Development of a cryogenic DC transformer using for the measurement of large current

Abstract

Superconducting transformer is a typical facility used for inducing ultra-high current for large-scale scientific measurement systems, such as SULTAN-facility at the Centre de Recherches en Physique des Plasma (CRPP) in Switzerland, FRESCA-facility at CERN in Switzerland etc. A new program has been launched at the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) to build a new conductor test facility to investigate the transverse pressure dependence of critical current of various superconducting cables using a compact superconducting transformer and cryogenic electromagnetic press systems. The superconducting transformer can induce a secondary current up to 60 kA, at a background magnetic field up to 15 T at 4.2 K. To measure the induced secondary current at cryogenic temperature precisely, three types of NbTi superconducting coils are designed based on the zero-flux principle to characterize the variation of the measured current. In this paper, the design principle of the cryogenic DC transformer and its commissioning results in a preliminary prototype test device are presented. The measurement results show achievements on accuracy of ±0.6% or less and nonlinearity of better than ±0.25%, which demonstrates the feasibility of the cryogenic DC transformer and provides a reliable technology for the secondary current measurement of a 100 kA superconducting transformer used in the program of Super-X test facility at ASIPP.