JP7327229B2 - Protective nets, turbomolecular pumps and mass spectrometers - Google Patents

Description

The present invention relates to protective nets, turbomolecular pumps and mass spectrometers.

Between the inlet flange of the turbomolecular pump and the chamber of the equipment, a net-like member called a protective net or "protective net" is placed to prevent foreign matter from falling into the turbomolecular pump. ) are arranged (see, for example, Patent Document 1). The mesh roughness of the protective net is set according to the size of foreign matter that may fall, and mesh openings large enough to prevent the foreign matter from falling into the pump are formed throughout the net.

A turbo-molecular pump is used to evacuate a mass spectrometer, and a single turbo-molecular pump can be used to evacuate an exhaust chamber containing an ion delivery unit (also called an ionization unit) and an exhaust chamber containing a mass spectrometer. A differential pumping structure that pumps air may be employed. For example, the exhaust ports of a plurality of exhaust chambers are arranged so as to be adjacent to each other, and the plurality of exhaust ports are connected to the intake port of the turbo-molecular pump so as to exhaust simultaneously. In this case, an exhaust chamber pressure of about 10 ² to 10 ^-2 Pa is required for the ion sending section, while an exhaust chamber pressure of about 10 ^-3 to 10 ^-4 Pa is required for the mass spectrometry section.

Japanese Patent No. 6261507

By the way, the exhaust chamber in which the ion sending unit is housed contains parts that require maintenance or repair, and maintenance or repair may be performed while the turbomolecular pump is connected. Therefore, a fine-mesh protective net is required to prevent parts and the like from falling into the turbomolecular pump during operation. Since the fineness of the mesh is determined by the size of the falling object, if the predicted falling object is small, the mesh may become too fine, which may interfere with evacuation of the mass spectrometer.

A protective net according to an aspect of the present invention is a protective net provided at a connection portion between a plurality of exhaust chambers and a turbo-molecular pump connected to the plurality of exhaust chambers, wherein the protective net has a plurality of mesh openings. In the plurality of mesh-like regions, the mesh roughness of one of the mesh-like regions is different from that of the other mesh-like regions.
A turbomolecular pump according to an aspect of the present invention is a turbomolecular pump that evacuates a plurality of exhaust chambers of a mass spectrometer, and the protective net is provided at the pump inlet.
A mass spectrometer according to an aspect of the present invention comprises: a first exhaust chamber housing an ion sending unit for sending ions to a mass spectrometry unit; a second exhaust chamber housing the mass spectrometry unit; and a protective net according to claim 1 provided so as to face the exhaust port of the second exhaust chamber and the exhaust port of the second exhaust chamber, wherein the protective net is provided corresponding to the first exhaust chamber. and a second mesh region provided corresponding to the second exhaust chamber, wherein the mesh roughness of the first mesh region is the same as that of the second mesh region. finer than thin.

According to the present invention, it is possible to achieve both prevention of falling objects and vacuum performance.

FIG. 1 is a diagram showing an example of a mass spectrometer. FIG. 2 is a cross-sectional view taken along line AA of FIG. FIG. 3 is a cross-sectional view showing an example of a schematic configuration of a turbo-molecular pump. FIG. 4 is a plan view of the protective net. FIG. 5 is a diagram illustrating openings formed in a mesh region. FIG. 6 is a diagram showing another shape of the opening. FIG. 7 is a diagram for explaining the case where the opening areas of the two mesh-like regions are substantially the same. FIG. 8 is a diagram showing Modification 1, and is a diagram showing the bottom side of the apparatus housing. FIG. 9 is a diagram showing a CC cross section of FIG. FIG. 10 is a diagram showing Modification 2. As shown in FIG.

