RAMP-RATE LIMITATION TEST OF CABLE-IN-CONDUIT CONDUCTORS WITH SUPERCRITICAL HELIUM

It has been found on the United States Demonstration Poloidal Coil (US-DPC) and in 27 strand subsized cables of pool boiling cable-in-conduit conductor (CICC), that there is critical current degradation due to fast ramping of the magnetic field. The characteristics of this ramp-rate limitation phenomenon are investigated by using a 27 strand Nb3Sn cable in supercritical helium at 6 atm. A 3 m long cable-in-conduit conductor is prepared noninductively and tested in a background field up to 9.5 tesla with maximum ramp rate of 1.6 tesla/second. The ramp-rate limitation results are compared with results of the ramp rate test of the US-DPC and previous experiments. The experimental data are analyzed to identify and understand possible sources of ramp-rate limitation.