Stirling/pulse tube hybrid cryocooler with gas flow shunt

A two-stage hybrid cryocooler (20) includes a first-stage Stirling expander (22) having a first-stage regenerator (24) having a first-stage-regenerator inlet (26) a nd a first-stage-regenerator outlet (28), and a second-stage pulse tube expander (32). The second-stage pulse tube expander (32) includes a second-stage regenerator (34) having a second-stage regenerator inlet (36) in gaseous communication with the first-stage regenerator outlet (28), and a second-stage regenerator outlet (40), and a pulse tube (42) having a pulse-tube inlet (44) in gaseous communication with the second-stage regenerator outlet (40), and a pulse-tube outlet (48). The second-stage regenerator (34) and the pulse tube (42) together provide a first gas-flow path (43) between the first-stage regenerator (24) and the pulse-tube outlet (48). A pulse tube pressure drop structure (50) has a pulse-tube-pressure-drop inlet in gaseous communication with the pulse-tube outlet (48), and a pulse-tube pressure-drop outlet, and a gas volume is in gaseous communication with the pulse-tube pressure-drop outlet. A gas flow shunt (60) provides gaseous communication between the first-stage regenerator (24) and the pulse-tube outlet (48). The gas flow shunt (60) provides a second gas-flow path (62) between the first-stage regenerator (24) and the pulse-tube outlet (48).