FIG. 1 is a schematic diagram showing an example of a mass spectrometer using a turbomolecular pump in an exhaust system. The mass spectrometer 70 shown in FIG. 1 is a gas chromatograph mass spectrometer (GC mass spectrometer) as an example. a portion 73; The ion sending part 72 and the mass spectrometry part 73 are evacuated by the turbomolecular pump 1 . A protective net 5 is provided at the intake port 121 a of the intake port flange 121 of the turbo-molecular pump 1 . As shown in FIG. 4, which will be described later, the protective net 5 has two types of mesh areas: a coarse mesh area (mesh area) and a fine mesh area (mesh area). The present invention is applicable not only to gas chromatograph mass spectrometers, but also to liquid chromatograph mass spectrometers, inductively coupled plasma mass spectrometers, and the like. In either case, the mass spectrometry part and the ion sending part for sending ions to the mass spectrometry part are evacuated by a single turbomolecular pump.

Two differential exhaust chambers 741 and 742 partitioned by a wall portion 740 are formed adjacent to each other in the device housing 74 . Differential exhaust chambers 741 and 742 are individually provided with exhaust ports 741a and 742a. The ion sending section 72 is provided in the differential evacuation chamber 741 , and the mass analysis section 73 is provided in the differential evacuation chamber 742 .

The gas chromatograph section 71 is provided with a column oven 711 , a column (capillary column) 712 and an injector 713 . Although not shown, the injector 713 has a sample vaporization chamber for heating and vaporizing the liquid sample, and the sample vaporization chamber is supplied with a carrier gas (He gas or H ₂ gas) at a predetermined flow rate. A liquid sample injected into the sample vaporization chamber by a microsyringe or the like is vaporized in the sample vaporization chamber and sent into the column 712 along with the carrier gas flow. Column 712 is heated to moderate temperature by column oven 711 .

The vaporized sample (ie sample gas) moves through the column 712 with the carrier gas. Although the sample gas contains a plurality of components, the speed at which each component travels through the column 712 is different. As a result, each component is temporally separated, reaches the outlet of the column 712 , and is guided from the sample introduction tube 714 to the ion delivery section 72 .

The ion delivery unit 72 ionizes the sample gas and delivers it to the mass spectrometry unit 73 , and includes an ionization chamber 721 and an ion transport optical system 722 . Molecules of the gas component guided from the sample introduction pipe 714 to the ion delivery section 72 are introduced into the ionization chamber 721 . Molecules of the gas component introduced into the ionization chamber 721 are ionized by thermal electrons emitted from a filament 725 provided in the ionization chamber 721 . The generated ions are ejected from the ionization chamber 721 by the ejection electrode 726 to which a positive voltage is applied.

Ions emitted from the ionization chamber 721 are converged by an ion transport optical system 722 having a linear optical axis and guided to a mass spectrometer 73 . The mass spectrometer 73 has a quadrupole mass spectrometer 731 , an ion lens 732 and a detector 733 . Ions converged by the ion transport optical system 722 are guided to a quadrupole mass spectrometer 731 . A voltage obtained by superimposing a DC voltage and a radio frequency voltage (RF voltage) is applied to the quadrupole mass spectrometer 731, and only ions having a mass corresponding to the applied voltage pass through the quadrupole mass spectrometer 731. do. Ions passing through a quadrupole mass spectrometer 731 are converged by an ion lens 732 and detected by a detector 733 .

A differentially pumped chamber 741 provided with a quadrupole mass spectrometer 731, an ionization chamber 721 and an ion transport optical system 722, and a differentially pumped chamber 742 provided with an ion lens 732 and a detector 733, It is partitioned by a wall portion 740 in which a passage hole 740a is formed. The differential pumping chambers 741 and 742 are pumped by one turbomolecular pump 1 .

FIG. 2 is a view showing the AA section of FIG. 1, and the turbomolecular pump 1 is connected to the device housing 74 so that the inlet flange 121 faces the respective outlets 741a and 742a. The exhaust port 741 a and the exhaust port 742 a are provided adjacent to each other across a wall portion 740 provided between the differential exhaust chambers 741 and 742 and face the intake port of the intake port flange 121 . The first mesh area 50a of the protection net 5 provided at the intake port 121a of the intake flange 121 faces the exhaust port 741a, and the second mesh area 50b of the protection net 5 is opposed to the exhaust port 742a. facing each other.

