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33398 Publications

Steel related activities and capabilities at HZDR

Gerbeth, G.
  • Invited lecture (Conferences)
    Sino-German Symposium „Future Steel“, 18.07.2019, Shanhai, China

Permalink: https://www.hzdr.de/publications/Publ-30740
Publ.-Id: 30740


Hollow Au@TiO2 porous electrospun nanofibers for catalytic applications

Kumar, L.; Singh, S.; Horechyy, A.; Formanek, P.; Hübner, R.; Albrecht, V.; Weißpflog, J.; Schwarz, S.; Puneet, P.; Nandan, B.
Catalytically active porous and hollow titania nanofibers encapsulating gold nanoparticles were fabricated using a combination of sol-gel chemistry and coaxial electrospinning technique. We report the fabrication of catalytically active porous and hollow titania nanofibers encapsulating gold nanoparticles (AuNPs) using a combination of sol-gel chemistry and coaxial electrospinning technique. The coaxial electrospinning involved the use of a mixture of poly(vinyl pyrrolidone) (PVP) and titania sol as the shell forming component, whereas a mixture of poly(4-vinyl pyridine) (P4VP) and pre-synthesized AuNPs constituted the core forming component. The core-shell nanofibers were calcined stepwise up to 600 °C which resulted in decomposition and removal of the organic constituents of the nanofibers. This led to the formation of porous and hollow titania nanofibers, where the catalytic AuNPs were embedded in the inner wall of the titania shell. The catalytic activity of the prepared Au@TiO2 porous nanofibers was investigated using a model reaction of catalytic reduction of 4-nitrophenol and Congo red dye in the presence of NaBH4. The Au@TiO2 porous and hollow nanofibers exhibited excellent catalytic activity and recyclability, and the morphology of the nanofibers remained intact after repeated usage. The presented approach could be a promising route for immobilizing various nanosized catalysts in hollow titania supports for the design of stable catalytic systems where the added photocatalytic activity of titania could further be of significance.

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Permalink: https://www.hzdr.de/publications/Publ-30732
Publ.-Id: 30732


The role of boron on exchange coupling in NiFe/Ru1−xBx/FeCo trilayer structures

Mckinnon, T.; Hübner, R.; Heinrich, B.; Girt, E.
In this work, we study the interlayer exchange coupling, J, between two NiFe and FeCo layers in a series of NiFe/Ru1-xBx(d)/FeCo synthetic antiferromagnet (SAF) samples, where the thickness of the spacer layer, d, is varied from 0.4 nm to 0.9 nm, and the boron concentration, x, is varied from 0 to 15 at. %. The samples are studied as deposited and after being annealed at 250 °C. B is deposited into the Ru spacer layer to investigate what occurs after annealing a FeCoB/Ru/FeCoB SAF structure, which is commonly used in modern nanoscale magnetic devices, in which the FeCoB layer crystallizes to FeCo and B diffuses to adjacent layers. We find that J in as-deposited samples is relatively unaffected by adding up to 15% B into the Ru spacer layer. However, after annealing at 250 °C, J changes the sign from antiferromagnetic coupling to ferromagnetic coupling for spacer layers thinner than 0.45 nm for 5% and 10% B and thinner than 0.525 nm for 15% B. We used transmission electron microscopy energy-dispersive x-ray spectroscopy in order to investigate the diffusion of atoms within a similar Ta(2.5 nm)/NiFe(0.8 nm)/Ru1-xBx(23 nm) layer structure. We find that after annealing at 250 °C, the sample containing 15% B within the Ru85B15 layer had significantly more diffusion of Fe into the Ru85B15 layer, from the NiFe layer, as compared to the sample with 0% B. Thus, the presence of B within the spacer layer enhances diffusion of Fe into the spacer layer.

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Permalink: https://www.hzdr.de/publications/Publ-30731
Publ.-Id: 30731


Microstructure, texture and hardness of a metastable β-titanium alloy after bar-rolling and annealing

Gu, B.; Chekhonin, P.; Schaarschuch, R.; Oertel, C.-G.; Xin, S. W.; Ma, C. L.; Zhou, L.; Gan, W. M.; Skrotzki, W.
The microstructure and texture evolution of a metastable Ti-5Al-3V-3Mo-2Cr-2Zr-1Nb-1Fe alloy during bar-rolling and after various thermal treatments was investigated by high-energy synchrotron diffraction and electron backscatter diffraction. Bar-rolling is applied in the (α+β)-phase field in order to achieve a bi-modal (duplex) microstructure. The effect of dynamic recrystallized and recovered zones on texture of Ti5321was analyzed separately, as well as the texture of primary α-precipitates and secondary α-lamellae. The texture of the recovered zones is characterized by a cube component ({001}<100>) plus α- and γ-fibre with dominant {100}<110>, {112}<110>, {111}<110> components, while the texture of the recrystallized zones is a strong cube texture. After aging or recrystallization plus aging, this texture component remains, while it disappears after solution treatment. The primary α-precipitates have their c-axes perpendicular to the rolling direction and do not follow the Burgers orientation relationship. This texture characteristics remains after various thermal heat treatments. Secondary α-lamellae obey the Burgers orientation relationship. Moreover, a variant selection of secondary α-lamellae occurs. The mechanism of texture formation of the β-phase and the precipitation behavior of the α-phase is discussed.
The hardness increase can be attributed to size, shape and volume fraction of the α-precipitates.
Different combinations of primary α- and secondary α-precipitates make an increase in hardness of about 11%.
Keywords: Metastable β-titanium alloy, Bar-rolling, Microstructure, Texture, Microhardness

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Permalink: https://www.hzdr.de/publications/Publ-30724
Publ.-Id: 30724


HIM and AFM Data set from first AFM in the HIM test

Hlawacek, G.ORC; Andany, S.ORC

In this work, the integration of an atomic force microscope (AFM) into a helium ion microscope
(HIM) is reported for the first time. The helium ion microscope is a powerful instrument, capable of sub-
nanometer resolution imaging and machining nanoscale structures, while the AFM is a well-established
versatile tool for multiparametric nanoscale metrology. Combining the two techniques opens the way for
unprecedented, in-situ, correlative analysis at the nanoscale. Nanomachining and analysis can be
performed without contamination of the sample as well as avoiding environmental changes between
processing steps. The practicality of the resulting tool lies in the complementarity of the two techniques as
the AFM offers not only true 3D topography maps---something the HIM can only provide in an indirect
way---but also allows for nanomechanical property mapping, as well as electrical and magnetic
characterisation of the sample after focused ion beam materials modification with the HIM. The
experimental setup is described and evaluated through a series of correlative experiments, demonstrating
the feasibility of the integration.

Keywords: Helium Ion Microscopy; Atomic Force Microscopy
Related publications
An atomic force microscope integrated with a helium ion … (Id 30689) has used this publication of HZDR-primary research data
Alles Test Kursiv (Id 27438) is new version of this publication
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-02-04
    DOI: 10.14278/rodare.249

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Permalink: https://www.hzdr.de/publications/Publ-30718
Publ.-Id: 30718


Dynamics of Bubble Formation at Micro-orifices under Constant Gas Flow Conditions

Mohseni, E.ORC; Jose Kalayathine, J.; Reinecke, S.ORC; Hampel, U.ORC

Fine gas dispersion into a liquid is requested in a number of industrial applications. One way to achieve finer gas dispersion is to downsize the openings at which the gas bubbles are generated. Accordingly, we have investigated the dynamics of bubble formation from submerged orifices ranging from 0.04 to 0.8 mm at a comprehensive range of gas flow rates for a system of air and deionized water. In this range of orifice size, we observe a different mechanism of bubble formation compared with millimeter-range orifices. We discuss the observations on the basis of temporal change of the bubble shape, bubble base expansion, and detachment criteria. At submillimeter orifices, the mechanism of bubble formation is highly influenced by the capillary pressure and the gas kinetic energy. The latter results in congregation of small bubbles in the vicinity of the orifice, even at very small gas flow rates. Moreover, we studied the evolution of individual forces applied to the surface of bubbles during their formation. We found that the formation of bubbles at submillimeter orifices cannot be described with a quasi-static force balance. Finally, we present a bubbling regime map using proper dimensionless numbers.

Keywords: Bubble Formation; Submillimeter Orifices; Bubbling Regime; Bubbling Dynamics; Stainless Steel Orifice
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-02-03
    DOI: 10.14278/rodare.247

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Permalink: https://www.hzdr.de/publications/Publ-30717
Publ.-Id: 30717


The Late Paleozoic tectonometamorphic evolution of Patagonia revisited: Insights from the pressure-temperature-deformation-time (P-T-D-t) path of the Gondwanide basement of the North Patagonian Cordillera (Argentina)

Oriolo, S.; Schulz, B.; Gonzalez, P. D.; Bechis, F.; Olaizola, E.; Krause, J.; Renda, E. M.; Vizàn, H.
Combined field structural analysis with in situ EPMA (electron probe microanalysis) Th-U-Pb monazite dating, petrologic and microstructural data provide a reconstruction of the pressure-temperature-deformation-time (P-T-D-t) path of the Gondwanide basement of the North Patagonian Cordillera. For samples from the Challhuaco hill, the timing of development of the metamorphic S2 foliation and associated L2 lineation and tight to isoclinal F2 folds is constrained by monazite ages of 299 ± 8 and 302 ± 16 Ma during peak metamorphic conditions of ca. 650 °C and 11 kbar, achieved during prograde metamorphism and progressive deformation. Metamorphism and deformation of metamorphic complexes of the North Patagonian Andes seem to record Late Paleozoic crustal thickening and are coeval with metamorphism of accretionary complexes exposed further west in Chile, suggesting a coupled Late Devonian-Carboniferous evolution. Instead of the result of continental collision, the Gondwanide orogeny might thus be essentially linked to transpression due to advancing subduction along the proto-Pacific margin of Gondwana. On the other hand, a second generation of monazite ages of 171 ± 9 and 170 ± 7 Ma constrain the timing of low-grade metamorphism related to kink band and F3 open fold development during Jurassic transtension and emplacement of granitoids. Finally, a Cretaceous overprint, likely resulting from hydrothermal processes, is recorded by monazite ages of 110 ± 10 and 80 ± 20 Ma, which might be coeval with deformation along low-grade shear zones during the onset of Andean transpression.
Keywords: EPMA Th-U-Pb monazite dating, in situ petrochronology, garnet metapelite thermobarometry, Upper Paleozoic, Terra Australis, southwestern Gondwan

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Permalink: https://www.hzdr.de/publications/Publ-30714
Publ.-Id: 30714


Epithermal Ag-(Au)-Zn-Pb mineralisation in the northern part of the Freiberg District, Germany

Swinkels, L.; Rossberg, C.; Schulz-Isenbeck, J.; Frenzel, M.ORC; Gutzmer, J.ORC; Burisch, M.
The polymetallic veins in the Freiberg district form one of the largest epithermal systems in Europe. It produced over 5600 t of Ag during active mining between 1168 and 1969. Historically, exploration focused on the centre of the district, with peripheral sub-districts exploited only to shallow depth. Recent exploration activity focuses on these peripheral regions, yet only a limited amount of modern geochemical data is available and the underlying ore-forming processes are insufficiently understood. Here, we present preliminary geochemical, fluid inclusion, and petrographic data for 55 samples from the historical mine camps of Reinsberg and Kleinvoigtsberg (northern peripheral sub-district). Samples were selected from the scientific collections of the TU Bergakademie Freiberg and collected from outcrops in the field. They include vertical profiles of two major veins extending from 18 to 532 meters below ground level. The data is combined with previous literature descriptions to develop a genetic model for the northern sector of the Freiberg district. Mineralisation in the Reinsberg and Kleinvoigtsberg mine camps is hosted by polystadial Ag-(Au)-Zn-Pb veins. The paragenetically oldest mineralisation, Stage I, is dominated by base metal sulphides and quartz; it has been encountered most prominently in the deepest levels of the historic mines. The occurrence of carbonates and the introduction of Ag-Sb sulphides and sulfosalts mark the transition to Stage IIa. At shallower mining levels, carbonate recedes and quartz returns as the major gangue mineral, indicating the transition to Stage IIb. Stage IIb vein infill is often breccia-textured and carry the highest silver grades. At the present day surface, veins consist of quartz and host rock fragments, forming a cockade breccia texture (stage III). Although no visible sulphides are present, such quartz breccias contain up to 2.5 g/t Au. Recent studies show that the main ore-forming process in the northern district seems to be cooling - causing distinct district and vein-scale zoning. Effervescence of CO2 is most likely the underlying process behind the transition from quartz to carbonate gangue. An understanding of mineral zonation and its underlying ore-forming processes can be translated into mappable exploration criteria. In this case, the highest ore grades (Ag and Au) are associated with Stage IIb (Ag-Sb-sulfosalts-quartz assemblage). This assemblage occurs always wedged between the carbonate-rich assemblage of Stage IIa (below) and the sulphide-poor quartz Stage III (above). This systematic relation may well constitute an important exploration vector for the Freiberg district.
  • Lecture (Conference)
    Geomünster 2019, 22.-25.09.2019, Münster, BRD

Permalink: https://www.hzdr.de/publications/Publ-30713
Publ.-Id: 30713


Mineralogical zoning within the Freiberg epithermal Ag- (Au)-Pb-Zn-Cu system, Germany

Swinkels, L.; Rossberg, C.; Schulz-Isenbeck, J.; Burisch, M.; Frenzel, M.ORC; Gutzmer, J.ORC
The Freiberg epithermal system comprises numerous hydrothermal veins with rich Ag-(Au)-Pb-Zn-Cu mineralisation. Even after more than 800 years of extensive mining, substantial resources remain in the northern sub-districts. This area is subject to recent exploration activity. Preliminary petrographic data of two vertical profiles from the northern part of the district are presented and a new model for the district-scale zoning is proposed. The highest Ag grades occur in Ag-Sb-S-quartz veins and seem to systematically occur above an Ag-Sb-S-Carbonate stage and below Sb-S-quartz mineralisation. This high-grade Ag mineralisation is relatively distal, shallow, and abundant in the northwest sector of the Freiberg district. This, and similar insights may be used to develop new exploration vectors for the Freiberg district.
  • Poster
    15th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, 26.-30.08.2019, Glasgow, UK

Permalink: https://www.hzdr.de/publications/Publ-30712
Publ.-Id: 30712


Explaining metal zonation at the Lisheen Zn-Pb deposit, Ireland

Frenzel, M.ORC; Röhner, M.; Gutzmer, J.ORC; Burisch, M.; Cook, N. J.; Gilbert, S.; Ciobanu, C. L.; Güven, J.
Metal zonation is an important feature of low-temperature carbonate-hosted Zn-Pb deposits. Its origin, however, remains poorly understood. In this article, we use the Lisheen deposit in Ireland as a case study to show how thermodynamic modelling can explain these zonation patterns. Based on input data derived from fluid inclusion studies, bulk ore geochemistry and accepted models of ore formation in the Irish Orefield we construct a reaction path model that successfully accounts for the major features of the mineralisation, most importantly the presence of Cu-Ni-As-rich core zones around hydrothermal feeder structures, surrounded by more distal Fe-Zn-Pb-rich mineralisation. The outcomes of this study strongly support current metallogenetic models for Irish-type deposits and have implications for near-deposit exploration.
  • Lecture (Conference)
    15th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, 26.-30.08.2019, Glasgow, UK
  • Lecture (Conference)
    Geomünster 2019, 22.-25.09.2019, Münster, BRD

Permalink: https://www.hzdr.de/publications/Publ-30711
Publ.-Id: 30711


Mineralogy of the polymetallic Waschleithe Zn-Pb-(W) skarn – implications for skarn genesis in the Schwarzenberg district, western Erzgebirge, Germany

Reinhardt, N.; Frenzel, M.ORC; Gutzmer, J.ORC; Meinert, L. D.; Gerdes, A.; Burisch, M.
The Schwarzenberg district (SD) in the western Erzgebirge comprises a series of polymetallic skarn bodies with significant resource potential for Sn, W, Zn, and In. Skarn mineralisation in the SD is hosted by low- to medium-grade metasedimentary units forming the so-called Schwarzenberg Gneiss Dome (SGD). Recent exploration, mainly for Sn, W, and In, targeted the large Globenstein, Hämmerlein and Tellerhäuser skarn bodies (several km strike length). Fertile skarn mineralisation in these skarns is related to the late- to post-collisional phase of the Variscan Orogeny (325-295 Ma). Economically important large skarn bodies as well as smaller satellites of the SGD have thus far only been investigated individually, rather than being considered part of a potentially district-wide mineralizing system (~ 12 x 15 km). The Waschleithe skarn in the far north of the SGD is a typical example for a smaller skarn body. Considering its distal position within the SGD it provides valuable insight into district-scale mineral zoning. Mineralisation occurs within two skarn horizons hosted by marble interlayered with mica schists. The sharp contact between skarn and marble is well exposed in historical mine workings. Coarse-grained pyroxene (hedenbergite-diopside), finer-grained subordinate yellowish-green andraditic garnet and Mn-rich pyroxenoids are the dominant constituents of the prograde skarn mineral assemblage. All of them overprint the metamorphic microfabric of the marble. A retrograde skarn assemblage is only weakly developed and consists mainly of ilvaite, epidote, vesuvianite, amphibole, chlorite, quartz, fluorite and hydrothermal calcite. Ore minerals associated with the retrograde mineral assemblage may be grouped into three different assemblages: 1) magnetite, 2) sphalerite, galena, pyrite, and chalcopyrite and 3) scheelite. The retrograde ore mineral assemblages show no association with paragenetically late chlorite, indicating that they formed relatively early during retrograde skarn formation. The marble front, dark pyroxenes, relatively low garnet/pyroxene ratios and the presence of Mn-bearing pyroxenoids indicate that the Waschleithe skarn formed distal to its fluid source relative to skarns with a more proximal mineralogy, such as Hämmerlein. Thus, Waschleithe represents a distal equivalent to the larger skarns of the SGD situated farther to the south. A genetic link between the skarns of the SGD requires a substantial re-evaluation of the size and exploration potential of this mineral system. To test this hypothesis a comprehensive set of mineralogical, geochemical and geochronological data from several skarn bodies of the SGD is currently being acquired.
  • Lecture (Conference)
    Geomünster 2019, 22.-25.09.2019, Münster, BRD

Permalink: https://www.hzdr.de/publications/Publ-30699
Publ.-Id: 30699


The Waschleithe W-skarn - a distal relative of skarns in the Schwarzenberg district, western Erzgebirge, Germany?

