Leak detector

Abstract

The present application is to make the background easy to stabilize in a leak detector (X) that introduces hydrogen gas leaked from a test body (W) into an analysis tube (100) to perform detection, and greatly shorten the time taken for background recovery, and to obtain sufficient measurement accuracy in a short time. The analysis tube (100) includes: an ion source portion (1) that ionizes hydrogen gas introduced into the inside thereof to generate hydrogen ions; an ion collector portion (2) that detects the amount of current of the hydrogen ions; and a re-inflow suppression structure (71), a re-inflow suppression structure (72), and a re-inflow suppression structure (73) that suppress re-inflow of hydrogen gas that becomes uncharged from ions in the ion collector portion (2) into the ion source portion (1).

Description

Technical Field

[0001] The present invention relates to a hydrogen leak detector used for, for example, airtightness inspection of a vacuum container. Background Art

[0002] The mass spectrometer-type hydrogen leak detector introduces hydrogen gas flowing from the leaking part of the test object into the analysis tube and measures the leakage amount.

[0003] [Prior art literature]

[0004] [Patent Document]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-180633 Summary of the Invention

[0006] [Problems to be solved by the invention]

[0007] In hydrogen leak detectors, the background is more difficult to stabilize than in helium leak detectors. Moreover, after measuring a large leak, for example, it takes considerable time for the background to recover to a level sufficient for the next measurement. Therefore, it is sometimes difficult to obtain sufficient measurement accuracy in a short period of time.

[0008] The main intended subject of the present invention is to facilitate stabilization of the background, particularly in a hydrogen leak detector, and to significantly shorten the time required for background recovery, thereby enabling sufficient measurement accuracy to be obtained in a short time.

[0009] [Technical means to solve the problem]

[0010] That is, the leak detector of the present invention introduces hydrogen gas leaked from a test body into an analysis tube for detection. The analysis tube includes: an ion source portion, which ionizes the hydrogen gas introduced into the interior thereof to generate hydrogen ions; an ion collector portion, which detects the amount of current of the hydrogen ions ejected from the ion source portion; and a re-inflow suppression structure, which suppresses the hydrogen gas that has changed from ions to uncharged gas in the ion collector portion from re-inflowing into the ion source portion.

[0011] [Effects of the Invention]

[0012] If this structure is used, the re-inflow suppression structure suppresses the re-ionization caused by the regenerated uncharged hydrogen that has changed from hydrogen ions to an uncharged state due to measurement flowing back toward the ion source, reducing its probability. Therefore, in practical terms, the background recovery time after the measurement can be sufficiently shortened. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic cross-sectional view showing the internal structure of an analysis tube of a 270-degree deflection angle type in a comparative example and explaining a reflow path of regenerated uncharged hydrogen toward the ion source portion.

[0014] Figure 2 This is a schematic cross-sectional view showing the internal structure of a 90-degree deflection angle type analysis tube in a comparative example and illustrating the reflow path of regenerated uncharged hydrogen toward the ion source. This is a data explanatory diagram showing an example of a processing scheme in the embodiment.

[0015] Figure 3 This is a schematic cross-sectional view showing the internal structure of an analysis tube of a 180-degree deflection angle type in a comparative example and explaining a reflow path of regenerated uncharged hydrogen toward the ion source portion.

[0016] Figure 4 It is a schematic diagram showing the entire leak detector in one embodiment of the present invention.

[0017] Figure 5 It is a schematic cross-sectional view showing the internal structure of the analysis tube in the embodiment.

[0018] Figure 6 This is a schematic cross-sectional view showing the internal structure of an analysis tube in another embodiment of the present invention.

[0019] [Explanation of Symbols]

[0020] X: Leak Detector

[0021] 100: Analysis tube

[0022] 1: Ion source

[0023] 13: Ion source slit

[0024] 14: First partition wall

[0025] 2: Ion collector

[0026] 3: Shell

[0027] 31: Middle slit

[0028] 32: Magnetic Field Space

[0029] 33: Middle partition

[0030] 71, 72, 73: Reinflow inhibition structures

[0031] 71a: Hydrogen retention components

[0032] 72a: Shelter Wall

[0033] 73a: Second exhaust port

[0034] S1: orbital of hydrogen ion

[0035] S2: Re-inflow path DETAILED DESCRIPTION

[0036] Before describing the embodiment of the present invention, an analysis tube of a comparative example will be described, and its problems will be described in detail. Figures 1 to 3 It is a figure which shows the analysis tube of a comparative example.

