Development of a solenoidal HTS coil cooled by liquid or gas helium

A small HTS coil was developed that is cooled by liquid or gas helium. The coil temperature can be adjusted from 4.2 to 77 K by pulling the coil in or above liquid helium (LHe). The coil has a short solenoid structure. It is made of six Bi-2223 tapes with cross-section dimensions of 3.1 mm * 0.168 mm. The single tape length is about 200 meters. Experiments were carried out to measure the critical currents of the coil at different temperatures from 4.2 to 77 K. To investigate the applicability of the HTS coil to superconducting magnetic energy storage (SMES), the coil was charged at various rates by a current source IGBT AC/DC converter with temperatures ranging from 20 to 55 K.