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This content will become publicly available on July 1, 2017

Title: Feasible voltage-tap based quench detection in a Ag/Bi-2212 coil enabled by fast 3D normal zone propagation

For this study, small insert solenoids have been built using a commercial Ag/Bi-2212 multifilamentary round wire, insulated with a new thin TiO2– polymer coating insulation (thickness in ~20 μm versus ~100 μm for a commonly used mullite braided sleeve insulation), and characterized in background magnetic field up to 14 T at 4.2 K to explore the high-field performance and quench detection of Bi-2212 magnets. The coil has no visible leakage and no electrical shorts after reaction, and it carries 280 A/mm-2 in a background field 14 T and generates an additional 1.7 T. A notable result is that, despite normal zones propagate slowly along the conductor, the hot spot temperature upon detection increases only from 40 K to 60 K when the resistive quench detection voltage threshold increases from 0.1 V to 1 V for all operating current density investigated, showing that quench detection using voltage taps is feasible for this coil. This is in a strong contrast to a coil we previously built to the same specifications but from wires insulated with the mullite braided sleeve insulation, for which the hot spot temperature upon detection increases from ~80 K to ~140 K while increasing from the detection voltage thresholdmore » from 0.1 V to 1 V, and thus for which quench detection using voltage taps presents significant risks, consistent with the common belief that the effectiveness of quench detection using voltage taps for superconducting magnets built using high temperature superconductors is seriously compromised by their slow normal zone propagation. This striking difference is ascribed to the fast transverse quench propagation enabled by thin insulation and improved thermal coupling between conductor turns. Finally, this work demonstrates that quench detection for high-temperature superconducting magnets highly depends on the design and construction of the coils such as insulation materials used and this dependence should be factored into the overall magnet design.« less
Authors:
 [1] ;  [2] ;  [2]
  1. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Publication Date:
OSTI Identifier:
1256710
Report Number(s):
FERMILAB-PUB--16-221-TD
Journal ID: ISSN 0953-2048; 1468548
Grant/Contract Number:
AC02-07CH11359; AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
Superconductor Science and Technology
Additional Journal Information:
Journal Volume: 29; Journal Issue: 8; Journal ID: ISSN 0953-2048
Publisher:
IOP Publishing
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 36 MATERIALS SCIENCE