[0037] Figure 1 The illustrated analysis tube 100 is a magnetic field deflection type mass spectrometer, comprising: an ion source section 1, including an ion chamber (anode) 11, a filament 12 and an ion source slit 13; an ion collector section 2, including a sector-type deflection electrode 21, a magnetic compass pilot (MCP) or a Faraday cup plasma capture device 22 and an ion collector slit 23; a shell 3, which accommodates the ion source section 1 and the ion collector section 2 and forms a magnetic field space 32 with an intermediate slit 31 therebetween; and a magnet 4, which generates a magnetic field in a direction perpendicular to the paper surface.

[0038] The analysis tube 100 is always evacuated to a high vacuum state by a high vacuum pump connected to the exhaust port 51 , and hydrogen gas introduced into the analysis tube 100 is ionized in the ion chamber (anode) 11 by thermal electrons emitted from the filament.

[0039] The generated ions are ejected from the ion source slit 13 into the magnetic field space 32. According to Fleming's law, the ions draw circular arcs, but the radius thereof varies depending on the mass of the ions. Hydrogen ions draw a natural orbit with a mass number of 2.

[0040] The middle slit 31 is located on the hydrogen ion orbit S1, and only hydrogen ions pass through the middle slit 31 and reach the ion collector slit 23. Hydrogen ions are deflected by the electrostatic field at the sector deflection electrode 21 and return to neutral hydrogen after receiving free electrons in the ion trap 22.

[0041] At this time, free electrons are supplied in proportion to the number of hydrogen ions. A device that measures the supply of free electrons as current, converts it into a hydrogen leakage amount, and outputs it is called a hydrogen leak detector.

[0042] As a measurement procedure, the measurement is started by blowing hydrogen gas to the leakage test site of the test object until the inside of the analysis tube 100 becomes below a predetermined background.

[0043] However, in hydrogen leak detectors, the background is more difficult to stabilize than in helium leak detectors. Moreover, after measuring a large leak, for example, it takes a considerable amount of time for the background to recover to a level sufficient for the next measurement. Therefore, it is sometimes difficult to obtain sufficient measurement accuracy in a short period of time.

[0044] Regarding this phenomenon, the inventors of the present application believe that one of the reasons is that hydrogen takes more time to be discharged than helium. Therefore, after flowing into the analysis tube and being ionized, the detected hydrogen, that is, the hydrogen that has completed the measurement by receiving the supply of free electrons in the ion capture device and recovering from an ion to an uncharged state (hereinafter also referred to as regenerated uncharged hydrogen), returns to the ion source part and is ionized again, which occurs much more than helium.

[0045] Furthermore, in the case of a large leak, a large amount of air is sucked in, and water molecules contained in the air are decomposed into hydrogen ions during ionization, thereby generating more regenerated uncharged hydrogen than expected and flowing back into the ion source. This is also considered to be one of the reasons.

[0046] Therefore, the inventors of the present application conducted further research and studied through which path the regenerated uncharged hydrogen flows back into the ion source portion.

[0047] To facilitate understanding, the following will provide a somewhat qualitative description of the content.

[0048] This type of analysis tube has several types with different deflection angles. Figure 1 The analysis tube is a type with a deflection angle of 270 degrees, but there are other types, such as Figure 2 The type with a deflection angle of ninety degrees, or Figure 3 The 180-degree type analysis tube shown in the figure is shown in the figure.

[0049] Arriving at the ion capture device 22, receiving the supply of free electrons and changing from ions to a state of no charge, the regenerated uncharged hydrogen will not be affected by the magnetic field or electric field, but will diffuse linearly in all directions. Therefore, it is believed that the re-inflow path for the regenerated uncharged hydrogen to return to the ion source part 1 can be approximated by more than one straight line, including the situation where it collides with the inner surface (bottom surface, etc.) of the shell and then diffuses and rebounds in all directions. Each time a part of the hydrogen molecules traveling in the re-inflow path collides with the inner wall of the shell, a chemical reaction will occur and they will be trapped in the inner wall. Therefore, it is predicted that in the re-inflow path, the more rebounds there are, the less the amount (number) of hydrogen molecules returning to the ion source part will be.

