JPH02304390A - Particle detector - Google Patents

Abstract

PURPOSE:To detect the incident particle with high sensitivity by providing a secondary electron emission plate for emitting a secondary electron when the incident particle is emitted through one piece of incident port, and a constitution which can apply an electric field in the direction coinciding with the direction of a magnetic field. CONSTITUTION:An incident particle such as a neutral particle, a charged particle, etc., irradiates a secondary electron emission plate 1 through an incident port 0, and a secondary electron is generated. On the other hand, by applying a voltage between the secondary electron emission plate 1 and an acceleration electrode 2 from an acceleration power source 3, the secondary electron is accelerated in the direction of a line of magnetic force to irradiate a fluorescent screen 4 and light is generated, and this light is condensed by a condensing lens 5. Subsequently, this light is detected by a photodetector 7. In this case, in the acceleration electrode 2, since an electric field is applied in the direction coinciding with the direction of a magnetic field B, the electron is accelerated in a shape wound to the line of magnetic force, therefore, it does not occur that deterioration of sensitivity caused by a magnetic field is generated.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) The present invention relates to a particle detector that detects incident particles such as neutral particles and charged particles, and particularly relates to a particle detector that detects incident particles even in a strong magnetic field. The present invention relates to a particle detector capable of easily detecting particles.

(Prior Art) Conventionally, particle detectors for detecting incident particles such as neutral particles and charged particles include Ceratron detectors or microchannel detectors that use a method of multiplying secondary electrons caused by incident particles. have been widely adopted.

The Ceratron detector is made of ceramic whose inner surface is coated with a secondary electron emitting material, and a voltage is applied between the tip of the opening and the end of the helical tube that follows the trumpet-shaped opening. Ru. The incident particles hit the inner surface of the trumpet and generate secondary electrons, and the applied magnetic field causes the particles to collide with the inner surface of the helical tube many times, causing the electrons to be multiplied. and,
These electrons are emitted from the end of the helical tube, are collected at the collector by the electric field between them, are amplified as a signal by a preamplifier, and are counted by a counter. On the other hand, a microchannel detector is made of a plurality of glass pipes, each of which has an inner surface coated with a secondary electron emitting material, arranged in parallel, to which a voltage is applied. The incident particles hit the inner surface of the vibrator and generate secondary electrons, which are multiplied by colliding with the inner surface of the pipe many times due to the applied magnetic field and counted by a counter.

However, when these detectors are operated in a magnetic field of "1", the orbit of the 7-pole during secondary electron multiplication wraps around the magnetic field lines, and in the case of the Ceratron detector, it is several tens of Gauss, In the case of microchannel detectors, sensitivity decreases at a few hundred Gauss, and at higher frequencies the decrease in sensitivity becomes so pronounced that incident particles cannot be detected with good sensitivity. For example, 1
Gauss or higher) is applied, the electrons can only move along the magnetic field lines, so in the extreme case if a magnetic field is applied perpendicular to the trumpet tube, the secondary electrons will not enter the helical tube. Therefore, the original electron multiplication is no longer performed. Furthermore, in the case of a microchannel detector, although the shape is different, the principle is exactly the same, so when secondary electrons wrap around magnetic lines of force, the original electron multiplication does not occur, and the multiplication factor decreases.

(Problems to be Solved by the Invention) As described above, conventional particle detectors have a problem in that their sensitivity decreases significantly in a strong magnetic field, making it impossible to detect incident particles.

An object of the present invention is to provide a highly reliable particle detector that operates reliably even in a strong magnetic field and can detect incident particles with extremely high sensitivity.

[Composition 114 of the invention] (Means for solving the problem) In order to achieve the above object, incident particles such as neutral particles and charged RV particles are placed in a magnetic field in a direction different from the direction of the incident particles. In the first aspect of the present invention, a particle detector for detecting particles includes a secondary electron emitting plate that emits secondary electrons when an incident particle is irradiated through one entrance port, and an electric field that applies an electric field in a direction that coincides with the direction of the magnetic field. An accelerating electrode that accelerates electrons emitted from the secondary electron emission plate, a fluorescent plate that converts the electrons accelerated by the accelerating electrode into light, and a photodetector that detects the light from the fluorescent plate. In the second aspect of the present invention,
It has a secondary electron emitting plate that emits secondary electrons when incident particles are irradiated through N (N is an integer of 2 or more) entrance ports, and a configuration that can apply an electric field in a direction that matches the direction of the magnetic field. There is an accelerating electrode that commonly accelerates each electron emitted from the secondary electron emission plate, N fluorescent plates that individually convert each electron accelerated by the accelerating electrode into light, and the light from each fluorescent plate. It is configured to include N photodetectors that individually detect each one, and a data processing means that receives output signals from each photodetector and calculates the spatial distribution of particles based on these.

(Function) Therefore, in the particle detector of the first aspect of the present invention, when an incident particle is irradiated onto the secondary electron emission plate, secondary electrons are generated,
Secondary electrons are emitted in a direction along the magnetic field. These secondary electrons are accelerated by the electric field generated by the accelerating electrode, strike the fluorescent screen, and generate light, which is detected by a photodetector.

In this case, in the accelerating electrode, an electric field is applied in a direction that coincides with the direction of the magnetic field, and the electrons are accelerated while being wrapped around the lines of magnetic force, so there is no reduction in sensitivity due to the magnetic field. Moreover, in the particle detector of the second invention, in addition to the action of the particle detector of the first invention,
Based on the output signal from each photodetector, the spatial distribution of particles will be determined.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an example of the configuration of a particle detector according to the present invention. As shown in the figure, the particle detector of this embodiment includes a secondary electron emission plate 1, an accelerating electrode 2, and an accelerating electrode. It consists of a tS source 3, a fluorescent screen 4, a condenser lens 5, an optical cable 6, and a photodetector 7.

