Cryopump

Abstract

To improve the practicality of the safety purge function of cryopumps. [Solution] The cryopump 10 includes a purge valve comprising a main valve 60 that is closed when fluid is supplied from a fluid source to shut off the purge gas and opened when fluid is discharged to supply the purge gas, and a pilot valve 70 that switches between a first state in which fluid is supplied from the fluid source to the main valve 60 and a second state in which fluid is discharged from the main valve 60. The purge valve is configured to limit the discharge of fluid from the main valve 60 when the fluid supply from the fluid source is lost in the first state of the pilot valve 70.

Description

Technical Field

[0001] The present invention relates to a cryopump.

Background Art

[0002] A cryopump is a vacuum pump that captures gas molecules by condensation or adsorption on a cryopanel cooled to an extremely low temperature and evacuates them. Typically, a cryopump can be used to achieve a clean vacuum environment required in a semiconductor circuit manufacturing process. In a semiconductor manufacturing process, hazardous gases with various hazards such as explosiveness, corrosiveness, and toxicity may be used. When an unintended temperature rise occurs in the cryopump due to some abnormal situation such as a power outage, the hazardous gas stored in the cryopump is vaporized again, and the concentration of the hazardous gas can increase inside the cryopump. In order to eliminate such an unsafe state, it has been proposed to perform a so-called safety purge to automatically purge the hazardous gas from the cryopump using a normally open purge valve that naturally returns to the open state during a power loss.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] One exemplary object of an aspect of the present invention is to improve the practicality of the safety purge function of a cryopump.

Means for Solving the Problems

[0005] According to one aspect of the present invention, the cryopump includes a purge valve comprising a main valve that is closed when fluid is supplied from a fluid source to shut off the purge gas and is opened when fluid is discharged to supply the purge gas, and a pilot valve that switches between a first state in which fluid is supplied from the fluid source to the main valve and a second state in which fluid is discharged from the main valve. The purge valve is configured to limit the discharge of fluid from the main valve when the fluid supply from the fluid source is lost in the first state of the pilot valve.

[0006] According to one aspect of the present invention, the cryopump includes a purge valve comprising: a main valve that is closed when fluid is supplied from a fluid source to shut off the purge gas and opened when fluid is discharged to supply the purge gas; a pilot valve that switches between a first state in which fluid is supplied from the fluid source to the main valve and a second state in which fluid is discharged from the main valve; and a backup power supply connected to the pilot valve. The pilot valve includes a solenoid valve that returns from the first state to the second state when the supply voltage drops below the recovery voltage. The backup power supply includes an energy storage element and a boost circuit that increases the output voltage of the energy storage element to exceed the recovery voltage of the solenoid valve to generate a supply voltage to the solenoid valve.

[0007] According to one aspect of the present invention, the cryopump includes a purge valve comprising: a main valve that is closed by the supply of fluid from a fluid source to shut off the purge gas and opened by the discharge of fluid to supply the purge gas; a pilot valve that switches between a first state in which fluid is supplied from the fluid source to the main valve and a second state in which fluid is discharged from the main valve; and a backup power supply connected to the pilot valve. The backup power supply comprises an energy storage element and an energy storage element monitor that monitors the energy storage element by discharging the energy storage element.

[0008] Furthermore, any combination of the above components, or any substitution of components or expressions of the present invention between methods, apparatus, systems, etc., is also valid as an embodiment of the present invention. [Effects of the Invention]

[0009] According to the present invention, the practicality of the safety purging function of a cryopump can be improved. [Brief explanation of the drawing]

[0010] [Figure 1] A schematic diagram of a cryopump system according to an embodiment is shown. [Figure 2] A schematic diagram of a cryopump system according to an embodiment is shown. [Figure 3] This figure schematically shows an exemplary configuration of a purge valve for a cryopump in accordance with an embodiment. [Figure 4] This figure schematically shows an exemplary configuration of a purge valve for a cryopump in accordance with an embodiment. [Figure 5] This figure schematically shows an exemplary configuration of a purge valve for a cryopump in accordance with an embodiment. [Figure 6] This figure schematically shows an exemplary configuration of a purge valve for a cryopump in accordance with an embodiment. [Figure 7] This diagram schematically shows the power supply system of the purge valve of a cryopump according to an embodiment. [Modes for carrying out the invention]

[0011] The embodiments for carrying out the present invention will be described in detail below with reference to the drawings. In the description and drawings, identical or equivalent components, members, and processes are denoted by the same reference numerals, and redundant descriptions will be omitted as appropriate. The scale and shape of the illustrated parts are set for convenience to facilitate the explanation and are not to be interpreted restrictively unless otherwise specified. The embodiments are illustrative and do not limit the scope of the present invention in any way. Not all features or combinations thereof described in the embodiments are necessarily essential to the invention.

[0012] Figures 1 and 2 schematically illustrate a cryopump system according to an embodiment. Figure 1 schematically shows the external appearance of the cryopump 10, and Figure 2 schematically shows the internal structure of the cryopump 10. The cryopump 10 is used to raise the vacuum level inside the vacuum chamber 100 to the level required for a desired vacuum process, for example, by being installed in a vacuum chamber 100 of an ion implantation apparatus, sputtering apparatus, deposition apparatus, or other vacuum process apparatus. -5 Pa~10 -8 A high vacuum level of approximately Pa is achieved in the vacuum chamber 100.

[0013] The cryopump 10 comprises a compressor 12, a refrigerator 14, and a cryopump vessel 16. The cryopump vessel 16 has a cryopump intake port 17. The cryopump 10 also includes a rough valve 18, a body purge valve 20, a discharge valve 22, and a discharge purge valve 24, which are installed in the cryopump vessel 16.

[0014] The compressor 12 is configured to recover refrigerant gas from the chiller 14, pressurize the recovered refrigerant gas, and supply it back to the chiller 14. The chiller 14, also called the expander or cold head, together with the compressor 12 constitutes a cryogenic chiller. The circulation of refrigerant gas between the compressor 12 and the chiller 14 occurs with a combination of appropriate pressure and volume fluctuations of the refrigerant gas within the chiller 14, thereby creating a thermodynamic cycle that generates cold, and the chiller 14 can provide cryogenic cooling. The refrigerant gas is usually helium, but other suitable gases may be used. For understanding, the direction of refrigerant gas flow is indicated by arrows in Figure 1. The cryogenic chiller is, as an example, a two-stage Gifford-McMahon (GM) chiller, but may be a pulse tube chiller, a Stirling chiller, or other type of cryogenic chiller.