In order to improve the detection accuracy of the quadrupole mass spectrometer 731 and the detector 733, the differential evacuation chamber 742 is preferably highly vacuumed. Therefore, a wall portion 740 having a hole 740a formed between the differential pumping chamber 741 and the differential pumping chamber 742 is provided, and one turbo-molecular pump 1 operates to 742a is set as a differential pumping system for pumping each.

FIG. 3 is a cross-sectional view showing an example of a schematic configuration of the turbo-molecular pump 1. As shown in FIG. The turbomolecular pump 1 includes a turbopump section P1 having turbine blades and a Holweck pump section P2 having spiral grooves as exhaust function sections. The turbo pump section P1 is composed of a plurality of stages of rotor blades 30 formed on the pump rotor 3 and a plurality of stages of fixed blades 20 arranged on the base 2 and pump casing 12 side. On the other hand, the Holweck pump section P2 provided on the exhaust downstream side of the turbo pump section P1 is composed of a cylindrical section 31 formed in the pump rotor 3 and a stator 21 arranged on the base 2 side. A spiral groove is formed on the inner peripheral surface of the cylindrical stator 21 .

The pump rotor 3 is fastened to a shaft 10 that is rotationally driven by the motor 4 . A rotor unit comprising a shaft 10 and a pump rotor 3 is rotatably supported by a permanent magnet magnetic bearing 6 using permanent magnets 6a and 6b and a ball bearing 8 which is a rolling bearing. When the rotating unit is rotationally driven by the motor 4, the ionization chamber 721 and the differential evacuation chamber 742 connected to the inlet flange 121 are evacuated. Although not shown, an auxiliary pump is connected to the exhaust port 2a provided on the exhaust side of the turbo-molecular pump 1, and the gas exhausted by the turbo-molecular pump 1 is exhausted to the outside of the turbo-molecular pump 1 by the auxiliary pump. be done.

As shown in FIGS. 1 and 3, the turbo-molecular pump 1 is fixed to a connecting portion provided on the bottom wall 74b of the apparatus housing 74 with fastening bolts (not shown) or the like. The protection net 5 is provided in the connection area between the differential pumping chambers 741 and 742 and the turbomolecular pump 1 . In the examples shown in FIGS. 1 and 3, a protective net 5 is provided on the turbomolecular pump 1 side in the connection area. The gap dimension d between the upper surface of the protective net 5 provided on the inlet flange 121 and the surface of the bottom wall 74b is as small as about 1 to 2 mm.

FIG. 4 is a plan view of the protection net 5 viewed from the device housing 74 side of the mass spectrometer 70. As shown in FIG. The protective net 5 provided on the inlet flange 121 of the turbo-molecular pump 1 prevents parts and the like from falling into the turbo-molecular pump 1 during maintenance of the ion delivery section 72 provided in the differential exhaust chamber 741. It is provided to The protective net 5 is provided with a first fine mesh region 50a having a plurality of small openings 501 and a second coarse mesh region 50b having a plurality of large openings 502. . A boundary between the mesh region 50a and the mesh region 50b is provided at a position facing the wall portion 740 that partitions the differential exhaust chamber 741 and the differential exhaust chamber 742 .

In this embodiment, the protection net 5 is formed by forming openings in a thin metal plate by etching. However, the present invention is not limited to the protective net 5 having such a configuration, and can be applied to a protective net formed by weaving metal wires.

As shown in FIG. 2, the protective net 5 has a fine mesh region 50a at a position facing the exhaust port 741a of the differential exhaust chamber 741, and faces the exhaust port 742a of the differential exhaust chamber 742. A coarse mesh region 50b is arranged at the position. As described above, since the gap dimension d (see FIG. 3) between the upper surface of the protective net 5 and the surface of the bottom wall 74b of the apparatus housing 74 is as small as about 1 to 2 mm, the exhaust port of the differential exhaust chamber 741 is closed during maintenance. When a screw, a part, or the like drops from 741a into the mesh area 50a, there is no possibility that the dropped object will move toward the mesh area 50b.

