics of electrons were probed at room temperature by optical-pump THz-probe spectroscopy, which is an established contactless method that circumvents challenges in the fabrication of electrical contacts on nanowires. We found that the mobility of electrons inside the strained GaAs core undergoes a remarkable enhancement despite the small core thickness, becoming 30 – 50 % higher than in unstrained GaAs/AlGaAs nanowires or bulk GaAs [2]. Our studies are extended to modulation-doped GaAs/InAlAs nanowires and the results will be presented.
The reported strain-induced mobility enhancement is of major importance for the realization of transistors with high speed and low power consumption, having the potential to trigger major advancements in high-performance nanowire electronic devices monolithically integrated in Si platforms.

[1] L. Balaghi, G. Bussone, R. Grifone, R. Hübner, J. Grenzer, M. Ghorbani-Asl, A. V. Krasheninnikov, H. Schneider, M. Helm, E. Dimakis, Nat Commun 10, 2793 (2019).
[2] L. Balaghi, S. Shan, I. Fotev, F. Moebus, R. Rana, T. Venanzi, R. Hübner, T. Mikolajick, H. Schneider, M. Helm, A. Pashkin, E. Dimakis, Nat Commun 12, 6642 (2021).

Related publications

  • Lecture (Conference)
    19th Conference on Gettering and Defect Engineering in Semiconductor Technology, 10.09.2022, Mondsee, Austria

Permalink: https://www.hzdr.de/publications/Publ-36089
Publ.-Id: 36089


Overview on in vitro experiment possibilities and Flash experiments

Beyreuther, E.

Overview on in vitro experiment possibilities and Flash experiments

  • Lecture (Conference) (Online presentation)
    NIRO - DD Seminar on Pre-clinical Research in Proton Therapy, 07.03.2022, Zoom, Deutschand & Norwegen

Permalink: https://www.hzdr.de/publications/Publ-36088
Publ.-Id: 36088


Preclinical studies on proton Flash-RT

Beyreuther, E.

Overview over preclinical proton flash experiments

  • Invited lecture (Conferences)
    Bergen Proton Research Seminar, 21.11.2022, Bergen, Norway

Permalink: https://www.hzdr.de/publications/Publ-36087
Publ.-Id: 36087


Effects of beam pulse structure on oxygen depletion and radical production at ultra-hig dose rates and implications for the flash effect in zebrafish embryo

Jansen, J.; Beyreuther, E.; García-Calderón, D.; Karsch, L.; Knoll, J.; Pawelke, J.; Schürer, M.; Seco, J.

Background and Aims

A prominent explanation of the FLASH effect is the oxygen depletion hypothesis, in which the radiolysis of water or cytoplasm produces radicals that react with the O2 dissolved in the water or cytoplasm. This would result in an oxygen depletion leading to a hypoxic target and hence radiation protection effect based on the Oxygen Enhancement Ratio. The presented study aims to investigate the impact of beam pulse structure on oxygen depletion and its correlation with biological endpoints.
Methods

O2 depletion was measured using 30 MeV electron irradiation on a sealed water target. Read-out was performed using TROXSP5 sensors. The beam pulse structure was altered to assess 4 different regimes of average and beam pulse dose rate.
At clinical doses, not enough O2 was consumed to explain a FLASH effect due to radiation-induced hypoxia. The amount of O2 depleted per dose depends on the dose rate, and slightly less O2 is removed at higher dose rates, suggesting radical-radical reactions as a possible mechanism of the FLASH effect. Furthermore, our results regarding the pulse structures showed that the average dose rate seems to dominate the pulse dose rate in terms of radical production and O2 depletion. The direct comparison of the depletion measurements presented here with biological experiments on zebrafish embryos from another study also showed that there was a strong correlation between O2 depletion and biological radiation response (FIG 1). The results emphasize that the FLASH effect in biological tissues is likely to be explained by decreased effective radical production at high dose rates.
Conclusions

In the tested beam parameters, the mean dose rate has the most pronounced effect on O2 depletion. Depletion measurements showed a clear correlation with biological data, from which FLASH effects can be largely explained by changes in radical production.

  • Poster
    2nd Flash Radiotherapy and Particle Therapy Conference (FRPT 2022), 30.11.-02.12.2022, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-36086
Publ.-Id: 36086


Systematic proton Flash experiments with zebrafish embryo

Beyreuther, E.; Brack, F.-E.; Hans, S.; Horst, F. E.; Jansen, J.; Karsch, L.; Leßmann, E.; Löck, S.; Metzkes-Ng, J.; Pawelke, J.; Reimold, M.; Seco, J.; Schramm, U.; Szabo, R.; Zeil, K.

Background and Aims
The Flash effect, i.e. the radiobiological observation of normal tissue sparing but efficient tumor killing by
ultra-high dose rate (UHDR) irradiation, promise great benefits for cancer patient treatment. The translation
process of the Flash effect should be accompanied by systematic studies on the necessary beam parameters
for each clinical applied radiation. Using the zebrafish embryo model, the influence of partial oxygen level
(https://doi.org/10.1016/j.radonc.2021.02.003), electron pulse structure and dose were studied thoroughly.
To investigate a similar range of proton beam parameters UHDR experiments at different accelerators, but
under comparable conditions, are required.
Methods
To cover a broad range of proton dose rates, experiments have been prepared at the University Proton
Therapy Dresden (UPTD) and at the Draco laser accelerator (Helmholtz-Zentrum Dresden-Rossendorf)
providing quasi-continuous and single-shot proton beam delivery in the range of 0.12 to 10^9 Gy/s. To fulfil
the requirements of the model, i.e., irradiating a sufficiently high number of embryos at low oxygen level,
dedicated setups were established that also allow for the online measurement of oxygen partial pressure
and cope with the geometric restrictions of the respective accelerator.
Results
A comparison experiment at UPTD reveal a significant protecting Flash effect in both setups for zebrafish
embryo treated with 300 Gy/s relative to conventional proton dose rate. Moreover, a higher protection of
the embryos was indicated comparing the embryo length after irradiation with 10^9 Gy/s and conventional
proton dose rate, respectively.
Conclusions
Experimental setups have been established that allow for systematic proton dose rate studies using the
zebrafish embryo model at the clinical cyclotron of UPTD and at the Draco laser accelerator. Therewith, the
experimental possibilities at the Dresden platform for UHDR radiobiology are extended providing electron
and proton dose rates up to 10^9 Gy/s.

  • Poster
    2nd Flash Radiotherapy and Particle Therapy Conference (FRPT 2022), 30.11.-02.12.2022, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-36085
Publ.-Id: 36085


Unique Proton and Electron Flash Experiment Platform for Preclinical Studies

Beyreuther, E.

The recent rediscovery of the “Flash Effect” revived the interest in high and ultra-high dose-rate radiation
effects throughout the radiobiology community, promising protection of normal tissue, while simultaneously
not altering tumour control. Systematic preclinical studies at (modified) clinical accelerators resulted in a recipe
of necessary beam parameters for the induction of electron Flash effect (doi:10.3389/fonc.2019.01563), whereas
for protons the optimal parameter setting is still under investigation. Expanding the clinical parameter range
the “Dresden platform for high-dose rate radiobiology” enables electron and proton experiments with doserates
of up to 109 Gy/s and more flexible beam pulse structures.
For systematic studies of the available electron and proton beam parameters, the zebrafish embryo model was
irradiated under similar conditions at the different accelerators. The irradiation setup was adapted with respect
to model requirements, i.e. a certain partial oxygen pressure, and the respective beam parameters.
Making use of the flexible pulse structure of the research electron accelerator ELBE, the mean dose rate was
identified as the factor that defines the electron Flash effect with decreasing radiation damage for electron
mean dose rate from 0.1 to 10^5 Gy/s. To cover a similar range of dose rates for protons, irradiations at the
University Proton Therapy Dresden (UPTD) were combined with proton treatment at the laser proton
accelerator DRACO. In doing so, the effects of proton dose rates in the range of 0.1 to 10^9 Gy/s could be
investigated.
To sum up, using the zebrafish embryo model as showcase the possibilities of the “Dresden platform” were
demonstrated, which opens the possibility for systematic studies on the mechanisms of the Flash effect in
tissue, on physico-chemical or molecular level.

  • Invited lecture (Conferences)
    2nd Flash Radiotherapy and Particle Therapy Conference (FRPT 2022), 30.11.-02.12.2022, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-36084
Publ.-Id: 36084


The Need for a Research Room in a Proton Therapy Centre – Dresden perspective

Beyreuther, E.

The Need for a Research Room in a Proton Therapy Centre – Dresden perspective

  • Invited lecture (Conferences)
    Proton Therapy Knowledge Hub, 29.11.2022, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-36083
Publ.-Id: 36083


Beam pulse structure affects the magnitude of Flash effect in zebrafish embryo

Beyreuther, E.; Pawelke, J.; Brand, M.; Hans, S.; Hideghety, K.; Jansen, J.; Karsch, L.; Leßmann, E.; Löck, S.; Schürer, M.; Seco, J.; Szabo, E. R.; Schramm, U.

Purpose/Objective
In a previous experiment at the HZDR research electron accelerator ELBE high mean dose rates of 105 Gy/s in combination with partial oxygen pressure below 5 mmHg protect zebrafish embryo from radiation damage compared to continuous reference irradiation (mean dose rate of 0.11 Gy/s) and higher oxygen pressure (Pawelke et al. Radiother Oncol 2021). However, the influence of beam pulse structure on the radiation response remains unanswered and should be resolved in an upcoming experiment.
Material/Methods
In addition to the Flash and the reference regime, the ELBE accelerator was used to mimic the pulse structure of a clinical electron linac delivering a dose of 28 Gy by 5 pulses at a frequency of 250 Hz. For comparison, a fourth regime of similar mean dose rate, but continuous beam (280 Gy/s) mimicking FLASH irradiation at a isochronous proton cyclotron (Beyreuther et al. Radiother Oncol 2019) was applied. Wild type zebrafish embryo (24 hpf) were irradiated and the radiation induced malformation were studied during the four day follow up for all four regimes. Zebrafish embryo irradiation was performed under low oxygen pressure and the depletion of depletion during irradiation was measured online.
Results
Compared to the reference regime a protecting Flash effect was found the three other pulse regimes for endpoints, except embryo survival. Analysing the radiation induced malformation more detailed significant correlations to mean and pulse dose rate are revealed. Surprisingly, the beam delivery in macro pulses (Linac regime) reduces the Flash effect relative to delivery at the same pulse dose rate but in a single pulse.
Conclusion.
The ELBE electron accelerator can be applied to study the influence of beam dose rate and pulse structure on the Flash effect by varying both parameters over several orders of magnitude. Hence, ELBE is an ideal tool for systematic studies on optimal electron beam parameters for Flash, including pulse structures that are relevant for clinical application.

  • Lecture (Conference)
    ESTRO 2022, 06.-10.05.2022, Copenhagen, Denmark
  • Abstract in refereed journal
    Radiotherapy and Oncology 170(2022), S69-S70

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  • Secondary publication expected from 31.05.2023

Permalink: https://www.hzdr.de/publications/Publ-36082
Publ.-Id: 36082


Ultra-high dose rate radiobiology at the "Dresden platform for high dose-rate radiobiology"

Beyreuther, E.

Ultra-high dose rate radiobiology at the "Dresden platform for high dose-rate radiobiology"

  • Lecture (others)
    HZDR ELI Beamlines Workshop, 31.05.2022, Prague, Czech

Permalink: https://www.hzdr.de/publications/Publ-36081
Publ.-Id: 36081


Aus Sicht der Akademie: Translational Radiopharmaceutical Research Beyond Vision

Kopka, K.

kein Abstrakt verfügbar

  • Invited lecture (Conferences)
    NuklearMedizin 2022 - Vorkongress-Symposium „Beyond Vision – quo vadis", 27.-30.04.2022, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36080
Publ.-Id: 36080


Gezielte Bekämpfung von Prostatakrebs

Kopka, K.

kein Abstrakt verfügbar

  • Invited lecture (Conferences)
    8. Jahrestreffen der Seniorexperten Chemie (GDCh), 02.-04.05.2022, Wernigerode, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36078
Publ.-Id: 36078


Exotic Cores with and without Dark-Matter Admixtures in Compact Stars

Zöllner, R.; Kämpfer, B.

We parameterize the core of compact spherical star configurations
by a mass ($m_x$) and a radius ($r_x$)
and study the resulting admissible areas in the total-mass -- total-radius plane.
The employed fiducial equation-of-state models of the corona at radii $r \ge r_x$ and
pressures $p \le p_x = p(r = r_x)$ are that (i) of constant sound velocity and (ii)
a proxy of DY$\Delta$ DD-ME2 provided by Buchdahl's exactly solvable ansatz.
The core ($r < r_x$) may contain any type of material,
e.g.\ Standard-Model matter with unspecified equation of state or/and
an unspecified Dark-Matter admixture.
Employing a toy model for the cool equation of state with first-order phase transition
we discuss also the mass-radius relation of compact stars with an admixture of Dark Matter
in a Mirror-World scenario.

Keywords: compact stars; core-corona decomposition; Dark-Matter admixture

Permalink: https://www.hzdr.de/publications/Publ-36077
Publ.-Id: 36077


Can we offer the right basic radiopharmaceutical research tool box for next generation clinical theranostics?

Kopka, K.

kein Abstrakt verfügbar

  • Invited lecture (Conferences)
    6th Theranostics World Congress, 24.-26.06.2022, Wiesbaden, D

Permalink: https://www.hzdr.de/publications/Publ-36076
Publ.-Id: 36076


Can we consolidate Radionuclide Theranostics through Applied Radiopharmaceutical Sciences?

Kopka, K.

kein Abstrakt verfügbar

  • Invited lecture (Conferences) (Online presentation)
    61st Annual Meeting of the Korean Society of Nuclear Medicine, 04.-05.11.2022, Ilsan, Korea

Permalink: https://www.hzdr.de/publications/Publ-36075
Publ.-Id: 36075


Sensitization of Patient-Derived Colorectal Cancer Organoids to Photon and Proton Radiation by Targeting DNA Damage Response Mechanisms

Pape, K.; Lößner, A.; William, D.; Czempiel, T.; Beyreuther, E.; Klimova, A.; Lehmann, C.; Schmäche, T.; Merker, S. R.; Naumann, M.; Ada, A.; Baenke, F.; Seidlitz, T.; Bütof, R.; Dietrich, A.; Krause, M.; Weitz, J.; Klink, B.; von Neubeck, C.; Stange, D. E.

Pathological complete response (pCR) has been correlated with overall survival in several
cancer entities including colorectal cancer. Novel total neoadjuvant treatment (TNT) in rectal cancer
has achieved pathological complete response in one‐third of the patients. To define better treatment
options for nonresponding patients, we used patient‐derived organoids (PDOs) as avatars of the
patient´s tumor to apply both photon‐ and proton‐based irradiation as well as single and combined
chemo(radio)therapeutic treatments. While response to photon and proton therapy was similar,
PDOs revealed heterogeneous responses to irradiation and different chemotherapeutic drugs.
Radiotherapeutic response of the PDOs was significantly correlated with their ability to repair
irradiation‐induced DNA damage. The classical combination of 5‐FU and irradiation could not
sensitize radioresistant tumor cells. Ataxia‐telangiectasia mutated (ATM) kinase was activated
upon radiation, and by inhibition of this central sensor of DNA damage, radioresistant PDOs were
resensitized. The study underlined the capability of PDOs to define nonresponders to irradiation
and could delineate therapeutic approaches for radioresistant patients.

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Permalink: https://www.hzdr.de/publications/Publ-36074
Publ.-Id: 36074


A Quantitative Assessment of Rubrics Using a Soft Computing Approach

Bhattacharyya, S.; De, S.; Mrsic, L.; Pan, I.; Muhammad, K.; Konar, D.

This study aims to elucidate a soft computing approach for quantitative assessment of the 1
scoring grade or rubrics for students in an outcome based education system. The intended approach 2
resorts to a fuzzy membership based assessment of the different parameters of the scoring system, 3
thereby yielding a novel and humanly assessment technique. The selection of the membership 4
functions is based on the human behavior so as to make a realistic representation of the scoring 5
strategy. The novelty of the proposed strategy lies in assigning fuzzy membership based weighted 6
scores instead of simply assigning score bands to rubric categories, as is performed in normal rubrics 7
based assessment. Comparative results demonstrated on a case study of Indian education scenario 8
reveal the effectiveness of the proposed strategy over other fuzzy membership and normal rubrics 9
based assessment procedures.

Keywords: OBTE; graduate attributes; rubrics; fuzzy sets

Permalink: https://www.hzdr.de/publications/Publ-36073
Publ.-Id: 36073


Performance Portability with alpaka

Stephan, J.; Bussmann, M.

The alpaka library is a header-only C++17 abstraction library for development across hardware accelerators (CPUs, GPUs, FPGAs). Its aim is to provide performance portability across accelerators through the abstraction (not hiding!) of the underlying levels of parallelism. In this poster we will show the concepts behind alpaka, how it is mapped to the various underlying hardware models, and show the features introduced over the last year. In addition, we will also present the software ecosystem surrounding alpaka.

Keywords: alpaka; C++; GPGPU; FPGA; performance portability; HPC

  • Open Access Logo Poster
    8. Annual MT Meeting, 26.-27.09.2022, Hamburg, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-36072
Publ.-Id: 36072


Performance Portability with alpaka

Stephan, J.; Bastrakov, S.; Di Pilato, A.; Ehrig, S.; Gruber, B. M.; Vyskocil, J.; Widera, R.; Bussmann, M.

The alpaka library is a header-only C++17 abstraction library for development across hardware accelerators (CPUs, GPUs, FPGAs). Its aim is to provide performance portability across accelerators through the abstraction (not hiding!) of the underlying levels of parallelism. In this talk we will show the concepts behind alpaka, how it is mapped to the various underlying hardware models, and show the features introduced over the last year. In addition, we will also (shortly) present the software ecosystem surrounding alpaka.

