JP2007311111A - Tof type mass spectrometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a TOF type mass spectrometer with light weight and low cost while maintaining accuracy of the interval and arrangement location of electrode plates to curve ion beams. <P>SOLUTION: Fan-type electrode parts 1-4 are constituted of a pair of first plates 30 which are installed and fixed so as to interpose an inner metallic plate 42 and an outer metallic plate 43 of thin plate shape and an ion optical system 8 is constituted of a pair of second plates 32 to interpose the pair of first plates 30 of the fan-type electrode parts 1-4. Since the first plates 30 are fixed to the second plates 32 by a plurality of rods 12 which penetrate the pair of first plates 30 and are installed and fixed to the second plates 32, the ion optical system 8 is made light weight and low cost while maintaining the interval between the inner metallic plate 42 and the outer metallic plate 43 and loction accuracy in the ion optical system 8 of the fan-type electrode parts 1-4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a TOF mass spectrometer that performs mass analysis of an ion beam that draws a circular orbit.

  In recent years, time-of-flight mass spectrometers (hereinafter abbreviated as TOF mass spectrometers) have been widely used for mass spectrometry because they can measure ion energy with high resolution. The TOF type mass spectrometer obtains ion velocity, and hence energy, from ion flight time. At this time, the longer the ion flight distance, the higher the resolution.

  Here, in order to maintain a high resolution and to make the size compact, the TOF type mass spectrometer makes the ions draw a circular orbit and increases the flight distance of the ions with a small volume. At this time, the TOF mass spectrometer is provided with a plurality of electrode plates that bend the ion trajectory. This electrode plate forms a uniform electric field on the ion trajectory so that the ions fly around the orbit (see Non-Patent Document 1, for example).

On the other hand, the detector for detecting ions is about several centimeters in size, whereas the total flight distance of ions is as long as about 10 m. In order to guide these ions from the ion source to the detector with a small loss while drawing a curved trajectory, the electrostatic field strength formed by the electrode plates and the mutual position of the arranged electrode plates must be highly accurate. Is done.
Japan Journal of Mass Spectrum Association (J. Mass Spectrom. Soc. Jpn.), Vol. 51, No. 2 (Vol. 51, N0.2), 2003, p. 349-353

  However, according to the background art described above, the electrode plate and the casing in which the electrode plate is disposed are heavy and costly. That is, the interval between the electrode plates forming the electrostatic field requires an accuracy of about several tens of μm, and the mutual position of the plurality of electrode plates requires an accuracy of about several hundreds of μm. In order to maintain this accuracy regardless of external impact or the like, the electrode plates have high strength, and these electrode plates are surrounded and supported by a strong housing.

  However, imparting high strength to the electrode plate and the housing makes the electrode plate and the housing thick and made of a hard material, which causes an increase in cost as well as weight. For example, the weight including the electrode plate and the housing is about 200 kg, and the material cost alone is several million yen.

For these reasons, it is important how to realize a light and inexpensive TOF type mass spectrometer while maintaining the accuracy of the distance between the electrode plates for bending the ion beam and the arrangement position.
The present invention has been made in order to solve the above-described problems of the background art, and is a light and inexpensive TOF type mass spectrometer while maintaining the accuracy of the interval and arrangement position of electrode plates for bending an ion beam. The purpose is to provide.

  In order to solve the above-described problems and achieve the object, a TOF type mass spectrometer according to the first aspect of the present invention includes a fan-shaped electrode unit that forms an electrostatic field that bends an orbit of an ion beam, and a plurality of the fan-shaped electrodes. An ion optical system having an electrode portion disposed in the middle of the orbit and having the orbit as a circular orbit, wherein the sector electrode has one of two orthogonal sides Two rectangular metal plates facing each other while being curved, and a pair of plate-like first plates that sandwich and fix the two rectangular metal plates from the direction of the other side of the two sides In the ion optical system, the plurality of fan-shaped electrode portions are arranged in parallel such that the arrangement direction of the first plates forming a pair is orthogonal to the orbital surface of the orbit, and the plurality A first plate forming a pair of A pair of second plates arranged at positions sandwiched from the direction and a rod-like rod that passes through the pair of first plates and is fixed to the pair of second plates. .

