JPH10260079A - Electron impact emission spectrodetector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve detecting sensitivity for gas molecules or atoms by forming an anode electrode into a coil shape or a mesh shape, so that electrons can reciprocatingly run at the anode electrode. SOLUTION: When electrons are released from a thermoelectron releasing electrode 5 in the vacuum atmosphere, the electrons go to an anode electrode 19. Because the cylindrical anode electrode 19 is formed into a construction of coil shape or mesh shape spatially having gaps, the major part of the electrons are passed through the anode electrode 19. The passing electrons are returned in the direction of the anode electrode 19 of higher potential than a nipple 2 or a flange of ground potential. The electrons repeat such motion and reciprocatingly run, and the whole electrons are finally caught with the anode electrode 19. By lengthening the running distance of the electrons in this way, probability causing collision of the electrons with gas molecules 10 or the like is heightened, rate of the electrons colliding with the gas molecules or the like is increased, and hence partial pressure measuring sensitivity is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron impact emission spectrometer and, more particularly, to a method for measuring a partial pressure of a gas molecule or an atom in a vacuum.
The present invention relates to an electron-impact emission spectrometer with improved sensitivity for measuring the partial pressure of gas molecules or atoms slightly existing in a vacuum.

[0002]

2. Description of the Related Art An example of a conventional electron impact emission spectrometer will be described with reference to FIG. The port portion of the vacuum vessel 1 has a hole substantially at the center thereof, and a flange 3 covered with a quartz window 4 is hermetically attached via a nipple 2 to surround the hole. The inner area communicates with the vacuum chamber.

[0003] A thermoelectron emission electrode 5 is provided on the flange 3 at a position outside the quartz window mounting portion in an insulating and airtight manner through the wall surface. The thermoelectron emission electrode 5 is provided inside the nipple 2. It is protruding. The anode electrode 8 is connected to the flange 3
The hole is fixed to the flange 3 at a position substantially symmetrical with respect to the thermionic emission electrode 5 about the center axis of the hole. The mesh electrode 7 is fixed to the flange 3 at a position between the anode electrode 8 and the thermoelectron emission electrode 5 near the thermoelectron emission electrode.

The thermoelectron emission electrodes 5 having such a positional relationship are kept at a potential lower than the ground potential. Further, the electron repulsion electrode 6 provided outside and close to the thermoelectron emission electrode 5 is electrically connected to the thermoelectron emission electrode 5,
It has the same potential. The mesh electrode 7, the anode electrode 8, the flange 3, the case 9, and the nipple 2 are electrically connected to each other, and are at the ground potential via the vacuum vessel 1 and the case 9.

In the above configuration, electrons emitted from the thermionic emission electrode 5 are extracted in the direction of the mesh electrode 7 by an electric field formed between the thermionic emission electrode 5 and the mesh electrode 7 having a ground potential. It is. Since the mesh electrode 7 has a mesh shape with many gaps, most of the extracted electrons travel through the gaps of the mesh electrode 7 as indicated by arrows 18. Since the anode electrode 8 in the electron traveling direction has the same ground potential as the mesh electrode 7, the electrons travel while maintaining the speed, and are finally captured by the anode electrode 8.

When electrons travel toward the anode electrode 8, if gas molecules or atomic atoms 1
If a zero is present, the traveling electron will strike the gas molecule or atom with a certain probability. The probability of collision is proportional to the spatial density of each of these gas molecules or atoms 10, ie, the partial pressure.

[0007] When an electron collision occurs, each gas molecule or atom 10 is first excited at a specific rate, and then lowers its energy level. At that time, each gas molecule or atom 10 emits light 11 of a unique wavelength. The intensity of the light 11 of this specific wavelength is proportional to the spatial density of each gas molecule or atom 10, that is, the partial pressure.

The emitted light 11 passes through the quartz window 4 and comes out to the atmosphere. The light 11 emitted to the atmosphere side is the optical filter 1
2 is transmitted. The optical filter 12 is a filter that transmits only light of a narrow band wavelength centering on a specific wavelength.
Light 11 from gas molecules or atoms 10 having a specific wavelength corresponding to the wavelength that can be transmitted can be transmitted, and light of other wavelengths cannot be transmitted. That is, the intensity of the light 11 transmitted through the optical filter 12 is
Is proportional to the partial pressure of a particular gas molecule or atom 10 that emits light of a wavelength corresponding to the transmission wavelength of

The light that has passed through the optical filter 12 enters the photocathode 14 of the photomultiplier tube 13 and is converted into a current multiplied by the photomultiplier tube 13.

