This disclosure describes systems, methods, and apparatus for improving the cooldown time, or efficiency of cooling systems, for a low-frequency one or multi-stage pulse-tube refrigerator. More specifically, actuation is performed on the driving frequency of the oscillating pressure and flow, on flow resistance of valves in the acoustic network that terminate the LF-OPTR or LF-DIPTR, and/or on the asymmetric flow resistance of the bypass valves in a LF-DIPTR's flow network. The actuation of these parameters is informed by measurements of the output pressure or output-input differential pressure at the steady flow compressor, the temperature of each stage of the refrigerator, and the temperature difference between the final stage and upper stages of the refrigerator, to name a few non-limiting examples.

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.

In a pulse tube refrigerator, a gas flow passage is connected to a high-temperature end of a low-temperature side pulse tube and a compressor, such that a working gas flows in the gas flow passage. The gas flow passage includes: a first flow passage connected to the high-temperature end of the low-temperature side pulse tube; a second flow passage connected to the compressor and having an outlet facing an outlet of the first flow passage; and a housing that gastightly accommodates the outlet of the first flow passage and the outlet of the second flow passage. The housing has a gastight space communicating with the outlet of the first flow passage and the outlet of the second flow passage, the gastight space located on a side of the low-temperature side pulse tube with respect to the outlet of the first flow passage.

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 connecting device in a pulse tube cooler system branches such that a first line branch (11) has a first flexible line segment (4a) and a second line branch (12) has a second flexible line segment (4b), the flexible line segments being arranged in parallel with and offset from one another. The flexible line segments each have a front segment end (17, 18) and a rear segment end (19, 20), the front segment end (17) of the first flexible line segment (4a) and the rear segment end (20) of the second flexible line segment (4b) are rigidly connected to one another, the rear segment end (19) of the first flexible line segment (4a) and the front segment end (18) of the second flexible line segment (4b) are rigidly connected to one another, and there is no continuous rigid connection between the control valve and the cold head.

In a cryogenic refrigerator, a displacer defines an internal space, and circulates a working fluid in the internal space. A cylinder houses the displacer such as to enable it to reciprocate, and, at an interval from the bottom side of the displacer, forms an expansion space for the working fluid. A cooling stage is provided along an outer circumferential and bottom portion of the cylinder, in a location corresponding to the expansion space. A heat exchanger is arranged inside the expansion space and is thermally connected to the cooling stage. An end portion of the displacer on its expansion-space side has an opening that serves as an entry/exit port between the internal space and the expansion space for the working fluid. A working-fluid flow channel connects the internal space and the expansion space via the heat exchanger.

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.

A first regenerator of a regenerative refrigerator includes a first regenerator member and a first cylinder accommodating the first regenerator member. A second regenerator includes a second regenerator member and a second cylinder accommodating the second regenerator member and may be connected to a low temperature end of the first regenerator. A gas pipe guides a coolant gas discharged from the first regenerator to a portion in the middle of the second regenerator. The gas pipe may include a plurality of gas relief holes in the middle of the gas pipe.

A connecting device in a pulse tube cooler system branches such that a first line branch (11) has a first flexible line segment (4a) and a second line branch (12) has a second flexible line segment (4b), the flexible line segments being arranged in parallel with and offset from one another. The flexible line segments each have a front segment end (17, 18) and a rear segment end (19, 20), the front segment end (17) of the first flexible line segment (4a) and the rear segment end (20) of the second flexible line segment (4b) are rigidly connected to one another, the rear segment end (19) of the first flexible line segment (4a) and the front segment end (18) of the second flexible line segment (4b) are rigidly connected to one another, and there is no continuous rigid connection between the control valve and the cold head.

A cryocooling system includes a compressor, a refrigerator, and a controller, which is communicatively coupled to the compressor and the refrigerator. The compressor is configured to be driven at a drive frequency. The refrigerator is coupled to the compressor via a first fluid path and includes a cold heat exchanger, an output, a reservoir, and a flow resistor. The flow resistor controls fluid flow along a second fluid path between the output and the reservoir. The controller optimizes a rate of cooling of the cold heat exchanger by adjusting both a drive frequency of the compressor and a resistance of the flow resistor along the second fluid path.