  In the first aspect of the present invention, the fan-shaped electrode portion includes two rectangular metal plates facing each other while one side of two orthogonal sides is curved, and the two rectangular metal plates. The ion optical system has a pair of plate-shaped first plates that are sandwiched and fixed from the direction of the other side, and the ion optical system has a plurality of fan-shaped electrode portions, and the arrangement direction of the first plates forming a pair circulates. A parallel arrangement is made in parallel with the orbital plane of the orbit, and a pair of second plates and a pair are arranged at positions sandwiching the plurality of first plates arranged in parallel from the arrangement direction. It has a rod-like rod that passes through the first plate and is fixed to the second plate in a pair.

  A TOF type mass spectrometer according to the invention described in claim 2 is the TOF type mass spectrometer according to claim 1, wherein the ion optical system includes two rods for each of the sector electrode parts. It is characterized by providing.

According to the second aspect of the present invention, the sector electrode portion is prevented from rotating with respect to the ion optical system.
The TOF mass spectrometer according to the invention described in claim 3 is the TOF mass spectrometer according to claim 1 or 2, wherein the fan-shaped electrode portion includes the rectangular metal plate in the array direction and the rectangular metal plate. An insulator is provided between the first plates.

In the invention according to claim 3, the insulation between the rectangular metal plate and the first plate in the arrangement direction is made by the insulator.
According to a fourth aspect of the present invention, there is provided a TOF mass spectrometer according to any one of the first to third aspects, wherein the ion optical system is arranged in the array direction. A spacer is provided between one plate and the second plate.

According to the fourth aspect of the present invention, the position of the first plate between the second plates is changed according to the length of the spacer.
The TOF mass spectrometer according to the invention described in claim 5 is the TOF mass spectrometer according to any one of claims 1 to 4, wherein the ion optical system includes a plurality of the same shapes. A fan-shaped electrode part is provided.

In the invention according to the fifth aspect, the number of manufacturing steps of the fan-shaped electrode portion is reduced.
The TOF mass spectrometer according to the invention described in claim 6 is the TOF mass spectrometer according to any one of claims 1 to 5, wherein the ion optical system includes four fan-shaped electrodes. It comprises a part.

  In the invention according to the sixth aspect, the circular orbit is efficiently achieved.

  According to the present invention, the accuracy of the interval between two rectangular metal plates is determined by the accuracy of the mounting position on the plate-shaped first plate, and the positional accuracy of the paired first plates in the ion optical system. Is determined by the accuracy of the mounting position of the rod and the rod on the second plate, so that the weight of the ion optical system is maintained while maintaining the accuracy of the distance between the two rectangular metal plates and the positional accuracy in the ion optical system. Can be made light in weight determined by the rectangular metal plate, the first plate, the second plate, and the rod, and the material cost can be reduced.

The best mode for carrying out a TOF mass spectrometer according to the present invention will be described below with reference to the accompanying drawings. Note that the present invention is not limited thereby.
First, the configuration of the TOF mass spectrometer 10 according to the present embodiment will be described with reference to FIG. FIG. 1 is a cross-sectional view showing the configuration of a TOF mass spectrometer 10 according to the present embodiment. The TOF type mass spectrometer 10 includes an ion optical system 8, an ion source 20, and a housing 9. Here, the housing 9 and the ion source 20 form a vacuum container, and the inside is in a high vacuum state.

  The ion source 20 uses an ionized gas as a sample, forms an ion beam 22 in which the gas is focused and accelerated, and injects the ion beam into the ion optical system 8. The ion optical system 8 includes four sector electrode portions 1 to 4 and a detection portion 17 and will be described in detail later. The fan-shaped electrode portions 1 to 4 cause the ion beam 22 to fly while drawing an 8-shaped trajectory indicated by a dotted line in FIG. 1 to separate and detect elements having different masses contained in the ion beam 22. The ion beam 22 circulates in an x-shaped orbit on the xz-axis surface of the xyz coordinate axis shown in FIG. 1 while moving in the y-axis direction orthogonal to the xz-axis surface for each lap. Draw the trajectory.

