Abstract:
Provided is an ultra-high vacuum forming device containing an ion pump having a compact size in the central axis direction. The ultra-high vacuum forming device ( 1 ) is provided with at least one ion pump ( 100 ). The ion pump ( 100 ) is provided with: a casing ( 110 ) having at least one opening ( 111, 112 ); a board-shaped electrode group ( 120 ) formed by means of a central opening ( 120   a ) being formed along a predetermined central axis (C) disposed within the casing ( 110 ), and a plurality of electrodes ( 121 ) being joined with spaces therebetween; a pair of board-shaped electrodes ( 131, 132 ) having a different polarity than that of the electrode group ( 120 ) and that are disposed at positions sandwiching both sides of the electrode group ( 120 ) within the casing ( 110 ); and a pair of board-shaped magnets ( 141, 142 ) disposed at positions sandwiching both sides of the pair of board-shaped electrodes ( 131, 132 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an ultra-high vacuum creating device. To be specific, the ultra-high vacuum creating device of the present invention includes at least one ion pump. In addition, the ultra-high vacuum creating device of the present invention is configured to include another ion pump, a heating and non-evaporating getter pump and a sublimation pump arbitrarily stacked on the ion pump according to an application, and accordingly, an exhaust characteristic thereof can be optimized according to the application. 
       BACKGROUND ART 
       [0002]    Recently, an ultra-high vacuum technique has been regarded as important along with remarkable development of a nanotechnology and an ultra-precision measurement technique. For example, a surface of a semiconductor is easily contaminated by gas molecules, and conventionally, there has been a need of maintaining the semiconductor in an ultra-high vacuum state under 10 −5  Pa or lower to keep the clean semiconductor surface. In addition, a field emission type charged particle source is used in a charged particle beam device, for example, which uses a finely focused electron beam or an ion source such as a scanning electron microscope in order to improve resolution. At this time, it is necessary to maintain an internal space of the charged particle source in the ultra-high vacuum state in order to stably operate this field emission type charged particle source. Thus, conventionally, an ultra-high vacuum pump such as an ion pump has been used as a device configured for the formation of the ultra-high vacuum state. 
         [0003]    In this manner, the ultra-high vacuum environment under 10 −5  Pa or lower, particularly, a class of 10 −9  Pa to 10 −7  Pa provides ultimate cleanness and stability, and thus, is indispensable for nanoscale ultra-precision machining, ultra-precision measurement, and the like. Conventionally, however, it has been considered that an exhaust device such as a bulky ion pump and a cryopump is necessary for creation and maintenance of such ultra-high vacuum environment. In this manner, the exhaust device has a large-scale structure, a chamber housing the device becomes bulky, and as a result, there is a problem that the entire device scale becomes unnecessarily larger and heavier. 
         [0004]    Thus, a light, small and highly efficient ion pump having uniaxially symmetric electrode arrangement has been developed (Patent Literature 1) in order to solve the above-described problem and a cylindrical ion pump with a larger exhaust amount has been developed (Patent Literature 2) as an evolved type thereof. In particular, the ion pump described in Patent Literature 2 is the cylindrical ion pump in which a space with little electromagnetic field modulation, configured to store a sample and a charged particle source, is secured at the center thereof, and a pump element (a permanent magnet or the like) is arranged in the form of being stuck to a casing surface of an ultra-high vacuum chamber. Thus, it is revolutionary in terms that it is possible to realize high exhaust performance and space efficiency at the same time. 
       CITATION LIST 
     Patent Literature 
       [0005]    Patent Literature 1: Japanese Patent No. 4831549 
         [0006]    Patent Literature 2: Japanese Patent No. 4835756 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0007]    Meanwhile, the overall shape of the cylindrical ion pump disclosed in Patent Literature 2 is formed in a shape which is long in the central-axis direction and short in the direction orthogonal to the central axis (for example, a shape like a clay pipe) in order to secure the high exhaust performance. However, there is a case where it is difficult to sufficiently secure a space for mounting of the ion pump which is long in the central-axis direction depending on a shape of the vacuum chamber as a mounting target, and there is a problem that it is difficult to mount the ion pump to a desired vacuum chamber in such a case. In particular, an electron microscope is configured by scrupulously calculating each relative arrangement of parts forming an electron gun, and thus, in the current status, a space for mounting an ion pump is hardly provided in the central-axis direction of the ion pump in the case of mounting the conventional cylindrical ion pump in a lens barrel of the electron microscope or the like. 
         [0008]    Thus, currently, there is a demand for an ultra-high vacuum creating device which includes an ion pump whose size in the central-axis direction is further reduced while maintaining basic performances of the conventional cylindrical ion pump such as light weight, efficiency, and an exhaust property. 
       Solution to Problem 
       [0009]    Thus, the inventor of the present invention has dedicatedly studied solutions to the conventional problem, and as a result, has invented a configuration in which a plate-shaped electrode group, which has a center opening and is formed by connecting a plurality of electrodes at intervals, and a pair of plate-shaped electrode and a pair of plate-shaped magnet, provided on both upper and lower sides of the electrode group, are arranged inside a casing of an ion pump. According to such a configuration, it has been found out that it is possible to realize the thin ion pump whose size in the central-axis direction is further reduced while maintaining a basic performance such as an exhaust property. Further, the present inventor has conceived that it is possible to solve the problems of the related art based on the above-described finding, and completed the present invention. To be specific, the present invention has the following configurations. 
         [0010]    The present invention relates to an ultra-high vacuum creating device. 
         [0011]    The ultra-high vacuum creating device of the present invention includes at least one ion pump  100 . 
         [0012]    Here, the ion pump  100  includes a casing  110 , a plate-shaped electrode group  120 , a pair of plate-shaped electrodes  131  and  132 , and a pair of plate-shaped magnets  141  and  142 . 
         [0013]    The casing  110  includes at least one of openings  111  and  112 . The plate-shaped electrode group  120  and the pair of plate-shaped electrodes  131  and  132  are at least housed inside the casing  110  such that opposite poles thereof directly oppose therebetween. 
         [0014]    The plate-shaped electrode group  120  is arranged inside the casing  110 . The electrode group  120  has a predetermined central axis (C), and a center opening  120   a  is formed along the central axis (C). In addition, the electrode group  120  has a structure in which electrodes  121  are connected at intervals. In addition, the electrode group  120  may have a structure in which a hollow electrode  123  having a space inside thereof is provided and the electrode  121  is housed inside the hollow electrode  123 . 
         [0015]    The pair of plate-shaped electrodes  131  and  132  is arranged at positions inside the casing  110  such that the electrode group  120  is sandwiched therebetween. That is, the pair of plate-shaped electrodes  131  and  132  is arranged at both sides of the electrode group  120  in the central-axis direction. 
         [0016]    The pair of plate-shaped magnets  141  and  142  is arranged at positions such that the pair of plate-shaped electrodes  131  and  132  is sandwiched therebetween. That is, the pair of plate-shaped magnets  141  and  142  is arranged at both sides of the pair of plate-shaped electrodes  131  and  132  sandwiching the electrode group  120  in the central-axis direction. The pair of plate-shaped magnets  141  and  142  may be arranged inside the casing  110 , but is preferably arranged outside the casing  110 . The pair of plate-shaped magnets  141  and  142  applies a magnetic field in the vertical direction inside the casing  110 , and preferably in a space between the pair of plate-shaped electrodes  131  and  132 . 
         [0017]    As the above-described configuration, the plate-shaped electrode group  120  keeping the space is arranged, and the pair of thin plate-shaped electrodes and the pair of thin plate-shaped magnets are arranged at both sides of the electrode group  120  in the central-axis direction (up-and-down direction). Accordingly, it is possible to reduce the size of the ion pump  100  in the central-axis direction while maintaining the basic performance such as the exhaust property. That is, it is possible to effectively use the internal space of the casing  110  as a gas collecting space by providing the plate-shaped electrode group  120  keeping the space to be sandwiched by the pair of plate-shaped electrodes  131  and  132 , and the pair of plate-shaped magnets  141  and  142  from both the upper and lower sides. Further, the ion pump  100  maintains the exhaust performance or the likes by widening a horizontal width of the plate-shaped electrode group  120 , and further, includes the thin plate-shaped electrodes  131  and  132 , and the plate-shaped magnets  141  and  142  arranged at both the upper and lower sides of the electrode group  120 . Thus, it is possible to reduce the length (that is, thickness) of the ion pump  100  in the central-axis direction while maintaining the exhaust performance of the ion pump  100 . For example, it is possible to set the length of the ion pump  100  in the central-axis direction to be about ¼ of a length of the conventional ion pump according to the configuration of the present invention. Therefore, it is possible to mount the high-performance ion pump  100  (ultra-high vacuum creating device) without changing the basic shape or arrangement thereof even in the case of the electron microscope which has a limit regarding a mounting space, for example. 
         [0018]    In the ultra-high vacuum creating device of the present invention, at least one of the openings  111  and  112  is preferably formed on the central axis (C) in the casing  110  of the ion pump  100 . 
         [0019]    In addition, center openings  133  and  134  are preferably formed on the central axis (C) in the pair of plate-shaped electrodes  131  and  132 , respectively. 
         [0020]    Further, center openings  143  and  144  are preferably formed on the central axis (C) in the pair of plate-shaped magnets  141  and  142 , respectively. 
         [0021]    Accordingly, a gas flow path or a space configured to house experimental equipment or cause the experimental equipment to pass therethrough is formed along the central axis (C) in the ultra-high vacuum creating device of the present invention. 
         [0022]    As the above-described configuration, it is possible to secure the space to house the experimental equipment or cause the experimental equipment to pass therethrough by forming the columnar space along the central axis (C) of the electrode group  120 . In addition, it is possible to secure a wide discharge space by, for example, forming the electrode group  120  using the plurality of ring-shaped electrodes  121  to share each central axis of the pair of plate-shaped electrodes  131  and  132  and the pair of plate-shaped magnets  141  and  142 . 
