Patent Publication Number: US-2021190058-A1

Title: Cryopump

Description:
RELATED APPLICATIONS 
     The contents of Japanese Patent Application No. 2018-167178, and of International Patent Application No. PCT/JP2019/030303, on the basis of each of which priority benefits are claimed in an accompanying application data sheet, are in their entirety incorporated herein by reference. 
    
    
     BACKGROUND 
     Technical Field 
     Certain embodiments of the present invention relate to a cryopump. 
     Description of Related Art 
     A cryopump is a vacuum pump which captures gas molecules on a cryopanel cooled to a cryogenic temperature by condensation or adsorption to pump the gas molecules. The cryopump is generally used to realize a clean vacuum environment which is required for a semiconductor circuit manufacturing process or the like. 
     SUMMARY 
     According to an embodiment of the present invention, there is provided a cryopump including: a cryopump housing having a cryopump intake port; a radiation shield that is disposed inside the cryopump housing in a non-contact manner with the cryopump housing and is cooled to a shield cooling temperature; and a heat shielding dummy panel that is disposed at the cryopump intake port and mounted to the radiation shield through a thermal resistance member such that a dummy panel temperature becomes higher than the shield cooling temperature. 
     According to another embodiment of the present invention, there is provided a cryopump including: a cryopump housing having a cryopump intake port; a radiation shield that is disposed inside the cryopump housing in a non-contact manner with the cryopump housing and is cooled to a shield cooling temperature; and a heat shielding dummy panel that is disposed at the cryopump intake port and thermally coupled to the cryopump housing such that a dummy panel temperature becomes higher than the shield cooling temperature. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram schematically showing a cryopump according to a certain embodiment. 
         FIG. 2  is a schematic perspective view of the cryopump shown in  FIG. 1 . 
         FIG. 3  is a diagram schematically showing a cryopump according to another embodiment. 
         FIG. 4  is a schematic perspective view of a cryopump according to still another embodiment. 
         FIG. 5  is a partial sectional view schematically showing a portion of the cryopump shown in  FIG. 4 . 
         FIG. 6  is a schematic perspective view of a cryopump according to still yet another embodiment. 
         FIG. 7  is a partial sectional view schematically showing a portion of the cryopump shown in  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION 
     A cryopanel that is cooled to a cryogenic temperature of, for example, about 100 K is disposed at an intake port of the cryopump. In the design of a cryopump of the related art, it is thought that such an intake port cryopanel is essential. However, the inventor of the present invention doubted such a common view and newly found that a cryopump having a different design could also be realized. 
     It is desirable to provide a cryopump with a new and alternative design. 
     Any combination of the constituent elements described above, or replacement of constituent elements or expressions of the present invention with each other between methods, apparatuses, systems, or the like is also valid as an aspect of the present invention. 
     Hereinafter, modes for carrying out the present invention will be described in detail with reference to the drawings. In the description and the drawings, identical or equivalent constituent elements, members, and processing are denoted by the same reference numerals, and overlapping description is omitted appropriately. The scales or shapes of the respective parts shown in the drawings are set for convenience in order to facilitate description and are not interpreted to a limited extent unless otherwise specified. Embodiments are exemplification and do not limit the scope of the present invention. All features described in the embodiments or combinations thereof are not necessarily essential to the invention. 
       FIG. 1  schematically shows a cryopump  10  according to a certain embodiment.  FIG. 2  is a schematic perspective view of the cryopump  10  shown in  FIG. 1 . 
     The cryopump  10  is mounted to a vacuum chamber of, for example, an ion implanter, a sputtering apparatus, a vapor deposition apparatus, or other vacuum process equipment and is used to increase the degree of vacuum in the interior of the vacuum chamber to a level which is required for a desired vacuum process. The cryopump  10  has a cryopump intake port (hereinafter, also simply referred to as an “intake port”)  12  for receiving a gas to be pumped, from the vacuum chamber. The gas enters an internal space  14  of the cryopump  10  through the intake port  12 . 
     In the following, there is a case where the terms “axial direction” and “radial direction” are used in order to express the positional relationship between constituent elements of the cryopump  10  in an easily understandable manner. The axial direction of the cryopump  10  represents a direction passing through the intake port  12  (that is, a direction along a central axis C in the drawing), and the radial direction represents a direction along the intake port  12  (a first direction in the plane perpendicular to the central axis C). For convenience, with respect to the axial direction, there is a case where the side relatively close to the intake port  12  is referred to as an “upper side” and the side relatively distant from the intake port  12  is referred to as a “lower side”. That is, there is a case where the side relatively distant from the bottom of the cryopump  10  is referred to as an “upper side” and the side relatively close to the bottom of the cryopump  10  is referred to as a “lower side”. With respect to the radial direction, there is a case where the side close to the center (in the drawing, the central axis C) of the intake port  12  is referred to as an “inner side” and the side close to the peripheral edge of the intake port  12  is referred to as an “outer side”. Such expressions are not related to the disposition when the cryopump  10  is mounted to the vacuum chamber. For example, the cryopump  10  may be mounted to the vacuum chamber with the intake port  12  facing downward in the vertical direction. 
     Further, there is a case where a direction surrounding the axial direction is referred to as a “circumferential direction”. The circumferential direction is a second direction along the intake port  12  (a second direction in the plane perpendicular to the central axis C) and is a tangential direction orthogonal to the radial direction. 
