OBSERVATIONS ON FLUX JUMPING IN TUBULAR Nb , Sn SAMPLES IN TRANSVERSE FIELDS

The flux jumping behavior of tubular samples of vapor-deposited Nb,Sn has been observed at 4.2 and 1.9 K. Measurements of field profiles along the axis of the sample tubes provided information on the extent of the flux jumps and the nature of the field structure remaining after the jumps. Measurements of the field inside the tube as a function of the applied field provided information on the frequency and field dependence of the flux jumping. At low fields numerous partial flux jumps occurred, while above a critical field level of 510 kG samples were stable. The tubes were less stable at the lower temperature, although some improvement in stability was obtained by electroplating one of the samples with copper. The observations were compared with predictions based on the adiabatic stability criteria. Agreement was obtained between the observed temperature and field dependencies of the instabilities and the predictions of the theory. (Submitted to Cryogenics) *Supported by the Department of Energy, Contract No. EY-76-C-03-0515.