Leak detector and ion source for leak detector

Abstract

To provide a leak detector and an ion source for a leak detector that improve the insulation durability between electrodes without changing the size and weight of the ion source. A leak detector that guides a gas from an object to be inspected to an analysis tube that is evacuated, ionizes the gas using an ion source provided in the analysis tube, and detects the ionized gas to thereby perform a leak inspection on the object to be inspected, wherein the ion source includes a filament that emits hot electrons that ionize the gas, an electrode that is electrically connected to the filament, a base member through which the electrode passes and that separates an internal space in which the filament is disposed from the outside, a first insulation member that is provided in a through-hole for the electrode formed in the base member and that insulates the electrode from the base member, and a second insulation member that is provided around the electrode and that extends toward the internal space side more than a surface of the base member that faces the internal space.

Description

Technical Field

[0001] This invention relates to a leak detector and an ion source for the leak detector. Background Technology

[0002] As an existing leak detector, as shown in Patent Document 1, there is a leak detector that guides the helium gas flowing into the test subject to an analysis tube for detection, and is called a helium leak detector.

[0003] The leak detector has the following structure: helium is guided by evacuating the analysis tube using a vacuum pump, and helium is ionized using an ion source located inside the analysis tube.

[0004] To describe the ion source in more detail, the ion source is configured such that by flowing an electric current between a pair of electrodes on which a filament is mounted, the filament is heated to release thermionic electrons, which are then used to ionize helium and detect it by an ion collector.

[0005] In this structure, the electrodes are supported on a substrate member that separates the interior from the exterior of the ion source. More specifically, the electrodes are disposed through glass, which serves as an insulator embedded in a through-hole in the substrate member. This glass insulates the electrodes from the substrate member and maintains insulation between the electrodes.

[0006] However, if components of the oil used in the vacuum pump mentioned above and the oil adhering to the test sample are attracted by the vacuum-evacuated analysis tube and fly to the vicinity of the ion source, these components will carbonize due to the heat of the filament, resulting in carbides adhering to the glass mentioned above. As a result, due to the adhered carbides, insulation between the electrodes and the substrate cannot be maintained, leading to bridging between the electrodes and insulation failure, and the inability to release hot electrons.

[0007] To prevent this kind of insulation failure, a large distance is considered between the electrode and the substrate component. However, this would lead to the enlargement of the parts around the electrode, the increase in weight, and other problems such as making the processing of the ion source inconvenient.

[0008] [Existing technical documents]

[0009] [Patent Literature]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 2020-197127 Summary of the Invention

[0011] [The problem the invention aims to solve]

[0012] Therefore, the present invention was made in view of the problems described above, and its objective is to improve the insulation durability between electrodes.

[0013] [Technical means to solve the problem]

[0014] A first embodiment of the present invention relates to a leak detector that guides gas from a test subject to a vacuum-sealed analysis tube, and uses an ion source disposed within the analysis tube to ionize and detect the gas, thereby performing a leak check on the test subject. In the leak detector, the ion source includes: a filament that releases thermionic electrons to ionize the gas; an electrode electrically connected to the filament; a substrate member through which the electrode passes and which separates the internal space where the filament is disposed from the outside; a first insulating member disposed within an electrode through-hole formed on the substrate member and which mediates between the electrode and the substrate member; and a second insulating member disposed around the electrode and extending towards the internal space side beyond the surface of the substrate member facing the internal space.

[0015] A second embodiment of the present invention relates to an ion source for a leak detector, which is used to perform leak detection on a test subject and is disposed in a vacuum-sealed analysis tube to ionize gas from the test subject guided to the analysis tube. The ion source for the leak detector includes: a filament that releases thermionic electrons to ionize the gas; an electrode electrically connected to the filament; a substrate member through which the electrode passes and which separates the internal space in which the filament is disposed from the outside; a first insulating member disposed in an electrode through-hole formed on the substrate member and which mediates between the electrode and the substrate member; and a second insulating member disposed around the electrode and extending toward the internal space side beyond the surface of the substrate member facing the internal space.

[0016] [The effects of the invention]

[0017] According to the present invention, since a second insulating member is included that extends toward the inner space side of the surface of the substrate member facing the inner space, the insulation distance between the electrode and the substrate member can be obtained by utilizing the outer peripheral surface of the second insulating member, thereby significantly improving the insulation durability between the electrodes. Attached Figure Description

[0018] Figure 1 This is a schematic diagram showing the overall structure of a leak detector according to an embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram showing the internal structure of the analysis tube in the described embodiment.