     The cryopump  10  includes a cryocooler  16 , a radiation shield  30 , a second-stage cryopanel assembly  20 , and a cryopump housing  70 . The radiation shield  30  may be referred to as a first-stage cryopanel, a high-temperature cryopanel part, or a 100 K part. The second-stage cryopanel assembly  20  may be referred to as a low-temperature cryopanel part or a 10 K part. 
     The cryocooler  16  is a cryocooler such as a Gifford McMahon type cryocooler (a so-called GM cryocooler), for example. The cryocooler  16  is a two-stage cryocooler. Therefore, the cryocooler  16  includes a first cooling stage  22  and a second cooling stage  24 . The cryocooler  16  is configured to cool the first cooling stage  22  to a first cooling temperature and cool the second cooling stage  24  to a second cooling temperature. The second cooling temperature is lower than the first cooling temperature. For example, the first cooling stage  22  is cooled to a temperature in a range of about 65 K to 120 K, preferably, in a range of 80 K to 100 K, and the second cooling stage  24  is cooled to a temperature in a range of about 10 K to 20 K. The first cooling stage  22  and the second cooling stage  24  may be referred to as a high-temperature cooling stage and a low-temperature cooling stage, respectively. 
     Further, the cryocooler  16  includes a cryocooler structure part  21  that structurally supports the second cooling stage  24  on the first cooling stage  22  and structurally supports the first cooling stage  22  on a room temperature part  26  of the cryocooler  16 . Therefore, the cryocooler structure part  21  includes a first cylinder  23  and a second cylinder  25  that extend coaxially along the radial direction. The first cylinder  23  connects the room temperature part  26  of the cryocooler  16  to the first cooling stage  22 . The second cylinder  25  connects the first cooling stage  22  to the second cooling stage  24 . The room temperature part  26 , the first cylinder  23 , the first cooling stage  22 , the second cylinder  25 , and the second cooling stage  24  are linearly arranged in this order. 
     A first displacer and a second displacer (not shown) are reciprocally disposed in the interiors of the first cylinder  23  and the second cylinder  25 , respectively. A first regenerator and a second regenerator (not shown) are respectively incorporated into the first displacer and the second displacer. Further, the room temperature part  26  has a drive mechanism (not shown) for reciprocating the first displacer and the second displacer. The drive mechanism includes a flow path switching mechanism that switches a flow path of a working gas (for example, helium) so as to periodically repeat the supply and discharge of the working gas to and from the interior of the cryocooler  16 . 
     The cryocooler  16  is connected to a compressor (not shown) for the working gas. The cryocooler  16  cools the first cooling stage  22  and the second cooling stage  24  by expanding the working gas pressurized by the compressor in the interior thereof. The expanded working gas is recovered to the compressor and pressurized again. The cryocooler  16  generates cold by repeating a thermodynamic cycle (for example, a refrigeration cycle such as a GM cycle) including the supply and discharge of the working gas and the reciprocation of the first displacer and the second displacer in synchronization with the supply and discharge of the working gas. 
     The cryopump  10  which is shown in the drawing is a so-called horizontal cryopump. The horizontal cryopump is generally a cryopump in which the cryocooler  16  is disposed so as to intersect (usually, be orthogonal to) the central axis C of the cryopump  10 . 
     The radiation shield  30  surrounds the second-stage cryopanel assembly  20 . The radiation shield  30  provides a cryogenic surface for protecting the second-stage cryopanel assembly  20  from a radiant heat outside the cryopump  10  or from the cryopump housing  70 . The radiation shield  30  is thermally coupled to the first cooling stage  22 . 
     Accordingly, the radiation shield  30  is cooled to the first cooling temperature. The radiation shield  30  has a gap between itself and the second-stage cryopanel assembly  20 , and the radiation shield  30  is not in contact with the second-stage cryopanel assembly  20 . The radiation shield  30  is also not in contact with the cryopump housing  70 . 
     The radiation shield  30  is provided to protect the second-stage cryopanel assembly  20  from the radiant heat of the cryopump housing  70 . The radiation shield  30  extends in a tubular shape (for example, a cylindrical shape) in the axial direction from the intake port  12 . The radiation shield  30  is located between the cryopump housing  70  and the second-stage cryopanel assembly  20  and surrounds the second-stage cryopanel assembly  20 . The radiation shield  30  has a shield main opening  34  for receiving gas from the outside of the cryopump  10  into the internal space  14 . The shield main opening  34  is located at the intake port  12 . 
     The radiation shield  30  is formed of a high heat conductive metal material such as copper (for example, pure copper), for example. Further, the radiation shield  30  may have a metal plating layer containing, for example, nickel and formed on the surface thereof, in order to improve corrosion resistance, as necessary. 
     The radiation shield  30  is provided with a shield front end  36  defining the shield main opening  34 , a shield bottom portion  38  which is located on the side opposite to the shield main opening  34 , and a shield side portion  40  connecting the shield front end  36  to the shield bottom portion  38 . The shield side portion  40  extends in the axial direction from the shield front end  36  to the side opposite to the shield main opening  34 , and extends so as to surround the second cooling stage  24  in the circumferential direction. 
     The shield side portion  40  has a shield side portion opening  44  into which the cryocooler structure part  21  is inserted. The second cooling stage  24  and the second cylinder  25  are inserted into the radiation shield  30  from outside the radiation shield  30  through the shield side portion opening  44 . The shield side portion opening  44  is a mounting hole formed in the shield side portion  40  and is, for example, circular. The first cooling stage  22  is disposed outside the radiation shield  30 . 
