Heating device for cryogenic refrigerator

Abstract

A heating device (10) for a cryogenic refrigerator, the heating device (10) being inserted into a cylinder (111) of the cryogenic refrigerator, comprises: a first heater block (11) which is accommodated in the cylinder (111); and a first urging member (12) which presses the first heater block (11) against a first cylinder inner bottom surface (121AB) of the cylinder (111).

Description

Cryogenic refrigerator heating device

[0001] The present disclosure relates to a heating device for a cryogenic refrigerator.

[0002] The heating device of the cryogenic refrigerator includes a first heating block, a second heating block, and a flange. The flange holds the first heating block and the second heating block. The first heating block and the second heating block are aligned in the extension direction of the flange.

[0003] The heating device is inserted into a cylinder of a cryogenic refrigerator. The cylinder includes a first cooling stage and a second cooling stage. The first cooling stage and the second cooling stage are aligned in the direction of extension of the cylinder. When the heating device is inserted into the cylinder, the first heating block is positioned near the first cooling stage, and the second heating block is positioned near the second cooling stage. Helium gas is supplied between the first heating block and the first cooling stage, and between the second heating block and the second cooling stage. Therefore, thermal conduction of the helium gas occurs from each heating block to the cooling stage located near that heating block (see, for example, Patent Document 1).

[0004] Japanese Patent Application Laid-Open No. 2022-30736

[0005] In a heating device of a cryogenic refrigerator, it is required to improve the efficiency of heat conduction from the heating device to the cylinder that is the object to be heated.

[0006] A heating device for a cryogenic refrigerator according to one aspect is inserted into a cylinder of the cryogenic refrigerator and includes a heater block accommodated in the cylinder and a biasing member that presses the heater block against an inner bottom surface of the cylinder.

[0007] In the heating device for the cryogenic refrigerator described above, the heater block is pressed against the bottom surface of the cylinder by the biasing member, so that the heater block comes into direct contact with the bottom surface of the cylinder, thereby improving the efficiency of heat conduction from the heater block to the bottom surface of the cylinder.

[0008] The heating device of the above-mentioned cryogenic refrigerator may further include a cylindrical portion having an opening to which the heater block is attached and accommodated in the cylinder, and the thermal conductivity of the cylindrical portion may be lower than the thermal conductivity of the heater block.

[0009] According to the heating device of the above-mentioned cryogenic refrigerator, the thermal conductivity of the cylindrical portion is lower than that of the heater block, so that heat conduction from the heater block to the cylindrical portion is suppressed, and as a result, the amount of heat conducted from the heater block to the bottom surface inside the cylinder is less likely to decrease.

[0010] In the heating device for a cryogenic refrigerator, the heater block may be made of copper or aluminum, and the cylindrical portion may be made of stainless steel. According to the heating device for a cryogenic refrigerator, the thermal conductivity of the cylindrical portion is lower than the thermal conductivity of the heater block attached to the cylindrical portion.

[0011] In the heating device of the above-mentioned cryogenic refrigerator, the cylinder inner bottom surface may be the first cylinder inner bottom surface, the heater block may be a first heater block, the urging member may be a first urging member, and the device may further include a second heater block located on the opposite side of the first heater block from the first urging member and housed in the cylinder, and a second urging member located between the first heater block and the second heater block and pressing the second heater block against the second cylinder inner bottom surface of the cylinder.

[0012] According to the heating device of the above-mentioned cryogenic refrigerator, the heating device is provided with a second biasing member that presses the second heater block against the inner bottom surface of the second cylinder, thereby increasing the efficiency of heat conduction from the heating device to the cylinder at both the inner bottom surface of the first cylinder and the inner bottom surface of the second cylinder.

[0013] The heating device of the above-mentioned cryogenic refrigerator may further include a second cylindrical portion that has an opening to which the second heater block is attached and is housed in the cylinder, and the thermal conductivity of the second cylindrical portion may be lower than the thermal conductivity of the second heater block.