[0015] As shown in FIG. 2, the refrigerator 14 includes a room temperature section 26, a first cylinder 28, a first cooling stage 30, a second cylinder 32, and a second cooling stage 34. The refrigerator 14 is configured to cool the first cooling stage 30 to a first cooling temperature and the second cooling stage 34 to a second cooling temperature. The second cooling temperature is lower than the first cooling temperature. For example, the first cooling stage 30 is cooled to about 65K to 120K, preferably 80K to 100K, and the second cooling stage 34 is cooled to about 10K to 20K. The first cooling stage 30 and the second cooling stage 34 can also be referred to as a high-temperature cooling stage and a low-temperature cooling stage, respectively. By cooling the first cooling stage 30 and the second cooling stage 34 to their respective target cooling temperatures in this way, the cryopump 10 can perform a vacuum evacuation operation.

[0016] The first cylinder 28 connects the first cooling stage 30 to the room temperature section 26, whereby the first cooling stage 30 is structurally supported by the room temperature section 26. The second cylinder 32 connects the second cooling stage 34 to the first cooling stage 30, whereby the second cooling stage 34 is structurally supported by the first cooling stage 30. The first cylinder 28 and the second cylinder 32 extend coaxially, and the room temperature section 26, the first cylinder 28, the first cooling stage 30, the second cylinder 32, and the second cooling stage 34 are arranged linearly in this order in a row.

[0017] When the refrigerator 14 is a two-stage GM refrigerator, a first displacer and a second displacer (not shown) are reciprocally arranged inside the first cylinder 28 and the second cylinder 32, respectively. A first regenerator and a second regenerator (not shown) are incorporated in the first displacer and the second displacer, respectively. The room temperature section 26 has a drive mechanism 26a such as a motor for reciprocating the first displacer and the second displacer. The drive mechanism 26a may include a flow path switching mechanism that switches the flow path of the working gas (e.g., helium) to periodically repeat the supply and discharge of the working gas into the refrigerator 14.

[0018] The cryopump 10 also includes a radiation shield 36 and a cryopanel 38. The radiation shield 36 is thermally coupled to the first cooling stage 30 and cooled to the first cooling temperature to provide a cryogenic surface for protecting the cryopanel 38 from radiant heat from outside the cryopump 10 or from the cryopump container 16.

[0019] The radiation shield 36 has, for example, a cylindrical shape and is arranged to surround the cryopanel 38 and the second cooling stage 34. The end of the radiation shield 36 on the side of the cryopump inlet 17 is open, and can receive gas entering from outside the cryopump 10 through the cryopump inlet 17 into the radiation shield 36. The end of the radiation shield 36 on the side opposite to the cryopump inlet 17 may be closed, or may have an opening, or may be open. The radiation shield 36 has a gap between it and the cryopanel 38, and the radiation shield 36 is not in contact with the cryopanel 38. The radiation shield 36 is also not in contact with the cryopump container 16.

[0020] An inlet baffle 37 may be provided at the cryopump inlet 17 or between the cryopump inlet 17 and the cryopanel 38 to protect the cryopanel 38 from radiant heat from a heat source outside the cryopump 10 (for example, a heat source in the vacuum chamber 100 to which the cryopump 10 is attached). The inlet baffle 37 may be fixed to the open end of the radiation shield 36 and thermally coupled to the first cooling stage 30 of the refrigerator 14 through the radiation shield 36. Alternatively, the inlet baffle 37 may be attached to the first cooling stage 30. The inlet baffle 37 is cooled to the same temperature as the radiation shield 36 and can condense a so-called type 1 gas (a gas that condenses at a relatively high temperature, such as water vapor) on its surface.

[0021] The cryopanel 38 is thermally coupled to the second cooling stage 34 and cooled to a second cooling temperature in order to provide a cryogenic surface for condensing type 2 gases (e.g., gases that condense at relatively low temperatures, such as argon and nitrogen). In addition, at least a portion of the surface of the cryopanel 38 (e.g., the surface opposite the cryopump intake port 17) is fitted with, for example, activated carbon or other adsorbent material to adsorb type 3 gases (e.g., non-condensable gases, such as hydrogen). Gases entering the radiant shield 36 from outside the cryopump 10 through the cryopump intake port 17 are captured by condensation or adsorption on the cryopanel 38. The arrangement and shape of the radiant shield 36 and the cryopanel 38 can take various known configurations as appropriate, so they will not be described in detail here.

[0022] The cryopump vessel 16 has a vessel body 16a and a refrigerator housing cylinder 16b. The cryopump vessel 16 is a vacuum vessel designed to maintain a vacuum during the vacuum evacuation operation of the cryopump 10 and to withstand the pressure of the surrounding environment (e.g., atmospheric pressure). The vessel body 16a has a cylindrical shape with a cryopump intake port 17 at one end and the other end closed. The vessel body 16a houses a radiation shield 36, and as described above, the cryopanel 38 is housed inside the radiation shield 36 together with the second cooling stage 34. The refrigerator housing cylinder 16b is connected at one end to the vessel body 16a and fixed at the other end to the room temperature section 26 of the refrigerator 14. The refrigerator 14 is inserted into the refrigerator housing cylinder 16b and houses the first cylinder 28.

[0023] In this embodiment, the cryopump 10 is a so-called horizontal cryopump in which the refrigerator 14 is located on the side of the container body 16a. A refrigerator inlet is provided on the side of the container body 16a, and the refrigerator housing cylinder 16b is coupled to the side of the container body 16a at this refrigerator inlet. Similarly, adjacent to the refrigerator inlet of the container body 16a, a hole for passing the refrigerator 14 is also provided on the side of the radiation shield 36. The second cylinder 32 and the second cooling stage 34 of the refrigerator 14 are inserted into the radiation shield 36 through these holes, and the radiation shield 36 is thermally coupled to the first cooling stage 30 around the holes on its side.

[0024] The cryopump 10 can be installed in the vacuum chamber 100 in various orientations at the site of use. For example, the cryopump 10 can be installed in the lateral orientation shown in the figure, i.e., with the cryopump intake port 17 facing upward. In this case, the bottom of the container body 16a is located below the cryopump intake port 17, and the refrigerator 14 extends horizontally.

