JP3847458B2 - Small magnetic field deflection type mass spectrometer tube and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a small-sized magnetic field deflection type mass spectrometer tube used for a leak detection apparatus and the like, and a manufacturing method thereof.
[0002]
[Prior art]
Conventionally, the inside of a hollow leak detection target is evacuated to a vacuum, and a probe gas such as helium gas is sprayed on the peripheral surface of the target, and when there is a leak in the target, the leak gas such as helium gas is hollow. Since it penetrates into the interior, it is detected by a leak detection device connected to the hollow portion of the object to detect the presence of the leak.
[0003]
In order to analyze the leaked gas from the object, the leak detection device includes a small magnetic field deflection type mass spectrometer tube a having a configuration as shown in FIGS. 1 and 2. It is as follows. In a small casing b of the mass spectrometer tube a, a grid (electron collector) c for ionizing gas atoms and gas molecules such as probe gas introduced from the inside of the object and a thermoelectron emission filament d are provided. The amount of specific ions selected by an ionization chamber f including an ionization means and an extraction electrode e for extracting the ions, and a magnetic field deflection analyzer g including a permanent magnet outside the casing from the extracted ions When an ion detection chamber i provided with an ion collector h for detecting a gas leaks into the ionization chamber f and enters the ionization chamber f, gas molecules and the like are generated by the impact of thermoelectrons from the thermoelectron emission filament d. Is ionized and extracted to the ion detection chamber i by the extraction electrode e. Then, the magnetic field deflection analyzer g applies specific ions based on the equation of r = (1.44 × 10 ⁻⁴ √Mu × V) / B (r: turning radius, Mu: mass number, B: magnetic flux density). The selected ions are incident on the ion collector h through the collector slit j. The amount of ions incident on the ion collector h is measured by an ion current measuring device k. The voltage between the grid c and the filament d is adjusted by a voltage regulator l, the acceleration voltage of the grid c is adjusted by an ion acceleration power source m, and the kind of ions reaching the ion collector h is adjusted by this voltage adjustment. The composition of the leaked gas can also be analyzed. n is a filament power supply.
[0004]
As shown in FIG. 2, the casing b includes five ion source mounting flanges o, an ion source pipe p to which the ion source mounting flange o is mounted, an intermediate ion deflection flat pipe q, an ion collector pipe r, and an ion collector mounting flange s. A plate t with an ionization means (ion source) attached and a plate v with an ion collector u attached to each flange o, s are screwed together and formed by welding the members and enabling frequent maintenance inspection. . A magnetic field deflection analyzer g made of a permanent magnet having a U-shaped cross section is mounted and fixed on the outer periphery of the ion deflection flat pipe q. w is an exhaust port provided with a flange provided on the side of the ion source pipe p, and the exhaust port w is connected to the hollow interior of the leakage detection object.
[0005]
[Problems to be solved by the invention]
Each member constituting the casing b is made of SUS, and has flanges o and s having a diameter of about 50 mm and a center axis having a length of about 180 mm. The members are welded and integrally joined after shaping. . Since the ion deflection flat pipe q is a flat pipe different from the circular ion source pipe p and the ion collector pipe r, it is troublesome to manufacture separately. However, in such a manufacturing method, there are many welding points, due to thermal distortion due to welding, deformation due to moving or lifting before the weld cools, and due to the combination of manufacturing errors and distortion in the welding process, etc. , Angle accuracy and length accuracy are severely degraded. In addition, since the processing accuracy of the casing b is not stable, the sensitivity and resolution of the individual analysis tubes are greatly different particularly in a magnetic field deflection type mass analysis tube having a small turning radius.
[0006]
An object of the present invention is to provide a small magnetic field deflection type mass spectrometer tube which has uniform sensitivity and resolution, has high processing accuracy and is suitable for mass production.