[0014] According to the heating device of the above-mentioned cryogenic refrigerator, the thermal conductivity of the second cylindrical portion is lower than that of the second heater block, so heat conduction from the second heater block to the second cylindrical portion is suppressed, and as a result, the amount of heat conducted from the second heater block to the inner bottom surface of the second cylinder is less likely to decrease.

[0015] In the heating device of the above-mentioned ultra-low temperature refrigerator, the cylindrical portion accommodated in the cylinder may be a first cylindrical portion, the first heater block and the first cylindrical portion are included in a first cylindrical body, the second heater block and the second cylindrical portion are included in a second cylindrical body, and the position of the second cylindrical body relative to the first cylindrical body may be changed in the axial direction of the first cylindrical body.

[0016] Due to differences in processing accuracy and differences in thermal contraction caused by temperature distribution, the length between the inner bottom surface of the first cylinder and the inner bottom surface of the second cylinder may differ from the distance between the bottom surface of the first heater block and the bottom surface of the second heater block. Even in this case, with the heating device for a cryogenic refrigerator described above, it is possible to simultaneously press the first heater block against the inner bottom surface of the first cylinder and the second heater block against the inner bottom surface of the second cylinder by adjusting the position of the second cylindrical body relative to the first cylindrical body in the axial direction of the first cylindrical body.

[0017] In the heating device for a cryogenic refrigerator, the second heater block may be made of copper or aluminum, and the second cylindrical portion may be made of stainless steel. According to the heating device for a cryogenic refrigerator, the thermal conductivity of the second cylindrical portion is lower than the thermal conductivity of the second heater block attached to the second cylindrical portion.

[0018] Fig. 1 is a schematic diagram showing the structure of a superconducting magnet equipped with a cryogenic refrigerator that is heated during maintenance. Fig. 2 is a cross-sectional view showing the structure of a heating device. Fig. 3 is a cross-sectional view showing the structure of a cylinder into which the heating device is inserted. Fig. 4 is a cross-sectional view showing the structure of the heating device inserted into the cylinder.

[0019] A heating device 10 of a cryocooler 100 according to one embodiment will be described with reference to Figures 1 to 4. [Superconducting Magnet] A superconducting magnet 100 will be described with reference to Figure 1. The superconducting magnet 100 is an example of a device to which a cryocooler 110 is applied. The cryocooler 110 according to this embodiment is a two-stage Gifford-McMahon refrigerator.

[0020] As shown in Fig. 1, the superconducting magnet 100 includes a cryostat 101, a heat shield 102, a superconducting coil 103, a coil support 104, and an inner cylinder 105. The cryostat 101 defines a space that houses the heat shield 102. The heat shield 102 defines a space that houses the superconducting coil 103 supported by the coil support 104. The superconducting coil 103 is housed in the heat shield 102 while being supported by the coil support 104. The inner cylinder 105 penetrates the cryostat 101 and the heat shield 102 in the direction in which the inner cylinder 105 extends. The superconducting coil 103 is located outside the inner cylinder 105 in the radial direction of the inner cylinder 105.

[0021] The cryogenic refrigerator (hereinafter also referred to as refrigerator) 110 includes a cylinder 111 and a main body 112. The cylinder 111 is housed in the cryostat 101. The cylinder 111 is connected to the heat shield 102 and the coil support 104. The main body 112 is inserted into the cylinder 111. The refrigerator 110 is a two-stage refrigerator, and the cylinder 111 includes two cooling stages. The first cooling stage cools the heat shield 102. The second cooling stage cools the superconducting coil 103 supported by the coil support 104.

[0022] When maintenance of the refrigerator 110 is performed, first, the main body 112 is separated from the cylinder 111. Next, the main body 112 is removed from the cylinder 111. Next, the heating device 10 (see FIG. 2 ) of the refrigerator 110 is inserted into the cylinder 111. The heating device 10 of the cryogenic refrigerator (hereinafter also referred to as the heating device 10) of the present disclosure is used during maintenance of the refrigerator 110. By inserting the heating device 10 into the cylinder 111 and thereby raising the temperature of the cylinder 111, it is possible to suppress condensation from forming inside the cylinder 111 and remove moisture that has formed inside the cylinder 111 due to condensation before the temperature rises.