Reinhardt, N.; Burisch, M.; Frenzel, M.ORC; Gutzmer, J.ORC; Meinert, L. D.; Gerdes, A.
The Waschleithe skarn located near Schwarzenberg in eastern Germany hosts sub-economic polymetallic W-Zn-Pb-Cu-Fe mineralisation. Its mineralogy is dominated by prograde clinopyroxene and subordinate garnet. The garnet and pyroxene colours of this skarn as well as low garnet/pyroxene ratios are typical for distal skarn settings. Ore minerals (magnetite, sphalerite, galena, chalcopyrite, pyrite, scheelite) in the prograde skarn do not show a clear association with the weakly developed retrograde overprint consisting mainly of late chlorite and calcite.
  • Poster
    15th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, 28.08.2019, Glasgow, UK

Permalink: https://www.hzdr.de/publications/Publ-30698
Publ.-Id: 30698


Assessing the global availability of by-product metals – The cases of Ga, Ge and In

Frenzel, M.ORC
Recently, considerable concerns have been raised about the supply security of certain high-tech elements produced as by-products. To determine in how far these concerns are justified by the actual availability of these elements, a new method was developed to estimate supply potentials, including statistical uncertainties. This was applied to three relevant examples – Ga, Ge and In – to compare their global availability to current and historic production volumes. The assessment is based on detailed estimates of the amounts extractable from various raw material streams given contemporary market prices and technologies. The results show that the supply potentials of all three elements significantly exceed current primary production. However, the degree to which this is the case varies from element to element. Differences also exist in historic growth trends, with indium showing the fastest growth rate of production relative to supply potential at the time of analysis.
Keywords: By-products, Hi-tech metals, Supply security
  • Lecture (others)
    USGS Eastern Competence Center on Mineral Resources - Seminar, 17.12.2019, Reston, VA, USA

Permalink: https://www.hzdr.de/publications/Publ-30697
Publ.-Id: 30697


On the effect of liquid viscosity, density and surface tension on the hydrodynamics of TSL injection systems

Reuter, M. A.; Obiso, D.; Stelter, M.; Kriebitzsch, S.
On the effect of liquid viscosity, density and surface tension on the hydrodynamics of TSL injection systems,
Main features
Top-submerged gas injection
Submerged combustion
Smelting of non-ferrous metals
Example: copper from chalcopyrite (CuFeS2 )
Importance of hydrodynamics:
gas-liquid interface
intensity of mixing
splashing
lance cooling/coating
Keywords: TSL,
  • Lecture (Conference)
    EXTRACTION, 26.-29.08.2019, Ottawa, Canada

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Permalink: https://www.hzdr.de/publications/Publ-30695
Publ.-Id: 30695


Raw data of liquid saturation, pressure drop and porosity of an inclined rotating fixed-bed reactor with inner tube

Timaeus, R.; Schleicher, E.; Bieberle, A.; Hampel, U.; Schubert, M.

The hydrodynamic raw data of an inclined rotating fixed-bed reactor with different inner tubes are given. The phase distributions of nitrogen and cumene in the cross-section of the reactor filled with porous alumina particles were measured via a capacitance wire-mesh sensor. Besides, the the raw data of the specific pressure drops for the investigated operating points are described. Additionally, the attenuation coefficients of different configurations (different particle and inner tube diameter) are collected, which were measured by gamma-ray computed tomography. This publication contains the raw data of the publication "Hydrodynamic data of an inclined rotating fixed-bed reactor" (10.14278/rodare.203).

Keywords: Hydrodynamic analysis, Wire-mesh sensor, Raw data, Gamma-ray computed tomography
Related publications
Identification of the process windows of inclined rotating … (Id 30121) has used this publication of HZDR-primary research data
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-02-03
    DOI: 10.14278/rodare.243

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Permalink: https://www.hzdr.de/publications/Publ-30694
Publ.-Id: 30694


CFD modeling of combustion and heat transfer in the TSL smelter

Reuter, M. A.; Obiso, D.; Kriebitzsch, S.; Stelter, M.
CFD modelling of combustion and heat transfer in the TSL smelter.
The importance of viscous and interfacial forces on the hydrodynamics of the TSL furnace
An experimental and numerical investigation of TSL gas injection in liquid metal
Keywords: CFD modelling, TSL, metal
  • Lecture (Conference)
    EMC19, European Metallurgical Conference, 23.-26.06.2019, Düsseldorf, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-30693
Publ.-Id: 30693


Validation of a VOF approach for the Top-Submerged gas injection in liquid metal

Reuter, M. A.; Obiso, D.; Richter, A.; Akashi, M.; Eckert, S.
The main goal of this work is to prove the reliability of the Volume of Fluid (VOF) model for a top-submerged-lance (TSL) gas injection in a liquid metal bath, therefore trying to close the gap between the modelling of common air/water lab setups and real TSL slag-bath furnaces. Suitable validation data were provided by HZDR, where X-ray imaging was applied to picture the multiphase flow in an Argon - Ga77.2In14.4Sn8.4 system [1].
Keywords: Volume of Fluid, op-submerged-lance, metal, X-ray
  • Lecture (Conference)
    17th Multiphase Flow Conference HZDR, 13.-15.11.2019, Dresden, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-30692
Publ.-Id: 30692


Editorial for World of Metallurgy

Reuter, M. A.
The title of a paper we wrote for this journal in 2014 "Copper: A Key Enabler of Resource Efficiency", or to rephrase it in light of the present Circular Economy (CE) paradigm "Copper: A Key Enabler of the Circular Economy", rings as true as ever.
Keywords: Copper, Resource Efficiency, Circular Economy
  • Erzmetall - World of Metallurgy 72(2019)6, 307-308

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Permalink: https://www.hzdr.de/publications/Publ-30691
Publ.-Id: 30691


The Application Of Subspace Clustering Algorithms In Drill-Core Hyperspectral Domaining

Rafiezadeh Shahi, K.; Khodadadzadeh, M.ORC; Tolosana Delgado, R.ORC; Tusa, L.; Gloaguen, R.ORC
Diamond drilling is used in the mining industry to extract drill-cores for characterising mineral deposits. Traditionally, drill-cores are visually analysed by an on-site geologist, subjected to geochemical analyses, and then, few representative samples subjected to additional high-resolution mineralogical studies. However, the choice in samples is frequently subjective and the mineralogical analyses are highly time-consuming. In order to optimize the choice of samples and accelerate the analyses, drill-cores can be partitioned into domains, and then, laboratory analyses can be carried out on selected domains. Nevertheless, in the mining industry, automatic drill-core domaining still remains a challenge. Recently, hyperspectral imaging has become an important technique for the analysis of drill-cores in a non-invasive and non-destructive manner. Several clustering algorithms of hyper-spectral data are proposed for automatic drill-core domaining. In this paper, we suggest using advanced subspace clustering algorithms (i.e., sparse subspace clustering algorithm, spectral-spatial sparse subspace clustering algorithm). These algorithms work based on the self-representation property of the hyperspectral data. The clustering methods are tested on two drill-core samples which present different mineralogical and structural features. The subspace clustering algorithms are compared with the result of the K-means clustering algorithm. Our experimental results show that subspace clustering algorithms provide accurate drill-core domains and it is shown that including spatial information significantly improves the clustering results.
Keywords: Clustering algorithms, Hyperspectral imaging, Veins, Minerals, Signal processing algorithms, Clustering methods
  • Contribution to proceedings
    2019 10th Workshop on Hyperspectral Imaging and Signal Processing: Evolution in Remote Sensing (WHISPERS), 24.-26.09.2019, Amsterdam, Netherlands

Permalink: https://www.hzdr.de/publications/Publ-30688
Publ.-Id: 30688


A subspace clustering algorithm with spatial regularization for mineral mapping.

Rafiezadeh Shahi, K.; Khodadadzadeh, M.ORC; Tolosana Delgado, R.ORC; Gloaguen, R.ORC
Determination of the mineral compositions of an ore deposit is a vital task in exploration campaigns. HyperSpectral (HS) imaging is an emerging technology that is becoming popular in the mining industry. Specially, analyzing drill core HS data enables geologists to map minerals in mining projects in a fast and non-destructive manner. There are several methods to analyze the acquired drill cores. While traditional approaches such as X-Ray diffraction (XRD) can be subjective and are time consuming, the new machine learning based techniques applied on drill core HS scans have shown promising results. By using machine learning techniques, geologists are able to identify representative areas of drill core samples to apply traditional laboratory analysis.In recent studies, advanced unsupervised learning techniques to cluster HS data have shown great performance. Specially subspace clustering methods (i.e., sparse subspace clustering, low rank representation clustering) obtained more accurate results than the traditional clustering methods (e.g. K-means) for the analysis of this data. This is mainly because of the fact that each pixel may contain several minerals rather than a single phase. Therefore, the drill core HS data can be better represented as a union of low dimensional subspaces.In this work, we propose a new subspace-based method to cluster drill core HS data. It has been shown in the literature that incorporating spatial information will improve the classification results of HS data. Thus, in this work, we suggest including spatial information in the sparse subspace clustering method. In the classical sparse clustering method, only spectral information being used to cluster HS data. While, by adding information from the surrounding of each pixel in the classical sparse formula, the performance of the subspace clustering method will be improved. The method was applied to VNIR-SWIR hyperspectral data. Qualitative validation was provided by scanning electron microscopy based Mineral Liberation Analysis (SEM-MLA) on some areas of interest. Results indicate that the proposed method is promising, compared to existing clustering methods
Keywords: PIXELS, DRILL cores, REGULARIZATION (Mathematics), ORE deposits, SCANNING electron microscopy, MINERAL analysis
  • Open Access Logo Contribution to proceedings
    EGU General Assembly 2019, 07.-12.04.2019, Vienna, Austria
    Geophysical Research Abstracts

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Permalink: https://www.hzdr.de/publications/Publ-30686
Publ.-Id: 30686


UAS aeromagnetic survey and hyperspectral data for mineral exploration

Madriz Diaz, Y. C.; Jackisch, R.ORC; Zimmermann, R.ORC; Gloaguen, R.ORC
Geophysical methods for mineral exploration require cost- and time-effective ways to acquire high resolution data to supplement field mapping. During the last few years, lightweight magnetometers and hyperspectral imaging (HSI) sensors have been increasingly and independently developed for their use on unmanned aerial systems (UAS). We propose that the combination of hyperspectral images and UAS aeromagnetic surveys can provide a rapid and cost-effective technology to improve the detection of shallow targets and to delineate mineral structures in potentially hazardous terrains where traditional techniques cannot be operated safely. With low altitude flights and tight flight lines, UAS aeromagnetic surveys can help overcome the scale gap between ground and air-borne magnetics and deliver high resolution maps. However, data corrections are required for UAS aeromagnetic data to achieve valid observations and reliable maps. For this study the main magnetic compensations applied to the magnetics were meant to attenuate temporal variations, headings and maneuvering errors. The interpretation of accurate total field maps can be improved with the aid of hyperspectral images. HSI are widely used in geological mapping and mineral exploration (e.g., van der Meer et al., 2012, Jakob et al., 2016). A comprehensive data set including hyperspectral images and handheld spectral measurements of the study area in Siilinjärvi, Finland, was acquired before the UAS aeromagnetic survey was performed. The UAS magnetics was acquired at 40 m height, with a line spacing of 20 m, covering an area of 3.894 ha.
Data processing of the UAS aeromagnetic data revealed the importance of making appropriate corrections for the reliability of the total magnetic intensity (TMI) and derived maps. Results suggest that UAS aeromagnetic data captured the main geological trends of the area by applying pertinent corrections. Aided by the HSI information, the sources of the magnetic anomalies were identified. A high magnetic contrast created by a syenite intrusion located in a glimmeritic carbonatite complex is consistently delineated by the UAS aeromagnetic data. Outcropping areas of the syenite intrusion can also be identified in the available hyperspectral image of Siilinjärvi.
Keywords: Airborne magnetics, magnetometer, hyperspectral, mineral exploration, UAS
  • Open Access Logo Invited lecture (Conferences)
    AGU-SEG Airborne Geophysics Workshop, 11.-13.06.2019, Davie, Florida, United States

Permalink: https://www.hzdr.de/publications/Publ-30684
Publ.-Id: 30684


UAS aeromagnetic survey for mineral exploration using a fluxgate triaxial magnetometer.

Madriz Diaz, Y. C.; Jackisch, R.ORC; Zimmermann, R.ORC; Gloaguen, R.ORC
Unmanned aerial systems (UASs) for aeromagnetic surveying are currently an advantageous and suitable alternative for a large variety of geophysical applications, such as mineral exploration. UASs equipped with lightweight fluxgate magnetometers can rapidly provide high resolution magnetic data under conditions where traditional surveys cannot operate safely. Furthermore, UAS-borne magnetic acquisition offer a new mapping scale to overcome the gap between terrestrial and manned airborne surveys in a cost-effective way. However, there are several sources of magnetic interferences that compromise the measurements of the Earth's magnetic field, affecting the validity of observations and causing the development of unreliable maps. We address magnetic interference at the initial stages of survey planning and later on during processing. Fluxgate triaxial magnetometers can simultaneously measure the three components of the geomagnetic field but the sensor must be oriented and the heading of the aircraft plays an important role. To characterize the heading error it was essential to perform a compensation test including the possible flight directions before or after survey acquisition. To best adjust to the specific conditions of this case study, a processing tool was designed and programmed to compute suitable corrections and attenuate magnetic interferences. The three main corrections applied to the data included the removal of temporal variations, maneuvering noise and heading errors.
To test the potential of UAS for mineral exploration we selected a former mine in Otanmäki, Finland, as study site. To explore the contribution of low altitude UAS flights to characterize and improve the detection of geological structures, the study area was surveyed at three different heights: 60 m, 40 m and 15 m. For validation purposes, previous aeromagnetic studies in the area were employed, among them a ground magnetic survey. With regards to the efficiency of the UASs for aeromagnetic surveying it is worth mentioning that none of the flights lasted more than 15 minutes. The validation revealed that the total magnetic field maps consistently delineate the iron-ilmenite-magnetite deposits that enclose the test area. As expected, the superior spatial resolution was reached by the 15 m flight survey. Corrections played an important role during data processing. Nevertheless magnetic interference by heading errors was crucial for the reliability of this study. Our results suggest that after applying the pertinent magnetic compensations, UAS aeromagnetic surveys constitute a robust tool for mineral exploration.
Keywords: Unmanned aircraft systems, Magnetic survey, Magnetometer, Airborne surveying
  • Invited lecture (Conferences)
    EGU General Assembly 2019, 08.-12.04.2019, Wien, Austria

Permalink: https://www.hzdr.de/publications/Publ-30680
Publ.-Id: 30680


CFD modelling of the combustion and heat transfer in the Top-Submerged-Lance smelter