The current is subjected to current-voltage conversion and amplification by the preamplifier 15, and is transmitted as a voltage signal to a signal processing system. Since this voltage signal is proportional to the partial pressure of the specific gas molecule or atom 10, the partial pressure of the specific gas molecule or atom 10 can be measured.

The slit 16 together with the hole of the flange 3 serves to limit the field of view from the photocathode 14 of the photomultiplier 13 to a region between the electrodes not including the mesh electrode 7 and the anode electrode 8. Since the electrode portion is not included in the field of view from the photocathode 14, the heat radiation light and light emission from the electrode portion on the vacuum side do not reach the photocathode 14 and therefore do not cause measurement noise.

The heat shield 17 provided in the vicinity of the inner wall surface of the nipple serves to prevent radiation heat from the electrode portion from directly radiating to the nipple 2 and being heated to a high temperature.

[0013]

However, in the above-mentioned conventional electron impact emission spectrometer, the electron traveling indicated by the arrow 18 is only a short distance between the thermionic emission electrode 5 and the anode electrode 8. However, there is a disadvantage that the ratio of electrons that collide with gas molecules or atoms 10 is small, and thus the sensitivity of partial pressure measurement as a detector is low.

An object of the present invention is to solve this problem, and an object of the present invention is to provide an electron impact emission spectroscopic detector having improved sensitivity of partial pressure measurement as a detector.

[0015]

In order to achieve the above object, an electron impact emission spectrometer according to the present invention is configured as follows.

According to a first aspect of the present invention (corresponding to claim 1), an electron impact emission spectrometer detects an electron emitted from an electron emission electrode in a vacuum atmosphere and enters a vacuum atmosphere in a process of jumping into an anode electrode. Light of a specific wavelength emitted when the gas molecules or atoms excited by the electron impact collides with gas molecules or atoms existing in the region and lowers the energy level is received by the photoelectric conversion element through the spectral unit And, in the electron impact emission spectroscopy detector that measures the partial pressure of the gas molecules or atoms with the converted voltage value, the anode electrode,
It is made of a member through which the electrons can pass, and the detection area is provided in an inner space thereof, so that the electrons can reciprocate in the detection area of the anode electrode, between the anode electrode and its peripheral portion. This is an electron impact emission spectroscopic detector characterized by providing a potential difference.

In the first aspect of the invention, the electrons emitted from the electron source are captured by the coil-shaped or mesh-shaped anode electrode having a space therebetween, and most of the electrons are supplied to the anode electrode. Caught after passing through over and over. For this reason, the traveling distance of the electrons is longer than in the case of the conventional linear traveling, and the probability of collision between the electrons and gas molecules is increased, and as a result, the sensitivity as a detector is improved.

According to a second aspect of the present invention (corresponding to claim 2), in the electron impact emission spectroscopic detector according to the first aspect, the anode electrode, which is one of the main components that characterize the present invention, comprises a conductive wire. It is composed of a substantially cylindrical member wound in a coil shape. The traveling distance of electrons can be increased by a simple configuration of the anode electrode.

An electron impact emission spectrometer according to a third invention (corresponding to claim 3) is characterized in that the anode electrode in the first invention is a cylindrical member formed by rolling a mesh-shaped conductive thin plate. Fine. The traveling distance of electrons can be increased by a simple configuration of the anode electrode.

According to a fourth aspect of the present invention (corresponding to claim 4), in the electron impact emission spectrometer, the cross section perpendicular to the center axis of the cylindrical anode electrode is substantially circular or substantially elliptical. The electron impact emission spectrometer according to claim 2 or 3, wherein the detector is one of substantially rectangular shapes. A desirable cross-sectional shape of the cylindrical anode electrode is specified.

According to a fifth aspect of the present invention (corresponding to claim 5), in the electron impact emission spectrometer, the anode electrode is formed by arranging two mesh-shaped conductive thin plates in parallel. An electron impact emission spectrometer according to claim 1. The present invention specializes in the configuration of the anode electrode, which is one of the main components that characterize the present invention, other than the above-described tubular cross-sectional shape.

According to a sixth aspect of the present invention (corresponding to claim 6), in the electron impact emission spectrometer, the electron emission electrode is any one of a thermoelectron emission type and a cold cathode type. An electron impact emission spectrometer according to any one of claims 1 to 5,
For each type, an optimum type can be selected according to various given conditions.