[0025] The cryopump 10 includes a first temperature sensor 40 for measuring the temperature of the first cooling stage 30 and a second temperature sensor 42 for measuring the temperature of the second cooling stage 34. The first temperature sensor 40 may be attached to the first cooling stage 30. The second temperature sensor 42 may be attached to the second cooling stage 34. The temperature of the first cooling stage 30 measured by the first temperature sensor 40 can be considered as the temperature of the radiation shield 36, and the temperature of the second cooling stage 34 measured by the second temperature sensor 42 can be considered as the temperature of the cryopanel 38. Therefore, the first temperature sensor 40 can measure the temperature of the radiation shield 36 and output a first measured temperature signal indicating the measured temperature of the radiation shield 36. The second temperature sensor 42 can measure the temperature of the cryopanel 38 and output a second measured temperature signal indicating the measured temperature of the cryopanel 38. In addition, a pressure sensor 44 is provided inside the cryopump container 16. The pressure sensor 44 is installed, for example, in the refrigerator housing cylinder 16b, and can measure the internal pressure of the cryopump container 16 and output a measured pressure signal indicating the measured pressure.

[0026] Furthermore, the cryopump 10 includes a cryopump controller 46 that controls the cryopump 10. The cryopump controller 46 may be integrated with the cryopump 10. For example, the cryopump controller 46 may be attached to the room temperature section 26. Alternatively, the cryopump controller 46 may be configured as a separate control device from the cryopump 10. Alternatively, a part of the cryopump controller 46 may be integrated with the cryopump 10, and another part of the cryopump controller 46 may be provided separately from the cryopump 10, and they may be electrically connected to each other.

[0027] The cryopump controller 46 may control the refrigerator 14 based on the cooling temperature of the radiant shield 36 and / or cryopanel 38 during vacuum evacuation operation of the cryopump 10. The cryopump controller 46 may be connected to the first temperature sensor 40 to receive a first measured temperature signal from the first temperature sensor 40 and to the second temperature sensor 42 to receive a second measured temperature signal from the second temperature sensor 42.

[0028] Furthermore, the cryopump controller 46 can operate as a regeneration controller for the cryopump 10. During the regeneration operation of the cryopump 10, the cryopump controller 46 may control the chiller 14, rough valve 18, body purge valve 20, discharge valve 22, and discharge purge valve 24 based on the pressure in the cryopump vessel 16 (or, if necessary, based on the temperature of the cryopanel 38 and the pressure in the cryopump vessel 16). The cryopump controller 46 may be connected to the pressure sensor 44 to receive the measured pressure signal from the pressure sensor 44.

[0029] The internal configuration of the controller is realized in hardware form by components and circuits such as the CPU and memory of a computer, and in software form by computer programs, etc., but in the diagram, it is depicted as functional blocks realized through the coordination of these components as appropriate. It will be understood by those skilled in the art that these functional blocks can be realized in various ways through combinations of hardware and software.

[0030] For example, a controller can be implemented as a combination of a processor (hardware) such as a CPU (Central Processing Unit) or microcontroller, and a software program executed by the processor (hardware). The software program may be a computer program that causes the controller to perform vacuum evacuation and / or regeneration operations of the cryopump 10.

[0031] The rough valve 18 is installed in the cryopump container 16, for example, the refrigerator housing cylinder 16b. The rough valve 18 is connected to a rough pump (not shown) installed outside the cryopump 10. The rough pump is a vacuum pump used to evacuate the cryopump 10 to its operating pressure. When the rough valve 18 is opened under the control of the cryopump controller 46, the cryopump container 16 is connected to the rough pump, and when the rough valve 18 is closed, the cryopump container 16 is disconnected from the rough pump. By opening the rough valve 18 and operating the rough pump, the cryopump 10 can be depressurized.

[0032] The body purge valve 20 enables "body purging," which involves supplying purge gas to the container body 16a of the cryopump container 16. In an exemplary configuration, the body purge valve 20 is installed in the cryopump container 16, for example, in the container body 16a. The body purge valve 20 is also connected to a purge gas source 48 or purge gas supply device installed outside the cryopump 10.

[0033] When the body purge valve 20 is opened under the control of the cryopump controller 46, purge gas is supplied from the purge gas source 48 to the cryopump vessel 16, and when the body purge valve 20 is closed, the supply of purge gas to the cryopump vessel 16 is cut off. By opening the body purge valve 20 and introducing purge gas into the cryopump vessel 16, the cryopump 10 can be pressurized. In addition, the cryopump 10 can be heated from cryogenic temperatures to room temperature or higher. Alternatively, as described later, by adjusting the flow rate of purge gas with the body purge valve 20, the pressure and temperature inside the cryopump 10 can be maintained, or a significant increase can be suppressed, while supplying purge gas to the cryopump 10.

[0034] The purge gas may be, for example, nitrogen gas or other dry gas, and the temperature of the purge gas may be adjusted to, for example, room temperature (above 0°C, for example 15°C to 30°C), or heated to a temperature higher than room temperature (for example 50°C or below or 80°C or below). Alternatively, the temperature of the purge gas may be cooled to a temperature lower than room temperature (for example, below 0°C). Cooling the purge gas may be preferable in suppressing the temperature rise of the cryopanel 38 when the purge gas is supplied to the cryopump vessel 16 during the cooling operation of the refrigerator 14, as described later.

[0035] In this embodiment, as will be described later with reference to Figures 3 and 4, the body purge valve 20 may include a main valve 60 and a pilot valve 70.

[0036] The discharge valve 22 is installed in the cryopump container 16, for example, in the chiller housing cylinder 16b. The discharge valve 22 is provided as the outlet of the cryopump container 16 to discharge fluid from the inside of the cryopump 10 to the outside. The discharge valve 22 is also the inlet to the discharge line 50, which will be described later. When the discharge valve 22 is opened by the control of the cryopump controller 46, fluid is discharged from the cryopump container 16, and when the discharge valve 22 is closed, the discharge of fluid from the cryopump container 16 is shut off. The fluid discharged from the discharge valve 22 is basically a gas, but it may be a liquid or a mixture of gas and liquid. The discharge valve 22 may be, for example, a normally closed control valve.

[0037] In addition, the discharge valve 22 may function as a vent valve or safety valve and may be configured to open mechanically when a predetermined differential pressure is applied. In that case, if the inside of the cryopump becomes high pressure for any reason, the discharge valve 22 will open mechanically without requiring any control. This will allow the high pressure inside to be released into the discharge line 50.

[0038] The discharge purge valve 24 enables "discharge purging," which supplies purge gas to the discharge line 50. In an exemplary configuration, the discharge valve 22 and the discharge purge valve 24 may be provided separately, with the discharge purge valve 24 connected by piping downstream of the discharge valve 22. Alternatively, the discharge purge valve 24 may be provided integrally with the discharge valve 22 to supply purge gas to the discharge valve 22 or downstream of it. The discharge purge valve 24 may be installed in the cryopump vessel 16, for example, the chiller housing cylinder 16b. The discharge purge valve 24 is connected to the purge gas source 48 or another purge gas source.

