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

Abstract

For this study, small insert solenoids have been built using a commercial Ag/Bi-2212 multifilamentary round wire, insulated with a new thin TiO 2– 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 detectionmore » voltage threshold 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:
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)
OSTI Identifier:
1256710
Report Number(s):
FERMILAB-PUB-16-221-TD
Journal ID: ISSN 0953-2048; 1468548; TRN: US1601748
Grant/Contract Number:
AC02-07CH11359; AC02-05CH11231; Early Career Award
Resource Type:
Journal Article: 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
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 36 MATERIALS SCIENCE

Citation Formats

Shen, Tengming, Ye, Liyang, and Li, Pei. Feasible voltage-tap based quench detection in a Ag/Bi-2212 coil enabled by fast 3D normal zone propagation. United States: N. p., 2016. Web. doi:10.1088/0953-2048/29/8/08LT01.
Shen, Tengming, Ye, Liyang, & Li, Pei. Feasible voltage-tap based quench detection in a Ag/Bi-2212 coil enabled by fast 3D normal zone propagation. United States. doi:10.1088/0953-2048/29/8/08LT01.
Shen, Tengming, Ye, Liyang, and Li, Pei. 2016. "Feasible voltage-tap based quench detection in a Ag/Bi-2212 coil enabled by fast 3D normal zone propagation". United States. doi:10.1088/0953-2048/29/8/08LT01. https://www.osti.gov/servlets/purl/1256710.
@article{osti_1256710,
title = {Feasible voltage-tap based quench detection in a Ag/Bi-2212 coil enabled by fast 3D normal zone propagation},
author = {Shen, Tengming and Ye, Liyang and Li, Pei},
abstractNote = {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 threshold 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.},
doi = {10.1088/0953-2048/29/8/08LT01},
journal = {Superconductor Science and Technology},
number = 8,
volume = 29,
place = {United States},
year = 2016,
month = 7
}

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Cited by: 2works
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  • This paper discusses advantages and disadvantages of different locations of co-wound voltage sensors for quench detection in tokamak magnets with a cable-in-conduit conductor. The voltage sensor locations are analyzed and estimates of the anticipated noise vs. dB/dt are derived for transverse, parallel, and self fields. The LLNL Noise Rejection Experiment, also described here, is designed to verity theoretical expectations on a copper cable exposed to these fields that will simulate the tokamak field environment.
  • The key to understanding the fast quench phenomenon in multistrand cables is the normal zone origination and propagation in superconducting wires with fast changing currents. Results of experiments simulating the situation in strands during fast quench development are presented. The maximum quench current, normal zone velocity, increase of current and time before quench are measured in NbTi-CuNi composite wire at different transport current ramp rates and at different initial currents. Normal zone velocity propagation depends on I(t) and {dot I}(t) only. The presence of an initial current leads to the acceleration of normal zone propagation at decreasing current. The initialmore » current also leads to a reduction of the current increase and the time when a quench starts. The authors use the results received to explain the appearance of fast quench phenomenon in superconducting cables with insulated or highly resistive matrix strands.« less
  • Quench propagation was studied in a small bifilar coil wound from YBCO tape. Measurements were made at 77 K in self-field and at 4.2 K with an applied field. The velocity of quench propagation at 4.2 K was observed to be about an order of magnitude faster than at 77 K both in the longitudinal and transverse directions. During the course of this experiment the conductor damage limit characterized by ∫I2dt was also estimated. Details of the experiment and results are presented in this paper