A Proposal of New Fabricating Technique of Large MgB2 Bulk by a Capsule Method

We proposed a new fabricating technique of a large MgB2 superconducting bulk (20-30 mm in diameter) by a capsule method and measured the trapped field distribution for the MgB2 bulks. The capsule consists of a couple of commercial stainless steel flanges, a stainless steel plate and a copper gasket. The MgB2 bulks showed a superconducting transition at 38.3-38.6 K with a transition width of 0.6-1.1 K. The trapped magnetic field of the center of the bulk surface reached 1.65 T at 14 K for the bulk 30 mm in diameter. These results indicate that the capsule method is useful to produce the tesla-order large MgB2 bulk magnet.