         [0023]    Further, it is possible to stack a plurality of the ion pumps  100 , configured as described above by causing the openings  111  and  112  to communicate with each other. When the plurality of ion pumps  100  are stacked, the performance and service life thereof can be improved. Therefore, it is possible to mount the ultra-high vacuum creating device having the optimal configuration in terms of the device scale and the performance by adjusting the number of the ion pumps  100  to be stacked in accordance with tolerance of the mounting space. In this manner, the ultra-high vacuum creating device of the present invention has multi-stage extensibility in the central-axis direction. That is, the ultra-high vacuum creating device according to the present invention is capable of stacking the plurality of ion pumps  100  in any stages as long as the space allows it. 
         [0024]    In the ultra-high vacuum creating device of the present invention, two or more of the ion pump  100  may be stacked along the central-axis (C) direction. In this case, it is preferable that the neighboring ion pumps  100  share one of the pair of plate-shaped magnets  141  and  142 . That is, the shared plate-shaped magnet functions so as to apply the magnetic field to both the two neighboring ion pumps  100 . 
         [0025]    As the above-described configuration, it is possible to further reduce the size in the central-axis direction by causing one of the plate-shaped magnets  141  and  142  to be shared in the case of stacking the ion pumps  100 , and further, it is possible to reduce the gross weight of the device as compared to the case of simply connecting the ion pumps  100  in series since it is possible to omit one plate-shaped magnet, which is a heavy object, or more. 
         [0026]    The ultra-high vacuum creating device of the present invention may include at least one heating and non-evaporating getter pump  200  in addition to one or plurality of ion pumps  100 . 
         [0027]    The heating and non-evaporating getter pump  200  includes a casing  210 , a heater  220 , and a pair of getter materials  231  and  232 . 
         [0028]    The casing  210  includes at least one of openings  211  and  212 . The heater  220 , and the pair of getter materials  231  and  232  are arranged inside the casing  210 . 
         [0029]    The heater  220  heats the pair of getter materials  231  and  232 . The heater  220  preferably has a plate shape. 
         [0030]    The pair of getter materials  231  and  232  is arranged at positions inside the casing  210  such that the heater  220  is sandwiched therebetween from both the upper and lower sides. The getter materials  231  and  232  are heated in vacuum by a radiant heat from the heater  220  and activated by discharging a gas that has been stored therein, thereby functioning as a pump. 
         [0031]    Further, at least one of openings  211  and  212  of the heating and non-evaporating getter pump  200  communicates with at least one of openings  111  and  112  of the ion pump  100  in the ultra-high vacuum creating device of the present invention. 
         [0032]    As the above-described configuration, the ultra-high vacuum creating device of the present invention can be constructed by combining the ion pump  100  and the heating and non-evaporating getter pump  200 . 
         [0033]    In the ultra-high vacuum creating device of the present invention, at least one of the openings  211  and  212  is preferably formed on the central axis (C) in the casing  210  of the heating and non-evaporating getter pump  200 . 
         [0034]    In addition, a center opening  221  is preferably formed on the central axis (C) in the heater  220 . 
         [0035]    Further, center openings  233  and  234  are preferably formed on the central axis (C) in the pair of getter materials  231  and  232 , respectively. 
         [0036]    Accordingly, a gas flow path and a space configured to house experimental equipment or cause the experimental equipment to pass therethrough is formed along the central axis (C) in the ultra-high vacuum creating device which is configured to include the ion pump  100  and the heating and non-evaporating getter pump  200 . 
         [0037]    As the above-described configuration, it is possible to secure the space configured to house the experimental equipment or cause the experimental equipment to pass therethrough by forming the columnar space along the central axis (C) at the time of combining the ion pump  100  and the heating and non-evaporating getter pump  200 . Thus, it is possible to efficiently use the ion pump  100  and the heating and non-evaporating getter pump  200  in combination according to the ultra-high vacuum creating device of the present invention. 
         [0038]    The ultra-high vacuum creating device of the present invention may include a sublimation pump  300  in addition to one or plurality of ion pumps  100 . 
         [0039]    The sublimation pump  300  includes a casing  310 , a sublimation filament  320 , and a shield  330 . 
         [0040]    The casing  310  includes at least one of openings  311  and  312 . The sublimation filament  320  is arranged inside the casing  310 . 
         [0041]    The sublimation filament  320  is a ring-shaped filament member which is sublimated when current flows. 
         [0042]    Further, at least one of openings  311  and  312  of the sublimation pump  300  communicates with at least one of openings  111  and  112  of the ion pump  100  in the ultra-high vacuum creating device of the present invention. 
         [0043]    As the above-described configuration, the ultra-high vacuum creating device of the present invention can be constructed by combining the ion pump  100  and the sublimation pump  300 . 
         [0044]    In the ultra-high vacuum creating device of the present invention, at least one of openings  311  and  312  is preferably formed on the central axis (C) in the casing  310  of the sublimation pump  300 . Accordingly, a gas flow path or a space configured to house experimental equipment or cause the experimental equipment to pass therethrough is formed along the central axis (C) in the ultra-high vacuum creating device which is configured to include the ion pump  100  and the sublimation pump  300 . 
         [0045]    As the above-described configuration, it is possible to secure the space configured to house the experimental equipment or cause the experimental equipment to pass therethrough by forming the columnar space along the central axis (C) at the time of combining the ion pump  100  and the sublimation pump  300 . Thus, various characteristics of the ion pump  100  and the sublimation pump  300  are effectively combined according to the ultra-high vacuum creating device of the present invention, and thus, can be used as an efficient pump system. 
       Advantageous Effects of Invention 
       [0046]    According to the present invention, it is possible to provide the ultra-high vacuum creating device which includes the ion pump whose size in the central-axis direction is further reduced while maintaining the basic performances of the conventional ion pump such as the light weight, the efficiency, and the exhaust property. 
         [0047]    The ion pump  100  has a thin shape (preferably, a disc shape) in the present invention, and accordingly, can also be mounted in, for example, a vacuum chamber with few margin in the mounting space such as the lens barrel of the electron gun. In addition, it is also possible to mount the heating and non-evaporating getter pump  200  having an excellent gettering performance of hydrogen in an ultra-high vacuum space and the sublimation pump  300  having an excellent gettering performance in a low vacuum space as well as the ion pump  100  combinedly in the vacuum chamber with a margin in the mounting space. When a plurality of pump units are connected in tandem with each other in this manner, the exhaust amount and exhaust characteristics thereof can be enhanced and adjusted if necessary. Accordingly, the ultra-high vacuum creating device of the present invention has, for example, a start-up vacuum level of 10 −4  Pa to 10 −3  Pa and can improve an ultimate vacuum level up to 10 −9  Pa to 10 −8  Pa. 
         [0048]    The ultra-high vacuum creating device of the present invention can be suitably applied to, for example, an ion beam processing device in which large gases are released from a sample, various processing devices, an ionized gas generation device, an ion source generation device, and the like. In addition, the ultra-high vacuum creating device of the present invention can also be suitably applied to, for example, a synchrotron radiation facility which requires more stable ultra-high vacuum environment, an ion trap, an atomic clock, and the like. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0049]      FIG. 1  is a cross-sectional view illustrating a configuration example of an ion pump. 
           [0050]      FIG. 2  is an exploded view illustrating the configuration example of the ion pump. 
           [0051]      FIGS. 3( a ) and 3( b )  are other examples of a structure of an electrode group. 
           [0052]      FIG. 4  illustrates concept of a closed magnetic circuit formed in the ion pump. 
           [0053]      FIGS. 5( a ) to 5( c )  illustrate examples of a method of supplying a voltage to an electrode of the ion pump. 
           [0054]      FIG. 6  is a cross-sectional view illustrating a configuration example of ion pumps stacked in two stages. 
           [0055]      FIG. 7  is an exploded view illustrating the configuration example of the ion pumps stacked in two stages. 
           [0056]      FIG. 8  is a cross-sectional view illustrating a configuration example of ion pumps stacked in three stages. 
           [0057]      FIG. 9  is a cross-sectional view illustrating a configuration example of ion pumps stacked in four stages. 
           [0058]      FIG. 10  is a cross-sectional view illustrating a configuration example of a heating and non-evaporating getter pump. 
           [0059]      FIG. 11  is an exploded view illustrating the configuration example of the heating and non-evaporating getter pump. 
           [0060]      FIG. 12  is a cross-sectional view illustrating a state in which the ion pump and the heating and non-evaporating getter pump are stacked. 
           [0061]      FIG. 13  is a cross-sectional view illustrating a state in which a one-stage ion pump and a two-stage heating and non-evaporating getter pump are stacked. 
           [0062]      FIG. 14  is a cross-sectional view illustrating a state in which a two-stage ion pump and a one-stage heating and non-evaporating getter pump are stacked. 
           [0063]      FIG. 15  is a cross-sectional view illustrating a configuration example of heating and non-evaporating getter pumps stacked in two stages. 
           [0064]      FIG. 16  is an exploded view illustrating the configuration example of the heating and non-evaporating getter pumps stacked in two stages. 
           [0065]      FIG. 17  is a cross-sectional view illustrating a configuration example of heating and non-evaporating getter pumps stacked in three stages. 
           [0066]      FIG. 18  is a cross-sectional view illustrating a configuration example of a sublimation pump. 
           [0067]      FIG. 19  is an exploded view illustrating the configuration example of the sublimation pump. 
           [0068]      FIG. 20  is a cross-sectional view illustrating a state in which the ion pump, the heating and non-evaporating getter pump, and the sublimation pump are stacked. 
           [0069]      FIG. 21  is a cross-sectional view illustrating another form of the electrode group. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0070]    Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described below, but includes amendments thereto made appropriately by those skilled in the art to the extent obvious. 
