PURPOSE: To obtain a cavity having a large inner diameter and to obtain a heat insulating container, whose entire weight can be made light without increasing the outer diameter of the entire configuration, by using an object for heat insulation as a reference, and decreasing the number of heat radiation shield plates, which are located at inner position than the object for heat insulation in comparison with the number of heat radiation shield plates, which are located at the outer position of the object for heat insulation.
CONSTITUTION: Heat radiation shield plates 6a, which are cooled with liquid nitrogen, and two heat radiation shield plates 6b, which are cooled with evaporated helium gas, are arranged between the outer wall of an inner container 5 and the outer wall of a vacuum container 2 and between the axial direction wall of the inner container 5 and the axial direction wall of the vacuum container 2. The number of the heat radiation shield plates, which are positioned at the inner side is made fewer than the number of the heat shield plates positioned at the outside by one plate in this way. The area of the inner wall of the inner container 5 is inherently narrower than the area of the outer wall. Therefore, the quantity of heat, which intrudes from the inner wall, is less. Even if the heat radiation shield plates is decreased by one, the heat insulating performance is not hampered.
SATO AKIO
YASUDA SATOSHI
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