Keywords: alpaka; performance portability; GPGPU; C++; heterogeneous programming; software portability; parallel programming; CUDA; OpenMP; SYCL

  • Open Access Logo Poster
    21st International Workshop on Advanced Computing and Analysis Techniques in Physics Research (ACAT 2022), 23.-28.10.2022, Bari, Italia

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Permalink: https://www.hzdr.de/publications/Publ-36071
Publ.-Id: 36071


Mathematical Foundation for Quantum Computing

Konar, D.

This session was part of ISTE, IET and University of Mumbai approved one week Faculty Development Program on "Quantum Computing" which was conducted in hybrid mode from 12'h Dec 2022 to 17'h Dec 2022.

  • Lecture (others) (Online presentation)
    ISTE' IET and University of Mumbai approved one week Faculty Development Program (FDP) on "Quantum Computing", 12.-17.12.2022, Mumbai, India
  • Invited lecture (Conferences) (Online presentation)
    Faculty Development Program (FDP) on "Quantum Computing", 12.-17.12.2022, Mumbai, India

Permalink: https://www.hzdr.de/publications/Publ-36070
Publ.-Id: 36070


Parameterized Quantum Supervised Learning Classifiers

Konar, D.; Cangi, A.

Recent years witnessed various supervised learning frameworks relying on trainable quantum circuits as a result of advancement of quantum machine learning. The variational quantum classifier classifies data using a Variational Quantum Circuit (VQC) with an ansatz. The primary goal of the quantum supervised learning classifiers is to use the quantum feature map to transform data from distinct classes to different places in Hilbert space. However, it is not feasible to do feature selection beforehand, and for high-dimensional data using specific features to embed in the ansatz leads to data loss and error in classification. Hence, often data reduction technique like Shannon map is used on the data before uploading it to the quantum circuit. To obviate the data reduction before feeding to the circuit, dense parameterized quantum circuits with lesser number trainable parameters have been proposed without compromising the classification accuracy. The proposed quantum supervised learning framework is an improvement over established work on supervised quantum classifications. To show the effectiveness of the proposed densed quantum circuit, extensive experiments have been performed on IRIS data set and results show that it outperforms the previous quantum supervised classification frameworks in terms of classifications accuracy and complexity of the frameworks.

Keywords: Quantum computing; Quantum Machine Learning

  • Poster
    LEAPS meets Quantum Technology, 15.-20.05.2022, Elba Island, Italy

Permalink: https://www.hzdr.de/publications/Publ-36066
Publ.-Id: 36066


Coupled processes across a 10-year-old clayrock/concrete interface: results of a combined X-ray CT and PET transport experiment

Bernard, E.; Kulenkampff, J.; Jenni, A.; Mäder, U.

Interfaces between clay and cementitious materials are studied in the context of deep disposal of radioactive waste. Contrasting porewater chemistries lead to transport and chemical reactions that modify the pore network and affect transport. Research efforts were directed towards mineralogical and physical characterisation of interface regions (e.g. Mäder et al. 2017, Swiss J. Geosci. 110, 307) but little evidence exists on direct observations of transport behaviour across complex skins. We aim at providing evidence on how mineralogical-physical changes at such an interface affect transport of water and solutes, and linking mineralogical-physical characterisation.
A core was recovered at the Mont Terri rock laboratory (CI Experiment), containing a physically preserved interface between Opalinus Clay and Portland cement (PC) concrete reacted for 10 years. A long-term transport experiment was set up by injecting a synthetic claystone pore water into the core on the clay side, and forcing advection/diffusion across the interface and out of the cement side.
Before injection, the core was tomographed by X-ray CT; the clay part showed pre-existing bedding-parallel weak jointing and the PC concrete contains aggregates and gas pores. Figure 1 (left) shows the core skeleton during the infiltration, i.e. only the aggregates in the concrete and the dense Opalinus Clay.
A series of X-ray CT scans over time showed the change in porosity, while PET (positron emission tomography) directly images the mobile phase in 3D, and its penetration as a function of time (Kulenkampff et al., 2016, Solid Earth, 7, 1217). The sample was monitored frequently by high resolution X-ray CT during the first 4 months. 124I was used as PET tracer in the infiltrating synthetic claystone pore water, and the chosen dose allowed for continuous PET scanning during two weeks. Figure 1 (right) shows the flow observed by PET superimposed to the skeleton of the core. PET captured some preferential flow across claystone along some remaining joints, a large spreading of the tracer plume at the clay/cement interface, and some preferential flow across the PC.
The mineralogical and chemical changes coupled to the time-resolved 3D X-ray CT and PET scans (imaging both the stationary and the mobile phase) provide detailed information of coupled processes in complex porous media, e. g. how the dissolution of hydroxide cement phases and the precipitation of carbonates are influenced by advection/diffusion and vice versa.
Partial funding from the European Union's (Euratom) Horizon 2020 Programme under grant agreement 662147 – Cebama is acknowleged, and contributions by Nagra and the Mont Terri Consortium (CI Experiment) to Uni Bern.

Keywords: cement-clay interface; X-ray CT; PET; transport

  • Lecture (Conference)
    Clay Conference, 13.-16.06.2022, Nancy, France

Permalink: https://www.hzdr.de/publications/Publ-36062
Publ.-Id: 36062


Exploiting Heterogeneous Architectures: Applications and Lessons Learned

Stephan, J.

In this talk we show the benefits of using performance portability layers such as alpaka in real-world HPC applications. Using PIConGPU and the CMS Patatrack experiment as examples we demonstrate the minimal porting effort achieved by using alpaka when encountering new and previously unknown hardware architectures.

Keywords: PIConGPU; alpaka; cupla; heterogeneous architectures; heterogeneous systems; heterogeneous programming; C++; performance portability; software portability; HPC

  • Open Access Logo Lecture (others)
    Thirteenth INFN International School on: "Architectures, tools and methodologies for developing efficient large scale scientific computing applications" (ESC 2022), 03.-08.10.2022, Bertinoro, Italia

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Permalink: https://www.hzdr.de/publications/Publ-36061
Publ.-Id: 36061


Introduction to Software Portability Among Heterogeneous Architectures

Stephan, J.

In this talk we first introduce the concept of heterogeneous computing systems and then show the difficulties that lie in programming them. We present the different workload patterns that are suitable for different hardware types. In the end propose the alpaka kernel abstraction library as a possible solution to these challenges.

Keywords: heterogeneous systems; heterogeneous programming; software portability; performance portability; alpaka; C++; heterogeneous architectures; parallel programming; SYCL; Kokkos; RAJA; cupla; LLAMA; vikunja

  • Open Access Logo Lecture (others)
    Thirteenth INFN International School on: "Architectures, tools and methodologies for developing efficient large scale scientific computing applications" (ESC 2022), 03.-08.10.2022, Bertinoro, Italia

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Permalink: https://www.hzdr.de/publications/Publ-36060
Publ.-Id: 36060


Data Publication: Ab initio path integral Monte Carlo simulations of hydrogen snapshots at warm dense matter conditions

Böhme, M.; Dornheim, T.; Moldabekov, Z.; Vorberger, J.
Project Manager: Dornheim, Tobias; ResearchGroup: Moldabekov, Zhandos; RelatedPerson: Vorberger, Jan

This is the archived datasets used for the publication in the article: Ab initio path integral Monte Carlo simulations of hydrogen snapshots at warm dense matter conditions. The dataset also contains the data-analysis python scripts.

Keywords: Path-Integral Monte-Carlo; Warm Dense Hydrogen; Many-body physics

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-36059
Publ.-Id: 36059


The alpaka SYCL back-end

Stephan, J.

In this talk the kernel abstraction library alpaka is briefly introduced. Afterwards the technical details of the alpaka SYCL back-end are presented.

Keywords: alpaka; SYCL; heterogeneous programming; HPC; parallel programming

  • Open Access Logo Lecture (others) (Online presentation)
    Patatrack Students Meeting, 18.10.2022, Genf, Schweiz

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Permalink: https://www.hzdr.de/publications/Publ-36058
Publ.-Id: 36058


QED.jl - Strong-field particle physics code

Hernandez Acosta, U.; Steiniger, K.; Jungnickel, T.; Bussmann, M.

We present a novel approach for an event generator inherently using exact QED descriptions to predict the results of high-energy electron-photon scattering experiments that can be performed at modern X-ray free-electron laser facilities. Our event generator makes use of the fact, that the classical nonlinearity parameter barely approaches unity in high-frequency regimes accessible at these facilities, while this parameter range is outside of the application window of existing QED-PIC codes. This constraint on the parameter range allows for an approximation which is capable of taking the finite bandwidth of the X-ray laser into account in the description of the interaction.
We investigate the application of the new first-principle method to the generation of events in energy-driven electromagnetic cascades, which complements the studies on intensity-driven cascades at optical laser experiments.

  • Poster
    International Conference on Quantum Systems in Extreme Conditions (QSEC2022), 14.-18.11.2022, Bingen am Rhein, Germany

Permalink: https://www.hzdr.de/publications/Publ-36057
Publ.-Id: 36057


First steps in QED cascades - the onset stage

Hernandez Acosta, U.

While the high frequency of modern x-ray free-electron lasers has the benefit of requiring less energy of a seed electron for triggering the development of a QED cascade, the non-linearity parameter obeys a_0 < 1, in contrast to high-intensity optical lasers. Accordingly, we analyse the phenomenon of multi-photon effects in trident pair production in pulsed x-ray laser fields at such values of a_0. The impact of the energy spectrum and its temporal structure and the coherence of the laser field on the emergent particle distribution at the onset of further cascading is discussed. Besides the evolution of mean multiplicities in the course of an energy-powered cascade, we seek characteristic fluctuation patterns.

Keywords: Strong-field QED; Pair production; Electromagnetic cascades; Trident process

  • Invited lecture (Conferences)
    QED Laser Plasmas (qlasp22), 26.-30.09.2022, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36055
Publ.-Id: 36055


Event generation in Julia

Hernandez Acosta, U.

The accurate modelling of laser-matter interaction is a very challenging task. Especially, the generation of scattering events to mimic statistical particle distributions seen in experiments have demanding requirements on the computational methods and implementations. With this talk, we introduce the complicated structure of strong-field QED and formulate the fundamental building blocks for Monte-Carlo event generation using this theory, where a key feature is the dynamical coupling of the laser field to the scattering processes. This type of coupling can not be addressed with state-of-the-art event generators used to model processes from the standard model of particle physics. Therefore, we introduce a new implementation of e Monte-Carlo event generator, written in the Julia programming language. Furthermore, we introduce some key language features of Julia, which may come in handy for implementations of future event generators in general, where especially the capabilities of distributed computing will be highlighted.

Keywords: Laser-Matter interaction; Event generation; Julia programming language

  • Invited lecture (Conferences) (Online presentation)
    HSF Physics Generator WG meeting, 07.07.2022, virtuell, virtuell

Permalink: https://www.hzdr.de/publications/Publ-36054
Publ.-Id: 36054


Microstructuring YbRh₂Si₂ for resistance and noise measurements down to ultra-low temperatures

Steppke, A.; Hamann, S.; König, M.; Mackenzie, A. P.; Kliemt, K.; Krellner, C.; Kopp, M.; Lonsky, M.; Müller, J.; Levitin, L. V.; Saunders, J.; Brando, M.

The discovery of superconductivity in the quantum critical Kondo-lattice system YbRh₂Si₂ at an
extremely low temperature of 2 mK has inspired efforts to perform high-resolution electrical
resistivity measurements down to this temperature range in highly conductive materials. Here we
show that control over the sample geometry by microstructuring using focused-ion-beam
techniques allows to reach ultra-low temperatures and increase signal-to-noise ratios (SNRs)
tenfold, without adverse effects to sample quality. In five experiments we show four-terminal
sensing resistance and magnetoresistance measurements which exhibit sharp phase transitions at
the Néel temperature, and Shubnikov–de-Haas (SdH) oscillations between 13 T and 18 T where we
identified a new SdH frequency of 0.39 kT. The increased SNR allowed resistance fluctuation
(noise) spectroscopy that would not be possible for bulk crystals, and confirmed intrinsic 1/ f -type
fluctuations. Under controlled strain, two thin microstructured samples exhibited a large increase
of T̀N from 67 mK up to 188 mK while still showing clear signatures of the phase transition and
SdH oscillations. Superconducting quantum interference device-based thermal noise spectroscopy
measurements in a nuclear demagnetization refrigerator down to 0.95 mK, show a sharp
superconducting transition at T̀c = 1.2 mK. These experiments demonstrate microstructuring as a
powerful tool to investigate the resistance and the noise spectrum of highly conductive correlated
metals over wide temperature ranges.

Permalink: https://www.hzdr.de/publications/Publ-36051
Publ.-Id: 36051


Unconventional Spin State Driven Spontaneous Magnetization in a Praseodymium Iron Antimonide

Pabst, F.; Palazzese Di Basilio, S.; Seewald, F.; Yamamoto, S.; Gorbunov, D.; Chattopadhyay, S.; Herrmannsdörfer, T.; Ritter, C.; Finzel, K.; Doert, T.; Klauss, H.-H.; Wosnitza, J.; Ruck, M.

Consolidating a microscopic understanding of magnetic properties is crucial for a rational design of magnetic materials with tailored characteristics. The interplay of 3d and 4f magnetism in rare-earth transition metal antimonides is an ideal platform to search for such complex behavior. Here the synthesis, crystal growth, structure, and complex magnetic properties are reported of the new compound Pr3Fe3Sb7 as studied by magnetization and electrical transport measurements in static and pulsed magnetic fields up to 56 T, powder neutron diffraction, and Mößbauer spectroscopy. On cooling without external magnetic field, Pr3Fe3Sb shows spontaneous magnetization, indicating a symmetry breaking without a compensating domain structure. The Fe substructure exhibits noncollinear ferromagnetic order below the Curie temperature TC ≈ 380 K. Two spin orientations exist, which approximately align along the Fe–Fe bond directions, one parallel to the ab plane and a second one with the moments canting away from the c axis. The Pr substructure orders below 40 K, leading to a spin-reorientation transition (SRT) of the iron substructure. In low fields, the Fe and Pr magnetic moments order antiparallel to each other, which gives rise to a magnetization antiparallel to the external field. At 1.4 K, the magnetization approaches saturation above 40 T. The compound exhibits metallic resistivity along the c axis, with a small anomaly at the SRT.

Permalink: https://www.hzdr.de/publications/Publ-36050
Publ.-Id: 36050


Interparticle Charge-Transport-Enhanced Electrochemiluminescence of Quantum-Dot Aerogels

Gao, X.; Jiang, G.; Gao, C.; Prudnikau, A.; Hübner, R.; Zhan, J.; Zou, G.; Eychmüller, A.; Cai, B.

Electrochemiluminescence (ECL) represents a widely explored technique to generate light, in which the emission intensity relies critically on the charge-transfer reactions between electrogenerated radicals. Two types of charge-transfer mechanisms have been postulated for ECL generation, but the manipulation and effective probing of these routes remain a fundamental challenge. Here, we demonstrate the design of quantum dot (QD) aerogels as novel ECL luminophores via a versatile water-induced gelation strategy. The strong electronic coupling between adjacent QDs enables efficient charge transport within the aerogel network, leading to the generation of highly efficient ECL based on the selectively improved interparticle chargetransfer route. This mechanism is further verified by designing CdSe-CdTe mixed QD aerogels, where the two mechanistic routes are clearly decoupled for ECL generation. We anticipate our work will advance the fundamental understanding of ECL and prove useful for designing next-generation QD-based devices.

Related publications

  • Angewandte Chemie - International Edition 62(2023), e202214487
    Online First (2022) DOI: 10.1002/anie.202214487

Permalink: https://www.hzdr.de/publications/Publ-36048
Publ.-Id: 36048


Plastic instabilities in epitaxial NiMnGa Heusler films

Fareed, A.; Kar, S.; Fähler, S.; Maass, R.

Magnetic shape memory alloys are known to undergo stress- and temperature-driven phase changes. Here we study the specific case of a NiMnGa Heusler alloy that has an austenitic phase at room temperature. Upon cooling or the application of mechanical pressure, the austenite can transform into martensite, allowing for large reversible strain cycling and making such alloys to promising actuating materials. In order to shed more light on the mechanical switching behavior and possible dissipative processes, we probe the nano-scale plasticity of 0.5 and 2 µm thick epitaxial NiMnGa films with nanoindentation. A distinct pop-in signature is seen as the first departure from Hertzian elastic contact mechanics at small film thicknesses. This pop-in behavior persists across four orders of loading rates and over a broad temperature regime from 40°C to -30°C, which encompasses the transformation temperature to martensite. The statistics of the incipient plastic events are well described by a Weibull distribution. Atomic force microscopy reveals surface signatures around indents that indicate residual martensite, which is further confirmed with transmission electron microscopy imaging of the structure underneath indents. Instead of the expected modulated martensite (14M, 10M) that forms during a temperature-driven phase change, regions underneath indents contain non-modulated (NM) martensite. NM martensite exhibits a higher spontaneous strain and often forms at lower temperatures and higher strains. Therefore, it is concluded that the pop-in signature during nanoindentation originates from an athermal martensitic transformation, where the confinement effects result in huge and complex deformation inducing a partly irreversible transition to NM martensite.

Keywords: Magnetic Shape Memory Alloys; Nanoindentation

  • Lecture (Conference)
    Nanobrücken 2022: Nanomechanical Testing Conference, 08.-10.06.2022, Prague, Czech Republik

Permalink: https://www.hzdr.de/publications/Publ-36047
Publ.-Id: 36047


What is the speed limit of martensitic transformations?

Fähler, S.; Schwabe, S.; Lünser, K.; Schmidt, D.; Nielsch, K.; Gaal, P.

