THE VAMAS INTERCOMPARISON ON THE UPPER CRITICAL-FIELD MEASUREMENT IN NB-TI WIRE

The intercomparison on the upper critical field measurement in the Nb- Ti wire (NIST-SRM 1457) has been performed through the VAMAS TWA 6 act ivity. The homogeneity in the H-C2 of the wire is fairly good, while t he coefficient of scatter in the H-C2 intercomparison is about 0.60%. The scatter in high field measurement may cause that in critical curre nt measurement at high magnetic fields. Effects of several factors on the H-C2 of the Nb-Ti wire have been also studied. The coiled specimen shows slightly lower H-C2 than the straight sample. The H-C2 of the w ire shows an appreciable anisotropy with respect to the direction of a pplied field.