[0023] [Heating Device and Cylinder] The structures of the heating device 10 and the cylinder 111 into which the heating device 10 is inserted will be described with reference to Figures 2 to 4. Figure 2 shows the structure of the heating device 10 before it is inserted into the cylinder 111. Figure 3 shows the structure of the cylinder 111 into which the heating device 10 is inserted. Figure 4 shows the structure of the heating device 10 inserted into the cylinder 111 together with the structure of the cylinder 111.

[0024] The heating device 10 of the cryogenic refrigerator 110 shown in Figure 2 is inserted into the cylinder 111 of the cryogenic refrigerator 110. The heating device 10 includes a first heater block 11 and a first biasing member 12. The first heater block 11 is housed in the cylinder 111. The first biasing member 12 presses the first heater block 11 against a first cylinder inner bottom surface 121AB (see Figure 3) of the cylinder 111.

[0025] According to the heating device 10 of the present disclosure, the first heater block 11 is pressed against the first cylinder inner bottom surface 121AB by the first biasing member 12, so that the first heater block 11 comes into direct contact with the first cylinder inner bottom surface 121AB. This improves the efficiency of heat conduction from the first heater block 11 to the first cylinder inner bottom surface 121AB. As a result, the cylinder 111, which is the target of heating by the heating device 10, is more easily heated.

[0026] The heating device 10 further includes a first cylindrical portion 13. The first cylindrical portion 13 has an opening 13A to which the first heater block 11 is attached. The first cylindrical portion 13 is housed in a cylinder 111. The thermal conductivity of the first cylindrical portion 13 is preferably lower than that of the first heater block 11. If the thermal conductivity of the first cylindrical portion 13 is lower than that of the first heater block 11, heat conduction from the first heater block 11 to the first cylindrical portion 13 is suppressed, and as a result, the amount of heat conducted from the first heater block 11 to the first cylinder inner bottom surface 121AB is less likely to decrease. As a result, the cylinder 111 in contact with the first heater block 11 is more likely to be heated.

[0027] For example, the first heater block 11 may be made of copper or aluminum, and the first cylindrical portion 13 may be made of stainless steel. This makes the thermal conductivity of the first cylindrical portion 13 lower than the thermal conductivity of the first heater block 11 attached to the first cylindrical portion 13. In this case, heat is less likely to be transmitted from the first heater block 11 to the first cylindrical portion 13, so a rise in temperature in the first cylindrical portion 13, which is likely to be touched by an operator, is suppressed. This makes it possible to improve the ease of handling of the heating device 10.

[0028] The first cylindrical portion 13 has a top surface 13B at the cylindrical end opposite the opening 13A. The first biasing member 12 contacts the top surface 13B of the first cylindrical portion 13, thereby biasing the first cylindrical portion 13 toward the first cylinder inner bottom surface 121AB of the cylinder 111. As a result, the first heater block 11 attached to the opening 13A of the first cylindrical portion 13 is pressed against the first cylinder inner bottom surface 121AB.

[0029] The first cylindrical portion 13 includes an insertion portion 13C that extends in a direction away from the first heater block 11 in the extension direction of the first cylindrical portion 13. The first biasing member 12 is passed through the insertion portion 13C. The first cylindrical portion 13 includes a pressing portion 13D. The pressing portion 13D is passed through the insertion portion 13C. The pressing portion 13D sandwiches the first biasing member 12 between itself and the top surface 13B in the extension direction of the first cylindrical portion 13. The pressing force of the pressing portion 13D that presses the first biasing member 12 toward the top surface 13B changes depending on the position in the extension direction of the first cylindrical portion 13. The pressing force on the first biasing member 12 increases as the pressing portion 13D approaches the top surface 13B in the extension direction of the first cylindrical portion 13. Furthermore, the force with which the first biasing member 12 presses the first heater block 11 against the inner bottom surface 121AB of the first cylinder when the heating device 10 is inserted into the cylinder 111 changes depending on the position of the pressing portion 13D in the direction in which the first cylindrical portion 13 extends.