The mesh roughness of the mesh areas 50a and 50b is an index representing the size of a falling object that can be blocked by the mesh areas 50a and 50b. The fine mesh region 50a can block smaller falling objects than the coarse mesh region 50b. As a concrete definition of mesh roughness, for example, the mesh roughness is expressed by the size of the opening area, and in the case of similar polygonal or circular openings, the length of the corresponding side or the size of the radius can express the roughness of the mesh. In this specification, the quantity defined as follows is used as an index of "roughness of mesh".

(Definition of mesh roughness)
5(a) and 5(b) are diagrams for explaining the definition of "mesh roughness" in this specification. FIG. 5(a) is a diagram illustrating openings 501 formed in the mesh region 50a. FIG.5(b) is a figure explaining a falling object. The shape and size of the opening 501 are set based on the size of parts, foreign matter, etc. that may fall during maintenance of the ion sending unit 72 . For example, the size of the opening 501 is set so that the smallest falling object in the differential exhaust chamber 741 does not pass through. If the smallest falling object is the bolt 300 as shown in FIG. 5B, the size of the opening 501 is set so that the head portion 301 of the bolt 300 does not pass through the opening 501 .

For example, when the radius of the head portion 301 is Rb, if the shortest distance R1 from the center O of the regular hexagonal opening 501 to the opening edge portion 510 is set as R1<Rb, the head portion 301 is open. Since it does not pass through 501, it is possible to prevent the bolt 300 from falling into the pump. That is, considering only whether the bolt 300 passes through the opening 501, the bolt 300 can be regarded as equivalent to the falling spherical object B having the radius Rb. From the viewpoint of the effective pumping speed for the differential pumping chamber 741, it is preferable to increase the conductance of the mesh region 50a as much as possible within the range where the falling spherical object B can be prevented from passing. Therefore, in the range where R1<Rb is satisfied, R1 should be set slightly smaller than Rb.

By the way, when the shape of the opening is a regular polygon or a circle like the opening 501, the shortest distance from the center O of the opening 501 to the opening edge 510 and the radius Rb are compared to determine whether the bolt 300 can pass through. It is possible to determine whether or not However, in the case of irregularly shaped openings such as the openings 501a in the peripheral portion of the mesh region 50a in FIG. is not clearly defined.

Therefore, in this specification, taking irregular-shaped openings into account, the "mesh roughness" of the mesh-like regions 50a and 50b is expressed using the quantity "the radius of the maximum sphere that can pass through the openings." I decide to In the examples shown in FIGS. 5(a) and 5(b), the sphere with radius R1 corresponds to the "maximum sphere that can pass through the opening". It is possible to prevent the bolt 300 corresponding to the falling spherical object B of Rb from falling from the opening 501 . By using such "the radius of the maximum sphere that can pass through the opening", even if the opening has an irregular shape like the opening 501a and the center of the opening is unknown, the mesh areas 50a and 50b can be "corrected". "Mesh roughness" can be evaluated.

By the way, as shown in FIG. 4, the openings 501 and 502 included in the mesh areas 50a and 50b are basically regular hexagons, but the openings 501a and 502a around the mesh areas 50a and 50b are regular hexagons. The opening has a shape in which a part of is missing. Therefore, the "radius of the maximum passable sphere" of the openings included in the mesh region 50a is different between the openings 501 and 501a. The same applies to the openings 502, 502a of the mesh region 50b. Therefore, when comparing the openings of the mesh region 50a and the openings of the mesh region 50b, if the openings 501 and 502 are compared, it can be determined that the openings of the mesh region 50a are larger and coarser. When the opening 501 and the opening 502a are compared, it is judged that the mesh area 50b is larger and coarser.

