Thermal design and verification tests of the Nb-Ti demo poloidal coils (DPC-U1, U2)

For the development of a 30-MJ, 7-T/s pulsed coil, a 30-kA cable-in-conduit conductor with low pulsed loss was designed and fabricated. The Japan Atomic Energy Research Institute performed verification tests to measure the temperature increase when a high-energy disturbance of 300 mJ/cc-strand is put into the superconducting strands and also to measure the stability margin of the conductor, which is increased by a factor of 1.65 when the He flow rate is increased from 0 to 1.0 g/s at the nominal current under 7 T. A possible mechanism to explain this improvement is discussed. >