[0039] When the discharge purge valve 24 is opened by the control of the cryopump controller 46, purge gas is supplied from the purge gas source 48 to the discharge line 50, and when the discharge purge valve 24 is closed, the supply of purge gas to the discharge line 50 is cut off. The purge gas supplied from the discharge purge valve 24 is usually the same type of gas as the purge gas supplied from the body purge valve 20 (for example, nitrogen gas), but a suitable different type of gas may be used.

[0040] The discharge line 50 is provided to discharge the discharge fluid from the cryopump 10 to the treatment device 52, and is connected to the discharge valve 22 and the discharge purge valve 24 at its upstream end and to the treatment device 52 at its downstream end.

[0041] The treatment device 52 may be, for example, a pollution control device that treats hazardous gases contained in the discharge fluid (e.g., hydrogen gas, or other explosive gases, or other corrosive or toxic gases such as fluorine-based gases or halogen-based gases) to produce harmless gases, or it may be a treatment device that treats hazardous gases to reduce their hazard. Known pollution control devices or treatment devices can be appropriately adopted as such a treatment device 52, so their details will not be described here.

[0042] As the vacuum evacuation operation of the cryopump 10 continues, gas accumulates in the cryopump 10. To discharge the accumulated gas to the outside, the cryopump 10 is regenerated. The regeneration of the cryopump 10 generally includes a heating process, a discharge process, and a cool-down process.

[0043] A gate valve 102 is installed between the cryopump 10 and the vacuum chamber 100 that is evacuated. When regeneration of the cryopump 10 is started, the gate valve 102 is closed, and the cryopump 10 is isolated from the vacuum chamber 100 (the internal volume of the cryopump 10 is isolated from the vacuum chamber 100).

[0044] The heating step includes heating the cryopump 10 to the boiling point of the hazardous gases among the gases captured in the cryopump 10, or a temperature above that, and further heating the cryopump 10 to the regeneration temperature. The hazardous gases are typically, for example, type 2 or type 3 gases, and their boiling points are, for example, below 100K. The regeneration temperature is, for example, room temperature or higher. Therefore, in many cases, the hazardous gases revaporize in the first half of the heating step, especially immediately after the start, and are discharged from the cryopump 10 and flow into the treatment device 52. The hazardous gases are removed from the cryopump 10 in the heating step.

[0045] The heat source for raising the temperature is, for example, the refrigerator 14. The refrigerator 14 enables heating operation (so-called reverse heating). That is, the refrigerator 14 is configured such that adiabatic compression occurs in the working gas when the drive mechanism 26a operates in the opposite direction to the cooling operation (i.e., the motor driving the refrigerator 14 rotates in reverse). The heat of compression thus obtained allows the refrigerator 14 to heat the first cooling stage 30 and the second cooling stage 34. The radiant shield 36 and the cryopanel 38 are heated using the first cooling stage 30 and the second cooling stage 34 as heat sources, respectively. In addition, the purge gas supplied into the cryopump vessel 16 from the body purge valve 20 can also contribute to raising the temperature of the cryopump 10. Alternatively, the cryopump 10 may be provided with a heating device such as an electric heater. For example, an electric heater that can be controlled independently of the operation of the refrigerator 14 may be attached to the first cooling stage 30 and / or the second cooling stage 34 of the refrigerator 14.

[0046] In the discharge process, the gas captured by the cryopump 10 is re-vaporized or liquefied and discharged as gas, liquid, or a mixture of gas and liquid through the discharge line 50 or through the rough valve 18. Since type 2 and type 3 gases can already be easily discharged from the cryopump 10 in the heating process, the discharge process is mainly for discharging type 1 gas. Once the discharge process is complete, the cool-down process begins. In the cool-down process, the cryopump 10 is re-cooled to an extremely low temperature for vacuum evacuation operation. Once regeneration is complete, the gate valve 102 is opened again, and the cryopump 10 can start vacuum evacuation operation again.

[0047] In semiconductor manufacturing processes, hazardous gases with various risks, such as explosiveness, corrosiveness, and toxicity, are sometimes used. If an unintended temperature rise occurs in the cryopump 10 for any reason, the hazardous gases accumulated in the cryopump 10 may re-vaporize, and the concentration of hazardous gases within the cryopump 10 may increase.

[0048] Such unsafe conditions can occur, for example, due to a power outage or some other abnormality. The cryopump 10 can perform operations such as vacuum evacuation and regeneration under the control of the cryopump controller 46 by being powered from a main power source (not shown), such as a commercial power supply. However, if the main power supply fails, the operation of the cryopump 10 may stop. In the event of a power outage, especially if it takes time to restore power, the cryopump 10 may be heated up by heat input from the surrounding environment.

[0049] To eliminate the unsafe condition, a so-called safety purge may be performed, which involves automatically purging the cryopump 10. In a safety purge, the body purge valve 20 is opened, and purge gas is supplied from the purge gas source 48 to the cryopump container 16 through the body purge valve 20. Gases that have vaporized in the cryopump container 16, such as hazardous gases, are discharged along with the purge gas to the discharge line 50 through the discharge valve 22. In this way, the concentration of hazardous gases in the cryopump 10 can be reduced to a safe level.

[0050] One of the main applications of the cryopump 10 is vacuum evacuation of ion implantation equipment. In this case, hydrogen gas is mainly stored in the cryopump 10. By performing a safety purge during a power outage, even if the hydrogen gas re-vaporizes inside the cryopump 10, it can be discharged from the cryopump 10 along with the purge gas. In this way, the hydrogen gas concentration inside the cryopump 10 can be reduced to a safe level, for example, below the explosive limit of hydrogen gas (approximately 4%).

[0051] The body purge valve 20 may be a normally open valve. This allows the body purge valve 20 to return to its normal open state when power to the body purge valve 20 is lost. In this way, the body purge valve 20 can be automatically opened in the event of a power outage, ensuring that a safe purge is performed.

[0052] During safety purging, the discharge purge valve 24 may be opened and purge gas may be supplied to the discharge line 50. This may purge the discharge line 50 and quickly reduce the concentration of hazardous gas in the discharge line 50 to a safe level. To ensure this is done reliably, the discharge purge valve 24 may be a normally open valve.

[0053] If the cryopump controller 46 is operational, the body purge valve 20 may be opened under the control of the cryopump controller 46, and a safety purge may be performed. In this case, the discharge purge valve 24 may also be opened by the cryopump controller 46.