Structural martensitic transformations enable various applications, which range from high stroke actuation and sensing to energy efficient magnetocaloric refrigeration and thermomagnetic energy harvesting. All these emerging applications benefit from a fast transformation, but up to now the speed limit of martensitic transformations has not been explored. Here, we demonstrate that a martensite to austenite transformation can be completed in under ten nanoseconds. We heat an epitaxial Ni-Mn-Ga film with a laser pulse and use synchrotron diffraction to probe the influence of initial sample temperature and overheating on transformation rate and ratio. We demonstrate that an increase of thermal energy drives this transformation faster. Though the observed speed limit of 2.5 x 1027 (Js)-1 per unit cell leaves plenty of room for a further acceleration of applications, our analysis reveals that the practical limit will be the energy required for switching. Our experiments unveil that martensitic transformations obey similar speed limits as in microelectronics, which are expressed by the Margolus–Levitin theorem.
[1] S. Schwabe, K. Lünser, D. Schmidt, K. Nielsch, P. Gaal and S. Fähler, https://arxiv.org/abs/2202.12581

Keywords: Martensitic Transformations; Shape Memory Alloys

  • Invited lecture (Conferences)
    MSE2022, 27.-30.09.2022, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36046
Publ.-Id: 36046


Disentangling nanotwinned microstructures in Ni-Mn-based Heusler alloys from first-principles

Gruner, M. E.; Miroshkina, O. N.; Fähler, S.; Baigutlin, D.; Sokolovskiy, V. V.; Buchelnikov, V. D.

Depending on composition and chemical order, Ni-Mn-based Heusler alloys exhibit interesting functional properties, which render them useful for magnetic shape memory applications or as magnetocaloric materials. This is linked to the presence of hierarchically twinned modulated structures in martensite, which can be interpreted as adaptive, self-organized arrangement of [110]-aligned nanotwins consisting of non-modulated tetragonal building blocks as was shown previously for the paradigmatic case of stoichiometric Ni2MnGa [1]. A band-Jahn-Teller-type reconstruction of the Fermi surface which in particular softens the [110] transversal acoustic phonons leads to a downhill transformation path from cubic austenite to nanotwinned martensite [2]. The twin interfaces are subject to competing repulsive and attractive interactions related to the frustrated antiferromagnetic coupling between neighboring Mn atoms [3].
Based on recent first-principles calculations in the framework of density functional theory, the present contribution explores the signatures of the interdependence of magnetism, chemical order and nanotwinning in Ni-Mn-based Heusler systems beyond Ni-Mn-Ga and their relevance for the functional properties. Particular emphasis will be made on off-stoichiometric compositions suitable for magnetocaloric purposes.

Keywords: Magnetic Shape Memory Alloys; Martensite; Twinning; First Principle Calculations

  • Poster
    MSE 2022, 27.-30.09.2022, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36045
Publ.-Id: 36045


In situ stability study of WAlSiN based selective absorber under heating and cooling cycles in vacuum up to 800°C

Lungwitz, F.; Niranjan, K.; Munnik, F.; Hübner, R.; Garcia Valenzuela, A.; Escobar Galindo, R.; Krause, M.; Barshilia, H.

In situ measurements using RBS, ERD, and SE are less explored in characterizing solar absorber materials at high temperatures [1, 2]. In the present work, we report the W/WAlSiN/SiON/SiOO2 based spectrally selective solar absorber coating with excellent optical, compositional and structural properties at high temperatures [3, 4]. We have carried out in situ Rutherford backscattering spectrometry, elastic recoil detection and spectroscopic ellipsometry measurements at three different temperatures at 450°C, 650°C, and 800°C. An optical model describing perfectly the reflectance and ellipsometric data was developed. Further, the microstructural properties of the solar absorber coating are evaluated using cross-sectional transmission electron microscopy before and after annealing. Our data obtained before and after the heating experiments demonstrate excellent compositional, optical and structural stability of the coatings under the applied conditions. Furthermore, in situ ellipsometry showed the conservation of the optical properties of the W/WAlSiN/SiON/SiOO2 based spectrally selective solar absorber up to 800 °C, which is crucial for high-temperature applications.
[1] Ramón Escobar Galindo, Matthias Krause, K. Niranjan and Harish Barshilia, in Sustainable Material Solutions for Solar Energy Technologies (ed. Mariana Fraga, Delaina Amos, Savas Sonmezoglu, Velumani Subramaniam, Elsevier, 2021).
[2] Lungwitz, F. et al. Transparent conductive tantalum doped tin oxide as selectively solar-transmitting coating for high temperature solar thermal applications, Solar Energy Mater. Solar Cells 196, 84-93, doi:10.1016/j.solmat.2019.03.012 (2019).
[3] K. Niranjan, A. Soum-Glaude, A. Carling-Plaza, S. Bysakh, S. John, H.C. Barshilia, Extremely high temperature stable nanometric scale multilayer spectrally selective absorber coating: Emissivity measurements at elevated temperatures and a comprehensive study on ageing mechanism, Solar Energy Mater. Sol. Cells 221 (2021) 110905, doi:10.1016/j.solmat.2020.110905.
[4] K. Niranjan, A.C. Plaza, T. Grifo, M. Bordas, A. Soum-Glaude, H.C. Barshilia, Performance evaluation and durability studies of W/WAlSiN/SiON/SiOO2 based spectrally selective solar absorber coating for high-temperature applications: A comprehensive study on thermal and solar accelerated ageing, Solar Energy 227 (2021) 457–467, doi:10.1016/j.solener.2021.09.026.

Keywords: Concentrated solar power; high-temperature solar-selective coatings; nanolaminates; in situ analysis; ion beam analysis; STEM-EDXS imaging

Related publications

  • Poster
    PSE 2022 - 18th International Conference on Plasma Surface Engineering, 12.-15.09.2022, Erfurt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36044
Publ.-Id: 36044


A convolutional neural network for automated delineation and classification of metabolic tumor volume in head and neck cancer

Nikulin, P.; Hofheinz, F.; Maus, J.; Cegła, P.; Furth, C.; Kaźmierska, J.; Rogasch, J.; Hajiyianni, M.; Kotzerke, J.; Zschaeck, S.; van den Hoff, J.

Deep Learning based approaches for automated analysis of tomographic image data are drawing ever increasing attention in Radiology and Nuclear Medicine. With the advent of the new generation of PET scanners with massively enlarged axial field of view (“total body PET”) the importance of integrating such approaches into clinical workflows will further increase. In the present study we report on our application of a convolutional neural network (CNN) for automated survival analysis in head and neck cancer (HNC): PET parameters such as metabolic tumor volume (MTV), total lesion glycolysis, and asphericity of the primary tumor are known to be prognostic of clinical outcome in HNC patients. Additionally including evaluation of lymph node metastases further increases the prognostic value of PET. However, accurate manual delineation and classification of all lesions is time consuming and incompatible with clinical routine. Our goal, therefore, was development and evaluation of an automated tool for MTV delineation/classification of primary tumor and lymph node metastases in HNC in PET.

Automated delineation of the HNC cancer lesions was per- formed with a residual 3D U-Net convolutional neural network (CNN). 698 FDG PET/CT scans from 3 different sites and 4 public databases were used for network training and testing. In these data, primary tumor and metastases were manually delineated (with assistance of semi-automatic tools) and accordingly labeled by an experienced physician. Performance of the trained network models was assessed by 5-fold cross validation using the Dice similarity coefficient for individual delineation tasks.

Additionally, survival analysis using univariate Cox regression was performed. Delineation of all malignant lesions with the trained U-Net model achieves a Dice coefficient of 0.866 when not dis-
criminating between primary tumor and lymph nodes. Treating primary tumor and lymph node metastases as distinct classes yields Dice coefficients of 0.835 and 0.757 for the respective delin-
eations. The univariate Cox analysis reveals that, both, manually as well as automatically derived total MTVs are highly prognostic with similar hazard ratios (HR) with respect to overall survival
(HR=1.8; P<0.001 and HR=1.7; P<0.001, respectively). To the best of our knowledge, our work represents the first CNN model for successful MTV delineation and lesion classification in HNC. The network quickly performs usually satisfactory delineation and classification of primary tumor and lymph node metastases in HNC using FDG-PET data alone with only minimal sporadic manual corrections required. It is able to massively facilitate study data evaluation in large patient groups and also does have clear potential for clinical application.

  • Poster
    9th Conference on PET/MR and SPECT/MR & Total-Body PET Workshop, 28.05.-01.06.2022, Isola d'Elba, Italia

Permalink: https://www.hzdr.de/publications/Publ-36040
Publ.-Id: 36040


Experimental and Theoretical Analyses of Adiabatic Two-phase Flows in Horizontal Feed Pipes

Döß, A.

The majority of technical separation processes for fluid mixtures utilize the principle of rectification. If a two-phase mixture is fed into the column, possibly undesirable flow morphologies or severe droplet carry-over may occur, which detrimentally affect separation efficiency and equipment integrity. Currently, the two-phase flow behavior in feed pipes is hardly predicable and mostly based on empirical or heuristic methods, which do not properly account for a broad range of possible fluid properties and plant dimensions. As a consequence, costly safety margins are applied. Feed pipes to separation columns are often characterized by horizontal inlet nozzles, small length-to-diameter ratios and complex routing, involving elbows or bends. The pipe lengths are too short to enable the two-phase flow to fully develop, which thus, enters the column with unknown flow morphology. Since developing flows have rarely been studied, today’s engineering practice relies on existing predictive methods for fully developed two-phase flows. Graphical methods can hardly represent gradual transitions between flow regimes. Analytical models provide only simplified flow representations of the two-phase flow that have not yet been qualified for developing pipe flow. In this work, a comprehensive experimental database of horizontal water-air flows in two test sections with nominal pipe diameters of D = 50 mm and D = 200 mm and feed pipe lengths in the range 10 < L/D < 75 was established. This way, the data cover developing pipe flows with entrance lengths typical for two-phase feeds of separation columns and more developed flows that are comparable with the extensively studied reference system water-air. A particular focus was put on the effect of pipe bends on the flow morphology up- and downstream. The flow morphology was captured using imaging wire-mesh sensors. A 4D fuzzy algorithm was applied to objectively identify the flow two-phase morphologies. Based on their fuzzy representation, the flow morphologies were classified and a novel 2D visualization technique is proposed to discuss the flow development along the feed pipes. Undesired flow morphologies (intermittent flow and entrainment) during the operation of two-phase feeds are hardly predictable by conventional design tools. The inception of intermittent flows was analyzed using the experimental data. Consequently, the inception criteria based on the required liquid levels for fully developed intermittent flows were adapted for short entrance lengths. The characteristic dynamics of flow morphologies that are known to cause the onset of entrainment were analyzed. Based on wave frequencies, a predictive criterion for the susceptibility of wavy flows for the onset of entrainment is introduced and applied to straight feed pipes and horizontal 90° bends. Among the dozens available, 66 reduced-order models for the prediction of the void fraction were tested for straight feed pipes and horizontal 90° pipe bends. Thereof, the ones most suitable for variable operating conditions and pipe geometries were identified and adapted. Complementary 3D simulations were performed to verify the applicability of numerical codes (VoF, AIAD) for flows with free interfaces. The flow morphologies were successfully reproduced at macroscopic scale, however, the simulation results rank behind reduced-order models considering their quantitative predicting capabilities.

Keywords: Distillation; Two-phase feed; Flow morphology; Horizontal two-phase flow

  • Doctoral thesis
    TU Dresden, 2022
    PURL: https://nbn-resolving.org/urn:nbn:de:bsz:14-qucosa2-827786

Permalink: https://www.hzdr.de/publications/Publ-36039
Publ.-Id: 36039


Structural stability of transparent conductive oxide tantalum doped tin oxide during high-temperature treatment

Krause, M.; Hoppe, M.; Mendez, A.; Munnik, F.; Rodriguez Garcia, J.; Lungwitz, F.; Gemming, S.; Rafaja, D.; Escobar-Galindo, R.

The transparent conductive tantalum doped tin oxide is a potential candidate for applications in concentrated solar power technology, dye-sensitized solar cells and dynamic random access memories [1], [2], [3]. In all these fields, high-temperature stability in air is mandatory to preserve its functionality. In this work we demonstrate the compositional and structural in-air-stability of SnO2:Ta thin films at 650 °C and 800 °C for 12 hours. While the element composition and optical spectra were unchanged and the X-ray diffractograms revealed the conservation of a single-phase rutile-type crystal structure, some strong Raman lines of SnO2:Ta underwent substantial changes upon tempering. Quantum ab initio calculations of pristine and Ta-doped SnO2 with systematically varied point defects indicated that preferentially Sn vacancies and excess O atoms are responsible for these strong and unexpected Raman signatures. These defects are partially healed during high-temperature exposure, but that does not affect the functionality of SnO2:Ta as transparent conductor under these harsh conditions. This study provides a comprehensive understanding of crystal and defect structure of Ta-doped SnO2 prior to and after high temperature treatment in air for the first time and encourages its application in different fields where high-T stability, transparency and conductivity are required.
[1] F. Lungwitz et al., Transparent conductive tantalum doped tin oxide as selectively solar-transmitting coating for high temperature solar thermal applications, Solar Energy Mater. Solar Cells 199, 84 (2019), doi: 10.1016/j.solmat.2019.03.012
[2] R. Ramarajan, et al. Large-area spray deposited Ta-doped SnO2 thin film electrode for DSSC application, Solar Energy 211, 547-559 (2020), doi:10.1016/j.solener.2020.09.042.
[3] C. J. Cho, et al. Ta-Doped SnO2 as a reduction-resistant oxide electrode for DRAM capacitors, Journal of Materials Chemistry C 5, 9405-9411 (2017), doi:10.1039/c7tc03467a
Financial support by the EU, grant No. 645725, project FRIENDS2, is gratefully acknowledged.

Keywords: high-temperature materials; in-air stability; transparent conductive oxide; Ta-doped tin oxide; Raman signatures; point defects

Related publications

  • Lecture (Conference)
    PSE 2022 - 18th International Conference on Plasma Surface Engineering, 12.-15.09.2022, Erfurt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36038
Publ.-Id: 36038


A convolutional neural network for automated delineation and classification of metabolic tumor volume in head and neck cancer in FDG-PET/CT

Nikulin, P.; Hofheinz, F.; Maus, J.; Cegła, P.; Furth, C.; Kaźmierska, J.; Rogasch, J.; Kotzerke, J.; Zschaeck, S.; van den Hoff, J.

Aim: Image derived PET parameters such as metabolic tumor volume (MTV), total lesion glycolysis, and tumor asphericity of the primary tumor have been shown to be prognostic of clinical outcome of patients with head and neck cancer (HNC). Evaluation of lymph node metastases in addition to the primary tumor further increases the prognostic value of PET. Such analysis requires, however, accurate delineation and classification of all lesions which is very time-consuming when performed manually. The goal of this study is development of an automated tool for MTV delineation of primary tumor and lymph node metastases in HNC in PET/CT.

Methods: Automated delineation of the HNC cancer lesions was performed with a residual 3D U-Net convolutional neural network (CNN). 698 FDG PET/CT scans from 3 different sites and 4 public databases were used for network training (N=558) and testing (N=140). In these data, primary tumor and metastases were manually delineated and accordingly labeled by an experienced physician. This manual delineation served as the ground truth for network training. Performance of the trained network model was assessed in the test data using the Dice similarity coefficient for primary tumor, metastases, and the union of all lesions, respectively.

Results: The derived U-Net model is capable of accurate delineation of malignant lesions achieving a Dice coefficient of 0.847 for indiscriminative segmentation. Treating primary tumor and lymph node metastases as distinct classes yields Dice coefficients of 0.840 and 0.714 for the respective delineations.

Conclusions: In this work, we present the first CNN model for MTV delineation and classification in HNC. The developed network model allows to quickly perform satisfactory delineation of (and discrimination between) primary tumor and lymph node metastases in HNC with only minimal manual corrections possibly required. It thus is able to improve and to accelerate study data evaluation in quantitative PET and does also have potential for clinical application.

  • Lecture (Conference)
    NuklearMedizin 2022, 27.-30.04.2022, Leipzig, Deutschland
  • Contribution to proceedings
    NuklearMedizin 2022, 27.-30.04.2022, Leipzig, Deutschland
    A convolutional neural network for automated delineation and classification of metabolic tumor volume in head and neck cancer in FDG-PET/CT: Thieme
    DOI: 10.1055/s-0042-1745945

Permalink: https://www.hzdr.de/publications/Publ-36037
Publ.-Id: 36037


Advantages of Using Triboscopic Imaging: Case Studies on Carbon Coatings in Non-Lubricated Friction Conditions

Lorenz, L.; Makowski, S.; Weihnacht, V.; Krause, M.; Lasagni, A. F.

Triboscopy focuses on the analysis of the temporal evolution of a tribological system, combining local and time-resolved information, most commonly the evolution of friction. In this work, this technique is applied on measurements, which were carried out with a custom-built ultrahigh vacuum tribometer in ball-on-disc configuration. Based on these experiments, an extended classification to distinguish different triboscopic features is suggested, depending on the persistence in both track position and time: UNIFORM, GLOBAL, LOCAL, and SPORADIC. Further, a filter technique for quantifying triboscopic data regarding this classification is introduced. The new and improved triboscopic techniques are applied to various dry friction measurements of hydrogen-free carbon coatings under varying humidity and pressure. The resulting specific triboscopic features are correlated to wear phenomena, such as counter body coating abrasion, inhomogeneities in the wear track, non-uniform track wear, stick-slip and debris in the contact area, demonstrating the increased analysis and monitoring capabilities when compared to conventional friction curves and wear track images.

Keywords: DLC; ta-C; a-C; friction; wear

Related publications

Permalink: https://www.hzdr.de/publications/Publ-36035
Publ.-Id: 36035


Low-Friction of ta-C Coatings Paired with Brass and Other Materials under Vacuum and Atmospheric Conditions

Härtwig, F.; Lorenz, L.; Makowski, S.; Krause, M.; Habenicht, C.; Lasagni, A. F.