  The detection unit 17 uses a microchannel plate or the like, and detects the ion beam 22. The detection unit 17 is different from the ion source 20 in the y-axis direction, and detects the ion beam 22 obtained by multiplying the 8-shaped trajectory in a spiral manner. Note that the xyz coordinate axes depicted in FIG. 1 are the same as the xyz coordinate axes shown in the drawings described later, and indicate the positional relationship between the drawings.

  FIG. 2 is a perspective view of the ion optical system 8 viewed from an oblique direction. The ion optical system 8 includes four fan-shaped electrode portions 1 to 4, a pair of second plates 32, eight rods 12, and six spacers 51 to 53 and 62 to 64. The rod 12 and the spacers 62 to 64 not shown will be shown later. The pair of plate-like second plates 32 are arranged so that the plate surfaces face each other in the y-axis direction. The four sector electrode portions 1 to 4 are arranged in parallel between the pair of plate-like second plates 32 via the spacers 51 to 53 and 62 to 64.

  Here, the fan-shaped electrode portions 1 to 4 are arranged at the four corners of the second plate 32 where the ion beam 22 bends the orbit with a slight shift in the y-axis direction. The spacers 51 to 53 and 62 to 64 have different lengths in the y-axis direction for each of the sector electrode portions 1 to 4 by the magnitude of this shift.

  Between the paired second plates 32, two parallel rods 12 are stretched for each of the sector electrode portions 1 to 4. These rods 12 are fixed to the second plates 32 that pass through the rod holes provided in the sector electrode portions 1 to 4 and the spacers 51 to 53 and 62 to 64 and make a pair. Further, the second plate 32 forming a pair is fixed to the housing 9, and consequently the fan-shaped electrode portions 1 to 4 fixed to the second plate 32 forming a pair, and the spacers 51 to 53 and 62 to 64 are also provided. The arrangement is fixed to the housing 9.

  FIG. 3 is a perspective view of the sector electrode portion 1 as viewed from an oblique direction. In addition, since the sector electrode parts 1-4 have the completely same structure, only the structure of the sector electrode part 1 is shown as a representative example. The sector electrode portion 1 includes a pair of first plates 30, an inner metal plate 42 and an outer metal plate 43 that are rectangular metal plates, a shunt 34, and a spacer 35. A Mazda plate (not shown) exists between the inner metal plate 42 and the outer metal plate 43 which are rectangular metal plates. The Mazda plate will be described later using a cross-sectional view. Here, the inner metal plate 42 and the outer metal plate 43 have a cylindrical structure in which a plate-like metal plate is curved so that the xz cross section forms a fan shape. Then, a voltage is applied between the inner metal plate 42 and the outer metal plate 43, and the ion beam 22 input during this time is output by changing the trajectory by a predetermined angle.

  In this orbit change, the ion beam 22 moves not only in the xz plane, but also in the z-axis direction, and has an 8-shaped orbit in the xz plane as shown in FIG. Then, a spiral orbit is drawn and moved while shifting the orbital plane in the y-axis direction.

  The plate-like first plate 30 opposed in the y-axis direction is formed by interposing an inner spacer 42 and an outer metal plate, which are rectangular metal plates, through an insulating spacer 35 made of glass or the like in the opposed space. 43 is fixed by screwing or the like. At this time, the distance between the opposing surfaces of the inner metal plate 42 and the outer metal plate 43 is constant with high accuracy depending on the mounting position provided on the first plate 30, for example, the screw hole position. A shunt 34 is present at the end where the ion beam 22 is input / output between the inner metal plate 42 and the outer metal plate 43, and the ion beams 22 on the orbits having different positions in the y-axis direction are mixed with each other. Is preventing.