In this way, when a plurality of types of openings with different sizes are included in each of the mesh regions 50a and 50b, the "radius of the maximum passable sphere" cannot be determined by comparing some of the openings. It will not be fixed. Therefore, considering the case where multiple types of openings with different sizes are included, the definition of "mesh roughness" is "the average value for multiple openings of the radius of the maximum sphere that can pass through the openings". , will be explained using that definition. That is, an average value (referred to as a first average value) of the maximum spherical radii of all the openings 501 including the openings 501a of the mesh region 50a is obtained, and all the openings 502 including the openings 502a of the mesh region 50b are calculated. The average value (referred to as the second average value) of the maximum sphere radii of the mesh regions 50a and 50b is compared by comparing the first average value and the second average value to determine the mesh roughness of the mesh regions 50a and 50b. Determine large or small (ie, coarse or fine).

When the openings included in the mesh regions 50a and 50b are composed only of the openings 501 and 502, instead of "the average value of the radii of the maximum sphere that can pass through the openings for a plurality of openings" The "roughness of the mesh" may be defined as "the radius of the maximum sphere that can pass through the opening". However, in both of the mesh-like regions 50a and 50b, since the ratio of the openings having a shape in which a part of a regular hexagon is missing is small, it is The "average value" is approximately equal to the "radius of the maximum sphere that can pass through the openings" for the openings 501,502.

In addition, when the shape of the openings included in each of the mesh regions 50a and 50b is one type and similar shapes such as the openings 501 and 502, "the average of the radii of the maximum spheres that can pass through the openings for a plurality of openings value” is the same as the “radius of the maximum sphere that can pass through the opening”. Also, instead of the "radius of the maximum sphere that can pass through the opening", the "area of the opening", the "length of the corresponding side of the opening", etc. may be used as the definition of the "roughness of the mesh". Regardless of which definition is used, the magnitude relationship of "mesh roughness" is the same as in the case of "radius of maximum sphere that can pass through opening".

As described above, with respect to the mesh roughness of the mesh region 50a, by setting the "average value of the maximum radii of the spheres that can pass through the openings for a plurality of openings" to be smaller than the radius Rb of the fallen spherical object B, , the bolt 300 can be prevented from falling through the opening 501 . On the other hand, the mesh roughness of the mesh region 50b is set, for example, as follows.

The parts (quadrupole mass spectrometer 731, ion lens 732, detector 733, etc.) accommodated in the differential pumping chamber 742 are generally not maintained by the user. is determined mainly from the viewpoint of evacuation performance. A differential evacuation chamber 742 accommodating the quadrupole mass spectrometer 731 and the detector 733 requires a vacuum of about 10 ⁻³ to 10 ⁻⁴ Pa. Therefore, the conductance of the mesh region 50b, that is, the size of the openings 502 is set so that the effective exhaust velocity at the exhaust port 742a becomes an effective exhaust velocity that enables a pressure of 10 ^-3 to 10 ^-4 Pa.

For example, it is preferable to set the area of the opening 502 to be twice or more that of the opening 501 . In this case, the ratio of the side lengths of the regular hexagonal openings 502 and 501 is √2:1. Expressed using the shortest distance described above, this corresponds to setting the shortest distance of the opening 502 to be 1.4 (≈√2) times or more the shortest distance R1 of the opening 501 . That is, it is preferable to set the radius of the maximum sphere that can pass through the opening 502 to 1.4 times or more the radius of the maximum sphere that can pass through the opening 501 .

In the example shown in FIG. 4, the shape of the openings 501 and 502 is a regular hexagon. The value R1 or the radius R1 of the maximum sphere that can pass through the opening 501 is set such that R1<Rb with respect to the aforementioned radius Rb, as in the case of the regular hexagonal opening.

Also, as shown in FIGS. 6A and 6B, even in the case of horizontally long polygons (hexagons and rectangles), the radius R1 of the maximum sphere that can pass through the opening 501 is R1<Rb. The size of the opening 501 is set as follows. FIG. 6(c) shows a square opening 501c having the same area as the opening 501 in FIG. 6(b). The radius R1c of the maximum sphere that can pass through the opening 501c is R1c/R1=√2. As described above, if the opening area is the same, a horizontally long polygon can prevent even a smaller falling object from falling into the pump than a regular polygon.

