A pulse tube cryocooler includes a pulse tube that includes a tube inner space, and an integral flow straightener that includes a flow straightening layer disposed to face the tube inner space so as to straighten a refrigerant gas flow from the tube inner space or into the tube inner space and a heat exchange layer formed integrally with the flow straightening layer outside the flow straightening layer with respect to the tube inner space so as to exchange heat with the refrigerant gas flow by contact with the refrigerant gas flow and is disposed at a low-temperature end and/or a high-temperature end of the pulse tube. The flow straightening layer includes a plurality of protrusions that protrude from the heat exchange layer toward the tube inner space.

A thermoacoustic refrigeration assembly includes a resonating tube having a first end and a second end; a first mechanical oscillator at the first end; a second mechanical oscillator at the second end; and a thermoacoustic stack sandwich disposed along a length of the resonating tube through which gas travels. The stack sandwich includes a first outboard heat exchanger on a first side of the stack sandwich facing the first mechanical oscillator, a second outboard heat exchanger on a second side of the stack sandwich facing the second mechanical oscillator, and a center heat exchanger disposed between the first outboard heat exchanger and the second outboard heat exchanger.

A heat/acoustic wave conversion component includes a partition wall that defines a plurality of cells extending from a first end face to a second end face and mutually converts heat exchanged between the partition wall and the working fluid and energy of acoustic waves resulting from oscillations of the working fluid. Hydraulic diameter HD of the heat/acoustic wave conversion component is 0.4 mm or less, where the hydraulic diameter HD is defined as HD=4×S/C, where S denotes an area of a cross-section of each cell perpendicular to the cell extending direction and C denotes a perimeter of the cross section. The heat/acoustic wave conversion component has an open frontal area at each end face of 60% or more and 93% or less. The partition wall has arithmetic surface roughness (Ra) at the surface of 3 μm or more and 20 μm or less.

A cryogenic refrigerator includes a pulse tube cryocooler including a pulse tube, and a pulse tube cryocooler rotating mechanism that rotatably supports the pulse tube cryocooler allowing it to be changed from a cooling posture to a heating posture. When the pulse tube cryocooler is in the cooling posture, an inclination angle formed between a vertical line and a center axis of the pulse tube is a first angle, and when the pulse tube cryocooler is in the heating posture, the inclination angle is a second angle. In a case where the inclination angle formed when a cold end of the pulse tube faces vertically downward is defined as zero degrees and the inclination angle formed when the cold end of the pulse tube faces vertically upward is defined as 180 degrees, the second angle is larger than the first angle.

A cold storage material of an embodiment includes a rare earth oxysulfide containing at least one rare earth element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and a first group element of 0.001 atom % or more and 10 atom % or less, in which a maximum value of volume specific heat in a temperature range of 2 K or more and 10 K or less is 0.5 J/(cm.sup.3.Math.K) or more.

A cryogenic device includes: a hermetic container; a cryocooler including a mounting portion mounted on the container, a connecting part extending from the mounting portion into the container in an axial direction of the cryocooler, and a cooling stage attached to the connecting part and disposed in the container; and a member to be cooled that is disposed in the container with a gap, which is configured to allow heat to be exchanged, between the cooling stage and the member. The cooling stage includes a cold fin extending in a direction perpendicular to the axial direction. A fin receiving groove recessed in the direction perpendicular to the axial direction is formed in the member to be cooled and extends in the axial direction, and the member to be cooled receives the cold fin in the fin receiving groove with the gap.

A thermoacoustic refrigeration assembly includes a resonating tube having a first end and a second end; a first mechanical oscillator at the first end; a second mechanical oscillator at the second end; and a thermoacoustic stack sandwich disposed along a length of the resonating tube through which gas travels. The stack sandwich includes a first outboard heat exchanger on a first side of the stack sandwich facing the first mechanical oscillator, a second outboard heat exchanger on a second side of the stack sandwich facing the second mechanical oscillator, and a center heat exchanger disposed between the first outboard heat exchanger and the second outboard heat exchanger.

A cryogenic device includes: a hermetic container; a cryocooler including a mounting portion mounted on the container, a connecting part extending from the mounting portion into the container in an axial direction of the cryocooler, and a cooling stage attached to the connecting part and disposed in the container; and a member to be cooled that is disposed in the container with a gap, which is configured to allow heat to be exchanged, between the cooling stage and the member. The cooling stage includes a cold fin extending in a direction perpendicular to the axial direction. A fin receiving groove recessed in the direction perpendicular to the axial direction is formed in the member to be cooled and extends in the axial direction, and the member to be cooled receives the cold fin in the fin receiving groove with the gap.

The disclosed subject matter includes an active control alternating-direct flow hybrid mechanical cryogenic system, and relates to the field of cryogenic refrigeration technologies. The active control alternating-direct flow hybrid mechanical cryogenic system includes a main compressor, a Stirling cold finger, an intermediate heat exchanger, a pulse tube cold finger, a first dividing wall type heat exchanger, a final precooled heat exchanger, a second dividing wall type heat exchanger, and an evaporator that are communicated successively, where the second dividing wall type heat exchanger is connected to the evaporator through a second connecting pipeline, and a throttling element is disposed on the second connecting pipeline; a pulse tube cold head of the pulse tube cold finger is communicated with the final precooled heat exchanger through a cold chain; and a check valve is disposed on the intermediate heat exchanger.

An apparatus includes a heat exchanger configured to transfer heat to a fluid and to absorb heat from the fluid as the fluid flows between a warm end and a cold end of a cryocooler. The heat exchanger includes at least one section having a substrate of at least one allotropic form of carbon and a layer of nanoparticles on or over the substrate. The heat exchanger could include multiple sections, and each section could include one of multiple substrates and one of multiple layers of nanoparticles. The heat exchanger can further include pores through the multiple sections of the heat exchanger, where the pores are configured to allow the fluid to flow through the heat exchanger and to contact the substrates and the layers of nanoparticles. The nanoparticles could include at least one lanthanide element or alloy, and the substrate could include carbon nanotubes or graphene.