     The shield side portion  40  is provided with a mounting seat  46  for the cryocooler  16 . The mounting seat  46  is a flat portion for mounting the first cooling stage  22  to the radiation shield  30 , and is slightly depressed when viewed from outside the radiation shield  30 . The mounting seat  46  forms the outer periphery of the shield side portion opening  44 . The first cooling stage  22  is mounted to the mounting seat  46 , whereby the radiation shield  30  is thermally coupled to the first cooling stage  22 . 
     Instead of directly mounting the radiation shield  30  to the first cooling stage  22  in this manner, in an embodiment, the radiation shield  30  may be thermally coupled to the first cooling stage  22  through an additional heat transfer member. The heat transfer member may be, for example, a hollow short cylinder having flanges at both ends. The heat transfer member may be fixed to the mounting seat  46  by the flange at one end and fixed to the first cooling stage  22  by the flange at the other end. The heat transfer member may extend from the first cooling stage  22  to the radiation shield  30  to surround the cryocooler structure part  21 . The shield side portion  40  may include such a heat transfer member. 
     In the illustrated embodiment, the radiation shield  30  is configured in an integral tubular shape. Instead, the radiation shield  30  may be configured to have a tubular shape as a whole by a plurality of parts. The plurality of parts may be disposed with a gap therebetween. For example, the radiation shield  30  may be divided into two parts in the axial direction. 
     The cryopump  10  includes a heat shielding dummy panel  32  disposed at the intake port  12 . The heat shielding dummy panel  32  is mounted to the radiation shield  30  through a thermal resistance member  48  such that a dummy panel temperature becomes higher than a shield cooling temperature (for example, the first cooling temperature described above). 
     In other words, the heat shielding dummy panel  32  is disposed at the intake port  12  so as to avoid cooling by the cryocooler  16  as much as possible. The heat shielding dummy panel  32  is not a “cryopanel” intended to be cooled to a cryogenic temperature. Accordingly, the heat shielding dummy panel  32  may be designed such that the dummy panel temperature exceeds 0° C. during the operation of the cryopump  10 . However, depending on the design of the thermal resistance member  48  and/or a method of mounting the heat shielding dummy panel  32  to the radiation shield  30 , the dummy panel temperature may fall below 0° C. during the operation of the cryopump  10 . However, even in that case, the dummy panel temperature is maintained at a temperature higher than the shield cooling temperature. 
     The heat shielding dummy panel  32  is provided at the intake port  12  (or the shield main opening  34 , the same applies hereinafter) in order to protect the second-stage cryopanel assembly  20  from a radiant heat from a heat source outside the cryopump  10  (for example, a heat source in the vacuum chamber to which the cryopump  10  is mounted). Since the heat shielding dummy panel  32  is not almost or entirely cooled by the cryocooler  16 , it does not have a function of condensing a gas (for example, a function of pumping a type 1 gas such as water vapor). 
     The heat shielding dummy panel  32  is disposed at a location corresponding to the second-stage cryopanel assembly  20  at the intake port  12 , for example, directly above the second-stage cryopanel assembly  20 . The heat shielding dummy panel  32  occupies the central portion of the opening area of the intake port  12 , and forms an annular (for example, circular ring-shaped) open area  51  between itself and the radiation shield  30 . 
     The heat shielding dummy panel  32  is disposed at the central portion of the intake port  12 . The center of the heat shielding dummy panel  32  is located on the central axis C. However, the center of the heat shielding dummy panel  32  may be located somewhat off from the central axis C, and even in that case, the heat shielding dummy panel  32  can be regarded as being located at the central portion of the intake port  12 . The heat shielding dummy panel  32  is disposed perpendicular to the central axis C. 
     Further, with respect to the axial direction, the heat shielding dummy panel  32 , may be disposed slightly above the shield front end  36 . In that case, since the heat shielding dummy panel  32  can be disposed farther from the second-stage cryopanel assembly  20 , the thermal action (that is, cooling) on the heat shielding dummy panel  32  from the second-stage cryopanel assembly  20  can be reduced. Alternatively, the heat shielding dummy panel  32  may be disposed at substantially the same height as the shield front end  36  in the axial direction, or slightly below the shield front end  36  in the axial direction. 
     The heat shielding dummy panel  32  is formed of a single flat plate. The heat shielding dummy panel  32  has a dummy panel central portion  32   a  and a dummy panel mounting portion  32   b  extending radially outward from the dummy panel central portion  32   a . The shape of the dummy panel central portion  32   a  when viewed in the axial direction is, for example, a disk shape. The diameter of the dummy panel central portion  32   a  is relatively small and is smaller than the diameter of the second-stage cryopanel assembly  20 , for example. The dummy panel central portion  32   a  may occupy at most ⅓ or at most ¼ of the opening area of the intake port  12 . In this way, the open area  51  may occupy at least ⅔ or at least ¾ of the opening area of the intake port  12 . 
     The dummy panel central portion  32   a  is mounted to the thermal resistance member  48  through the dummy panel mounting portion  32   b . As shown in  FIGS. 1 and 2 , the dummy panel mounting portion  32   b  is linearly bridged to the thermal resistance member  48  along the diameter of the shield main opening  34 . Further, the dummy panel mounting portion  32   b  divides the open area  51  in the circumferential direction. The open area  51  is composed of a plurality of (for example, two) arc-shaped areas. The dummy panel mounting portions  32   b  are provided on both sides of the dummy panel central portion  32   a . However, the dummy panel mounting portions  32   b  may extend in four directions from the dummy panel central portion  32   a  so as to form a cross shape when viewed in the axial direction, or may have other shapes. Here, the dummy panel central portion  32   a  and the dummy panel mounting portion  32   b  of the heat shielding dummy panel  32  are integrally formed. However, the dummy panel central portion  32   a  and the dummy panel mounting portion  32   b  may be provided as separate members and joined to each other. 