According to a seventh aspect of the present invention (corresponding to claim 7), the electron impact emission spectrometer includes a nipple connected to a vacuum vessel,
The electron impact emission spectrometer according to any one of claims 1 to 7, wherein the flange and the heat shield have a ground potential, the electron emission electrode has a higher potential than the ground potential, and the anode electrode has a higher potential than the electron emission electrode. It is. Since the electron emission electrode is higher than the ground potential, the emitted electrons do not jump into the nipple, flange, and heat shield connected to the vacuum vessel at the ground potential, improving the detection sensitivity,
And stable.

[0024]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a typical embodiment of the present invention. In FIG. 1, elements substantially the same as the elements described in FIG. 2 are denoted by the same reference numerals. The port portion of the vacuum vessel 1 has a hole substantially at the center thereof, and a flange 3 covered with a quartz window 4 is hermetically attached via a nipple 2 to surround the hole. The inner area communicates with the vacuum chamber. This is the same configuration as that shown in the conventional example of FIG.

Anode electrode 1 which is one of the features of the present invention
9 is formed in a substantially cylindrical shape or a cylindrical shape obtained by rolling a conductive mesh-like thin plate by winding a conductive wire into a coil shape. In the nipple 2, the center axis of the anode electrode 19 substantially coincides with the center axis of the quartz window 4, which is hermetically sealed to extract light emission from vacuum to the atmosphere, and is insulated from the flange 3. Fixed.

An electron emission electrode 5 is provided on the flange 3.
It is provided so as to penetrate the wall of the flange insulatively and airtightly, and protrude in the nipple 2 in the vicinity of the anode electrode 19 and at a position outside the anode electrode 19.

Light emitted by the electron impact is taken out to the atmosphere side through the quartz window 4, and then, through the optical filter 12, which is a spectral unit, a photoelectric conversion element unit for converting the electric signal into an electric signal is provided on the cylindrical anode electrode 19. It is arranged in the direction of extension of the central axis. That is, the optical filter 12 and the photocathode 14 of the photomultiplier 13 are provided in the case 9 with their central axes substantially coincident with the quartz window 4 attached to the central hole of the flange 3.

At the center of the field of view of the photocathode 14 of the photomultiplier tube 13, there is a space in which the central axis of the anode electrode 19 is viewed in the axial direction, and the slit 16 is arranged so that each part of the vacuum side electrode cannot be seen. This is the same as in the conventional example.

Reference numeral 15 denotes a preamplifier having current-voltage conversion and amplification functions.

The thermionic emission electrode 5 is maintained at a potential higher than the ground potential by the DC power supply 31. The DC power supply 32 is a power supply for heating the thermionic emission electrode 5.
The anode electrode 19 is maintained at a higher potential than the thermionic emission electrode 5 by the DC power supply 33. Anode electrode 19
The connection line 34 between the DC power supply 33 and the flange 3 and the case 9
And is insulated and airtightly fixed to each of them. Further, the nipple 2 and the flange 3 are maintained at the ground potential together with the vacuum vessel 1 and the case 9.

The heat shield 17 is arranged so as to be a partition between the nipple 2 and the other electrode portions, as in the above-described conventional example.

After evacuating the inner region surrounded by the vacuum vessel 1, the nipple 2, the flange 3, and the quartz window 4 having such a structure, when electrons are emitted from the thermionic emission electrode 5 in this vacuum atmosphere, The electrons travel to the anode electrode 19 having a higher potential than the thermionic emission electrode 5. Since the cylindrical anode electrode 19 has a coil-shaped or mesh-shaped structure with a gap in the space, most of the electrons pass through the anode electrode 19, and the electrons passing through the nipple 2 and the flange are ground potential. 3 returns to the direction of the anode electrode 19 having a higher potential than that of the electrode 3. The electrons repeat such a movement, reciprocate, and are eventually captured entirely by the anode electrode 19. When the electrons repeat the reciprocating motion at the anode electrode 19, there is a possibility that the electrons collide with gas molecules or atoms 10 in the space inside the cylindrical anode electrode 19. The space inside the cylindrical anode electrode 19 is used as a detection region in which gas molecules and the like to be detected based on collision exist. In the configuration of the present embodiment, in the detection region, the electrons repeatedly travel, and the traveling distance (traveling time) of the electrons is increased to increase the probability of collision between the electrons and gas molecules. . Therefore, the ratio of electrons that collide with gas molecules or atoms 10 increases, and the partial pressure measurement sensitivity can be increased.

