| 摘要 |
PURPOSE:To reduce the thermal load of liquid helium due to the radiative nuclear kerns by constituting an adsorption part from the material having a large radiation-beam transmittance, thus making a condensation part and the adsorption part from the material having different radiation-beam transmittance. CONSTITUTION:A pump case 12 is made of stainless steel having a low radiation-beam transmittance and covered with lead outside. Also a liquid nitrogen reservoir 34 as condensation part and radiation shield buffles 30 and 32 are made of the material having a low radiation-beam transmittance such as stainless steel and lead, and absorb the thermal load due to radiation beam. The liquid helium reservoirs 36 and 42 as adsorption part, radiation shielding buffle 38, and low-temperature adsorbing surface 40 consist of a thin-plate structure having a large radiation-beam transmittance such as aluminium, and the thermal load is reduced by allowing the radiation beam to transmit as much as possible.
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