A.C. losses in niobium single crystals in the Meissner state

Abstract
Losses at 50 Hz as a function of magnetic field and surface profile have been investigated in single crystal samples of niobium at 42°K using an electronic wattmeter. The losses in samples with smooth surfaces were less than 5 × 10−4 W Hz−1 m−2 at 1 × 105 A m−1 (1250 Oe). A sample with a cold-worked surface showed higher losses both before and after the surface was polished. It is concluded that the surface finish is of major importance in determining the magnitude of losses below the lower critical field.