FLUX JUMP STABILITY IN NB3SN TAPE

GE manufactured Nb3Sn tape was examined to determine the influence of critical temperature, both conductor and coil current density (J(c)), and tape width on flux jump stability, The onset of flux jump instabil ity was measured in 3 mm wide, copper stabilized tapes reacted to a ra nge of critical currents (I-c) above and below the normal I-c in produ ction tape, These tapes were stacked in approximations of coil cross s ections with and without insulating interlayer glass cloth, Production tape, 3 mm wide, was found to be stable above 9 Kelvin (K) with norma l quantities of interlayer glass when reacted to yield an I-c no great er than 482 amps at 5 Tesla (T) and 4.2 K, To evaluate low temperature operation in the range of 4-5 K, consistent with cryocooler advances, narrower width tapes were studied as decreasing tape width will decre ase the flux jump stability temperature, Flux jump stability was measu red in identically reacted tapes slit to 3.0, 2.5, 2.0 and 1.5 mm, The 1,5 mm tape was found to be stable above 6.5 K, Slitting edge damage in the narrow widths was found to be similar for all widths of tape. T he I-c of the narrower tapes were predictably reduced. Decreasing coil current density also decreased the flux jump stability temperature, N b3Sn tape, 3 mm wide, cowound with copper into a solenoid was tested t o evaluate lower temperature operation. The coil was stable during bot h ramping and operation near the short sample I-c of the tape at 4.2 K .