In FIG. 7, the area of the rectangular openings 501 formed in the mesh region 50a and the area of the square openings 502 formed in the mesh region 50b are the same, and the radius of the maximum sphere that can pass through the openings is set to be the same. FIG. 4 is a diagram showing a case where the ratio of R1 and R2 is set to about 1:2.3; In this case, the areas of the openings 501 and 502 are the same, but the radius R1 of the maximum sphere that can pass through the opening 501 is smaller than the radius R2 of the maximum sphere that can pass through the opening 502. FIG. That is, as the definition of "roughness of the mesh", "the radius of the maximum sphere that can pass through the opening" is more suitable than the "opening area". The mesh roughness is determined to be coarser than that of the mesh region 50b.

The radius R1 is set so as to block a falling object equivalent to a sphere B with a radius Rb that satisfies Rb>R1 (≈R2/2.3). Since the openings 501 and 502 have the same area, the mesh regions 50a and 50b have approximately the same conductance. However, since a horizontally long falling object such as the falling object B1 passes through the opening 501, the opening 501 should be made a square smaller than the opening 502, even if it means sacrificing the decrease in conductance. is preferred.

(Modification 1)
8 and 9 are diagrams showing Modification 1 of the above-described embodiment. FIG. 8 is a view of the bottom wall 74b of the device housing 74 as seen from the turbomolecular pump side. Also, FIG. 9 is a diagram showing a CC cross section of FIG. In the above-described embodiment, as shown in FIG. 3, the protection net 5 is provided on the turbomolecular pump 1 side (that is, the inlet flange 121) in the connection area. It was arranged on the 74 side. A circular recess 744 is formed in the bottom wall 74b of the device housing 74, and exhaust ports 741a and 742a are formed in the bottom surface 744b of the recess 744. As shown in FIG. The protective net 5 is screwed to the bottom surface 744b. The turbo-molecular pump 1 fixed to the bottom wall 74b of the apparatus housing 74 is arranged such that the intake port 121a faces the recess 744 of the bottom wall 74b, as shown in FIG.

As shown in FIG. 8, the protective net 5 is arranged such that the mesh region 50a formed with the small openings 501 faces the exhaust port 741a, and the mesh region 50b formed with the large openings 502 faces the exhaust port 742a. , it is fixed to the bottom surface 744 b of the recess 744 . Thus, the protective net 5 is arranged so that the fine mesh region 50a faces the exhaust port 741a of the differential exhaust chamber 741, and the coarse mesh region 50b faces the exhaust port 742a of the differential exhaust chamber 742. need to be placed. In the case of the configuration in which the protection net 5 is fixed to the device housing 74 side as in the first modification, the phase of the intake flange 121 when fixing the turbo-molecular pump 1 is adjusted according to the relationship between the turbo-molecular pump 1 and the surrounding devices. You can freely decide accordingly. For example, the mounting rotational phase of the intake flange 121 can be freely determined in accordance with the positional relationship between the exhaust port 2a and the auxiliary pump and so as not to interfere with surrounding devices.

On the other hand, in the configuration in which the protection net 5 is provided on the turbo-molecular pump 1 side, the attachment rotational phase when fixing the intake flange 121 to the bottom wall 74b of the apparatus housing 74 is determined to be a predetermined phase. Therefore, it is necessary to design the positional relationship between the exhaust port 2a and the auxiliary pump and the layout of the peripheral devices in accordance with the mounting rotation phase of the turbopump.

(Modification 2)
FIG. 10 is a diagram showing Modification 2 of the above-described embodiment. In Modification 2, an ISO standard ISO-LF flange is adopted as the inlet flange 121 of the turbomolecular pump 1 . In the ISO-LF flange, a center ring 200 provided with an O-ring seal 201 is used as a sealing member. The center ring 200 is sandwiched between the inlet flange 121 and the bottom surface 74b of the device housing 74, and the inlet flange 121 is fixed to the bottom surface 74b by a plurality of clamps 202. As shown in FIG. The protective net 5 is fitted on the inner peripheral side of the center ring 200 . The center ring 200 is set so that the mesh region 50a of the protective net 5 faces the exhaust port 741a, and the mesh region 50b faces the exhaust port 742a.