Reuter, M.ORC; Obiso, D.; Stelter, M.; Kriebitzsch, S.
The growth outlook for the circular economy in the metallurgical industry has to be built on the deep knowledge of the secondary processes involved in the chain: metal recycling and waste recov-ery play a significant role to successfully close the loop in the metal cycle.
The top-submerged-lance (TSL) furnace technology, primarily designed for metal extraction, is gradually making headway on that perspective because of its technical and economical flexibility. To push the market in that direction, an intense research effort has to be put in the understanding of the fundamentals, from chemical-physical to the engineering aspects.
In the present work, the authors investigate the lance combustion and the heat transfer in a TSL fur-nace. The submerged combustion is a crucial aspect of this technology. The correct design and ap-plication of the lance and the appropriate gas flow conditions must ensure a well-defined value of the partial pressure of oxygen pO2, which drives the smelting reaction process of the mineral con-centrate in the liquid slag bath.
A CFD investigation of the lab-scale TSL furnace, located at TU Bergakademie Freiberg, is per-formed using ANSYS Fluent®: the furnace setup includes the submerged combustive injection into a Cu-slag bath, in absence of the concentrate stream. The analysis provides detailed insights of the fuel combustion and the interaction with the liquid slag. Besides that, the evaluation of the pO2 at the lance tip and the temperature distribution in the bath and in the lance wall represent an added value for the furnace controlling and optimization.
Keywords: TSL smelting, submerged combustion, CFD, pyrometallurgy
  • Poster
    TMS - The Mineral Society Annual Meeting, 10.-14.03.2019, San Antonio, Texas, Texas, USA

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Permalink: https://www.hzdr.de/publications/Publ-30678
Publ.-Id: 30678


Line-scan detection system to identify rare earth elements in rocks

Abend, T.; Sharma, S. K.; Fuchs, M.; Beyer, J.; Heitmann, J.; Gloaguen, R.
We develop an integrated sensor system to detect rare earth elements (REE) in natural minerals on-site. The system combines reflectance and photoluminescence (PL) spectroscopy in order to present a noninvasive alternative to conventional time-consuming and costly chemical analysis of drill cores in mineral exploration. The major benefit lies in the rapid gathering of continuous spatial information on the type and abundance of the REEs in drill cores. Additionally the sample material remains unharmed during the whole process. To maximise scan speed and sample throughput, our system operates in continuous line scan mode, with continuous sample flow beneath the detector.
Keywords: Photoluminescence (PL); rare earth elements (REE); line-scan; system integration
  • Lecture (Conference)
    IEEE Sensors 2019, 27.-30.10.2019, Montreal, Canada

Permalink: https://www.hzdr.de/publications/Publ-30677
Publ.-Id: 30677


Ice Complex formation on Bol’shoy Lyakhovsky Island (New Siberian Archipelago, East Siberian Arctic) since about 200 ka

Wetterich, S.; Rudaya, N.; Kuznetsov, V.; Maksimov, F.; Opel, T.; Meyer, H.; Guenther, F.; Bobrov, A.; Raschke, E.; Zimmermann, H.; Strauss, J.; Starikova, A.; Fuchs, M.; Schirrmeister, L.
Late Quaternary landscapes of unglaciated Beringia were largely shaped by ice-wedge polygon tundra. Ice Complex (IC) strata preserve such ancient polygon formations. Here we report on the Yukagir IC from Bol'shoy Lyakhovsky Island in northeastern Siberia and suggest that new radioisotope disequilibria (230Th/U) dates of the Yukagir IC peat confirm its formation during the Marine Oxygen Isotope Stage (MIS) 7a–c interglacial period. The preservation of the ice-rich Yukagir IC proves its resilience to last interglacial and late glacial–Holocene warming. This study compares the Yukagir IC to IC strata of MIS 5, MIS 3, and MIS 2 ages exposed on Bol'shoy Lyakhovsky Island. Besides high intrasedimental ice content and syngenetic ice wedges intersecting silts, sandy silts, the Yukagir IC is characterized by high organic matter (OM) accumulation and low OM decomposition of a distinctive Drepanocladus moss-peat. The Yukagir IC pollen data reveal grass-shrub-moss tundra indicating rather wet summer conditions similar to modern ones. The stable isotope composition of Yukagir IC wedge ice is similar to those of the MIS 5 and MIS 3 ICs pointing to similar atmospheric moisture generation and transport patterns in winter. IC data from glacial and interglacial periods provide insights into permafrost and climate dynamics since about 200 ka.
Keywords: Cryostratigraphy, ice wedges, stable isotopes, pollen, radioisotope disequilibria dating, Beringia

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-30675
Publ.-Id: 30675


Geochemical Characterization of Tea Leaves (Camellia sinensis) and Soils for Provenance Studies based on Compositional Data Analysis

Pospiech, S.ORC
Provenance studies on tea (Camellia sinensis) are an important tool to reconstruct the origin of tea products. This thesis explores the potential of using solely the ionome (main and trace element concentrations) of tea shoot tips for provenance studies. The emphasize of the thesis is to find element subcompositions which are robust in respect to the various parameters of tea cultivation and production, such as the area, their soils, soil fertilizer and applications of foliar sprays, tea cultivars, plucking/harvesting techniques, manufacturing or leaf grade of the processed tea. For specific discrimination tasks these robust subcompositions can be combined with element subcompositions which are sensitive to one or several tea cultivation and production parameters. The data set consists of ca. 300 leaf and processed tea samples and ca. 130 soil samples. The sampling areas are located in Darjeeling, Assam and Nilgiris in India, in Paraná and São Paulo in Brazil and in Uji and Shizuoka in Japan. All samples, plants and soils, had been treated with four acid digestion methods with HNO3, HCl, HClO4 and HF to achieve a total dissolution. The sample solutions had been analyzed by ICP-MS and ICP-OES. The element concentrations of the leaf and processed tea samples had been corrected for adhering (soil) particles. Hence, all statistical analysis are based on the corrected concentrations values of Al, Ba, Ca, Cd, Co, Cr, Cs, Cu, Fe, K, La, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, S, Sb, Sc, Sr, Tl, Y and Zn. The element concentrations are converted into log-ratios by additive, centered or isometric log-ratio transformations prior to statistical analysis to avoid spurious correlations and to enhance the signal-noise ratio for e.g. the trace elements concentrations. The comparison of the geochemical composition of topsoils, subsoils, mature leaves, shoot tips and processed tea samples is used to establish for each element a qualitative index of robustness with respect to cultivation and production parameters. The elements with a high robustness are considered as very suitable for a provenance analysis without further knowledge about the tea samples. The thesis exemplary shows that with already small element subcompositions a good discrimination by geographical origin is possible if the elements are chosen in terms of their suitability for provenance studies of tea including their sensitivity in respect to specific parameters. The geological source rocks of the tea plantations is one of the major factors for discrimination of tea origin.
Keywords: tea; Camellia sinensis; compositional data; soil-plant interaction; plant analysis; plant ionom; provenance; Darjeeling
  • Doctoral thesis
    Georg-August-Universität Göttingen, 2019
    Mentor: Prof. H. Ruppert
    267 Seiten

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Permalink: https://www.hzdr.de/publications/Publ-30674
Publ.-Id: 30674


TWEAC - Energy-efficient Laser-plasma acceleration beyond the dephasing and depletion limits

Debus, A.ORC; Pausch, R.ORC; Hübl, A.ORC; Steiniger, K.ORC; Widera, R.ORC; Cowan, T.ORC; Schramm, U.ORC; Bussmann, M.ORC
We present Traveling-Wave Electron Acceleration (TWEAC), a novel compact electron accelerator scheme based on laser-plasma acceleration. While laser-plasma accelerators provide multi-GeV electron beams today, the acceleration to higher energies is limited. The sub-luminal group-velocity of plasma waves let electrons outrun the accelerating field.

In order to control the speed of the accelerating plasma cavity, TWEAC utilizes two pulse-front tilted laser pulses whose propagation directions enclose an acute 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. Thus, TWEAC offers constant acceleration without a dephasing electron beam while avoiding usual laser pump depletion within the interaction region. This opens the way for electron energies beyond 10 GeV, possibly towards TeV class electron beams, without the need for multiple laser-accelerator stages.

In this poster we study the energy efficiency of TWEAC compared to LWFA. We find that for low-angle TWEAC setups, it is possible to accelerate high-charge bunches with laser to electron beam energy efficiencies close to 50%, which exceeds energy efficiencies typically attained with LWFA.
Keywords: Laser-produced plasmas, Plasma-based accelerators, Laser-wakefield acceleration, Traveling-wave electron acceleration, TWEAC
  • Poster
    5. Annual MT Meeting, 05.-7.3.2019, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30673
Publ.-Id: 30673


Scaling EUV and X-ray Thomson Sources to Optical Free-Electron Laser Operation with Traveling-Wave Thomson-Scattering

Debus, A.ORC; Steiniger, K.ORC; Albach, D.ORC; Bussmann, M.ORC; Löser, M.ORC; Pausch, R.ORC; Röser, F.; Schramm, U.ORC; Siebold, M.
Traveling-Wave Thomson-Scattering (TWTS) is a novel Thomson scattering geometry which allows for orders of magnitude higher photon yields than classic head-on Thomson sources. TWTS thereby remains compact and provides narrowband and ultra-short ultraviolet to γ-ray radiation pulses just as classic Thomson sources. Even the realization of optical free-electron lasers is possible with the TWTS geometry since it provides both optical undulators with thousands of periods needed to microbunch the electron beam and a reduction of electron beam quality requirements compared to classic Thomson scattering to a level technically feasible today. TWTS employs a side-scattering geometry depicted in fig. 1. Laser and electron propagation direction of motion enclose the interaction angle ϕ. Tilting the laser pulse front with respect to the wave front by half the interaction angle ensures continuous overlap of electrons and laser pulse over the whole laser pulse width while the laser pulse crosses the electron beam trajectory. In this way the interaction length becomes controllable by the laser pulse width and independent of the laser pulse duration. Utilizing wide, petawatt class laser pulses for TWTS allows to realize thousands of optical undulator periods. The variability of TWTS with respect to the interaction angle can be used to control the radiation wavelength even for electron sources with fixed energy. For a fixed target wavelength on the other hand, the free choice of interaction angle enables control over electron beam quality requirements. Small interaction angle scenarios (ϕ∼10°) typically yield the best trade-off between requirements on electron beam quality, laser power and laser intensity stability. In the talk we will show that TWTS OFELs emitting extreme ultraviolet radiation are realizable today with existing technology for electron accelerators and laser systems. We detail an experimental setup to generate the tilted TWTS laser pulses which aims at compactness and provides focusing of these high-power pulses and compensation of dispersion accompanying pulse-front tilts. The method presented for dispersion compensation is especially relevant when building high yield X- and γ-ray sources in large interaction angle setups of TWTS.
Keywords: optical FEL, traveling-wave, Thomson scattering, pulse-front tilt, out-of-focus interaction, EUV, X-ray
  • Poster
    5. Annual MT Meeting, 05.-7.3.2019, Helmholtz Institut Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30670
Publ.-Id: 30670


Influence of LWFA injection schemes on temporal pulse structure and peak current

Debus, A.ORC; Zarini, O.ORC; Laberge, M.; Couperus Cabadağ, J. P.ORC; Köhler, A.ORC; Kurz, T.ORC; Schöbel, S.; Krämer, J.; Hannasch, A. J.; Zgadzaj, R.; Mewes, H.; Meißner, H.; Bussmann, M.ORC; Downer, M.; Schramm, U.ORC; Irman, A.ORC
Laser wakefield accelerators (LWFA) feature unique electron bunch characteristics, namely micrometer beam size with duration ranging from a few fs to tens of fs. Precise knowledge of the longitudinal profile of such ultra-short electron bunches is essential for the design of future table-top x-ray light-sources.
Spectral measurements of broadband transition radiation from LWFA electron bunches passing through a metal foil are especially promising for non-destructively analyzing ultrashort longitudinal bunch characteristics with single-shot capability.

Our broadband, single-shot spectrometer combines the TR spectrum in UV/VIS (200-1000nm), NIR (0.9-1.7μm) and mid-IR (1.6-12μm). A complete characterization and calibration of the spectrometer have been done with regard to wavelengths, relative spectral sensitivities, and absolute photometric sensitivity. Our spectrometer is able to characterize electron bunches with charges as low as 1 pC and resolve time-scales from 0.4 to 40 fs. In addition, complementary data on the transverse bunch profile is provided by simultaneously imaging the CTR in the far- and near-field.

We present recent experimental results of different LWFA injection mechanisms, such as self-truncated ionization-injection and self-injection. By analyzing the transition radiation spectra and reconstructing electron bunch profiles including error analysis, we determine electron bunch profiles and peak currents of the respective injection regimes. In addition to bunch durations and peak currents, we show sub-fs beam micro-structures and systematic experimental scans of the nitrogen doping concentration for ionization-induced injection.
Keywords: LWFA, Laser-wakefield acceleration, peak current, injection scheme, broadband spectrometer, single-shot bunch length measurement, coherent transition radiation, absolute calibration, electron bunch duration, longitudinal profile, absolute calibration, UV, VIS, NIR, MIR
  • Lecture (Conference)
    5. Annual MT Meeting, 05.-7.3.2019, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30669
Publ.-Id: 30669


Scalable laser-plasma acceleration using Traveling-Wave Electron Acceleration

Debus, A.ORC; Pausch, R.ORC; Hübl, A.ORC; Steiniger, K.ORC; Widera, R.ORC; Cowan, T.ORC; Schramm, U.ORC; Bussmann, M.ORC
While laser-plasma accelerators provide multi-GeV electron beams today, the acceleration to higher energies is limited. The sub-luminal group-velocity of plasma waves let electrons outrun the accelerating field. We present Traveling-Wave Electron Acceleration, a novel compact laser-plasma accelerator scheme which circumvents the LWFA constraints of electron beam dephasing, laser pulse diffraction and depletion.

For controlling the speed of the accelerating plasma cavity, TWEAC utilizes two pulse-front tilted lasers 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. Such guiding-structure-free, lateral coupling of lasers into the plasma allows the field within this overlap region to be continuously replenished by the successive parts of the laser pulse. Supported by 3D particle-in-cell simulations, we show that this leads to quasi-stationary acceleration conditions for electron bunches along the total acceleration length, such that TWEAC is in principle scalable to arbitrarily long acceleration stages.

We discuss scaling laws and detail experimental design considerations. We find that for low-angle TWEAC setups, it is possible to accelerate nanocoulomb-class bunches with laser to electron beam energy efficiencies close to 50%, thus exceeding energy efficiencies typically attained with LWFA.
Keywords: Laser-produced plasmas, Plasma-based accelerators, Laser-wakefield acceleration, Traveling-wave electron acceleration, TWEAC
  • Lecture (Conference)
    4th European Advanced Accelerator Concepts Workshop (EAAC 2019), 15.-21.9.2019, La Biodola Bay, Isola d'Elba, Italy

Permalink: https://www.hzdr.de/publications/Publ-30668
Publ.-Id: 30668


Modeling the L|PWFA hybrid accelerator using PIConGPU

Debus, A.ORC; Pausch, R.ORC; Steiniger, K.ORC; Hübl, A.ORC; Widera, R.ORC; Kurz, T.ORC; Schöbel, S.; Chang, Y.-Y.; Couperus Cabadağ, J. P.ORC; Köhler, A.ORC; Heinemann, T.; Ding, H.; Döpp, A.; Giljohann, M.; Kononenko, O.; Gaurav, R.; Corde, S.; Hidding, B.; Karsch, S.; Martinez De La Ossa, A.; Irman, A.ORC; Schramm, U.ORC
The hybrid L|PWFA acceleration scheme combines laser- (LWFA) with plasma-wakefield acceleration (PWFA) to provide an ultra-compact, high-brightness electron source. Recently, the acceleration of a witness bunch using this hybrid scheme was demonstrated at HZDR. In this talk, we present recent start-to-end simulations, that accompanied the experimental campaign, and provided fundamental insights into the injection and acceleration process of this novel, compact accelerator. These accompanying simulations were performed using the 3D3V particle-in-cell code PIConGPU. A significantly enhanced agreement between theoretical predictions and experimental measurements could be achieved by resembling the experiment to a very high degree. Modeling the geometry, density distributions, laser modes, and gas dopings as measured in the experiments provided good comparability between experiment and simulation. With that degree of agreement, the wealth of information provided by the in-situ data analysis of PIConGPU provided insight into the plasma dynamics, otherwise inaccessible in experiments. The talk will not only focus on explaining the fundamental physical process behind this hybrid scheme but will further elaborate on the essential details that produce the quasi-monoenergetic witness bunches seen in experiment. Furthermore, we will discuss the associated challenges in maintaining numerical stability and experimental comparability of these long-duration simulations.
Keywords: LWFA, PWFA, laser wakefield acceleration, plasma wakefield acceleration, particle-in-cell simulations, PIC, hybrid L|PWFA, start-to-end simulation
  • Lecture (Conference)
    4th European Advanced Accelerator Concepts Workshop (EAAC 2019), 15.-21.9.2019, La Biodola Bay, Isola d'Elba, Italy

Permalink: https://www.hzdr.de/publications/Publ-30667
Publ.-Id: 30667


A spectral library for Smithsonian rare-earth element phosphate standards using laser-induced fluorescence

