WO2010125670A1 - Ion detection device and ion detection method - Google Patents

Abstract

Provided is an ion detection device comprising a mechanism for converting ions into electrons and amplifying the electrons obtained by the conversion, which enables a reduction in noise caused by stray light. The ion detection device is provided with an ion-electron conversion electrode which converts mass-fractionated ions into electrons, and an amplification mechanism which is configured so as to amplify the electrons, the amplification mechanism leading the electrons obtained by the conversion by the ion-electron conversion electrode thereinto by an electric field and amplifying the electrons.  The ion-electron conversion electrode has any one of a needle shape, a ribbon shape, a mesh shape, or a slit shape.

Description

Ion detector and ion detection method

The present invention relates to an ion detection device and an ion detection method for detecting ions at a very high S / N (signal / noise ratio) in a mass spectrometer.

The mass spectrometer is an analyzer that quantifies and determines each component constituting the mixed sample by the difference in mass, and is extremely characterized in that it has extremely high sensitivity (low detection limit) as compared with other analyzers. One of the elements that realizes this is a unit that detects ions separated by mass, and has a plate-shaped ion-to-electron conversion electrode, a secondary electron multiplying electrode of about 15 stages (SEM, It also has a collector, etc.).

Mass-fractionated ions vertically collide with the ion-electron conversion electrode. At this time, if -1.9 kV is applied to the ion-electron conversion electrode, the collision energy becomes approximately 1.9 keV, electrons generate from the surface of the ion-electron conversion electrode by this energy, and ion-electron conversion is performed. The yield (efficiency) is about 0.1 to 0.2 and is not largely influenced by the material or surface state of the ion electron conversion electrode, but is generally proportional to the collision energy, so the ion energy is important for ion / electron conversion. .

Electrons generated from the ion-electron conversion electrode to which a voltage of about -1.9 kV is usually applied are incident on the first stage electrode of the SEM in which a positive potential difference is applied to the ion-electron conversion electrode. A voltage is applied to each of the electrodes constituting the SEM sequentially with a potential difference of about 100 to 200 V from the first stage electrode to the last stage electrode. Each of these voltages is often supplied by dividing the applied voltage supplied to the first stage electrode by the resistance provided inside the detection unit. A voltage of about -1.5 kV is usually applied to the first stage electrode, and electrons incident on the SEM first stage electrode from the ion electron conversion electrode generate secondary electrons on the first stage electrode surface. The yield of secondary electron generation due to electron collision is very high, and with this energy, it is about 1.5 to 2.0 in an appropriate surface state. Therefore, amplification of electrons is realized. Thereafter, electron amplification is similarly performed in the second stage electrode, third stage electrode..., And amplification of 5 to 6 digits is performed in the final stage. An SEM capable of performing such extremely high amplification is essential for mass spectrometric analysis.

However, not only ions to be detected and signaled but also light that causes noise come to the ion electron conversion electrode. At the ion-to-electron conversion electrode, light is also converted into electrons as well as ions, so the electrons generated by the light are also amplified by the SEM in the same manner as the signal, and the electron amplification factor is increased by increasing the applied voltage. / N is not improved. Since mass spectrometers need to analyze mixed samples with concentration differences of 5 to 6 digits, S / N can also be 5 to 6 digits, and how to suppress noise is an important factor that determines its performance. It becomes.

In mass separation, it is first necessary to ionize neutral molecules to be measured. A typical ionization method is electron ionization, which uses thermions generated from the filament of the ion source to give energy to neutral molecules to remove shell electrons and ionize them (in addition to plasma and ionisation, There are many ways to use electric fields etc)). However, in this process, a large number of molecules which are only excited are generated without reaching ionization, and these molecules release and stabilize vacuum ultraviolet light having energy of several to several tens of eV after a while. Since this vacuum ultraviolet light has no charge, it is not separated by the mass separation function and arrives at the ion electron conversion electrode, and when it is irradiated, it emits electrons (also called photoelectrons because of light).

Furthermore, it is also known that light that causes noise may be emitted from parts of the mass spectrometer. Furthermore, in the quadrupole mass spectrometer most representative of mass spectrometers, soft x-rays having higher energy than vacuum ultraviolet light due to the collision of ions with the quadrupole electrode to which a negative high voltage is applied. Occurs.

Vacuum ultraviolet light and soft X-rays generated in this manner are called "stray light" because they cause noise for the mass spectrometer. Since the stray light greatly lowers the basic performance of the mass spectrometer by lowering the S / N of the mass spectrometer, the device described in the following document is to convert only ions to electrons as SEM and to convert stray light to electrons as much as possible. Although it is described in, it is not always sufficient.

JP-A-8-7832 JP, 2001-351565, A

In order that the ion detection unit as the ion detection device does not detect stray light as noise, the following measures are taken in Patent Document 2 and Non-Patent Document 1.
FIG. 20A is a schematic view showing the whole of a conventional mass spectrometer, FIG. 20B is an enlarged view of the vicinity of an ion detection unit of the mass spectrometer shown in FIG. 20A, and FIG. 20C is ion electrons shown in FIG. It is the detail figure which showed conversion electrode vicinity by trigonometry.

In FIG. 20A, a mass spectrometer 1 disposed in a vacuum vessel 1 a includes an ion source 2, a mass separation mechanism 3, and an ion detection unit 4.
The ion source 2 has a filament 5 and ionizes a neutral molecule containing a molecule to be measured using the thermoelectrons 6 generated by the filament, and introduces the generated ion to the mass fractionator 3.

The mass analysis mechanism 3 has a quadrupole electrode 7 consisting of four cylindrical electrodes. By electrically connecting opposing electrode sets of the quadrupole electrodes 7 and applying a DC voltage and a high frequency AC voltage to each electrode set, only ions having a mass number corresponding to each voltage, frequency, etc. Is made to pass in the long axis direction of the quadrupole electrode 7. In addition, an aperture plate 8 in which an aperture is formed as a quadrupole exit electrode in which an aperture is formed is disposed at an outlet portion of the mass analysis mechanism 3. Although the aperture plate 8 is set to a predetermined potential, it is normally at the ground potential (earth potential, 0 V).

The ion detection unit 4 has a deflection mechanism 9 for bending the trajectory of ions, a secondary electron multiplier (SEM) 11, and an ion electron conversion electrode 10. In FIG. 20A, the secondary electron multiplier 11 has a plurality of electrodes and a collector 12. A potential of -1.9 kV is applied to the ion electron conversion electrode 10. Further, a potential of -1.5 kV is applied to the first stage electrode of the secondary electron multiplier tube 11.

In such a configuration, when ions generated in the ion source 2 are incident on the mass separation mechanism 3, ions 13 having a desired mass number pass through the mass separation mechanism 3 and the ions 13 are detected by the ion detection unit 4 It is incident on The ion 13 incident on the ion detection unit 4 changes its trajectory toward the ion electron conversion electrode 10 by the action of the deflection mechanism 9. When the ions 13 are incident on the ion-to-electron conversion electrode 10, the ion-to-electron conversion electrode 10 generates electrons 15 by ion / electron conversion. When the electrons 15 are incident on the first stage electrode of the secondary electron multiplier tube 11, secondary electrons are generated at the electrode, and the secondary electrons are sequentially amplified by the subsequent stage electrode and are incident on the collector 12. The collector 12 outputs a signal 14 according to the incident secondary electrons.