Vacuum environments provide challenging conditions for tribological systems. MoS2 is one of the materials commonly known to provide low friction for both ambient and vacuum conditions. However, it also exhibits poor wear resistance and low ability to withstand higher contact pressures. In search of wear-resistant alternatives, superhard hydrogen-free tetrahedral amorphous carbon coatings (ta-C) are explored in this study. Although known to have excellent friction and wear properties in ambient atmospheres, their vacuum performance is limited when self-paired and with steel. In this study, the influence of the paired material on the friction behavior of ta-C is studied using counterbodies made from brass, bronze, copper, silicon carbide, and aluminum oxide, as well as from steel and ta-C coatings as reference materials. Brass was found to be the most promising counterbody material and was further tested in direct comparison to steel, as well as in long-term performance experiments. It was shown that the brass/ta-C friction pair exhibits low friction (µ < 0.1) and high wear in the short term, irrespective of ambient pressure, whereas in the long term, the friction coefficient increases due to a change in the wear mechanism. Al2O3 was identified as another promising sliding partner against ta-C, with a higher friction coefficient than that of brass (µ = 0.3), but considerably lower wear. All other pairings exhibited high friction, high wear, or both.

Keywords: diamond-like coatings; wear; tribology; carbon; films

Related publications

Permalink: https://www.hzdr.de/publications/Publ-36034
Publ.-Id: 36034


Phase Transformation Induced by High Pressure Torsion in the High-Entropy Alloy CrMnFeCoNi

Chulist, R.; Pukenas, A.; Chekhonin, P.; Hohenwarter, A.; Pippan, R.; Schell, N.; Skrotzki, W.

The forward and reverse phase transformation from face-centered cubic (fcc) to hexagonal
close-packed (hcp) in the equiatomic high-entropy alloy (HEA) CrMnFeCoNi has been investigated
with diffraction of high-energy synchrotron radiation. The forward transformation has been induced
by high pressure torsion at room and liquid nitrogen temperature by applying different hydrostatic
pressures and large shear strains. The volume fraction of hcp phase has been determined by Rietveld
analysis after pressure release and heating-up to room temperature as a function of hydrostatic
pressure. It increases with pressure and decreasing temperature. Depending on temperature, a
certain pressure is necessary to induce the phase transformation. In addition, the onset pressure
depends on hydrostaticity; it is lowered by shear stresses. The reverse transformation evolves over
a long period of time at ambient conditions due to the destabilization of the hcp phase. The effect
of the phase transformation on the microstructure and texture development and corresponding
microhardness of the HEA at room temperature is demonstrated. The phase transformation leads
to an inhomogeneous microstructure, weakening of the shear texture, and a surprising hardness
anomaly. Reasons for the hardness anomaly are discussed in detail.

Keywords: high-entropy alloy; high-entropy alloy; high pressure torsion; microstructure; texture; phase transformation; strength

Permalink: https://www.hzdr.de/publications/Publ-36033
Publ.-Id: 36033


Generating synthetic shadowgrams with an in-situ plugin in PIConGPU

Carstens, F.-O.; Steiniger, K.; Pausch, R.; Schöbel, S.; Chang, Y.-Y.; Irman, A.; Schramm, U.; Debus, A.

Few-cycle shadowgraphy is a valuable diagnostic for laser-plasma accelerators for obtaining insight into the $\mu$m- and fs-scale relativistic plasma dynamics. To enhance the understanding of experimental shadowgrams, we developed a synthetic shadowgram diagnostic within the fully relativistic particle-in-cell code PIConGPU.
In the shadowgraphy diagnostic, the probe laser is propagated through the plasma using PIConGPU, and then extracted and propagated onto a virtual CCD using an in-situ plugin for PIConGPU based on Fourier optics. The in-situ approach circumvents performance limitations of a post-processing workflow, like storing and loading large output files that result from large-scale laser-plasma simulations.
This poster presents the in-situ plugin and first synthetic shadowgrams from laser wakefield accelerator simulations that are generated by the plugin.

Keywords: Shadowgraphy; Synthetic Diagnostics; In-Situ Plugin; PIConGPU; Laser-Electron Acceleration

  • Poster
    8. Annual MT Meeting, 26.-27.09.2022, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36032
Publ.-Id: 36032


Curvilinear magnetism: from fundamentals to applications

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics, superconductivity and magnetism [1,2]. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape of magnetic thin films and nanowires [2,3]. In this talk, we will address fundamentals of curvature-induced effects in magnetism and review current application scenarios. In particular, we will demonstrate that curvature allows tailoring fundamental anisotropic and chiral magnetic interactions [4] and enables fundamentally new non-local chiral symmetry breaking effect [5]. Application potential of geometrically curved magnetic architectures is currently being explored as mechanically reshapeable magnetic field sensors for automotive applications, memory, spin-wave filters, high-speed racetrack memory devices as well as on-skin interactive electronics relying on thin films [6,7] as well as printed magnetic composites [8,9].

[1] P. Gentile et al., Electronic materials with nanoscale curved geometries. Nature Electronics (Review) 5, 551 (2022).
[2] D. Makarov et al., New Dimension in Magnetism and Superconductivity: 3D and Curvilinear Nanoarchitectures. Advanced Materials (Review) 34, 2101758 (2022).
[3] D. Makarov et al., Curvilinear micromagnetism: from fundamentals to applications (Springer, Zurich, 2022).
[4] O. Volkov et al., Experimental observation of exchange-driven chiral effects in curvilinear magnetism. Physical Review Letters 123, 077201 (2019).
[5] D. D. Sheka et al., Nonlocal chiral symmetry breaking in curvilinear magnetic shells. Communications Physics 3, 128 (2020).
[6] J. Ge et al., A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).
[7] G. S. Canon Bermudez et al., Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics. Nature Electronics 1, 589 (2018).
[8] M. Ha et al., Printable and Stretchable Giant Magnetoresistive Sensors for Highly Compliant and Skin-Conformal Electronics. Advanced Materials 33, 2005521 (2021).
[9] R. Xu et al., Self-healable printed magnetic field sensors using alternating magnetic fields. Nature Communications 13, 6587 (2022).

Keywords: curvature effects in magnetism; curvilinear magnetism; printed electronics; human-machine interfaces

Related publications

  • Lecture (others)
    Seminar at the University of Kiel, 25.01.2023, Kiel, Germany

Permalink: https://www.hzdr.de/publications/Publ-36031
Publ.-Id: 36031


Pattering data from NPVE software for Helium Ion Microscopy (HIM) irradiation data

Hlawacek, G.; Fowley, C.; Kuria, J.
Project Member: Fowley, Ciaran; Project Member: Kurian, Jinu; Project Leader: Doudin, Bernard

Pattering data from NPVE software for Helium Ion Microscopy (HIM) irradiation data

Keywords: focused ion beam; helium ion microscopy; nanopatterning; magnetic

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-36030
Publ.-Id: 36030


Fungal bioleaching of metals from industrial wastes

Chakankar, M. V.

Industrial wastes and wastewaters are important secondary sources for many metals. Recovering these metals from such waste streams helps in resource recycling and reduce the environmental burden. Microbial technology offers an economical alternative to traditional metal recovery. Several bacterial and fungal species are reported for metal bioleaching from different industrial wastes. Use of fungi in bioleaching process offers a variety of advantages. The present study provides an overview of fundamental mechanisms of fungal bioleaching and methods used for the same. The case study of two different industrial wastes is also provided.

  • Invited lecture (Conferences) (Online presentation)
    Fungal Diversity and its novel applications, 09.04.2022, Pune, India

Permalink: https://www.hzdr.de/publications/Publ-36029
Publ.-Id: 36029


Metal recovery by bioionflotation using biosurfactants

Chakankar, M. V.; Pollmann, K.; Rudolph, M.

Metal recovery by bioionflotation using biosurfactants

  • Lecture (others) (Online presentation)
    UGC STRIDE Lecture Series- Advances in Life Science Research, 10.02.2022, Kolhapur, India

Permalink: https://www.hzdr.de/publications/Publ-36028
Publ.-Id: 36028


Curvilinear magnetism: fundamentals and applications

Makarov, D.

In this tutorial, we will review recent activities in the field of curvilinear magnetism. In particular, fundamental aspects on controling anisotropy and chiral responses via geometrical curvature will be discussed. Furthermore, activities on the realization and application scenarios of flexible, stretchable and printed magnetic field sensors will be presented.

Keywords: curvature effects in magnetism; curvilinear magnetism; printed electronics; human-machine interfaces; flexible magnetoelectronics

Related publications

  • Invited lecture (Conferences)
    IEEE Advances in Magnetics conference (AIM2023), 15.-18.01.2023, Moena, Italy

Permalink: https://www.hzdr.de/publications/Publ-36025
Publ.-Id: 36025


Small Molecule Radiotracers for PET Imaging of PD-L1 with Copper-64

Krutzek, F.; Donat, C.; Ullrich, M.; Kopka, K.; Stadlbauer, S.

The programmed cell death ligand (PD-L1) is expressed on a number of different tumor entities and inhibits the immune response through binding to PD-1 on T-cells. Immune checkpoint inhibitors (ICI) prevent this blockade and thus can reactivate an immune response. However, only about 30% of the patients respond to an ICI monotherapy. Therefore, clinicians are in need for a non-invasive PET/SPECT radioligand for patient stratification and therapy monitoring.

Based on the structures of non-peptidic PD-L1 inhibitors, six different radiotracers were synthesized and radiolabelled with [64Cu]Cu2+ (HZDR, 30 MeV TR-FLEX cyclotron). Binding affinities were determined on PC3 cells stably overexpressing hPD-L1. For in vivo studies, qualitative PET/CT imaging experiments (nanoSCAN PET/CT, Mediso) were performed in NMRI-FoxN1-nude mice bearing PC3-hPD-L1 and mock xenograted tumors.

Two PD-L1 inhibitors were modified with strongly water-soluble acid groups, hydrophilic linker units and a NODAGA-chelator resulting in six different radioligands. The log(D) values of the copper-64 labelled radiotracers were between –3.17 and –4.15 and binding affinities ranged between 80.5 and 533 nM. Depending on the number and the pattern of sulfonate and phosphonate groups, in vivo experiments showed drastically different pharmacokinetic profiles. The radiotracer with one sulfonate and phosphonate group and the most hydrophobic linker exhibited a short circulation time, renal clearance, good tumor uptake (SUVmax = 3.5) and a distinct contrast between the hPD-L1 and the mock tumor.

In conclusion one PD-L1 radiotracer showed a promising pharmacokinetic profile, which is currently further modified to improve the binding affinity and tumor uptake.

  • Lecture (Conference) (Online presentation)
    The 8th International Electronic Conference on Medicinal Chemistry, 01.-30.11.2022, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36024
Publ.-Id: 36024


Synthesis and Biological Evaluation of Chelator-Based Small Molecule PET-Radiotracers for Imaging of PD-L1

Krutzek, F.; Donat, C.; Ullrich, M.; Kopka, K.; Stadlbauer, S.

Aim:

The programmed cell death ligand 1 (PD-L1) is overexpressed by various cancers, resulting in a downregulation of the local immune response and therefore enabling further tumor growth.[1] Immune checkpoint inhibitors (ICIs) can reactivate the immune system, however, only 30% of the patients respond to an ICI monotherapy.[2] Since PD-L1 is heterogeneously expressed within and across tumor sites, there is an urgent clinical need for non-invasive diagnostic tools to support the therapeutic decision process. Small molecule-based radiotracers for noninvasive molecular PD-L1 imaging offer improved tissue penetration, fast blood clearance and low immunogenicity over radiolabeled antibodies.

Methods:

Based on a published small molecule PD-L1 inhibitor, 10 different radioligands were synthesized and radiolabeled with copper-64 (HZDR, 30 MeV TR-FLEX cyclotron). Binding affinities were determined on PC3 cells stably overexpressing human PD-L1. For in vivo evaluation, qualitative PET/CT imaging (nanoSCAN PET/CT, Mediso) was performed in NMRI-FoxN1-nude mice bearing PC3-hPD-L1 xenografted tumors.

Results:

Modification of the PD-L1 binding motif with strongly water-solubilizing sulfonate and phosphonate groups, different linker units and a NODAGA-chelator in 21-25 organic synthesis steps (12-13 longest linear sequence) yielded 10 different ligands [3]. The 64Cu-labelled radiotracers exhibited logD values between -3.17 and -4.15 for six ligands of the first series, with dissociation constants (Kd) between 80.5 and 532.8 nM, as determined by saturation binding assays. Depending on the number and pattern of sulfonate and phosphonate groups, the in vivo experiments showed drastically different pharmacokinetic profiles: Compounds bearing a less hydrophilic linker showed improved tumor uptake. Three sulfonates resulted in increased blood circulation times of up to 24 h due to albumin binding increased renal clearance but also low tumor uptake (SUVmax = 1.4). Substitution of one sulfonate with a phosphonate reduced the circulation time to two hours, however, accompanied by mainly hepatobiliary clearance. To achieve predominant renal clearance, a second series of four compounds bearing two phosphonate and one sulfonate groups in the solubilizer unit and larger halogens at the central aryl core for improved tumor uptake were synthesized and are currently tested in vivo.

Conclusion:

Sulfonate groups in the PD-L1 tracers increased circulation times along with renal clearance, while tracers with one phosphonate group reduced the blood circulation time but lead to a more hepatobiliary clearance. Structural modifications to increase the binding affinity and improve tumor uptake are currently ongoing.

References:

[1] M. A. Postow, M. K. Callahan, J. D. Wolchok, J. Clin. Oncol. 2015, 33, 1974-1982.
[2] S. L. Topalian, C. G. Drake, D. M. Pardoll, Cancer Cell 2015, 27, 450-461.
[3] Stadlbauer S., Krutzek F., Kopka K. EP21212444.0, December 6th 2021.

  • Lecture (Conference)
    20th European Symposium on Radiopharmacy and Radiopharmaceuticals, 24.-27.11.2022, Verona, Italia

Permalink: https://www.hzdr.de/publications/Publ-36023
Publ.-Id: 36023


Small Molecule-Based Radiotracers for PET Imaging of PD-L1 With Copper-64

Krutzek, F.; Donat, C.; Ullrich, M.; Kopka, K.; Stadlbauer, S.

Aim/Introduction
The programmed cell death ligand 1 (PD-L1) is expressed by several cancer types and leads to a downregulation of the local immune response, therefore enabling tumour cells to evade the immune response.[1] So-called immune checkpoint inhibitors (ICI) are able to reactivate the immune system, however, only 30% of the patients respond to an ICI monotherapy.[2] Since PD-L1 is heterogeneously expressed within and across tumour sites, there is an urgent clinical need for a diagnostic, non-invasive imaging probe to support therapy decision. Small molecule-based radiotracers for PD-L1 PET or SPECT imaging fulfil these requirements due to their fast clearance, low risk of side effects and highly sensitive imaging at the molecular level.[3]

Materials & Methods
Based on a published small molecule PD-L1 inhibitor, six different radioligands were synthesized and radiolabelled with copper-64 (HZDR, 30 MeV TR-FLEX cyclotron). Binding affinities were determined on PC3 cells stably overexpressing human PD-L1 which were kindly provided by the Department of Radioimmunology. For in vivo evaluation, qualitative PET/CT imaging experiments (nanoSCAN PET/CT scanner, Mediso) were performed in NMRI-FoxN1-nude mice bearing PC3-hPD-L1 xenografted tumours.

Results
We designed six radioligands by modifying the PD-L1 binding motif with strongly water-solubilizing sulfonate and phosphonate groups, hydrophilic linker units and a NODAGA-chelator in 21 – 25 organic synthesis steps (12-13 longest linear sequence).[4] The copper-64 labelled radiotracers exhibited log(D) values between –3.17 and –4.15. Binding affinities (Kd) were between 80.5 and 532.8 nmol/L. Depending on the number and pattern of sulfonate and phosphonate groups, the in vivo experiments showed drastically different pharmacokinetic profiles: The radiotracer containing three sulfonates showed long circulation times of 24 h due to albumin binding, renal clearance but low tumour uptake (SUVmax = 1.4). Substitution of one sulfonate with a phosphonate improved tumour uptake (SUVmax = 3.1), reduced the circulation time to two hours but showed a more hepatobiliary clearance. The less hydrophilic radiotracer in this series with a Kd of 82.4 ± 7.42 nM, bearing one sulfonate and one phosphonate showed the most favourable pharmacokinetic profile with a short circulation time, renal clearance and an increased tumour uptake (SUVmax = 3.5).

Conclusions
The radiotracer bearing one sulfonate and one phosphonate group exhibited the best pharmacokinetic profile. This radioligand will undergo further structural modifications to increase the binding affinity and improve the tumour uptake.

References
[1] M. A. Postow, M. K. Callahan, J. D. Wolchok, J. Clin. Oncol. 2015, 33, 1974-1982.
[2] S. L. Topalian, C. G. Drake, D. M. Pardoll, Cancer Cell 2015, 27, 450-461.
[3] S. Chatterjee, W. G. Lesniak, S. Nimmagadda., Mol. Imaging 2017, 16, 1-5.
[4] S. Stadlbauer, F. Krutzek, K. Kopka, EP21212444.0, 2021.

  • Lecture (Conference)
    35th Annual Congress of the European Association of Nuclear Medicine, 15.-19.10.2022, Barcelona, Espana

Permalink: https://www.hzdr.de/publications/Publ-36022
Publ.-Id: 36022


Small Molecule-Radioliganden für PET-Bildgebung von PD-L1 mit Kupfer-64

Krutzek, F.; Donat, C.; Ullrich, M.; Kopka, K.; Stadlbauer, S.

Ziel: Der Programmed Cell Death Ligand 1 (PD-L1) ist auf verschiedenen Tumorentitäten überexprimiert und hemmt die Immunantwort durch Bindung an PD-1 auf T-Zellen. Immuncheckpoint-Inhibitoren können diese Blockade aufbrechen und die Immunantwort reaktivieren. Da nur ca. 30% der Patienten auf eine solche Therapie ansprechen, besteht klinisch ein dringender Bedarf an einem nicht-invasiven PET/SPECT-Radioliganden, um die Ansprechrate der Patienten auf diese Therapie abzuschätzen.[1]

Methoden: Basierend auf den Strukturen von nicht-peptidischen PD-L1-Inhibitoren, wurden sechs verschiedene Radioliganden synthetisiert und mit [64Cu]Cu2+ markiert (HZDR, 30 MeV TR-FLEX-Zyklotron). Bindungsaffinitäten wurden auf stabil hPD-L1 überexprimierenden PC3 Zellen bestimmt. In vivo wurden qualitative PET/CT-Bilder (nanoSCAN PET/CT, Mediso) an NMRI-FoxN1-Nacktmäusen mit PC3-hPD-L1- und mock-Tumoren aufgenommen.