Fuchs, M.; Beyer, J.; Lorenz, S.; Sharma, S.ORC; Renno, A.ORC; Heitmann, J.; Gloaguen, R.ORC
Innovation in raw material exploration relies on efficient and non-invasive technologies. Spectroscopy based methods have proven great potential to deliver instant and spatially continuous information on the composition of an investigated surface. Several studies successfully applied laser-induced fluorescence (LIF) for rare-earth element (REE) identification in natural rocks. However, the diagnostic assignment of detected emission lines remains a complex task, because of the highly variable composition of natural rocks. It needs a transfer of the profound knowledge from the field of applied physics and synthetic materials to the natural rock material under investigation. The evaluation of measured spectra and robust assignment of REEs requires reference data, yet usually based on tables of published emission lines, while data of complete reference spectra are not available.
We present a library of reference spectra for all luminescent rare-earth elements using the Smithsonian rare-earth phosphate standards for electron microprobe analysis. We employ laser-induced fluorescence at three commonly used laser wavelengths (325 nm, 442 nm, 532 nm) to acquire reference spectra for REE phosphate minerals in the visible to near-infrared spectral range (350 – 1080 nm). Excitation at all three laser wavelengths yielded spectra with distinct REE-related emission lines for EuPO4, TbPO4, DyPO4 and YbPO4. Lower energy laser excitation at 442 nm showed successful especially for suppressing non-REE-related broadband defect emission. Resulting REE-reference spectra include those from PrPO4, SmPO4 and ErPO4. For NdPO4 and HoPO4 most efficient excitation was achieved with 532 nm. The diagnostic emission lines of GdPO4 lie outside the detection range and none of the three laser wavelengths was appropriate for TmPO4 excitation.
Our results demonstrate the suitability of LIF for REE detection and especially the possibility of selective element excitation. Our reference spectra provide the full spectral information at high resolution (0.13nm) as a basis for an improved evaluation of REE-bearing natural rocks allowing for data analysis of emission line positions, emission line intensity ratios and splitting into emission line sub-levels. The spectral library data support the use of LIF for REE analysis in natural samples and its application in raw material exploration.
Keywords: spectroscopy, laser-induced fluorescence, rare-earth elements
  • Open Access Logo Contribution to proceedings
    European Geoscience Union, 12.04.2019, Vienna, Austria

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Permalink: https://www.hzdr.de/publications/Publ-30666
Publ.-Id: 30666


Erfassung hydrodynamischer Kenngrößen in großen Prozessbehältern mittels instrumentierter Strömungsfolger

Hampel, U.
This keynote presentation introduces the concept of instrumented flow followers for determination of hydrodynamic parameters in large process vessels. Instrumented flow followers are medium size particles that drift with the flow in a vessel. They actively adjust buoyancy with an electromechanical mechanisms and comprise sensors for temperature, pressure, acceleration and further parameters. Furthermore, novel concepts of data transfer, communication and positioning are being presented.
Keywords: instrumented flow followers, autonomous sensors, process measurement, process engineering
  • Invited lecture (Conferences)
    Campus Mehrphasenreaktoren, 31.01.2020, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30665
Publ.-Id: 30665


Metallurgy: key enabler of the Circular Economy HSC Sim as a tool for the analysis of large CE SYSTEMS

Reuter, M. A.
The complexity of metal and material mixtures in products
Simulation-based quantification of the resource efficiency of very large - Circular Economy (CE) systems
Various industrial examples for footprinting the CE e.g.
Copper rock to metal – exergy dissipation of the system
PV life cycle linked to energy system: exergy dissipation in the system
Zinc and lead processing systems
Product design for circularity for OEMs (mobile, LED, laptops etc.)
Battery recycling,
Water systems optimization, and
…many more, also developed during my time @ Outotec, also in client solution development, sales, etc.
Challenges?
Too many not yet accepting the above state-of-the-art in the CE discussion, leading to critical and sub-optimal discussions, policy, etc.
Keywords: Circular Economy, resource efficiency, HSC
  • Lecture (others)
    Outotec celebrates 70 years of technology innovation at Pori ORC, 15.-16.10.2019, Pori, Finnland

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Permalink: https://www.hzdr.de/publications/Publ-30662
Publ.-Id: 30662


Challenges of the circular economy - A metallurgical perspective

Reuter, M. A.
Circular economy's (CE) noble aims maximize resource efficiency (RE) by, for example, extending product life cycles and using wastes as resources. Modern society's vast and increasing amounts of waste and consumer goods, their complexity, and functional material combinations are challenging the viability of the CE despite various alternative business models promising otherwise. The metallurgical processing of CE-enabling technologies requires a sophisticated and agile metallurgical infrastructure. The challenges of reaching a CE are highlighted in terms of, e.g., thermodynamics, transfer processes, technology platforms, digitalization of the processes of the CE stakeholders, and design for recycling (DfR) based on a product (mineral)-centric approach, highlighting the limitations of material-centric considerations. Integrating product-centric considerations into the water, energy, transport, heavy industry, and other smart grid systems will maximize the RE of future smart sustainable cities, providing the fundamental detail for realizing and innovating the United Nation's Sustainability Development Goals.
Keywords: circular economy, process metallurgy, thermoeconomics, exergy, design for recycling
  • Lecture (others)
    10. Scientific Exchange Day 2019, 07.02.2019, Linz, Österreich

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Permalink: https://www.hzdr.de/publications/Publ-30661
Publ.-Id: 30661


Metallurgical Recycling infrastructure of THE circular economy (CE)

Reuter, M. A.
Circular Economy (CE)
Digitalization in the metallurgical industry within the CE system
Metallurgical reactor technology
Design for recycling
Various literature and other detail
Keywords: Circular Economy, HSC, Copper, energy & resource efficiency,
  • Lecture (others)
    Atlantic Copper Meeting, 13.12.2019, Madrid, Spanien

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Permalink: https://www.hzdr.de/publications/Publ-30660
Publ.-Id: 30660


Steigender Energieaufwand bei der Gewinnung von Metallen – Möglichkeiten und Grenzen des Metallrecyclings

Reuter, M. A.
Ein Abschied ist zugleich ein Neuanfang. Der Ausstieg aus den fossilen Energieträgern ist klimapolitisch überfällig. Das aktive Phase-Out des fossilen Erdöls erfordert zugleich einen Einstieg, ein aktives Phase- In von noch mehr Metallen. Beides, Einstieg und Ausstieg, zusammenzuhalten ist der Schwerpunkt unserer Veranstaltung.

Auch das postfossile Zeitalter braucht Energie. Der Ersatz für die fossilen Energieträger beim Übergang zu regenerativen Energien sind die mehr als ausreichenden Energieströme von der Sonne. Zukünftig primäre Bedeutung wird daher die Elektroenergie haben. Für die Energiewende brauchen wir mehr Metalle: Ob klassische Basismetalle wie Kupfer oder etwa Seltenerdmetalle wie Neodym für die Permanentmagneten moderner Windkraftanlagen. Auch die Mobilitätswende erfordert eine zunehmende Elektrifizierung des motorisierten Straßenverkehrs, sei es direktelektrisch oder mit Wasserstoff / Brennstoffzelle. Mit der Digitalisierung kommt nochmals eine weitere Dimension an Metallbedarf auf uns zu. Metalle sind die Voraussetzung für die Energiewende, die Mobilitätswende und die digitale Transformation. Dazu braucht es alle Metalle im Periodensystem – wir sind im „All Metals Age“ angekommen.

Es geht dabei nicht nur um Lithium, um Kobalt, wozu gelegentlich Meldungen aufgrund von Menschenrechtsverletzungen und Auseinandersetzungen im Kongo bei uns aufschlagen. Oder nur um Seltenerdmetalle, die im Handelskonflikt zwischen den USA und China eine starke Stellung Chinas signalisieren. Wir brauchen ein umfassendes Problemverständnis für die Metalle.

Der klimapolitisch überfällige Übergang ist somit, recht betrachtet, einer vom Zugriff auf einen Bodenschatz zu einem anderen. Der Unterschied in den Eigenschaften dieser beiden Typen von Bodenschätzen wird die zukünftige Geschichte der Menschheit prägen, sowohl die wirtschaftliche als auch die politische. Im Gegensatz zum fossilen Erdöl können wir aus der Nutzung von Metallen nicht aussteigen.
Keywords: fossiles Erdöl, Metalle, Elektroenergie, Metalle, Kupfer, Seltenerdmetalle
  • Invited lecture (Conferences)
    Kobalt, Kupfer, Lithium & Co.: Phase-Out von Erdöl und Phase-In von Metallen, 21.-22.11.2019, Dresden, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-30659
Publ.-Id: 30659


Main technology trends in processing – Data integration of LCA, materials modelling, process flowsheets

Reuter, M. A.
The harmony and complexity of metal and material mixtures: Their value
Simulation-based quantification of the resource efficiency of very large - Circular Economy (CE) systems
Various industrial examples for understanding very large CE systems:
A policy brief informing society: Lead key enabler of the circular economy
Car recycling: Design for recycling SEAT
PV resource life cycle linked to energy system: Exergy dissipation in large systems
Various EU & EIT Rawmaterials projects as well as BMBF and B2B:
PreMa: Low CO2 production of FeMn, incl. solar heat
GUCCIS: Product design for circularity
B2B: Fairphone
Circular by Design: BMBF Germany
Submitted project: SiSal Pilot
INFACT: EU project
Keywords: Circular Economy, Car recycling, resource systems,
  • Invited lecture (Conferences)
    Innovation, new technology trends and Skills for Raw Materials“New technology trends in exploration, mining and processing, Skills for Raw Materials, Horizon 2020 Raw Materials Information and Brokerage Event”, 18.-22.11.2019, Brüssel, Belgien

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Permalink: https://www.hzdr.de/publications/Publ-30656
Publ.-Id: 30656


Laser-driven strong shocks with infrared lasers at intensity of 1016 W/cm2

Antonelli, L.; Trela, J.; Barbato, F.; Boutoux, G.; Nicolaï, P.; Batani, D.; Tikhonchuk, V.; Mancelli, D.; Tentori, A.; Atzeni, S.; Schiavi, A.; Baffigi, F.; Cristoforetti, G.; Viciani, S.; Gizzi, L. A.; Smid, M.ORC; Renner, O.; Dostal, J.; Dudzak, R.; Juha, L.; Krus, M.
We present the results of an experiment on laser-driven shock waves performed at the Prague Asterix Laser system (PALS), where the fundamental frequency of the laser (1315 nm) is used to launch a strong shock in planar geometry. The experiment aims to characterize both shock waves and hot electrons generated at intensities of ’ 1016 W=cm2 . It is shown that, in these interaction conditions, hydrodynamics is strongly impacted by noncollisional mechanisms, and the role of the hot electrons, generated by parametric instabilities, is essential in determining shock dynamics.

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Permalink: https://www.hzdr.de/publications/Publ-30655
Publ.-Id: 30655


Metallurgy as the key enabler in Circular Economy, and bottlenecks by REACH and other policies on metal banning

Reuter, M. A.
The complexity of metal and material mixtures in products
Simulation-based quantification of the resource efficiency of very large - Circular Economy (CE) systems
Various industrial examples for understanding very large CE systems e.g.
A policy brief informing society: Lead key enabler of the circular economy
PV life cycle linked to energy system: exergy dissipation in the system
Car recycling – design for recycling
Challenges?
Keywords: resource efficiency, Circular Economy, metallurgy, Socrates, recycling,
  • Invited lecture (Conferences)
    CICERONE - Funding the Circular Economy, 19.-20.11.2019, Berlin, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-30651
Publ.-Id: 30651


Spin dynamics in strongly-correlated spin systems: physics and methodology

Zvyagin, S.ORC
für diesen Vortrag hat keine inhaltliche Kurzfassung vorgelegen
  • Invited lecture (Conferences)
    Heinz Maier-Leibnitz Zentrum User Meeting, 10.-11.12.2019, Garching, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30650
Publ.-Id: 30650


Metall-Kreislaufwirtschaft - Potentiale und Grenzen // Smartphone: IconographiC example for digital transformation

Reuter, M. A.
The complexity of metal and material mixtures in products
Simulation-based quantification of the resource efficiency of very large Circular Economy (CE) systems
Various industrial examples for understanding very large CE systems e.g.
A policy brief informing society: Lead key enabler of the circular economy
PV life cycle linked to energy system: exergy dissipation in the system
Car recycling – design for recycling
Many more, also developed during my time @ Outotec, also in client solution development, sales, etc.:
Copper rock to metal – exergy dissipation of the system
Battery recycling
Zinc and lead processing systems
Product design for circularity for OEMs (mobile, LED, laptops etc.)
Water systems optimization e.g. on concentrator plants
Challenges?
Background information
Keywords: Circular Economy, SOCRATES, Recycling, footprint of minor metals, car recycling, emobility
  • Invited lecture (Conferences)
    Metalle – Voraussetzung der digitalen Transformation, 08.-09.11.2019, Tutzingen, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-30645
Publ.-Id: 30645


Smelters and refineries strategies to mitigate impact of minor metal increase in feed

Reuter, M. A.
The importance of metals in society /
The fundamental role of metals in a circular society /
Metallurgical infrastructure criticality in a circular society – recovering the minor elements /
Our actions as industry?
Keywords: circular society, emobility, recycling, circular economy, process metallurgy,
  • Invited lecture (Conferences)
    Third Minor Metal Symposium: Multi Metal Management and Sustainable Processing of Complex Sulfide Materials, 19.-21.10.2019, Lissabon, Portugal

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Permalink: https://www.hzdr.de/publications/Publ-30644
Publ.-Id: 30644


The eco-footprint of raw materials. Current limits.

Reuter, M. A.
The complexity of metal and material mixtures in products
Simulation-based quantification of the resource efficiency of very large - Circular Economy (CE) systems
Applying the tools of process metallurgy to quantify CAPEX and OPEX of CE system
Various industrial examples for footprinting the CE e.g.
PV life cycle linked to energy system: exergy dissipation in the system
Various other examples among many:
Copper rock to metal – exergy dissipation of the system (industry)
Product design for circularity for OEMs (mobile, LED, laptops etc.)
Water systems optimization (industry)
Zinc and lead processing systems (industry)
Challenges?
Keywords: ecological footprint, circular SOCIETY, emobility, resource efficiency, Circular Economy
  • Invited lecture (Conferences)
    4th Expert Forum on Sustainable Materials for Future Mobility/Electrification and Lightweight Design, 07.-09.10.2019, Nizza, Frankreich

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Permalink: https://www.hzdr.de/publications/Publ-30643
Publ.-Id: 30643


Numerical optimization of a finned tube bundle heat exchanger arrangement for passive spent fuel pool cooling to ambient air

Unger, S.; Krepper, E.; Beyer, M.; Hampel, U.ORC

This is the data set for the corresponding journal publication " Numerical optimization of a finned tube bundle heat exchanger arrangement for passive spent fuel pool cooling to ambient air".


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Numerical optimization of a finned tube bundle heat … (Id 29116) has used this publication of HZDR-primary research data
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-01-24
    DOI: 10.14278/rodare.235
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-30638
Publ.-Id: 30638


SPCI-Reconstruction

Kornek, D.; Berthold, J.; Kögler, T.ORC

Single plane Compton imaging (SPCI) is a novel approach to medical imaging of gamma radiation [1]. The possible range of applications includes nuclear imaging and range verification in proton therapy. For the purpose of image reconstruction, a software tool written in ROOT [2] and named SPCI-Reconstruction [3] has been developed. The implementation features the well-established MLEM algorithm for binned data [4] as well as a Monte-Carlo based algorithm called Origin Ensemble [5]. Given a precalculated system matrix and a file containing the measurements, the emission densities of the gamma radiation source can be backprojected into a voxel-based image space.

[1] Pausch G et al. A novel scheme of compton imaging for nuclear medicine. 2016 IEEE Nuclear Science Symposium, Medical Imaging Conference and Room-Temperature Semiconductor Detector Workshop (NSS/MIC/RTSD).

[2] CERN. ROOT – Data Analysis Framework. Release 6.12/04 - 2017-12-13. https://root.cern.ch/content/release-61204.

[3] Kornek D. Anwendung von Maximum-Likelihood Expectation-Maximization und Origin Ensemble zur Rekonstruktion von Aktivitätsverteilungen beim Single Plane Compton Imaging (SPCI). Master's thesis. TU Dresden. 2019.

[4] Shepp LA, Vardi Y. Maximum likelihood reconstruction for emission tomography. IEEE Trans Med Imaging. 1982; 1(2):113-22.

[5] Sitek A. Representation of photon limited data in emission tomography using origin ensembles. Phys Med Biol. 2008 June; 53(12):3201-3216.