In such a mass analysis, as described above, stray light 16 such as vacuum ultraviolet light may be incident on the mass separation mechanism 3 from the ion source 2 in addition to the ions.

As described above, the potential of the aperture plate 8 is usually the ground potential (earth potential: 0 V), and the ion detection unit 4 detects the ions that have passed through the aperture plate 8. Although it is efficient that the ion detection unit 4 is located on the same axis as the aperture formed in the aperture plate 8 if only ion detection is considered, then 16 stray lights will be detected as well. Therefore, by arranging only the ion detection unit 4 at a position away from the aperture and bending only the trajectory of the ions 13 by the electric field of the deflection mechanism 9 or the ion electron conversion electrode 10, the ions can be detected without much loss Thus, the stray light 16 does not directly irradiate the ion electron conversion electrode 10. This structure is widely spread as an off-axis structure.
By adopting the off-axis structure in this way, it is possible to reduce the incidence of stray light 16 on the ion-electron conversion electrode, but as shown in FIG. 20B, stray light 16 is generated by being reflected in deflection mechanism 9 or the like. Stray light (hereinafter also referred to as reflected stray light) 17 may occur.

The off-axis structure is effective for stray light 16 traveling straight, but is not valid for reflected stray light 17 due to the reflectance of 20 to 30% of vacuum ultraviolet light and soft X-rays. The reason is that since the ion electron conversion electrode 10 has a plate shape, the area receiving the reflected stray light 17 is equal to the cross-sectional area of the stray light, and all of them are detected (FIG. 20C upper right). This has become a major problem for the improvement of the S / N for the latest mass spectrometer, and there has been a demand to reduce the influence of stray light, that is, to reduce the influence of external stray light.

Although the secondary electron multiplier (SEM) shown in FIG. 20A is a front entry type in which electrons are incident from the front of the SEM assembly axis, other than this, a side entry type in which electrons are incident from the side surface of the SEM assembly axis is is there.

The present invention has been made in view of such problems, and the object of the present invention is to be attributed to stray light in an ion detector having a mechanism for converting ions into electrons and amplifying the converted electrons. An object of the present invention is to provide an ion detector capable of reducing noise.

A first aspect of the present invention is an ion detector, comprising: an ion electron conversion electrode for converting mass-separated ions into electrons; and an amplification mechanism configured to amplify electrons, the ion electrons And an amplification mechanism for drawing in and converting the electrons converted by the conversion electrode by an electric field, and the ion electron conversion electrode is any one of a needle shape, a ribbon shape, a mesh shape, and a slit shape. .

A second aspect of the present invention is an ion detection method, which comprises the steps of mass separating incident ions, and any of needle-shaped, ribbon-shaped, mesh-shaped, and slit-shaped ions subjected to mass separation. It has a step of converting into an electron by an ion-electron conversion electrode having one shape, and a step of amplifying the converted electron.

According to the present invention, in an ion detector having an ion electron conversion electrode, stray light incident on the ion conversion electrode can be reduced, and an improvement in the S / N ratio can be realized.

It is the figure which showed a part of mass spectrometer which concerns on one Embodiment of this invention by trigonometry. It is a three-dimensional perspective view of a part of ion detector concerning one embodiment of the present invention. It is the figure which showed a part of ion detector which concerns on one Embodiment of this invention by the trigonometry. It is the figure which showed a part of ion detector which concerns on one Embodiment of this invention by the trigonometry. It is the figure which showed a part of ion detector which concerns on one Embodiment of this invention by the trigonometry. It is a figure for demonstrating the electric potential switching of the ion electron conversion electrode shown to FIG. 3A. It is the figure which showed a part of ion detector which concerns on one Embodiment of this invention by the trigonometry. It is the figure which showed a part of ion detector which concerns on one Embodiment of this invention by the trigonometry. It is the figure which showed a part of ion detector which concerns on one Embodiment of this invention by the trigonometry. It is the figure which showed a part of ion detector which concerns on one Embodiment of this invention by the trigonometry. It is the figure which showed a part of mass spectrometer which concerns on one Embodiment of this invention by trigonometry. It is the figure which showed a part of mass spectrometer which concerns on one Embodiment of this invention by trigonometry. It is the figure which showed a part of ion detector which concerns on one Embodiment of this invention by the trigonometry. It is a figure for demonstrating the cleaning of the ion detector which concerns on one Embodiment of this invention. It is a figure for demonstrating cleaning of the ion detector which concerns on one Embodiment of this invention, Comprising: It is a front view of an ion detector. It is a top view of the ion detection apparatus shown to FIG. 11A. It is the figure which showed a part of ion detector which concerns on one Embodiment of this invention by the trigonometry. It is a figure for demonstrating a mode that ion injects into the ion conversion electrode shown to FIG. 12A. It is the figure which showed a part of ion detector which concerns on one Embodiment of this invention by the trigonometry. It is the figure which showed a part of ion detector which concerns on one Embodiment of this invention by the trigonometry. It is a front view showing a part of mass spectrometer concerning one embodiment of the present invention. It is a top view which shows a part of mass spectrometer shown to FIG. 15A. It is a front view of the ion detection apparatus shown to FIG. 15A. It is a front view of the ion detector concerning one embodiment of the present invention. It is a front view showing a part of mass spectrometer concerning one embodiment of the present invention. It is a front view of the ion detection apparatus shown to FIG. 17A. It is the figure which showed a part of mass spectrometer which concerns on one Embodiment of this invention by trigonometry. FIG. 5 is a type diagram of each type of secondary electron multiplier according to an embodiment of the present invention. It is a schematic diagram which shows the whole of the conventional mass spectrometer. It is an enlarged view of ion detection apparatus vicinity of the mass spectrometer shown to FIG. 20A. It is the figure which showed the ion electron conversion electrode vicinity shown to FIG. 20A by the trigonometry.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings described below, components having the same function are denoted by the same reference numerals, and the repetitive description thereof will be omitted.

(Principle of the present invention)
The present invention is based on the following principle.
Principle 1: <reduction of real area>
In the present invention, stray light (reflected stray light or stray light incident from the outside of the ion detector) is received by changing the shape of the ion electron conversion electrode from a conventional plate to a needle shape, ribbon shape, mesh shape, slit shape or the like. Reduce the area. The influence of stray light can be reduced by this area reduction.

Principle 2; <reduction of expected area>
By arranging the ion-electron conversion electrode so that the expected area (area to which stray light is irradiated) from the arrival direction of stray light is reduced, high-intensity stray light from the arrival direction of the ion-electron conversion electrode is irradiated Reduce the area. The effects of stray light can be significantly reduced.

Principle 3: <Coron force-based ion collection>
By forming an electric field that attracts ions to the ion electron conversion electrode such as needle shape, ribbon shape, mesh shape, slit shape, etc., the decrease in ion detection efficiency due to the area reduction is compensated, and the ion to the ion electron conversion electrode The attractive effect can be made equal to that of the conventional plate type.

Principle 4: <Both collection efficiency and conversion efficiency>
By installing an ion electron conversion electrode such as a needle shape, ribbon shape, mesh shape, slit shape or the like so as to extend along the incident direction of ions, the ion electron conversion efficiency can be excellent while securing good ion collection efficiency. Secure.