It will be appreciated by those skilled in the art that the exemplary embodiments and variations described above are specific examples of the following aspects.

[1] A protective net according to one aspect is a protective net provided at a connection portion between a plurality of exhaust chambers and a turbo-molecular pump connected to the plurality of exhaust chambers, the protective net having a plurality of openings. has a plurality of mesh-like regions formed in a mesh-like manner, and among the plurality of mesh-like regions, the mesh roughness of one of the mesh-like regions is different from that of the other mesh-like regions.

For example, in the protective net 5 shown in FIG. 4, the mesh area 50a has finer mesh roughness than the mesh area 50b. Therefore, as shown in FIG. 2, by connecting the turbo-molecular pump 1 to the apparatus housing 74 so that the portion of the mesh region 50a faces the exhaust port 741a of the differential exhaust chamber 741, the difference in maintenance and the like can be reduced. The protective net 5 can prevent falling objects from the dynamic exhaust chamber 741 to the turbomolecular pump 1 . In addition, since the mesh region 50b is set to be coarser than the mesh region 50a, it is possible to suppress the decrease in the effective pumping speed for the differential pumping chamber 742 due to the provision of the protective net 5. . That is, by using the protective net 5, it is possible to achieve both prevention of objects falling on the turbomolecular pump 1 and vacuum performance of the differential exhaust chamber 742. FIG.

Although the intake port 121a of the turbo-molecular pump 1 is connected to the two differential exhaust chambers 741 and 742 in the above embodiment, it may be connected to three or more exhaust chambers. For example, when connecting to three exhaust chambers, the protection net 5 provided at the intake port 121a is provided with three mesh regions having different mesh roughnesses. Then, the protective net is arranged so that each mesh region faces the exhaust port of the corresponding exhaust chamber.

[2] In the protective net described in [1] above, the mesh roughness of the mesh region is defined as the average value of the radii of the maximum spheres that can pass through the openings. For example, in the protective net 5 shown in FIG. 4, the average value of the radii of the maximum spheres in the mesh region 50a is set smaller than the average value of the radii of the maximum spheres in the mesh region 50b. As a result, even when a plurality of types of openings with different shapes are included as in the mesh regions 50a and 50b shown in FIG. can be done.

[3] A turbo-molecular pump according to one aspect is a turbo-molecular pump that evacuates a plurality of exhaust chambers of a mass spectrometer, wherein the protective net described in [1] and [2] above is provided at the pump inlet. It is

[4] In the turbo-molecular pump described in [3] above, the pump intake port accommodates a first exhaust chamber that accommodates an ion delivery unit that delivers ions to a mass analysis unit, and the mass analysis unit. The protection net is connected to the second exhaust chamber, and includes a first mesh area provided corresponding to the first exhaust chamber and a second mesh area provided corresponding to the second exhaust chamber. and the mesh coarseness of the first mesh region is finer than the mesh coarseness of the second mesh region.

For example, in the turbomolecular pump 1 shown in FIG. 3, the protective net 5 is attached to the inlet flange 121 . When connecting the turbo-molecular pump 1 to the apparatus housing 74 of the mass spectrometer 70 , the mesh region 50 a having finer mesh is arranged so as to face the exhaust port 741 a of the differential exhaust chamber 741 of the mass spectrometer 73 . connect to. The mesh roughness of the mesh region 50a is finely set so that the average value of the radii of the largest spheres can prevent objects from falling into the turbomolecular pump 1, thereby preventing falling objects from falling into the turbomolecular pump 1. can be prevented. As a result, it is possible to achieve both the prevention of objects falling into the turbo-molecular pump and the vacuum performance of the differential evacuation chamber 742 .

[5] In the turbomolecular pump described in [4] above, when the mesh roughness of the mesh region is defined as the average value of the radii of the maximum spheres that can pass through the openings for the plurality of openings, The average value of the second mesh area is set to 1.4 times or more of the average value of the first mesh area. By setting in this way, an effective pumping speed for the differential pumping chamber 742 can be ensured.