Ergebnisse:

Zwei PD-L1-Inhibitoren wurden synthetisch mit stark wasserlöslichen Säuregruppen, hydrophilen Linkern und NODAGA modifiziert (Abb. 1a).[2] Die LogD7.4-Werte der [64Cu]Cu-Radioliganden lagen zwischen –3,17 und –4,15 und die Bindungsaffinitäten (KD) zwischen 80,5 und 532,8 nM. Abhängig von der Zahl und dem Substitutionsmuster der Sulfon- und Phosphonsäuregruppen, zeigte sich in vivo eine stark unterschiedliche Pharmakokinetik. Der Radioligand mit R1 = SO2Me, R2 = PO3H2 und n = 0 zeigte in vivo eine kurze Zirkulationszeit, renale Ausscheidung, gute Tumoraufnahme (SUVmax = 3.5) und einen deutlichen Kontrast zwischen hPD-L1- und mock-Tumor (Abb. 1b).
Schlussfolgerungen: Der PD-L1-Radioligand mit je einer Sulfon- und Phosphonsäuregruppe wies das beste pharmakokinetische Profil auf. Um die Bindungsaffinität und die Tumoraufnahme zu verbessern, wird das Leitmotiv derzeit weiter modifiziert.

Referenzen:

[1] Postow M. A., Callahan M. K., Wolchok J. D. J. Clin. Oncol. 2015, 33, 1974-1982.
[2] Stadlbauer S., Krutzek F., Kopka K. EP21212444.0, 2021.

  • Lecture (Conference)
    28. Jahrestagung der Arbeitsgemeinschaft Radiochemie / Radiopharmazie, 22.-24.09.2022, Wart, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36021
Publ.-Id: 36021


Detection schemes for quantum vacuum diffraction and birefringence

Ahmadiniaz, N.; Cowan, T.; Grenzer, J.; Franchino-Vinas, S.; Laso García, A.; Smid, M.; Toncian, T.; Trejo Espinosa, M. A.; Schützhold, R.

Motivated by recent experimental initiatives, such as at the
Helmholtz International Beamline for Extreme Fields (HIBEF)
at the European X-ray Free Electron Laser (XFEL), we calculate
the birefringent scattering of x-rays at the combined field of
two optical (or near-optical) lasers and compare various scenarios.
%
In order to facilitate an experimental detection of quantum vacuum diffraction and
birefringence, special emphasis is placed on scenarios where the initial
and final x-ray photons differ not just in polarization, but also in
propagation direction (corresponding to scattering angles in the mrad regime)
and possibly energy.

Keywords: Strong Field QED; Vacuum qirefringence; Quantum vacuum diffraction; Euler-Heisenberg Lagrangian; XFEL; Laser; Light-by-light scattering

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Permalink: https://www.hzdr.de/publications/Publ-36020
Publ.-Id: 36020


Resummed heat-kernel and form factors for surface contributions: Dirichlet semitransparent boundary conditions

Franchino-Vinas, S.

In this article we consider resummed expressions for the heat-kernel's
trace of a Laplace operator, the latter including a potential and imposing Dirichlet semitransparent boundary conditions on a surface of codimension one in flat space.
We obtain resummed expressions that correspond to the first and second order expansion of the heat-kernel in powers of the potential.
We show how to apply these results to obtain the bulk and surface form factors of a scalar quantum field theory in $d=4$ with a Yukawa coupling to a background.
A characterization of the form factors in terms of pseudo-differential operators is given.

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Permalink: https://www.hzdr.de/publications/Publ-36019
Publ.-Id: 36019


Geometrizing the Klein–Gordon and Dirac equations in Doubly Special Relativity

Franchino-Vinas, S.; Relancio, J. J.

In this work we discuss the deformed relativistic wave equations, namely the Klein--Gordon and Dirac equations in a Doubly Special Relativity scenario.
We employ what we call a geometric approach, based on the geometry of a curved momentum space, which should be seen as complementary to the more spread algebraic one.
In this frame we are able to rederive well-known algebraic expressions, as well as to treat yet unresolved issues, to wit, the explicit relation between both equations, the discrete symmetries for Dirac particles, the fate of covariance, and the formal definition of a Hilbert space for the Klein--Gordon case.

Keywords: Doubly Special Relativity; Klein-Gordon equation; Dirac equation; Curved momentum space

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Permalink: https://www.hzdr.de/publications/Publ-36017
Publ.-Id: 36017


Worldline instantons for the momentum spectrum of Schwinger pair production in space-time dependent fields

Degli Esposti, G.; Torgrimsson, G.

We show how to use the worldline-instanton formalism to calculate the momentum spectrum of the electron-positron pairs produced by an electric field that depends on both space and time. Using the LSZ reduction formula with a worldline representation for the propagator in a spacetime field, we make use of the saddle-point method to obtain a semiclassical approximation of the pair-production spectrum. In order to check the final result, we integrate the spectrum and compare with the results obtained using a previous instanton method for the imaginary part of the effective action.

Permalink: https://www.hzdr.de/publications/Publ-36015
Publ.-Id: 36015


Recovery of Release Cloud from Laser Shock-Loaded Graphite and Hydrocarbon Targets: In Search of Diamonds

Schuster, A. K.; Voigt, K.; Klemmed, B.; Hartley, N. J.; Lütgert, B. J.; Bähtz, C.; Benad, A.; Brabetz, C.; Cowan, T.; Doeppner, T.; Erb, D.; Eychmueller, A.; Facsko, S.; Falcone, R. W.; Fletcher, L. B.; Frydrych, S.; Ganzenmüller, G. C.; Gericke, D. O.; Glenzer, S. H.; Grenzer, J.; Helbig, U.; Hiermaier, S.; Hübner, R.; Laso García, A.; Lee, H. J.; Macdonald, M. J.; McBride, E. E.; Neumayer, P.; Pak, A.; Pelka, A.; Prencipe, I.; Prosvetov, A.; Rack, A.; Ravasio, A.; Redmer, R.; Reemts, D.; Rödel, M.; Schoelmerich, M.; Schumacher, D.; Tomut, M.; Turner, S. J.; Saunders, A. M.; Sun, P.; Vorberger, J.; Zettl, A.; Kraus, D.

This work presents first insights into the dynamics of free-surface release clouds from dynamically compressed polystyrene and pyrolytic graphite at pressures up to 200 GPa, where they transform into diamond or lonsdaleite, respectively. These ejecta clouds are released into either vacuum or various types of catcher systems, and are monitored with high-speed recordings (frame rates up to 10 MHz). Molecular dynamics simulations are used to give insights to the rate of diamond preservation throughout the free expansion and the catcher impact process, highlighting the challenges of diamond retrieval. Raman spectroscopy data show graphitic signatures on a catcher plate confirming that the shock-compressed PS is transformed. First electron microscopy analyses of solid catcher plates yield an outstanding number of different spherical-like objects in the size range between ten(s) up to hundreds of nanometres, which are one type of two potential diamond candidates identified. The origin of some objects can unambiguously be assigned, while the history of others remains speculative.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-36014
Publ.-Id: 36014


Integrated phycoremediation and ultrasonic-irradiation treatment (iPUT) for the enhanced removal of pharmaceutical contaminants in wastewater

Kurade, M. B.; Mustafa, G.; Zahid, M. T.; Awasthi, M. K.; Chakankar, M. V.; Pollmann, K.; Khan, M. A.; Park, Y. K.; Chang, S. W.; Chung, W.; Jeon, B.-H.

Ultrasonication using low frequencies of sound can increase cell organogenesis, which is beneficial for various industrial applications. This study demonstrates a novel approach of integrated phycoremediation and ultrasonication-irradiation treatment (iPUT) used for improving the degradation of sulfonamide antibiotics via a cumulative effect of combined treatments. Variable ultrasonication treatment (UT) (20 %-2 min to 40 %-10 min) was given to a model microalga, Chlamydomonas mexicana in two ways, 1) single ultrasonic treatment (SUT) and 2) multiple-intermittent ultrasonic treatments (IUT). The microalgal growth was slightly affected by SUT, while it significantly inhibited by IUT. The removal of sulfacetamide and sulfapyridine was significantly improved by >1.7-fold and >1.95-fold at 20 % of SUT and IUT treatment, respectively, compared to control. In the case of sulfamethazine, the SUT showed maximum removal (33.5 %) at 20 %, whereas IUT could achieve 27.5 % removal at the same ultrasonication conditions compared to 9.5 % removal in control. The IUT accelerated the degradation of sulfamethoxazole and sulfadimethoxine more than SUT showing a 9- fold and 12- fold increase in the removal of sulfamethoxazole and sulfadimethoxine with 20 % and 40 % treatments, respectively. The changes in microalgal cell morphology due to ultrasonication treatment were the main cause of enforced uptake and subsequent degradation of these ECs.

Keywords: phycoremediation

Permalink: https://www.hzdr.de/publications/Publ-36013
Publ.-Id: 36013


Carborane Analogues of Fenoprofen Exhibit Improved Antitumor Activity

Useini, L.; Mojić, M.; Laube, M.; Lönnecke, P.; Mijatović, S. S.; Maksimović-Ivanić, D.; Pietzsch, J.; Hey-Hawkins, E.

Fenoprofen is a widely used nonsteroidal anti-inflammatory drug (NSAID) against rheumatoid arthritis, degenerative joint disease, ankylosing spondylitis and gout. Like other NSAIDs, fenoprofen inhibits the synthesis of prostaglandins by blocking both cyclooxygenase (COX) isoforms, COX-1 the “house-keeping” enzyme and COX-2 the induced isoform from pathological stimuli. Unselective inhibition of both COX isoforms results in many side effects, but off-target effects have also been reported. The steric modifications of the drugs could afford the desired COX-2 selectivity. Furthermore, NSAIDs have shown promising cytotoxic properties. The structural modification of fenoprofen using bulky dicarba-closo-dodecaborane(12) (carborane) clusters and the biological evaluation of the carborane analogues for COX inhibition and antitumor potential showed that the carborane analogues exhibit stronger antitumor potential compared to their respective aryl-based compounds.

Permalink: https://www.hzdr.de/publications/Publ-36012
Publ.-Id: 36012


Investigating Brain Connectivity with Graph Neural Networks and GNNExplainer

Zhdanov, M.; Steinmann, S.; Hoffmann, N.

Functional connectivity plays an essential role in modern neuroscience. The modality sheds light on the brain's functional and structural aspects, including mechanisms behind multiple pathologies. One such pathology is schizophrenia which is often followed by auditory verbal hallucinations. The latter is commonly studied by observing functional connectivity during speech processing. In this work, we have made a step toward an in-depth examination of functional connectivity during a dichotic listening task via deep learning for three groups of people: schizophrenia patients with and without auditory verbal hallucinations and healthy controls. We propose a graph neural network-based framework within which we represent EEG data as signals in the graph domain. The framework allows one to 1) predict a brain mental disorder based on EEG recording, 2) differentiate the listening state from the resting state for each group and 3) recognize characteristic task-depending connectivity. Experimental results show that the proposed model can differentiate between the above groups with state-of-the-art performance. Besides, it provides a researcher with meaningful information regarding each group's functional connectivity, which we validated on the current domain knowledge.

Keywords: Graph neural networks; EEG; Functional connectivity

  • Open Access Logo Contribution to proceedings
    26th International Conference on Pattern Recognition (ICPR), 21.08.2022, Montreal, Canada
    DOI: 10.1109/ICPR56361.2022.9956201

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Permalink: https://www.hzdr.de/publications/Publ-36011
Publ.-Id: 36011


OPC UA Based User Data Interface at ELBE

Zenker, K.; Justus, M.; Steinbrück, R.

The Electron Linac for beams with high Brilliance and low Emittance (ELBE) at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) is operated using the SCADA system WinCC by Siemens. The majority of ELBE systems is connected to WinCC via industrial Ethernet and proprietary S7 communication. However, in recent years there was a demand to provide a more open and platform independent access to ELBE machine data. The Industry 4.0 standard OPC UA has been chosen to implement such an interface. We will show how we use OPC UA as a common communication layer between industrial and scientific instruments as well as proprietary and open source control system software. Our solution makes use of commercially available hard- and software, namely Simatic STEP7, Simatic WinCC v7.x by Siemens and IBH Link UA by IBHsoftec. Combining these products we designed an OPC UA based user data interface, which features encrypted communication and access control from the control room via WinCC. It is available for internal use, e.g. for feedbacks, and external use, e.g to log ELBE data along with experiment data or to provide data to ELBE operators for machine optimizations.

Keywords: OPC UA

Related publications

  • Poster
    13th International Workshop on Emerging Technologies and Scientific Facilities Controls, 04.-07.10.2022, Dolní Břežany/Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-36006
Publ.-Id: 36006


X-ray radiation transport in GPU accelerated Particle In Cell simulations

Ordyna, P.; Kluge, T.; Cowan, T.; Schramm, U.

Ultra-high-intensity laser pulse interactions with solid density targets are of central importance for
modern accelerator physics, Inertial Confinement Fusion(ICF) and astrophysics. In order to meet
the requirements of real-world applications, a deeper understanding of the underlying plasma
dynamics, including plasma instabilities and acceleration mechanisms, is needed. X-ray radiation
plays a substantial role in plasma physics, either as an integral part of a physical system itself or
as a useful diagnostic, hence it should be included in computational models.
Therefore, we bring a Monte Carlo based X-ray radiation transport module into our Particle In
Cell simulation framework PIConGPU. It allows, among others, for Thompson scattering, e.g. for
small-angle X-ray scattering (SAXS), and Faraday effect calculation for X-ray polarimetry - as
online, in-situ diagnostics.

  • Poster
    8. Annual MT Meeting, 26.-27.09.2022, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36005
Publ.-Id: 36005


NuScale SMR 3-D modelling and analysis of boron dilution with the system code ATHLET in the framework of McSAFER

Diaz Pescador, E.; Jobst, M.; Kliem, S.

The small modular reactor (SMR) NuScale is modelled by Helmholtz-Zentrum Dresden Rossendorf (HZDR) in the framework of the EU H2020 McSAFER. NuScale is a SMR of integral pressurized type operated with light water driven by natural circulation. This work summarizes the reactor modelling approach with the system code ATHLET and presents the results from a boron dilution sequence, based on the Design Certification Application (DCA). Steady-state and transient results show agreement, thereby demonstrating ATHLET strong simulation capabilities on complex transients applied to SMR designs. The results show a decrease in core nominal boron concentration and subsequent reactivity insertion by the boron feedback. The reactor is tripped upon “high pressurizer pressure” setpoint and the actuation of the DHRS leads to a long term safe shutdown condition.

  • Contribution to proceedings
    KERNTECHNIK 2022, 21.06.2022, Leipzig, Germany
  • Lecture (Conference)
    KERNTECHNIK 2022, 21.06.2022, Leipzig, Germany

Permalink: https://www.hzdr.de/publications/Publ-36003
Publ.-Id: 36003


NuScale SMR 3-D Modelling and Applied Safety Analyses with the System Code ATHLET in the Framework of the EU H2020 McSAFER

Diaz Pescador, E.; Jobst, M.; Kliem, S.

Research and development of small modular reactors (SMRs) is receiving increasing attention by several countries and organizations due to flexibility, cost reduction and advanced safety features. The SMR NuScale is modelled by Helmholtz-Zentrum Dresden Rossendorf (HZDR) in the framework of the EU H2020 McSAFER project. NuScale is a SMR of integral pressurized water reactor (PWR) type, operated with light water driven by natural circulation in all operation modes. This work summarizes the modelling approach of a thermohydraulic model of NuScale SMR with the system code ATHLET, that includes a state-of-the-art 3-D reactor pressure vessel (RPV). The paper presents results and discussion from a boron dilution sequence at hot full power based on the Design Certification Application (DCA) report. Simulation results show agreement at steady-state and transient calculation, thereby demonstrating ATHLET strong simulation capabilities on complex sequences in SMR designs. The results show a decrease in core nominal boron concentration and subsequent reactivity insertion by boron feedback. The reactor is tripped upon “high pressurizer pressure” function by the insertion of the control rod banks. The actuation of the decay heat removal system (DHRS) provides long term core cooling to bring the reactor to a safe shutdown condition and preservation of shutdown margin is met during the simulation thereby complying with acceptance criterion.

Keywords: NuScale; SMR; ATHLET; Boron Dilution; McSAFER

  • Contribution to proceedings
    13th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety, 06.09.2022, Hsinchu, Taiwan
  • Lecture (Conference) (Online presentation)
    13th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety, 06.09.2022, Hsinchu, Taiwan

Permalink: https://www.hzdr.de/publications/Publ-36001
Publ.-Id: 36001


Einsatz der FTC-Mini-Pilotanlage zur Optimierung von Flotationsprozessen Vorteile und Grenzen

Ben Said, B.; Pereira, L.; Rudolph, M.

Die Aufbereitung komplexer Erze durch neue Verfahren oder durch den Einsatz neuer oder ungewöhnlicher Reagenzien in der Flotation kann Probleme mit sich bringen. Insbesondere wenn neue Flotationsreagenzien verwendet werden oder ein kompliziertes Fließschema erforderlich ist, lassen sich die Auswirkungen auf den Betrieb anhand von Laborversuchen nicht ausreichend bestimmen. Es ist daher ratsam, Erze im kontinuierlichen Betrieb einer Pilotanlage zu untersuchen, bevor eine Aufbereitungsanlage im industriellen Maßstab installiert wird. Üblicherweise sind konventionelle Pilotanlagen, in denen 100 bis 1.000 kg/h Erzproben verarbeitet werden, eingesetzt, um die Machbarkeit des Verfahrens vor dem industriellen Maßstab zu belegen. Daraus ergeben sich detaillierte technische Daten, die für die Entwicklung eines endgültigen Prozessablaufs und die Dimensionierung der Ausrüstung erforderlich sind. Allerdings sind diese Pilotanlagen teuer in der Errichtung und im Betrieb. Als Alternative entwickelte das Falconbridge Technology Centre (FTC) 1999 in Zusammenarbeit mit Canadian Process Technologies Inc. eine Mini-Pilotanlage. Die FTC-Mini-Pilotanlage hat zunehmend an Bedeutung gewonnen, vor allem wegen der geringeren Probenmenge im Vergleich zur konventionellen Pilotanlage. In diesem Beitrag wird anhand der Ergebnisse der Batch-Flotation einer Fallstudie der Einsatz der FTC-Mini-Pilotanlage Optimierung des Flotationsprozesses von Scheelit unter Verwendung ein neuer Drücker aufgezeigt. Die Vorteile und Grenzen des Betriebs der Mini-Pilotanlage werden erörtert und die Ergebnisse im industriellen Maßstab validiert.