These will be described below.
The amount of noise based on stray light is proportional to the area of the ion-electron conversion electrode that receives stray light. On the other hand, since stray light is an electromagnetic wave such as vacuum ultraviolet light or soft x-ray and has no charge, it is not affected by an electric field and goes straight. As a result, the area in which the ion-electron conversion electrode receives stray light is equal to the cross-sectional area of the ion-electron conversion electrode (irradiation area of the stray light flux on the ion-electron conversion electrode) estimated by the irradiated stray light flux. Therefore, reducing the cross-sectional area will reduce noise.

Stray light that has not been irradiated to the ion-to-electron conversion electrode passes by and is eventually irradiated to the vacuum chamber of the ground potential, but the electrons (photoelectrons) generated there are set to the negative potential because they have the potential of the ground potential. It does not enter the electrode of the secondary electron multiplier and does not become noise. However, a part of the stray light is reflected as it is to become reflected stray light, which may be irradiated to the ion-electron conversion electrode to become noise. That is, although the stray light irradiated to the ion electron conversion electrode is high in intensity from the original arrival direction, there are other stray lights irradiated from all directions by reflection.

The principle 1 <reduction of the real area> is effective for “stray light from all directions” after reflection, and the noise amount thereof is approximately proportional to the surface area of the ion-electron conversion electrode. Next, Principle 2 <Reduction of the expected area> is effective for the “stray light from the original arrival direction before reflection” mentioned at the beginning, and the noise amount is the initial arrival at the ion electron conversion electrode Proportional to the expected area from the direction. This "stray light from the original arrival direction" is high in strength, but the effect is great if the measures are successful, and it is practical to make the prospect area significantly smaller, so this practicality is high.

It should be noted that part of the stray light is also irradiated to the other electrodes (for example, the ion suppressor electrode and the shield electrode) coexisting in the ion detection unit, and since a deep negative potential is applied to those electrodes as well. The electrons generated from H.sub.2 can enter the secondary electron multiplier and become noise. Therefore, it is effective to reduce the light receiving area of stray light by making these electrodes into needle shape, ribbon shape, mesh shape, slit shape or the like.

On the other hand, charged ions are attracted toward the high potential ion-electron conversion electrode while bending the orbit by Coulomb force (in detecting positive ions, the ion-electron conversion electrode has a negative high potential such as -2 kV). is there). For this reason, although the actual area of the ion electron conversion electrode such as needle shape, ribbon shape, mesh shape, and slit shape is small, the detection efficiency of ions is not as low as that of stray light. The attractive force is weak for ions passing away from the ion-electron conversion electrode, but the ion bundle has a negative low potential smaller in absolute value than the ion-electron conversion electrode, in other words, the extrusion potential for ions. By installing an ion suppressor electrode having (for example, -600 V), it is possible to increase the collection efficiency of ions by the pushing effect. It is also effective to dispose a plurality of ion electron conversion electrodes of needle shape, ribbon shape, mesh shape, slit shape or the like and disperse them in the whole ion flux. These effects can be obtained from principle 3 <collection of ions by Coulomb force>.

By the way, although ions in the stopped state (zero initial energy of ions) are necessarily collected on the electrode having a lower potential (100% collection efficiency), collection efficiency decreases when the initial energy in the vertical direction is obtained. This is similar to the fact that an object attracted to the earth is repelled into space without necessarily colliding with the earth. Therefore, to increase the detection efficiency of ions, it is effective to make the initial energy of ions smaller. However, the energy of ions required to cause ion-to-electron conversion is as high as several hundred eV or more.

Although these two requirements are contradictory, by installing the needle-shaped ion-electron conversion electrode in parallel with the incident direction of the ion flux, that is, by injecting ions along the extending direction of the ion-electron conversion electrode It is possible to solve.

Considering the collection of ions, the energy in the direction perpendicular to the ion flux incident direction, which reduces the collection efficiency, is small as long as it is an ion flux (it can not be an ion flux if it has one). Next, the attractive force of the ions is exactly proportional to the product of the Coulomb force and the time for which it is applied (the impulse), and the ions fly parallel to the distracting ion-electron conversion electrode, so The time for passing the vicinity of the electron conversion electrode is long, and as a result, a large impulse toward the ion conversion electrode is received. Finally, the ions are collected at the ion conversion electrode while maintaining sufficient energy in the ion incident direction. This is principle 4 <coexistence of collection efficiency and conversion efficiency>, which makes it possible to achieve the same detection efficiency as in the case of the plate shape of the prior art.

In summary, by forming the ion electron conversion electrode into a needle shape, a ribbon shape, a mesh shape, or a slit shape, the influence of stray light can be reduced (Principle 1) without sacrificing ion detection (Principle 3). Further, the ion detection electrode can be kept at the same level as the conventional plate shape by, for example, placing the extending direction of the ion-electron conversion electrode parallel to the ion incident direction and causing the ions to enter along the extending direction. (Principle 4) The influence of stray light can be significantly reduced (Principle 2).
Furthermore, in the prior art, the ions are incident on the front of the ion-electron conversion electrode, but in the present invention, the oblique incidence causes an effect of improving the ion collection efficiency.

First Embodiment
FIG. 1A is a diagram showing a part of the mass spectrometer according to the present embodiment by trigonometry, and FIG. 1B is a three-dimensional perspective view of a part of the ion detection unit according to the present embodiment. These are the figures which showed a part of ion detection unit which concerns on this embodiment by trigonometry. The stray light receiving area and stray light cross-sectional area of the ion electron conversion electrode are shown in the upper right of FIG. 1C. Further, in order to make the drawing easy to see, the top plate portion of the shield electrode is omitted in FIG. 1B.

In FIG. 1A, a deflection mechanism 114 and a structure shown in FIG. 1B are provided downstream of a mass separation mechanism 111 having a quadrupole electrode 112 and an aperture plate 113 formed with an aperture 113a as an outlet electrode of the mass separation mechanism. The ion detection unit 101 which has is provided. In such a configuration, the ion flux 107 introduced from the mass analysis mechanism 111 via the aperture 113 a changes its trajectory toward the ion electron conversion electrode 103 by the action of the deflection mechanism 114. When the ion bundle 107 is incident on the ion electron conversion electrode 103, electrons 109 are generated at the ion electron conversion electrode 103 by ion / electron conversion. The electrons 109 are incident into the secondary electron multiplier tube 101 through the electron incident port 102 formed in the secondary electron multiplier tube 101 as a secondary electron multiplier, and the secondary electron multiplier tube It is amplified by

The conventional secondary electron multiplier can detect not only ions but also electrons and (high energy) light, and the electrode at the first stage performs ion electron conversion, secondary electron generation, and photoelectron generation, respectively. Since the basic function and operation are the same, the first stage electrode and the electrodes after that have substantially the same shape and structure. However, in this embodiment, an ion-electron conversion electrode having a completely novel structure as described below has a mechanism for converting ions into electrons and amplifying the converted electrons (hereinafter referred to as “ion electron amplification mechanism”). By arranging in the first stage, it is possible to drastically improve the performance of ion electron conversion to reduce stray light noise and improve S / N. That is, in the present embodiment, the first stage electrode of the ion electron amplification mechanism is used as the ion electron conversion electrode which is characteristic of the present invention.