Keywords: single plane compton imaging, compton camera, image reconstruction, maximum-likelihood expectation-maximization, origin ensemble, nuclear medicine, range verification in particle therapy
  • Software in the HZDR data repository RODARE
    Publication date: 2020-01-17
    DOI: 10.14278/rodare.191
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-30631
Publ.-Id: 30631


Process Metallurgy in Circular Economy System Design: Challenges & Solutions

Reuter, M. A.; Bartie, N.
Realising the circular economy (CE) is faced with some significant challenges. Process metallurgy and its infrastructure play key roles at the heart of making the CE work. Therefore, the enabling role of process metallurgy within the CE will be central to the discussion in this paper, touching among others on product and system design as well as the key metallurgical and other process fundamentals that need to be investigated and understood to make the CE a reality. The central role of materials and its processing will be discussed in an integrated circular cities perspective. A key focus will be a discussion on designing a resilient “Smart Materials Grid” using and innovating metallurgical process engineering tools, which will manage the flows through Sustainable Circular Cities. The discussion will be using copper as leitmotiv of the discussion i.e. from copper ore, to metal, to complex products, recycling, product design and simulation and its impact.
Keywords: circular economy, Process metallurgy, “Smart Materials Grid”, Sustainable Circular Cities
  • Invited lecture (Conferences)
    COM 2019 Hosting Copper 2019, 18.-21.08.2019, Vancouver, Canada

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Permalink: https://www.hzdr.de/publications/Publ-30630
Publ.-Id: 30630


Effects of He ion irradiation on gold nanoclusters: a Molecular Dynamics study

Ghaderzadeh, S.ORC; Ghorbani Asl, M.ORC; Kretschmer, S.ORC; Hlawacek, G.ORC; Krasheninnikov, A.ORC
The interpretation of helium ion microscopy (HIM) images of crystalline metal clusters requires microscopic understanding of the effects of He ion irradiation on the system, including energy deposition and associated heating, as well as channeling patterns. While channeling in bulk metals has been studied at length, there is no quantitative data for small clusters. We carry out molecular dynamics simulations to investigate the behavior of gold nano-particles with diameters of 5–15 nm under 30 keV He ion irradiation. We show that impacts of the ions can give rise to substantial heating of the clusters through deposition of energy into electronic degrees of freedom, but it does not affect channeling, as clusters cool down between consecutive impact of the ions under typical imaging conditions. At the same time, high temperatures and small cluster sizes should give rise to fast annealing of defects so that the system remains crystalline. Our results show that ion-channeling occurs not only in the principal low-index, but also in the intermediate directions. The strengths of different channels are specified, and their correlations with sputtering-yield and damage production is discussed, along with size-dependence of these properties. The effects of planar defects, such as stacking faults on channeling were also investigated. Finally, we discuss the implications of our results for the analysis of HIM images of metal clusters.
Keywords: Helium Ion Microscope, Channeling effect, Nano particles, Ion irradiation
  • Lecture (Conference)
    AVS 66th International Symposium & Exhibition, 20.-25.10.2019, Columbus, United States of America

Permalink: https://www.hzdr.de/publications/Publ-30629
Publ.-Id: 30629


Effects of gold nanoclusters under He ion irradiation: a molecular dynamics study

Ghaderzadeh, S.ORC; Ghorbani Asl, M.ORC; Hlawacek, G.ORC; Krasheninnikov, A.ORC
Ion channeling is a well-known effect in ion irradiation processes, which is a result of ion moving between the rows of atoms. It drastically affects the ion distribution, ion energy-loss and consequently the damage production in the target. Therefore one could derive the ion-channeling pattern out of the energy-loss behavior of ion-target interaction.
Ion channeling effect is studied for a few pure element crystals and also for some compounds in a systematic way [1]. In this work, we focus on nano-structures which are of major importance, due to their high surface-to-volume ratio. Our results, for different gold cluster sizes, show that ion-channeling occurs not only in the principal low-index, but also in other directions in between. The strengths of different channels are specified, and their correlations with sputtering-yield and damage production is discussed.
Keywords: Helium Ion Microscope, Nano particles, Channeling effect, Ion irradiation
  • Poster
    Towards Reality in Nanoscale Materials X, 12.-14.02.2019, Levi, Finland

Permalink: https://www.hzdr.de/publications/Publ-30627
Publ.-Id: 30627


Process Metallurgy is Fundamental to the Circular Economy

Reuter, M. A.
Metals are eminently recyclable, and by recycling and refining complex materials, the interconnected metals sector is responding to the increasing scarcity of certain metals. In this way, the metals sector is delivering and recovering the technology and base metals for the Circular Economy (CE). Moreover, metals are at the heart of the energy infrastructures that now run Circular Cities, and they will play an even greater part in the future. Metals are key enablers in the CE, as it is capable of dissolving and carrying a multitude of technology elements. The recovery and recycling of several critical technology elements is based on refining them from molten metal through well-developed metallurgical processes in which these act as carrier metals. To put it simply, process metallurgy is fundamental if countries want to innovate leading positions in the global CE. This presentation is gleaning from a recent policy brief developed by industry and academia within the EU ETN SOCRATES.
Keywords: Circular Economy, Circular Cities, process metallurgy, SOCRATES
  • Invited lecture (Conferences)
    Waste innovation for a circular economy / Cutting Edge Science and Engineering Symposium, 27.-29.05.2019, Clayton, Australien

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Permalink: https://www.hzdr.de/publications/Publ-30626
Publ.-Id: 30626


Traveling-Wave Electron Acceleration - Energy-efficient Laser-plasma acceleration beyond the dephasing and depletion limits

Debus, A.ORC; Pausch, R.ORC; Hübl, A.ORC; Steiniger, K.ORC; Widera, R.ORC; Cowan, T.ORC; Schramm, U.ORC; Bussmann, M.ORC
We present Traveling-Wave Electron Acceleration (TWEAC), a novel compact electron accelerator scheme based on laser-plasma acceleration. While laser-plasma accelerators provide multi-GeV electron beams today, the acceleration to higher energies is limited. The sub-luminal group-velocity of plasma waves let electrons outrun the accelerating field.

In order to control the speed of the accelerating plasma cavity, 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. Supported by 3D particle-in-cell simulations using PIConGPU, we show that TWEAC offers constant acceleration without a dephasing electron beam while avoiding usual laser pump depletion within the interaction region. This opens the way for electron energies beyond 10 GeV, possibly towards TeV class electron beams, without the need for multiple laser-accelerator stages. For lower GeV-scale electron energies, TWEAC at high plasma densities and 10TW-class laser systems could enable compact accelerators at kHz-repetition rates.

After analyzing stability of acceleration and possible limits of the scheme, we present energy scaling laws for both laser as well as electrons and detail experimental design considerations. By comparing the energy efficiency of various TWEAC designs to LWFA, we find using simulations that for low-angle TWEAC setups, it is possible to accelerate high-charge bunches with laser to electron beam energy efficiencies close to 50%, which exceeds energy efficiencies typically attained with LWFA.
Keywords: Laser-produced plasmas, Plasma-based accelerators, Laser-wakefield acceleration, Traveling-wave electron acceleration, TWEAC
  • Lecture (Conference)
    Laser-Plasma Accelerator Workshop 2019, 05.-10.5.2019, Split, Kroatien

Permalink: https://www.hzdr.de/publications/Publ-30624
Publ.-Id: 30624


Tomographic imaging of two-phase flow

Hampel, U.
The presentation gives an overview on the application of x-ray tomographic imaging for flow analysis in nuclear safety research. Its application is exemplified for two-phase flow imaging around a flow obstacle and gas holdup measurement in a heated rod bundle.
Keywords: tomographic imaging, X-ray tomography, two-phase flow, rod bundle
  • Lecture (Conference)
    3rd Sino-German Symposium on Fundamentals of Advanced Nuclear Safety Technology SG-FANS-3, 25.-27.09.2019, Xi'an, China

Permalink: https://www.hzdr.de/publications/Publ-30623
Publ.-Id: 30623


Determining impact of LWFA injection schemes on electron bunch profiles and peak currents based on broadband, spectral CTR diagnostics at single shot

Debus, A.ORC; Zarini, O.ORC; Laberge, M.; Couperus Cabadağ, J. P.ORC; Köhler, A.ORC; Kurz, T.ORC; Schöbel, S.; Kraemer, J.; Hannasch, A. J.; Zgadzaj, R.; Mewes, H.; Meißner, H.; Bussmann, M.ORC; Downer, M.; Schramm, U.ORC; Irman, A.ORC
Laser-wakefield accelerators (LWFA) feature electron bunch durations on a fs-scale. Precise knowledge of the longitudinal profile of such ultra-short electron bunches is essential for the design of future compact X-ray light sources. Resolution limits, as well as the limited reproducibility of electron bunches, pose big challenges for LWFA beam diagnostics.

Spectral measurements of broadband transition radiation from LWFA electron bunches passing through a metal foil are especially promising for analyzing ultrashort longitudinal bunch characteristics ranging from of tens of fs down to sub-fs.

Our broadband, single-shot spectrometer combines the TR spectrum in UV/VIS (200-1000nm), NIR (0.9-1.7μm) and mid-IR (1.6-12μm). A complete characterization and calibration of the spectrometer has been done with regard to wavelengths, relative spectral sensitivities and absolute photometric sensitivity. Our spectrometer is able to characterize electron bunches with charges as low as 1 pC and resolve time-scales from 0.7 to 40 fs. In addition, complementary data on the transverse bunch profile is provided by simultaneously imaging the CTR in the far- and near-field.

We present recent experimental results of different LWFA injection mechanisms, such as self-truncated ionization-injection and self-injection. By analyzing the transition radiation spectra and reconstructing electron bunch profiles including error analysis, we determine electron bunch profiles and peak currents of the respective injection regimes. In addition to bunch durations and peak currents, we discuss sub-fs beam micro-structures and systematic experimental scans of the nitrogen doping concentration for ionization-induced injection.
Keywords: LWFA, Laser-wakefield acceleration, peak current, injection scheme, broadband spectrometer, single-shot bunch length measurement, coherent transition radiation, absolute calibration, electron bunch duration, longitudinal profile, absolute calibration, UV, VIS, NIR, MIR
  • Lecture (Conference)
    Laser-Plasma Accelerator Workshop 2019, 05.-10.5.2019, Split, Kroatien

Permalink: https://www.hzdr.de/publications/Publ-30622
Publ.-Id: 30622


Imaging techniques for multiphase flows - Needs and recent developments

Hampel, U.
The presentation gives an overview over the state of the art in imaging techniques for multiphase flows in chemical engineering.
Keywords: imaging techniques, multiphase flow
  • Invited lecture (Conferences)
    Bernal Fluids Day, 26.06.2019, Limerick, Irland

Permalink: https://www.hzdr.de/publications/Publ-30621
Publ.-Id: 30621


Experimental analysis of reactive bubbly flows

Kipping, R.; Kryk, H.; Hampel, U.
Bubble column reactors are widespread in the chemical industry [1]. Hydrodynamics and mass transfer processes in bubble column reactors are difficult to predict, as they occur at different length and time scales. Thus, numerous parameters affect the performance of bubble column reactors in terms of yield and selectivity. These are the gas holdup, bubble size, bubble interfacial area, liquid-phase velocity, and mass transfer coefficients. In addition, the kinetics of the chemical reactions in a bubble column and the mixing of the reactants play a significant role and may even feedback on mass transfer and hydrodynamics. Within a German DFG Priority Programme we investigate the coupling between hydrodynamics, mass transfer and reaction in bubbly flows across the scales and with real chemical reaction systems [2]. Within this framework, our group studies the macroscale processes in laboratory bubble columns with selected experimental techniques. In our presentation, we will introduce two different ways for time-resolved local chemical species concentration measurement, i.e. the analysis of OH- consumption during chemisorption of CO2 in alkaline solution by electrochemical analysis using a wire-mesh sensor as well as chemical conversion of NO in Fe(II) (EDTA) solution with a fiber optical photospectrometry technique.
Keywords: bubble columns; mass transfer; chemical species concentration measurement
  • Lecture (Conference)
    Gas-Liquid and Gas-Liquid-Solid Reactor Engineering (GLS-14), 30.05.-03.06.2019, Guilin, China

Permalink: https://www.hzdr.de/publications/Publ-30620
Publ.-Id: 30620


Vacancy-Hydrogen Dynamics in Samples during Low Temperature Baking

Wenskat, M.; Bate, C.; Cizek, J.; Liedke, M. O.ORC; Butterling, M.; Hirschmann, E.; Wagner, A.ORC; Reschke, D.; Weise, H.
The recent discovery of a modified low temperature baking process established an increased accelerating gradient of TESLA shaped cavities through reduction of surface losses.
A possible explanation for the performance gain is the suppression of lossy nanohydrides via defect trapping, with vacancy-hydrogen (v+nH) complexes forming at the lower temperatures. Utilizing Doppler broadening Positron Annihilation Spectroscopy, Positron Annihilation Lifetime Spectroscopy and Nuclear Reaction Analysis, samples made from European XFEL niobium sheets and cavity cut-outs were investigated. The evolution of vacancies, hydrogen and their interaction at different temperature levels have been studied during in-situ and ex-situ annealing and in-situ cooldowns.
Measurements of niobium samples and a correlation between RF, material properties, and v+nH distribution in cavity cut-outs have been carried out.
Keywords: PAS, Nb, superconductivity, defects, hydrogen

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Permalink: https://www.hzdr.de/publications/Publ-30619
Publ.-Id: 30619


Evaluation of separation and segregation in dynamic air classifiers

Buchmann, M.; Mütze, T.
Dynamic air classifiers separate particles in a gas flow due to their different trajectories. The characteristic property of separation is the settling velocity of the particles which is influenced by their size, shape, and density. The present contribution takes a close look at the separation behaviour of heterogeneous feeds, in which valuables and gangue minerals show significant differences in density. A new concept of multi-dimensional characterization of a separation process is presented and compared to the classical approach of the evaluation by partition curves (split factor, cut size, separation efficiency etc.) The new concept utilises the complex information from an automated mineral liberation analysis (MLA) and provides information of the enrichment and segregation of individual mineral phases in the products.
  • Open Access Logo Contribution to proceedings
    16th European Symposium on Comminution & Classification (ESCC 2019), 02.-04.09.2019, Leeds, United Kingdom
    DOI: 10.5518/100/17

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Permalink: https://www.hzdr.de/publications/Publ-30617
Publ.-Id: 30617


Accelerated magnetic re-ordering in Ne+ irradiated FeAl thin films

Liedke, M. O.ORC; Ehrler, J.; Bali, R.; Butterling, M.; Hirschmann, E.; Wagner, A.ORC; Cizek, J.
Thermally activated (re)ordering processes in ferromagnetic Fe60Al40 thin films during in-situ annealing have been investigated by magnetometry and positron annihilation spectroscopy supported with atomic superposition calculations. A ferromagnetic A2-disordered phase coexists with a paramagnetic B2-ordered phase in the as-grown sputter deposited films. Due to thermal treatment at elevated temperature of 773K the B2-phase can be fully established. However, employing Ne+ irradiation as a tool to generate a pure A2-phase and subsequent mild temperature annealing the activation temperature for (re)ordering can be decreased to only 400K. It will be shown that due to immobile large vacancy clusters, which are dominant in the as-grown films and possess a high thermal activation barrier the ordering is strongly hindered.
Ion irradiation breaks down these pinning defects strongly accelerating thermal diffusion and reordering. These results provide insights into thermal reordering processes in binary alloys, and the consequent effect on magnetic behavior.
Keywords: positron annihilation spectroscopy, FeAl, AIDA, MePS, PALS, PAS
  • Lecture (Conference)
    DPG-Frühjahrstagung — Regensburg, 31.03.2019, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30616
Publ.-Id: 30616


Electrical field-controlled ON-OFF ferromagnetism in single metal oxide films

Liedke, M. O.ORC; Butterling, M.; Quintana, A.; Menéndez, E.; Hirschmann, E.; Sireus, V.; Nogués, J.; Sort, J.; Wagner, A.ORC; Elsherif, A. G. A.
With respect to applications, substituting electric currents, which are nowadays used to operate spintronic devices, with electric fields, would result in a reduction of both the energy consumption and cost [1]. Co3O4 is a candidate for a tunable, non-volatile energy-efficient functional material whose magnetic properties can be controlled by electric voltage. In our current investigations the as-grown Co3O4 films consist of a paramagnetic (PM) phase only, which is transformed to a ferromagnetic (FM) state by electrolyte-gated and defect-mediated O and Co transport. A negative voltage reduces Co3O4 to Co (FM: ON), resulting in a phase separated material with Co- and O-rich regions. Applying a positive bias, the process is reversed oxidizing Co back to Co3O4 (PM: OFF). We will show that atoms migration is driven by rather complex vacancy states and a clear increase of the grain boundaries volume after negative biasing assists to O transport. Moreover, concomitantly with the PM phase transition due to the positive biasing the structural defects picture reverses to a large extent as well, which manifests as reduction in volume of both vacancy clusters and grain boundaries. Doppler broadening and positron annihilation lifetime spectroscopy have been used as an in-situ probe of electric field driven ionic transport of Co and O via different type of defects in Co3O4 systems [2].
[1] Y. Shiota, et al. Nature Mater. 11, 39 (2012)
[2] A. Quintana, E. Menéndez, M. O. Liedke, M. Butterling, A. Wagner, et al. ACS Nano 12, 10291 (2018)
Keywords: positron, positron annihilation spectroscopy, AIDA, magnetism, voltage
  • Poster
    “From Matter to Materials and Life” (MML), 12.02.2019, Dresden, Deutschland
  • Invited lecture (Conferences)
    15th International Workshop on Slow Positron Beam Techniques & Applications (SLOPOS-15), 02.09.2019, Prague, Czech Republic
  • Lecture (Conference)
    The European Materials Research Society (E-MRS) Fall Meeting, 16.09.2019, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-30615
Publ.-Id: 30615


Measurement systems for liquid metals

Wondrak, T.
This talk represents an introduction into measurement techniques for liquid metals including invasive probes, ultrasonic and inductive methods as well as x-ray radiography.
Keywords: liquid metal, measurement techniques
  • Invited lecture (Conferences)
    PAMIR summer school 2019, 02.-5.7.2019, Reims, France

Permalink: https://www.hzdr.de/publications/Publ-30614
Publ.-Id: 30614


Inductive measurement techniques for liquid metals

Wondrak, T.
This talk represents an introduction into inductive measurement techniques for liquid metals.
Keywords: liquid metals, inductive measurement techniques, flow measurement
  • Invited lecture (Conferences)
    MHD Modelling School 2019, 14.-18.10.2019, Riga, Latvia

Permalink: https://www.hzdr.de/publications/Publ-30613
Publ.-Id: 30613


Misunterstandings – how dies the mining industry present itself in Europe and how is it perceived by society?