When each gas molecule or atom 10 collides with an electron, it is excited at a specific rate and then lowers its energy level. At that time, light 11 having a wavelength unique to each gas molecule or atom 10 is emitted. The emission of this light is caused by the anode electrode 19.
Is done inside. The emitted light 11 having a specific wavelength passes through the quartz window 4 and exits to the atmosphere. The optical filter 12 is a filter that transmits only light having a wavelength in a narrow band around a specific wavelength, and cannot transmit light having a wavelength other than this wavelength.

The light passing through the optical filter 12 and the slit 16 is incident on the photocathode 14 of the photomultiplier 13 and is converted into a current multiplied by the photomultiplier 13. This current is subjected to current-voltage conversion and amplification by the preamplifier 15,
It is sent to the signal processing system as a voltage signal. Further, a slit 16 and a hole of the flange 3 are arranged so that each part of the vacuum side electrode is not visible in the field of view of the photocathode 14 of the photomultiplier tube 13,
The heat radiation light and the light emission from the electrode part on the vacuum side are prevented from reaching the photocathode 14 and causing noise in measurement. or,
Since the heat shield 17 is arranged so as to be a partition wall between the nipple 2 and other electrode portions, it prevents radiant heat from the electrode portion from being directly radiated to the nipple 2 and heated to a high temperature. These are the same as in the conventional example.

In the above embodiment of the present invention, the anode electrode has been described as having a cylindrical shape. However, unlike the cylindrical shape, the anode electrode may have an elliptical tube shape, a rectangular tube shape, or the like. Alternatively, two flat mesh plates may be arranged in parallel. The anode electrode having these shapes and configurations has a detection area on the inside where electrons collide with gas molecules and the like, and the electrons repeatedly pass through these electrodes by reciprocating motion and travel through the detection area, so that the electron traveling distance is small. The effect that can be lengthened is the same.

Although the electron source is thermionic emission electrode 5, electrons are emitted in the same manner even when a cold cathode electron source using the field emission effect is used.

[0038]

According to the present invention, most of the electrons emitted from the electron emitting electrode reciprocate around the anode electrode 19 many times, so that the distance of the electron traveling 18 becomes longer, and even if the same partial pressure is applied, the electron travels. The probability of collision with gas molecules or atoms 10 before being captured by the anode electrode 19 increases, the intensity of the voltage signal at the same partial pressure is improved as compared with the conventional one, and the sensitivity as a detector is improved. .

[Brief description of the drawings]

FIG. 1 is an embodiment of the present invention.

FIG. 2 is an example of a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Nipple 3 Flange 4 Quartz window 5 Thermionic emission electrode 6 Electron repulsion electrode 7 Mesh electrode 8 Anode electrode, 9 Case 10 Gas molecule or atom 11 Light of specific wavelength 12 Optical filter 13 Photomultiplier tube 14 Photocathode 15 Preamplifier 16 Slit 17 Heat shield 18 Electron traveling 19 Anode electrode

Claims (7)

[Claims] An electron emitted from an electron emission electrode in a vacuum atmosphere collides with gas molecules or atoms present in a detection area in a vacuum atmosphere in a process of jumping into an anode electrode,
Light of a specific wavelength that is emitted when the gas molecule or atom excited by the electron impact lowers the energy level, is received by the photoelectric conversion element via the spectroscopic unit, and the gas molecule or the light is converted at the converted voltage value. In the electron impact emission spectrometer for measuring the partial pressure of atoms, the anode electrode is made of a member through which the electrons can pass, and the detection region is provided in an inner space thereof, and the detection region of the anode electrode includes the detection region. A potential difference is provided between the anode electrode and a peripheral portion thereof so that electrons can reciprocate. 2. The electron impact emission spectral detector according to claim 1, wherein the anode electrode is a substantially cylindrical member formed by winding a conductive wire in a coil shape. 3. The method according to claim 1, wherein the anode electrode is a cylindrical member formed by rolling a mesh-shaped conductive thin plate.
3. The electron impact emission spectrometer according to claim 1. 4. The electron according to claim 2, wherein the shape of the cross section perpendicular to the central axis of the cylindrical anode electrode is one of a substantially circular shape, a substantially elliptical shape, and a substantially square shape. Shock emission spectroscopy detector. 5. The electron impact emission spectrometer according to claim 1, wherein the anode electrode is formed by arranging two mesh-shaped conductive thin plates in parallel. 6. The electron impact emission spectrometer according to claim 1, wherein the electron emission electrode is one of a thermoelectron emission type and a cold cathode type. 7. A nipple, a flange, and a heat shield connected to a vacuum vessel are at a ground potential, an electron emission electrode is higher than the ground potential, and an anode electrode has a higher potential than the electron emission electrode. Item 2. An electron impact emission spectrometer according to item 1.