Patent ID: 8590319

Claim:
A multi-stage pulse tube refrigerator, comprising: a first stage regenerator tube including a heat exchanger; a second stage regenerator tube; a first stage pulse tube; a second stage pulse tube; a first cooling stage connected to a cold end of the first stage regenerator tube and a cold end of the first stage pulse tube; and a second cooling stage connected to a cold end of the second stage regenerator tube and a cold end of the second stage pulse tube, wherein the cold end of the first stage regenerator tube is in communication with the first stage pulse tube via a first flow path and in communication with a hot end of the second stage regenerator tube via a second flow path; the first flow path is configured such that a heat exchange occurs between the heat exchanger and a refrigerant gas flowing through the first flow path; and the second flow path is configured such that the refrigerant gas flowing through the second flow path is fluidically isolated from the heat exchanger, wherein the refrigerant gas flows to and from the second stage regenerator tube without contacting the heat exchanger.