Numerically Thermal Stability Analysis on a Geometrically Symmetrical Strand Fabricated by 2G Wires in Liquid Helium Temperature

Due to its excellent j
_c
(B) performance at low temperatures, the second generation (2G) high-temperature superconducting (HTS) REBCO wire is promising for high-field applications. The thermal stability of a strand consisting of 2G wires operating at low temperatures is an important issue with increasing current density at high magnetic field. The paper focuses on the thermal stability of geometrically symmetrical strands under background direct current (dc) magnetic field of 6 T in liquid helium temperature by numerical method. The strand with copper sheath consists of 80 stacked 2G wires. The thermal stability of the strand is accurately analyzed based on the analytical dependence of the critical current density on temperature and magnetic field as well as its orientation to wide surface of 2G wire. By using the helium heat transfer coefficient, the minimum quench energy and the quench propagation velocity of the strand in liquid helium temperature are calculated and compared with those in the adiabatic conditions, the results are useful for application of the strand in high magnetic field at low temperature.