Excitation Test of Solenoid MgB2 Coil Under External Magnetic Field Immersed in Liquid Hydrogen

We have been developing a liquid hydrogen (LH
₂
) cooled superconducting energy apparatus, such as superconducting generator, SMES, and so on. An MgB
₂
superconductor whose critical temperature is 39 K is now developing for a practical use. It can be cooled by LH
₂
with a sufficient temperature margin. An MgB
₂
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 MgB
₂
wire, we have carried out measurement tests of critical superconducting properties of MgB
₂
under LH
₂
cooling and investigation of heat transfer characteristics of LH
₂
. There are few reports on the experimental results of a superconducting coil using a long MgB
₂
wire under the LH
₂
immersion cooling. In this study, we have carried out an excitation test of a small MgB
₂
coil immersed in LH
₂
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 MgB
₂
wire (Hitachi Ltd., Ibaraki, Japan). The temperature of LH
₂
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.