Flux-Jumping Behavior of Some Niobium-Tin Solenoids

Abstract

Oscillographic and X‐Y recorder observations have been made of the flux‐jumping pattern in several superconducting Nb₃Sn solenoids at magnetic fields ranging from 15 to above 100 kG at 4.2°K. It is noted that flux jumping is much more frequent in these solenoids than is observed in Nb–Zr solenoids. The flux‐jump pattern extends throughout the high‐field region. It can be modified, however, by gross rate changes in current increase, as well as by application and removal of external fields which change the induced magnetization. Frequent quenching of the Nb₃Sn superconducting solenoids does not seem to alter the flux‐jump behavior appreciably. The relationship of a superconductive transition to flux jumps occurring just prior to the transition is discussed. It is suggested that the more frequent but often lower‐amplitude flux jumps in these niobium‐tin solenoids contribute to the smaller coil degradation effect noticed as compared to niobium‐zirconium solenoids. To eliminate, or at least minimize this effect, further exploration of magnetic instabilities and influence of material parameters is required.