A cryocooler includes a first cylinder and a second cylinder, a first cooling stage, a second cooling stage, a radiation shield which is cooled by the first cooling stage, accommodates the second cooling stage, and shields the second cooling stage from radiant heat from an outside, and a temperature sensor which detects a temperature of the second cooling stage. A working gas is supplied into the first cylinder and the second cylinder to be expanded and is exhausted to the outside, an insertion hole through which an output cable of the temperature sensor passes through from an inside to an outside of the radiation shield is provided in the radiation shield, and the insertion hole is configured such that the radiant heat entering the radiation shield from the outside of the radiation shield is not directly radiated to the second cooling stage.

A cryogenic cooling apparatus includes: a vacuum container configured to form an airtight space capable of forming a vacuum and accommodate a first cooling object; a first bellows connected to a peripheral portion of an opening provided in the vacuum container and configured to form an expandable and contractible communication space; a flange provided at a tip of the first bellows on a side opposite to the opening of the vacuum container and configured to fix a refrigerator; a first sleeve connected to a peripheral edge portion of an opening of the flange, into which the refrigerator is inserted, and configured to form a first accommodation space; a first heat-transfer block provided at a tip of the first sleeve on a side opposite to the flange and thermally connected to the first cooling object by being brought into contact with a first cooling block of the refrigerator; and a second bellows formed in a part of the first sleeve and configured to expand or contract the accommodation space depending on the refrigerator inserted into the accommodation space.

A pulse tube cryocooler includes a cold head including a pulse tube and a radiator thermally coupled to a high-temperature end of the pulse tube, and a forced cooler that forcedly cools the radiator in a cool-down operation of the pulse tube cryocooler from an ambient temperature to a cryogenic temperature.

A pulse tube refrigerator (PTR) comprising a pedestal head and a regenerator tube assembly is provided having particular application in cooling a Magnetic Resonance Imaging system. The PTR comprises a pedestal head and at least one cooled stage, the at least one cooled stage being mounted to a distal end, with respect to the pedestal head, of each of an associated regenerator tube and an associated pulse tube, the associated regenerator tube and associated pulse tube together providing pressurized coolant gas to the at least one cooled stage, wherein the associated regenerator tube and the associated pulse tube are elongate along substantially parallel axes; and further arranged, wherein, the displacements of the distal ends of each of the associated regenerator tube and the associated pulse tube in response to the cyclical changes in coolant pressure, are substantially the same when the pulse tube refrigerator is in use.

A pulse tube refrigerator includes a compressor, a regenerator to which a refrigerant gas is discharged from the compressor and from which the refrigerant gas returns to the compressor, a pulse cube including a low-temperature end connected to the low-temperature end of the regenerator, and a flow rate controller provided at the low-temperature end of the regenerator. The flow rate controller is configured to control the flow rate of a first DC flow flowing from the regenerator toward the pulse tube and the flow rate of a second DC flow flowing from the pulse tube toward the regenerator, so that the flow rate of the first DC flow is greater than the flow rate of the second DC flow.

A disclosed cryogenic refrigerator includes a first refrigerator including a compressor, a regenerator which performs intake or ejection of a refrigerant gas relative to the compressor, and a pulse tube whose low temperature end is connected to a low temperature end of the regenerator; a second refrigerator having an output smaller than the first refrigerator; a connecting pipe which performs intake and ejection of the refrigerant gas relative to a high temperature end of the pulse tube and the second refrigerator; and a flow control valve which is provided in the connecting pipe and performs a flow control of the refrigerant gas flowing inside the connecting pipe.

A Stirling-type pulse tube refrigerator includes: a regenerator that has a low temperature end and high temperature end; a pulse tube that is arranged coaxially with the regenerator, and that is connected to the regenerator so as to enable working gas to circulate therebetween; a low temperature heat exchanger that is disposed in the low temperature end of the regenerator, and that has a gas flow passage serving as a flow passage for the working gas; and a flow straightener that is disposed in an end portion, on a side close to the low temperature heat exchanger, out of end portions of the pulse tube. The gas flow passage and the flow straightener are spaced away from each other, and a length of a connecting passage connecting the gas flow passage and the flow straightener is equal to or shorter than 10% of a length of the pulse tube.

A refrigerator includes a regenerator, a low-temperature end heat exchanger, a pulse tube, a high-temperature end heat exchanger, and a phase adjustment mechanism, connected in that order. A draft tube is provided inside the regenerator, paralleling the regenerator's axis, and the draft tube can extend into the low-temperature end heat exchanger.

According to an aspect of some embodiments of the present invention there is provided a method for converting energy. The method comprises receiving energy from an external source, using the received energy for inducing a mass exchange process to release thermodynamic energy, and converting the thermodynamic energy directly into electrical energy at sufficient amount for performing work therewith. In some embodiments of the present invention, a portion of the released energy is converted to a pressure wave, and the mechanical energy constituted by the pressure wave is converted to non-mechanical energy.

A thermoacoustic machine including a device for measuring at least one parameter representative of a temperature of a first external source and/or of a second external source, and a control device configured to modulate the acoustic power generated by one or more acoustic sources such that the temperature of one said external source connected to one or more thermoacoustic cells of the machine reaches or remains substantially identical to a setpoint temperature is disclosed.