Excitation Test Of Solenoid Mgb2 Coil Under External Magnetic Field Immersed In Liquid Hydrogen

We have been developing a liquid hydrogen (LH2) cooled superconducting energy apparatus, such as superconducting generator, SMES, and so on. An MgB2 superconductor whose critical temperature is 39 K is now developing for a practical use. It can he cooled by LH2 with a sufficient temperature margin. An MgB2 wire is expected to be used for superconducting equipment due to the low production cost and material cost. In order to design equipment using the MgB2 wire, we have carried out measurement tests of critical superconducting properties of MgB2 under LH2 cooling and investigation of heat transfer characteristics of LH2. There are few reports on the experimental results of a superconducting coil using a long MgB2 wire under the LH2 immersion cooling. In this study, we have carried out an excitation test of a small MgB2 coil immersed in LH2 under an external magnetic field. Tanaka et al proposed that the test coil is a 529 turn solenoid coil with an inner diameter of 120 mm, an outer diameter of 190 mm, and a height of 41 mm, which was produced by the Wind and React method using a 300-m multifilament MgB2 wire (Hitachi Ltd., Ibaraki, Japan). The temperature of LH2 was changed from 21 K to 30 K and the external magnetic field was also applied up to 4.5 T. In the experiment, the critical characteristic of the solenoid coil was measured and a coil load line was obtained.