[0020] Figure 3 This is a schematic diagram showing the structure of the ion source according to the described embodiment.

[0021] Figure 4 This is a schematic diagram showing the internal structure of the ion source in the described embodiment.

[0022] Figure 5 This is a cross-sectional view showing the structure of the second insulator in the described embodiment.

[0023] Figure 6 This is a schematic diagram illustrating the effect of the second insulator based on the described embodiment.

[0024] Figure 7 This is a cross-sectional view showing the structure of the second insulating member in other embodiments.

[0025] Figure 8 This is a cross-sectional view showing the structure of the second insulating member in other embodiments.

[0026] Figure 9 This is a cross-sectional view showing the structure of the second insulating member in other embodiments.

[0027] Figure 10 This is a cross-sectional view showing the structure of the cover member in other embodiments.

[0028] [Explanation of Symbols]

[0029] 100: Leak Detector

[0030] X: Subject

[0031] 4: Analytical tubes

[0032] 6: Ion source

[0033] 61: Filament

[0034] 62: Anode

[0035] 63: Shielding components

[0036] 64: Accelerating the narrow slit

[0037] 65: Electrode

[0038] 66: Base components

[0039] 66h: Through hole for electrode

[0040] 661: Base surface

[0041] 67: First insulating component

[0042] 671: Opposing planes

[0043] 6S: Interior Space

[0044] 68: Second insulating component

[0045] 68h: Insertion hole

[0046] 681: Opposing planes

[0047] 682: Outer circumference

[0048] 69: Cover component Detailed Implementation

[0049] A leak detector according to one embodiment of the present invention will be described with reference to the accompanying drawings.

[0050] [Overall Structure]

[0051] The leak detector 100 of this embodiment is used, for example, to check for leaks in a test object X such as a vacuum container, and as... Figure 1 As shown, it is connected to the test object X via the test port P pipe.

[0052] Specifically, the leak detector 100 includes at least three vacuum pumps: an oil rotary pump 1, a traction pump 2, and a turbomolecular pump 3; three valves V1 to V3 that open and close the exhaust path and the helium introduction path; and an analysis tube 4. Furthermore, the opening and closing states of each valve V1 to V3 are controlled by a control device (not shown) based on instructions from the operator of the leak detector 100. Additionally, the number of vacuum pumps and valves is not limited to... Figure 1 The shape shown can be appropriately changed according to the structure of the device.

[0053] The analysis tube 4 is connected to the rotary oil pump 1 via the turbomolecular pump 3, the traction pump 2, and valve V1. The test subject X, which is to be tested for leakage, is connected to the rotary oil pump 1 via the test port P and valve V2. In addition, the test subject X is connected to the exhaust port 3a of the turbomolecular pump 3 via the test port P and valve V3, wherein valve V3 is open in the reverse diffusion exhaust mode of the helium leak detector (or, other modes such as intermediate exhaust mode or direct flow).

[0054] The leak check for test subject X is performed according to the following procedure. Furthermore, for simplicity, only the case of reverse diffusion exhaust mode will be described here.

[0055] (1) Close valves V2 and V3 and open valve V1, and use a series structure of turbomolecular pump 3, traction pump 2 and oil rotary pump 1 to vent the analysis tube 4 under vacuum until it reaches a specified vacuum level (helium background value).

[0056] (2) Install the test subject X of the leakage test at the test port P.

[0057] (3) After the background value in the analysis tube 4 drops below the specified background value, open valve V2 and use oil rotary pump 1 to perform vacuum exhaust (rough vacuum exhaust) on the test subject X.

[0058] (4) Close valve V2 and open valve V3 to begin leak detection using analysis tube 4. That is, attempt to allow helium (He) gas to flow from the outside of the test object X through the leak test site into the test object X.

[0059] (5) If there is a leak at the leak test site of the test object X, He gas will enter the test object X. The He gas passes through the open valve V3 and the turbomolecular pump 3 to reach the analysis tube 4. The amount of leakage of the test object X is determined by detecting the helium gas through the analysis tube 4.

[0060] Next, use Figure 2 The analysis tube 4 is described below.

[0061] The analysis tube 4 includes: an ion source 6 disposed within a sealed container 5; a permanent magnet 7 that forms a magnetic field emitted by helium ions ionized by the ion source 6; an intermediate slit 8 that allows helium ions bent by the magnetic field to pass through while preventing other ions (e.g., ions from components contained in the air) from passing through; and an ion collector 9 that detects the helium ions that have passed through the intermediate slit 8.