[0054] Figures 3 and 4 are schematic diagrams illustrating an exemplary configuration of the purge valve of the cryopump 10 according to an embodiment. As shown in the figures, the body purge valve 20 comprises a main valve 60 and a pilot valve 70. The body purge valve 20 may also be equipped with a check valve 75, as will be described later.

[0055] The main valve 60 is configured to close when fluid is supplied from the fluid source 54, thereby shutting off the purge gas, and to open when the fluid is discharged, thereby supplying the purge gas. The pilot valve 70 is configured to switch between a first state in which fluid is supplied from the fluid source 54 to the main valve 60 and a second state in which fluid is discharged from the main valve 60. The first state is shown in Figure 3, and the second state is shown in Figure 4.

[0056] Therefore, the main valve 60 is closed when the pilot valve 70 is in the first state, cutting off the supply of purge gas to the cryopump container 16. On the other hand, the main valve 60 is opened when the pilot valve 70 is in the second state, supplying purge gas to the cryopump container 16. The purge gas flow is schematically shown in Figure 4 by arrow 76.

[0057] The main valve 60 may be a so-called air-operated valve. Therefore, the fluid supplied to and discharged from the main valve 60 by the pilot valve 70 may be air, for example, compressed air. The fluid source 54 may be an air source, for example, a compressed air source.

[0058] The pilot valve 70 may be externally piloted and may be located outside the main valve 60 and connected to the main valve 60. In this case, the pilot valve 70 may be positioned in a fixed position relative to the main valve 60. For example, both the main valve 60 and the pilot valve 70 may be attached to the cryopump vessel 16 and connected to each other by piping 68 for fluid supply and discharge. Alternatively, the pilot valve 70 may be internally piloted and may be incorporated into the main valve 60.

[0059] In an exemplary configuration, the main valve 60 comprises a valve case 62 and a valve piston 64. The valve case 62 has a purge gas inlet 62a, a purge gas outlet 62b, and a fluid port 62c. The purge gas inlet 62a is connected to a purge gas source 48, and the purge gas outlet 62b is connected to a cryopump vessel 16. The purge gas inlet 62a and purge gas outlet 62b are opened and closed by the movement of the valve piston 64, as described later. The fluid port 62c is connected to a fluid source 54 through a pilot valve 70. The fluid port 62c is not opened or closed by the movement of the valve piston 64. The fluid port 62c is always open.

[0060] The valve piston 64 is arranged to reciprocate within the valve case 62. The volume within the valve case 62 is divided by the valve piston 64 into two chambers: a purge gas passage 65 and a fluid chamber 66. The purge gas passage 65 has a purge gas inlet 62a and a purge gas outlet 62b, and the fluid chamber 66 has a fluid port 62c.

[0061] Furthermore, the valve piston 64 is connected to the valve case 62 by a return spring 67. The return spring 67 is provided to keep the main valve 60 normally open. That is, the return spring 67 biases the valve piston 64 so that the purge gas passage 65 is normally open.

[0062] The pilot valve 70 has a supply port 71, a discharge port 72, and a main valve port 73. The pilot valve 70 may be a three-way valve. The supply port 71 is connected to a fluid source 54. As shown in the figure, the supply port 71 may also be connected to the fluid source 54 via a check valve 75. The discharge port 72 may be open to the ambient environment or connected to a fluid recovery tank (not shown). The main valve port 73 is connected to the fluid port 62c of the main valve 60 by piping 68.

[0063] In the first state of the pilot valve 70, the supply port 71 and the main valve port 73 are connected, as shown in Figure 3. In the first state, the discharge port 72 is closed. In the second state of the pilot valve 70, the discharge port 72 and the main valve port 73 are connected, as shown in Figure 4. In the second state, the supply port 71 is closed.

[0064] The pilot valve 70 may be equipped with a solenoid valve that switches between a first state and a second state. In this embodiment, the pilot valve 70 normally takes the second state. That is, the pilot valve 70 is driven to the first state when power is supplied and returns to the second state when power is not supplied, such as during a power outage.

[0065] In a safe state where no abnormalities such as power outages occur, for example during vacuum evacuation operation of the cryopump 10, the pilot valve 70 is powered and enters the first state. As shown in Figure 3, in the first state, the pilot valve 70 connects the fluid source 54 to the fluid chamber 66 of the main valve 60. As schematically shown by arrow 77, fluid is supplied from the fluid source 54 to the fluid chamber 66 through the pilot valve 70. The fluid pressure in the fluid chamber 66 is increased to exceed the pressure in the purge gas passage 65. Due to the fluid pressure in the fluid chamber 66, the valve piston 64 moves to reduce the volume of the purge gas passage 65, as schematically shown by arrow 78, blocking the purge gas inlet 62a and purge gas outlet 62b. The main valve 60 is closed, and the supply of purge gas from the purge gas source 48 to the cryopump vessel 16 is cut off. Thus, the body purge valve 20 is closed by power supply. Closing the body purge valve 20 maintains a vacuum in the cryopump vessel 16.

[0066] On the other hand, in unsafe conditions, the pilot valve 70 switches from the first state to the second state. For example, in the event of a power outage, the pilot valve 70 is not powered, so it returns from the first state to the second state. As shown in Figure 4, in the second state, the pilot valve 70 connects its discharge port 72 to the fluid chamber 66 of the main valve 60. The fluid source 54 is disconnected from the fluid chamber 66. As schematically shown by arrow 79, fluid is discharged from the fluid chamber 66 to the outside through the pilot valve 70, and the fluid pressure in the fluid chamber 66 is lost. Due to the restoring force of the return spring 67, the valve piston 64 moves to increase the volume of the purge gas passage 65, and the purge gas inlet 62a and purge gas outlet 62b are connected through the purge gas passage 65. Thus, the main valve 60, i.e., the body purge valve 20, is opened, and purge gas is supplied from the purge gas source 48 to the cryopump container 16, as schematically shown by arrow 76. The body purge valve 20 can perform a safety purge.

[0067] The fluid source 54 is typically a cylinder that stores fluid. As the fluid is consumed, the remaining pressure in the cylinder decreases, so the user of the cryopump 10 needs to replace the used cylinder with a new one in a timely manner. If use continues with insufficient remaining pressure in the cylinder, eventually the fluid source 54 will no longer be able to provide the fluid pressure to the fluid chamber 66 necessary to switch the pilot valve 70 to the first state. Alternatively, if the piping for fluid supply connected to the fluid source 54 is accidentally disconnected, the fluid supply to the pilot valve 70 will also be lost.

