| 摘要 |
PURPOSE:To contrive a higher refrigeration capacity without any complication of construction by providing a main body of a cryogenic refrigerator of the single-stage expansion type and a cooling means for pre-cooling a heat- exchanging stage. CONSTITUTION:A main body 51 of a cryogenic refrigerator is composed of a single-stage expansion type GM refrigerator. When a pre-cooling refrigerator 52 is operated, a heat-transmitting block 86 is cooled to about 40K, and a heat- transmitting block 87 is cooled to about 8K. When a displacer 62 is moved toward the top dead center, a high-pressure helium gas is cooled by a cold- accumulating material 70 in a fluid passage 74, before flowing to a heat- exchanging stage 72. The stage 72 is kept at about 45K, so that the helium gas flowing out of a passage has a temperature of about 45K. A heat-exchanging stage 73 is kept at about 12K, so that the helium gas passed through a fluid passage 78 has a temperature of about 12K. The helium gas is then cooled to about 4.2K by a cold-accumulating material 81 in a fluid passage 76, before flowing into an expansion chamber 90. When a high-pressure valve 66 is closed and a low-pressure valve 67 is opened, the helium gas is expanded to produce cold, whereby a cooling stage 83 is cooled to a low temperature. |