[0062] Furthermore, the ion source 6 described in the leakage detector 100 of the present invention will be described in detail below.

[0063] like Figure 3 As shown, the ion source 6 heats the filament 61 to release thermionic electrons, and uses the thermionic electrons to ionize helium.

[0064] As an example of a specific structure of ion source 6, such as Figure 3 As shown, an ion source can be exemplified by including a filament 61, an anode 62, a shield 63, and an accelerating slit 64. In this structure, thermionic electrons released from the surface of the filament 61 fly towards the anode 62, which is given a positive potential. However, since the anode 62 includes a thin metal wire, most of the thermionic electrons pass through the anode 62 towards the shield 63. Moreover, since the shield 63 is given a negative potential, the thermionic electrons do not reach the shield 63 but continue to fly back. The thermionic electrons in this reciprocating motion collide with the gas present between the filament 61 and the shield 63, thereby ionizing the gas into ions and electrons. The ionized ions fly towards the accelerating slit 64, which is the negative electrode, relative to the anode 62, and are ejected into the magnetic field through the opening 641 formed in the accelerating slit 64. Furthermore, the structure of the ion source 6 is not limited to this; various types of ion sources can be used.

[0065] like Figure 4As shown, the ion source 6 of this embodiment includes a filament 61 and a pair of columnar electrodes 65 electrically connected to the filament 61, and is configured such that by allowing current to flow between these electrodes 65, the filament 61 is heated to release thermionic electrons. Furthermore, in this embodiment, a pair of filaments 61 are provided, and a conductive member 611 is provided between these filaments 61 and the electrodes 65. Additionally, the anode 62 described above is also electrically connected to an electrode 65, so that a positive potential can be applied to the anode 62 via the electrode 65.

[0066] In the structure described above, the electrodes 65 need to be mutually insulated because the electrical connection of the multiple electrodes 65 described above would cause insulation failure.

[0067] Therefore, as Figure 4 and Figure 5 As shown, the ion source 6 includes a metal substrate 66 supporting the electrode 65 and a first insulating member 67 that insulates the electrode 65 from the substrate 66.

[0068] like Figure 5 As shown, the base member 66 is a flat plate that supports the electrode 65 and separates the internal space 6S where the filament 61 is disposed from the outside. The base member 66 here is, for example, a circular iron plate, and has through holes 66h for electrodes extending along its thickness direction. However, the material and shape of the base member 66 are not limited to those shown in the figure and can be appropriately varied.

[0069] The electrode through-hole 66h is, for example, circular in shape, through which the electrode 65 passes. In this embodiment, a plurality of electrode through-holes 66h are provided at equal intervals, for example, around the center of the base member 66. However, the shape, arrangement, and number of electrode through-holes 66h are not limited to the form shown in the figure and can be adapted accordingly.

[0070] The first insulating member 67 is an insulating material such as glass, disposed within the electrode through-hole 66h described above. In this embodiment, the electrode through-hole 66h is pre-filled with glass serving as the first insulating member 67. By inserting the electrode 65 while the glass is molten and then cooling it, the electrode 65 is supported on the substrate member 66 while the first insulating member 67 is penetrated. Thus, the first insulating member 67 exists between the electrode 65 and the substrate member 66, insulating them.

[0071] Moreover, such as Figure 4 and Figure 5 As shown, the ion source 6 in this embodiment also includes a second insulating member 68, which, together with the first insulating member 67, insulates the electrode 65 from the substrate member 66.

[0072] The second insulating member 68 is an insulating material such as alumina disposed around the electrode 65, and in this embodiment it is a different member from the first insulating member 67. However, the second insulating member 68 may also be integral with the first insulating member 67.

[0073] To be more specific, as follows: Figure 4 and Figure 5 As shown, the second insulating member 68 is, for example, cylindrical, and has an insertion hole 68h for inserting the electrode 65. The second insulating member 68 is inserted into the electrode 65 through the insertion hole 68h, thereby the second insulating member 68 is configured to surround the outer peripheral surface of the electrode 65.

[0074] The first insulating member 67 and the second insulating member 68 are arranged facing each other, and the facing surfaces 671 and 681 of the first insulating member 67 and the second insulating member 68 are in contact with each other. That is, the second insulating member 68 extends from the surface of the first insulating member 67 facing the inner space 6S toward the inner space 6S.