         [0071]    In the specification of the present application, a “plate shape” means a shape formed to have the width longer than the thickness. The plate shapes include not only a disk shape but also a polygonal plate shape such as a square plate shape. 
         [0072]    In the specification of the present application, a “ring shape” means a shape formed to have an opening at the center thereof. The ring shapes include not only a circular ring shape but also a polygonal ring shape such as a square ring shape. 
         [0073]    [1. Ion Pump] 
         [0074]    An ultra-high vacuum creating device  1  according to the present invention is configured to include an ion pump  100 .  FIGS. 1 to 9  illustrate configuration examples of the ion pump  100  included in the present invention. 
         [0075]    An operation principle of an ion pump is well-known. The operation principle of the ion pump will be briefly described. First, a voltage of several kV is applied between a titanium negative electrode (cathode) and a positive electrode (anode) of the ion pump, primary electrons are released from the titanium negative electrode. The primary electrons released from the titanium negative electrode are affected by a magnetic field applied from a magnet while being attracted to the positive electrode, and thus, the primary electrons reach the positive electrode by whirling round in a long spiral motion. On the way to the positive electrode, the primary electrons collide against neutral gas molecules to generate many positive ions and secondary electrons. The positive ions are accelerated toward the titanium negative electrode by a high voltage, thereby sputtering titanium atoms. The sputtered titanium atoms adhere to the positive electrode or the like to adsorb the gas molecules (getter effect). Incidentally, the secondary electrons further perform a spiral motion and collide against the gas molecules to generate more positive ions and electrons (tertiary electrons). Accordingly, the gas molecules inside a certain space are collected in the ion pump, and the space can be set to the ultra-high vacuum state of 10 −5  Pa or lower. 
         [0076]      FIG. 1  illustrates the configuration example of the ion pump  100 .  FIG. 1  illustrates a cross-sectional view when the ion pump is seen in a plan view, and a cross-sectional view when the ion pump is seen in a side view. In addition,  FIG. 2  illustrates an exploded view of the ion pump  100 . As illustrated in  FIGS. 1 and 2 , the ion pump  100  is configured to include a casing  110 , an electrode group  120 , a pair of plate-shaped electrodes  131  and  132 , a pair of plate-shaped magnets  141  and  142 , and a magnetic shield  150 . In addition, the magnetic shield  150  minimizes a leakage magnetic field to the outside, and further, forms a closed magnetic circuit together with the plate-shaped magnets  141  and  142 . In the present embodiment, the casing  110 , and the pair of plate-shaped magnets  141  and  142  are arranged inside the magnetic shield  150 . In addition, the electrode group  120 , and the pair of plate-shaped electrodes  131  and  132  are arranged inside the casing  110 . In addition, external connection flanges  114  and  116  formed in the casing  110  protrude outside the magnetic shield  150 . The ion pump  100  is connected to another external device via the external connection flanges  114  and  116 . The external device to which the ion pump  100  is connected is, for example, a vacuum chamber, a sample chamber, or the like which is a target to be turned into a vacuum state. In addition, the external device may be another vacuum pump (an ion pump, a heating and non-evaporating getter pump, a sublimation pump, and the like). 
         [0077]    [1-1. Casing] 
         [0078]    The casing  110  is a frame which forms a workspace configured to collect gas molecules or to house a sample and experimental equipment or causing the sample and the experimental equipment to pass therethrough. As illustrated in  FIG. 1 , the electrode group  120  and the pair of plate-shaped electrodes  131  and  132  are arranged inside the casing  110 . In the present invention, a main body portion to form a space in which the electrode group  120 , and the pair of plate-shaped electrodes  131  and  132  are arranged in the casing  110  preferably has a thin disk shape. That is, the main body portion of the casing  110  is preferably a shape which is formed to have a length (width) in a direction (hereinafter, referred to also as the “orthogonal direction”) orthogonal to the central-axis direction that is longer than a length (thickness) in the central-axis (C) direction. In this manner, it is possible to reduce the overall size of the ion pump  100  in the central-axis direction by forming the main body portion of the casing  110  in the thin disk shape. 
         [0079]    A space formed in the periphery of the central axis of the casing  110  serves not only as a gas flow path in an exhaust operation but also as the space configured to house the sample and the experimental equipment or to cause the sample and the experimental equipment to pass therethrough. The casing  110  includes at least one opening ( 111  or  112 ). A gas flows inside or outside the casing  110  via the opening ( 111  or  112 ). In the embodiment illustrated in  FIG. 1 , the casing  110  includes the two openings  111  and  112 . However, the casing  110  does not necessarily include two openings, and one opening thereof may be occluded. In the specification of the present application, the two upper and lower openings  111  and  112  are formed in the casing  110  in order to describe the ion pump  100  which is extensible in multiple stages in the up-and-down direction. 
         [0080]    As illustrated in  FIG. 1 , the casing  110  is configured of an upper casing member  113  and a lower casing member  115 . That is, when the upper casing member  113  and the lower casing member  115  are bonded to each other, a space configured to house the electrode group  120  and the pair of plate-shaped electrodes  131  and  132  is formed. Incidentally, when the upper casing member  113  and the lower casing member  115  are bonded to each other, flange portions formed in the respective casing members  113  and  115  can be butted and bonded to each other. 
         [0081]    In addition, the upper casing member  113  includes the upper external connection flange  114 , the lower casing member  115  includes the lower external connection flange  116 . Further, the upper opening  111  is formed in the upper external connection flange  114 , and the lower opening  112  is formed in the lower external connection flange  116 . Accordingly, it is possible to connect an external device to both upper and lower sides of the ion pump  100  via the external connection flanges  114  and  116 . 
         [0082]    In addition, as illustrated in  FIG. 1 , both the upper opening  111  and the lower opening  112  are formed on the central axis (C) in the casing  110  as illustrated in  FIG. 1 . Accordingly, the upper external connection flange  114  and the lower external connection flange  116  are also formed on the central axis (C). Accordingly, the flow path passing from the upper opening  111  through the lower opening  112  is linearly formed in the casing  110 . 
         [0083]    Incidentally, a known material such as aluminum, titanium and stainless is used as a material of the casing  110 . In addition, the casing  110  can also cause an inner wall of the casing  110  to directly function as an electrode. In this regard, the casing  110  is preferably made of aluminum with titanium vapor-deposited on the inner wall surface thereof. In this manner, it is possible to decrease the weight of the ion pump system, and further, it is possible to simplify and downsize the structure of the ion pump  100 . In addition, a wiring (not illustrated) or the like, configured to drive an electrode, may be provided inside the casing  110 . 
         [0084]    [1-2. Electrode Group] 
         [0085]    The electrode group  120  is a plurality of electrodes arranged inside the casing  110 . A polarity of the electrode group  120  may be positive or negative as long as it is different from each polarity of the pair of plate-shaped electrodes  131  and  132  to be described later. In addition, the electrode group  120  may be configured such that the polarity thereof can be changed. However, the polarity of the electrode group  120  is preferably positive in the configuration of the ion pump  100  according to the present embodiment. 
         [0086]    As illustrated in  FIG. 1 , the electrode group  120  is configured to include electrodes  121  connected at intervals. For example, the electrode group  120  may be formed by connecting the plurality of electrodes  121  at intervals, or the electrode group  120  may be formed by forming a plurality of holes in one electrode. Accordingly, the electrode group  120  keeping the space is formed. In the example illustrated in  FIG. 1 , each of the plurality of electrodes  121  forming the electrode group  120  is formed in a ring shape. In particular, the electrode  121  is preferably a circular ring shape (ring shape). However, the electrode  121  may be a triangular ring shape, a square ring shape, or another polygonal ring shape. In addition,  FIGS. 3( a ) and 3( b )  illustrate other examples of the shape of the electrode group  120 . As illustrated in  FIG. 3( a ) , the electrode group  120  may be formed by making the electrode  121  in a spiral shape. In addition, the electrode group  120  may be formed by making the electrode  121  in a honeycomb shape (hexagonal lattice shape) as illustrated in  FIG. 3( b ) . However, the example of the structure of the electrode group  120  is not limited to the drawings, and any shape can be employed as long as the shape keeps the space at the internal portion thereof by connecting the electrodes  121  at intervals. In addition, the electrode group  120  may be configured to include a hollow electrode  123  housing the electrode  121  at an internal portion thereof as will be described later. 
         [0087]    In addition, a center opening  120   a  is formed in the electrode group  120  along the central axis (C) thereof as illustrated in  FIGS. 1, 3 ( a ) and  3 ( b ). Thus, when the electrode group  120  is formed using the plurality of ring-shaped electrodes  121 , the plurality of ring-shaped electrodes  121  are concentrically arranged with the central axis (C) as the center thereof as in the example illustrated in  FIG. 1 . Hereinafter, a description will be given by exemplifying a case in which the electrode group  120  is formed using a plurality of electrodes having the ring shape (hereinafter, referred to as the “ring-shaped electrodes”) as an example of the ion pump according to the present invention. 
         [0088]    As illustrated in  FIGS. 1 and 2 , the electrode group  120  has the shape which is formed such that the length (width) in the orthogonal direction is longer than the length (thickness) in the central-axis (C) direction. That is, the electrode group  120  is formed in a thin type which has a thin thickness. In particular, the electrode group  120  configured of the plurality of ring-shaped electrodes  121  preferably has the length (width) in the orthogonal direction which is longer than 5 or 10 times or more, or is more preferably 5 to 30 times, or most preferably 10 to 25 times of the length (thickness) in the central-axis (C) direction. 
         [0089]    In addition, the plurality of ring-shaped electrodes  121  formed in the circular ring shape are respectively arranged like concentric circles with the central axis (C) as the center thereof. That is, one the ring-shaped electrode  121  is arranged in an opening of another the ring-shaped electrode  121 , and this another the ring-shaped electrode  121  is arranged in an opening of the other the ring-shaped electrode  121 . In this manner, the plurality of ring-shaped electrodes  121  share the central axis. In addition, it is preferable that the intervals among the plurality of ring-shaped electrodes  121  be practically equal intervals. In addition, the number of the ring-shaped electrodes  121  forming the electrode group  120  is not particularly limited, and may be about, for example, 5 to 20 or 8 to 15. 