[0007]
[Means for Solving the Problems]
In the present invention, within the casing, it provided an ionization chamber and an ion detection chamber, the ionization means and ion ion detection of ions by electron impact gas atoms and gas molecules of the probe gas, etc. introduced into this to the ionization chamber An ion collector for extracting a specific ion amount selected from the extracted ions by a magnetic field deflection type analyzer comprising a permanent magnet outside the detection chamber. A magnetic field deflection type mass spectrometer having a central axis of the ionization chamber and the ion detection chamber bent according to an ion rotation radius by the magnetic field deflection type analyzer, wherein the magnetic field deflection type is provided in the material block of the casing. Two circular holes having a central axis according to the ion turning radius of the analyzer are formed by cutting, and are connected to both circular holes inside the intersection of the central axes. By cutting forming a flat hole which, by making the casing in machining machined from a block of material of the casing, and so as to achieve the above object. This is also advantageous in production. The outer peripheral surface of the intersecting portion of the block may be cut flat to form a mounting portion for the magnetic field deflection analyzer, and if necessary, the casing may be made of two blocks of material. As a manufacturing method thereof, a method in which two circular holes having intersecting angle axes according to the ion rotation radius are formed in a block by cutting and then a flat through hole communicating with both circular holes is formed by cutting. .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. In FIG. 3, reference numeral 1 is a small casing, 2 is an ionization chamber, 3 is an ion detection chamber, 4 is an ionization means provided in the ionization chamber 2, Reference numeral 5 denotes an extraction electrode for drawing out ions generated by the ionization means to the ion detection chamber 3. The structure of the ionization means 4 is the same as that of the prior art. The ionization means 4 has a grid 6 and a thermoelectron emission filament 7 and enters from an exhaust port 8 connected to the hollow interior of a leakage detection object formed on the side wall of the ionization chamber 2. Gas atoms such as a probe gas and gas molecules are ionized by applying an electron bombardment with thermoelectrons emitted from the filament 7, and the generated ions are extracted to the ion detection chamber 3 by the extraction electrode 5. A magnetic field deflection type analyzer 9 made of a fan-shaped permanent magnet is attached to the outside of the ion detection chamber 3 to apply a deflection magnetic field to the extracted ions, and only selected specific ions are collected through the collector slit 10 as an ion collector. 11 is incident. An ion current detector is connected to the ion collector 11 as in the prior art.
[0009]
The dimension of the casing 1 is about 160 mm in the length of the bent central axis, and the inner diameter of the ionization chamber 2 and the ion detection chamber 3 is about 40 mm. Conventionally, the casing is made of SUS pipe or flange as described above. It was manufactured by shaping and welding, but in the present invention, a block of casing material is manufactured by machining, so that a small magnetic field deflection type with uniform sensitivity, resolution, high processing accuracy and mass productivity. A mass spectrometer tube was obtained. The casing material block is preferably made of aluminum or a material that is relatively soft and has good machinability, such as aluminum.
[0010]
A manufacturing example of the casing for the 90 ° deflection type is as shown in FIG. 4, and the surplus portion 13 in the bending range of the square block 12 according to the ion rotation radius is, for example, 0.1 mm or less in length and 0.1 degrees or less in angle. An L-shaped bending material 14 is produced by cutting with an accurate NC automatic lathe or the like, and the bending corner portion 15 is cut 15a. Then, the front and back of the corner portion 15 are cut out to cut out the flat mounting portion of the magnetic field deflection analyzer 9, and the ion turning radius is followed by the cutting tool 18 such as an end mill from each end face 16, 17 of the bending material 14. Circular holes 19 and 20 having central axes 21 and 22 are formed by cutting. These circular holes 19, 20 are cut to a depth that does not reach the flat corner portion 15, and are deep in each circular hole where the intersections of both central axes 21, 22 exist, that is, inside the corner portion 15. A flat through hole 23 that communicates these circular holes is formed by cutting. As shown in FIG. 3, the thickness of the casing 1 is such that the plate 24 to which the ionization means 4 and the extraction electrode 5 are attached, the plate 25 to which the collector slit 10 and the ion collector 11 are attached, and the magnetic field deflection analyzer 9. Thick enough to be screwed and left when cutting. FIG. 5 shows the outer shape of the casing 1.