Reuter, M. A.
Europe’s mining sector aligns itself with the sustainability agenda through concepts such as the circular economy, the coming energy and resource transition, a zero-waste economy, etc. Ironically, these concepts also cause misunderstandings within society, most notably that no more mining or smeltering will be needed. This can be seen in the current debate on the ban of lead, i.e. lead is a necessary carrier element for many CRMs and lead-metallurgy is fundamental for a true circular economy. Is education enough to overcome these misunderstandings or is something else needed?
Keywords: Mireu, research, Social License to Operate, SLO, sustainability, circular economy, lead
  • Invited lecture (Conferences)
    3rd SLO workshop: ensuring SLO is adaptive and resilient, 05.-06.06.2019, Brüssel, Belgien

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Permalink: https://www.hzdr.de/publications/Publ-30612
Publ.-Id: 30612


Contribution to the structure of the periodic classification of metals - Metals enable Future® Metalle vernetzen Zukunft®

Reuter, M.ORC
The importance of metals in society //
The fundamental role of metals (incl. lead) in a circular society//
Metallurgical infrastructure criticality in a circular society
Keywords: metals, circular society, circular economy
  • Invited lecture (Conferences)
    EMC 2019 – 10th European Metallurgical Conference, 23.-26.06.2019, Düsseldorf, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-30610
Publ.-Id: 30610


Inductive and resistive methods for gas detection

Wondrak, T.; Gundrum, T.; Willers, B.ORC
This talk gives an overview about resistive and inductive methods for bubble detection in liquid metals.
Keywords: liquid metal, bubble detection
  • Lecture (Conference)
    ESFR-SMART European Workshop on Instrumentation for the Safety of Liquid Metal Facilities, 10.-12.04.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30609
Publ.-Id: 30609


Contactless inductive flow tomography

Wondrak, T.; Ratajczak, M.; Stefani, F.
This talk gives an overview of the contactless inductive flow tomography and recent developments at HZDR.
Keywords: contactless inductive flow tomography, inductive flow measurement, liquid metal
  • Lecture (Conference)
    ESFR-SMART European Workshop on Instrumentation for the Safety of Liquid Metal Facilities, 10.-12.04.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30608
Publ.-Id: 30608


Pulsed-Magnet Developments at the Dresden High Magnetic Field Laboratory

Zherlitsyn, S.ORC
für diesen Vortrag hat keine inhaltliche Kurzfassung vorgelegen
  • Invited lecture (Conferences)
    MT 26 - International Conference on Magnet Technology, 22.-27.09.2019, Vancouver, Canada

Permalink: https://www.hzdr.de/publications/Publ-30606
Publ.-Id: 30606


Pressure-Tuning the Quantum Spin Hamiltonian of the Triangular Lattice Antiferromagnet Cs2CuCl4: High-Field ESR Studies

Zvyagin, S.ORC
für diesen Vortrag hat keine inhaltliche Kurzfassung vorgelegen
  • Invited lecture (Conferences)
    Conference EPR-75 (Electron Paramagnetic Resonance (EPR)), 23.-27.09.2019, Kazan, Russia

Permalink: https://www.hzdr.de/publications/Publ-30604
Publ.-Id: 30604


Spin-Lattice Coupling in a Yafet-Kittel Ferrimagnetic Spinel

Miyata, A.
für diesen Vortrag hat keine inhaltliche Kurzfassung vorgelegen
  • Invited lecture (Conferences)
    14th Asia-Pacific Physics Conference (APPC), 17.-22.11.2019, Kuching, Malaysia

Permalink: https://www.hzdr.de/publications/Publ-30603
Publ.-Id: 30603


Materialien die sich Kälte merken

Gottschall, T.ORC
für diesen Vortrag hat keine inhaltliche Kurzfassung vorgelegen
  • Invited lecture (Conferences)
    Verständliche Wissenschaft 2019, 14.02.2019, Geesthacht, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30602
Publ.-Id: 30602


Magnetocaloric materials for solid-state refrigeration

Gottschall, T.ORC
für diesen Vortrag hat keine inhaltliche Kurzfassung vorgelegen
  • Invited lecture (Conferences)
    Institutsseminar Fraunhofer IWS, 02.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30601
Publ.-Id: 30601


A short history about (nearly) everything concerning bio-research in Dresden

Schäfer, S.
  • Lecture (others)
    Vorlesung an der Universidad de Granada, 17.12.2019, Granada, Spain

Permalink: https://www.hzdr.de/publications/Publ-30600
Publ.-Id: 30600


Development of turbulent cellular structures in Rayleigh-Benard convection in a finite liquid metal layer

Tasaka, Y.; Akashi, M.; Yanagisawa, T.; Vogt, T.ORC; Eckert, S.ORC
Large-scale, coherent flow structures of Rayleigh-Bénard convection in a finite liquid metal layer were examined experimentally by means of ultrasonic Doppler velocimetry. The fluid layer with aspect ratio of five and L = 40 mm in height was filled with eutectic alloy of GaInSn (Prandtl number, Pr = 0.03), and multiple ultrasonic transducers for the velocimetry were mounted in the side wall of the vessel to capture three-dimensional structures of the convection.
Spatio-tempral velocity maps obtained at different Rayleigh numbers in the range, 7900 < Ra < 180000, elucidated emergences of wavy-roll-like coherent structures, where the roll axis is determined quasi-randomly. The roll structure takes transition with reducing the number of rolls from four to three as Ra increases via intermediate regime between the two conditions, four or three rolls. With further increase of Ra a cellular structure with characteristics of fully developed thermal turbulence occupies the entire fluid layer. We will discuss details on derivation of the power law and relation with turbulent superstructures that have recently been discussed.
Keywords: Rayleigh-Benard convection, liquid metal, velocity measurements, coherent structures
  • Lecture (Conference)
    17th European Turbulence Conference, 03.-06.09.2019, Torino, Italy

Permalink: https://www.hzdr.de/publications/Publ-30597
Publ.-Id: 30597


Liquid Metal Model Experiments for Continuous Casting of Steel

Schurmann, D.ORC; Eckert, S.ORC
Experimental investigations of the fluid flow in the continuous casting mold are performed at the Mini-LIMMCAST facility of HZDR, which is a liquid metal mockup operated with GaInSn at room temperature. Velocity measurements in the non-transparent liquid metal are performed by means of the ultrasound Doppler velocimetry (UDV), which enables the reconstruction of the complex flow pattern in the mold. The focus of our study is on the influence of different electromagnetic actuators like electromagnetic brakes (EMBr) or electromagnetic stirring (EMS) on the mold flow in slab and bloom geometries.
Keywords: experimental investigation; liquid metal model; continuous casting; electromagnetic brake; electromagnetic stirring;
  • Lecture (others)
    CFD and Thermomechanics Days, 04.-06.02.2020, Online, Internet

Permalink: https://www.hzdr.de/publications/Publ-30596
Publ.-Id: 30596


Interprofessionelle Kooperation in klinischen Studien. Zunehmender Bedarf, Komplexität und Anregungen am Beispiel einer prospektiv-onkologischen Multicenter-Studie.

Zippel, C.; Giesel, F.; Kopka, K.ORC
Um neue Erkenntnisse in für Patienten nützliche Behandlungsansätze überführen zu können, werden in der medizinischen (onkologischen) Translationsforschung zunehmend prospektive klinische Studien initiiert. Damit diese Studien möglichst effizient und effektiv durchgeführt werden können, bedarf es der engen Kooperation und Kommunikation von Experten aus verschiedenen Berufsgruppen. In diesem Aufsatz beleuchten wir am Beispiel der prospektiven onkologisch-klinischen DKTK-PSMA-Studie der Phasen-I/-II „68Ga-PSMA-11 in Hochrisiko-Prostatakrebs“, welche wesentlichen Professionen bei der Planung, Vorbereitung und Durchführung von (nuklearmedizinisch) klinischen Studien involviert sein können und welche essenziellen Aufgaben diese zur Verwirklichung der Studie leisten. Darauf aufbauend führen wir allgemeine organisatorische Maßnahmen an, durch welche die interprofessionelle Zusammenarbeit bei künftig weiteren (nicht nur onkologischen)
Studien gefördert werden kann.

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Permalink: https://www.hzdr.de/publications/Publ-30594
Publ.-Id: 30594


Challenges of the Circular Economy

Reuter, M. A.
A Circular Economy (CE) paradigm aims to maximize sustainability and resource efficiency by extending product life cycles and using wastes as resources. So, what is the brave step that will deliver the CE for modern services, complex products, and society in general? Questions we should, among others, ask and attempt to answer are (i) What are the challenges to achieve this move forward? (ii) What does the metallurgical infrastructure have to be that maximally recovers materials from increasingly complex products and services, while returning high quality materials back into the CE? (iii) What smart energy and water grid will maximize resource efficiency and minimize exergy destruction of an increasingly complex society and system? In order to answer these questions, the role of metallurgical processing systems, smart materials production, digital technology platforms, product design etc. will be discussed in the context of Sustainable Circular Cities. It will furthermore be shown how digitalized real-time simulation and control of material and metal flow and metallurgical processing systems i.e. the “Smart Materials Grid - SMG” will form the heart of the CE system. The SMG will integrate into the water, energy, transport, heavy industry, and other grid systems and will help drive the resource efficiency of the future “Sustainable Circular Cities.” This will help to enable “Smart Sustainable Living” by also helping to quantify and realize the United Nation’s Sustainability Development Goals.
Keywords: Circular Economy, sustainability, resource efficiency, CE,
  • Invited lecture (Conferences)
    REWAS 2019 Plenary Session, 10.-14.03.2019, San Antonio, Texas, USA

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Permalink: https://www.hzdr.de/publications/Publ-30593
Publ.-Id: 30593


New Strategies for Imaging of Brain Cancer with Radiopharmaceuticals

Brust, P.
Background:
Brain cancer is a challenge for the health care system because of major problems for treatment. Radical surgery is not possible. Radiation treatment is restricted by missing borderlines, and drug treatment is limited by the blood-brain barrier. Therefore, glioblastoma multiforme, the most aggressive type of primary brain tumors, has a median overall survival of only ~12 months. Although new molecular pathways are being constantly discovered, translation of basic science into clinical practice is rather slow. Major obstacles in the resistance to therapy are heterogeneity of brain tumors, multiple genetic alterations, and their diffuse, infiltrative behavior. Hence monitoring of pathways related to tumor etiology and growth is highly important.
Methodology:
Positron emission tomography (PET) offers the potential to identify key signaling and metabolic pathways in tumors and to discover drugs for targeted therapy. An important prerequisite for PET is the development of radiolabeled molecules (radiotracer) to investigate impaired brain functions in living human subjects. Fluorine-18 is currently the most favorable radionuclide that is routinely used for radiolabeling because of its half-life of 109.8 min. The presentation will focus on the development of fluorine-18 labelled radiotracers bridging from basic science to biomedical application and focusing on four targets of major importance for brain cancer.
Results and Discussion:
Cannabinoids are known to induce apoptosis of glioma cells and the extent of cannabinoid CB2 receptor expression is related to tumor malignancy. The challenge in radiotracer development is the high expression of CB1 receptors. Therefore our strategies will be presented to achieve highly selective PET radiotracers for CB2 receptors.
The immunosuppressive effects of adenosine and the adenosine-triggered activation of catabolic energy production account for pro-cancer roles of extracellular adenosine. Accordingly, plasma-membrane-bound adenosine receptors were identified as new targets in the immunotherapy of brain tumors. Currently, we have PET radiotracers for A2A and A2B receptors under development, which are regarded as potential tools for therapy monitoring.
Sigma receptors, previously regarded as opioid receptors, are comprised of the σ1 and σ2 subtypes and represent orphan receptors of different families. While the σ1 receptor is a molecular chaperone, which interacts with various ion channels and G-protein coupled receptors, the σ2 receptor (TMEM97) is an intracellular protein located at the endoplasmatic reticulum that binds numerous drugs. There is evidence that both subtypes are important for glioblastoma growth thus facilitating the ongoing development of selective PET radiotracers for both subtypes in our department.
Furthermore, as other cancers glioblastoma is characterized by metabolic reprogramming to preferentially undergo aerobic glycolysis. The elevated production of lactate is accompanied by the increased expression of monocarboxylate transporters (MCTs). Accordingly a therapeutic approach targeting MCTs is a promising strategy in brain cancer treatment. A PET radiotracer for peripheral MCT1/MCT4 imaging has already been developed by us and will be discussed concerning its suitability for glioblastoma imaging.
Conclusion:
Numerous attempts are ongoing for molecular characterization of brain cancer with PET radiopharmaceuticals. It is expected that they will support in the future patient stratification and hence individualized therapy.
  • Lecture (Conference)
    International Symposium on Trends in Radiopharmaceuticals - ISTR 2019, 28.10.-01.11.2019, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-30590
Publ.-Id: 30590


Metallurgy is fundamental to the Circular Economy

Reuter, M. A.
The importance of metals in society,
The fundamental role of metals (incl. lead) in a circular society,
Metallurgical infrastructure criticality in a circular society
Keywords: metals, circular society,
Related publications
Lead Metallurgy is Fundamental to the Circular Economy … (Id 30586) is part of this publication
  • Invited lecture (Conferences)
    International Lead Association conference, 19.-21.06.2019, Madrid, Spanien

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Permalink: https://www.hzdr.de/publications/Publ-30589
Publ.-Id: 30589


Disturbing-free determination of yeast concentration in DI water and in glucose using impedance biochips

Kiani, M.; Du, N.; Vogel, M.; Raff, J.; Hübner, U.; Skorupa, I.; Bürger, D.; Schulz, S. E.; Schmidt, O. G.; Blaschke, D.; Schmidt, H.
Deionized water and glucose with yeast (Saccharomyces cerevisiae) of optical density OD600 ranging from 4 to 16 has been put in the ring electrode region of impedance biochips and impedance has been measured in dependence on the added volume (20, 21, 22, 23, 24, 25 L). Modeled impedance of the biochip reveals a linear relationship between the impedance model parameters and yeast concentration. Presented biochips allow for continuous impedance measurements without interrupting the cultivation of the yeast. A multiparameter fit of the impedance model parameters allows to determine the concentration of yeast cy in the range from cy = 3.3x107 to cy = 17x107 cells/mL. This work shows that independent on the liquid, DI water or glucose, the change of the impedance model parameters with increasing added volume of the liquid is clearly distinguishable from the change of impedance model parameters with increasing concentration of added yeast in the ring electrode region of the impedance biochips.
Keywords: Biochips, impedance spectroscopy, yeast Saccharomyces cerevisiae, electrical equivalent circuit, biomaterial, biosensing

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Permalink: https://www.hzdr.de/publications/Publ-30588
Publ.-Id: 30588


Lead Metallurgy is Fundamental to the Circular Economy Policy Brief SOCRATES EU MSCA-ETN

Reuter, M.ORC; Malfliet, A.; Blanpain, B.
Metals are eminently recyclable, and by recycling and refining complex materials, the EU's interconnected metals sector is responding to the increasing scarcity of certain metals. In this way, we are delivering and recovering the technology and base metals for the EU's Circular Economy (CE). Moreover, metals are at the heart of the energy infrastructures that now run Circular Cities, and they will play an even greater part in the future. One of these metals is lead. With respect to this familiar metal, industry is fully aware that in order to keep on using it, the associated risks need to be well managed at all times. Importantly, lead is a key enabler in the CE, as it is capable of dissolving and carrying a multitude of technology elements. The recovery and recycling of several critical technology elements is based on refining them from lead through well-developed metallurgical processes in which the lead acts as a carrier metal. Limiting lead metallurgy would have a detrimental impact, not only on the lead industry itself, but on all the industries linked to it. It is therefore critical that we maintain and further develop the lead infrastructure and know-how in Europe. To put it simply, lead metallurgy is fundamental if the EU wants to retain its leading position in the global CE. Executive Summary the 5 lessons learned: • Lesson 1: Lead is frequently seen as a problematic metal that can be detrimental to human health; what is much less well known is its fundamental role in extrac-tive metallurgy and how this is closely associated with the Circular Economy. • Lesson 2: Molten lead has unique properties that means it can act as an efficient liquid carrier for critical raw materials such as In, Bi, Cd and Te. • Lesson 3: Restricting lead metallurgy in the EU would not only have a detrimental impact on the lead industry, but also on all the industries linked to it that work with elements like Ag, Cu, Sb, Sn, Te, and Zn. • Lesson 4: The focus must be on correctly and comprehensively minimising the risks of lead-containing materials for society and carefully managing them, rather than attempting to ban the use of lead. • Lesson 5: An environmentally friendly and energy-efficient lead infrastructure together with the associated research and know-how in Europe is absolutely vital if the continent is to maintain its global leadership in the Circular Economy.
Keywords: recyclable, recycling, EU's Circular Economy, CE, Circular Cities, lead, research
Related publications
Metallurgy is fundamental to the Circular Economy (Id 30589) has this publication as part
  • Other report
    ---: ETN Socrates, 2019
  • Lecture (Conference)
    Fifth SOCRATES network-wide event, 19.-21.02.2019, Leicester, England