     Since the heat shielding dummy panel  32  is not a cryopanel, it does not require as high thermal conductivity as the cryopanel. Therefore, the heat shielding dummy panel  32  does not need to be formed of high thermal conductivity metal such as copper, and may be formed of, for example, stainless steel or other easily available metal material. Alternatively, the heat shielding dummy panel  32  may be formed of a metal material, a resin material (for example, a fluororesin material such as polytetrafluoroethylene), or any other material as long as it is suitable for use in a vacuum environment. Further, a part (for example, the dummy panel central portion  32   a ) of the heat shielding dummy panel  32  may be formed of a metal material, and the other part (for example, the dummy panel mounting portion  32   b ) of the heat shielding dummy panel  32  may be formed of a resin material. 
     The thermal resistance member  48  is formed of a material having a lower thermal conductivity than the material (for example, pure copper, as described above) of the radiation shield  30 , or a heat insulating material. In a case where it is considered that it is important to reduce the heat conduction between the radiation shield  30  and the heat shielding dummy panel  32 , the thermal resistance member  48  may be formed of, for example, a fluororesin material such as polytetrafluoroethylene, or other resin material. In a case where it is considered that it is important to reduce the thermal shrinkage of the thermal resistance member  48  and more reliably fix the heat shielding dummy panel  32  (for example, to prevent loosening of bolts), the thermal resistance member  48  may be formed of a metal material such as stainless steel, for example. 
     The thermal resistance member  48  is fixed to the inner peripheral surface of the shield front end  36  to correspond to the dummy panel mounting portion  32   b  of the heat shielding dummy panel  32 . As shown in the drawings, in a case where two dummy panel mounting portions  32   b  are provided on both sides of the dummy panel central portion  32   a , two thermal resistance members  48  are provided. The thermal resistance member  48  is fixed to the shield front end  36  by a fastening member such as a bolt or other appropriate method. The tip part of the dummy panel mounting portion  32   b  is fixed to the thermal resistance member  48  by a fastening member such as a bolt or other appropriate method. The smaller the contact area between the dummy panel mounting portion  32   b  and the thermal resistance member  48  and/or the cross-sectional area of the thermal resistance member  48  and/or the contact area between the thermal resistance member  48  and the shield front end  36 , the smaller the heat conduction between the radiation shield  30  and the heat shielding dummy panel  32  can become. 
     In this way, the heat shielding dummy panel  32  is thermally insulated from the radiation shield  30  or is connected to the radiation shield  30  through a high thermal resistance. The heat shielding dummy panel  32  is disposed at the intake port  12  so as to be in non-contact with the shield front end  36  and other portions of the radiation shield  30 . Further, the heat shielding dummy panel  32  is close to, but not in contact with, the second-stage cryopanel assembly  20 . 
     The heat shielding dummy panel  32  includes a dummy panel outer surface  32   c  facing the outside of the cryopump  10 , and a dummy panel inner surface  32   d  facing the inside of the cryopump  10 . The dummy panel outer surface  32   c  can also be referred to as a dummy panel upper surface, and the dummy panel inner surface  32   d  can also be referred to as a dummy panel lower surface. 
     An emissivity of the dummy panel outer surface  32   c  may be higher than an emissivity of the dummy panel inner surface  32   d . That is, reflectance of the dummy panel outer surface  32   c  may be lower than reflectance of the dummy panel inner surface  32   d . Therefore, the dummy panel outer surface  32   c  may have a black surface. The black surface may be formed, for example, by black painting, black plating, or other blackening treatment. Alternatively, the dummy panel outer surface  32   c  may have a rough surface. The dummy panel outer surface  32   c  may be subjected to, for example, sandblasting or other roughening treatment. The dummy panel inner surface  32   d  may have a mirror surface. The dummy panel inner surface  32   d  may be subjected to polishing or other mirror surface treatment. 
     As a first example, a case where both the dummy panel outer surface  32   c  and the dummy panel inner surface  32   d  are black is considered. In this case, both the emissivity of the dummy panel outer surface  32   c  and the emissivity of the dummy panel inner surface  32   d  are regarded as being 1. Heat input to the heat shielding dummy panel  32  among the heat input to the cryopump  10  is defined as Q [W]. When the heat shielding dummy panel  32  receives the heat input Q, a radiant heat Wo [W] that is radiated by the dummy panel outer surface  32   c  is Wo=(1/(1+1))Q=Q/2, and a radiant heat Wi [W] that is radiated by the dummy panel inner surface  32   d  is Wi=(1/(1+1))Q=Q/2. That is, the outward radiant heat Wo and the inward radiant heat Wi are equal. The radiant heat Wo is discharged from the dummy panel outer surface  32   c  to the outside of the cryopump  10 . The radiant heat Wi goes from the dummy panel inner surface  32   d  toward the inside of the cryopump  10 , that is, the radiation shield  30  and the second-stage cryopanel assembly  20 . However, it is cooled by the cryocooler  16  and discharged from the cryopump  10 . 
     As a second example, a case where the dummy panel outer surface  32   c  is black and the dummy panel inner surface  32   d  is a mirror surface is considered. The emissivity of the dummy panel outer surface  32   c  is regarded as being 1. The emissivity of the dummy panel inner surface  32   d  is assumed to be 0.1, for example. In this case, when the heat shielding dummy panel  32  receives the heat input Q, the radiant heat Wo [W] that is radiated by the dummy panel outer surface  32   c  is Wo=(1/(1+0.1))Q=(10/11)Q, and the radiant heat Wi [W] that is radiated by the dummy panel inner surface  32   d  is Wi=(0.1/(1+0.1))Q=(1/11)Q. 