  Further, the first plate 30 has a plurality of rod holes 13. The rod hole 13 exists at the same position in the xz-axis plane of the two opposing first plates 30 and has the same cross-sectional shape as the short-axis cross section of the rod 12 described above. The rod hole 13 penetrates the rod 12 in the y-axis direction, and the relative position of the rod 12 and the first plate 30 that makes a pair is fixed in the xz plane. Since the rod 12 is fixed to the second plate 32 by screwing or the like, the first plate 30 is fixedly disposed on the second plate 32 by the rod 12.

  Further, when the cross section of the rod 12 in the short axis direction and the hole cross section of the rod hole 13 are circular, the relative movement of the rod 12 and the first plate 30 due to rotation around the y axis direction can be achieved with only one rod 12. A change in position can occur. In order to prevent this rotation, two or more rods 12 are used to prevent a change in relative position due to rotation. In FIG. 3, four rod holes 13 are provided in the first plate 30 including a spare.

  FIG. 4 is a cross-sectional view showing a CC ′ cross section of the sector electrode portion 1 shown in FIG. The inner metal plate 42 and the outer metal plate 43 which are rectangular metal plates have a fan-shaped cross section, and form an electrostatic field in a space between the metal plates. Then, the ion beam 22 incident between the inner metal plate 42 and the outer metal plate 43 is bent along the fan-shaped surface under the influence of the force of the electrostatic field, and is output from the other end surface. Note that the second plate 32 and the first plate 30 of the fan-shaped electrode portions 1 to 4 have cylindrical holes punched out within a range where there is no problem in strength for weight reduction.

  FIG. 5 is a cross-sectional view showing a DD ′ cross section of the sector electrode portion 1 shown in FIG. 3. A Mazda plate 36 is disposed between the inner metal plate 42 and the outer metal plate 43 extending in the y-axis direction with a predetermined interval. The Mazda plate 36 prevents the ion beam 22 from diffusing in the y-axis direction and moves the ion beam 22 in the y-axis direction. The ion beam 22 is positioned at an intermediate position of the Mazda plate 36 that is repeatedly arranged in the y-axis direction. Here, the spot-like ion beams 22 arranged in the y-axis direction indicate the passing positions of the ion beam 22 moving in the y-axis direction in a spiral shape while drawing an 8-shaped orbit in the xz plane. .

  FIG. 6 is a cross-sectional view showing an AA ′ cross section of the ion optical system 8 in which the sector electrode portions 1 to 4 shown in FIG. 2 are combined. Each of the sector electrode portions 1 to 4 is fixed to the paired second plate 32 by the two rods 12. Spacers 62 to 64 indicated by hidden lines (dotted lines) in the figure are arranged between the fan-shaped electrode portions 2 to 4 and the second plate 32, and the two rods 12 are passed through each spacer 62 to 64. It is done. The fan-shaped electrode unit 1 is directly connected to the second plate 32 without arranging a spacer.

  Here, the spacers 51 to 53 and 62 to 64 shown in FIGS. 2 and 6 have different lengths in the y-axis direction. The spacer 51 is placed between the paired second plates 32 where the fan-shaped electrode portions 1 exist, and the spacers 52 and 62 are placed between the paired second plates 32 where the fan-shaped electrode portions 2 exist. The spacers 53 and 63 are placed between the paired second plates 32 where the fan-shaped electrode portions 3 exist, and the spacer 64 is placed between the paired second plates 32 where the fan-shaped electrode portions 4 exist. The length of the spacer in the y-axis direction is set such that the spacer 51 alone, the spacers 52 and 62 added, the spacers 53 and 63 added, and the spacer 64 alone are equal. The positions of the fan-shaped electrode portions 1 to 4 existing between the paired second plates 32 in the y-axis direction are equal to each other by a length corresponding to the moving distance of the ion beam 22 moving spirally in the y-axis direction. The position is shifted. The second plate 32 has a cylindrical hole punched out in a range where there is no problem in strength for weight reduction.