[0030] The heating device 10 may include only one first biasing member 12, or may include multiple first biasing members 12. For example, in this embodiment, the heating device 10 includes three first biasing members 12. When viewed from a viewpoint facing the top surface 13B of the first cylindrical portion 13, each first biasing member 12 biases a portion of the top surface 13B that is not in contact with other first biasing members 12.

[0031] The first heater block 11 includes a first surface (top surface in FIG. 2 ) that contacts the first cylindrical portion 13, and a second surface (bottom surface in FIG. 2 ) that is located on the opposite side and faces the first cylinder inner bottom surface 121AB in FIG. 3 . The pressing force of the first biasing member 12 is set to a magnitude that allows the second surface of the first heater block 11 to contact the first cylinder inner bottom surface 121AB. For example, the pressing force of the first biasing member 12 is set to a magnitude that can prevent a gap from occurring between the first heater block 11 and the first cylinder inner bottom surface 121AB due to dimensional tolerances of the heating device 10 in the extension direction of the first cylindrical portion 13.

[0032] The heating device 10 includes a plurality of first heaters 14. In the example shown in Fig. 2, the heating device 10 includes six first heaters 14 (two of which are shown in Fig. 2). Each first heater 14 is located inside the first cylindrical portion 13 and inserted into the first heater block 11. When an electric current is supplied to each first heater 14, the first heater 14 generates heat, thereby heating the first heater block 11.

[0033] The heating device 10 further includes a second heater block 15 and a second biasing member 16. The second heater block 15 is located on the opposite side of the first heater block 11 from the first biasing member 12, and is housed in the cylinder 111. The second biasing member 16 is located between the first heater block 11 and the second heater block 15, and presses the second heater block 15 against a second cylinder inner bottom surface 121BB (see FIG. 3 ) of the cylinder 111. Because the heating device 10 includes the second biasing member 16 that presses the second heater block 15 against the second cylinder inner bottom surface 121BB, the efficiency of heat conduction from the heating device 10 to the cylinder 111 is improved at both the first cylinder inner bottom surface 121AB and the second cylinder inner bottom surface 121BB of the cylinder 111.

[0034] The first biasing member 12, the first heater block 11, the second biasing member 16, and the second heater block 15 are arranged in the order listed in the direction of extension of the heating device 10. In the direction of extension of the heating device 10, the first heater block 11 is located on the opposite side of the second heater block 15 with respect to the second biasing member 16. In the direction of extension of the heating device 10, the first biasing member 12 is located on the opposite side of the second biasing member 16 with respect to the first heater block 11.

[0035] The heating device 10 further includes a second cylindrical portion 17. The second cylindrical portion 17 has an opening 17A to which the second heater block 15 is attached, and is housed in the cylinder 111. The thermal conductivity of the second cylindrical portion 17 is preferably lower than that of the second heater block 15. When the thermal conductivity of the second cylindrical portion 17 is lower than that of the second heater block 15, heat conduction from the second heater block 15 to the second cylindrical portion 17 is suppressed, and as a result, the amount of heat conducted from the second heater block 15 to the second cylinder inner bottom surface 121BB is less likely to decrease.

[0036] For example, the second heater block 15 may be made of copper or aluminum, and the second cylindrical portion 17 may be made of stainless steel. According to the heating device 10, the thermal conductivity of the second cylindrical portion 17 is lower than the thermal conductivity of the second heater block 15 attached to the second cylindrical portion 17.

[0037] The second cylindrical portion 17 has an inserted portion 17B at the cylindrical end opposite the opening 17A. Because the second cylindrical portion 17 has the inserted portion 17B, the cylindrical end of the second cylindrical portion 17 opposite the opening 17A is closed. The inserted portion 17B has a step portion 17BA in the radial direction of the second cylindrical portion 17, where the first end of the second biasing member 16 is disposed.