[0075] In this embodiment, the facing surface 681 of the second insulating member 68 is smaller than the facing surface 671 of the first insulating member 67, and the entire facing surface 681 of the second insulating member 68 is confined inside the facing surface 671 of the first insulating member 67. However, the facing surface 681 of the second insulating member 68 may be the same size (same shape) as the facing surface 671 of the first insulating member 67, or it may be larger than the facing surface 671 of the first insulating member 67.

[0076] Moreover, such as Figure 5 As shown, the second insulating member 68 extends toward the inner space 6S side further than the surface 661 (hereinafter also referred to as the base surface 661) of the base member 66 described above facing the inner space 6S. In other words, the outer peripheral surface 682 of the second insulating member 68 extends toward the inner space 6S side further than the base surface 661.

[0077] The outer peripheral surface 682 of the second insulating member 68 extends in a direction orthogonal to the base surface 661 or in a direction inclined from the orthogonal direction. As specific shapes, examples include undulating shapes (corrugated shapes) that undulate along the direction of extension, convex and concave shapes that are provided along the direction, or straight tube shapes that extend straight along the direction.

[0078] In the embodiment, the second insulating member 68 is a cylindrical member whose axial direction is orthogonal to the base surface 661, and an insulator is used, for example.

[0079] The longer the outer peripheral surface 682 of the second insulating member 68 is along the axial direction, the longer the insulation distance between the base member 66 and the electrode 65. Therefore, from the viewpoint of obtaining the insulation distance between the base member 66 and the electrode 65, it is preferable that the axial dimension (height dimension) of the second insulating member 68 is long, specifically, preferably at least 1 / 2 times the diameter of the second insulating member 68. Alternatively, the axial dimension (height dimension) of the second insulating member 68 is preferably 10% or more of the height of the electrode 65, more preferably 30% or more, and even more preferably 50% or more. Alternatively, the axial dimension (height dimension) of the second insulating member 68 is preferably 2 mm or more, more preferably 4 mm or more. In particular, experiments have shown that in areas with a height dimension of 2 mm or more, the carbides described later are difficult to adhere.

[0080] [Effects of this implementation method]

[0081] According to the leakage detector 100 configured in this way, since it includes a second insulating member 68 extending towards the inner space 6S side of the base surface 661 of the base member 66, the insulation distance between the electrode 65 and the base member 66 can be obtained by utilizing the outer peripheral surface 682 of the second insulating member 68.

[0082] Specifically, the surfaces that contribute to insulation include the surface of the first insulating member 67 that is parallel to the base member 66 and faces the internal space 6S, the outer peripheral surface 682 of the second insulating member 68 that is orthogonal to the base member 66, and the surface that is parallel to the base member 66, thereby increasing the insulation distance.

[0083] As a result, the insulation durability between electrodes 65 can be significantly improved with almost no change to the size and weight of ion source 6.

[0084] To explain more specifically, the components of the oil used by vacuum pumps 1 to 3 and the oil adhering to the test object X are carbonized due to the heat of filament 61. Therefore, the carbides fly from the direction of filament 61, resulting in their easy adhesion to the first insulating member 67. However, because the carbides fly from the direction of filament 61, such as... Figure 6 As shown, the carbide is difficult to adhere to the outer peripheral surface 682 of the second insulating member 68 in the direction. Therefore, the outer peripheral surface 682 can be used to maintain the insulation between the electrode 65 and the substrate member 66, thereby improving the insulation durability between the electrodes 65 as described above.

[0085] [Other Implementation Methods]

[0086] Other implementation methods will be described.

[0087] For example, the form in which the first insulating member 67 and the second insulating member 68 are in contact has been described in the embodiment, but as... Figure 7 As shown, the first insulating member 67 and the second insulating member 68 may also be non-contacting. In this case, the first insulating member 67 does not need to completely fill the electrode through-hole 66h. Furthermore, the second insulating member 68 can be configured to extend from the base surface 661 toward the internal space 6S and block the electrode through-hole 66h.

[0088] Furthermore, the second insulating member 68 is not limited to a cylindrical shape. For example, it can be a cylindrical shape with a triangular, rectangular, or polygonal cross-section. As long as the shape extends towards the inner space 6S side of the base surface 661, it does not need to be cylindrical and can be set to various shapes.

[0089] In the described embodiment, the first insulating member 67 and the second insulating member 68 are described as having different forms, but as... Figure 8 As shown, the first insulating member 67 and the second insulating member 68 can also be integrated. In this case, the second insulating member 68 is the part located on the side of the inner space 6S that is closer to the base surface 661.