         [0090]    In addition, the electrode group  120  includes a conducting wire  122  which extends in the direction orthogonal to the central-axis (C) direction in order to connect the plurality of ring-shaped electrodes  121  as illustrated in  FIG. 1 . In the example illustrated in  FIG. 1 , the conducting wire  122  is provided in four places. The conducting wire  122  electrically connects the ring-shaped electrodes  121  forming the electrode group  120  to each other. When the plurality of ring-shaped electrodes  121  are connected via the conducting wire  122  in this manner, the respective the ring-shaped electrodes  121  can be maintained in the same polarity. In addition, it is unnecessary to apply a voltage to each of the ring-shaped electrodes  121  by connecting the plurality of ring-shaped electrodes  121  via the conducting wire  122 . That is, when a voltage is applied to at least one of the ring-shaped electrodes  121 , the voltage is applied to all the ring-shaped electrodes  121  via the conducting wire  122 . In addition, the conducting wire  122  may function as a spacer configured to hold the interval between the respective ring-shaped electrodes  121  to be constant. When the conducting wire  122  is configured to function as the spacer in this manner, it is possible to simplify the configuration inside the electrode group  120 . 
         [0091]    In addition, the number of the ring-shaped electrodes  121  forming the electrode group  120  can be appropriately increased. It is possible to increase the exhaust amount of the ion pump  100  by increasing the number of the ring-shaped electrodes  121 . In addition, when the number of the ring-shaped electrodes  121  is increased, the size of the ion pump  100  in the direction orthogonal to the central-axis direction (the orthogonal direction) is extended, but the size thereof in the central-axis direction does not change. Thus, it is possible to improve the exhaust amount while suppressing the size of the ion pump  100  in the central-axis direction to be small by increasing the number of the ring-shaped electrodes  121  in the configuration of the present invention. In this manner, the exhaust amount of the ion pump  100  can be adjusted by the extensibility in the orthogonal direction. 
         [0092]    A known material can be appropriately used for the ring-shaped electrode  121  forming the electrode group  120 . Examples of the material of the ring-shaped electrode  121  may include titanium, copper, graphite, and copper tungsten. In particular, the ring-shaped electrode  121  is preferably made of titanium when being configured to function as the negative electrode. In addition, the electrode group  120  may be arranged inside the casing  110  via a known fixing unit (not illustrated). For example, a protrusion may be formed in an outermost layer of the electrode group  120  so as to be fit in a groove formed in the casing  110 . 
         [0093]    Further,  FIG. 21  illustrates another form of the electrode group  120 . The electrode group  120  illustrated in  FIG. 21  includes the hollow electrode  123  in addition to the electrode  121 . That is, the electrode group  120  is configured such that the plurality of electrodes  121  connected at intervals are housed inside the hollow electrode  123  which has a space formed at an internal portion thereof. 
         [0094]    To be specific, the hollow electrode  123  includes upper and lower flat surface portions  123   a,  and a side surface portion  123   b  which connects side edges of the upper and lower flat surface portions  123   a  in the vertical direction. The space is secured between the upper and lower flat surface portions  123   a  by the side surface portion  123   b.  In this manner, the hollow electrode  123  is formed in a hollow shape to keep the space at the internal portion thereof. In addition, a center opening  124  is formed along the central axis (C) in the hollow electrode  123 . Further, the electrodes  121  connected at intervals are housed in the internal portion of the hollow electrode  123 , that is, the space between the upper and lower flat surface portions  123   a  as illustrated in  FIG. 21 . Incidentally, the electrode  121  arranged in the internal portion of the hollow electrode  123  may be the ring shape (the circular ring shape, the square ring shape, and the like), the spiral shape, or the honeycomb shape (hexagonal lattice shape) described above. In this manner, the electrode group  120  may have the structure that includes the hollow electrode  123  in addition to the electrode  121 . 
         [0095]    In addition, it is preferable that the electrode  121  and the hollow electrode  123  be electrically connected to each other as illustrated in  FIG. 21 . Accordingly, when a voltage is applied to any one of the electrode  121  and the hollow electrode  123 , it is possible to maintain the polarity of the entire electrode group  120  to be the same. For example, it is preferable that the hollow electrode  123  be electrically connected to the electrode  121  in the side surface portion  123   b.  However, it is also possible to electrically connect the hollow electrode  123  and the electrode  121  via other portions or parts. 
         [0096]    In addition, the center opening  120   a  formed at the center of the electrode group  120  and the center opening  124  formed in the hollow electrode  123  communicate with each other in the vertical direction as illustrated in  FIG. 21 . At this time, the center opening  124  of a middle-penetrating electrode  123  is preferably formed to have a larger opening diameter than the center opening  120   a  of the electrode group  120 . In addition, the shape of the hollow electrode  123  can be appropriately designed in accordance with each shape of the casing  110 , the electrode  121 , the plate-shaped electrodes  131  and  132 , and the like. 
         [0097]    [1-3. Plate-Shaped Electrode] 
         [0098]    The plate-shaped electrodes  131  and  132  are electrodes arranged inside the casing  110  and the electrodes electrically forming a pair with the above-described electrode group  120 . That is, it is necessary to form the plate-shaped electrodes  131  and  132  to have a different polarity from the electrode group  120 . In addition, each polarity of the plate-shaped electrodes  131  and  132  may be appropriately changed according to the polarity of the electrode group  120 . However, each polarity of the plate-shaped electrodes  131  and  132  is preferably negative in the configuration of the ion pump  100  according to the present embodiment. 
         [0099]    As illustrated in  FIG. 1 , at least a pair of the plate-shaped electrodes  131  and  132  is provided such that the electrode group  120  is sandwiched therebetween from both sides in the central-axis direction (up-and-down direction). That is, the one plate-shaped electrode  131  is arranged at the upper side of the electrode group  120 , and the other plate-shaped electrode  132  is arranged at the lower side of the electrode group  120 . Each thickness of the pair of upper and lower plate-shaped electrodes  131  and  132  is extremely thin. In addition, each width (length in the orthogonal direction) of the pair of plate-shaped electrodes  131  and  132  is practically equal to that of the electrode group  120 . That is, the plate-shaped electrodes  131  and  132  are formed to have a horizontal width which enables the electrode group  120  to be entirely covered from the upper and lower sides. In addition, the plate-shaped electrodes  131  and  132  preferably have a disk shape. However, the plate-shaped electrodes  131  and  132  may have a triangular plate shape, a square plate shape, or other polygonal plate shapes. Each shape of the plate-shaped electrodes  131  and  132  may be set in accordance with each shape of the casing  110  and the electrode group  120 . 
         [0100]    As illustrated in  FIG. 2 , the center openings  133  and  134  are formed in the respective central portions of the pair of plate-shaped electrodes  131  and  132 . It is preferable that each size of the center openings  133  and  134  be substantially the same size as a size of the opening of the ring-shaped electrode  121  arranged at the nearest position to the central axis (C) among the plurality of ring-shaped electrodes  121  forming the electrode group  120 . Further, the pair of plate-shaped electrodes  131  and  132  are arranged such that the center openings  133  and  134  are positioned on the central axis (C), respectively, as illustrated in  FIG. 2 . Thus, the center openings  133  and  134  of the pair of plate-shaped electrodes  131  and  132  communicate with the opening of the electrode group  120  along the central axis (C). 
         [0101]    A known material can be appropriately used for the plate-shaped electrodes  131  and  132 . Titanium, copper, graphite, copper tungsten, or the like, which has supplemental performance with respect to residual gases in the vacuum may be appropriately used as the material the plate-shaped electrodes  131  and  132 . In particular, the plate-shaped electrodes  131  and  132  are preferably made of titanium when being configured to function as the negative electrode. In addition, the plate-shaped electrodes  131  and  132  may be formed using a plate for enhancement of electric field application efficiency or punching metal for enhancement of permeability of the residual gas. In addition, the plate-shaped electrodes  131  and  132  may be arranged inside the casing  110  via a known fixing unit (not illustrated). For example, a protrusion may be formed in the plate-shaped electrodes  131  and  132  so as to be fit into a groove formed in the casing  110 . 
         [0102]    [1-4. Plate-Shaped Magnet] 
         [0103]    The pair of plate-shaped magnets  141  and  142  is a magnet that applies a magnetic field inside the casing  110 . Thus, the plate-shaped magnets  141  and  142  are arranged at the positions such that the pair of plate-shaped electrodes  131  and  132  is sandwiched therebetween from both the sides in the up-and-down direction (central-axis direction) as illustrated in  FIG. 1 . That is, the one plate-shaped magnet  141  is arranged above the upper plate-shaped electrode  131 , and the other plate-shaped magnet  142  is arranged below the lower plate-shaped electrode  132 . The plate-shaped magnets  141  and  142  are preferably permanent magnets, but may be configured using an electromagnetic coil as a magnet. In addition, each of the pair of plate-shaped magnets  141  and  142  has different magnetism between one side and the miscellaneous sides, and it is necessary for the plate-shaped magnets  141  and  142  opposing each other to be arranged such that polarities of faces opposing each other are different from each other. 
         [0104]    As illustrated in  FIG. 1 , the pair of plate-shaped magnets  141  and  142  is preferably arranged outside the casing  110 . However, it is also possible to be arranged the pair of plate-shaped magnets  141  and  142  inside the casing  110 . When the plate-shaped magnets  141  and  142  are arranged outside the casing  110 , the upper plate-shaped magnet  141  may be fixed to the upper casing member  113 , and the upper plate-shaped magnet  142  may be fixed to the lower casing member  115 . To be specific, each of the plate-shaped magnets  141  and  142  is preferably arranged between the main body portion (portion forming a housing space of the electrode group  120  or the like) of the casing  110  and each of the external connection flanges  114  and  116 . 