[0050] Under this premise, Figures 1 to 3 In FIG. 1 , the reflow path S2 of the regenerated uncharged hydrogen is qualitatively indicated by arrows, and the thickness of the arrows indicates the amount of the regenerated uncharged hydrogen that reflows into the ion source 1 .

[0051] As mentioned above, Figure 2The structure shown is that although the analysis tube 100 is deflected at a 90-degree angle, most of the regenerated uncharged hydrogen directly reflows into the ion source 1. This is because there is no shield between the ion collector slit 23 and the ion source slit 13, and the reflow path S1 is formed by a straight line connecting them.

[0052] Figure 3 As can be seen from the analysis tube 100 with a deflection angle of 180 degrees, in this structure, hydrogen molecules that have collided with the inner wall of the housing at least once may flow back into the ion source 1 .

[0053] Figure 1 The analysis tube has a deflection angle of 270 degrees. It can be seen that in this structure, hydrogen molecules that have collided with the inner wall of the housing at least twice may flow into the ion source part 1 again.

[0054] According to the above, Figure 1 The structure can reduce the amount of hydrogen molecules that flow back into the ion source portion 1 to the greatest extent, but it can also be understood that the amount of hydrogen molecules that flow back into the ion source portion 1 cannot be sufficiently reduced in any way.

[0055] If the amount of hydrogen molecules flowing into the ion source 1 again in this manner is large, ionization is repeated and detected as current, which is considered to be a factor causing a considerable time to be required for background stabilization or background recovery as described above.

[0056] Next, one embodiment of the present invention will be described.

[0057] like Figure 4 As schematically shown, the leak detector X of this embodiment is connected to a test body W such as a vacuum container as a leakage inspection target via a test port P through piping.

[0058] This leak detector X includes three exhaust pumps: a low vacuum pump (e.g., an oil rotary pump) P3, a first high vacuum pump (e.g., a turbomolecular pump) P1, and a second high vacuum pump (e.g., a mechanical dry pump) P2; three valves V1, V2, and V3 for opening and closing the exhaust path; and an analysis tube 100. In some cases, P1 and P2 may consist of a single composite pump.

[0059] The analysis tube 100 is connected to a low vacuum pump P3 via a first high vacuum pump P1 , a second high vacuum pump P2 , and a valve V2 .

[0060] The vacuum container 100 is connected to a low vacuum pump P3 via a test port P and a valve V1 through piping.

[0061] The test specimen is leak-checked in the following order.

[0062] (1) Close valves V1 and V3 and open valve V2 to exhaust the inside of the analysis tube 100 to a predetermined background value using a first high vacuum pump P1, a second high vacuum pump P2, and a low vacuum pump P3 connected in series.

[0063] (2) After the background pressure in the analysis tube 100 drops to a predetermined value, the valve V2 is closed and the valve V1 is opened, and the interior of the test body W is evacuated (rough exhaust) by the rough vacuum pump P3.

[0064] (3) Close valve V1 and open valves V2 and V3 to start leak gas detection using the analysis tube 100 by blowing hydrogen (H2) to the leak test site of the test object W. At this time, the exhaust pumps P1 to P3 continue to operate.

[0065] (4) If there is a leak at the leak test site of the test body W, hydrogen gas enters the test body W. An amount of hydrogen gas proportional to its partial pressure enters the analysis tube 100 via valve V3 and turbomolecular pump P1. The hydrogen gas is detected by the analysis tube and the amount of leakage of the test body W is measured.

[0066] like Figure 5 As shown in its schematic side cross-sectional view, the analysis tube 100 includes a housing 3, an ion source portion 1 provided in the housing 3, an ion collector portion 2, and a magnetic field space 32 formed therebetween. Figure 1 The same reference numerals are used to denote corresponding components of the analysis tube described above.

[0067] The housing 3 is, for example, a metal (here, aluminum) housing in the shape of a rectangular parallelepiped having a front, back, left and right side surfaces, a top surface, and a bottom surface. For ease of explanation, the directions mentioned below, such as up, down, left, and right, are relative and do not represent absolute directions. The shape of the housing 3 is not limited to a rectangular parallelepiped.

