CRYOGENIC PERFORMANCE OF A SUPERCONDUCTING MAGNET SYSTEM FOR THE J‐PARC NEUTRINO BEAM LINE

A neutrino experiment facility using the J-PARC proton beam has been constructed at Tokai campus of KEK. In this project, a 150 m superconducting magnet system is installed in an arc section of the primary proton beam line. The magnet system consists of 28 superconducting magnets. The cold mass of a magnet is 6 tons. The refrigerator and the magnets are connected by a transfer tube with the total length of 90 m. Forced flow supercritical Helium with the mass flow rate of 300 g/sec, the inlet temperature of 4.5 K and inlet pressure of 400 kPa is supplied to the magnets through the transfer tube. A pair of superconducting busbars are also installed in the transfer tube. Total cold mass of the magnet system including the transfer tube and other instruments is about 204 tons. This paper describes the cryogenic performance of the superconducting magnet system.