[0038] The first heater block 11 has a fitting portion 11H. The fitting portion 11H is a hole that opens to the second surface (bottom surface in FIG. 2 ) of the first heater block 11. The fitting portion 11H has a bottom midway in the thickness direction of the first heater block 11 from the second surface to the first surface (top surface in FIG. 2 ) of the first heater block 11. The fitting portion 11H has a groove portion 11HA in which the second end of the second biasing member 16 is disposed. The inserted portion 17B of the second cylindrical portion 17 is fitted into the fitting portion 11H with the second biasing member 16 attached.

[0039] The inserted portion 17B is recessed in the radial direction of the second cylindrical portion 17 and has an elongated hole 17BG extending along the axial direction of the second cylindrical portion 17. The first heater block 11 is provided with a fixing pin 11P extending along the radial direction of the first cylindrical portion 13. An end of the fixing pin 11P located closer to the central axis of the first cylindrical portion 13 in the radial direction of the first cylindrical portion 13 protrudes into the fitting portion 11H of the first heater block 11. The fixing pin 11P and the elongated hole 17BG are configured so that the second cylindrical portion 17 can be fixed to the first heater block 11 by the fixing pin 11P at any position of the elongated hole 17BG along the axial direction of the second cylindrical portion 17.

[0040] As a result, the heating device 10 is configured to be able to change the position of the second cylindrical body relative to the first cylindrical body in the axial direction of the first cylindrical body. In the heating device 10, the first heater block 11 and the first cylindrical portion 13 are included in the first cylindrical body, and the second heater block 15 and the second cylindrical portion 17 are included in the second cylindrical body.

[0041] Due to differences in processing accuracy and differences in thermal contraction due to temperature distribution, the distance between the first cylinder inner bottom surface 121AB (see FIG. 3) and the second cylinder inner bottom surface 121BB (see FIG. 3) may differ from the distance between the bottom surface of the first heater block 11 and the bottom surface of the second heater block 15. The bottom surface of the first heater block 11 is the surface of the first heater block 11 that is pressed against the first cylinder inner bottom surface 121AB. The bottom surface of the second heater block 15 is the surface of the second heater block 15 that is pressed against the second cylinder inner bottom surface 121BB.

[0042] Even in this case, by adjusting the position of the second cylindrical body relative to the first cylindrical body in the axial direction of the first cylindrical body, it is possible to simultaneously press the first heater block 11 against the inner bottom surface 121AB of the first cylinder and press the second heater block 15 against the inner bottom surface 121BB of the second cylinder.

[0043] The pressing force of the second biasing member 16 is set to a magnitude that allows the surface of the second heater block 15 opposite the surface that contacts the second cylindrical portion 17 to contact the second cylinder inner bottom surface 121BB. For example, the pressing force of the second biasing member 16 is set to a magnitude that can prevent a gap from being generated between the second heater block 15 and the second cylinder inner bottom surface 121BB due to a difference in thermal contraction caused by the dimensional tolerance and temperature distribution of the heating device 10 in the extension direction of the second cylindrical portion 17.

[0044] The heating device 10 includes a plurality of second heaters 18. In the example shown in Fig. 2, the heating device 10 includes two second heaters 18 (one of which is shown in Fig. 2). The second heaters 18 are located inside the second cylindrical portion 17 and inserted into the second heater block 15. When an electric current is supplied to the second heaters 18, the second heaters 18 generate heat, thereby heating the second heater block 15.

[0045] The heating device 10 further includes a flange portion 10F, a gas supply pipe 10G1, a gas exhaust pipe 10G2, and a wiring portion 10W. The inserted portion 13C of the first cylindrical portion 13 is supported on the flange portion 10F.

[0046] The gas supply pipe 10G1 extends in the same direction as the first cylindrical portion 13. The gas supply pipe 10G1 has a length that extends from the flange portion 10F to the tip of the second cylindrical portion 17. A cylinder of helium gas, for example, is connected to the gas supply pipe 10G1. The gas exhaust pipe 10G2 is inserted into a through-hole in the flange portion 10F. The gas exhaust pipe 10G2 extends from the flange portion 10F toward the opposite side from the second heater block 15. The gas exhaust pipe 10G2 exhausts the gas supplied from the gas supply pipe 10G1 into the cylinder 111 to the outside of the cylinder 111.