The “first-stage electrode of the ion electron amplification mechanism” is an electrode that generates an electron serving as a signal by the ion to be detected when the ion is incident. For example, in FIGS. 1A to 1C, the ion electron conversion electrode 103 disposed immediately in front of the electron entrance 102 of the secondary electron multiplier tube 101 becomes a signal when the ion flux 107 to be detected is incident. Since the next electron 109 is generated, it becomes the first stage electrode of the ion electron amplification mechanism.

In the present embodiment, as shown in FIG. 1B, the ion electron amplification mechanism has a secondary electron multiplier tube 101 as an amplification mechanism configured to amplify electrons, and an ion electron conversion electrode 103, An ion electron conversion electrode 103 is disposed at the first stage of the ion electron amplification mechanism.

In this embodiment, the ion electron conversion electrode 103, which is an electrode for converting ions into electrons, is formed into a needle shape, and its extension direction (here, longitudinal direction = axial direction) is parallel to the traveling direction in the stray light flux 108. And set a potential of -1.9 kV. That is, the ion electron conversion electrode 103 is disposed such that the extending direction of the ion electron conversion electrode 103 is parallel to the traveling direction of the ion flux 107. At that time, the diameter of the ion electron conversion electrode 103 is about 0.1 to 1.0 mm, for example, 0.5 mm, and the length is about 5 to 20 mm, for example 10 mm. The material is preferably a material resistant to deterioration such as stainless steel or molybdenum. Further, the shape of the ion electron conversion electrode 103 may not be a needle, but may be a shape having a slit (slit shape), a mesh shape, or the like.

As described above, in the present embodiment, since the shape of the ion electron conversion electrode 103 is a needle, even if the ion electron conversion electrode 103 is provided in the ion bundle 107 or the stray light flux 108 as shown in FIGS. The area (light receiving area) on which the stray light flux 108 is effectively incident can be reduced. That is, since the stray light flux 108 arrives with the ion flux 107 due to various factors, conventionally, a plate-like electrode (the ion-electron conversion electrode of the present invention for converting ions into electrons so as to be contained in the stray light flux). If the plate-like electrode is disposed, the amount of irradiation of stray light increases, and the S / N ratio is lowered. However, in the present embodiment, since the needle-shaped electrode is used as the ion electron conversion electrode, the stray light receiving area itself can be reduced. Therefore, even if the ion electron conversion electrode 103 is provided so as to be included in the stray light flux 108, the decrease in S / N ratio can be reduced.

Here, the stray light flux 108 is the “stray light from the original arrival direction” described above, and reducing the incidence of the stray light flux 108 to the ion-electron conversion electrode 103 is effective from the viewpoint of noise reduction. . Therefore, in the present embodiment, by causing the ion flux 107 to be incident along the extension direction of the ion electron conversion electrode 103, the amount of incident stray light flux 108 to the ion electron conversion electrode 103 can be further reduced. Therefore, even if the ion-electron conversion electrode 103 is present on the way of the stray light flux 108, as shown in FIG. 1C, ion-electron conversion of the stray light flux 108 incident from the same direction as the ion flux 107. The amount of incident light to the electrode 103 can be further reduced.

Further, as shown in FIG. 1B, a mesh-shaped ion suppressor electrode 104 is provided around the ion electron conversion electrode 103 and at a position surrounding the ion flux 107. A potential of -1.0 kV is applied to the ion suppressor electrode 104. By this potential, the incident ion flux 107 can be focused on the ion electron conversion electrode 103, and since the shape is a mesh, secondary electrons generated from the ion electron conversion electrode 103 can be passed. The optical transmittance of the ion suppressor electrode 104 is about 60 to 95%, for example 90%, and the length is a dimension surrounding the ion electron conversion electrode 103, and the material is preferably a material resistant to deterioration such as stainless steel or molybdenum. The shape may be a shape having a slit instead of a mesh, a needle shape, or the like.

Next, by applying −1.5 kV in the positive direction from the ion electron conversion electrode 103 to the first stage electrode (electron entrance 102) of the secondary electron multiplier tube 101 installed near the side surface of the ion suppressor electrode 104, the ion electron Secondary electrons generated from the conversion electrode 103 are taken, multiplied and detected.

Further, in the present embodiment, the shield electrode 105 is provided at a position surrounding the ion-electron conversion electrode 103 and the ion suppressor electrode 104. By applying a potential of -2.0 kV to the shield electrode 105, the secondary electrons generated from the ion electron conversion electrode 103 are not diffused to the wall of the vacuum vessel which is the ground potential, and the electron incidence of the secondary electron multiplier tube 101 It can be incident on the mouth 102. The shape of the shield electrode 105 may be a plate shape, a slit shape, or a mesh shape. The material of the shield electrode 105 may be an electrode material used in vacuum such as stainless steel or nickel.

Further, a focus electrode 106 having a hole in the center is provided between the opening of the shield electrode 105 and the secondary electron multiplier tube 101. By applying a potential of -1.8 kV to the focus electrode 106, it is possible to increase the efficiency with which the secondary electrons enter the secondary electron multiplier tube 101.

In summary of the main points, since the ion-electron conversion electrode 103 at the deep negative potential is surrounded by the ion suppressor electrode 104 at a shallower potential than that, as shown in FIG. Even if the ion flux 107 can be collected. Then, as shown in FIG. 1C, the secondary electrons 109 generated at the ion electron conversion electrode 103 pass through the mesh-like ion suppressor electrode 104, but there is a shield with a potential deeper than that of the ion electron conversion electrode 103. The light is transported to the electron incident port 102 of the secondary electron multiplier tube 101 at a potential shallower than the ion electron conversion electrode 103 on one side without being diffused around the ground potential by the electrode 105 and amplified. The focus electrode 106 has a potential between the ion electron conversion electrode 103 and the electron entrance 102 of the SEM, and helps the secondary electrons 109 to be transported to the electron entrance 102.

The potentials to be applied to the ion electron conversion electrode 103, the ion suppressor electrode 104, the shield electrode 105, and the focus electrode 106 can be separately supplied, or the division resistances of the respective electrodes of the secondary electron multiplier tube 101 can be used. It is also possible to use the potential applied at the same time.

Second Embodiment
FIG. 2 is a diagram showing a part of the ion detection unit according to the present embodiment by trigonometry. In the present embodiment, the entire configuration is the same as that of the first embodiment, but the installation place of the ion electron conversion electrode is outside the stray light flux so that the shape is a ribbon (thin plate) shape.

In FIG. 2, reference numeral 201 denotes a ribbon-shaped ion electron conversion electrode. The ion electron conversion electrode 201 is arranged outside the stray light flux 108, and a potential of -1.9 kV is applied. In addition, the ion electron conversion electrode 201 is disposed so that the ion flux 107 is incident along the extension direction (long axis direction in FIG. 2).

Thus, by causing the ion flux 107 to be incident along the extension direction of the ion electron conversion electrode 201, as shown in FIG. 2, the ion electrons of the stray light flux 108 incident from the same direction as the ion flux 107. The amount of light incident on the conversion electrode 103 can be reduced.