         [0105]    The pair of upper and lower plate-shaped magnets  141  and  142  is formed in a thin type. That is, each of the plate-shaped magnets  141  and  142  has a shape which is formed such that a length (width) in the orthogonal direction is longer than a length (thickness) in the central-axis (C) direction. In addition, each width (length in the orthogonal direction) of the pair of plate-shaped magnets  141  and  142  is practically equal to that of the electrode group  120 . That is, the plate-shaped magnets  141  and  142  are formed to have a horizontal width which enables the electrode group  120  to be entirely covered from the upper and lower sides. In addition, the plate-shaped magnets  141  and  142  preferably have a disk shape. However, the plate-shaped magnets  141  and  142  may have a triangular plate shape, a square plate shape, or other polygonal plate shapes. Each shape of the plate-shaped magnets  141  and  142  may be set in accordance with each shape of the casing  110 , the electrode group  120 , and the plate-shaped electrodes  131  and  132 . 
         [0106]    As illustrated in  FIG. 2 , the center openings  143  and  144  are formed in the respective central portions of the pair of plate-shaped magnets  141  and  142 . It is preferable that each size of the center openings  143  and  144  be substantially the same size as a size of the opening of the ring-shaped electrode  121  arranged at the nearest position to the central axis (C) among the plurality of ring-shaped electrodes  121  forming the electrode group  120 . Further, the pair of plate-shaped magnets  141  and  142  are arranged such that the center openings  143  and  144  are positioned on the central axis (C), respectively, as illustrated in  FIG. 2 . Thus, the center openings  143  and  144  of the pair of plate-shaped magnets  141  and  142  communicate with the opening of the electrode group  120  and the center openings  133  and  134  of the plate-shaped electrodes  131  and  132  along the central axis (C). 
         [0107]    [1-5. Magnetic Shield] 
         [0108]    The magnetic shield  150  is a shield member that houses the casing  110  and the plate-shaped magnets  141  and  142  therein and prevents the magnetism of the plate-shaped electrodes  131  and  132  from leaking to the outside, and works to suppress the magnetic field leakage to the workspace around the central axis and suppress disturbance of a magnetic flux intruding into the electrode group  120  by forming the closed magnetic circuit together with the plate-shaped magnets  141  and  142 . The magnetic shield  150  can be formed using a known material having high magnetic permeability such as mu metal and permalloy. In addition, the magnetic shield  150  is preferably conductive. 
         [0109]    In addition, an opening is formed in a part of the magnetic shield  150  so that the external connection flanges  114  and  116  of the casing  110  protrude through the opening as illustrated in  FIG. 1 . 
         [0110]    Further, the magnetic shield  150  preferably forms the closed magnetic circuit inside the ion pump in cooperation with the pair of plate-shaped magnets  141  and  142 . The concept of the closed magnetic circuit is illustrated in  FIG. 4 . As illustrated in  FIG. 4 , the pair of plate-shaped magnets  141  and  142  each of which has the different magnetism between one side and the miscellaneous sides is used, and further, the plate-shaped magnets  141  and  142  opposing each other are arranged such that polarities of faces opposing each other are different from each other. In the example illustrated in  FIG. 4 , a face of the upper plate-shaped magnet  141  on the electrode group  120  side becomes the S-pole, and the opposite face becomes the N-pole. On the other hand, a face of the lower plate-shaped magnet  142  on the electrode group  120  side becomes the N-pole, and the opposite face becomes the S-pole. Incidentally, each of the upper plate-shaped magnet  141  and the lower plate-shaped magnet  142  may have the polarity opposite to the above-described polarity. In addition, the magnetic shield  150  is formed using a magnetically permeable material having high magnetic permeability. 
         [0111]    With the above-described configuration, the magnetic shield  150  functions as a guide of the magnetic flux surrounding the periphery of the ion pump in cooperation with the pair of plate-shaped magnets  141  and  142 . That is, when the magnetic flux vertically penetrating the ion pump is pulled into the magnetic shield  150 , the closed magnetic circuit is formed. Accordingly, it is possible to align distribution of the magnetic flux intruding into the electrode group  120  and to reduce the leakage of the magnetic field into the space around the central axis. 
         [0112]    The ion pump  100  configured as described above has the size which is small in the central-axis (C) direction as illustrated in  FIG. 1  and the like. That is, the length in the central-axis direction is set to be smaller than the length in the direction orthogonal to the central axis (the orthogonal direction) when the overall outer shape of the ion pump  100  is viewed. To be specific, it is possible to suppress the length of the ion pump  100  of the present invention in the central-axis direction to be about ¼ of that of an ion pump of the related art. 
         [0113]    In addition, the ion pump  100  of the present invention has the small size in the central-axis direction as described above, but basic performances thereof such as the exhaust amount can be maintained as performances which are not changed from the related art. That is, it is possible to sufficiently secure the space to collect the gas by increasing the number of the ring-shaped electrodes  121  forming the electrode group  120  and extending each length (width) of the casing  110 , the plate-shaped electrodes  131  and  132 , and the plate-shaped magnets  141  and  142  in the orthogonal direction in accordance with the increased number. Therefore, the ion pump  100  can obtain the desired exhaust performance while suppressing the size in the central-axis direction. 
         [0114]    [1-6. Voltage Supply Method] 
         [0115]      FIGS. 5( a ) to 5( c )  illustrate examples of modes of connecting a power supply  2  to the ion pump  100  having the above-described configuration. 
         [0116]    For example,  FIG. 5( a )  illustrates an example in which the power supply  2  is connected to the electrode group  120  and a voltage is applied to the electrode group  120 . In this case, it is possible to connect an earth  3  to the casing  110 . Incidentally, the casing  110  is connected to the pair of plate-shaped electrodes  131  and  132 . Thus, the electrode group  120  serves as the positive electrode, and the plate-shaped electrodes  131  and  132  and the casing  110  serve as the negative electrodes in the example illustrated in  FIG. 5( a ) . 
         [0117]    In addition,  FIG. 5( b )  illustrates an example in which the power supply  2  is connected to the pair of plate-shaped electrodes  131  and  132  and a voltage is applied to the plate-shaped electrodes  131  and  132 . In this case, it is possible to connect the earth  3  to the casing  110  and the electrode group  120 . In the example illustrated in  FIG. 5( b ) , the pair of plate-shaped electrodes  131  and  132  serves as the positive electrode, and the casing  110  and the electrode group  120  serves as the negative electrodes. 
         [0118]    In addition,  FIG. 5( c )  illustrates an example in which a positive side of the power supply  2  is connected to one of the electrode group  120  and the plate-shaped electrodes  131  and  132 , and a negative side of the power supply  2  is connected to the other one of the electrode group  120  and the plate-shaped electrodes  131  and  132 . In this case, it is possible to connect the earth  3  to the magnetic shield  150 . In addition, the earth  3  may be connected to the casing  110  although not illustrated. In the example illustrated in  FIG. 5( c ) , one of the electrode group  120  and the plate-shaped electrodes  131  and  132  serve as the positive electrodes, and the other serves as the negative electrode in the direction in which current flows from the power supply  2 . Which one is set as the positive electrode or the negative electrode can be changed by controlling the direction of the current to be supplied from the power supply  2 . Thus, a control device (not illustrated) configured to control the power supply  2  may be provided in the example illustrated in  FIG. 5( c ) . 
         [0119]    [1-7. Multi-Stage Structure of Ion Pump] 
         [0120]    One of the characteristics of the ion pump  100  having the above-described structure is that it is possible to stack the ion pumps  100  in a plurality of stages in the central-axis (C) direction. That is, the ion pump  100  has the extensibility in the central-axis direction. 
         [0121]      FIG. 6  illustrates an example of a structure in which the ion pumps  100  are stacked in two stages. In addition,  FIG. 7  illustrates an exploded view of the structure in which the ion pumps  100  are stacked in two stages. As illustrated in  FIGS. 6 and 7 , the ion pump  100  includes the casing  110 , the electrode group  120 , the pair of plate-shaped electrodes  131  and  132 , and the pair of plate-shaped magnets  141  and  142  as the basic configuration. Incidentally, the magnetic shield  150  is preferably formed in a shape that can cover all the stacked ion pumps  100  when the ion pumps  100  are stacked. 
         [0122]    As illustrated in  FIG. 6 , the two stacked ion pumps  100  share the central axis (C). That is, a columnar space is formed along the single central axis (C) by the two ion pumps  100 . Thus, it is possible to secure the space configured to house the experimental equipment or cause the experimental equipment to pass therethrough. 
         [0123]    To be specific, when the ion pumps  100  are stacked, the casing  110  includes a relay casing member  117  in addition to the upper casing member  113  in which the upper external connection flange  114  is formed and the lower casing member  115  in which the lower external connection flange  116  is formed. The relay casing member  117  is arranged between the upper casing member  113  and the lower casing member  115 . The relay casing member  117  is bonded to the upper casing member  113 , thereby functioning as the casing  110  for the ion pump  100  at the upper stage. At the same time, the relay casing member  117  is bonded to the lower casing member  115 , thereby also functioning as the casing  110  for the ion pump  100  at the lower stage. Incidentally, when the relay casing member  117  is bonded to the upper casing member  113  and the lower casing member  115 , flange portions formed in the respective casing members  113 ,  115  and  117  can be butted and bonded to each other. In this manner, it is possible to make the overall size of the ultra-high vacuum creating device  1  in the central-axis direction compact by providing the relay casing member  117  that can be shared between the upper-stage ion pump  100  and the lower-stage ion pump  100 . 
         [0124]    In addition, a constricted portion  118  that is inwardly constricted is formed in a central portion of the relay casing member  117  in the central-axis direction as illustrated in  FIG. 6  and the like. A plate-shaped magnet  145  ( 141  or  142 ) is arranged in the constricted portion  118  of the relay casing member  117 . 
