| 摘要 |
PURPOSE:To reduce an amount of liquid helium consumed for cooling, by means of a construction wherein a conductor section between a thermal anchor section and an extremely low temperature section is cooled by means of liquid nitrogen while a current is flowing through the conductor. CONSTITUTION:The valves 7, 10 are closed when non-conducting current. At this time, since liquid nitrogen LN2 in the conductor 4b is stationary, nitrogen existing on the lower temperature side from the thermal anchor section is supercooled by liquid helium LHe through the conductor 4a so as to reduce the temperature as proceeding toward the low temperature section. If the temperature is set at about 30K on non-conducting current state, a state results in which supercooled liquid nitrogen and solid state nitrogen are coexistent in the conductor 4b. In this case, thermal conductivity of nitrogen is sufficiently smaller than that of the conductor 4. On conducting current, the valves 7, 10 are opened. When nitrogen on the lower temperature end of the liquid nitrogen cooling section 4b is freezed, the valve 7 may be closed or limited. When the temperature of the current lead rises due to heat resulted from the conducting current so that liquid nitrogen LN2 can flow, the valve 7 is adjusted so as to attain a required flow rate. |