[0068] The housing 3 has a first chamber 61 formed in the upper portion of the rear side, a second chamber 62 formed in the upper portion of the front side, and a third chamber 63 formed below the first chamber 61 and the second chamber 62. Furthermore, a first partition wall 14 is provided at the boundary between the first chamber 61 and the third chamber 63, and a second partition wall 24 is provided at the boundary between the second chamber 62 and the third chamber 63.

[0069] The ion source unit 1 includes an ion chamber (anode) 11 and a filament 12 disposed in a first chamber 61, and an ion source slit 13 penetrating a first partition wall 14. Electrons emitted from the filament ionize hydrogen molecules in the first chamber 61, and the resulting hydrogen ions are ejected from the ion source slit 13 toward the third chamber 63 below.

[0070] A magnetic field space 32 is formed in the third chamber 63. Specifically, a magnet 4 is disposed outside the third chamber 63, forming a magnetic field therein. Hydrogen ions emitted from the ion source 1 into the magnetic field space 32 are bent along a predetermined trajectory S1 by the magnetic field. An intermediate partition wall 33 is provided in the center of the third chamber 63. A middle slit 31 extends through the intermediate partition wall 33 at a location intersecting the trajectory S1. Since other ions have different trajectories than hydrogen ions, only hydrogen ions pass through the middle slit 31.

[0071] The ion collector unit 2 includes a sector-shaped deflection electrode 21 and an MCP or Faraday cup plasma trap 22, both located within the second chamber 62. The ion collector slit 23 extends through the second partition wall 24. The ion collector slit 23 is positioned on the hydrogen ion trajectory S1. Hydrogen ions emitted from the ion source slit 13 are deflected 180 degrees within the magnetic field 32 of the third chamber 63. After passing through the ion collector slit 23, they are further deflected 90 degrees by the sector-shaped deflection electrode 21 and irradiated onto the ion trap 22. In the ion trap 22, the hydrogen ions are freed and converted back into uncharged hydrogen molecules. The amount of hydrogen leakage is measured by monitoring the current flowing through the ion trap 22.

[0072] However, in this embodiment, three re-inflow suppressing structures 71 , 72 , and 73 are provided to suppress the re-inflow of hydrogen converted from ions to uncharged hydrogen (hereinafter also referred to as regenerated uncharged hydrogen) in the ion collector portion 2 into the ion source portion 1 .

[0073] The first reflow prevention mechanism 71 includes a hydrogen trapping member 71 a provided at a desired location inside the housing 3 .

[0074] The hydrogen trapping member 71a is made of a material with superior hydrogen adsorption properties compared to the material of the housing 3. Since the housing 3 is made of aluminum, stainless steel is used, which has superior hydrogen adsorption properties compared to aluminum. The hydrogen adsorption properties are determined by the difference between hydrogen adsorption and / or absorption and dissociation.

[0075] like Figure 5 As shown, the hydrogen trapping member 71 a is disposed on the bottom surface of the third chamber 63 (magnetic field space 32 ), the intermediate partition wall 33 , and the surface of the first partition wall 14 .

[0076] The hydrogen trapping component 71a provided on the bottom surface of the third chamber 63 is formed in a plate shape, and more specifically, can be interchangeably installed at the intersection of the straight line connecting the ion source slit 13 and the intermediate slit 31 (part of the re-inflow path S2) and the bottom surface of the third chamber 63.

[0077] The intermediate partition wall 33 and the first partition wall 14 include stainless steel plates as the hydrogen trapping member 71a, and they are detachable.

[0078] This structure can reduce the ratio of regenerated uncharged hydrogen rebounding on the inner surface of the housing 3 , the ion source slit 13 , or the intermediate slit 31 , thereby reducing the amount of regenerated uncharged hydrogen flowing back into the ion source 1 .

[0079] Furthermore, since the hydrogen trapping member 71a is configured to be detachable from the housing 3, even if the hydrogen adsorption performance deteriorates due to saturation or the like, the original performance can be easily restored by simply replacing the hydrogen trapping member 71a.

[0080] The hydrogen trapping member is not limited to stainless steel, and any single metal such as titanium, copper, or iron, or various alloys thereof, may be used as long as the hydrogen adsorption capacity is superior to that of aluminum.

[0081] The housing 3 itself may be formed of the hydrogen trapping member. The placement of the hydrogen trapping member is not limited to the above-described location, and may be, for example, the ion collector slit 23 .

