Pulse tube cryogenic cooler with tunable inertance tube

A cryogenic cooler comprising:

• a pressure generator for generating oscillating pressure waves in, and mass flow of, a contained working fluid;
• an aftercooler fluidly communicating with the pressure generator, for transferring heat from the working fluid;
• a regenerator fluidly communicating with the aftercooler, for absorbing heat from the working fluid flowing through the regenerator and storing absorbed heat, and for transferring stored heat to the working fluid;
• a cold heat exchanger fluidly communicating with the regenerator, for transferring heat to the working fluid;
• a pulse tube fluidly communicating with the cold heat exchanger, for compressing and expanding the working fluid and thereby creating heat flow in the working fluid;
• a hot heat exchanger fluidly communicating with the pulse tube for transferring heat from the working fluid;
• an inertance tube fluidly communicating a fluid reservoir with the hot heat exchanger and having an adjustable inductance, for causing a phase shift between the pressure waves and the mass flow;
• a tuning mechanism for adjusting the adjustable inductance including:
• an aperture having a state comprised of an open state for obtaining a maximum fluid communication between the inertance tube and the reservoir, or a closed state for reducing fluid communication between the inertance tube and the reservoir to a reduced fluid communication less than the maximum fluid communication;
• a tubular sleeve slidable over the inertance tube and having a shaped leading edge;
• and
• the aperture having a sealing valve for changing the state of the aperture upon contact between the leading edge and the sealing valve, wherein
• the aperture remains in the open state in absence of contact between the sleeve and the sealing valve, whereby the cryogenic cooler has an improved Carnot efficiency.