Keywords: Anlagenoptimierung; Flotationsprozess; Mineralienaufbereitung; Mini-Pilotanlage; Prozessoptimierung

  • Open Access Logo Lecture (Conference)
    Aufbereitung und Recycling 2022, 10.-11.11.2022, Freiberg, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-35996
Publ.-Id: 35996


Surrogate Modeling of Laser-Ion Acceleration in the Near-Critical Density Regime with Invertible Neural Networks

Miethlinger, T.; Garten, M.; Göthel, I.; Hoffmann, N.; Schramm, U.; Kluge, T.

The interaction of near-critical plasmas with ultra-intense laser pulses presents a promising approach to enable the development of very compact sources for high-energetic ions. However, current records for maximum proton energies are still below the required values for many applications, and challenges such as stability and spectral control remain unsolved to this day. In particular, significant effort per experiment and a high-dimensional design space renders naive sampling approaches ineffective. Furthermore, due to the strong nonlinearities of the underlying laser-plasma physics, synthetic observations by means of particle-in-cell (PIC) simulations are computationally very costly, and the maximum distance between two sampling points is strongly limited as well. Consequently, in order to build useful surrogate models for future data generation and experimental understanding and control, a combination of highly optimized simulation codes (we employ PIConGPU), powerful data-based methods, such as artificial neural networks, and modern sampling approaches are essential. Specifically, we employ invertible neural networks for bidirectional learning of parameter and observables, and autoencoder to reduce intermediate field data to a lower-dimensional latent representation.

Keywords: Invertible Neural Networks; Inverse Problems; Laser-Plasma; Laser-Ion Acceleration

  • Lecture (Conference) (Online presentation)
    DPG Spring Meeting Mainz 2022, 28.03.-01.04.2022, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35995
Publ.-Id: 35995


Surrogate Modeling of Laser-Plasma-Based Ion Acceleration with Invertible Neural Networks

Miethlinger, T.; Hoffmann, N.; Kluge, T.

The interaction of overdense and/or near-critical plasmas with ultra-intense laser pulses presents a promising approach to enable the development of very compact sources for high-energetic ions. However, current records for maximum proton energies are still below the required values for many applications, and challenges such as stability and spectral control remain unsolved to this day. In particular, significant effort per experiment and a high-dimensional design space renders naive sampling approaches ineffective. Furthermore, due to the strong nonlinearities of the underlying laser-plasma physics, synthetic observations by means of particle-in-cell (PIC) simulations are computationally very costly, and the maximum distance between two sampling points is strongly limited as well. Consequently, in order to build useful surrogate models for future data generation and experimental understanding and control, a combination of highly optimized simulation codes (we employ PIConGPU), powerful data-based methods, such as artificial neural networks, and modern sampling approaches are essential. Specifically, we employ invertible neural networks for bidirectional learning of parameter and observables, and autoencoder to reduce intermediate field data to a lower-dimensional latent representation.

Keywords: Invertible Neural Networks; Inverse Problems; Laser-Plasma; Laser-Ion Acceleration

  • Poster
    Platform for Advanced Scientific Computing 2022, 27.-29.06.2022, Basel, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-35994
Publ.-Id: 35994


Acceptance Rates of Invertible Neural Networks on Electron Spectra from Near-Critical Laser-Plasmas: A Comparison

Miethlinger, T.; Hoffmann, N.; Kluge, T.

While the interaction of ultra-intense ultra-short laser pulseswith near- and overcritical plasmas cannot be directly observed, experimentally accessible quantities (observables) often only indirectly giveinformation about the underlying plasma dynamics. Furthermore, theinformation provided by observables is incomplete, making the inverseproblem highly ambiguous. Therefore, in order to infer plasma dynamicsas well as experimental parameter, the full distribution over parameters given an observation needs to considered, requiring that models areflexible and account for the information lost in the forward process. Invertible Neural Networks (INNs) have been designed to efficiently modelboth the forward and inverse process, providing the full conditional posterior given a specific measurement. In this work, we benchmark INNsand standard statistical methods on synthetic electron spectra. First, weprovide experimental results with respect to the acceptance rate, whereour results show increases in acceptance rates up to a factor of 10. Additionally, we show that this increased acceptance rate also results in anincreased speed-up for INNs to the same extent. Lastly, we propose acomposite algorithm that utilizes INNs and promises low runtimes whilepreserving high accuracy.

Keywords: Invertible Neural Networks; Inverse Problems; Machine Learning; Particle-in-Cell; Laser-Plasma Physics

Permalink: https://www.hzdr.de/publications/Publ-35993
Publ.-Id: 35993


(Data set) Distinction of charge transfer and Frenkel excitons in pentacene traced via infrared spectroscopy

Pinteric, M.; Roh, S.; Hammer, S.; Pflaum, J.; Dressel, M.; Uykur, E.

  1. Data from the publication are given in Origin format with Figure codes.
  2. More data are available upon request.

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Permalink: https://www.hzdr.de/publications/Publ-35990
Publ.-Id: 35990


Distinction of charge transfer and Frenkel excitons in pentacene traced via infrared spectroscopy

Pinteric, M.; Roh, S.; Hammer, S.; Pflaum, J.; Dressel, M.; Uykur, E.

Infrared spectroscopy studies on pentacene single crystals have been performed in the frequency range of 12 meV to 3 eV in reflection and transmission configurations as a function of temperature, down to 10 K. Our results reveal the dominant contributions of the excitonic bands at the absorption edge. The singlet transitions of the Frenkel excitons at 1.78 eV with 130 meV Davydov splitting have been identified. An additional excitonic feature observed at 1.83 eV can be assigned to a charge-transfer type exciton evidenced by the strong vibrational anomalies. On the other hand, the strong feature seen at 1.67 eV does not couple to the vibrational modes suggests that electronic origin in nature.

Permalink: https://www.hzdr.de/publications/Publ-35989
Publ.-Id: 35989


(Data set)High-pressure investigations in CH3NH3PbX3 ( X = I, Br, and Cl): Suppression of ion migration and stabilization of low-temperature structure

Chan, Y. T.; Elliger, N.; Klis, B.; Kollar, M.; Horvath, E.; Forro, L.; Dressel, M.; Uykur, E.

The raw data can be obtained from the corresponding author
Martin Dressel: dressel@pi1.physik.uni-stuttgart.de

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Permalink: https://www.hzdr.de/publications/Publ-35988
Publ.-Id: 35988


Untersuchung zur Flotation von ultrafeinen Partikeln im neu entworfenen Trennapparat MultiDimFlot

Stefenelli, N.

Die Flotation ist ein Trennprozess, der in der Aufbereitung und Veredelung eines breiten Spektrums primärer Rohstoffe (Erze, Kohle, Karbonate etc.) sowie in diversen Recyclingprozessen eingesetzt wird [1]. Aufgrund des steigenden Bedarfs an Rohstoffen steht die Aufbereitungstechnik vor der Herausforderung fein- und feinstverwachsene Erze zu flotieren [2]. Daher ist es von großer Bedeutung die Grenzen der Flotierbarkeit in den ultrafeinen Bereich zu erweitern. Bei der Flotation handelt es sich um einen Nassprozess, dessen Trennprinzip auf der unterschiedlichen Benetzbarkeit der zu trennenden Feststoffpartikeln basiert. Hydrophobe Teilchen haften hierbei an eingebrachten Gasblasen und bilden Partikel-Blasen-Aggregate, die in der Suspension aufsteigen und einen Schaum bilden. Diese mit Wertstoff beladene Schaumschicht wird als Konzentrat von der Trübeoberfläche abgezogen. Die hydrophilen Partikel verbleiben hingegen in der Trübe [3]. In der Feinkornaufbereitung mit einem Partikelgrößenbereich von 10 μm bis 200 μm ist dieser Trennprozess weit verbreitet [4]. Die Flotation ultrafeiner Partikel mit einer Größe x < 10 μm stellt jedoch eine Vielzahl an verfahrenstechnischen Herausforderungen dar, sodass die herkömmlichen Flotationsapparate (mechanische Flotationsapparate, Flotationssäulen) entweder nicht oder nur ineffizient das hydrophile Gangmineral vom hydrophoben Wertstoff trennen. Im Rahmen des Projekts MultiDimFlot, welches Teil des DFG Schwerpunktprogramms 2045 MehrDimPart ist, wurde ein spezieller Trennapparat entwickelt, mit dem die Flotation ultrafeiner Partikel untersucht werden soll. Diese Apparatur kombiniert die Vorzüge des turbulenten Strömungsregimes in einer mechanischen Flotationszelle mit dem für die Flotationssäulen typischen tiefen Schaum. Die Flotierbarkeit eines binären Gemisches aus ultrafeinem Magnetit und Glaspartikel mit der MultiDimFlot-Apparatur wird im Zuge dieser Bachelor-Arbeit experimentell untersucht. Der Einfluss variierender Partikeleigenschaften auf den Flotationsprozess wird erforscht, weshalb Glaspartikel mit unterschiedlichen Partikelformen (Sphären, Fragmente und Fasern) und Hydrophobierungszuständen (nicht-, mäßig- und stark hydrophobiert) in Flotationsversuchen verwendet werden. Die experimentelle Arbeit umfasst drei Teile: Das Ziel des ersten Teils ist es, durch Variation der Parameter Rotordrehzahl und Luftzufuhr, geeignete Maschinen-parameter zur Flotation mäßig hydrophobierter, ultrafeiner Fragmente mit der MultiDimFlot-Apparatur zu finden. Im zweiten Teil wird mit den gewählten Betriebsparametern das Flotationsverhalten der übrigen Partikelsysteme untersucht. Der dritte Teil umfasst erste Testversuche zur Herstellung eines stationären Zustands und die Beprobung der Schaumsäule in unterschiedlichen Höhen.

  • Bachelor thesis
    TUBAF, 2022

Permalink: https://www.hzdr.de/publications/Publ-35987
Publ.-Id: 35987


Development of a system for the design and synthesis of tailor-made peptides for the treatment of polymers prior to plastic metallization

Kießlich, T.; Braun, R.; Lederer, F.; Pollmann, K.

Increasing demands in environmental protection and environmentally friendly solutions are important market drivers for the development of sustainable chemicals. Chromium (VI) is used in electroplating technology to pretreat polymers in order to achieve good metallization. However, it´s application requires special permits now. This is an EU strategy to prevent the use of dangerous and unhealthy Reduce substances. Finding replacements with conventional chemicals is increasingly difficult. In order to change the chemistry and microstructure of polymer surfaces at suitable temperatures and process times, very reactive chemicals are required, which pose a high risk. Currently available alternative Chromium (VI) -free technologies for polymer preconditioning have not yet been reach the industrial requirements.
One strategy to solve this problem is to focus on very specific and selective reactions. The main aim of this work is to develop a biological system that enables the development and synthesis of tailor-made, selective polymer-binding peptides. The system is based on what is known as phage surface display technology (PSD).
PSD generally uses a library of about 109 phages with various peptides fused to the phage coat proteins. All the phages in the library are unique. Phage particles are incubated with the target material (polymer) in three biopanning cycles. Only a few phages bind to surfaces and the unbound phage particles are removed when the target materials are washed. Finally, the attached phage particles were eluted and amplified in Escherichia coli cells. After the last cycle of biopanning, there are only a few individual phages left that have exceptionally high surface affinity. The phage particles are used for subsequent sequencing, modification and application. The peptides that are expressed by the selected phages are then characterized with regard to their sequence, their binding motif and their interaction with the target material.
.

  • Poster
    European Peptide Symposium, 29.08.-02.09.2022, Sitges, Spanien

Permalink: https://www.hzdr.de/publications/Publ-35984
Publ.-Id: 35984


Covid-19 Infections in Czechia

Abdussalam, W.

We provide post-processing data of daily infected COVID-19 cases for a municipality (Obec) level. The current data for municipality level is prepared on Czech_Obec_COVID19_Infections.csv. The file consists of five columns such as region, name, date, infected and population. The region denotes the ID of a county/state followed by its name in the next column. The inserted date of data is prepared in the third column followed by the number of dead and infected cases. Last but not least, the population of the county is provided in the last column.

This data hub was partially funded by the Where2Test project, which is financed by SMWK with tax funds on the basis of the budget approved by the Saxon State Parliament. This data hub was also partially funded by the Center of Advanced Systems Understanding (CASUS) which is financed by Germany’s Federal Ministry of Education and Research (BMBF) and by the Saxon Ministry for Science, Culture and Tourism (SMWK) with tax funds on the basis of the budget approved by the Saxon State Parliament.

Keywords: Covid-19; Czechia

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Permalink: https://www.hzdr.de/publications/Publ-35983
Publ.-Id: 35983


Seeded FEL lasing of the COXINEL beamline driven by the HZDR plasma accelerator

Labat, M.; Couperus Cabadağ, J. P.; Ghaith, A.; Irman, A.; Berlioux, A.; Berteaud, P.; Blache, F.; Bock, S.; Bouvet, F.; Briquez, F.; Chang, Y.-Y.; Corde, S.; Debus, A.; de Oliveira, C.; Duval, J.-P.; Dietrich, Y.; El Ajjouri, M.; Eisenmann, C.; Gautier, J.; Gebhardt, R.; Grams, S.; Helbig, U.; Herbeaux, C.; Hubert, N.; Kitegi, C.; Kononenko, O.; Kuntzsch, M.; La Berge, M.; Le, S.; Leluan, B.; Loulergue, A.; Malka, V.; Marteau, F.; Huy N. Guyen, M.; Oumbarek-Espinos, D.; Pausch, R.; Pereira, D.; Püschel, T.; Ricaud, J.-P.; Rommeluere, P.; Roussel, E.; Rousseau, P.; Schöbel, S.; Sebdaoui, M.; Steiniger, K.; Tavakoli, K.; Thaury, C.; Ufer, P.; Valleau, M.; Vandenberghe, M.; Veteran, J.; Schramm, U.; Couprie, M.-E.

Laser Plasma Accelerators (LPAs), harnessing gigavolt-per-centimeter accelerating fields, can generate high peak current, low emittance and GeV class electron beams paving the way for the realization of future compact free-electron lasers (FELs). Here, we report on the commissioning of the COXINEL beamline driven by the HZDR plasma accelerator and experimental demonstration of FEL lasing at 270 nm in a seeded configuration. Control over the radiation wavelength is achieved with an improved bandwidth stability. Furthermore, the appearance of interference fringes, resulting from the interaction between the phase-locked emitted radiation and the seed, confirms longitudinal coherence, representing a key feature of such a seeded FEL. These results are cross-checked with simulations, ELEGANT for beam optics and GENESIS for FEL radiation. We anticipate a navigable pathway toward smaller-scale free-electron lasers at extreme ultra-violet wavelengths.

Keywords: free electron laser; laser plasma accelerator; seeded FEL driven by LPA beams

  • Lecture (Conference)
    Advanced Accelerator Concepts (AAC), 06.-11.11.2022, Long Island, New York, USA
  • Invited lecture (Conferences)
    BLIN, 12.10.2022, Garching, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35982
Publ.-Id: 35982


Seeded free-electron laser driven by a compact laser plasma accelerator

Labat, M.; Couperus Cabadağ, J. P.; Ghaith, A.; Irman, A.; Berlioux, A.; Berteaud, P.; Blache, F.; Bock, S.; Bouvet, F.; Briquez, F.; Chang, Y.-Y.; Corde, S.; Debus, A.; de Oliveira, C.; Duval, J.-P.; Dietrich, Y.; El Ajjouri, M.; Eisenmann, C.; Gautier, J.; Gebhardt, R.; Grams, S.; Helbig, U.; Herbeaux, C.; Hubert, N.; Kitegi, C.; Kononenko, O.; Kuntzsch, M.; La Berge, M.; Le, S.; Leluan, B.; Loulergue, A.; Malka, V.; Marteau, F.; Huy N. Guyen, M.; Oumbarek-Espinos, D.; Pausch, R.; Pereira, D.; Püschel, T.; Ricaud, J.-P.; Rommeluere, P.; Roussel, E.; Rousseau, P.; Schöbel, S.; Sebdaoui, M.; Steiniger, K.; Tavakoli, K.; Thaury, C.; Ufer, P.; Valleau, M.; Vandenberghe, M.; Veteran, J.; Schramm, U.; Couprie, M.-E.

Seeded free-electron laser driven by a compact laser plasma accelerator
Free-electron lasers generate high-brilliance coherent radiation at
wavelengths spanning from the infrared to the X-ray domains. The recent
development of short-wavelength seeded free-electron lasers now allows
for unprecedented levels of control on longitudinal coherence, opening
new scientific avenues such as ultra-fast dynamics on complex systems
and X-ray nonlinear optics. Although those devices rely on state-of-the-art
large-scale accelerators, advancements on laser-plasma accelerators, which
harness gigavolt-per-centimetre accelerating fields, showcase a promising
technology as compact drivers for free-electron lasers. Using such
footprint-reduced accelerators, exponential amplification of a shot-noise
type of radiation in a self-amplified spontaneous emission configuration
was recently achieved. However, employing this compact approach for the
delivery of temporally coherent pulses in a controlled manner has remained
a major challenge. Here we present the experimental demonstration
of a laser-plasma accelerator-driven free-electron laser in a seeded
configuration, where control over the radiation wavelength is accomplished.
Furthermore, the appearance of interference fringes, resulting from the
interaction between the phase-locked emitted radiation and the seed,
confirms longitudinal coherence. Building on our scientific achievements,
we anticipate a navigable pathway to extreme-ultraviolet wavelengths,
paving the way towards smaller-scale free-electron lasers, unique tools for a
multitude of applications in industry, laboratories and universities.