[0011]
When the machining of the casing 1 is completed, the plates 24 and 25 and the magnetic field deflection analyzer 9 can be attached as they are and assembled into the magnetic field deflection type mass analysis tube. By cutting, it is possible to mass-produce magnetic deflection type mass spectrometers with uniform sensitivity and resolution without welding distortion or deformation.
[0012]
Two blocks of the casing material may be used. In this case, as shown in FIG. 6, the outer periphery of one end of one block 12a is flattened for mounting the magnetic field deflection type analysis tube 9. A flange portion 26 for cutting and connecting another block 12b is formed by cutting, a flat through hole 23 is formed by cutting on a surface 27 having the flange portion 26, and an end surface 28 intersecting the surface 27 is formed. A circular hole 20 communicating with the through hole 23 was formed, and a circular hole 19 penetrating through the other block 12b was formed, and the open end of the circular hole was screwed and joined to the flange portion 26. In this case, as shown in FIG. 7, both the blocks 12a and 12b are mechanically joined by the flanges. Therefore, the length accuracy and the angle accuracy are more accurate than the welding, and the assembly is facilitated. Also in this case, a material having good cutting properties such as aluminum is used for the block material, and plates 24 and 25 provided with ionization means and the like are attached to the end portions of the circular holes 19 and 20 as shown in FIG. A magnetic field deflection type analyzer 9 is attached to the corner portion 15. FIG. 8 shows the outer shape of the casing 1.
[0013]
The mass spectrum obtained by the 90 ° deflection type magnetic field deflection type mass spectrometer having the shaving casing of the present invention shown in FIGS. 3 and 4 is as shown in FIG. The state of peak separation is sharper than the mass spectrum of the 90 ° deflection type mass analysis tube having a casing manufactured by conventional welding shown in FIG. 10, and the mass analysis tube using the casing of the present invention is cut out. The resolution was good. The conventional mass spectrometer tube had a deflection angle reduced by 2 degrees at the time of manufacture, and its correction was difficult. Further, when only the helium spectrum was measured using the mass spectrometer tube having the machined casing of the present invention and the mass spectrometer tube having the conventional welding casing, the results shown in FIGS. 11 and 12 were obtained. FIG. 11 shows a helium spectrum of a mass spectrometer tube using the casing of the present invention, and its peak appears on the low energy side of about 10 eV compared to the conventional one of FIG. The energy of the helium peak calculated from the above formula is an actual measurement value of 0.210 T of the magnetic field strength and a rotation radius of 2 cm to about 213 V, and this value is not a conventional one, but the helium peak obtained with the mass spectrometer of the present invention. It corresponds to the ion energy of. The reason is that the manufacturing accuracy of the deflection angle is low with the conventional one, and the deflection angle is manufactured to be about 2 degrees smaller as shown in FIG. This is because the deflection angle of the present invention is almost exactly 90 °, and the energy position at which the helium ion peak appears is almost as calculated.
[0014]
In the above example, the analyzer 9 gives a 90 ° deflection to the ions and the axis of the ionization chamber 2 and the axis of the ion detection chamber 2 intersect at 90 °. The present invention can also be applied to those having a deflection.
