Magnetic shield structure of cryogenic refrigerators and cryogenic refrigerators

摘要

To suppress degradation of refrigeration performance of a cryogenic refrigerator with a magnetic shield, used in a helium atmosphere.SOLUTION: A cryogenic refrigerator 1 comprises: a magnetic shield 70 which axially extends along a two-stage cylinder 51 from a two-stage cooling stage 72 at the outside of the two-stage cylinder 51, and is disposed with an axial separation distance from a one-stage cooling stage 35, an annular space 78 opened to helium atmosphere being formed between the two-stage cylinder 51 and the magnetic shield 70, and an axial depth of the annular space 78 being longer than the axial separation distance; and a convection suppressing member 74 which suppresses axial convection of helium gas in the annular space 78 caused by temperature difference between the two-stage cylinder 51 and the magnetic shield 70, and is disposed in the annular space 78, and has an axial length longer than the axial separation distance.SELECTED DRAWING: Figure 1