Hybrid double-inlet valve for pulse tube cryocooler

A Gifford-McMahon (GM) type double-inlet pulse tube cryocooler system for providing cooling at cryogenic temperatures, comprising;

• a compressor supplying gas at a supply pressure through a supply line and receiving gas at a return pressure through a return line;
• a valve assembly connected to the supply and return lines;
• and
• a pulse tube cold head connected to the valve assembly, wherein the valve assembly cycles gas between the supply pressure and the return pressure to the pulse tube cold head through a connecting line, the pulse tube cold head comprising:
• at least one regenerator having a warm end and a cold end;
• at least one pulse tube having a warm end and a cold end;
• at least one double-inlet valve comprising:
• a fixed restrictor;
• and
• a needle valve coupled to the fixed restrictor in parallel, wherein a flow through the needle valve is asymmetric;
• a buffer volume connected to the warm end of the pulse tube;
• a first line extending from the connecting line to the warm end of the regenerator, wherein the double-inlet valve is connected to the first line;
• a second line connecting the cold end of the regenerator to the cold end of the pulse tube;
• and
• a third line from the warm end of the pulse tube to the double-inlet valve and to the buffer volume through a single-inlet valve.