Quench stability against beam-loss in superconducting magnets at the 50 GeV proton beam line for the J-PARC neutrino experiment

The heat load on superconducting magnets induced by beam loss is a major subject to be solved for stable operation of the 50 GeV-0.75 MW J-PARC neutrino beam line. Heat load for a 10 W/point beam loss in an actual coil was calculated using the MARS code which simulates the actual magnet. Calculated heat load was up to 20 kJ/m(3)/pulse. Instantaneous heating of 0-40 kJ/m(3)/pulse was induced in Rutherford type cable in an experiment, and the thermal characteristic measured using SHe. The cable specimen for an experimental verification used the same structure as the superconducting cable for the magnet in the test. It was found that a heat pulse of 20 kJ/m(3) caused an instantaneous temperature rise of 0.25 K in the experiment and will not induce a quench according to the quench simulation calculation.