In this embodiment, by setting the installation place of the ion electron conversion electrode 201 outside the stray light flux 108, generation of noise based on stray light can be further reduced, but the installation place is inside the ion suppressor electrode 104. It is still in the shape of a ribbon. Therefore, since the electrode surface area is increased and the ion collection efficiency is increased as compared with the needle-shaped ion-electron conversion electrode described in the first embodiment, the ion collection efficiency does not decrease much. Although in FIG. 2 the ion electron conversion electrode 201 is placed apart from the secondary electron multiplier tube 101, it may be placed close to it.
Further, in the present embodiment, the shape of the ion electron conversion electrode 201 is not limited to the ribbon shape, and may be a mesh shape.
Furthermore, in the present embodiment, the outer shape of the ion-electron conversion electrode 201 is not limited to the rectangular shape, and the outer shape may be any shape such as a circle, an ellipse, or a star.

Third Embodiment
FIG. 3A is a diagram showing a part of the ion detection unit according to the present embodiment by trigonometry. In this embodiment, the use of a needle-shaped ion-electron conversion electrode is the same as that of the first embodiment, but as shown in FIG. 3, a plurality of needle-shaped ion electron exchange electrodes 103 are used. This can increase the collection efficiency of ions.

Then, not all of them are used as the ion electron conversion electrode, but some of them are used with the same potential as the ion suppressor electrode, and if the ion electron conversion electrode in use is deteriorated, the same potential as the ion suppressor electrode is used. The life can be extended by replacing it with the setting.

This potential switching will be described using FIG. 3B.
In FIG. 3B, for example, a potential of -1.9 kV is applied as the ion electron conversion potential to the ion electron conversion electrodes 103a, 103b and 103d, and -1.0 kv as the ion suppressor potential is applied to the ion electron conversion electrode 103c. Apply a potential. Then, at a predetermined timing, the applied potential to any one of the ion- electron conversion electrodes 103a, 103b, and 103d is changed to the ion suppressor potential, and the applied potential to the ion-electron conversion electrode 103c is changed to the ion-electron conversion potential . The potential switching may be performed in this manner.

Fourth Embodiment
FIG. 4 is a diagram showing a part of the ion detection unit according to the present embodiment by trigonometry. In the present embodiment, the use of the ion suppressor electrode is the same as that of the first embodiment, but the shape is used as a needle and arranged in parallel with the ion incident direction. The number of needles as ion suppressor electrodes can be about 6 to 10, for example, eight. Further, the diameter of the needle may be about 0.05 to 1.0 mm, for example, 0.1 mm, and the length may be a dimension that surrounds the ion electron conversion electrode. Furthermore, the material of the needle is preferably a material resistant to deterioration such as stainless steel or molybdenum.

In FIG. 4, eight needle-shaped ion suppressor electrodes 401 a to 401 h are disposed so as to surround the ion electron conversion electrode 103. The ion suppressor electrodes 401a to 401h are arranged such that the ion flux 107 is incident along the extending direction. A potential of -1.0 kV is applied to each of the eight ion suppressor electrodes 401a to 401h.

As described above, in the present embodiment, since the ion suppressor electrode is constituted by a plurality of needles, the area is reduced as compared with the mesh-shaped ion suppressor electrode (the first embodiment). Therefore, the probability that the secondary electrons 109 generated from the ion electron conversion electrode 103 are absorbed by the ion suppressor electrode decreases with the reduction of the area, so the secondary electron multiplier tube 101 of the secondary electrons 109 The incident efficiency can be increased.

Fifth Embodiment
FIG. 5 is a diagram showing a part of the ion detection unit according to the present embodiment by trigonometry. The use of a needle-shaped ion suppressor electrode is the same as in the fourth embodiment, but in this embodiment, the voltage applied to the ion suppressor electrodes 401 e to 401 h closer to the secondary electron multiplier tube 101 is far The depth is set to be approximately 100 V shallow (in the positive direction) with respect to the ion suppressor electrodes 401a to 401d on the side. That is, a potential of -1.0 kV is applied to each of the ion suppressor electrodes 401a to 401d, and a potential of -0.9 kV is applied to each of the ion suppressor electrodes 401e to 401h.

In the fourth embodiment (FIG. 4), the applied potentials to the ion suppressor electrodes 401a to 401h are all the same potential (-1.0 kV), so the force for transporting the secondary electrons 109 to the secondary electron multiplier tube 101 ( The electric potential) is generated only at the electric potential at the inlet of the secondary electron multiplier tube 101. On the other hand, in the present embodiment, among the plurality of needle-shaped ion suppressor electrodes, the potential applied to the ion suppressor electrode disposed on the secondary electron multiplier tube 101 side is opposite to that of the secondary electron multiplier tube 101 It is smaller than the applied potential to the ion suppressor electrode arranged on the side. Thus, since the applied potential is set and a potential difference is made to direct the ion suppressor electrode itself toward the secondary electron multiplier tube 101 side, the secondary electrons 109 generated from the ion electron conversion electrode 103 become the secondary electron multiplier tube. The efficiency of incidence to 101 can be increased.

Sixth Embodiment
FIG. 6 is a diagram showing a part of the ion detection unit according to the present embodiment by trigonometry. In the present embodiment, in the first embodiment, the portion closest to the secondary electron multiplier tube 101 in the ion suppressor electrode 104 is deleted. As a result, even if the ion suppressor electrode has a mesh shape, the efficiency with which the secondary electrons 109 generated from the ion electron conversion electrode 103 enter the secondary electron multiplier tube 101 can be increased.

In FIG. 6, reference numeral 601 is an ion suppressor electrode. In the ion suppressor electrode 601, the cylindrical shape in the ion suppressor electrode 104 of the first embodiment is changed to a rectangular shape in order to facilitate manufacture. And in order to improve the incident efficiency of the secondary electron 109 to the secondary electron multiplier tube 101, it has a notch structure in which the surface closest to the rectangular parallelepiped secondary electron multiplier tube 101 is deleted. Note that a potential of -1.0 kV is applied to the ion suppressor electrode 601 having a notch.

Seventh Embodiment
FIG. 7 is a diagram showing a part of the ion detection unit according to the present embodiment by trigonometry. In the present embodiment, in the fifth embodiment, the ion suppressor electrodes 4401f and 401g closest to the secondary electron multiplier tube 101 among the plurality of needle-shaped ion suppressor electrodes 401a to 401h are deleted. As a result, the efficiency with which the secondary electrons 109 generated from the ion electron conversion electrode 103 enter the secondary electron multiplier tube 101 can be increased.

Eighth Embodiment
FIG. 8 is a diagram showing a part of the mass spectrometer according to the present embodiment by trigonometry. In this embodiment, the ion electron conversion electrode 103 of the first embodiment shown in FIG. 1 is coaxially adjacent to the aperture 113 a formed in the aperture plate 113 which is the exit electrode of the mass sorting mechanism 111. However, since the ion electron conversion electrode 103 is less susceptible to the influence of the stray light flux 108, the noise does not become serious, while the S / N can be improved by further increasing the collection efficiency of the ion flux 107. . At this time, the apparatus can be miniaturized by using a secondary electron multiplier as a side entry type secondary electron multiplier 801 provided with an electron incident surface 802 on the side as shown in FIG. it can.