     Therefore, by making the emissivity of the dummy panel outer surface  32   c  higher than the emissivity of the dummy panel inner surface  32   d , it is possible to increase the amount of heat that is discharged from the heat shielding dummy panel  32  toward the outside of the cryopump  10 . At the same time, the amount of heat that goes from the heat shielding dummy panel  32  toward the inside of the cryopump  10  and is discharged from the cryopump  10  by the cryocooler  16  is reduced. Therefore, the power consumption of the cryocooler  16  can be reduced. 
     The second-stage cryopanel assembly  20  is provided at the central portion of the internal space  14  of the cryopump  10 . The second-stage cryopanel assembly  20  includes an upper structure  20   a  and a lower structure  20   b . The second-stage cryopanel assembly  20  includes a plurality of adsorption cryopanels  60  arranged in the axial direction. The plurality of adsorption cryopanels  60  are arranged at intervals in the axial direction. 
     The upper structure  20   a  of the second-stage cryopanel assembly  20  includes a plurality of upper cryopanels  60   a  and a plurality of heat transfer bodies (also referred to as heat transfer spacers)  62 . The plurality of upper cryopanels  60   a  are disposed between the heat shielding dummy panel  32  and the second cooling stage  24  in the axial direction. The plurality of heat transfer bodies  62  are arranged in a columnar shape in the axial direction. The plurality of upper cryopanels  60   a  and the plurality of heat transfer bodies  62  are alternately stacked in the axial direction between the intake port  12  and the second cooling stage  24 . The centers of the upper cryopanel  60   a  and the heat transfer body  62  are located together on the central axis C. In this way, the upper structure  20   a  is disposed above the second cooling stage  24  in the axial direction. The upper structure  20   a  is fixed to the second cooling stage  24  through a heat transfer block  63  formed of a high heat conductive metal material such as copper (for example, pure copper), and is thermally coupled to the second cooling stage  24 . Therefore, the upper structure  20   a  is cooled to the second cooling temperature. 
     The lower structure  20   b  of the second-stage cryopanel assembly  20  includes a plurality of lower cryopanels  60   b  and a second-stage cryopanel mounting member  64 . The plurality of lower cryopanels  60   b  are disposed between the second cooling stage  24  and the shield bottom portion  38  in the axial direction. The second-stage cryopanel mounting member  64  extends downward in the axial direction from the second cooling stage  24 . The plurality of lower cryopanels  60   b  are mounted to the second cooling stage  24  through the second-stage cryopanel mounting members  64 . In this way, the lower structure  20   b  is thermally coupled to the second cooling stage  24  and is cooled to the second cooling temperature. 
     In the second-stage cryopanel assembly  20 , an adsorption area  66  is formed on at least a part of the surface. The adsorption area  66  is provided, for capturing a non-condensable gas (for example, hydrogen) by adsorption. The adsorption area  66  is formed for example, by bonding an adsorbent (for example, activated carbon) to the surface of the cryopanel. 
     As an example, one or a plurality of upper cryopanels  60   a  that are closest to the heat shielding dummy panel  32  in the axial direction, among the plurality of upper cryopanels  60   a , are flat plates (for example, disk-shaped) and are disposed perpendicular to the central axis C. The remaining upper cryopanels  60   a  have an inverted truncated cone shape, and a circular bottom surface is disposed perpendicular to the central axis C. 
     The upper cryopanel  60   a  closest to the heat shielding dummy panel  32  (that is, the upper cryopanel  60   a  located directly below the heat shielding dummy panel  32  in the axial direction, also referred to as a top cryopanel  61 ), among the upper cryopanels  60   a , has a diameter larger than that of the heat shielding dummy panel  32 . However, the diameter of the top cryopanel  61  may be equal to or smaller than the diameter of the heat shielding dummy panel  32 . The top cryopanel  61  directly faces the heat shielding dummy panel  32 , and no other cryopanel exists between the top cryopanel  61  and the heat shielding dummy panel  32 . 
     The diameters of the plurality of upper cryopanels  60   a  gradually increase toward the lower side in the axial direction. Further, the inverted truncated cone-shaped upper cryopanel  60   a  is disposed in a nested manner. The lower part of the upper cryopanel  60   a  on the higher side enters the inverted truncated conical space in the upper cryopanel  60   a  adjacent thereunder. 
     Each heat transfer body  62  has a columnar shape. The heat transfer body  62  may have a relatively short columnar shape and may have an axial height smaller than the diameter of the heat transfer body  62 . The cryopanel such as the adsorption cryopanel  60  is generally formed of a high heat conductive metal material such as copper (for example, pure copper), and as necessary, the surface thereof is coated with a metal layer such as nickel. In contrast, the heat transfer body  62  may be formed of a material different from that of the cryopanel. The heat transfer body  62  may be formed of a metal material, such as aluminum or an aluminum alloy, for example, having a lower density although it has a lower thermal conductivity than the adsorption cryopanel  60 . In this way, both the thermal conductivity and the reduction in weight of the heat transfer body  62  can be achieved to some extent, which is helpful to reduce the cooling time of the second-stage cryopanel assembly  20 . 
     The lower cryopanel  60   b  is a flat plate, for example, in a disk shape. The lower cryopanel  60   b  has a larger diameter than the upper cryopanel  60   a . However, a cutout portion extending from a portion of the outer periphery to the central portion may be formed in the lower cryopanel  60   b  for mounting the lower cryopanel  60   b  to the second-stage cryopanel mounting member  64 . 