[0068] As shown in Figure 5, if the fluid source 54 is directly connected to the pilot valve 70 (i.e., without the check valve 75), then if the fluid supply from the fluid source 54 to the pilot valve 70 is lost, the fluid pressure in the fluid chamber 66 will decrease, or fluid will be discharged from the fluid chamber 66, as schematically shown by arrow 79. In this case, the main valve 60 will open as if the pilot valve 70 had returned to the second state, and purge gas will be supplied to the cryopump vessel 16, as schematically shown by arrow 76. Such an unintended safety purge will destroy the vacuum environment for the vacuum process, forcing the process to be interrupted. This is undesirable because it requires considerable time and expense to restart the process.

[0069] Therefore, the body purge valve 20 may be configured to restrict the discharge of fluid from the main valve 60 when the fluid supply from the fluid source 54 is lost in the first state of the pilot valve 70. In this way, when the fluid supply from the fluid source 54 to the fluid chamber 66 is lost due to insufficient pressure in the fluid source 54, accidental removal of piping, etc., the fluid pressure in the fluid chamber 66 can be maintained by restricting the discharge of fluid from the main valve 60, and the first state of the pilot valve 70 can be continued. Thus, unintended safety purging as described above can be prevented. On the other hand, in situations where safety purging is required, the execution of safety purging is not prevented. By switching the pilot valve 70 from the first state to the second state, fluid can be discharged from the fluid chamber 66, the main valve 60 can be opened, and safety purging can be performed.

[0070] As an exemplary configuration to address unintended safety purging, a check valve 75 may be used. As shown in the figure, the check valve 75 is located between the fluid source 54 and the supply port 71 of the pilot valve 70. The check valve 75 is connected between the fluid source 54 and the supply port 71 to allow forward fluid flow from the fluid source 54 to the supply port 71 and to prevent backflow of fluid from the supply port 71 to the fluid source 54.

[0071] Since the check valve 75 allows fluid flow from the fluid source 54 to the supply port 71, it does not obstruct the supply of fluid from the fluid source 54 to the main valve 60 through the pilot valve 70 in the first state of the pilot valve 70.

[0072] As shown in Figure 6, when the supply of fluid from the fluid source 54 to the fluid chamber 66 is lost, the check valve 75 prevents backflow of fluid from the supply port 71 towards the fluid source 54, thereby maintaining the fluid pressure in the fluid chamber 66 and allowing the pilot valve 70 to continue in the first state. Therefore, unintended safety purging as described above can be prevented. On the other hand, in situations where safety purging is required, the execution of safety purging is not hindered. In situations where safety purging is required, the pilot valve 70 can be switched from the first state to the second state to discharge fluid from the fluid chamber 66 and open the main valve 60, thereby executing a safety purge.

[0073] The check valve 75 may be positioned in a fixed location relative to the pilot valve 70. For example, both the pilot valve 70 and the check valve 75 may be attached to the cryopump vessel 16 and connected to each other by piping for fluid supply and discharge. This would prevent the piping from becoming detached due to accidental relative movement of the check valve 75 relative to the pilot valve 70. Alternatively, the check valve 75 may be attached to the supply port 71 of the pilot valve 70.

[0074] If the power outage is temporary, for example, if the main power is restored before the temperature rise in the cryopump 10 is high enough to cause re-vaporization of the gas, then safety purging is not necessarily required. Therefore, the cryopump 10 may be equipped with an uninterruptible power supply (UPS) function that enables temporary power supply during a main power outage. This allows the cryopump 10 to supply power to the purge valve and keep it closed, even during a power outage, within the power supply capacity of the UPS function. The UPS function may be designed to keep the purge valve closed for at least one minute, or at least two minutes. Alternatively, the UPS function may be designed to keep the purge valve closed for at most ten minutes, or at most five minutes.

[0075] Figure 7 is a schematic diagram illustrating the power supply system of the purge valve of the cryopump 10 according to an embodiment. The purge valve, for example, the body purge valve 20, may include a main valve 60 and a pilot valve 70, as described above.

[0076] As described above, the pilot valve 70 may be a solenoid valve that normally takes the second state. When the pilot valve 70 is in the second state, if a drive voltage is supplied to the pilot valve 70 from the power supply system, the pilot valve 70 is driven to the first state. In this way, the pilot valve 70 switches from the second state to the first state. When the pilot valve 70 is in the first state, if the supply voltage from the power supply system exceeds the recovery voltage, the pilot valve 70 remains in the first state. The pilot valve 70 returns from the first state to the second state when the supply voltage from the power supply system drops below the recovery voltage.

[0077] The drive voltage is the rated voltage of the pilot valve 70, and may be a DC voltage such as 12V or 24V. The recovery voltage of the pilot valve 70 is a voltage lower than the drive voltage. For example, the recovery voltage may be lower than half of the drive voltage.

[0078] As shown in the figure, the power supply system comprises a main power supply 80, a backup power supply 82 that provides uninterruptible power supply functionality, and a power supply controller 90 that controls both power supplies. The main power supply 80 and the backup power supply 82 are connected to the body purge valve 20 through a power supply line 81. The power supply controller 90 may be included in the cryopump controller 46.

[0079] The main power supply 80 is configured to generate drive power for the pilot valve 70 from an external power source such as a DC power supply. When the main power supply 80 is energized, the power supply controller 90 operates on power supplied from the main power supply 80 and controls the power supply from the main power supply 80 to the pilot valve 70. The power supply controller 90 may receive a command to close the body purge valve 20 from the cryopump controller 46, and have the main power supply 80 supply a drive voltage to the pilot valve 70, thereby switching the pilot valve 70 from the second state to the first state and closing the body purge valve 20. Alternatively, the power supply controller 90 may receive a command to open the body purge valve 20 from the cryopump controller 46, and stop the power supply from the main power supply 80 to the pilot valve 70, thereby returning the pilot valve 70 from the first state to the second state and opening the body purge valve 20.

[0080] The backup power supply 82 is connected to the pilot valve 70 by a power supply line 81 and is configured to supply power to the pilot valve 70 in place of the main power supply 80 in the event of a failure of the main power supply 80. The backup power supply 82 may also supply power to the pilot valve 70 in the event of a failure of the main power supply 80 under the control of the power supply controller 90. The backup power supply 82 may also be connected to the power supply controller 90 and is configured to supply power to the power supply controller 90 in place of the main power supply 80 in the event of a failure of the main power supply 80. The power supply controller 90 may be considered to be part of the backup power supply 82.

[0081] The backup power supply 82 includes an energy storage element 83. For example, the energy storage element 83 may be an electric double-layer capacitor (also called a supercapacitor). As shown in Figure 7, the energy storage element 83 may be connected to the power supply controller 90 to supply power to the power supply controller 90 in place of the main power supply 80 in the event of a power outage of the main power supply 80.