  FIG. 7 is a cross-sectional view showing the BB ′ cross section of the ion optical system 8 in which the sector electrode portions 1 to 4 shown in FIG. 2 are combined. FIG. 7 illustrates a cross section of the sector electrode portion 1, the sector electrode portion 4, the paired second plate 32, and the spacers 51 and 64. Furthermore, in the sector electrode part 1 and the sector electrode part 4, the cross section of the 1st plate 30, the rod 12, the inner side metal plate 42, the outer side metal plate 43, and the Mazda plate 36 which make a pair is illustrated. Further, FIG. 7 shows the trajectory of the ion beam 22 moving in the y-axis direction in a spiral shape, and the positions of the fan-shaped electrode portions 1 and 4 in the y-axis direction. The position of the fan-shaped electrode portions 1 and 4 in the y-axis direction differs by a length that generally matches the moving distance of one cycle of the ion beam 22 due to the spacer 51 and the spacer 64 inserted at different positions in the y-axis direction.

  Further, in FIG. 7, the two rods 12 that fix the fan-shaped electrode portion 1 pass through the rod hole 13 and the spacer 51 of the first plate 30 that makes a pair, and are fixed to the second plate 32 that makes a pair. The two rods 12 that fix the fan-shaped electrode unit 4 pass through the rod hole 13 and the spacer 64 of the first plate 30 that makes a pair, and are fixed to the second plate 32 that makes a pair. Is shown.

  Next, functions and operations of the ion optical system 8 according to the present embodiment will be described. The ion optical system 8 causes the ion beam 22 to draw an 8-shaped trajectory that moves in a spiral shape. At this time, the distance between the inner metal plate 42 and the outer metal plate 43 and the attachment position, which determine the trajectory of the ion beam 22, are set with high accuracy.

  As shown in FIG. 3, the inner metal plate 42 and the outer metal plate 43, which are rectangular metal plates, are mounted on the opposed flat plate-like first plates 30. The distance between the inner metal plate 42 and the outer metal plate 43 in the vicinity of the first plate 30 is determined only by the position where the inner metal plate 42 and the outer metal plate 43 are attached to the first plate 30, and can be within an error of about several tens of micrometers.

  However, the inner metal plate 42 and the outer metal plate 43 are reduced in thickness for weight reduction and are weak in strength against torsion. Therefore, the two first plates 30 facing each other may be displaced in relative positions within the facing xz-axis planes, possibly causing distortion. Further, the fan-shaped electrode portions 1 to 4 including the inner metal plate 42 and the outer metal plate 43 are arranged on the xz-axis surface as shown in FIG. 2, and it is necessary to increase the accuracy of the relative position.

  Here, the two opposing first plates 30 have two rods 12 penetrating the same opposing rod hole 13. Thereby, the two opposing first plates 30 are fixed at positions where the relative positions of the xz-axis surfaces are the same as the hole positions of the rod holes 13. The rod 12 extends to the two opposing second plates 32 and is fixed to the mounting position of the two opposing second plates 32. As a result, the first plate 30 arranged on the second plate 32 has a high accuracy in which the relative position in the xz-axis plane is determined by the mounting position for fixing the rod 12. The inner metal plate 42 and the outer metal plate 43 attached to 30 are also assumed to have high positional accuracy. The relative position of the first plate 30 arranged in the xz-axis plane can be within an error of about 100 to 200 μm.

  On the other hand, the ion optical system 8 including the inner metal plate 42, the outer metal plate 43, the first plate 30, the second plate 32, and the rod 12 has the interval between the inner metal plate 42 and the outer metal plate 43 and the mounting position. It is possible to reduce weight while maintaining accuracy. The inner metal plate 42 and the outer metal plate 43, which are rectangular metal plates, reduce the thickness of the metal plate, and the first plate 30 is a plate that maintains the mounting position accuracy of the inner metal plate 42 and the outer metal plate 43. By providing a cylindrical punching hole with a thin plate-like thickness, the second plate 32 has a thin plate-like plate thickness and a cylindrical shape while maintaining the mounting position accuracy of the first plate 30. The rod 12 is formed by providing a punching hole and by making the diameter of the rod 12 small.

