| 摘要 |
PURPOSE:To reduce an output necessary for an oblique magnetic field coil as low as possible and to obtain a cryostat having sufficient thermal shielding effect by using a stainless steel for a thermal shielding plate, and mounting a pipe for feeding liquid nitrogen around the plate. CONSTITUTION:When an oblique magnetic field coil 7 is operated, an eddy current is induced in a thermal shielding plate 3a of stainless steel. In case of the stainless steel, its electric resistance is approx. 1000 times as large as copper, and the magnetic field output is reduced due to the eddy current as well. Accordingly, the output of the coil 7 can be reduced that much in the correction of the magnetic field output. The stainless steel has approx. 1/1000 of thermal conductivity as compared with the copper. Thus, sufficient thermal shielding effect cannot be obtained by cooling by thermal conduction from a liquid nitrogen tank 2, but a pipe 9 is mounted to feed liquid nitrogen supplied from the tank 2, thus cooling the plate 3a, thereby enhancing the thermal shielding effect. |
