Compressor unit of a split stirling cryogenic refrigeration device

A compressor unit of a split Stirling cryogenic refrigeration device, the compressor unit comprising:

• a compression chamber that is connectable via a transfer lure to an expander unit of the refrigeration device;
• a piston that is configured to be moved back and forth along a longitudinal axis to alternately compress and decompress a gaseous working agent in the compression chamber;
• and
• a linear electromagnetic actuator that is configured to drive the piston, the actuator comprising:
• a stator assembly that includes a driving coil that is wound about the longitudinal axis and that is enclosed within a toroidal back iron except, for a coaxial cylindrical gap in a radially outward facing surface of the toroidal back iron;
• and
• a movable assembly that is connected to the piston, the movable assembly comprising two movable permanent magnets separated by a ferromagnetic spacer that are located radially exteriorly to the stator assembly, the two movable permanent magnets being magnetically polarized parallel to the longitudinal axis and oppositely to one another such that an alternating electrical current that flows through the driving coil causes the movable assembly to move back and forth parallel to the longitudinal axis so as to periodically drive the piston into and out of the compression chamber.