[0047] The wiring portion 10W is supported by the flange portion 10F. The wiring portion 10W includes wiring connected to the first heater 14 and wiring connected to the second heater 18. As shown in FIG. 3, the cylinder 111 includes a main body portion 121, a first cooling stage 122, and a second cooling stage 123. The main body portion 121 includes a first cylinder portion 121A and a second cylinder portion 121B. The first cylinder portion 121A and the second cylinder portion 121B are aligned along the extension direction of the main body portion 121, and the second cylinder portion 121B is connected to the first cylinder portion 121A. The diameter of the second cylinder portion 121B is smaller than the diameter of the first cylinder portion 121A. The first cylinder portion 121A has a flange portion 121F at the first cylinder end and a first cylinder inner bottom surface 121AB at the second cylinder end. The first cylinder inner bottom surface 121AB has a closed ring shape. In the second cylinder portion 121B, a first cylinder end is connected to the first cylinder portion 121A, and a second cylinder end has a second cylinder inner bottom surface 121BB.

[0048] The first cooling stage 122 is attached to the second cylinder end of the first cylinder portion 121A. The thermal conductivity of the first cooling stage 122 may be higher than the thermal conductivity of the main body portion 121. When the cylinder 111 is mounted on the superconducting magnet 100, the first cooling stage 122 is in contact with the heat shield 102 of the superconducting magnet 100.

[0049] The second cooling stage 123 is attached to the second cylinder end of the second cylinder portion 121B. The thermal conductivity of the second cooling stage 123 may be higher than the thermal conductivity of the main body portion 121. When the cylinder 111 is mounted on the superconducting magnet 100, the second cooling stage 123 is in contact with the coil support portion 104 of the superconducting magnet 100.

[0050] 4, the heating device 10 is inserted into the cylinder 111, and the heating device 10 is attached to the cylinder 111 so that the flange portion 10F of the heating device 10 contacts the flange portion 121F of the cylinder 111. At this time, the bottom surface of the second heater block 15 opposite the surface that contacts the second cylindrical portion 17 contacts the second cylinder inner bottom surface 121BB. As a result, the force of the second biasing member 16 pressing the second heater block 15 against the second cylinder inner bottom surface 121BB acts on the second heater block 15.

[0051] Furthermore, since the flange portion 10F of the heating device 10 contacts the flange portion 121F of the cylinder 111 and the bottom surface of the first heater block 11 contacts the inner bottom surface 121AB of the first cylinder, a force is applied to the first heater block 11 by the first biasing member 12 pressing the first heater block 11 against the inner bottom surface 121AB of the first cylinder.

[0052] As described above, the heating device 10 of the cryogenic refrigerator 110 according to one embodiment can achieve the following effects: (1) The first heater block 11 is pressed against the first cylinder inner bottom surface 121AB by the first biasing member 12, so the first heater block 11 comes into direct contact with the first cylinder inner bottom surface 121AB. This improves the efficiency of heat conduction from the first heater block 11 to the first cylinder inner bottom surface 121AB.

[0053] (2) If the thermal conductivity of the first cylindrical portion 13 is lower than that of the first heater block 11, heat conduction from the first heater block 11 to the first cylindrical portion 13 is suppressed, thereby making it difficult for the amount of heat conducted from the first heater block 11 to the first cylinder inner bottom surface 121AB to decrease.

[0054] (3) The heating device 10 includes the second biasing member 16 that presses the second heater block 15 against the second cylinder inner bottom surface 121BB. This increases the efficiency of heat conduction from the heating device 10 to the cylinder 111 at both the first cylinder inner bottom surface 121AB and the second cylinder inner bottom surface 121BB of the cylinder 111.

[0055] (4) When the thermal conductivity of the second cylindrical portion 17 is lower than that of the second heater block 15, heat conduction from the second heater block 15 to the second cylindrical portion 17 is suppressed, and as a result, the amount of heat conducted from the second heater block 15 to the second cylinder inner bottom surface 121BB is less likely to decrease. (5) By adjusting the position of the second cylindrical body relative to the first cylindrical body, it is possible to simultaneously press the first heater block 11 against the first cylinder inner bottom surface 121AB and press the second heater block 15 against the second cylinder inner bottom surface 121BB.