Ninth Embodiment
FIG. 9A is a diagram showing a part of the mass spectrometer according to the present embodiment by trigonometry. FIG. 9B is a diagram showing a part of the ion detection device shown in FIG. 9A by trigonometry.

In this embodiment, as shown in FIGS. 9A and 9B, the side entry type secondary electron multiplier tube 801 is used, and the electron incident surface 802 is positioned at a position not directly visible from the ion electron conversion electrode 103. Next electron multiplier tube 801 is arranged. In this embodiment, when it is necessary to further reduce the influence of stray light from the first embodiment shown in FIGS. 1A to 1C, the electron incident port 802 of the secondary electron multiplier tube 801 is the ion electron conversion electrode 103. Arrange so as not to overlook. Therefore, the amount of incident stray light on the secondary electron multiplier tube 801 can be further reduced, and noise can be further reduced. On the other hand, the secondary electrons 109 generated from the ion electron conversion electrode 103 can be transported to the electron incident port 802 of the secondary electron multiplier tube 801 by controlling with the electric field, and the signal amount can be maintained.

Tenth Embodiment
In the first embodiment, the surface of the ion-electron conversion electrode 103 can be cleaned by heating by energizing the ion-electron conversion electrode 103. Since ions of the molecule to be measured collide with the ion-to-electron conversion electrode 103, a part thereof may become molecules and may be fixed. Therefore, the surface state different from the original state is obtained, and the ion electron conversion efficiency changes. However, for example, when the ion electron conversion electrode 103 is heated to 1500 ° C. or more, most of the fixed molecules can be evaporated and returned to the same surface state as the initial state.

Therefore, in the present embodiment, as shown in FIG. 10, for example, when the ion electron conversion electrode 103 is made of a high melting point material such as molybdenum, the conduction current 1001 of order A is supplied to the ion electron conversion electrode 103. The ion electron conversion electrode 103 can be heated in the range of 500 ° C. to 2000 ° C. Therefore, when the cleaning is necessary, the surface of the ion-electron conversion electrode 103 can be cleaned by heating the ion-electron conversion electrode 103 to a predetermined temperature by supplying the current 1001 in the order of A or the like.

Eleventh Embodiment
In the first embodiment, a thermal filament is provided outside the ion suppressor electrode 104, and at least one of the ion suppressor electrode 104 and the ion electron conversion electrode 103 is heated by electron impact or radiant heat by energizing the thermal filament. , Can clean the surface.

FIGS. 11A and 11B are diagrams for explaining the manner of heating and cleaning at least one of the ion-electron conversion electrode and the ion suppressor electrode according to the present embodiment.
In FIGS. 11A and 11B, a thermal filament 1101 is provided outside the ion suppressor electrode 104. During ion measurement, this filament 1101 is extinguished. At the time of actual cleaning, the applied potential to the shield electrode 105 is 0 V, the applied potential to the ion electron conversion electrode 103 is +500 V, and the applied potential to the ion suppressor electrode 104 is +100 V. Further, by setting the potential applied to the thermal filament 1101 to 0 V, electrons 1102 are generated from the thermal filament 1101. The electron 1102 is on the order of mA, the electron 1102 directed to the ion electron conversion electrode 103 has an energy of 500 eV, and the electron 1102 directed to the ion suppressor electrode 104 has an energy of 100 eV. When the electron 1102 having such energy enters the ion electron conversion electrode 103, the ion electron conversion electrode 103 can be heated in the range of 500 ° C. to 2000 ° C. to clean the ion electron conversion electrode 103. Further, when the electrons 1102 are incident on the ion suppressor electrode 104, the ion suppressor electrode 104 can be heated in the range of 200 ° C. to 1000 ° C. to clean the ion suppressor electrode 104.

Twelfth Embodiment
FIG. 12A is a diagram showing a part of the ion detection device according to the present embodiment by trigonometry. Moreover, FIG. 12B is a figure for demonstrating a mode that ion injects into the ion conversion electrode shown to FIG. 12A.

As shown in FIG. 12A, in the present embodiment, the ion electron conversion electrode 1201 is configured by spacing a plurality of needle-shaped needle electrodes apart, and the axial direction of the needle electrode constituting the ion electron conversion electrode 1201 The ion-to-electron conversion electrode 1201 is disposed so as to be oblique to the traveling direction of the ion flux 107. That is, the ion electron conversion electrode 1201 composed of a plurality of needle electrodes is installed so as to diagonally cross the ion bundle 107, and a voltage of -1.9 kV is applied to each needle electrode. Further, the voltage applied to the shield electrode 105 is set to the same −1.9 V as that of the ion electron conversion electrode 103. Further, a potential of −1.5 kV is applied to the electron entrance surface 102 of the secondary electron multiplier tube 101.

As a result, as shown in FIG. 12B, the ion flux 107 that has passed through the region (opening portion) between the needle electrodes constituting the ion electron exchange electrode 1201 and has exited to the secondary electron multiplier tube 101 is electron incident The trajectory is bent by the electric field resulting from the -1.5 kVV applied to the port 102. The ions whose orbits are bent can collide with the ion electron exchange electrode 103 to generate secondary electrons 109. In the present embodiment, the ion suppressor electrode is not necessary because the trajectory change of the ions is locally performed.

On the other hand, most of the stray light flux 108 passes through the opening portion formed between the needle electrodes constituting the ion electron exchange electrode 103, so that noise due to the stray light flux 108 can be reduced.

Thirteenth Embodiment
FIG. 13 is a diagram showing a part of the ion detector according to the present embodiment by trigonometry.
In FIG. 13, the ion electron conversion electrode 1301 is configured by spacing and arranging a plurality of needle-shaped needle electrodes. Specifically, each needle electrode is installed so that the axial direction of the needle electrode constituting the ion electron conversion electrode 1301 is perpendicular to the traveling direction of the ion bundle 107, and the plurality of needle electrodes are arranged in the ion bundle The ion bundle 107 is installed so as to cross the ion bundle 107 at an angle with respect to the traveling direction of the electron beam 107. Further, a potential of -1.9 kV is applied to each of the plurality of needle electrodes constituting the ion electron conversion electrode 1301. Further, a potential of -2.0 kV is applied to the shield electrode 105, and a potential of -1.5 kV is applied to the electron entrance surface of the secondary electron multiplier tube 101. The trajectory change and collection efficiency of ions are almost the same as in the twelfth embodiment.

As described above, since the ion electron conversion electrode 1301 has the plurality of needle electrodes spaced apart, an opening is formed in the ion electron conversion electrode 1301. Therefore, most of the stray light flux 108 passes through the opening formed between the needle electrodes, so that noise due to the stray light flux 108 can be reduced.

Fourteenth Embodiment
FIG. 14 is a diagram showing a part of the ion detector according to the present embodiment by trigonometry.
In the present embodiment, as shown in FIG. 14, the ion electron conversion electrode 1401 is changed to a plurality of needle electrodes of the ion electron conversion electrode 1301 of FIG. 13 into ribbons or meshes, and The area portion is positioned so as to be parallel to the traveling direction of the stray light flux 108. By arranging in this manner, in the present embodiment, the collection efficiency of ions is improved compared to the thirteenth embodiment.