[6] A mass spectrometer according to an aspect includes: a first exhaust chamber housing an ion sending unit that sends ions to a mass spectrometry unit; a second exhaust chamber housing the mass spectrometry unit; and a protective net according to claim 1 provided so as to face the exhaust port of the exhaust chamber and the exhaust port of the second exhaust chamber, wherein the protective net is provided corresponding to the first exhaust chamber. and a second mesh region provided corresponding to the second exhaust chamber, wherein the mesh roughness of the first mesh region is equal to that of the second mesh region. finer than the roughness of As a result, it is possible to prevent objects from falling into the vacuum pumps (for example, turbo-molecular pumps) connected to the respective exhaust ports of the first and second exhaust chambers, and to improve the vacuum performance of the second exhaust chamber.

[7] In the mass spectrometer according to [6] above, the mesh roughness of the mesh region is defined as an average value of the radii of the maximum spheres that can pass through the openings, with respect to the plurality of openings. The average value of the two mesh areas is set to be 1.4 times or more the average value of the first mesh area. By setting in this way, it is possible to secure an effective exhaust speed for the second exhaust chamber.

Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other aspects conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention. For example, in the above-described embodiment, a turbo-molecular pump equipped with a permanent magnet magnetic bearing was explained as an example, but a turbo-molecular pump using a 5-axis control type magnetic bearing or a turbo-molecular pump using a mechanical bearing similarly applicable.

REFERENCE SIGNS LIST 1 turbomolecular pump 5 protective net 50a, 50b mesh region 70 mass spectrometer 72 ion delivery unit 73 mass spectrometer 74 apparatus housing 121 inlet flange 121a Intake port 200 Center ring 501, 501a, 501c, 502, 502a Opening 741, 742 Differential exhaust chamber 741a, 742a Exhaust port

Claims (6)

A protective net provided at a connection portion between a plurality of exhaust chambers of a mass spectrometer and a turbomolecular pump connected to the plurality of exhaust chambers,
The protective net has a plurality of mesh regions in which a plurality of openings are formed in a mesh shape,
The plurality of exhaust chambers includes a first exhaust chamber that houses an ion sending unit that sends ions to a mass spectrometer, and a second exhaust chamber that houses the mass spectrometer,
The plurality of mesh areas includes a first mesh area provided corresponding to the first exhaust chamber and a second mesh area provided corresponding to the second exhaust chamber,
The protective net , wherein the mesh roughness of the first mesh region is finer than the mesh roughness of the second mesh region . In the protective net according to claim 1,
The protective net, wherein the mesh roughness of the mesh region is defined as an average value for the plurality of openings of the radius of a maximum sphere that can pass through the openings. A turbomolecular pump for evacuating a plurality of exhaust chambers of a mass spectrometer,
3. A turbomolecular pump, wherein the protective net according to claim 1 or 2 is provided at the pump inlet. In the turbomolecular pump according to claim 3 ,
When the mesh roughness of the mesh region is defined by the average value of the maximum sphere radii that can pass through the openings for the plurality of openings,
The turbomolecular pump, wherein the average value of the second mesh region is set to be 1.4 times or more the average value of the first mesh region. a first exhaust chamber in which an ion sending section for sending ions to the mass spectrometry section is accommodated;
a second exhaust chamber in which the mass spectrometer is accommodated;
and a protection net according to claim 1, which is provided so as to face the exhaust port of the first exhaust chamber and the exhaust port of the second exhaust chamber,
The protective net is arranged such that the first mesh region corresponds to the first exhaust chamber, and the second mesh region corresponds to the second exhaust chamber.
Mass spectrometer. In the mass spectrometer according to claim 5 ,
The mesh roughness of the mesh region is defined as an average value for the plurality of openings of the radius of the maximum sphere that can pass through the openings,
The mass spectrometer, wherein the average value of the second mesh area is set to be 1.4 times or more the average value of the first mesh area.

Images