Keywords: free electron laser; laser plasma accelerator; seeded FEL driven by LPA beams

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Permalink: https://www.hzdr.de/publications/Publ-35981
Publ.-Id: 35981


Stable and High-Quality Electron Beams from Staged Laser and Plasma Wakefield Accelerators

Foerster, F. M.; Döpp, A.; Haberstroh, F.; Grafenstein, K. V.; Campbell, D.; Chang, Y.-Y.; Corde, S.; Couperus Cabadağ, J. P.; Debus, A.; Gilljohann, M. F.; Habib, A. F.; Heinemann, T.; Hidding, B.; Irman, A.; Irshad, F.; Knetsch, A.; Kononenko, O.; Martinez De La Ossa, A.; Nutter, A.; Pausch, R.; Schilling, G.; Schletter, A.; Schöbel, S.; Schramm, U.; Travac, E.; Ufer, P.; Karsch, S.

We present experimental results on a plasma wakefield accelerator (PWFA) driven by high-current
electron beams from a laser wakefield accelerator (LWFA). In this staged setup stable and high-quality
(low-divergence and low energy spread) electron beams are generated at an optically generated hydro-
dynamic shock in the PWFA. The energy stability of the beams produced by that arrangement in the PWFA
stage is comparable to both single-stage laser accelerators and plasma wakefield accelerators driven by
conventional accelerators. Simulations support that the intrinsic insensitivity of PWFAs to driver energy
fluctuations can be exploited to overcome stability limitations of state-of-the-art laser wakefield
accelerators when adding a PWFA stage. Furthermore, we demonstrate the generation of electron bunches
with energy spread and divergence superior to single-stage LWFAs, resulting in bunches with dense phase
space and an angular-spectral charge density beyond the initial drive beam parameters. These results
unambiguously show that staged LWFA-PWFA can help to tailor the electron-beam quality for certain
applications and to reduce the influence of fluctuating laser drivers on the electron-beam stability. This
encourages further development of this new class of staged wakefield acceleration as a viable scheme
toward compact, high-quality electron beam sources.

Keywords: hybrid lwfa-pwfa

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Permalink: https://www.hzdr.de/publications/Publ-35980
Publ.-Id: 35980


Effects of rf current and bias-field direction on the transition from linear to nonlinear gyrotropic dynamics in magnetic vortex structures

Ramasubramanian, L.; Iurchuk, V.; Sorokin, S.; Hellwig, O.; Deac, A. M.

We present a frequency-domain study of the dynamic behavior of a magnetic vortex core within a single Permalloy disk by means of electrical detection and micromagnetic simulations. When exciting the vortex core dynamics in a nonlinear regime, the lineshape of the rectified dc signal reveals a resonance peak splitting which depends on the excitation amplitude. Using micromagnetic simulations, we show that at high excitation power the peak splitting originates from the nanosecond time scale quasiperiodic switching of the vortex core polarity. Using lock-in detection, the rectified voltage is integrated over a ms time scale, so that the net signal detected between the two resonant peaks for a given range of parameters cancels out. The results are in agreement with the reported effects of the in-plane static field magnitude on the gyration dynamics, and complement them by detailed analysis of the effects of the rf current amplitude and the azimuthal angle of the in-plane bias magnetic field. Systematic characterization shows that a transition from linear to nonlinear dynamical regime can be controlled by rf current as well as by varying the magnitude and the direction of the bias magnetic field.

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Permalink: https://www.hzdr.de/publications/Publ-35979
Publ.-Id: 35979


Theranostic platform technologies for therapy and imaging

Feldmann, A.

Theranostic platform technologies for therapy and imaging

Keywords: theranostic; CAR T cell therapy; antibody

  • Invited lecture (Conferences)
    I&I retreat 2022, 09.-10.06.2022, Bonn, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35978
Publ.-Id: 35978


Theranostic Antibody- and CAR-based Platform Technology for Therapy and Imaging

Feldmann, A.

Theranostic Antibody- and CAR-based Platform Technology for Therapy and Imaging

Keywords: bispecific antibody; CAR T cell therapy; theranostics; UniCAR; RevCAR

  • Invited lecture (Conferences)
    Antibody Technologies and Therapeutics Conference, 11.-14.09.2022, Prato, Italien

Permalink: https://www.hzdr.de/publications/Publ-35977
Publ.-Id: 35977


Adaptor UniCAR and RevCAR platforms for flexible, switchable and combinatorial tumor targeting

Feldmann, A.; Rodrigues Loureiro, L. R.; Kegler, A.; Arndt, C.; Mitwasi, N.; Bergmann, R.; Koristka, S.; Hoffmann, A.; González Soto, K. E.; Kittel-Boselli, E.; Bartsch, T.; Drewitz, L.; Berndt, N.; Fasslrinner, F.; Bornhäuser, M.; Bachmann, M.

Chimeric antigen receptor (CAR) T-cells show remarkable therapeutic effects especially in B-cell derived leukemias and lymphomas. However, clinical translation of such an innovative immunotherapeutic approach in highly heterogeneous hematological malignancies like acute myeloid leukemia (AML) or solid tumors is still challenging due to life-threatening side effects, immune escape and disease relapse. To overcome such major hurdles and to address the unmet need for further improvements in CAR therapy, we have established flexible, switchable and programmable adaptor CAR platform technologies named UniCAR and RevCAR. These modular strategies consist of T-cells engineered with adaptor CARs which are primarily inactive as they are incapable to recognize surface antigens. Universal adaptor CAR T-cells can be flexibly redirected to any tumor antigen and controlled by targeting modules (TMs) cross-linking adaptor CAR T- and tumor cells resulting in tumor cell lysis. As an advancement of UniCARs, RevCARs lack the extracellular antigen-binding moiety reducing the receptor size and facilitating the genetical modification of T-cells with several RevCARs possessing different specificity and functionality. Thus, the RevCAR platform enables combinatorial tumor targeting following Boolean logic gates. So far, we have successfully shown preclinical applicability of the UniCAR and RevCAR approaches to target hematological malignancies as well as solid tumors in a flexible and specific manner using tumor cell lines and patient-derived materials. Remarkably, efficiency and switchability of UniCAR T-cells were even proven for the first time in patients in a clinical phase I study. Furthermore, by targeting of two different tumor antigens, combinatorial OR and AND gate logic targeting according to the rules of Boolean algebra was accomplished using the RevCAR platform. These achievements have a high potential for an improved and personalized tumor immunotherapy.

Keywords: UniCAR; RevCAR; CAR T cell therapy; combinatorial tumor targeting

  • Invited lecture (Conferences)
    3rd International Conference on Lymphocyte Engineering, 31.03.-02.04.2022, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35976
Publ.-Id: 35976


Investigation of the ¹⁴N(p,γ)¹⁵O reaction and its impact on the CNO cycle

Frentz, B.; Aprahamian, A.; Boeltzig, A.; Borgwardt, T.; Clark, A. M.; Deboer, R. J.; Gilardy, G.; Görres, J.; Hanhardt, M.; Henderson, S. L.; Howard, K. B.; Kadlecek, T.; Liu, Q.; Macon, K. T.; Moylan, S.; Reingold, C. S.; Robertson, D.; Seymour, C.; Strauss, S. Y.; Strieder, F.; Vande Kolk, B.; Wiescher, M.

The CNO cycle is the main energy source in massive stars during their hydrogen burning phase, and, for our
sun, it contributes at the ≈1% level. As the ¹⁴N(p,γ)¹⁵O reaction is the slowest in the cycle, it determines the
CNO energy production rate and thus the CNO contribution to the solar neutrino flux. These CNO neutrinos are
produced primarily from the β decay of ¹⁵O and, to a lesser extent, from the decay of ¹³N. Solar CNO neutrinos
are challenging to detect, but they can provide independent new information on the metallicity of the solar core.
Recently, CNO neutrinos from ¹⁵O have been identified for the first time with the Borexino neutrino detector
at the INFN Gran Sasso underground laboratory. There are, however, still some considerable uncertainties in
the ¹⁴N(p,γ)¹⁵O reaction rate under solar temperature conditions. The low energy reaction data presented
here, measured at the CASPAR underground accelerator, aim at connecting existing measurements at higher
energies and attempts to shed light on the discrepancies between the various data sets, while moving towards a
better understanding of the ¹⁴N(p,γ)¹⁵O reaction cross section. The present measurements span proton energies
between 0.27 and 1.07 MeV, closing a critical gap in the existing data. A multichannel R-matrix analysis was
performed with the entire new and existing data sets and is used to extrapolate the astrophysical S factors of the
ground state and the 6.79 MeV transition to low energies. The extrapolations are found to be in agreement with
previous work, but find that the discrepancies between measured data and R-matrix fits, both past and present,
still exist. We examine the possible reasons for these discrepancies and thereby provide recommendations for
future studies.

Permalink: https://www.hzdr.de/publications/Publ-35974
Publ.-Id: 35974


Thermal neutron background at Laboratorio Subterráneo de Canfranc (LSC)

Plaza, J.; Martínez, T.; Bécares, V.; Cano-Ott, D.; Villamarín, D.; Pérez De Rada, A.; Mendoza, E.; Pesudo, V.; Santorelli, R.; Peña, C.; Balibrea-Correa, J.; Boeltzig, A.

The thermal neutron background at Laboratorio Subterráneo de Canfranc (LSC) has been determined using several ³He proportional counter detectors. Bare and Cd shielded counters were used in a series of long measurements. Pulse shape discrimination techniques were applied to discriminate between neutron and gamma signals as well as other intrinsic contributions. Montecarlo simulations allowed us to estimate the sensitivity of the detectors and calculate values for the background flux of thermal neutrons inside Hall-A of LSC. The obtained value is (3.5±0.8)×10⁻⁶ n/cm²s, and is within an order of magnitude compared to similar facilities.

Keywords: Underground neutron background; Thermal neutron flux; ³He proportional counter; Pulse shape discrimination

Permalink: https://www.hzdr.de/publications/Publ-35972
Publ.-Id: 35972


Exploring Stars in Underground Laboratories: Challenges and Solutions

Aliotta, M.; Boeltzig, A.; Depalo, R.; Gyürky, G.

For millennia, mankind has been fascinated by the marvel of the starry night sky. Yet, a proper scientific understanding of how stars form, shine, and die is a relatively recent achievement, made possible by the interplay of different disciplines as well as by significant technological, theoretical, and observational progress. We now know that stars are sustained by nuclear fusion reactions and are the furnaces where all chemical elements continue to be forged out of primordial hydrogen and helium. Studying these reactions in terrestrial laboratories presents serious challenges and often requires developing ingenious instrumentation and detection techniques. Here, we reveal how some of the major breakthroughs in our quest to unveil the inner workings of stars have come from the most unexpected of places: deep underground. As we celebrate 30 years of activity at the first underground laboratory for nuclear astrophysics, LUNA, we review some of the key milestones and anticipate future opportunities for further advances both at LUNA and at other underground laboratories worldwide.

Keywords: stellar evolution; nucleosynthesis; nuclear astrophysics experiments; background suppression underground

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Permalink: https://www.hzdr.de/publications/Publ-35971
Publ.-Id: 35971


Data publication: Towards High-Repetition Rate Petawatt Laser Experiments with Cryogenic Jets Using a Mechanical Chopper System

Rehwald, M.; Assenbaum, S.; Bernert, C.; Curry, C. B.; Gauthier, M.; Glenzer, S. H.; Göde, S.; Schoenwaelder, C.; Treffert, F.; Schramm, U.; Zeil, K.

Rohdaten und Ausgewertete Messungen, die in der Publikation dargestellt sind.

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Permalink: https://www.hzdr.de/publications/Publ-35970
Publ.-Id: 35970


PIConGPU: Scaling high-fidelity plasma simulations up to exascale compute systems and a view on recent applications

Debus, A.; Steiniger, K.; Bastrakov, S.; Bastrakova, K.; Bussmann, M.; Carstens, F.-O.; Chandrasekaran, S.; Garten, M.; Gruber, B. M.; Hernandez Arreguin, B.; Hübl, A.; Juckeland, G.; Kelling, J.; Lebedev, A.; Leinhauser, M.; Marre, B. E.; Meyer, F.; Ordyna, P.; Pausch, R.; Pöschel, F.; Rogers, D.; Schramm, U.; Sprenger, L.; Starke, S.; Thévenet, M.; Trojok, J.; Wang, M.; Widera, R.; Young, J.

PIConGPU’s latest release 0.6.0 in December 2021 brought a number of new features. Among these are an arbitrary-order Maxwell solver, the Higuera-Cary pusher, collisions, and incident field generation via the total field/scattered field technique enhancing its numerical stability and predictive capabilities.
Furthermore, there are various technical advances, most notably support of the HIP computational backend allowing to run on AMD GPUs. These advances are mainly driven by our participation in OLCF’s Frontier Center for Accelerated Application Readiness providing access to the hardware platform of the Frontier exascale supercomputer scheduled for deployment later this year. We show performance data and present recent applications of PIConGPU profiting from these developments. To these applications belongs the advanced laser-plasma accelerator scheme Traveling-wave electron acceleration (TWEAC), providing scalability to energies beyond 10 GeV while avoiding staging. We further present simulation campaigns modeling and delivering valuable insight into the micrometer and femtosecond plasma dynamics of existing experimental campaigns.

Keywords: PIConGPU; particle-in-cell code; TWEAC; Laser-plasma accelerator

  • Poster
    8. Annual MT meeting, 26.-27.9.2022, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35969
Publ.-Id: 35969


Towards High-Repetition Rate Petawatt Laser Experiments with Cryogenic Jets Using a Mechanical Chopper System

Rehwald, M.; Assenbaum, S.; Bernert, C.; Curry, C. B.; Gauthier, M.; Glenzer, S. H.; Göde, S.; Schoenwaelder, C.; Treffert, F.; Schramm, U.; Zeil, K.

Laser-plasma based ion accelerators require suitable high-repetition rate target systems that enable systematic studies at controlled plasma conditions and application-relevant particle flux. Self-refreshing, micrometer-sized cryogenic jets have proven to be an ideal target platform. Yet, operation of such systems in the harsh environmental conditions of high power laser induced plasma experiments have turned out to be challenging. Here we report on recent experiments deploying a cryogenic hydrogen jet as a source of pure proton beams generated with the PW-class ultrashort pulse laser DRACO. Damage to the jet target system during application of full energy laser shots was prevented by implementation of a mechanical chopper system interrupting the direct line of sight between the laser plasma interaction zone and the jet source.

Related publications

  • Open Access Logo Contribution to proceedings
    13th Int. Particle Acc. Conf. IPAC2022, 12.-17.06.2022, Bangkok, Thailand
    Proceedings of the 13th International Particle Accelerator Conference, Geneva, Switzerland: JACoW Publishing, 978-3-95450-227-1
    DOI: 10.18429/JACoW-IPAC2022-WEIXSP1

Permalink: https://www.hzdr.de/publications/Publ-35968
Publ.-Id: 35968


Supporting Data for PhD Dissertation of Klara Lünser, TU Dresden, 2022

Lünser, K.

This collection belongs to the PhD Dissertation of Klara Lünser with the title "Martensitische Phasenumwandlungen und Zwillingsbildung in epitaktisch gewachsenen Nickel-Titan-Schichten" (Martensitic phase transitions and twinning in epitaxial nickel-titanium thin films). The folder contains raw data of atomic force microscopy, resistivity, in situ scanning electron and pole figure measurements. It also contains the MATLAB code used for calculations of pole figures and inverse pole figures with martensite theories. The file "Probenzuordnung" explains which sample and data was used for which figure in the dissertation. 

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Permalink: https://www.hzdr.de/publications/Publ-35967
Publ.-Id: 35967


Self-evaluation Photon and Neutron RIs for FAIR data certification

Lambert, S.; McBirnie, A.; Matthews, B.; Fiedler, M.; Gagey, B.; Görzig, H.; Knodel, O.; Kourousias, G.; Markvardsen, A.; Minotti, C.; Ounsy, M.; Schön, S.; Soler, N.; Spruce, D.; Vukolov, A.; Collins, S.; Pozsa, K.

This ExPaNDS project deliverable describes a FAIR self-assessment undertaken by the ten
ExPaNDS partner Photon and Neutron Research Infrastructures (PaN RIs) over the
three-month period July – September 2022. After reviewing selected examples of existing
FAIR evaluation frameworks designed to enable assessment at different levels (dataset,
repository, and organisation), the report describes the evaluation approach adopted for the
ExPaNDS FAIR self-assessment. As no existing framework met our specific need to focus
on FAIR workflows and processes in PaN RIs, it was necessary to select, combine, and
adapt existing frameworks. Supported by four underlying guiding principles, our approach
drew heavily on the FAIR Principles, the RDA FAIR Data Maturity Model, and FAIRsFAIR’s
CoreTrustSeal+FAIRenabling framework. Post-evaluation feedback from ExPaNDS partners
indicated that they found the FAIR self-assessment a useful and valuable exercise for
understanding current levels of FAIRness at their facilities and for articulating what
implementations they have in progress or planned to support FAIR in future. A key output of
the ExPaNDS FAIR evaluation is the collected self-assessment reports from the ten partner
facilities. These reports are published openly and in full as part of the deliverable. In addition,
the self-assessments are supplemented with some high-level observations on the state of
the FAIR journey across the ExPaNDS facilities.

Keywords: FAIR; Metadata; ExPaNDS; European Photon and Neutron facilities

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Permalink: https://www.hzdr.de/publications/Publ-35966
Publ.-Id: 35966


Traveling-wave electron accelerators – leveraging exascale computing towards scalable laser-plasma accelerators

Debus, A.; Steiniger, K.; Widera, R.; Bastrakov, S.; Carstens, F.-O.; Meyer, F.; Pausch, R.; Lebedev, A.; Garten, M.; Kluge, T.; Kelling, J.; Hernandez Arreguin, B.; Young, J.; Pöschel, F.; Hübl, A.; Rogers, D.; Juckeland, G.; Chandrasekaran, S.; Bussmann, M.; Schramm, U.