[0082] The second reflow prevention mechanism 72 includes a shielding wall 72 a provided outside the hydrogen ion orbit S1 and on the reflow orbit S2 . The shielding wall 72 a is formed in a flange shape protruding from the outer peripheral edge of the ion source slit 13 in the first partition wall 14 toward the third chamber 63 .

[0083] By means of the above structure, the amount of regenerated uncharged hydrogen flowing into the ion source 1 can be reduced. The shielding wall 72a can also be provided outside the first partition wall 14. For example, Figure 6 As shown, it can be provided at the peripheral edge of the intermediate slit 31 in the intermediate partition wall 33, or it can be provided independently of the partition wall on the inflow track S2. Furthermore, the shield wall can be formed by the hydrogen trapping member, or a hydrogen trapping member can be attached to its surface.

[0084] The third re-inflow prevention mechanism 73 includes a second exhaust port 73a opened in the third chamber 63 (magnetic field space 32). The second exhaust port 73a is connected to the high vacuum pump P1 by piping.

[0085] This structure allows the regenerated uncharged hydrogen generated in the ion collector 2 to be discharged immediately before the ion source 1, thereby reducing the amount of regenerated uncharged hydrogen flowing into the ion source 1. Furthermore, heavy molecules such as other molecules (e.g., water molecules) can be actively discharged, thereby suppressing the generation of hydrogen ions caused by these molecules.

[0086] Furthermore, the second exhaust port 73a may be located at any location as long as it is closer to the ion collector portion 2 than the ion source portion 1. In the example described above, the second exhaust port 73a is located on the same surface (the back surface) as the surface of the housing 3 where the first exhaust port 51 is located to simplify piping. For example, the second exhaust port may be located closer to the ion collector portion 2 than the intermediate slit 31 of the third chamber 63, or may be located on the bottom or side surface of the housing 3. Furthermore, the second exhaust port may be located in the second chamber 62 where the ion collector portion 2 is located.

[0087] The features of the leak detector X are summarized as follows.

[0088] (1) The analysis tube 100 includes: an ion source portion 1 for ionizing hydrogen gas introduced therein to generate hydrogen ions; an ion collector portion 2 for detecting the amount of current of hydrogen ions ejected from the ion source portion 1; and reflow suppression structures 71, 72, and 73 for suppressing hydrogen that has been converted from ions to uncharged hydrogen in the ion collector portion 2 from reflowing into the ion source portion 1.

[0089] This structure can suppress the re-ionization of regenerated neutral hydrogen, which has been converted from hydrogen ions to neutral during measurement, by flowing back toward the ion source 1. This allows for a significantly faster background recovery time than conventional helium methods. Furthermore, hydrogen is abundant and inexpensive compared to helium, thus avoiding concerns about resource depletion and price increases.

[0090] (2) The re-inflow suppression structure 71 includes the hydrogen trapping member 71 a provided on the inner surface of the analysis tube 100 .

[0091] With this structure, the ratio of regenerated uncharged hydrogen that bounces off the inner surface of the analysis tube 100 can be reduced, and the amount of regenerated uncharged hydrogen that flows back into the ion source unit 1 due to the rebound can be reduced.

[0092] (3) The housing 3 constituting the analysis tube 100 is made of aluminum, and the hydrogen trapping member 71a is made of stainless steel.

[0093] If this structure is used, for example, by making the shell 3 from easily processed aluminum on one side and attaching a stainless steel plate to the required part of the inner surface on the other side, the reflow suppression structure 71 can be economically constructed without imposing a large burden on manufacturing.

[0094] (4) The hydrogen retention component 71a is arranged on at least any one of the inner surface of the magnetic field space 32 between the ion source part 1 and the ion collector part 2, the surface of the first partition wall 14 forming the ion source slit 13 for ejecting hydrogen ions from the ion source part 1, and the surface of the intermediate partition wall 33 forming the intermediate slit 31 arranged on the orbit S1 of hydrogen ions in the magnetic field space 32.

[0095] With this structure, the amount of regenerated uncharged hydrogen that flows back into the ion source section 1 can be reduced more effectively.