         [0125]    In addition, when the ion pumps  100  are stacked, the upper-stage ion pump  100  and the lower-stage ion pump  100  can share the plate-shaped magnet  145  ( 141  or  142 ). Originally, the ion pump  100  is provided with the pair of two plate-shaped magnets  141  and  142 . However, when the ion pumps  100  are stacked in a plurality of stages, a single plate-shaped magnet can be used as the lower plate-shaped magnet  142  in the upper-stage ion pump  100  and the upper plate-shaped magnet  141  in the lower-stage ion pump  100 . Thus, three plate-shaped magnets are used to realize the same function as that in the case of arranging four plate-shaped magnets in the example illustrated in  FIG. 6 . In the respective drawings, reference sign  145  represents the plate-shaped magnet shared by the two ion pumps  100 . The shared plate-shaped magnet  145  is configured to provide a magnetic field to both the casing  110  of the upper-stage ion pump  100  and the casing  110  of the lower-stage ion pump  100 . When the plate-shaped magnet  145  is shared in the case of stacking the ion pumps  100  in this manner, it is possible to make the overall size of the ultra-high vacuum creating device  1  in the central-axis direction more compact, and reduce the weight thereof. Incidentally, the shared plate-shaped magnet  145  is arranged in the constricted portion  118  of the relay casing member  117 . 
         [0126]    In addition,  FIG. 8  illustrates a structure in which the ion pumps  100  are stacked in three stages. When the ultra-high vacuum creating device  1  is constructed by stacking the ion pumps  100  in three stages, there are the two relay casing members  117  and the two shared plate-shaped magnets  145 . 
         [0127]    In addition,  FIG. 9  illustrates a structure in which the ion pumps  100  are stacked in four stages. When the ultra-high vacuum creating device  1  is constructed by stacking the ion pumps  100  in four stages, there are the three relay casing members  117  and the three shared plate-shaped magnets  145 . Incidentally, the ultra-high vacuum creating device  1  of the present invention has the size in the central-axis (C) direction that is about ¼ of that of the ion pump of the related art. Thus, when the ion pumps  100  are stacked in four stages, the size of the ultra-high vacuum creating device  1  of the present invention in the central-axis direction is just the same level as the size of the ion pump of the related art. Further, the exhaust performance of the ultra-high vacuum creating device  1  of the present invention is remarkably improved as compared to the ion pump of the related art since the ion pumps  100  are stacked in four stages. 
         [0128]    [2. Heating and Non-Evaporating Getter Pump] 
         [0129]    The ultra-high vacuum creating device  1  according to the present invention may be provided with a heating and non-evaporating getter pump  200  in addition to the ion pump  100 .  FIGS. 10 to 17  illustrate configuration examples of the heating and non-evaporating getter pump  200 . The heating and non-evaporating getter pump  200  is a vacuum pump that performs exhaust by heating a surface of a getter material using radiant heat from a heater in vacuum inside a casing and activating the getter material. The operation principle of the heating and non-evaporating getter pump is that the surface of the getter material such as Ti—V—Fe and an internal portion in which gases are stored are heated in the vacuum to discharge stored and adsorbed gases, and then, a chain reaction relating to gas storage is caused by returning the temperature to room temperature, thereby realizing the function as the pump. 
         [0130]    The ion pump  100  has an advantage that it is possible to collect an inert gas such as nitrogen, helium and argon and rapidly create the ultra-high vacuum, but has a disadvantage that exhaust efficiency regarding hydrogen as a light element molecule is poor. On the other hand, the heating and non-evaporating getter pump  200  has a disadvantage that the absolute exhaust speed and the operation in a low vacuum region are poor, but has a high exhaust performance relating to hydrogen. Thus, it is possible to complement the disadvantages of the pumps one another by combining the ion pump  100  and the heating and non-evaporating getter pump  200  like the ultra-high vacuum creating device  1  of the present invention. Therefore, it is possible to provide the ultra-high vacuum creating device  1  with the favorable usability by combining the ion pump  100  and the heating and non-evaporating getter pump  200 . It is novel to provide such a uniaxially symmetric structure of the heating and non-evaporating getter pump  200  in order for series-connection with another pump. 
         [0131]      FIG. 10  illustrates the configuration example of the heating and non-evaporating getter pump  200 .  FIG. 10  illustrates a cross-sectional view when the heating and non-evaporating getter pump is seen in a plan view, and a cross-sectional view when the heating and non-evaporating getter pump is seen from a side view. In addition,  FIG. 11  illustrates an exploded view of the heating and non-evaporating getter pump  200 . As illustrated in  FIGS. 10 and 11 , the heating and non-evaporating getter pump  200  is configured to include a casing  210 , a heater  220 , a pair of getter materials  231  and  232 , and a heat shield  240 . In the present embodiment, the casing  210  is arranged inside the heat shield  240 . In addition, the heater  220  and the pair of getter materials  231  and  232  are arranged inside the casing  210 . In addition, external connection flanges  214  and  216  formed in the casing  210  protrude outside the heat shield  240 . The heating and non-evaporating getter pump  200  is connected to another external device via the external connection flanges  214  and  216 . The external device to which the heating and non-evaporating getter pump  200  is connected is, for example, a vacuum chamber, a sample chamber, or the like which is a target to be turned into a vacuum state. In addition, the external device may be another vacuum pump (an ion pump, a heating and non-evaporating getter pump, a sublimation pump, and the like). 
         [0132]    [2-1. Casing] 
         [0133]    The casing  210  is a frame which forms a workspace configured to collect gas molecules or to house a sample and experimental equipment or causing the sample and the experimental equipment to pass therethrough. The casing  210  of the heating and non-evaporating getter pump  200  has basically the same structure as the casing  110  of the ion pump  100  described above. Thus, the description for the casing  110  of the ion pump  100  can be appropriately incorporated to the description for the casing  210  of the heating and non-evaporating getter pump  200 . 
         [0134]    That is, the casing  210  of the heating and non-evaporating getter pump  200  includes at least one opening ( 211  or  212 ). In the embodiment illustrated in  FIG. 10 , the casing  210  includes the two openings  211  and  212 . Accordingly, the heating and non-evaporating getter pump  200  is extensible in multi stages in the up-and-down direction. In addition, a space, configured to house the heater  220  and the getter materials  231  and  232 , is formed in the casing  210  by bonding the upper casing member  213  and the lower casing member  215 . In addition, the upper casing member  213  includes the upper external connection flange  214 , the lower casing member  215  includes the lower external connection flange  216 . The upper opening  211  is formed in the upper external connection flange  214 , and the lower opening  212  is formed in the lower external connection flange  216 . Further, both the upper opening  211  and the lower opening  212  are formed on the central axis (C) in the casing  210 . Accordingly, a flow path passing from the upper opening  211  through the lower opening  212  is linearly formed in the casing  210 . A space formed in the periphery of the central axis serves not only as a gas flow path in an exhaust operation but also as the space configured to house the sample and the experimental equipment or to cause the sample and the experimental equipment to pass therethrough. 
         [0135]    [2-2. Heater] 
         [0136]    The heater  220  is a heat generating source configured to heat the getter materials  231  and  232  inside the casing  210 . The heater  220  may be formed using a metallic material that generates heat by electrical heating when power is applied, for example. Thus, the heater  220  is preferably connected to a power supply (not illustrated). The heater  220  is heated to a degree that can cause the getter materials  231  and  232  to be heated by the radiant heat. The heating temperature of the heater  220  is not particularly limited, and for example, is 300 to 600 degree. The heating temperature of the heater  220  may be appropriately adjusted according to each material of the getter materials  231  and  232 , a positional relationship therebetween, and the like. 
         [0137]    As illustrated in  FIG. 10 , the heater  220  has preferably a plate shape. The plate shape indicates a shape whose width is longer than a thickness thereof. The heater  220  has preferably a disk shape, but may have a triangular plate shape a square plate shape, or other polygonal plate shapes. 
         [0138]    In addition, the center opening  221  is formed at the central portion of the heater  220 . A size of the center opening  221  may be set to the same level as the openings  211  and  212  formed in the casing  210 , for example. Further, heater  220  is arranged such that the center opening  221  is positioned on the central axis (C) as illustrated in  FIG. 1 . Thus, the center opening  221  of the heater  220  communicates with the openings  211  and  212  of the casing  210  along the central axis (C). 
         [0139]    [2-3. Getter Material] 
         [0140]    The getter materials  231  and  232  are members each of which are activated when being heated by the heater  220  in the vacuum and causes gas molecules such as hydrogen to be continuously stored through the chain reactions. A known material having a getter effect and a hydrogen storage effect can be used as the getter materials  231  and  232 . For example, the getter materials  231  and  232  may be made of an alloy including, for example, Ti, V, Fe and the like. 
         [0141]    As illustrated in  FIG. 10 , the pair of getter materials  231  and  232  is arranged on both sides of the heater  220  in the central-axis direction (up-and-down direction). That is, one of the getter material  231  is arranged above the heater  220  and the other getter material  231  is arranged below the heater  220 . The pair of getter materials  231  and  232  is formed in a thin type such that a length (width) in the orthogonal direction is longer than a length (thickness) in the central-axis direction. In addition, the getter materials  231  and  232  are preferably formed in a disk shape similarly to the heater  220 . However, the getter materials  231  and  232  may have a triangular plate shape, a square plate shape, or other polygonal plate shapes, but is desirably a structure in which a face opposing the heater has an appropriately uneven structure so as to efficiently repair the radiant heat from the heater. Each shape of the getter materials  231  and  232  may be formed in accordance with each shape of the casing  210  and the heater  220 . 
