Effects of Cu stabilizer configuration on thermal stability of Nb/sub 3/Sn composite superconductors under cryocooling condition

Abstract

It is known that current sharing effects of the stabilizer are limited in cryocooling conditions being different from poolboiling. Therefore we have studied stability under it, focusing on minimum quench energy (MQE) of Nb 3 Sn superconductors under various conditions of the applied magnetic field, temperature, and the transport current, for various volume fractions and configurations of Cu stabilizer. From the experimental results, the larger the external Cu volume fraction, the higher the MQE was obtained. All MQE data were summarized by only one line in characteristics of normalized MQE and normalized ( c2 ). The obtained MQE behavior was to be characterized by only one empirical equation. It is thought that the obtained formula is useful for a standard of designing the Nb 3 Sn superconductor and its coil under cryocooled condition.

Quench and Normal Zone Propagation Characteristics of RHQT-Processed ${\rm Nb}_{3}{\rm Al}$ Wires Under Cryocooler-Cooling Conditions

“…The typical results of characteristics in the cryocooler cooling, i.e. decrease with increase of fields, were observed because the in the cryocooler cooling is determined by the temperature margin [5]- [8]. It is different from characteristics in the immersed cooling using the cryogen; i.e.…”

“…Voltage taps and temperature measuring sensors (Cernox) were set on the sample. Signals obtained from them were recorded by a personal computer and a digital oscilloscope [5]- [8]. The critical temperature was measured by the resistance method in accordance with the international standards of measurement method, IEC 61788-10, in changing the temperature using the cryocooler under applied magnetic fields.…”

“…However, while a lot of studies concerned with stability under the pool-boiling cooling condition have been achieved, such as Maddock's equal area theory [2], Stekly's classic cryostatic stability criterion [3], and CCM stability criterion [4], fewer have addressed stability under the cryocooler-cooling conditions. Previously, there were some reports on thermal stability of wires under pulsed and external-oriented disturbances caused by wire-movements and cracks in epoxy in the potted coil under cryocooler-cooling conditions [5]- [8]. In these cases, the minimum quench energy behavior was characterized by only one empirical equation [8].…”

“…Previously, there were some reports on thermal stability of wires under pulsed and external-oriented disturbances caused by wire-movements and cracks in epoxy in the potted coil under cryocooler-cooling conditions [5]- [8]. In these cases, the minimum quench energy behavior was characterized by only one empirical equation [8].…”