Michael J. Wolf

Karlsruhe Institute of Technology

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W.H. Fietz

Karlsruhe Institute of Technology

R. Heller

Karlsruhe Institute of Technology

Klaus‐Peter Weiss

Karlsruhe Institute of Technology

D. Beckmann

Karlsruhe Institute of Technology

N. Bagrets

Karlsruhe Institute of Technology

Alan Preuß

Karlsruhe Institute of Technology

Christian Lange

Winterthur Museum Garden and Library

M. Heiduk

Karlsruhe Institute of Technology

Laura Savoldi

Polytechnic University of Turin

R. Zanino

Polytechnic University of Turin

Cooperative Institutions

Fusion Academy

Plasma Technology (United States)

Fusion (United States)

Karlsruhe Institute of Technology

Massachusetts Institute of Technology

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

National Agency for New Technologies, Energy and Sustainable Economic Development

Boston Fusion (United States)

École Polytechnique Fédérale de Lausanne

FZI Research Center for Information Technology

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HTS CroCo - demonstration of long length fabrication

Alan Preuß Michael J. Wolf N. Bagrets W.H. Fietz M. Heiduk

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Nonlocal transport and heating in superconductors under dual-bias conditions

Physical Review B (2013)

S. Kolenda Michael J. Wolf Dmitry S. Golubev Andrei D. Zaikin D. Beckmann

We report on an experimental and theoretical study of nonlocal transport in superconductor hybrid structures, where two normal-metal leads are attached to a central superconducting wire. As a function of voltage bias applied to both normal-metal electrodes, we find surprisingly large nonlocal conductance signals, almost of the same magnitude as the local conductance. We demonstrate that these signals are the result of strong heating of the superconducting wire, and that under symmetric bias conditions, heating mimics the effect of Cooper pair splitting.

Biasing

Cooper pair

10.1103/physrevb.88.174509

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A critical assessment of thermal–hydraulic modeling of HTS twisted-stacked-tape cable conductors for fusion applications

Superconductor Science and Technology (2019)

Andrea Zappatore W.H. Fietz R. Heller Laura Savoldi Michael J. Wolf

Reliable analyses of thermal–hydraulic (TH) transients are becoming fundamental to supporting the design of magnets for fusion applications based on high temperature superconducting (HTS) cable-in-conduit-conductors (CICCs). However, currently available TH codes were developed and validated only for the analysis of magnets wound with low temperature superconductor (LTS) CICCs. In order to confirm the applicability of such tools to HTS CICCs, a two-step strategy is presented in this paper. First, a qualitative assessment of the characteristic time and spatial scales in HTS CICCs, based on the twisted-stacked-tape cable (TSTC) concept, has been performed. It shows that the different geometry and materials of TSTC strands lead to heat transfer time scales on the conductor cross-section, which are comparable to those of fast transients, ranging from milliseconds to few seconds, e.g. quench initiation and propagation as well as AC losses. Therefore, the assumptions of temperature uniformity on the cross-section, typical of the well-established 1D codes developed for LTS magnets, become questionable. A second, quantitative assessment, based on detailed electro-thermal models of the conductor and of the single TSTC strand cross-section, provides guidelines for the development of more reliable 1D models for the analysis of TH transients in HTS fusion magnets.

Electrical conduit

Thermal hydraulics

10.1088/1361-6668/ab20a9

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Citations (36)

Biblis electronuclear power plant (West Germany)

L. Dieterich Michael J. Wolf J. Vogel

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Analysis and evaluation of processes and equipment in tasks 2 and 4 of the low-cost solar array project

Howard H. Goldman Michael J. Wolf

Several experimental and projected Czochralski crystal growing process methods were studied and compared to available operations and cost-data of recent production Cz-pulling, in order to elucidate the role of the dominant cost contributing factors. From this analysis, it becomes apparent that substantial cost reductions can be realized from technical advancements which fall into four categories: an increase in furnace productivity; the reduction of crucible cost through use of the crucible for the equivalent of multiple state-of-the-art crystals; the combined effect of several smaller technical improvements; and a carry over effect of the expected availability of semiconductor grade polysilicon at greatly reduced prices. A format for techno-economic analysis of solar cell production processes was developed, called the University of Pennsylvania Process Characterization (UPPC) format. The accumulated Cz process data are presented.

Crucible (geodemography)

Cost reduction

Characterization

Economic Analysis

Production cost

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Review and evaluation of past solar cell development efforts. Semiannual report, 1 Jun-30 Nov 1967

P.A. Crossley G. T. Noel Michael J. Wolf

Historical review of scientific work on photovoltaic effects and on energy conversion devices using this effect

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Subscale HTS Fusion Conductor Fabrication and Testing in High Magnetic Background Field

IEEE Transactions on Applied Superconductivity (2022)

Daniel Nickel N. Bagrets W.H. Fietz Christian Lange Klaus‐Peter Weiss

In actual or future fusion machines like ITER, JT-60SA, W7-X or the present EU-DEMO design, low temperature superconductor (LTS) cables are used or planned to be used in the magnet system to create the strong magnetic field necessary for plasma confinement. High temperature superconductors (HTS) offer the potential to increase the magnetic field strength in fusion magnet systems even further, allowing to build more compact fusion machines or to realize higher flux swings in central solenoids. In this work, two HTS conductors were fabricated and characterized by high current testing at 77 K in self-field conditions and at 4.2 K with an external magnetic field up to 12 T. Both samples offer the same amount of superconducting HTS tapes but differ in the assembly process and termination type. These tests were intended to validate the current KIT design of a HTS CroCo triplet conductor and to qualify a low degradation cable manufacturing process.

Fusion power

10.1109/tasc.2022.3151581

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Picture Power 新時代の台湾に息づく融合の文化

ニューズウィーク (2008)

Michael J. Wolf

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Long-range spin transport in superconductors

arXiv (Cornell University) (2012)

F. Hübler Michael J. Wolf D. Beckmann H. v. Löhneysen

We report on nonlocal transport in multiterminal superconductor-ferromagnet structures, which were fabricated by means of e-beam lithography and shadow evaporation techniques. In the presence of a significant Zeeman splitting of the quasiparticle states, we find signatures of spin transport over distances of several {\mu}m, exceeding other length scales such as the coherence length, the normal-state spin-diffusion length, and the charge-imbalance length. The relaxation length of the spin signal shows a nearly linear increase with magnetic field, hinting at a freeze-out of relaxation by the Zeeman splitting. We propose that the relaxation length is given by the recombination length of the quasiparticles rather than a renormalized spin-diffusion length.

Spin diffusion

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A critical assessment of the issues in the thermal modeling of an HTS CroCo conductor for the EU DEMO TF coils

Andrea Zappatore W.H. Fietz R. Heller Laura Savoldi Michael J. Wolf

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