[0096] (5) The re-inflow suppression structure 72 includes a shielding wall 72 a provided on the re-inflow path S2 and outside the orbit S1 of the hydrogen ions. The re-inflow path S2 is represented by a straight line connecting the ion collector section 2 and the ion source section 1 including rebounds in the inner surface of the analysis tube.

[0097] With this structure, the shielding wall 72 a can prevent the regenerated uncharged hydrogen from flowing toward the ion source portion 1 .

[0098] (6) The ion source unit 1 includes the ion source slit 13 for emitting hydrogen ions, and the shielding wall 72 a is provided so as to stand upright from the peripheral edge of the ion source slit 13 .

[0099] With this structure, the shielding wall 72 a can be easily provided by modifying the existing ion source slit 13 .

[0100] (7) The shielding wall 72a or the surface portion of the shielding wall 72a includes the hydrogen trapping member 71a.

[0101] With this structure, the amount of regenerated uncharged hydrogen flowing into the ion source section 1 can be drastically reduced due to the synergistic effect of the shielding wall 72 a and the hydrogen trapping member 71 a .

[0102] (8) The ion source portion 1 is provided with the first exhaust port 51 , and the re-inflow suppressing structure 73 includes the second exhaust port 73 a provided on the ion collector portion 2 side relative to the ion source portion 1 .

[0103] With this structure, the regenerated uncharged hydrogen before returning to the ion source 1 can be efficiently exhausted from the second exhaust port 73a, thereby reducing the amount of regenerated uncharged hydrogen flowing into the ion source 1. In addition, heavy molecules such as other molecules (e.g., water molecules) can be actively exhausted to suppress the generation of hydrogen ions caused by them.

[0104] (9) The first exhaust port 51 and the second exhaust port 73 a are provided on the same surface of the housing 3 constituting the analysis tube 100 .

[0105] With this structure, the piping structure connected to the exhaust port 51 and the exhaust port 73a can be simplified.

[0106] Furthermore, the present invention is not limited to the above embodiment. For example, the present invention can be applied to analysis tubes with a 90-degree or 180-degree deflection angle, achieving the same effects. The reflow suppression structures may also utilize any one or two of the three described above, rather than all three.

[0107] In addition, the present invention can be modified in various ways without departing from the spirit and scope of the present invention.

Claims

1. A leak detector that introduces hydrogen gas leaked from a test body into an analysis tube for detection, characterized in that: The analysis tube includes an ion source portion that ionizes hydrogen introduced into the ion source portion to generate hydrogen ions; an ion collector portion that detects the current of the hydrogen ions emitted from the ion source portion; and a reflow suppression structure that suppresses the reflow of hydrogen that has been converted from ions to uncharged hydrogen in the ion collector portion into the ion source portion.

2. The leak detector according to claim 1, wherein The re-inflow suppression structure includes a hydrogen retaining component provided on the inner surface of the analysis tube.

3. The leak detector according to claim 2, wherein The shell constituting the analysis tube is made of aluminum, and the hydrogen trapping member is made of stainless steel.

4. The leak detector according to claim 2 or 3, wherein The hydrogen retention component is arranged on at least any one of the inner surface of the magnetic field space between the ion source part and the ion collector part, the surface of the first partition wall forming an ion source slit for ejecting hydrogen ions from the ion source part, and the surface of the middle partition wall forming an middle slit arranged on the orbit of hydrogen ions in the magnetic field space.

5. The leak detector according to any one of claims 1 to 3, wherein The re-inflow suppression structure includes a shielding wall provided on a re-inflow path outside a trajectory of hydrogen ions. The re-inflow path is represented by a straight line connecting the ion collector and the ion source, including a rebound on an inner surface of an analysis tube.

6. The leak detector according to claim 5, wherein The ion source portion includes an ion source slit for emitting hydrogen ions, and the shielding wall is provided so as to stand upright from a peripheral edge portion of the ion source slit.

7. The leak detector according to claim 5, wherein The shield wall or a surface portion of the shield wall includes a hydrogen trapping feature.

8. The leak detector according to any one of claims 1 to 3, wherein The ion source portion is provided with a first exhaust port, and the re-inflow suppression structure includes a second exhaust port provided on a side of the ion collector portion relative to the ion source portion.

9. The leak detector according to claim 8, wherein The first exhaust port and the second exhaust port are provided on the same surface of a housing constituting the analysis tube.

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