Permalink: https://www.hzdr.de/publications/Publ-30586
Publ.-Id: 30586


Process metallurgy and systems in circular city design – the challenges

Reuter, M. A.
Realising the circular economy is faced with some significant challenges. Process metallurgy and its infrastructure play key roles at the heart of making the circular economy work. The enabling role of process metallurgy within the circular economy and circular cities will be discussed, touching also on product and system design.
Keywords: circular economy, process metallurgy, product and system design
  • Invited lecture (Conferences)
    Connecting Innovation in the Raw Materials Sector / EIT Raw Materials summit 2019, 20.-22.05.2019, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30585
Publ.-Id: 30585


Stability criterion for the magnetic separation of rare-earth ions

Lei, Z.ORC; Fritzsche, B.; Eckert, K.ORC
The stability criterion for the magnetic separation of rare-earth ions is studied, taking dysprosium Dy(iii) ions as an example. Emphasis is placed on quantifying the factors that limit the desired high enrichment. During magnetic separation, a layer enriched in Dy(iii) ions is generated via the surface evaporation of an aqueous solution which is levitated by the Kelvin force. Later, mass transport triggers instability in the enriched layer. The onset time and position of the instability is studied using an interferometer. The onset time signals that an advective process which significantly accelerates the stratification of enrichment is taking place, although the initial phase is quasi-diffusion-like. The onset position of the flow agrees well with that predicted with a generalized Rayleigh number (Ra∗=0) criterion which includes the Kelvin force term acting antiparallel to gravity. Further three-dimensional analysis of the potential energy, combining magnetic and gravitational terms, shows an energy barrier that has to be overcome to initiate instability. The position of the energy barrier coincides well with the onset position of the instability.
Keywords: Evaporation, Flow instability, Instability control, Optical interferometry, Transport phenomena

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Permalink: https://www.hzdr.de/publications/Publ-30582
Publ.-Id: 30582


Spectral tomography for 3D mineral and chemical analysis

Da Assuncao Godinho, J. R.; Renno, A.ORC; de Schryver, T.; Masschaele, B.
A new analytical tool for mineral analysis will be introduced: Laboratory-based Spectral 3D X-ray Computed Tomography (Sp-CT). Results from a spectral imaging detector, prototype installed inside a TESCAN CoreTOM micro-CT system, will be presented and discussed in the context of mineralogical and chemical analysis of geological materials. The technique will be demonstrated to allow:
a) 3D mineral classification from the transmitted energy spectrum characteristic of a mineral phase.
b) Quick bulk chemical quantification of heavy elements with K-edge > 20 keV at high concentrations that are difficult to analyse by other methods.
c) Reducing common CT artefacts such as scattering and beam hardening, as well as improved contrast by selectively choose the most convenient energy range.
The advantages of Sp-CT will open new possibilities in geometallurgy and minerals processing research to move from the predominant 2D based image characterization towards more representative 3D characterization. These are fundamental steps to enable automated and routine 3D characterization that ultimately has the potential to provide faster and lower cost analysis to, for example, the mining industry, as well as more comprehensive rock characterization technique for Earth sciences research.
Keywords: XRCT, spectral XRCT
  • Poster
    PRORA - 10. Fachtagung Prozessnahe Röntgenanalytik, 28.-29.11.2019, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30581
Publ.-Id: 30581


Applications in the Resource Industry - Between Handheld Instruments and 4D Methods

Renno, A.ORC; Da Assuncao Godinho, J. R.; Gutzmer, J.ORC; Kelly, N.; Reuter, M.ORC; Seidel, P.; Sittner, J.; Winardhi, C. W.
An exemplary overview of the use of X-ray-based analytical methods in the resource industry, underpinned by examples, gives a very heterogeneous picture. The use of these methods is considered in the exploration, mining, mechanical processing and metallurgical/chemical processing of primary and secondary mineral and metallic raw materials.
Although X-ray diffraction, fluorescence, absorption and luminescence as well as various tomographic methods cover a very broad spectrum of methods, in many cases their use is apparently rather arbitrary, regardless of the respective matrix, technology and location.
For example for offline characterisation of raw materials and intermediates, established and reliable methods as well as pure estimation methods are used. In inline analytics, ad-hoc analytical instruments are used in addition to metrologically well-proven measuring systems that are well integrated into the respective technological processes. The enforcement of state standards with regard to environmental protection and resource use leads to a significant increase in the use of analytical technology and increased requirements for the certification of procedures.
A conspicuous feature is the constantly growing use of mobile "handheld devices", which are often used at decisive points to control the flow of materials. Very often, it can be observed that these devices, which in principle are very powerful, work under their respective capabilities or lead to significantly wrong results due to insufficiently thought-out and implemented measuring methods.
Almost all inline analytical methods used for sorting or process monitoring have the characteristic that they only lead to binary decisions. A comprehensive characterization of the material flow, which would lead both to flexible adaptation of the technologies used subsequently and to a significantly more differentiated splitting of the material flow, is a consequence of the ever more complex properties of the primary and secondary raw materials. This is the result of the change to economic forms with significantly stronger elements of a circular economy.
On the basis of current research at the HIF, it is presented how such a multi-effective measuring system could be designed. Furthermore, the advantages of the use of 3D methods in the characterization of primary and secondary raw materials as well as in the description of technological processes will be demonstrated. Both spectral XRCT (X-Ray Computed Tomography) and dynamic time-resolved XRCT methods are used.
Keywords: Resource Industry, Process Analysis, X-Ray Methods
  • Invited lecture (Conferences)
    PRORA - 10. Fachtagung Prozessnahe Röntgenanalytik, 28.-29.11.2019, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30580
Publ.-Id: 30580


Halogen analysis of sulphide minerals at the ultratrace level – first applications of the Dresden Super-SIMS

Renno, A.ORC; Rugel, G.ORC; Wiedenbeck, M.; Ziegenrücker, R.ORC
The integration of an ion source having very high spatial resolution with a tandem accelerator is a long-standing concept for improving analytical selectivity and sensitivity by orders of magnitude [1]. Translating this design concept into reality has its challenges [e.g. 2,3], meaning this approach has seldom been employed for mineralogical and geochemical research [e.g. 4].
Supporting a strong focus on natural, metallic and mineral resources, the Helmholtz Institute Freiberg for Resource Technology installed a so-called Super-SIMS at the Ion Beam Center at HZDR in Dresden-Rossendorf; this highly novel tool is devoted to the characterization of minerals and ores. The secondary ion beam from a CAMECA IMS 7f-auto is injected into the 6MV Dresden Accelerator Mass Spectrometry [5] facility, which effectively eliminates all molecular species from the ion beam.
We will present the current status of this initiative and will report our first results from halogen determinations (F, Cl, Br, I) in both sphalerite and galena. These data demonstrate a systematic and significant change in the counting rates of all halogens in mineralogically distinct areas of both minerals. Furthermore, we will describe our concepts for the quantification of these data at ultratrace levels.


[1] Matteson (2008) Mass Spec Rev 27, 470-484. [2] Ender et al. (1997) NIMB 123, 575-578. [3] Fahey et al. (2016) Anal Chem 88, 7145-7153. [4] Sie et al. (2000) NIMB 172, 228-234. [5] Rugel et al. (2016) NIMB 370, 94-100.
Keywords: SIMS, Super-SIMS, Halogen, Sphalerite, Galena
  • Lecture (Conference)
    GEOMÜNSTER 2019, 22.-25.09.2019, Münster, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30579
Publ.-Id: 30579


Halogen analysis at the ultratrace level – first applications of the Dresden Super-SIMS

Renno, A.ORC; Akhmadaliev, S.; Belokonov, G.; Böttger, R.; Borany, J.; Kaever, P.; Meyer, M.; Noga, P.; Rugel, G.ORC; Tiessen, C. J.; Wagner, N.; Wiedenbeck, M.; Wu, H.ORC; Ziegenrücker, R.ORC
The integration of an ion source having very high spatial resolution with a tandem accelerator is a long-standing concept for improving analytical selectivity and sensitivity by orders of magnitude [1]. Translating this design concept into reality has its challenges [e.g. 2,3], meaning this approach has seldom be used in the framework of geochemical research [e.g. 4].
Supporting a strong focus on natural, metallic and mineral resources, the Helmholtz Institute Freiberg for Resource Technology installed a so-called Super-SIMS at the Ion Beam Center at HZDR; this highly novel tool is devoted to the characterization of minerals and ores. The secondary ion beam from a CAMECA IMS 7f-auto is injected into the 6MV Dresden Accelerator Mass Spectrometry [5] facility, which quantitatively eliminates effectively all molecular species from the ion beam.
We will present the current status of this initiative and will report on the performance parameters of the Dresden Super-SIMS as well as first results from halogen determinations in sphalerite and galena. Furthermore, we will describe our concepts for the quantification of these data at the ultratrace level.
[1] Matteson (2008) Mass Spec Rev 27, 470-484. [2] Ender et al. (1997) NIMB 123 575-578. [3] Fahey et al. (2016) Anal Chem 88, 7145-7153. [4] Sie et al. (2000) NIMB 172, 228-234. [5] Rugel et al. (2016) NIMB 370 94-100.
Keywords: SIMS. Super-SIMS, Sphalerite, Halogen
  • Lecture (Conference)
    GOLDSCHMIDT 2019, 18.-23.08.2019, Barcelona, Spanien

Permalink: https://www.hzdr.de/publications/Publ-30578
Publ.-Id: 30578


Single-Shot Multi-keV X-Ray Absorption Spectroscopy Using an Ultrashort Laser-Wakefield Accelerator Source

Kettle, B.; Gerstmayr, E.; Streeter, M. J. V.; Albert, F.; Baggott, R. A.; Bourgeois, N.; Cole, J. M.; Dann, S.; Falk, K.ORC; Gallardo González, I.; Hussein, A. E.; Lemos, N.; Lopes, N. C.; Lundh, O.; Ma, Y.; Rose, S. J.; Spindloe, C.; Symes, D. R.; Smid, M.ORC; Thomas, A. G. R.; Watt, R.; Mangles, S. P. D.
Single-shot absorption measurements have been performed using the multi-keV x rays generated by alaser-wakefield accelerator. A 200 TW laser was used to drive a laser-wakefield accelerator in a modewhich produced broadband electron beams with a maximum energy above 1 GeVand a broad divergence of ≈15mrad FWHM. Betatron oscillations of these electrons generated1.2 0.2×106photons=eV in the5 keV region, with a signal-to-noise ratio of approximately 300∶1. This was sufficient to allow high-resolution x-ray absorption near-edge structure measurements at theKedge of a titanium sample in a singleshot. We demonstrate that this source is capable of single-shot, simultaneous measurements of both theelectron and ion distributions in matter heated to eV temperatures by comparison with density functionaltheory simulations. The unique combination of a high-flux, large bandwidth, few femtosecond durationx-ray pulse synchronized to a high-power laser will enable key advances in the study of ultrafast energeticprocesses such as electron-ion equilibration.

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Permalink: https://www.hzdr.de/publications/Publ-30577
Publ.-Id: 30577


Laser-wakefield accelerators for high-resolution X-ray imaging of complex microstructures

Hussein, A. E.; Senabulya, N.; Ma, Y.; Streeter, M. J. V.; Kettle, B.; Dann, S. J. D.; Albert, F.; Bourgeois, N.; Cipiccia, S.; Finlay, O.; Gerstmayr, E.; Gallardo Gonzales, I.; Higginbotham, A.; Jaroszynski, D. A.; Falk, K.ORC; Krushelnick, K.; Lemos, N.; Lopes, N. C.; Lumsdon, C.; Lundh, O.; Mangles, S. P. D.; Najmudin, Z.; Rajeev, P. P.; Schlepütz, C. M.; Shahzad, M.; Smid, M.ORC; Spesyvtsev, R.; Symes, D. R.; Vieux, G.; Willingale, L.; Wood, J. C.; Shahani, A. J.; Thomas, A. G. R.
Laser-wakefield accelerators (LWFAs) are high acceleration-gradient plasma-based particle accelerators capable of producing ultra-relativistic electron beams. Within the strong focusing fields of the wakefield, accelerated electrons undergo betatron oscillations, emitting a bright pulse of X-rays with a micrometer-scale source size that may be used for imaging applications. Non-destructive X-ray phase contrast imaging and tomography of heterogeneous materials can provide insight into their processing, structure, and performance. To demonstrate the imaging capability of X-rays from an LWFA we have examined an irregular eutectic in the aluminum-silicon (Al-Si) system. The lamellar spacing of the Al-Si eutectic microstructure is on the order of a few micrometers, thus requiring high spatial resolution. We present comparisons between the sharpness and spatial resolution in phase contrast images of this eutectic alloy obtained via X-ray phase contrast imaging at the Swiss Light Source (SLS) synchrotron and X-ray projection microscopy via an LWFA source. An upper bound on the resolving power of 2.7 ± 0.3 μm of the LWFA source in this experiment was measured. These results indicate that betatron X-rays from laser wakefield acceleration can provide an alternative to conventional synchrotron sources for high resolution imaging of eutectics and, more broadly, complex microstructures.

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Permalink: https://www.hzdr.de/publications/Publ-30576
Publ.-Id: 30576


Renewable Methanol Synthesis

Roode-Gutzmer, Q. I.ORC; Kaiser, D.; Bertau, M.
Renewable methanol production is an emerging technology that bridges the gap in the shift from fossil fuel to renewable energy. Two thirds of the global emission of CO₂ stems from humanity’s increasing energy need from fossil fuels. Renewable energy, mainly from solar and wind energy, suffers from supply intermittency, which current grid infrastructures cannot accommodate. Excess renewable energy can be harnessed to power the electrolysis of water to produce hydrogen, which can be used in the catalytic hydrogenation of waste CO₂ to produce renewable methanol. This review considers methanol production in the current context, regionally for Europe, which is dominated by Germany, and globally by China. Appropriate carbon-based feedstock for renewable methanol production is considered, as well as state-of-the-art renewable hydrogen production technologies. The economics of renewable methanol production necessitates the consideration of regionally relevant methanol derivatives. The thermodynamics, kinetics, catalytic reaction mechanism, operating conditions and reactor design are reviewed in the context of renewable methanol production to reveal the most up to date understanding.
Keywords: Catalysis, Energy storage, Hydrogenation of CO₂, Renewable methanol, Waste CO₂

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Permalink: https://www.hzdr.de/publications/Publ-30575
Publ.-Id: 30575


The role of gas impurities on the optical properties of sputtered Ti(Al)N coatings

Bohovičová, J.; Meško, M.; Méndez, Á.; Julin, J. A.ORC; Munnik, F.ORC; Hübner, R.; Grenzer, J.; Čaplovič, Ľ.; Krause, M.ORC
In this study, we investigated the role of impurities, such as H, C, and O on the optical properties of the Ti(Al)N coatings. For comparison, coatings were prepared by direct-current magnetron sputtering (DC-MS) and high-power impulse magnetron sputtering (HiPIMS) at the same average power. The elemental composition of the thin films was measured by elastic recoil detection analysis. Regardless of the deposition technique used, no significant difference in H and C concentrations were found. The analysis showed, that HiPIMS coatings contain less O impurities than the corresponding DC-MS films, despite the lower deposition rate. The reduced residual O content in HiPIMS coatings can be explained by the cleaning effect of the bombarding ions. Moreover, densification effects presumably suppress post-deposition oxidation. Given the reduced O content, HiPIMS films showed higher optical reflectance for the entire measured spectral range.
  • Lecture (Conference)
    The 15th International Symposium on Sputtering and Plasma Processes, ISSP 2019, 11.-14.06.2019, Kanazawa, Japan
  • Poster
    The 15th International Symposium on Sputtering and Plasma Processes, ISSP 2019, 11.-14.06.2019, Kanazawa, Japan
  • Contribution to proceedings
    The 15th International Symposium on Sputtering and Plasma Processes, ISSP 2019, 11.-14.06.2019, Kanazawa, Japan