(Fifteenth Embodiment)
In the above-described embodiment, as the amplification mechanism configured to amplify electrons, the embodiment using the secondary electron multiplier tube configured by arranging the electrodes in multiple stages has been described. In this embodiment, a multichannel plate type photomultiplier tube is used as an amplification mechanism configured to amplify electrons.

FIG. 15 is a front view showing a part of the mass spectrometer according to the present embodiment. FIG. 15B is a top view showing a part of the mass spectrometer shown in FIG. 15A. Furthermore, FIG. 15C is a front view of the ion detector shown in FIG. 15A.

The microchannel plate is a type of secondary electron multiplier tube having an electron incident surface on one side of a disk shape by arranging ultra-small continuous type SEMs horizontally. In this embodiment, a microchannel plate type having ion passage openings (openings) is used as a secondary electron multiplier, and the electron incident surface is set to face in the same direction as the traveling direction of stray light. Thus, stray light can be prevented from entering the electron incident surface.

In this embodiment, as shown in FIGS. 15A to 15C, the ion electron amplification mechanism has a microchannel plate (MCP) 1501 as an amplification mechanism configured to amplify electrons, and an ion electron conversion electrode 103. doing. The MCP 1501 has a donut shape as shown in FIG. 15B, and an opening 1502 as an ion passage port is formed. The ion bundle 107 and the stray light beam 108 pass through the opening 1502. Further, the electron incident port 1503 of the MCP 1501 is positioned on the side of the ion flux 107 and the stray light flux 108 facing the incident side of the MCP 1501.

A potential of -1.9 kV is applied to the ion electron conversion electrode 103 disposed downstream of the traveling direction of the ion flux 107 of the MCP 1501, and a potential of -1.8 kV is applied to the ion suppressor electrode 104, A potential of −2.0 kV is applied to the shield electrode 105. Further, a potential of -1.6 kV is applied to the electron incident surface 1503 of the MCP 1501. With such a configuration, the ion flux 107 is drawn to the ion electron conversion electrode 103, and the ion flux 107 generates secondary electrons 109 in the ion electron conversion electrode 103. The generated secondary electrons 109 are incident on the electron incident surface 1503 by the potential formed by the potential applied to the ion suppressor electrode 104 and the electron incident surface 1503, and the incident electrons are amplified in the SEM constituting the MCP 1501. Be done.

In the present embodiment, the surface of the MCP 1501 facing the incident surface of the ions 108 is the electron incident surface 1503. Therefore, as shown in FIG. 15C, since the stray light flux 108 which has passed through the opening 1502 goes straight as it is, it does not enter the electron incident surface 1503 of the MP 1501. On the other hand, secondary electrons 109 generated at the ion electron conversion electrode 103 can be favorably incident on the electron incident surface 1503 by the above-described action.

In this embodiment, in the ion-electron conversion mechanism, the MCP 1501 is disposed at the front stage of the traveling direction of the ion flux 107 and the ion-electron conversion electrode 103 is disposed at the rear stage. Then, it passes through the MCP 1501 and enters the ion electron conversion electrode 103. In the present embodiment, since the ion-electron conversion electrode 103 generates the secondary electrons 109 serving as a signal when the ion bundle 107 to be detected is incident, the ion-electron conversion electrode 103 is also an ion electron in this embodiment. It is the first stage electrode of the amplification mechanism.

Sixteenth Embodiment
FIG. 16 is a front view of the ion detector according to the present embodiment.
In the present embodiment, in the fifteenth embodiment, the ion suppressor electrode is installed in such a manner that the diameter of the arrangement portion increases (the shape of a wrapper) as it goes to the tip. That is, in the present embodiment, using the trumpet-like ion suppressor electrode 1601 whose width gradually widens in the predetermined direction, the predetermined direction is made to coincide with the traveling direction of the ion bundle 107 and the wide part is the ion The ion suppressor electrode 1601 is disposed so as to be positioned downstream of the traveling direction of the bundle 107. A potential of -1.8 kV is applied to the ion suppressor electrode 1601.

Now, even if stray light is irradiated to the ion suppressor electrode to which a deep negative potential as in the ion electron conversion electrode 103 is applied, it causes noise, while the stray luminous flux 108 is a parallel bundle (cylindrical shape due to irregular reflection etc. It is not a bundle but a bunch (wrapper type) with a spread. Therefore, in the present embodiment, the ion suppressor electrode is shaped like a trumpet like the spread of the stray light flux 108, and its width is spread along the traveling direction of the ion flux 107, that is, the traveling direction of the stray light flux 108. Therefore, the stray light flux 108 can be prevented from being received by the trumpet shaped ion suppressor electrode 1601. Therefore, noise can be reduced.

(Seventeenth embodiment)
FIG. 17A is a front view showing a part of the mass spectrometer according to the present embodiment. FIG. 17B is a top view showing a part of the mass spectrometer shown in FIG. 17A. In this embodiment, the ion electron conversion electrode 103 and the MCP 1501 according to the fifteenth embodiment shown in FIGS. 15A to 15C are coaxially arranged adjacent to each other on an aperture 113a formed in the aperture plate 113. However, in the present embodiment, since the influence of the stray light flux 108 is less likely to occur, the noise does not become serious. On the other hand, the collection efficiency of the ion flux 107 can be further improved, and the S / N can be further improved.

Eighteenth Embodiment
FIG. 18 is a diagram showing a part of the mass spectrometer according to the present embodiment by trigonometry. In the present embodiment, in addition to the first embodiment, the light shielding case 1801 is installed around the ion electron conversion mechanism having the ion electron conversion electrode 103 and the secondary electron multiplier tube 101. This can prevent stray light 108 from entering each electrode of the secondary electron multiplier tube 101.

The respective embodiments have been described above, but the embodiments of the present invention are not limited to these, and it is natural that the respective elements of the respective embodiments can be combined and replaced.
Moreover, the voltage applied to each electrode is not limited to the said embodiment, According to a dimension, a shape, the objective, etc., it can select arbitrarily.

Furthermore, in each of the above-described embodiments, as the secondary electron multiplier, in the first to fourteenth and eighteenth embodiments, a multistage secondary electron multiplier tube (such as reference numerals 1901 and 1902 in FIG. 19) is used. In the fifteenth to seventeenth embodiments, a microchannel plate type photomultiplier is used. However, the secondary electron multiplier is not limited to these, and may be a continuous type or scintillator / photomultiplier. That is, in the embodiment of the present invention, any configuration may be used as long as the incident electrons are amplified and output.

FIG. 19 shows an example of a secondary electron multiplier according to an embodiment of the present invention.
In FIG. 19, reference numeral 1901a denotes a side entry type secondary electron multiplier having a plurality of electrodes, and reference numeral 1901b denotes a front entry type secondary electron multiplier having a plurality of electrodes. Further, reference numeral 1901c denotes a side entry type continuous photomultiplier tube, and reference numeral 1901d denotes a front entry type continuous photomultiplier tube. Reference numeral 1902 denotes an electron incident surface, reference numeral 1903 denotes an electron, and reference 1904 denotes a collector.