     The specific configuration of the second-stage cryopanel assembly  20  is not limited to the configuration described above. The upper structure  20   a  may have any number of upper cryopanels  60   a . The upper cryopanel  60   a  may have a flat plate shape, a conical shape, or other shapes. Similarly, the lower structure  20   b  may have any number of lower cryopanels  60   b . The lower cryopanel  60   b  may have a flat plate shape, a conical shape, or other shapes. 
     The adsorption area  66  may be formed in a place that is hidden behind the adsorption cryopanel  60  adjacent to the upper side so as not to be seen from the intake port  12 . For example, the adsorption area  66  is formed on the entire lower surface of the adsorption cryopanel  60 . The adsorption area  66  may be formed on the upper surface of the lower cryopanel  60   b . Further, although not shown in  FIG. 1  for the sake of simplification, the adsorption area  66  is also formed on the lower surface (back surface) of the upper cryopanel  60   a . As necessary, the adsorption area  66  may be formed on the upper surface of the upper cryopanel  60   a.    
     In the adsorption area  66 , a large number of activated carbon particles are bonded in an irregular arrangement in a state of being densely arranged on the surface of the adsorption cryopanel  60 . The activated carbon particles are molded, for example, in a columnar shape. The shape of the adsorbent may not be a columnar shape and may be, for example, a spherical shape, another molded shape, or an irregular shape. The arrangement of the adsorbents on the panel may be a regular arrangement or an irregular arrangement. 
     Further, a condensation area for capturing a condensable gas by condensation is formed on at least a part of the surface of the second-stage cryopanel assembly  20 . The condensation area is, for example, a section where the adsorbent is missing on the surface of the cryopanel, and the surface of the cryopanel base material, for example, the metal surface is exposed. The upper surface, the outer peripheral portion of the upper surface, or the outer peripheral portion of the lower surface of the adsorption cryopanel  60  (for example, the upper cryopanel  60   a ) may be a condensation area. 
     Both the upper and lower surfaces of the top cryopanel  61  may be condensation areas. That is, the top cryopanel  61  may not have the adsorption area  66 . In this manner, in the second-stage cryopanel assembly  20 , the cryopanel which does not have the adsorption area  66  may be referred to as a condensation cryopanel. For example, the upper structure  20   a  may be provided with at least one condensation cryopanel (for example, the top cryopanel  61 ). 
     As described above, the second-stage cryopanel assembly  20  has a large number of adsorption cryopanels  60  (that is, the plurality of upper cryopanels  60   a  and lower cryopanels  60   b ), and therefore, it has high pumping performance for a non-condensable gas. For example, the second-stage cryopanel assembly  20  can pumping hydrogen gas at a high pumping speed. 
     Each of the plurality of adsorption cryopanels  60  includes the adsorption area  66  at a portion which is not visible from the outside from the cryopump  10 . Therefore, the second-stage cryopanel assembly  20  is configured such that all or most of the adsorption areas  66  are completely invisible from the outside of the cryopump  10 . The cryopump  10  can also be called an adsorbent non-exposure type cryopump. 
     The cryopump housing  70  is a casing of the cryopump  10 , which accommodates the radiation shield  30 , the second-stage cryopanel assembly  20 , and the cryocooler  16 , and is a vacuum container configured to maintain the vacuum tightness of the internal space  14 . The cryopump housing  70  includes the radiation shield  30  and the cryocooler structure part  21  in a non-contact manner. The cryopump housing  70  is mounted to the room temperature part  26  of the cryocooler  16 . 
     The intake port  12  is defined by a front end of the cryopump housing  70 . The cryopump housing  70  has an intake port flange  72  extending radially outward from the front end thereof. The intake port flange  72  is provided over the entire circumference of the cryopump housing  70 . The cryopump  10  is mounted to a vacuum chamber to be evacuated by using the intake port flange  72 . 
     The operation of the cryopump  10  having the above configuration will be described below. When the cryopump  10  is operated, first, the interior of the vacuum chamber is roughed to about 1 Pa with another appropriate roughing pump before the operation. Thereafter, the cryopump  10  is operated. The first cooling stage  22  and the second cooling stage  24  are respectively cooled to the first cooling temperature and the second cooling temperature by the driving of the cryocooler  16 . Accordingly, the radiation shield  30  and the second-stage cryopanel assembly  20  thermally coupled to these are also respectively cooled to the first cooling temperature and the second cooling temperature. 
     A part of the gas that comes flying from the vacuum chamber toward the cryopump  10  enters the internal space  14  from the intake port  12  (for example, the open area  51  around the heat shielding dummy panel  32 ). The other part of the gas is reflected by the heat shielding dummy panel  32  and does not enter the internal space  14 . 
     As described above, since the heat shielding dummy panel  32  is mounted to the radiation shield  30  through the thermal resistance member  48 , the heat shielding dummy panel  32  is thermally insulated from the radiation shield  30  or is connected to the radiation shield  30  through a high thermal resistance. Therefore, the heat shielding dummy panel  32  is maintained at, for example, room temperature or a temperature higher than 0° C. during the operation of the cryopump  10 . Since the heat shielding dummy panel  32  is not almost or entirely cooled by the cryocooler  16 , almost or all the gas that is in contact with the heat shielding dummy panel  32  does not condense on the heat shielding dummy panel  32 . 
