TY - JOUR
T1 - Stability and quench behavior of YBa2CU3O 7-X coated conductor at 4.2 K, self-field
AU - Song, Honghai
AU - Schwartz, Justin
N1 - Funding Information:
Manuscript received February 11, 2009; revised May 4, 2009. First published July 6, 2009; current version published September 30, 2009. This paper was recommended by Associate Editor P. J. Masson. This work was supported in part by the Air Force Office of Scientific Research and in part by the U.S. Department of Energy.
PY - 2009/10
Y1 - 2009/10
N2 - YBa2CU3O7-X (YBCO) coated conductors (CCs) are now capable of carrying very high transport critical current density J c over a broad range of magnetic field and temperature space, and as a result, they are receiving significant interest for a wide range of applications. While many of these applications take advantage of the high-temperature performance of YBCO CCs, because the YBCO CC is typically produced on a high-strength substrate and carries very high Jc at very high magnetic field, there is now growing interest in using YBCO CCs at 4.2 K to generate very high magnetic fields. The transition from high-field conductor to high-field superconducting magnet, however, requires that some challenging issues be addressed. One of the most important challenges remaining is to better understand the stability and quench behavior at 4.2 K, so that an effective quench protection system can be developed. Here, we report on measurements of the stability and quench behavior of short YBCO CC at 4.2 K by inducing a quench via a heat pulse from a heater mounted on the conductor surface. Through gradually increasing heater pulse amplitude, the transition from stable to unstable (i.e., recovery to quench) is observed through voltage and temperature measurements. Using these data, the minimum quench energy (MQE) and normal zone propagation velocity (NZPV) are determined. It is found that, for the same fraction of critical current (I/Ic), YBCO CCs have similar MQE and NZPV as Ag-alloy-clad Bi2Sr2CaCu 2Ox wires and significantly higher MQE and lower NZPV than those of MgB2 round wires of similar Ic (4.2 K). Furthermore, the voltage and temperature versus time data are correlated to better understand the quench onset behavior at 4.2 K. It is determined that a normal temperature gradient exists from the CC surface to the YBCO layer within the conductor, as well as a directly measured longitudinal temperature gradient. After the heater pulse has ended but while the transport current continues, the temperature gradient along the length becomes dominant. Nevertheless, voltage and temperature measurements remain problematic for quench detection in large magnets because of the slow longitudinal propagation velocity. Thus, new approaches to quench detection and/or protection of high-field YBCO magnets are needed.
AB - YBa2CU3O7-X (YBCO) coated conductors (CCs) are now capable of carrying very high transport critical current density J c over a broad range of magnetic field and temperature space, and as a result, they are receiving significant interest for a wide range of applications. While many of these applications take advantage of the high-temperature performance of YBCO CCs, because the YBCO CC is typically produced on a high-strength substrate and carries very high Jc at very high magnetic field, there is now growing interest in using YBCO CCs at 4.2 K to generate very high magnetic fields. The transition from high-field conductor to high-field superconducting magnet, however, requires that some challenging issues be addressed. One of the most important challenges remaining is to better understand the stability and quench behavior at 4.2 K, so that an effective quench protection system can be developed. Here, we report on measurements of the stability and quench behavior of short YBCO CC at 4.2 K by inducing a quench via a heat pulse from a heater mounted on the conductor surface. Through gradually increasing heater pulse amplitude, the transition from stable to unstable (i.e., recovery to quench) is observed through voltage and temperature measurements. Using these data, the minimum quench energy (MQE) and normal zone propagation velocity (NZPV) are determined. It is found that, for the same fraction of critical current (I/Ic), YBCO CCs have similar MQE and NZPV as Ag-alloy-clad Bi2Sr2CaCu 2Ox wires and significantly higher MQE and lower NZPV than those of MgB2 round wires of similar Ic (4.2 K). Furthermore, the voltage and temperature versus time data are correlated to better understand the quench onset behavior at 4.2 K. It is determined that a normal temperature gradient exists from the CC surface to the YBCO layer within the conductor, as well as a directly measured longitudinal temperature gradient. After the heater pulse has ended but while the transport current continues, the temperature gradient along the length becomes dominant. Nevertheless, voltage and temperature measurements remain problematic for quench detection in large magnets because of the slow longitudinal propagation velocity. Thus, new approaches to quench detection and/or protection of high-field YBCO magnets are needed.
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U2 - 10.1109/TASC.2009.2023674
DO - 10.1109/TASC.2009.2023674
M3 - Article
AN - SCOPUS:70349898091
SN - 1051-8223
VL - 19
SP - 3735
EP - 3743
JO - IEEE Transactions on Applied Superconductivity
JF - IEEE Transactions on Applied Superconductivity
IS - 5
M1 - 5156264
ER -