Trapped Fields of Hot-Pressed MgB2 for Applications in Liquid Hydrogen

The development of hydrogen energy and, in particular, high-performance submersible liquid hydrogen (LH) pumps requires superconducting bearings which can trap magnetic fields up to 1 T at 20 K. MgB
₂
is hence a promising candidate for this application. The superconducting properties and microstructure of differently prepared MgB
₂
were compared and the ability of different composite materials to trap magnetic fields was studied. Hollow cylinders of the same geometry were manufactured from hot pressed (under 30 MPa) blocks prepared from Mg:2B with Ti, TiC and Ti-O additives as well as from melt-textured YBCO ceramics. The high critical current densities and critical magnetic fields should ensure high trapped fields in all these materials. Indeed all materials demonstrated the required performance; however, flux jumps are a serious issue in MgB
₂
even in crack free cylinders and impeded higher trapped fields.