A rotary valve unit includes a rotary valve and a reversible motor. The rotary valve operates according to a cooling valve timing for cooling a pulse tube cryocooler when the reversible motor rotates in a forward direction and is operated according to a heating valve timing for heating the pulse tube cryocooler when the reversible motor rotates in a backward direction. The cooling valve timing is designed to generate a working gas pressure oscillation in a pulse tube and apply a first phase delay to a working gas displacement oscillation in the pulse tube with respect to the working gas pressure oscillation. The heating valve timing is designed to generate the working gas pressure oscillation in the pulse tube and apply a second different phase delay to the working gas displacement oscillation in the pulse tube with respect to the working gas pressure oscillation.

A rotary valve of a cryocooler includes a valve stator, a valve rotor, a rotation member that rotates the valve rotor around an axis with respect to the valve stator, and a rotor holder connected to the valve rotor so as to rotate around an axis together with the valve rotor, and forming a low pressure section having a pressure lower than an ambient pressure between the valve rotor and the rotor holder so as to reduce an axial force of pressing the valve rotor against the valve stator. The rotation member is connected to the rotor holder so as to rotate the valve rotor around the axis via the rotor holder. The rotor holder is disposed between the rotation member and the valve rotor in an axial direction, and is movable in the axial direction with respect to the rotation member.

A cryogenic cooling system (CCS) includes a cylindrical housing having a first end and a second end. Also, the CCS includes a displacer disposed within the cylindrical housing and reciprocatingly driven between the first end and the second end of the cylindrical housing to compress or expand a refrigerant gas in a gas chamber. Further, the CCS includes a tubing unit coupled to the second end of the cylindrical housing and disposed adjacent to the at least one superconducting unit, wherein the tubing unit is configured to circulate the refrigerant gas received from the cylindrical housing through the tubing unit to absorb the at least one heat load imposed on the at least one superconducting unit to generate heated refrigerant gas, and convey the heated refrigerant gas to the gas chamber of the cylindrical housing to reduce or maintain a temperature of the at least one superconducting unit.

A cryocooler includes a cold head, a valve unit which includes a rotary valve configured to periodically switch a pressure of a working gas in the cold head between a first high pressure and a second high pressure lower than the first high pressure and a valve motor configured to rotate the rotary valve, the valve unit having a rotation angle range in which the rotary valve seals the working gas having the second high pressure in the cold head, a cryocooler control unit configured to control the valve motor, a cryocooler stop instruction unit configured to output a cryocooler stop instruction signal to the cryocooler control unit, and a valve stop timing control unit configured to control the valve motor to stop the rotary valve in the rotation angle range, according to the cryocooler stop instruction signal.

A rotary valve mechanism includes a valve stator having a stator recessed portion and a valve rotor having a rotor recessed portion. The rotor recessed portion is formed in the valve rotor such that a rotor-recessed-portion front edge line passes through a stator-recessed-portion front edge line and the rotor recessed portion fluidally communicates with the stator recessed portion at a first phase of rotary-valve-mechanism rotation, and a rotor-recessed-portion rear edge line passes through a stator-recessed-portion rear edge line and the rotor recessed portion is fluidally separated from the stator recessed portion at a second phase thereof, and a shape of the rotor-recessed-portion front edge line coincides with a shape of the stator-recessed-portion front edge line such that the rotor-recessed-portion front edge line overlaps the stator-recessed-portion front edge line at the first phase.

A rotary valve mechanism of a cryocooler includes a valve rotor and a valve stator. A rotor recessed portion is formed such that the rotor recessed portion fluidally communicates with a stator recessed portion at a first opening degree at a second phase of a valve rotation. The valve rotor includes a first rotor communication groove and/or a second rotor communication groove formed in the valve rotor such that the rotor recessed portion fluidally communicates with the stator recessed portion at an opening degree which is smaller than the first opening degree at a first phase preceding the second phase, and/or the valve stator includes a stator communication path formed in the valve stator such that the rotor recessed portion fluidally communicates with the stator recessed portion at an opening degree which is smaller than the first opening degree at the first phase preceding the second phase.

A rotary valve mechanism of a cryocooler includes a valve rotor and a valve stator. A rotor recessed portion is formed such that the rotor recessed portion fluidally communicates with a stator recessed portion at a first opening degree at a second phase of a valve rotation. The valve rotor includes a first rotor communication groove and/or a second rotor communication groove formed in the valve rotor such that the rotor recessed portion fluidally communicates with the stator recessed portion at an opening degree which is smaller than the first opening degree at a first phase preceding the second phase, and/or the valve stator includes a stator communication path formed in the valve stator such that the rotor recessed portion fluidally communicates with the stator recessed portion at an opening degree which is smaller than the first opening degree at the first phase preceding the second phase.

A cryogenic cooling system (CCS) includes a cylindrical housing having a first end and a second end. Also, the CCS includes a displacer disposed within the cylindrical housing and reciprocatingly driven between the first end and the second end of the cylindrical housing to compress or expand a refrigerant gas in a gas chamber. Further, the CCS includes a tubing unit coupled to the second end of the cylindrical housing and disposed adjacent to the at least one superconducting unit, wherein the tubing unit is configured to circulate the refrigerant gas received from the cylindrical housing through the tubing unit to absorb the at least one heat load imposed on the at least one superconducting unit to generate heated refrigerant gas, and convey the heated refrigerant gas to the gas chamber of the cylindrical housing to reduce or maintain a temperature of the at least one superconducting unit.

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 gas replacement method for an expander of a cryocooler, the expander including an expander cylinder, a pressure switching valve that switches a pressure inside the expander cylinder, a connection flow path from the pressure switching valve to the expander cylinder, and an expander motor that drives the pressure switching valve, includes connecting a nonflammable gas source to the connection flow path or the expander cylinder, and purging a residual gas in the expander cylinder with a nonflammable gas from the nonflammable gas source while the expander motor is stopped.