PRECOOLER FOR SUPERCONDUCTING MAGNET

PURPOSE:To reduce temperature rise in a tank of cryostat and to enable complete exhaust of refrigerant of a precooler for superconducting magnet by a method wherein a heater and a temperature measuring element are provided at the tank bottom part of cryostat, and the heater is controlled monitoring existence of the refrigerant by the temperature measuring element. CONSTITUTION:A superconducting magnet 2 is accomodated in the cryostat 1, and a pipe 3 is arranged as to open to the tank bottom part and a pipe 4 as to open to the upper part of the tank. The electric heater 6 is fixed to the tank bottom part, and is connected to a feed control circuit through a lead wire 7, and the temperature measuring part 9 of a thermoelectric couple 8 is fixed to the heater 6. A cold junction 10 of the thermoelectric couple 8 is equipped in a small heat insulating tank 11 as to be submerged in the refrigerant 5 for precooling, and a voltmeter 12 for temperature measurement is connected as to measure the temperature difference between the temperature measuring part 9 and the cold junction 10. Accordingly although the refrigerant 5 for precooling is poured in the tank when precooling is to be performed, and the refrigerant 5 is exhausted after the superconducting magnet is cooled, but when the refrigerant 5 is remained in the tank, because waste of refrigerant is generated, so that the remained refrigerant can be exhausted by making a current to be connected and disconnected from the heater monitoring deflection of the indicator of a voltmeter.