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Permalink: https://www.hzdr.de/publications/Publ-30572
Publ.-Id: 30572


Ultrafast Mid-Infrared and Terahertz Phenomena in Graphene

Winnerl, S.
Graphene, the first atomically thin 2D material that was intensely investigated since its discovery in 2014, is a gapless semiconductor or semimetal with linear dispersion. Consequently, graphene absorbs light at all energies, in particular also at low photon energies in the THz frequency range. Here we show that pump-probe experiments at low photon energies can provide deep insights into the carrier dynamics. In particular, electron-phonon scattering can be disentangled from Coulomb scattering processes [1, 2]. Coulomb scattering in graphene is responsible for a number of unusual effects like strong Auger scattering under Landau quantization [3].
With respect to applications we present a graphene based detector with ultrafast response time of 40 ps. It operates in the very broad frequency range from visible to THz radiation [4].
[1] S. Winnerl, M. Orlita, P. Plochocka, P. Kossacki, M. Potemski, T. Winzer, E. Malic, A. Knorr, M. Sprinkle, C. Berger, W. A. de Heer, H. Schneider und M. Helm, Phys. Rev. Lett. 107, 237401 (2011).
[2] J. C. König-Otto, M. Mittendorff, T. Winzer, F. Kadi, E. Malic, A. Knorr, C. Berger, W. A. de Heer, A. Pashkin, H. Schneider, M. Helm und S. Winnerl, Phys. Rev. Lett. 117, 087401 (2016).
[3] M. Mittendorff, F. Wendler, E. Malic, A. Knorr, M. Orlita, M. Potemski, C. Berger, W. A. de Heer, H. Schneider, M. Helm und S. Winnerl, Nature Phys. 11, 75 (2015).
[4] M. Mittendorff, J. Kamann, J. Eroms, D. Weiss, C. Drexler, S. D. Ganichev, J. Kerbusch, A. Erbe, R. J. Suess, T. E. Murphy, S. Chatterjee, K. Kolata, J. Ohser, J. C. König-Otto, H. Schneider, M. Helm, S. Winnerl, Optics Express 23, 28728 (2015).
Keywords: graphene, terahertz, ultrafast
  • Invited lecture (Conferences)
    Sino-German Bilateral Symposium on Low Dimensional Semiconductors and Opto-electronics Integration, 14.-17.11.2019, Changsha, China

Permalink: https://www.hzdr.de/publications/Publ-30568
Publ.-Id: 30568


Ge-based photoconductive emitters producing gapless broadband THz spectra

Singh, A.ORC; Pashkin, O.ORC; Winnerl, S.; Helm, M.; Schneider, H.ORC
We present photoconductive emitters based on Ge featuring gapless broadband spectra up to 13 THz. Thus they can fill the gap in the 5 – 10 THz range and can be excited with fiber lasers.
Keywords: terahertz, broadband, photoconductive emitters
  • Lecture (Conference)
    CLEO/Europe-EQEC 2019, 23.-27.06.2019, Munich, Germany

Permalink: https://www.hzdr.de/publications/Publ-30567
Publ.-Id: 30567


Nonlinear THz resoponse of graphene plasmonic structures

Winnerl, S.; Jadidi, M. M.; Chin, M.; Seidl, A.; Schneider, H.; Helm, M.; Drew, H. D.; Murphey, T. E.; Mittendorff, M.
Ribbons and discs based on doped graphene feature strong tunable plasmonic resonances. We show that excitation with THz radiation results in strong changes of transmission, even at moderate pump fluences. The response is due to a broadening and redshift for the plasmonic absorption line as charge carriers are heated. The response time is determined by the cooling of carriers, which is of the order of 10 ps.
Keywords: graphene, plasmonics, nonlinear terahertz spectroscopy
  • Invited lecture (Conferences)
    META 2019, the 10th International Conference on Metamaterials, Photonic Crystals and Plasmonics, 23.-26.07.2019, Lisbon, Portugal

Permalink: https://www.hzdr.de/publications/Publ-30566
Publ.-Id: 30566


Nonlinear THz spectroscopy in low-dimensional semiconductors using a free-electron laser

Winnerl, S.; Schmidt, J.; König-Otto, J.; Mittendorff, M.; Schneider, H.ORC; Helm, M.
Sources for intense THz pulses allow one to investigate interesting nonlinear effects in various solid-state systems in a time-resolved manner. Here we discuss perturbative and non-perturbative nonlinear effects in graphene-based systems and GaAs/AlGaAs quantum wells, respectively, which are excited by intense, tunable, narrowband THz pulses from a free-electron laser (FEL).
For the graphene-based samples we have pursued two strategies to resonantly enhance the linear and nonlinear response. One way is to apply a magnetic field perpendicular to the graphene layer.
This splits the linear band structure into a set of non-equidistant Landau levels. Four-wave mixing experiments on the lowest Landau levels reveal a strong nonlinearity and a rapid dephasing of the microscopic polarization on sub-ps timescales [1]. The second path for resonant enhancement is the fabrication of ribbons and discs of doped graphene that feature a strong plasmonic response [2]. The nonlinearity corresponding to the plasmonic response is based on a red-shift and broadening of the absorption line caused by carrier heating.
While the previously discussed phenomena are perturbative nonlinear effects, FEL pulses are also well suited to generate non-perturbative effects such as the intraexcitonic Autler-Townes effect and double dressing of polaritons in microcavities [3, 4]. Here we present novel results on the dressing of subbands in a single GaAs/AlGaAs quantum well by THz photons. To this end, the transition between the second and third subband was resonantly pumped with the FEL. Broadband probing by THz time-domain spectroscopy using GaP crystals for optical rectification enabled us to observe the THz-dressing of the electronic states. Namely Autler-Townes splitting occurs at the transition between the first and second subband while the transition from the second to the third subband is split into a Mollow triplet.
We are grateful to our collaborators M. M. Jadidi, T. E. Murphy, A. Belyanin, and E. Malic.
REFERENCES
1. König-Otto, J. C., Wang, Y., Belyanin, A., Berger, C. de Heer, W. A., Orlita, M., Pashkin, A., Schneider, H., Helm, M., Winnerl, S. "Four-wave mixing in Landau-quantized graphene," Nano Lett., Vol. 17, 2184-2188, 2017.
2. Jadidi, M. M., Daniels, K. M., Myers-Ward, R. L., Gaskill, D. K., Konig-Otto, J. C., Winnerl, S., Sushkov, A. B., Drew, H. D., Murphy, T. E., Mittendorff, M. "Optical control of plasmonic hot carriers in graphene," ACS Photonics, Vol. 6, 302307, 2019.
3. Wagner, M., Schneider, H., Stehr, D., Winnerl, S., Andrews, A. M., Schartner, S., Strasser, G., Helm, M. "Observation of the intraexciton Autler-Townes effect in GaAs=AlGaAs semiconductor quantum wells," Phys. Rev. Lett., Vol. 105, 167401, 2010.
4. Pietka, B., Bobrovska, N., Stephan, D., Teich, M., Krol, M., Winnerl, S., Pashkin, A., Mirek, R., Lekenta, K., Morier-Genoud, F., Schneider, H., Deveaud, B., Helm, M., Matuszewski, M., Szczytko, J. "Doubly dressed bosons: exciton polaritons in a strong terahertz field," Phys. Rev. Lett., Vol. 119, 077403, 2017.
Keywords: Free-electron laser, terahertz, nonlinear spectroscopy, low-dimensional semiconductors
  • Invited lecture (Conferences)
    Photonics & Electromagnetics Research Symposium (PIERS), 17.-20.06.2019, Rome, Italy

Permalink: https://www.hzdr.de/publications/Publ-30565
Publ.-Id: 30565


THz nonlinear optics in graphene ribbons

Jadidi, M. M.; Daniels, K. M.; Myers-Ward, R.; Gaskill, D. K.; König-Otto, J.; Winnerl, S.; Sushkov, A.; Drew, H. D.; Murphy, T. E.; Mittendorff, M.
Graphene plasmonics is an emerging field due the unique combination of spectral tunability, strong plasmonic resonance and low losses. Here we study the nonlinear optical properties of graphene bilayer ribbons, featuring a plasmonic resonance at 3.9 THz, in time resolved experiments. A redshift of the plasmonic resonance is observed upon excitation with picosecond THz pulses. The unconventional nonlinear effect is explained by the optical response of hot carriers. Already at fairly low fluences in the µJ/cm2 range strong changes in transmission in the 10 % range can be induced. This strong response, together with the fast recovery determined by the electron cooling time (∼10 ps), makes the system promising for optical switching applications.
Keywords: graphene, plasmonics, nonlinear optics
  • Lecture (Conference)
    DPG-Frühjahrstagung, 31.03.-05.04.2019, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30564
Publ.-Id: 30564


High Power Lasers for Advanced Accelerator Development at the ELBE Center Dresden

Schramm, U.ORC
Presentation of High Power Lasers Activities for
Advanced Accelerator Development
at the ELBE Center Dresden
Keywords: high power lasers
  • Invited lecture (Conferences)
    Helmholtz Laser and Photonics Meeting 2019, 03.-04.12.2019, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30563
Publ.-Id: 30563


Emergence of nanoscale patterns under ion induced non-equilibrium conditions

Facsko, S.ORC
Various self-organized nanoscale patterns emerge on surfaces which are irradiated by low- or medium-energy ion beams [1]. Depending on the irradiation conditions, hexagonally ordered dot or pit patterns, checkerboard patterns, as well as periodic ripple patterns are formed spontaneously due to the non-equilibrium conditions induced by continuous ion irradiation. In the collision cascade induced by an ion impact several defects, including interstitials, vacancies, ad-atoms and more complex defects are created. Below the recrystallization temperature, the surface is thus quickly amorphized by continuous ion irradiation and massive mass-transport takes place due to momentum-transfer from the ions to the near-surface atoms. Furthermore, ion sputtering is eroding the material non-homogeneously inducing a roughening instability.
On amorphous or amorphized surfaces, the formation of periodic patterns at high ion fluences results from an interplay of different roughening mechanisms, e.g. curvature dependent sputtering, ballistic mass redistribution, or altered surface stoichiometry on binary materials, and smoothing mechanisms, e.g. surface diffusion or viscous flow. Therefore, the patterns obey the symmetry given by the ion beam direction, i.e. hexagonal near order at normal incidence and two-fold symmetry with the ripple direction oriented perpendicular or parallel to the ion beam direction at off-normal incidence.
If the temperature during ion irradiation is above the recrystallization temperature of the material, ion induced defects are dynamically annealed and amorphization is prevented. The diffusion of ion-induced vacancies and ad-atoms on the crystalline surface is now additionally affected by the Ehrlich-Schwoebel barrier, like in molecular beam epitaxy. Vacancies and ad-atoms are trapped on terraces and can nucleate to form pits or terraces, respectively. Patterns formed in this regime exhibit the symmetry of the crystal structure of the irradiated surface and often have inverse pyramidal shapes with well-defined facets [2,3]. Therefore, this mechanism is called “reverse epitaxy”.
1.1. Ion induced patterns on Ge and GaAs
In Fig. 1 examples of ion irradiation induced pattern are shown for amorphized Ge surface (a, b) and for Ge (001) (c) and GaAs (001) (d) irradiated above their respective recrystallization temperatures of 250° and 200°C.
1.2. Modelling pattern formation by continuum equations
Pattern formation on ion irradiated surfaces can be modelled my atomistic simulation methods, such as molecular dynamics (MD) and Monte-Carlo (kMC), or by continuum equations. Due to the large area and high fluences, MD and MC cannot cover the large dynamic range, however, they can provide valuable insight into defect generation and ion induced mass transport. Continuum equations on the other hand are coarse grain approximations, which can cover much larger spatial and temporal regimes. Information from MD or MC can furthermore be used as input for predictive modelling of new materials and irradiation conditions.
Keywords: ion beams, ion-surface interaction, nanopattering
  • Invited lecture (Conferences)
    23rd International Workshop on Inelastic Ion-Surface Collisions, 17.-22.11.2019, Matsue, Japan

Permalink: https://www.hzdr.de/publications/Publ-30562
Publ.-Id: 30562


Ion beam modification and ion beam analysis in current materials research

Facsko, S.ORC; Heller, R.; Munnik, F.ORC; Klingner, N.ORC; Hlawacek, G.ORC
Introduction to the IOne Beam Cneter and Current Research.
Keywords: Ion beam analysis, ion beam modification
  • Lecture (Conference)
    NATO Advanced Training Course: “Spintronics Radar Detectors”, 14.-18.10.2019, Athens, Greece

Permalink: https://www.hzdr.de/publications/Publ-30561
Publ.-Id: 30561


Comparison of Si and Ge surface patterns produced by ion irradiation in the reverse epitaxy regime

Facsko, S.ORC; Xin, O.; de Schultz, R.; Erb, D.
In addition to sputtering, ion irradiation is often also leading to restructuring of the surface and a plethora of surface patterns can appear. At irradiation temperatures high enough to dynamically anneal defects induced by the collision cascades the surface remains crystalline. Still, a high density of ion-induced surface vacancies and adatoms remains and their diffusion is affected by the Ehrlich-Schwoebel (ES) barrier, i.e. an additional diffusion barrier to cross terrace steps. These defects are therefore trapped on terraces, nucleate and form pits or mounds [1]. In this way three dimensional, faceted nanostructures are formed, reflecting the underlying crystal lattice. Due to the similarity to growth of three-dimensional structures in molecular beam epitaxy this mechanism is called reverse epitaxy.
We will present patterns on Si and Ge surface induced by low energy, normal incidence, high fluence ion irradiation at temperatures above the recrystallization temperature. Patterns with very different symmetry can result, depending on the surface orientation: pyramidal structures with four-fold symmetry on the (001) surface, with three-fold and six-fold symmetry on the (111) surface and elongated structures with two-fold symmetry on the (011) surface [2].
Although Si and Ge have the same diamond crystal lattice, the resulting patterns and facets are different: on Ge(001) predominantly (105) facets are formed, whereas (115) facets are found on Si(001). Similarly, on Si(111) the pattern exhibits a six-fold symmetry with (123) facets, whereas on Ge(111) the patterns are formed by (356) facets and exhibit a three-fold symmetry. The formation mechanism and possible effects leading to these differences on Ge and Si surfaces will be presented and discussed.
Keywords: ion beams, nanopatterning, ion-surface interaction
  • Lecture (Conference)
    10th International Workshop on Nanoscale Pattern Formation at Surfaces (NanoPatterning 2019), 07.-10.07.2019, Surrey, England

Permalink: https://www.hzdr.de/publications/Publ-30560
Publ.-Id: 30560


Interaction of low-energy ions with surfaces and 2D materials

Facsko, S.ORC
The ion beam centre (IBC) of the Helmholtz-Zentrum Dresden-Rossendorf is a user facility primarily dedicated to research and application of ion beam techniques in materials research. The IBC comprises various ion beam facilities (accelerators, ion beam implanters, plasma-based ion beam equipment, focused / highly-charged ion facilities) which provide a wide energy range between 10 eV and 60 MeV. Besides these facilities, structural analysis (electron microscopy and spectroscopy, X-ray scattering techniques) and sample or device processing (under clean-room conditions) are part of the IBC to deliver a “complete” user service.
Special focus of the IBC is material research with low energy ions. Irradiations of surfaces with low energy ions can induce the formation of patterns with periodicities in the range of tens to hundreds of nanometers. At off-normal angle of incidence between 50° and 70° to the surface normal ripple patterns oriented perpendicular to the ion beam direction are observed. At normal incidence or for incidence angles smaller than 50° smoothing dominates on elemental materials, like Si and Ge. However, in contrast to irradiations at room temperature pattern formation is observed at normal ion incidence irradiations performed at temperatures above the recrystallization temperature of the material. Depending on the surface orientation checkerboard patterns with two-fold, three-fold, or six-fold symmetry reflecting the crystal structure of the irradiated surface are formed (Fig. 1).
Moreover, single impacts of low energy ions are used to create nanostructures and in thin membranes and for doping of 2D materials, like graphene and MoS2. In this case of highly charged ions the release of the potential leads to a local phase transformation of the material and subsequently to the formation of dots, pits or holes. Currently, a new facility for low energy ion nanoengineering is commissioned comprising a 100 keV accelerator for ion irradiations and MEIS, thin film deposition system, and different analytic tools for nanoscale analysis and characterization.
Keywords: ion beams, ion surface interaction, 2D materials
  • Lecture (others)
    Physics Seminar, 26.05.2019, Uppsala, Schweden

Permalink: https://www.hzdr.de/publications/Publ-30558
Publ.-Id: 30558


Advancing laser plasma accelerators by means of femto-scale diagnostics

Schramm, U.ORC
Invited talk on the role of femtoscale probing on laser plasma particle acceleration
Keywords: laser plasma accelerator
  • Invited lecture (Conferences)
    Conference on High Intensity and Attosecond Laser Science CHILI, 09.-11.12.2019, Tel Aviv, Israel

Permalink: https://www.hzdr.de/publications/Publ-30557
Publ.-Id: 30557


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