[0090] Furthermore, from the viewpoint of preventing carbides from adhering to the second insulating component, such as Figure 9 As shown, a portion of the facing surface 681 of the second insulating member 68, which is opposite to the first insulating member 67, may also be non-contact with the first insulating member 67. If so, it is difficult for carbides to adhere to a portion of the facing surface 681, thereby maintaining the insulation between the electrode 65 and the substrate member 66.

[0091] Furthermore, from the viewpoint of preventing carbides from adhering to the first insulating member 67, such as Figure 10 As shown, a cover member 69 may also be included, which is disposed further inside the space 6S than the first insulating member 67 and covers the first insulating member 67. In this case, the cover member 69 does not necessarily need to be insulating, and cover members of various materials can be used.

[0092] Furthermore, various modifications and combinations of embodiments are possible as long as they do not deviate from the spirit of this invention.

[0093] [Implementation Method]

[0094] Those skilled in the art will understand that the various exemplary embodiments described above, or variations thereof, are specific examples of the following embodiments.

[0095] (First item) A leak detector 100 of one embodiment guides gas from a test subject X to a vacuum-sealed analysis tube 4, and uses an ion source 6 disposed within the analysis tube 4 to ionize and detect the gas, thereby performing a leak check on the test subject X, and in the leak detector 100,

[0096] The ion source 6 includes:

[0097] Filament 61 releases thermionic electrons that ionize the gas;

[0098] Electrode 65 is electrically connected to the filament 61;

[0099] The base member 66 provides passage for the electrode 65 and separates the internal space 6S, in which the filament 61 is disposed, from the outside.

[0100] A first insulating member 67 is disposed within an electrode through-hole 66h formed on the substrate member 66, and exists as a separator between the electrode 65 and the substrate member 66; and

[0101] A second insulating member 68 is disposed around the electrode and extends toward the inner space 6S side further than the surface 661 of the base member 66 facing the inner space 6S.

[0102] According to the leakage detector 100 configured in this way, since it includes a second insulating member 68 extending further into the inner space 6S than the surface 661 facing the inner space 6S where the filament 61 is disposed on the substrate member 66, an insulating distance between the electrode 65 and the substrate member 66 can be obtained in the direction from said surface toward the inner space 6S side. As a result, the insulation durability between the electrodes 65 can be significantly improved. The first insulating member has an insulating effect on the surface parallel to the substrate member, and the second insulating member has an insulating effect on the surface parallel to the surface orthogonal to the substrate member. Since carbides are difficult to adhere to the surface of the second insulating member orthogonal to the substrate member, the insulation effect can be maintained extremely well.

[0103] (Second item) Another embodiment of the leakage detector 100 In the leakage detector 100 of the first item, the second insulating member 68 and the first insulating member 67 are different members.

[0104] According to this structure, existing components can be used as the first insulating member 67 and the base member 66 on which the first insulating member 67 is provided, thus significantly improving the insulation durability between the electrodes 65 without significantly changing the device structure up to this point.

[0105] (Third item) Another embodiment of the leakage detector 100 In the leakage detector 100 of the first or second embodiment, the second insulating member 68 is formed with an insertion hole 68h for the electrode 65 to be inserted.

[0106] According to this structure, by inserting the second insulating member 68 through the electrode 65, the insulation distance between the electrode 65 and the base member 66 can be extended, thus ensuring productivity.

[0107] (Fourth) Another embodiment of the leakage detector 100 In the leakage detector 100 of either the first or the second, the second insulating member 68 is cylindrical and has a dimension of 2 mm or more along its axial direction.

[0108] Experiments have shown that carbides are difficult to adhere in areas where the height of the second insulating component is greater than 2 mm. Therefore, this type of structure can achieve a more significant insulation effect.

[0109] (Fifth item) An embodiment of a leak detector ion source 6 is used for a leak detector 100 to perform leak detection on a test subject X, and is disposed in a vacuum-sealed analysis tube 4 to ionize the gas from the test subject X guided to the analysis tube 4, and the leak detector ion source 6 includes:

[0110] Filament 61 releases thermionic electrons that ionize the gas;

[0111] Electrode 65 is electrically connected to the filament 61;

[0112] The base member 66 provides passage for the electrode 65 and separates the internal space 6S, in which the filament 61 is disposed, from the outside.