         [0142]    As illustrated in  FIG. 11 , the center openings  233  and  234  are formed in the respective central portions of the pair of getter materials  231  and  232 . Each size of the center openings  233  and  234  of the getter materials  231  and  232  is preferably set to substantially the same size as the center opening  221  formed in the heater  220 . Further, the pair of getter materials  231  and  232  are arranged such that the center openings  233  and  234  are positioned on the central axis (C), respectively, as illustrated in  FIG. 11 . Thus, the center openings  233  and  234  of the pair of getter materials  231  and  232  communicate with the center opening  221  of the heater  220  along the central axis (C). 
         [0143]    In addition, a plurality of concave portions  235  and a plurality of convex portions  236  are alternately formed on each face of the getter materials  231  and  232  on each side opposing the heater  220  as illustrated in  FIG. 11 . The concave portion  235  and the convex portion  236  are formed at equal intervals in concentric circles having the central axis (C) as the central axis thereof. That is, the concentrically circular convex portion  236  is formed between the concentrically circular concave portions  235 . When the unevenness is formed on each surface of the getter materials  231  and  232  in this manner, it is possible to increase a surface area of a getter film, and thus, it is possible to enhance the efficiency of collecting gases inside the casing  210 . 
         [0144]    [2-4. Heat Shield] 
         [0145]    The heat shield  240  is a shield member which is configured to house the casing  210  therein and to prevent heat generated by the heater  220  from leaking outside. The heat shield  240  is a member that is arbitrarily provided, but is preferably provided in order to prevent an external device from being affected by the heat. The heat shield  240  can be formed using a known material. In addition, an opening is formed in a part of the heat shield  240  so that the external connection flanges  214  and  216  of the casing  210  protrude through the opening as illustrated in  FIG. 10 . 
         [0146]    [2-5. Combination of Ion Pump and Heating and Non-Evaporating Getter Pump] 
         [0147]    The heating and non-evaporating getter pump  200  having the above-described configuration can be combined with the ion pump  100  in a stacked manner. That is, the ultra-high vacuum creating device  1  of the present invention can be constructed by combining one or a plurality of ion pumps  100  and one or a plurality of heating and non-evaporating getter pumps  200 .  FIGS. 12 to 14  illustrates examples of the combination of the ion pump  100  and the heating and non-evaporating getter pump  200 . 
         [0148]      FIG. 12  illustrates a configuration example in which the one ion pump  100  and the one heating and non-evaporating getter pump  200  are combined. As illustrated in  FIG. 12 , the ion pump  100  and the heating and non-evaporating getter pump  200  share the central axis (C), and a columnar space is formed along the central axis (C). Thus, it is possible to cause the experimental equipment to be housed in or to pass through the columnar space. 
         [0149]    To be specific, the relay casing member  117  is provided when the ion pump  100  and the heating and non-evaporating getter pump  200  are stacked. The relay casing member  117  is arranged between the upper casing member  213  of the heating and non-evaporating getter pump  200  and the lower casing member  115  of the ion pump  100 . The relay casing member  117  is bonded to the upper casing member  213  of the heating and non-evaporating getter pump  200 , thereby functioning as the casing  210  for the heating and non-evaporating getter pump  200 . At the same time, the relay casing member  117  is bonded to the lower casing member  115  of the ion pump  100 , thereby also functioning as the casing  110  for the ion pump  100 . Incidentally, when the relay casing member  117  is bonded to the upper casing member  213  of the heating and non-evaporating getter pump  200  and the lower casing member  115  of the ion pump  100 , flange portions formed in the respective casing members  213 ,  115  and  117  can be butted and bonded to each other. In this manner, it is possible to make the overall size of the ultra-high vacuum creating device  1  in the central-axis direction compact by providing the relay casing member  117  that can be shared between the heating and non-evaporating getter pump  200  and the ion pump  100 . 
         [0150]    In addition, the constricted portion  118  that is inwardly constricted is formed in the central portion of the relay casing member  117  in the central-axis direction. The plate-shaped magnets  141  and  142  of the ion pump  100  are arranged in the constricted portion  118  of the relay casing member  117 . 
         [0151]    In addition,  FIG. 13  illustrates the ultra-high vacuum creating device  1  having a three-stage structure in which the heating and non-evaporating getter pumps  200  are stacked at the upper and lower stages, respectively, of the ion pump  100 . When the ultra-high vacuum creating device  1  having the three-stage structure is constructed, the two relay casing members  117  may be provided. 
         [0152]    In addition,  FIG. 14  illustrates the ultra-high vacuum creating device  1  having a three-stage structure in which the one heating and non-evaporating getter pump  200  is further stacked above the ion pumps  100  stacked in two stages. In this case, the two relay casing member  117  may also be used. 
         [0153]    [2-6. Multi-Stage Structure of Heating and Non-Evaporating Getter Pump] 
         [0154]      FIGS. 15 to 17  illustrate multi-stage structures of the heating and non-evaporating getter pump  200  for reference.  FIG. 15  illustrates an example of a structure in which the heating and non-evaporating getter pumps  200  are stacked in two stages. In addition,  FIG. 16  illustrates an exploded view of the heating and non-evaporating getter pump  200  having the two-stage structure. As illustrated in  FIGS. 15 and 16 , the two heating and non-evaporating getter pumps  200  share the central axis (C), and a flow path is formed along the central axis (C). Thus, it is possible to efficiently supply gases to each of the two heating and non-evaporating getter pumps  200 . 
         [0155]    To be specific, when the heating and non-evaporating getter pumps  200  are stacked, the casing  210  includes a relay casing member  217  in addition to the upper casing member  213  in which the upper external connection flange  214  is formed and the lower casing member  215  in which the lower external connection flange  216  is formed. The relay casing member  217  is arranged between the upper casing member  213  and the lower casing member  215 . The relay casing member  217  is bonded to the upper casing member  213 , thereby functioning as the casing  210  for the heating and non-evaporating getter pump  200  at the upper stage. At the same time, the relay casing member  217  is bonded to the lower casing member  215 , thereby also functioning as the casing  210  for the heating and non-evaporating getter pump  200  at the lower stage. Incidentally, when the relay casing member  217  is bonded to the upper casing member  213  and the lower casing member  215 , flange portions formed in the respective casing members  213 ,  215  and  217  can be butted and bonded to each other. In this manner, it is possible to make the overall size of the ultra-high vacuum creating device  1  in the central-axis direction compact by providing the relay casing member  217  that can be shared between the upper-stage heating and non-evaporating getter pump  200  and the lower-stage heating and non-evaporating getter pump  200 . 
         [0156]    In addition, when the heating and non-evaporating getter pumps  200  are stacked as illustrated in  FIGS. 16 and 17 , a stay member  218  is preferably provided between the getter material  232  below the upper-stage heating and non-evaporating getter pump  200  and the getter material  231  above the lower-stage heating and non-evaporating getter pump  200 . The stay member  218  is a support member to which the getter materials  231  and  232  are mounted. The stay member  218  can be formed in a disk shape, for example, which has an opening formed at the center thereof. The stay member  218  may be fixed to, for example, the relay casing member  217 . When the stay member  218  is provided in this manner, it is possible to stably keep the getter materials  231  and  232 . 
         [0157]      FIG. 17  further illustrates the heating and non-evaporating getter pump  200  having a three-stage structure. As illustrated in  FIG. 17 , the two relay casing members  217  and the two stay members  218  may be provided when the heating and non-evaporating getter pump  200  are formed in the three-stage structure. 
         [0158]    [3. Sublimation Pump] 
         [0159]    The ultra-high vacuum creating device  1  according to the present invention may be provided with a sublimation pump  300  in addition to the ion pump  100 . In addition, the above-described heating and non-evaporating getter pump  200  can be further combined.  FIGS. 18 to 20  illustrate configuration examples of the sublimation pump  300 . The sublimation pump  300  is a vacuum pump which performs exhaust by directly heating a sublimation filament inside a casing to be sublimated, and forming an active film to adsorb gases inside the casing. When the operation principle of the sublimation pump  300  is briefly described, first, a filament coated with titanium is electrically heated in vacuum so that the titanium on the filament surface is evaporated and vapor-deposited on each surface of the casing  310  and the shield  330 . This series of phenomena is called sublimation. Further, a fresh face immediately after the vapor deposition of titanium has a strong molecular adsorption (getter) performance, and functions as a pump that adsorbs gases until the face is completely covered by gas molecules. 
         [0160]    The ion pump  100  has an advantage that it is possible to collect an inert gas such as nitrogen, helium, and argon, but has a disadvantage that rough adsorption using another vacuum device in advance is required in order to use the ion pump  100  because an operating range thereof is the ultra-high vacuum (0.1 to 10 −5  Pa) or lower. On the other hand, the sublimation pump  300  can operate in the low vacuum (100 Pa or higher) or the medium vacuum (100 to 0.1 Pa) and has an advantage that the operating range is relatively wide, but has a disadvantage that a vacuum level inside a vacuum bath temporarily deteriorates during the sublimation operation because the operating time of the formed active film is short and it is necessary to perform the sublimation work every two to four hours. Thus, it is possible to complement the disadvantages of the pumps one another by combining the ion pump  100  and the sublimation pump  300  like the ultra-high vacuum creating device  1  of the present invention. Therefore, it is possible to provide the ultra-high vacuum creating device  1  with the favorable usability by combining the ion pump  100  and the sublimation pump  300 . It is novel to provide such a uniaxially symmetric structure of the sublimation pump  300  in order for series-connection with another pump. 
         [0161]      FIG. 18  illustrates the configuration example of the sublimation pump  300 .  FIG. 18  illustrates a cross-sectional view when the sublimation pump is seen in a plan view, and a cross-sectional view when the sublimation pump is seen from a side view. In addition,  FIG. 19  illustrates an exploded view of the sublimation pump  300 . As illustrated in  FIGS. 18 and 19 , the sublimation pump  300  is configured to include a casing  310 , a sublimation filament  320 , a shield member  330 , and a heat shield  340 . In the present embodiment, the casing  310  is arranged inside the heat shield  340 . In addition, the sublimation filament  320  and the shield member  330  are arranged inside the casing  310 . In addition, external connection flanges  314  and  316  formed in the casing  310  protrude outside the heat shield  340 . The sublimation pump  300  is connected to another external device via the external connection flanges  314  and  316 . The external device to which the sublimation pump  300  is connected is, for example, a vacuum chamber, a sample chamber, or the like which is a target to be turned into a vacuum state. In addition, the external device may be another vacuum pump (an ion pump, a heating and non-evaporating getter pump, a sublimation pump, and the like). 