[0015]
【The invention's effect】
As described above, according to the present invention, the casing of the magnetic deflection type mass spectrometer tube is manufactured by cutting out the casing material block, so that processing accuracy is higher than that of the conventional one, and uniform sensitivity and resolution can be obtained. As a result, the homogeneity is improved, and a small magnetic field deflection type mass analysis tube having good mass productivity can be obtained.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a conventional small magnetic field deflection type mass spectrometer tube. FIG. 2 is a plan view of a specific configuration of FIG. 1. FIG. 3 is a cut plan view showing an embodiment of the present invention. FIG. 5 is an external perspective view of the casing of FIG. 4. FIG. 6 is an explanatory view of another embodiment of the present invention. FIG. 7 is a small magnetic field deflection type using the casing of FIG. FIG. 8 is a perspective view of the outer appearance of the casing of FIG. 6. FIG. 9 is a diagram of the mass spectrum of the small magnetic field deflection type mass analysis tube of FIG. 3. FIG. Diagram of mass spectrum of analysis tube [FIG. 11] Diagram of helium spectrum of small magnetic deflection type mass spectrometer tube of FIG. 3 [FIG. 12] Diagram of helium spectrum of conventional small magnetic field deflection type mass spectrometer tube [FIG. [Explanation of the deflection angle of a conventional small magnetic field deflection type mass spectrometer]
DESCRIPTION OF SYMBOLS 1 Casing, 2 Ionization chamber, 3 Ion detection chamber, 4 Ionization means, 5 Extraction electrode, 9 Magnetic field deflection type analyzer, 11 Ion collector, 12 * 12a * 12b block, 19 * 20 Circular hole, 21 * 22 Central axis, 23 flat through hole, 26 flange,

Claims (4)

An ionization chamber and an ion detection chamber are provided in the casing. In the ionization chamber, ionization means for ionizing gas atoms and gas molecules such as probe gas introduced into the ionization chamber by electron bombardment and drawing out the ions to the ion detection chamber The ion detection chamber is provided with an ion collector for detecting the amount of specific ions selected from the extracted ions by a magnetic field deflection analyzer consisting of a permanent magnet outside the detection chamber, In a magnetic field deflection type mass spectrometer in which the central axes of the ionization chamber and the ion detection chamber are bent in accordance with the ion rotation radius of the magnetic field deflection type analyzer, the ion of the magnetic field deflection type analyzer is placed on the casing material block. Two circular holes having a central axis according to the turning radius are formed by cutting, and are flattened to communicate with both circular holes inside the intersection of the central axes. By cutting a hole, magnetic deflection mass spectrometer tube, characterized in that the casing produced by the machining machined from a block of material of the casing. 2. The magnetic field deflection type mass spectrometer tube according to claim 1, wherein an outer peripheral surface of the intersecting part of the block is cut flat to form an attachment part of the magnetic field deflection type analyzer . An ionization chamber and an ion detection chamber are provided in the casing. In the ionization chamber, ionization means for ionizing gas atoms and gas molecules such as probe gas introduced into the ionization chamber by electron bombardment and drawing out the ions to the ion detection chamber The ion detection chamber is provided with an ion collector for detecting the amount of specific ions selected from the extracted ions by a magnetic field deflection analyzer consisting of a permanent magnet outside the detection chamber, In a magnetic field deflection type mass spectrometer in which the central axes of the ionization chamber and the ion detection chamber are bent in accordance with the ion rotation radius of the magnetic field deflection type analyzer, two blocks of the casing material are prepared. The outer periphery of one end of the block is cut flat and a flange for connecting the other one is formed, and a flat through hole is formed on the surface having the flange. A circular hole communicating with the flat through hole is formed on the end surface intersecting with the surface, and a circular hole penetrating the other one block is formed, and the open end of the circular hole is defined as the flange portion. A magnetic field deflection type mass spectrometer tube characterized in that the casing is made from two blocks of material of the casing by screwing and joining to the casing. An ionization chamber and an ion detection chamber are provided in the casing. In the ionization chamber, ionization means for ionizing gas atoms and gas molecules such as probe gas introduced into the ionization chamber by electron bombardment and drawing out the ions to the ion detection chamber The ion detection chamber is provided with an ion collector for detecting the amount of specific ions selected from the extracted ions by a magnetic field deflection analyzer consisting of a permanent magnet outside the detection chamber, In a magnetic field deflection mass spectrometer tube in which the central axes of the ionization chamber and ion detection chamber are bent in accordance with the ion rotation radius of the magnetic field deflection analyzer, a block of the casing material is prepared, and the block is made by cutting. After forming two circular holes having an axis of crossing angle according to the ion rotation radius, a flat through hole communicating with both circular holes is formed by cutting. Method for producing a magnetic deflection mass spectrometer tube, characterized in that to produce a pacing.

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