[0113] A first insulating member 67 is disposed within an electrode through-hole 66h formed on the substrate member 66, and exists as a separator between the electrode 65 and the substrate member 66; and

[0114] A second insulating member 68 is disposed around the electrode and extends toward the inner space 6S side further than the surface 661 of the base member 66 facing the inner space 6S.

[0115] The ion source 6 for the leakage detector configured in this way can achieve the same effect as the leakage detector 100 described above, that is, it can achieve the effect of obtaining the insulation distance between the electrode 65 and the substrate member 66 by utilizing the second insulating member 68, and greatly improve the insulation durability between the electrodes 65.

[0116] (Sixth item) In one embodiment, a leak detector 100 guides gas from a test subject X to a vacuum-sealed analysis tube 4, and uses an ion source 6 disposed within the analysis tube 4 to ionize and detect the gas, thereby performing a leak check on the test subject X. Furthermore, in the leak detector 100…

[0117] The ion source 6 includes:

[0118] Filament 61 releases thermionic electrons that ionize the gas;

[0119] Electrode 65 is electrically connected to the filament 61;

[0120] The base member 66 provides passage for the electrode 65 and separates the internal space 6S, in which the filament 61 is disposed, from the outside.

[0121] A first insulating member 67 is disposed within an electrode through-hole 66h formed on the substrate member 66, and insulates the electrode 65 from the substrate member 66; and

[0122] Cover member 69 is disposed on the side of the internal space 6S further than the first insulating member 67 and covers the first insulating member 67.

[0123] According to the leakage detector 100 configured in this way, the insulation durability between the electrodes 65 can be improved because the cover member 69 can be used to suppress the adhesion of carbides to the first insulating member 67.

Claims

1. A leak detector that guides gas from a test object to a vacuum-sealed analysis tube, and ionizes and detects the gas using an ion source disposed within the analysis tube, thereby performing a leak check on the test object, wherein the leak detector, The ion source includes: The filament releases thermionic electrons that ionize the gas; The electrode is electrically connected to the filament; A base component through which the electrodes pass and which separates the internal space where the filament is disposed from the outside; A first insulating member is disposed within an electrode through-hole formed on the substrate member, and exists as a separator between the electrode and the substrate member; as well as A second insulating member is disposed around the electrode and extends further into the internal space than the surface of the base member facing the internal space. The second insulating member is formed as a cylinder extending from the base member toward the direction in which the filament is arranged, so as to suppress the adhesion of carbides flying from the direction in which the filament is arranged to the outer peripheral surface of the second insulating member.

2. The leak detector according to claim 1, wherein, The second insulating component is a different component from the first insulating component.

3. The leak detector according to claim 1 or 2, wherein, The second insulating member has an insertion hole for the electrode to pass through.

4. The leak detector according to claim 1 or 2, wherein, The second insulating member has a dimension of 2 mm or more along its axial direction.

5. An ion source for a leak detector, used for leak detection of a test object, and disposed within a vacuum-sealed analysis tube to ionize gas from the test object guided to the analysis tube, wherein the ion source for the leak detector comprises: The filament releases thermionic electrons that ionize the gas; The electrode is electrically connected to the filament; A base component through which the electrodes pass and which separates the internal space where the filament is disposed from the outside; A first insulating member is disposed within an electrode through-hole formed on the substrate member, and exists as a separator between the electrode and the substrate member; as well as A second insulating member is disposed around the electrode and extends further into the internal space than the surface of the base member facing the internal space. The second insulating member is formed as a cylinder extending from the base member toward the direction in which the filament is arranged, so as to suppress the adhesion of carbides flying from the direction in which the filament is arranged to the outer peripheral surface of the second insulating member.

6. A leak detector that directs gas from a test object to a vacuum-sealed analysis tube, and ionizes and detects the gas using an ion source disposed within the analysis tube, thereby performing a leak check on the test object, wherein the leak detector, The ion source includes: The filament releases thermionic electrons that ionize the gas; The electrode is electrically connected to the filament; A base component through which the electrodes pass and which separates the internal space where the filament is disposed from the outside; A first insulating member is disposed within an electrode through-hole formed on the substrate member, and insulates the electrode from the substrate member; as well as A cover component is disposed on the inner space side further than the first insulating component and covers the first insulating component. The cover member is configured as a circular plate with a diameter larger than that of the first insulating member, and is spaced apart and positioned closer to the filament side than the first insulating member, so as to suppress the adhesion of carbides flying from the direction in which the filament is positioned to the first insulating member.

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