Pulse tube refrigerator

Abstract

In a pulse tube refrigerator, a first pulse tube has a low-temperature end, and a high-temperature end connected to a compressor. A first regenerator has a low-temperature end connected to the low-temperature end of the first pulse tube, and a high-temperature end connected to the compressor. A second pulse tube has a high-temperature end connected to the compressor, and a low-temperature end having a lower temperature than the low-temperature end of the first pulse tube. A second regenerator has a high-temperature end, and a low-temperature end connected to the low-temperature end of the second pulse tube, and is arranged side by side with the second pulse tube. The second pulse tube includes a narrowed portion nearer a low-temperature end side than a position corresponding to the high-temperature end of the second regenerator.

What is claimed is: 
     
         1 . A pulse tube refrigerator comprising:
 a compressor that compresses a refrigerant gas;   a first pulse tube that has a low-temperature end and a high-temperature end connected to the compressor;   a first regenerator that has a low-temperature end connected to the low-temperature end of the first pulse tube and a high-temperature end connected to the compressor;   a second pulse tube that has a high-temperature end connected to the compressor and a low-temperature end having a lower temperature than the low-temperature end of the first pulse tube; and   a second regenerator that has a high-temperature end and a low-temperature end connected to the low-temperature end of the second pulse tube and is arranged side by side with the second pulse tube,   wherein the second pulse tube includes a narrowed portion nearer a low-temperature end side than a position corresponding to the high-temperature end of the second regenerator.   
     
     
         2 . The pulse tube refrigerator according to  claim 1 ,
 wherein the second regenerator includes:   a first regenerator material that is arranged on a high-temperature side; and   a second regenerator material that is arranged on a low-temperature side and is adjacent to the first regenerator material, and   wherein the narrowed portion is provided nearer the low-temperature end side than a position corresponding to a boundary between the first regenerator material and the second regenerator material in the second regenerator.   
     
     
         3 . The pulse tube refrigerator according to  claim 1 ,
 wherein the narrowed portion is provided in a region where the temperature of the refrigerant gas flowing through the second pulse tube reaches 8 K to 30 K.   
     
     
         4 . The pulse tube refrigerator according to  claim 1 ,
 wherein the narrowed portion increases gradually at a boundary portion on a high-temperature end side with another region until the flow path cross-sectional area thereof reaches a flow path cross-sectional area in the other region.   
     
     
         5 . The pulse tube refrigerator according to  claim 1 ,
 wherein the narrowed portion increases gradually at a boundary portion on a low-temperature end side with another region until the flow path cross-sectional area thereof reaches a flow path cross-sectional area in the other region.   
     
     
         6 . The pulse tube refrigerator according to  claim 1 ,
 wherein the second pulse tube is a pulse tube at a last stage on a low-temperature side, and   wherein the second regenerator is a regenerator at the last stage on the low-temperature side.   
     
     
         7 . A pulse tube refrigerator comprising:
 a compressor that compresses a refrigerant gas;   a first pulse tube that has a low-temperature end and a high-temperature end connected to the compressor;   a first regenerator that has a low-temperature end connected to the low-temperature end of the first pulse tube and a high-temperature end connected to the compressor;   a second pulse tube that has a high-temperature end connected to the compressor and a low-temperature end having a lower temperature than the low-temperature end of the first pulse tube; and   a second regenerator that has a high-temperature end and a low-temperature end connected to the low-temperature end of the second pulse tube and is arranged side by side with the second pulse tube,   wherein the second pulse tube includes a narrowed portion in a region where the temperature of the refrigerant gas flowing through the second pulse tube reaches 8 K to 30 K.