     A gas having a sufficiently low vapor pressure (for example, 10 −8  Pa or less) at the first cooling temperature condenses on the surface of the radiation shield  30 . This gas may be referred to as a type 1 gas. The type 1 gas is, for example, water vapor. In this way, the radiation shield  30  can pump the type 1 gas. A gas in which vapor pressure is not sufficiently low at the first cooling temperature is reflected by the radiation shield  30 , and a part thereof goes to the second-stage cryopanel assembly  20 . 
     The gas that has entered the internal space  14  is cooled by the second-stage cryopanel assembly  20 . The type 1 gas reflected by the radiation shield  30  condenses on the surface of the condensation area of the adsorption cryopanel  60 . In addition, a gas having a sufficiently low vapor pressure (for example, 10 −8  Pa or less) at the second cooling temperature condenses on the surface of the condensation area of the adsorption cryopanel  60 . This gas may be referred to as a type 2 gas. The type 2 gas is, for example, nitrogen (N 2 ) or argon (Ar). In this way, the second-stage cryopanel assembly  20  can pump the type 2 gas. 
     A gas in which vapor pressure is not sufficiently low at the second cooling temperature is adsorbed by the adsorption area  66  of the adsorption cryopanel  60 . This gas may be referred to as a type 3 gas. The type 3 gas is, for example, hydrogen (H 2 ). In this way, the second-stage cryopanel assembly  20  can pump the type 3 gas. Therefore, the cryopump  10  can pump various gases by condensation or adsorption and can make the degree of vacuum of the vacuum chamber reach a desired level. 
     According to the cryopump  10  of the embodiment, the heat shielding dummy panel  32  is disposed at the intake port  12 . The heat shielding dummy panel  32  is mounted to the radiation shield  30  through the thermal resistance member  48  such that the dummy panel temperature becomes higher than the shield cooling temperature. In this way, the heat shielding dummy panel  32  can provide a function of protecting the second-stage cryopanel assembly  20  from a radiant heat. Unlike a typical cryopump in which a cryopanel that is disposed at an intake port is essential, the cryopump  10  has a new and alternative design. 
     The thermal resistance member  48  is formed of a material having a lower thermal conductivity than the material of the radiation shield  30 , or a heat insulating material. In this way, it is easy to connect the heat shielding dummy panel  32  to the radiation shield  30  through a high thermal resistance, or to thermally insulate the heat shielding dummy panel  32  from the radiation shield  30 . As a result, it is possible to make the dummy panel temperature significantly higher than the shield cooling temperature. 
     Further, by making the emissivity of the dummy panel outer surface  32   c  higher than the emissivity of the dummy panel inner surface  32   d , it is possible to increase the amount of heat that is discharged from the heat shielding dummy panel  32  toward the outside of the cryopump  10 . At the same time, it is possible to reduce the amount of heat that goes from the heat shielding dummy panel  32  toward the inside of the cryopump  10 . 
     The dummy panel temperature exceeds 0° C. Therefore, it is guaranteed that the heat shielding dummy panel  32  does not provide the pumping capacity for the type 1 gas. It is avoided that an ice layer due to the condensation of water covers the surface (for example, the dummy panel outer surface  32   c ) of the heat shielding dummy panel  32 . 
     Therefore, it is possible to suppress an increase in reflectance (a decrease in emissivity) that may occur due to the formation of an ice layer, during the operation of the cryopump  10 . 
     Since the heat shielding dummy panel  32  does not need to be cooled, it does not need to be formed of a high thermal conductivity metal such as pure copper as in a cryopanel that is disposed at an intake port in a cryopump of the related art. Further, plating treatment of nickel or the like is also not required. In addition, for the same reason, the heat shielding dummy panel  32  may be thinner than the cryopanel. Therefore, the heat shielding dummy panel  32  can be manufactured by a common processing method using an easily available material such as stainless steel, for example, and is inexpensive. 
     Further, since the heat shielding dummy panel  32  does not need to be cooled, the power consumption of the cryocooler  16  can be reduced. 
     In the embodiment described above, the heat shielding dummy panel  32  is mounted to the radiation shield  30  through the thermal resistance member  48 . However, the heat shielding dummy panel  32  may be thermally coupled to the cryopump housing  70  such that the dummy panel temperature becomes higher than the shield cooling temperature. Such an embodiment will be described below. 
       FIG. 3  schematically shows a cryopump  10  according to another embodiment. As shown in the drawing, the heat shielding dummy panel  32  that is disposed at the intake port  12  is mounted to the intake port flange  72 . The heat shielding dummy panel  32  has the dummy panel central portion  32   a  disposed at the central portion of the intake port  12 , and the dummy panel mounting portion  32   b  extending radially outward from the dummy panel central portion  32   a , as in the embodiment shown in  FIGS. 1 and 2 . The dummy panel mounting portion  32   b  is fixed to the inner periphery of the intake port flange  72  by, for example, a fastening member such as a bolt or other appropriate method. 
     In this way, the heat shielding dummy panel  32  is directly mounted to the cryopump housing  70  and is thermally coupled to the cryopump housing  70 . Therefore, the heat shielding dummy panel  32  has a dummy panel temperature higher than the shield cooling temperature during the operation of the cryopump  10 . Therefore, the heat shielding dummy panel  32  can provide a function of protecting the second-stage cryopanel assembly  20  from a radiant heat. 
     Since the heat shielding dummy panel  32  is thermally coupled to the cryopump housing  70 , it can be easily maintained at the dummy panel temperature significantly higher than the shield cooling temperature, for example, a temperature higher than 0° C. (particularly room temperature). Further, since the thermal resistance member  48  as in the embodiment shown in  FIGS. 1 and 2  is not required, it is advantageous in that the mounting structure of the heat shielding dummy panel  32  can be simplified. 