         [0162]    [3-1. Casing] 
         [0163]    The casing  310  is a frame which forms a workspace configured to collect gas molecules or to house a sample and experimental equipment or causing the sample and the experimental equipment to pass therethrough. The casing  310  of the sublimation pump  300  has basically the same structure as the casing  110  of the ion pump  100  described above. Thus, the description for the casing  110  of the ion pump  100  can be appropriately incorporated to the description for the casing  310  of the sublimation pump  300 . 
         [0164]    That is, the casing  310  of the sublimation pump  300  includes at least one opening ( 311  or  312 ). In the embodiment illustrated in  FIG. 18 , the casing  310  includes the two openings  311  and  312 . Accordingly, the sublimation pump  300  is extensible in multiple stages in the up-and-down direction. In addition, a space, configured to house the sublimation filament  320  and the shield member  330 , is formed in the sublimation pump  300  by bonding the upper casing member  313  and the lower casing member  315 . In addition, the upper casing member  313  includes the upper external connection flange  314 , the lower casing member  315  includes the lower external connection flange  316 . The upper opening  311  is formed in the upper external connection flange  314 , and the lower opening  312  is formed in the lower external connection flange  316 . Further, both the upper opening  311  and the lower opening  312  are formed on the central axis (C) in the casing  310 . Accordingly, a flow path passing from the flow path passing the upper opening  311  through the lower opening  312  is linearly formed in the casing  310 . 
         [0165]    [3-2. Sublimation Filament] 
         [0166]    The sublimation filament  320  is a member that is sublimated when being heated by electrical heating to form the active film having the getter effect inside the casing  310 . Thus, the sublimation filament  320  is connected to a power supply (not illustrated). A known material having the getter effect can be used as the sublimation filament  320 . For example, the sublimation filament  320  may be a simple metal substance made of titanium, samarium, titanium, ytterbium, gadolinium, or erbium or may be made of an alloy including these metals. 
         [0167]    As illustrated in  FIG. 18 , the sublimation filament  320  is formed in a ring shape having an opening at the center thereof. In particular, the sublimation filament  320  has preferably a circular ring shape. However, the sublimation filament  320  may have a triangular ring shape, a square ring shape, or other polygonal ring shapes. 
         [0168]    The sublimation filament  320  and the casing  310  share the central axis (C). Thus, the opening of the sublimation filament  320  communicates with the two openings  311  and  312  of the casing  310  along the central axis (C). 
         [0169]    [3-3. Shield Member] 
         [0170]    The shield member  330  is a member configured to form the active film by causing metal atoms generated from the sublimation filament  320  and having the getter effect to adhere thereto. When the shield member  330  is provided, a surface area of the active film is improved. As illustrated in  FIG. 18 , the shield member  330  is arranged at the inner side of the ring-shaped sublimation filament  320  inside the casing  310 . The shield member  330  also provides a function of preventing a member released from the filament from intruding into the workspace around the central axis. 
         [0171]    The shield member  330  has preferably a ring shape as illustrated in  FIG. 18 . In particular, the shield member  330  has preferably a circular ring shape. However, the shield member  330  may have a triangular ring shape, a square ring shape or other polygonal ring shapes. The shape of the shield member  330  may be formed in accordance with the shape of the sublimation filament  320 . In this manner, the shield member  330  is arranged inside the opening formed at the center of the sublimation filament  320 . 
         [0172]    The shield member  330  and the casing  310  and the sublimation filament  320  share the central axis (C). Thus, the opening of the shield member  330  communicates with the two openings  311  and  312  of the casing  310  and the opening of the sublimation filament  320  along the central axis (C). Accordingly, a linear flow path is formed in the sublimation pump  300  along the central axis (C). 
         [0173]    [3-4. Heat Shield] 
         [0174]    The heat shield  340  is a shield member which is configured to house the casing  310  therein and to prevent heat generated by the sublimation filament  320  from leaking to the outside. The heat shield  3400  is a member that is arbitrarily provided, but is preferably provided in order to prevent an external device from being affected by the heat. The heat shield  340  can be formed using a known material. In addition, an opening is formed in a part of the heat shield  340  so that the external connection flanges  314  and  316  of the casing  310  protrude through the opening as illustrated in  FIG. 18 . 
         [0175]    [2-5. Combination of Ion Pump, Sublimation Pump and Heating and Non-Evaporating Getter Pump] 
         [0176]    The sublimation pump  300  having the above-described configuration can be combined with the ion pump  100  and the heating and non-evaporating getter pump  200  in a stacked manner. That is, the ultra-high vacuum creating device  1  of the present invention can be constructed by combining one or a plurality of ion pumps  100  with one or a plurality of heating and non-evaporating getter pumps  200  and one or a plurality of sublimation pumps  300 .  FIG. 20  illustrates an example of combination of the ion pump  100 , the heating and non-evaporating getter pump  200 , and the sublimation pump  300 . 
         [0177]      FIG. 20  illustrates a configuration example in which the one ion pump  100 , the one heating and non-evaporating getter pump  200 , and the one sublimation pump  300  are combined. As illustrated in  FIG. 12 , the ion pump  100 , the heating and non-evaporating getter pump  200 , and the sublimation pump  300  share the central axis (C), and a flow path is formed along the central axis (C). Thus, it is possible to efficiently supply gases to each of the ion pump  100 , the heating and non-evaporating getter pump  200 , and the sublimation pump  300 . 
         [0178]    To be specific, the two relay casing members  117  are provided when the heating and non-evaporating getter pump  200  and the sublimation pump  300  are stacked on the ion pump  100 . In such a three-stage structure, the casing  110  of the ion pump  100  positioned at the middle stage is formed by bonding the two relay casing members  117  to each other. In addition, the upper relay casing member  117  is bonded to the lower casing member  215  of the heating and non-evaporating getter pump  200 . Thus, the upper relay casing member  117  functions as both the casing  110  of the ion pump  100  and the casing  210  of the heating and non-evaporating getter pump  200 . In addition, the lower relay casing member  117  is bonded to the upper casing member  313  of the sublimation pump  300 . Thus, the lower relay casing member  117  functions as both the casing  110  of the ion pump  100  and the casing  310  of the sublimation pump  300 . In this manner, it is possible to make the overall size of the ultra-high vacuum creating device  1  in the central-axis direction compact by providing the relay casing member  117  that can be shared among the respective vacuum pumps  100 ,  200  and  300 . 
         [0179]    In addition, the constricted portion  118  that is inwardly constricted is formed in the central portion of the relay casing member  117  in the central-axis direction. The plate-shaped magnets  141  and  142  of the ion pump  100  are arranged in the constricted portion  118  of the relay casing member  117 . 
         [0180]    The embodiment of the present invention has been described as above with reference to drawings in the specifications of the present application in order to express the content of the present invention. However, the present invention is not limited to the embodiment described hereinbefore, and encompasses obvious modifications and improvements made by those skilled in the art based on the matters described in the specifications of the present application. 
         [0181]      FIGS. 1 to 20  illustrates the examples of how to combine the ion pump  100 , the heating and non-evaporating getter pump  200 , and the sublimation pump  300 . However, the method of combining these pumps  100 ,  200  and  300  is not limited to the drawings, and the combination can be made by freely selecting each number or arrangement of the pumps as necessary. 
       INDUSTRIAL APPLICABILITY 
       [0182]    The present invention relates to the ultra-high vacuum creating device including the ion pump. The ultra-high vacuum creating device of the present invention can be suitably applied to, for example, an ion beam processing device, various processing devices, an ionized gas generation device, an ion source generation device, and the like. In addition, the ultra-high vacuum creating device of the present invention can also be suitably applied to, for example, a synchrotron radiation facility, an ion trap, an atomic clock, and the like. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           1  ultra-high vacuum creating device 
           2  power supply 
           3  earth 
           100  ion pump 
           110  casing 
           111  upper opening 
           112  lower opening 
           13  upper casing member 
           114  external connection flange (upper side) 
           115  lower casing member 
           116  external connection flange (lower side) 
           117  relay casing member 
           118  constricted portion 
           120  electrode group 
           120   a  center opening 
           121  electrode 
           122  conducting wire 
           123  hollow electrode 
           123   a  upper and lower flat surface portions 
           123   b  side surface portion 
           124  center opening 
           131  plate-shaped electrode (upper side) 
           132  plate-shaped electrode (lower side) 
           133  center opening (upper side) 
           134  center opening (upper side) 
           141  plate-shaped magnet (upper side) 
           142  plate-shaped magnet (lower side) 
           143  center opening (upper side) 
           144  center opening (lower side) 
           145  shared plate-shaped magnet 
           150  magnetic shield 
           200  heating and non-evaporating getter pump 
           210  casing 
           211  upper opening 
           212  lower opening 
           213  upper casing member 
           214  external connection flange (upper side) 
           215  lower casing member 
           216  external connection flange (lower side) 
           217  relay casing member 
           218  stay member 
           220  heater 
           221  center opening 
           231  getter material (upper side) 
           232  getter material (lower side) 
           233  center opening (upper side) 
           234  center opening (lower side) 
           235  concave portion 
           236  convex portion 
           240  heat shield 
           300  sublimation pump 
           310  casing 
           311  upper opening 
           312  lower opening 
           313  upper casing member 
           314  external connection flange (upper side) 
           315  lower casing member 
           316  external connection flange (lower side) 
           320  sublimation filament 
           330  shield member 
           340  heat shield