[0082] Furthermore, if the rated voltage of the energy storage element 83 is lower than the recovery voltage of the pilot valve 70, the backup power supply 82 may include multiple energy storage elements 83 connected in series, and the sum of the rated voltages of these multiple energy storage elements 83 may be higher than the recovery voltage of the pilot valve 70. Alternatively, the sum of the rated voltages of these multiple energy storage elements 83 may be higher than the drive voltage of the pilot valve 70.

[0083] The backup power supply 82 may include a switch 84 between the pilot valve 70 and the energy storage element 83. The switch 84 may be connected between the power supply line 81 and the energy storage element 83. The switch 84 may be controlled by the power supply controller 90. For example, the power supply controller 90 turns off the switch 84 when the main power supply 80 is energized, disconnecting the energy storage element 83 from the pilot valve 70. Also, the power supply controller 90 turns on the switch 84 when the main power supply 80 fails, connecting the energy storage element 83 to the pilot valve 70.

[0084] Therefore, in the event of a power outage of the main power supply 80, power can be supplied to the pilot valve 70 from the energy storage element 83. If the pilot valve 70 is in the first state at the time of the power outage, the pilot valve 70 will remain in the first state as long as the supply voltage from the energy storage element 83 to the pilot valve 70 is equal to or greater than the recovery voltage. When the power supplied to the pilot valve 70 consumes the power stored in the energy storage element 83, and the supply voltage from the energy storage element 83 to the pilot valve 70 falls below the recovery voltage, the pilot valve 70 returns from the first state to the second state.

[0085] Furthermore, the backup power supply 82 may include a boost circuit 85 between the pilot valve 70 and the energy storage element 83. The boost circuit 85 may be connected in parallel with the switch 84 between the power supply line 81 and the energy storage element 83. The boost circuit 85 may be configured to boost the output voltage of the energy storage element 83 to a level higher than the return voltage of the pilot valve 70, thereby generating a supply voltage to the pilot valve 70. The boost circuit 85 may be, for example, a boost converter.

[0086] The boost circuit 85 may also be a buck-boost circuit, for example, a buck-boost converter. In this case, when the energy storage element 83 is charged by the main power supply 80, the boost circuit 85 may reduce the voltage of the main power supply 80 and supply it to the energy storage element 83.

[0087] The boost circuit 85 may be controlled by a power supply controller 90. For example, the power supply controller 90 may be configured to detect the output voltage of the energy storage element 83 and compare the output voltage of the energy storage element 83 with a voltage threshold. The voltage threshold may be equal to the recovery voltage of the pilot valve 70. Alternatively, the voltage threshold may be a voltage value higher than the recovery voltage, for example, a voltage value 0.1V to 1V higher than the recovery voltage.

[0088] The power supply controller 90 may turn off the boost circuit 85 when the output voltage of the energy storage element 83 is equal to or greater than the voltage threshold. In this case, the output voltage of the energy storage element 83 is supplied directly to the pilot valve 70. Since the supply voltage from the energy storage element 83 to the pilot valve 70 is equal to or greater than the recovery voltage, the pilot valve 70 is maintained in the first state.

[0089] On the other hand, the power supply controller 90 may turn on the boost circuit 85 when the output voltage of the energy storage element 83 falls below a voltage threshold. In this case, the output voltage of the energy storage element 83 is boosted by the boost circuit 85 to a level above the recovery voltage and supplied to the pilot valve 70. The pilot valve 70 is maintained in the first state until the power stored in the energy storage element 83 is consumed.

[0090] As another example, the boost circuit 85 may be connected in series with the switch 84 between the power supply line 81 and the energy storage element 83. The boost circuit 85 may be configured to detect the output voltage of the energy storage element 83 and compare the output voltage of the energy storage element 83 with a voltage threshold. When the output voltage of the energy storage element 83 is above the voltage threshold, the boost circuit 85 may supply the output voltage of the energy storage element 83 directly to the pilot valve 70. On the other hand, when the output voltage of the energy storage element 83 falls below the voltage threshold, the boost circuit 85 may boost the output voltage of the energy storage element 83 to above the recovery voltage and supply it to the pilot valve 70.

[0091] In this way, the backup power supply 82 can extend the backup time it can supply power to the pilot valve 70 by utilizing the boost circuit 85. Alternatively, to achieve an equivalent backup time, the backup power supply 82 can be equipped with a smaller energy storage element 83, which is advantageous.

[0092] Extending the backup time by using the boost circuit 85 allows for a decrease in the charge level of the energy storage element 83. In other words, the backup power supply 82 can achieve the same backup time with an energy storage element 83 at a lower charge level. When the energy storage element 83 is repeatedly charged, the higher the charge level, the shorter the lifespan of the energy storage element 83 tends to be. Therefore, a decrease in the charge level of the energy storage element 83 is advantageous because it can contribute to extending the lifespan of the energy storage element 83.

[0093] Furthermore, as shown in Figure 7, the backup power supply 82 may be equipped with a power storage element monitor 92. The power storage element monitor 92 may constitute part of the power supply controller 90.

[0094] The energy storage element monitor 92 may be configured to monitor the energy storage element 83 by discharging it. The energy storage element monitor 92 and the energy storage element 83 may be connected to each other to form a discharge circuit that discharges the energy storage element 83. The energy storage element monitor 92 may be connected to the energy storage element 83 via a power supply line 81. As an example, the energy storage element monitor 92 may include a constant current circuit that discharges the energy storage element 83 with a constant current. The constant current circuit may be a known constant current circuit.

[0095] The energy storage element monitor 92 may also monitor the capacity C(F) of the energy storage element 83. For example, when the energy storage element 83 is discharged by a constant current circuit that flows a constant current I(A), the capacity C(F) of the energy storage element 83 is expressed by the following formula. C = I × T / ΔV

[0096] Here, ΔV (=V1-V2) represents the voltage difference between the discharge start voltage V1 (V) and the discharge end voltage V2 of the energy storage element 83, and T (seconds) represents the discharge time required for the energy storage element 83 (i.e., the time required for the energy storage element 83 to discharge at a constant current I from the discharge start voltage V1 to the discharge end voltage V2).

[0097] When the energy storage element 83 is discharged into the constant current circuit of the energy storage element monitor 92, the energy storage element monitor 92 measures the constant current I, the voltage difference ΔV, and the discharge time T, and calculates the capacity C of the energy storage element 83. In this way, the energy storage element monitor 92 can monitor the capacity C(F) of the energy storage element 83.