Traveling-wave electron acceleration (TWEAC) is an advanced laser-plasma accelerator scheme, which is neither limited by dephasing, nor by pump depletion or diffraction. Such accelerators are scalable to energies beyond 10 GeV without the need for staging and are candidates for future compact electron-positron colliders based on existing CPA lasers.
Requiring to model a large plasma volume in 3D at high-resolution over an extended acceleration distance for high-fidelity results, TWEAC simulations need exascale compute resources -- even "small" test simulations need hundreds of GPUs.
We present recent progress in TWEAC simulations and various technical advances in the 3D3V particle-in-cell code PIConGPU that enable running on the upcoming Frontier cluster (#1 in TOP500), most notably support of the HIP computational backend allowing to run on AMD GPUs, as well as openPMD, PICMI and algorithmic developments. These advances are mainly driven by our participation in OLCF’s Frontier Center for Accelerated Application Readiness providing access to the hardware platform of the Frontier exascale supercomputer. We show performance data and present recent applications of PIConGPU profiting from these developments.

Keywords: TWEAC; Traveling-wave electron accelerators; laser pulse-front tilt; Laser-plasma accelerator; PIConGPU; particle-in-cell code

  • Poster
    EuroNNAc Special Topic Workshop 2022, 18.-24.09.2022, Isola d'Elba, Italien

Permalink: https://www.hzdr.de/publications/Publ-35965
Publ.-Id: 35965


High-fidelity particle-in-cell simulations at multiple scales

Debus, A.

The particle-in-cell method is central to providing a kinetic description of the relativstic, nonlinear plasma dynamics -- particularly when interacting with ultrashort laser pulses and particle beams. Its broad applicability ranges from advanced plasma accelerators of electrons or ions, warm dense matter to astrophysics. A major challenge to a better understanding is to integrate disparate spatial and temporal scales, as well as physics into consistent, predictive models that can be compared to experimental results. While the large-scale dynamics is often determined by hydrodynamic evolution, the microscale physics includes ionization, radiation processes from infrared to xrays, atomic physics, as well as QED effects. Interfacing and integrating domain-specific numerical codes, such as particle trackers, FEL codes, requires data standards for seamless data exchange. Based on recent examples from plasma accelerator research using the 3D3V particle-in-cell code PIConGPU, I will outline the state-of-the art and challenges of particle-in-cell simulations to and show current strategies of solving them in large-scale simulations on heterogenous high-performance computing environments.

Keywords: Particle-in-cell; PIConGPU; multi-scale

  • Invited lecture (Conferences)
    Multiscale Modeling of Matter under Extreme Conditions, 11.-16.09.2022, Görlitz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35963
Publ.-Id: 35963


Chelator-based non-peptidic radiotracers for PET imaging of PD-L1 with copper-64

Krutzek, F.; Donat, C.; Ullrich, M.; Rodrigues Loureiro, L. R.; Kopka, K.; Stadlbauer, S.

Objective: The programmed cell death-ligand 1 (PD-L1) is upregulated on many different cancers and allows the tumor cells to evade immune response through binding to the PD-1 receptor.[1] Monoclonal antibodies, i.e. checkpoint inhibitors, are able to break this blockade and thus reactivate the immune system.[2] However, only 30% of the patients respond to antibody-based immunotherapy. Because PD-L1 is heterogeneously expressed within and across tumor sites, there is an urgent clinical need for a non-invasive, diagnostic imaging approach helping for therapy decision. Radiotracers for PET and SPECT imaging are able to meet these requirements. Especially small molecules are favourable, because of their short clearance times and for providing high imaging contrast.[3]

Methods: Modification of two literature known small molecule PD-L1 inhibitors with water-solubilizing groups, different linkers and a DOTA chelator resulted in six different radioligands. Labeling was performed with Cu-64 (HZDR, 30 MeV TR-FLEX cyclotron) and binding affinities to PD-L1 were determined in vitro on transduced PC3 cells stably overexpressing human PD-L1. Qualitative PET scans (nanoSCAN PET/CT scanner, Mediso) were performed in NMRI-FoxN1-nude mice bearing PC3-hPD-L1 xenografted tumors.

Results: Organic synthesis started from biaryl building blocks (R1 = H, R2 = Br and R1 = R2 = Me), which underwent a Mitsunobu reaction with the central chloroaryl moiety. The bis(sulfonic acid) group was attached via a sarcosine spacer. Three different linker structures were synthesized and attached by Cu(I)-catalyzed click reaction. Synthesis was finished with DOTA conjugation and subsequent quantitative labeling with Cu-64 under standard labeling conditions was achieved. Using the shake flask method, log(D) values ranging from –1.5 to –2.5 were obtained. Saturation binding assays revealed that biphenyl compounds with R1 = R2 = Me showed promising binding affinities to PD-L1 (KD between 60 and 123 nM). In micro-PET experiments, the radioligands exhibited unusual high circulation times. PET images obtained after 15 h p.i. showed the highest tumor uptake and moderate uptake in the liver.
Conclusion: A library of new PD-L1 targeting non-peptide radiotracers based on small molecule lead structures bearing water-soluble groups and a chelator was successfully synthesized. All compounds showed moderate binding affinities toward PD-L1. Qualitative PET/CT scans showed a moderate uptake in PD-L1 positive tumors. For improved pharmacokinetics the lipophilicity should be further reduced and DOTA replaced by more optimal chelators such as NODAGA to avoid possible copper transchelation in the liver.

References:

[1] M. A. Postow, M. K. Callahan, J. D. Wolchok, J Clin Oncol 2015, 33, 1974-1982.
[2] S. L. Topalian, C. G. Drake, D. M. Pardoll, Cancer cell 2015, 27, 450-461.
[3] S. Chatterjee, W. G. Lesniak, S. Nimmagadda, Mol. Imaging 2017, 16, 1-5.

  • Lecture (Conference)
    International Symposium on Radiopharmaceutical Sciences, 29.05.-02.06.2022, Nantes, France

Permalink: https://www.hzdr.de/publications/Publ-35962
Publ.-Id: 35962


Traveling-wave electron accelerators – towards scalable laser-plasma accelerators beyond 10GeV

Debus, A.; Steiniger, K.; Widera, R.; Bastrakov, S.; Carstens, F.-O.; Meyer, F.; Pausch, R.; Garten, M.; Kluge, T.; Kelling, J.; Hernandez Arreguin, B.; Young, J.; Pöschel, F.; Hübl, A.; Rogers, D.; Juckeland, G.; Chandrasekaran, S.; Bussmann, M.; Schramm, U.

Traveling-wave electron acceleration (TWEAC) is an advanced laser-plasma accelerator scheme, which is neither limited by dephasing, nor by pump depletion or diffraction. Such accelerators are scalable to energies beyond 10 GeV without the need for staging and are candidates for future compact electron-positron colliders based on existing CPA lasers. TWEAC utilizes two pulse-front tilted laser pulses whose propagation directions enclose a configurable angle. The accelerating cavity is created along their overlap region in the plasma and can move at the vacuum speed of light. The oblique laser geometry enables to constantly cycle different laser beam sections through the interaction region, hence providing quasi-stationary conditions of the wakefield driver.

The TWEAC geometry enables to access to a wide range of regimes, which are customizable in cavity geometry, laser-to-electron energy efficiency and the required laser properties at different plasma densities, making the scheme suitable for high-rep rate lasers at low energies per pulse to multi-PW laser facilities. Exploring these regimes in high-fidelity simulations is computationally highly demanding, as these need to include large plasma volumes in 3D at high-resolution over an extended acceleration distance. Since even "small" test simulations need hundreds of GPUs, TWEAC simulations require exascale compute resources.

We present recent progress in TWEAC simulations and various technical advances in the 3D3V particle-in-cell code PIConGPU that enable running on the upcoming Frontier cluster, most notably support of the HIP computational backend allowing to run on AMD GPUs, as well as openPMD, PICMI and algorithmic developments. These advances are mainly driven by our participation in OLCF’s Frontier Center for Accelerated Application Readiness providing access to the hardware platform of the Frontier exascale supercomputer. We show performance data and recent applications of PIConGPU profiting from these developments.

Keywords: Traveling-wave electron acceleration; TWEAC; PIConGPU; Laser-plasma accelerator; Particle-in-cell simulations

  • Lecture (Conference)
    Advanced Accelerator Concepts Workshop 2022, 06.-11.11.2022, Long Island, New York, USA

Permalink: https://www.hzdr.de/publications/Publ-35961
Publ.-Id: 35961


PIConGPU + X – Building blocks for successful Exascale accelerator simulations

Debus, A.; Steiniger, K.; Widera, R.; Bastrakov, S.; Carstens, F.-O.; Meyer, F.; Pausch, R.; Garten, M.; Bernert, C.; Kluge, T.; Willmann, A.; Kelling, J.; Hernandez Arreguin, B.; Young, J.; Pöschel, F.; Hübl, A.; Rogers, D.; Juckeland, G.; Hoffmann, N.; Chandrasekaran, S.; Schramm, U.; Bussmann, M.

Exascale computing is close to becoming a reality. As technology progresses, it has become clear that heterogeneous computing is going to stay and adapting to new hardware is an ongoing challenge. Since 2015 PIConGPU has paved the way to accelerating plasma simulations across compute platforms using the Alpaka framework. This has enabled early adaption to new compute hardware and readiness for Exascale compute capabilities.
However, experience has shown that the real challenges are of a different nature. The first is in detailed analysis of the data produced in simulations. Here, we present our current work on I/O, code coupling, visual analytics and large-scale data analytics.
The second, and more pressing challenge, is comparison to experiment. Here, not only has the increasing quality of experiments put more demand on simulation quality, but more and more the demand for fast, close to real time analysis has grown. This puts high quality simulations to the test, as runs on supercomputers tend to be costly. We present workflows to match experiment and simulations and a future look on how feedback loops between experiment and simulation can be optimized.

Keywords: Particle-in-cell; PIConGPU; exascale; performance portable; synthetic diagnostics

  • Invited lecture (Conferences)
    Advanced Accelerator Concepts Workshop 2022, 06.-11.11.2022, Hyatt Regency, Hauppauge, Long Island, NY, USA

Permalink: https://www.hzdr.de/publications/Publ-35960
Publ.-Id: 35960


Sub-band gap infrared absorption in Si implanted with Mg

Wang, M.; Shaikh, M. S.; Kentsch, U.; Heller, R.; Zhou, S.

Single-crystalline Mg-implanted Si layers are synthesized by ion implantation followed by pulsed laser melting. The Mg doping concentration is reaching 10²¹ cm⁻³. The Raman, Rutherford backscattering spectrometry/channeling and particle induced x-ray emission measurements confirm the recrystallization of the Mg-implanted Si layer. A strong below band gap infrared absorption over the wavelength range of 1.4–6.2 µm (0.2–0.87 eV, in the mid-infrared range) has been observed in the Mg-implanted Si layers. It is associated with deep levels induced by Mg atoms at high implantation level. This work points out the potential of Mg-implanted Si for room-temperature light detection in a broad infrared range for the new generation of Si-based photonics.

Keywords: sub-band gap absorption; ion implantation; infrared photoresponse; deep-level impurity; Mg-implanted

Related publications

Permalink: https://www.hzdr.de/publications/Publ-35959
Publ.-Id: 35959


Learning Electron Bunch Distribution along a FEL Beamline by Normalising Flows

Willmann, A.; Couperus Cabadağ, J. P.; Chang, Y.-Y.; Pausch, R.; Ghaith, A.; Debus, A.; Irman, A.; Bussmann, M.; Schramm, U.; Hoffmann, N.

Understanding and control of Laser-driven Free Electron Lasers remain to be difficult problems that require highly intensive experimental and theoretical research. The gap between simulated and experimentally collected data might complicate studies and interpretation of obtained results. In this work we developed a deep learning based surrogate that could help to fill in this gap. We introduce a surrogate model based on normalising flows for conditional phase-space representation of electron clouds in a FEL beamline. Achieved results let us discuss further benefits and limitations in exploitability of the models to gain deeper understanding of fundamental processes within a beamline.

  • Open Access Logo Poster
    Machine Learning and the Physical Sciences, 03.12.2022, the New Orleans Convention Center in New Orleans, USA

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Permalink: https://www.hzdr.de/publications/Publ-35958
Publ.-Id: 35958


Spectroscopy of XFEL heated Cu and x-ray absorption in laser-produced Warm Dense Cu

Smid, M.

We report on a recent (Feb 2022) experiment on the spectroscopic characterization of XFEL-heated Cu foil targets. The 1-5μm thick Cu foils were irradiated by the tightly focused XFEL beam (~1μm focus, up till 1mJ in energy, European XFEL), heating the target to more then 100 eV, and clearly observing emission from ions up till Cu 25+. Three crystal spectrometers were measuring the emission and scattering in the range ~ 8000 - 9800 eV, i.e. covering the lines of Cu Kα and Kβ, including their ionized satellites. The XFEL photon energy was varied in the range 8.8-9.8 keV. The primary aim is to resolve the continuum lowering by checking the shifts of K edge for various ionizations, in a similar manner as was done earlier on lighter elements. Apart from this, many interesting phenomena can be studied from this extensive dataset, like the double-core hole (hollow ion) emission and its shift, resnonances, XRTS, and even Xanes absorption, by comparing the emission from the front and rear sides of the target. Having those data available in a well characterized system provides a high demand as well as benchmark for precise atomic simulations, and in general leads to a better understanding of Warm Dense Copper on the atomic physics level.

  • Lecture (Conference)
    Radiative Properties of Hot Dense Matter, 14.-18.11.2022, Santa Fe, United States of America

Permalink: https://www.hzdr.de/publications/Publ-35957
Publ.-Id: 35957


Combined Au/Ag nanoparticle creation in ZnO nanopillars by ion implantation for optical response modulation and photocatalysis

Macková, A.; Jagerová, A.; Lalik, O.; Mikšová, R.; Poustka, D.; Mistrík, J.; Holý, V.; Schutter, J. D.; Kentsch, U.; Marvan, P.; Azarov, A.; Galeckas, A.

ZnO nanopillars were implanted with Au-400 keV and Ag-252 keV ions with ion fluences from 1 × 10¹⁵ cm⁻² to 1 × 10¹⁶ cm⁻². We compared ZnO nanopillars solely implanted with Au-ions and dually-implanted with Au and Ag-ions. Rutherford Back-Scattering spectrometry (RBS) confirmed Ag and Au embedded in ZnO nanopillar layers in a reasonable agreement with theoretical calculations. A decreasing thickness of the ZnO nanopillar layer was evidenced with the increasing ion implantation fluences. Spectroscopic Ellipsometry (SE) showed a decrease of refractive index in the nanopillar parts with embedded Au, Ag-ions. XRD discovered vertical domain size decreasing with the proceeding radiation damage accumulated in ZnO nanopillars which effect was preferably ascribed to Au-ions. SE and diffuse reflectance spectroscopy (DRS) showed optical activity of the created nanoparticles at wavelength range 500 – 600 nm and 430 – 700 nm for the Au-implanted and Au, Ag-implanted ZnO nanopillars, respectively. Photoluminescence (PL) features linked to ZnO deep level emission appear substantially enhanced due to plasmonic interaction with metal nanoparticles created by Ag, Au-implantation. Photocatalytic activity seems to be more influenced by the nanoparticles presented in the layer rather than the surface morphology. Dual implantation with Ag, Au-ions enhanced optical activity to a larger extent without significant morphology deterioration as compared to the solely Au-ion implanted nanopillars.

Keywords: ZnO nanopillars; Au/Ag nanoparticles; ion implantation; SPR; doped ZnO nanostructures

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Permalink: https://www.hzdr.de/publications/Publ-35956
Publ.-Id: 35956


Data publication: Energy relaxation and electron-phonon coupling in laser-excited metals

Zhang, J.; Qin, R.; Zhu, W.; Vorberger, J.

DFT data and results for Al and Cu for the DOS, phonon DOS, and Eliashberg function depending on the electron temperature.

Keywords: electron-phonon; DFT; laser; laser-matter interaction; two-temperature model; relaxation; energy transfer

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Permalink: https://www.hzdr.de/publications/Publ-35955
Publ.-Id: 35955


Nonlinear dynamics of Dirac fermions in topological HgTe structures

Uaman Svetikova, T. A.; Pashkin, O.; de Oliveira, T.; Bayer, F.; Berger, C.; Fuerst, L.; Buhmann, H.; Molenkamp, L. W.; Helm, M.; Kiessling, T.; Winnerl, S.; Kovalev, S.; Astakhov, G.

High harmonic generation (HHG) has applications in various fields, including ultrashort pulse measurements, material characterization and imaging microscopy. Strong THz nonlinearity and efficient third harmonic generation (THG) were demonstrated in graphene [1], therefore it is natural to assume the presence of the same effect in other Dirac materials, such as topological insulators (TI). Topological states can be found in HgTe quantum wells with a thickness of more than 6.3 nm [2], and strained 3D Hg1-xCdxTe thin films with cadmium fraction x < 0.16 [3].
We used a series of HgTe samples corresponding to three qualitatively different cases: 2D trivial and topological structures and 3D topological insulators. By using moderate THz fields, the presence of highly efficient THG was measured in these samples at different temperatures and THz powers. This provides insight into physical mechanisms leading to THG in TIs. For in-depth understanding of Dirac fermions dynamics and dominating scattering mechanisms in HgTe TI, we conducted THz pump-probe experiments that reveal several relaxation time scales.

[1] Hafez, H. A. et al., Nature 561, 507 (2018).
[2] Bernevig, B. et al. Science 314, 5806 (2006): 1757-1761.
[3] Brüne, C., et al. Phys. Rev. Lett. 106, 12 (2011): 126803.

Keywords: topological insulators; HgTe; nonlinear dynamics

  • Lecture (Conference)
    3rd QMA retreat, 12.-14.10.2022, Friedrichroda, Deutschland
  • Poster
    DPG Meeting of the Condensed Matter Section (SKM): Regensburg 2022, 04.-09.09.2022, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35954
Publ.-Id: 35954


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