CPC F25B 9/14 (2013.01) [F25B 41/20 (2021.01); F25B 49/02 (2013.01); F25B 2309/1428 (2013.01); F25B 2321/00 (2013.01)] | 18 Claims |
1. A cryogenic refrigerator comprising:
a refrigeration volume having warm and cold ends;
a reciprocating displacer within the refrigeration volume;
a pneumatic drive volume at the warm end of the refrigeration volume;
a drive piston in the pneumatic drive volume coupled to the displacer;
refrigeration volume valving controlling cyclic supply and exhaust of a pressurized refrigerant gas to and from the warm end of the refrigeration volume;
drive valving providing supply and exhaust of drive fluid to and from the pneumatic drive volume to apply driving force to the drive piston;
magnets applying force to the piston in addition to the driving force applied by the drive fluid; and
an electronic controller controlling the drive valving with a drive control signal that varies through stroke of the drive piston to cause the drive piston to follow a programmed displacement profile through stroke of the drive piston.
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