[0098] The energy storage element monitor 92 may compare the calculated capacity C with a capacity threshold. If the calculated capacity C exceeds the capacity threshold, the energy storage element monitor 92 may determine that the energy storage element 83 is normal. The energy storage element monitor 92 may output information indicating that the energy storage element 83 is normal. On the other hand, if the calculated capacity C is less than or equal to the capacity threshold, the energy storage element monitor 92 may determine that the energy storage element 83 is abnormal. The energy storage element monitor 92 may output information indicating that the energy storage element 83 is abnormal (for example, that the capacity of the energy storage element 83 has decreased).

[0099] In this way, the energy storage element monitor 92 can monitor the energy storage element 83 and detect abnormalities. For example, the energy storage element monitor 92 can detect a decrease in the capacity of the energy storage element 83 due to deterioration over time or other causes.

[0100] The present invention has been described above based on examples. Those skilled in the art will understand that the present invention is not limited to the above embodiments, that various design changes are possible, and that various modifications are possible, and that such modifications also fall within the scope of the present invention. Various features described in relation to one embodiment are applicable to other embodiments. New embodiments resulting from combinations will possess the combined effects of each of the embodiments combined.

[0101] In the above-described embodiment, the case in which a check valve 75 is used to deal with unintended safety purging is explained as an example, but other configurations are also possible. For example, instead of the check valve 75, a flow resistance such as an orifice may be provided between the fluid source 54 and the supply port 71. In this case, the flow resistance can limit the discharge of fluid from the main valve 60 when the fluid supply from the fluid source 54 is lost in the first state of the pilot valve 70. This suppresses a rapid drop in the fluid pressure in the fluid chamber 66, thereby allowing the first state of the pilot valve 70 to continue to some extent and delaying the occurrence of unintended safety purging.

[0102] Alternatively, instead of the check valve 75, an on-off valve may be provided between the fluid source 54 and the supply port 71. In addition to the on-off valve, a pressure gauge may be provided to measure the pressure in the fluid chamber 66. If the pressure measured by the pressure gauge is sufficient to maintain the first state of the pilot valve 70, the on-off valve may be closed manually or under the control of the cryopump controller 46. In this way, the on-off valve, like the check valve 75, prevents backflow of fluid from the supply port 71 to the fluid source 54, thereby maintaining the fluid pressure in the fluid chamber 66 and allowing the pilot valve 70 to continue in the first state. The on-off valve may be opened manually or under the control of the cryopump controller 46 when the pilot valve 70 is in the second state. In this way, when the pilot valve 70 is switched from the second state to the first state, fluid can be supplied again from the fluid source 54 to the fluid chamber 66 through the on-off valve.

[0103] In the above-described embodiment, the case in which the body purge valve 20 comprises a main valve 60 and a pilot valve 70 is described as an example. However, the discharge purge valve 24 may have a configuration in which it comprises a main valve 60 and a pilot valve 70 together with the body purge valve 20, or in place of the body purge valve 20. In this case, the discharge purge valve 24 may be configured to restrict the discharge of fluid from the main valve 60 when the fluid supply from the fluid source 54 is lost in the first state of the pilot valve 70.

[0104] Although the present invention has been described using specific terms based on the embodiments, the embodiments only illustrate one aspect of the principle and application of the present invention, and many modifications and changes in arrangement are permitted in the embodiments, as long as they do not depart from the spirit of the present invention as defined in the claims. [Explanation of symbols]

[0105] 10 cryopumps, 16 cryopump vessels, 54 fluid sources, 60 main valves, 70 pilot valves, 71 supply ports, 73 main valve ports, 75 check valves, 82 backup power supplies, 83 energy storage elements, 85 boost circuits, 92 energy storage element monitors.

Claims

1. A main valve that is closed by the supply of fluid from a fluid source to shut off the purge gas, and opened by the discharge of the fluid to supply the purge gas, The purge valve includes a pilot valve that switches between a first state in which the fluid is supplied from the fluid source to the main valve and a second state in which the fluid is discharged from the main valve. The cryopump is characterized in that the purge valve is configured to limit the discharge of the fluid from the main valve when the fluid supply from the fluid source is lost in the first state of the pilot valve.

2. The pilot valve comprises a supply port connected to the fluid source and a main valve port connected to the main valve, and in the first state, the supply port and the main valve port are in communication. The cryopump according to claim 1, wherein the purge valve is provided between the fluid source and the supply port and includes a check valve to prevent backflow of the fluid from the supply port toward the fluid source.

3. The cryopump vessel is further connected to the main valve, The cryopump according to claim 1 or 2, characterized in that the main valve is closed when the pilot valve is in the first state to shut off the supply of the purge gas to the cryopump container, and is opened when the pilot valve is in the second state to supply the purge gas to the cryopump container.

4. The system further includes a backup power supply connected to the pilot valve, The pilot valve includes a solenoid valve that returns from the first state to the second state when the supply voltage drops below the recovery voltage. The aforementioned backup power supply is Energy storage element, The cryopump according to claim 1 or 2, further comprising a boost circuit that increases the output voltage of the energy storage element to exceed the recovery voltage of the solenoid valve in order to generate the supply voltage to the solenoid valve.

5. The system further includes a backup power supply connected to the pilot valve, The aforementioned backup power supply is Energy storage element, The cryopump according to claim 1 or 2, further comprising a storage element monitor that monitors the storage element by discharging it.

6. A main valve that is closed by the supply of fluid from a fluid source to shut off the purge gas, and opened by the discharge of the fluid to supply the purge gas, A purge valve comprising a pilot valve that switches between a first state in which the fluid is supplied from the fluid source to the main valve and a second state in which the fluid is discharged from the main valve, The system includes a backup power supply connected to the pilot valve, The pilot valve includes a solenoid valve that returns from the first state to the second state when the supply voltage drops below the recovery voltage. The aforementioned backup power supply is Energy storage element, A cryopump comprising a boost circuit that generates the supply voltage to the solenoid valve by boosting the output voltage of the energy storage element to exceed the return voltage of the solenoid valve.

7. A main valve that is closed by the supply of fluid from a fluid source to shut off the purge gas, and opened by the discharge of the fluid to supply the purge gas, A purge valve comprising a pilot valve that switches between a first state in which the fluid is supplied from the fluid source to the main valve and a second state in which the fluid is discharged from the main valve, The system includes a backup power supply connected to the pilot valve, The aforementioned backup power supply is Energy storage element, A cryopump comprising a storage element monitor that monitors the storage element by discharging it.

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