  By making the diameter of the rod 12 small, the relative position in the xz-axis plane can be rotated between the first plate 30 paired in the y-axis direction or the second plate 32 paired. Twist is likely to occur. However, this positional deviation is concentrated at the center position in the y-axis direction between the first plates 30 that make a pair in the y-axis direction or between the second plates 32 that make a pair. Therefore, due to this positional deviation, the distance between the inner metal plate 42 and the outer metal plate 43 and the accuracy of the mounting position are unlikely to change, and the influence on the trajectory of the ion beam 22 that forms the figure 8 while moving in a spiral shape is central. It becomes a small thing limited to the position.

  As described above, in the present embodiment, the fan-shaped electrode portions 1 to 4 are attached and fixed so as to sandwich the thin plate-like inner metal plate 42 and outer metal plate 43. The ion optical system 8 includes a second plate 32 that forms a pair sandwiching the first plate 30 that forms a pair of fan-shaped electrode portions 1 to 4, passes through the pair of first plates 30, Since the first plate 30 is fixed to the second plate 32 by the plurality of rods 12 attached and fixed to the second plate 32, the distance between the inner metal plate 42 and the outer metal plate 43 and the sector shape It is possible to make the ion optical system 8 light in weight while maintaining the positional accuracy of the electrode portions 1 to 4 in the ion optical system 8, and thus inexpensive.

  In the present embodiment, the fan-shaped electrode part that bends the trajectory of the ion beam 22 is composed of four fan-shaped electrode parts 1 to 4. it can.

  In this embodiment, the ion beam 22 draws an 8-shaped orbit in the xz-axis plane, but this orbit can be a circular orbit.

It is a block diagram which shows the whole structure of a TOF type | mold mass spectrometer. It is the perspective view which looked at the ion optical system of an embodiment from the slanting direction. It is the perspective view which looked at the fan-shaped electrode part of embodiment from the diagonal direction. It is sectional drawing which shows CC 'cross section of a fan-shaped electrode part. It is sectional drawing which shows DD 'cross section of a fan-shaped electrode part. It is sectional drawing which shows the AA 'cross section of an ion optical system. It is sectional drawing which shows the BB 'cross section of an ion optical system.

Explanation of symbols

1-4 Fan-shaped electrode part 8 Ion optical system 9 Case 10 TOF type mass spectrometer 12 Rod 13 Rod hole 17 Detection part 20 Ion source 22 Ion beam 30 First plate 32 Second plate 34 Shunt 35 Spacer 36 Mazda plate 42 inner metal plate 43 outer metal plates 51-53, 62-64 spacers

Claims (6)

A fan-shaped electrode part that forms an electrostatic field that bends the orbit of the ion beam;
An ion optical system in which a plurality of the sector electrode portions are arranged in the middle of the orbit, and the orbit is a circular orbit;
A TOF mass spectrometer comprising:
The sector electrode part sandwiches two rectangular metal plates facing each other while curving one of two orthogonal sides from the direction of the other side of the two sides. A pair of plate-like first plates to be fixed;
In the ion optical system, the plurality of fan-shaped electrode portions are arranged in a parallel arrangement in which the arrangement direction of the first plates forming a pair is orthogonal to the orbital surface of the orbit, and the plurality of the plurality of the arranged electrode arrangements are arranged in parallel. The paired first plates are fixed to the paired second plates that pass through the paired second plates and the paired first plates disposed at positions sandwiched from the arrangement direction. Having a rod-like rod
TOF type mass spectrometer characterized by   The TOF mass spectrometer according to claim 1, wherein the ion optical system includes two rods for each of the fan-shaped electrode portions.   3. The TOF mass spectrometer according to claim 1, wherein the fan-shaped electrode unit includes an insulator between the rectangular metal plate and the first plate in the arrangement direction.   4. The TOF mass spectrometer according to claim 1, wherein the ion optical system includes a spacer between the first plate and the second plate in the arrangement direction. 5. .   5. The TOF mass spectrometer according to claim 1, wherein the ion optical system includes a plurality of the fan-shaped electrode portions having the same shape.   6. The TOF mass spectrometer according to claim 1, wherein the ion optical system includes four fan electrode portions.

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