     The heat shielding dummy panel  32  may be mounted to the intake port flange  72  through another member and thermally coupled to the cryopump housing  70 . The heat shielding dummy panel  32  may be mounted to a mating flange to which the intake port flange  72  is mounted, or a center ring that is sandwiched between the intake port flange  72  and the mating flange. Such an embodiment will be described below. 
       FIG. 4  is a schematic perspective view of a cryopump  10  according to still another embodiment.  FIG. 5  is a partial sectional view schematically showing a portion of the cryopump  10  shown in  FIG. 4 .  FIG. 5  shows a part of the cross section of the cryopump  10  in a plane which includes the central axis of the cryopump, as in  FIG. 1 , and shows the heat shielding dummy panel  32  disposed at the intake port  12  and members around it. 
     In the embodiment shown in  FIGS. 4 and 5 , the heat shielding dummy panel  32  is mounted to a mating flange  74  to which the intake port flange  72  is mounted. The mating flange  74  may be, for example, a vacuum flange of a gate valve to which the cryopump  10  is mounted. The mating flange  74  may be a vacuum flange of the vacuum chamber to which the cryopump  10  is mounted. A center ring  76  is provided between the intake port flange  72  and the mating flange  74 . As is known, when the intake port flange  72  is mounted to the mating flange  74 , the center ring  76  is sandwiched between the intake port flange  72  and the mating flange  74 . 
     The heat shielding dummy panel  32  is mounted to the intake port flange  72  through the mating flange  74  and is thermally coupled to the cryopump housing  70 . Even in this way, the heat shielding dummy panel  32  has a dummy panel temperature, for example, room temperature, higher than the shield cooling temperature during the operation of the cryopump  10 . Therefore, similar to the embodiments described above, the heat shielding dummy panel  32  can provide a function of protecting the second-stage cryopanel assembly  20  from a radiant heat. 
       FIG. 6  is a schematic perspective view of a cryopump  10  according to still yet another embodiment.  FIG. 7  is a partial sectional view schematically showing a portion of the cryopump shown in  FIG. 6 .  FIG. 7  shows a part of the cross section of the cryopump  10  in a plane which includes the central axis of the cryopump, as in  FIG. 1 , and shows the heat shielding dummy panel  32  disposed at the intake port  12  and members around it. 
     In the embodiment shown in  FIGS. 6 and 7 , the heat shielding dummy panel  32  is mounted to the center ring  76 . When the intake port flange  72  is mounted to the mating flange  74 , the center ring  76  is sandwiched between the intake port flange  72  and the mating flange  74 . 
     The heat shielding dummy panel  32  is mounted to the intake port flange  72  through the center ring  76  and is thermally coupled to the cryopump housing  70 . Even in this way, the heat shielding dummy panel  32  has a dummy panel temperature, for example, room temperature, higher than the shield cooling temperature during the operation of the cryopump  10 . Therefore, similar to the embodiments described above, the heat shielding dummy panel  32  can provide a function of protecting the second-stage cryopanel assembly  20  from a radiant heat. 
     In the embodiments described with reference to  FIGS. 4 to 7 , the heat shielding dummy panel  32  can be regarded as configuring a part of the cryopump  10 . The mating flange  74  to which the heat shielding dummy panel  32  is mounted, or a vacuum device such as a gate valve having the mating flange  74 , or the center ring  76  may be provided to a user by a cryopump manufacturer as an accessory of the cryopump  10 . 
     Even in the embodiment in which the heat shielding dummy panel  32  is thermally coupled to the cryopump housing  70 , the emissivity of the dummy panel outer surface may be higher than the emissivity of the dummy panel inner surface. 
     The present invention has been described above based on the examples. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, various design changes can be made, various modification examples can be made, and such modification examples are also within the scope of the present invention. 
     In the embodiments described above, the dummy panel temperature is maintained so as to exceed 0° C. during the operation of the cryopump  10 , so that the heat shielding dummy panel  32  does not provide the pumping capacity for the type 1 gas. However, in a certain embodiment, the heat shielding dummy panel  32  may be cooled to a dummy panel temperature that is higher than the shield cooling temperature and lower than the condensation temperature of the type 1 gas (for example, water vapor). In this way, the heat shielding dummy panel  32  may have a certain degree of pumping capacity for the type 1 gas, although it is not so much as a first-stage cryopanel which is disposed at an intake port in a cryopump of the related art. 
     In the embodiments described above, the heat shielding dummy panel  32  is formed in a disk shape from a single plate. However, the heat shielding dummy panel  32  may have other shapes. For example, the heat shielding dummy panel  32  may be, for example, a plate having a rectangular shape or other shapes. Alternatively, the heat shielding dummy panel  32  may be a louver or a chevron formed in a concentric circle shape or a grid shape. 
     In the above description, the horizontal cryopump has been exemplified. However, the present invention is also applicable to other vertical cryopumps. The vertical cryopump refers to a cryopump in which the cryocooler  16  is disposed along the central axis C of the cryopump  10 . Further, the internal configuration of the cryopump, such as the arrangement, the shape, the number, or the like of a cryopanel, is not limited to the specific embodiment described above. Various known configurations can be appropriately adopted. 
     The present invention can be used in the field of cryopumps. 
     It should be understood that the invention is not limited to the above-described embodiment, but may be modified into various forms on the basis of the spirit of the invention. Additionally, the modifications are included in the scope of the invention.