| 摘要 |
PURPOSE:To flow no current across a coil protection resistance in a liquid helium vessel and depress the vaporization of liquid helium due to heat generation by switching a heater on in the permanent current switch using an automatic heater switch when the value of exciting current becomes equal to that of the source current. CONSTITUTION:When it is desired to decrease the current of a superconducting coil 1 from that in the permanent current mode, current leads 3 are installed and the power supply 2 is actuated to increase the source current. Then the value of exciting current is calculated from the measured value with a flux meter 12 and indicated on an exciting current meter 13. When the source current, which is indicated on a source current meter 14, becomes equal to that on the meter 13, an automatic heater switch 14 is actuated to switch the heater on. Then the superconducting wire 8 comes to function in the normal state of conductivity and the permanent current switch 7 is opened. Owing to no difference between the exciting current and the source current neither current flows in the coil protection resistance 4 nor increase appears in the vaporization of liquid helium resulting from heat generation. The same thing can be said of the case where it is desired to increase the current from that in the permanent current mode. |