For example, the secondary electron multipliers 1901a and 1901b have 16 electrodes, and the electrode D1 is disposed in the first stage of each of the secondary electron multipliers 1901a and 1901b. Then, secondary electrons generated at the electrode D1 are incident on the electrode D2, and secondary electrons generated at the electrode D2 are incident on the electrode D3. Each electrode is arranged to be incident on the In each electrode, an applied potential to each electrode is set so as to be amplified when secondary electrons are incident from the front stage and to emit secondary electrons to the rear stage.

On the other hand, the continuous photomultiplier tubes 1901c and 1901d respectively have continuous channel structures 1905 and 1906 made of, for example, lead glass, and when the electron 1903 is incident from the electron incident surface 1902, the channel structures It is configured to amplify electrons in 1905 and 1906.

Furthermore, although the ions to be measured in the above-described embodiments are positive ions, it is possible to apply not only positive ions but also negative ions by inverting the positive and negative of the set potential.
The voltage applied to the shield electrode may be the same potential as the voltage applied to the ion electron changing electrode.

The ion detection device according to one embodiment of the present invention is an ion detection unit capable of obtaining high S / N in a mass spectrometer, and is suitable for various mass spectrometers for a wide range of applications.

Now, in the present invention, in the ion detection device, the first electrode of the ion electron amplification mechanism configured to convert ions into electrons and amplify the converted electrons is a needle-shaped electrode, It is characterized in that it has a ribbon shape or a mesh shape. That is, the ion electron conversion electrode having a needle shape, ribbon shape or mesh shape is used as the first stage electrode of the ion electron amplification mechanism, and an amplification mechanism configured to amplify electrons is provided downstream of the ion electron conversion electrode. It is important to form the above ion electron amplification mechanism. By thus forming the first stage electrode of the ion electron amplification mechanism as a needle-shaped, ribbon-shaped or mesh-shaped ion-electron converting electrode, it is possible to obtain the effects according to the principles 1 to 4 described above.

Therefore, the amplification mechanism may be, for example, the secondary electron multipliers 1901a and 1901b shown in FIG. 19 themselves, or the second and subsequent stages of the secondary electron multipliers 1901a and 1901b (electrodes D2 to D16). ) May be.

For example, by using the packaged secondary electron multipliers 1901a and 1901b, the ion electron amplification mechanism of the present invention can be easily formed, so that the ion detector can be easily manufactured. In the case of using a packaged secondary electron multiplier, the ion electron conversion electrode may be provided at a stage prior to the packaged secondary electron multipliers 1901 a and 1901 b (corresponding to the former). In this case, the ion electron amplification mechanism includes packaged secondary electron multipliers 1901 a and 1901 b and an ion electron conversion electrode provided in the front stage thereof. This design concept is used in the above embodiments.

In addition, the electrode D1 positioned at the first stage of the packaged secondary electron multipliers 1901a and 1901b may be changed to the above-described ion electron conversion electrode characteristic of the present invention (corresponding to the above-mentioned latter). In this case, the packaged secondary electron multipliers 1901a and 1901b themselves constitute an ion electron amplification mechanism, and the electrodes D2 to 16 constitute an amplification mechanism configured to amplify electrons.

As described above, in the present invention, in the mechanism of the ion detection device, the ion to be detected is converted into electrons, and the converted electrons are amplified and output, the ion to be detected is first incident and signaled. It is essential to apply the structure of the ion-electron conversion electrode described in each of the above embodiments to the electrode that emits electrons.

Claims (20)

1. An ion-electron conversion electrode that converts mass-fractionated ions into electrons;
   An amplification mechanism configured to amplify electrons, the amplification mechanism configured to draw in and amplify an electron converted by the ion-electron conversion electrode by an electric field;
   The ion detector according to claim 1, wherein the ion electron conversion electrode is any one of a needle shape, a ribbon shape, a mesh shape, and a slit shape.
2. The ion suppressor electrode is further provided at a position surrounding the ion electron conversion electrode and surrounding the ion bundle, in which the secondary electron generated at the ion electron conversion electrode can pass therethrough.
   2. The ion detector according to claim 1, wherein a potential is applied to the ion suppressor electrode to focus the incident ions on the ion electron conversion electrode.
3. The ion detection unit according to claim 2, wherein the ion suppressor electrode is any one of a mesh shape, a slit shape, and a needle shape.
4. The ion suppressor electrode is formed of a plurality of needle-shaped electrodes,
   3. The ion detector according to claim 2, wherein the voltage applied to the plurality of needle-shaped electrodes has a potential difference which leads secondary electrons generated at the ion electron conversion electrode to the amplification mechanism. .
5. 3. The ion detector according to claim 2, wherein a notch for passing electrons is formed in a part of the ion suppressor electrode.
6. A plurality of the ion electron conversion electrodes are arranged,
   3. The ion detector according to claim 2, wherein an arbitrarily selected part of the plurality of ion electron conversion electrodes is set to the same potential as the ion suppressor electrode.
7. The ion detection device according to claim 2, further comprising a thermal filament that heats at least one of the ion electron conversion electrode and the ion suppressor electrode by electron impact or radiant heat.
8. And a shield electrode disposed at a position surrounding the ion electron conversion electrode and the ion suppressor electrode.
   3. The ion detection device according to claim 2, wherein a potential that is incident on the amplification mechanism is applied to the shield electrode without the secondary electrons emitted from the ion electron conversion electrode being diffused.
9. The ion detector according to claim 1, wherein a plurality of the ion electron conversion electrodes are arranged.
10. 2. The ion detection device according to claim 1, wherein the ion electron conversion electrode is disposed such that the extending direction of the ion electron conversion electrode is parallel to the ion flux traveling direction.
11. The ion-to-electron conversion electrode is disposed such that the extending direction of the ion-to-electron conversion electrode is oblique to the traveling direction of the ion flux to cross the ion flux. The ion detector according to 1.
12. In the plurality of ion electron conversion electrodes, the extending direction of the ion electron conversion electrode is disposed perpendicular to the traveling direction of the ion bundle, and the plurality of ion electron conversion electrodes are arranged in the traveling direction of the ion bundle 10. The ion detector according to claim 9, wherein the ion detector is arranged obliquely across the ion flux.
13. The ion detection device according to claim 1, wherein the ion electron conversion electrode is disposed outside the stray light flux.
14. The ion detection device according to claim 1, wherein the ion electron conversion electrode can be heated by energization.
15. The ion detection device according to claim 1, further comprising a thermal filament that heats the ion-electron conversion electrode by electron impact or radiant heat.
16. A focus electrode disposed between the ion electron exchange electrode and the electron incident surface of the amplification mechanism, for focusing secondary electrons generated by the ion electron exchange electrode onto the electron incident surface The ion detection device according to claim 1, further comprising:
17. The ion detector according to claim 1, further comprising a light shielding case installed around the amplification mechanism.
18. The ion detection device according to claim 1, wherein the electron incident surface of the amplification mechanism is disposed at a position not directly visible from the ion-electron conversion electrode.
19. The ion detection device according to claim 1, wherein the amplification mechanism is a microchannel plate having an ion passage and having an electron incident surface oriented in the same direction as a traveling direction of the ion bundle.
20. Mass fractionating the incident ions;
    Converting the mass-fractionated ions into electrons by means of an ion to electron conversion electrode having any one of a needle shape, a ribbon shape, a mesh shape, and a slit shape;
    And D. amplifying the converted electrons.

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