Cooling Stability Test of MgB sub(2) Wire Immersed in Liquid Hydrogen under External Magnetic Field

Liquid hydrogen (LH sub(2)), which has large latent heat, low viscosity coefficient, is expected to be a candidate for a cryogen for superconducting wires, not only MgB sub(2) but also other HTC superconductors. LH sub(2) cooled superconducting wires are expected to have excellent electro-magnetic characteristics, which is necessary to be clear for cooling stability design of LH sub(2) cooled superconducting device, however, due to handling difficulties of LH sub(2), there are only few papers on the properties of LH sub(2) cooled superconductors, especially under external magnetic field. We designed and made an experimental setup which can energize superconducting wires immersed in LH sub(2) with the current of up to 500A under the condition of external magnetic field up to 7 T and pressure up to 1.5 MPa. In order to confirm experimental method and safety operation of the setup, over current tests were carried out using MgB sub(2) superconducting wires under various external magnetic field conditions. Critical current of the test wire at the temperature 21, 24, 27, 29 K under external magnetic fields up to 1.2 T was successfully measured. The resistance of the wire also was measured, while the transport current exceeded the critical current of the wire.