[0056] (6) When each heater block 11, 15 is formed from copper or aluminum and each cylindrical portion 13, 17 is formed from stainless steel, the thermal conductivity of each cylindrical portion 13, 17 is lower than the thermal conductivity of the heater block 11, 15 attached to that cylindrical portion 13, 17.

[0057] The above-described embodiment can be modified as follows: [Thermal Conductivity] The thermal conductivity of each heater block 11, 15 may be equal to or lower than the thermal conductivity of the cylindrical portion 13, 17 to which the heater block 11, 15 is attached. Even in this case, the heater blocks 11, 15 are pressed against the inner bottom surfaces 121AB, 121BB of the cylinder, thereby achieving the effects equivalent to (1) and (3).

[0058] The first heater block 11 and the second heater block 15 may be made of a metal other than copper or aluminum. The first cylindrical portion 13 and the second cylindrical portion 17 may be made of a metal other than stainless steel. It is sufficient that the thermal conductivity of the metal constituting the first cylindrical portion 13 and the second cylindrical portion 17 is sufficiently smaller than the thermal conductivity of the metal constituting the first heater block 11 and the second heater block 15.

[0059] [Cryogenic Refrigerator] The cryogenic refrigerator included in the superconducting magnet 100 may be a single-stage type. In this case, since the cylinder 111 includes only one cylindrical portion, the heating device 10 applied to the cylinder 111 may also include only one heater block and one biasing member. Therefore, if the cryogenic refrigerator is a single-stage type, the second heater block 15, the second biasing member 16, and the second cylindrical portion 17 may be omitted from the heating device 10. Alternatively, if the cryogenic refrigerator is a single-stage type, the first heater block 11, the first biasing member 12, and the first cylindrical portion 13 may be omitted from the heating device 10. In this case, for example, the flange portion 10F of the heating device 10 may have a structure corresponding to the fitting portion 11H included in the first heater block 11.

[0060] REFERENCE SIGNS LIST 10: Heating device 11: First heater block 12: First biasing member 13: First cylindrical portion 15: Second heater block 16: Second biasing member 17: Second cylindrical portion

Claims

1. A heating device for a cryogenic refrigerator that is inserted into a cylinder of the cryogenic refrigerator, comprising: a heater block housed in the cylinder; and a biasing member that presses the heater block against an inner bottom surface of the cylinder.

2. The heating device of claim 1, further comprising a cylindrical portion having an opening to which the heater block is attached and housed in the cylinder, the thermal conductivity of the cylindrical portion being lower than the thermal conductivity of the heater block.

3. The heating device for a cryogenic refrigerator according to claim 2, wherein the heater block is made of copper or aluminum, and the cylindrical portion is made of stainless steel.

4. A heating device for a cryogenic refrigerator described in any one of claims 1 to 3, further comprising: a second heater block located on the opposite side of the first heater block to the first biasing member and housed in the cylinder; and a second biasing member located between the first heater block and the second heater block and pressing the second heater block against the second cylinder inner bottom surface of the cylinder.

5. The heating device of claim 2, further comprising: a second heater block located on the opposite side of the first heater block from the first biasing member and housed in the cylinder; a second biasing member located between the first heater block and the second heater block and pressing the second heater block against the second cylinder inner bottom surface of the cylinder; and a second cylindrical portion having an opening to which the second heater block is attached and housed in the cylinder, wherein the thermal conductivity of the second cylindrical portion is lower than the thermal conductivity of the second heater block.

6. A heating device for a cryogenic refrigerator as described in claim 5, wherein the first heater block and the first cylindrical portion are included in a first cylindrical body, the second heater block and the second cylindrical portion are included in a second cylindrical body, and the position of the second cylindrical body relative to the first cylindrical body can be changed in the axial direction of the first cylindrical body.

7. The heating device for a cryogenic refrigerator according to claim 5, wherein the second heater block is made of copper or aluminum, and the second cylindrical portion is made of stainless steel.

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