Here, the secondary electron emitting plate 1 is made of, for example, BeCu or the like, and emits secondary electrons when incident particles are irradiated through the entrance 0. In addition, the accelerating electrode 2 has a magnetic field B
It has a configuration that can apply an electric field in a direction that coincides with the direction of
It accelerates the electrons emitted from the secondary electron emission plate 1. Further, in the acceleration 7, the source 3 is connected to the secondary electron emission plate 1 and the accelerating electric current l! 1II2, a voltage is applied with the polarity shown.

On the other hand, the fluorescent screen 4 converts electrons accelerated by the accelerating electrode 2 into light. Further, the condenser lens 5 is connected to the fluorescent screen 4.
It focuses the light from the Furthermore, optical cable 6
is for transmitting the light focused by the condenser lens 5. Furthermore, the photodetector 7 is made of, for example, an otomaru or semiconductor detector, and is installed in a place without a magnetic field.
It detects light transmitted through the optical cable 6.

Next, the operation of the particle detector configured as above will be explained.

In Figure 1, incident particles such as neutral particles 2 charged particles are
The secondary electron emission plate 1 is irradiated through the entrance aperture 0, thereby generating secondary electrons. These secondary electrons are emitted in the direction along the magnetic field B while being wrapped around the magnetic field lines (the energy of the secondary electrons is at most 100 eV, and the spread of the electrons is about the Larmor radius, so the magnetic field B is If it is more than Gauss, it will be less than 1■). On the other hand, secondary electron emission plate 1
By applying a voltage from the accelerating power source 3 between the accelerating electrode 2 and the accelerating electrode 2, secondary electrons are accelerated in the direction of the magnetic field lines, and the fluorescent screen 4 is irradiated to generate light, which is focused by the condensing lens 5. be illuminated. This light is then transmitted through the tip cable 6 to a photodetector 7 installed in a place where there is no magnetic field, and detected by the photodetector 7. In this case, in the accelerating electrode 2, an electric field is applied in a direction that coincides with the direction of the magnetic field B, so that electrons are accelerated while being wrapped around the magnetic lines of force, so there is no reduction in sensitivity due to the magnetic field.

In the case of this particle detector, the condition is that the direction of incidence of the incident particle and the direction of the magnetic field B are at right angles or different.

This is because current neutral particle analyzers use electromagnets with iron cores, but when measuring plasma in the fusion reaction region, it is necessary to measure particles of several M e V. It is necessary to use an air-core coil of superconducting wire.

As a result, the magnetic field cannot have a sharp distribution, and a particle detector must be placed in the magnetic field. At this time, the magnetic field and the direction of the particles are at right angles.

As described above, the particle detector of this embodiment includes a secondary electron emission plate 1 that emits secondary electrons when an incident particle is irradiated through the entrance port 0, and an electric field that applies an electric field in a direction that coincides with the direction of the magnetic field B. an accelerating electrode 2 that has a configuration that allows voltage to be applied and accelerates electrons emitted from the secondary electron emission plate 1; an acceleration power source 3 that applies a voltage between the secondary electron emission plate 1 and the acceleration electrode 2; A fluorescent screen 4 that converts electrons accelerated by the accelerating electrode 2 into light, a condensing lens 5 that condenses the light from the fluorescent screen 4, an optical cable 6 that transmits the light condensed by the condensing lenses, and a magnetic field. The optical detector 7 is installed in a place where there is no traffic light, and a photodetector 7 detects the light transmitted through the optical cable 6.

Therefore, since the direction of the magnetic field B and the direction of the electric field are made to match, the electrons can be accelerated while being wrapped around the lines of magnetic force, and sensitivity does not decrease due to the magnetic field B. Therefore, the particle detector operates reliably even in a strong magnetic field of IK Gauss or higher, making it possible to detect incident particles with extremely high sensitivity.

In addition, since the light focused by the condenser lens 5 is transmitted through the optical cable 6 to the photodetector 7 installed in a place without a magnetic field, particle detection can be performed while improving the anti-noise automatic train control device. becomes possible.

Next, other embodiments of the present invention will be described.

FIG. 2 is a diagram showing another example of the structure of the particle detector according to the present invention. As shown in the figure, the particle detector of this embodiment includes a secondary 71iT emission plate 11, an accelerating electrode 12, and an accelerating power source 13.
, N fluorescent screens 14 , light shielding plate 15 , and end cable 1
6, N photodetectors 17, and a data processing device 18 (14), which is a multi-channel particle detector. Here, N is an integer of 2 or more, and the number of channels is Equivalent to.

Here, the secondary electron emission plate 11 emits secondary electrons when incident particles are irradiated through the N entrance ports 10. Further, the accelerating electrode 12 has a configuration capable of applying an electric field in a direction that coincides with the direction of the magnetic field, and
It accelerates the electrons emitted from 1. moreover,
The accelerating power source 13 applies 76 voltage between the secondary electron emission plate 11 and the accelerating electrolyte 12 with the illustrated polarity. On the other hand, the fluorescent screen 14 individually converts each electron accelerated by the accelerating electrode 12 into light. In addition, light shielding plate 1
Numeral 5 is for blocking light so that the individual lights from each fluorescent screen 14 are not mixed together. Furthermore, the optical cable 16 is a bundle type optical cable (a large number of optical cables are bundled into square parts as shown in 1 to N in the figure for the input side, and the output side is one optical cable for each channel), The light converted by the fluorescent screen 14 is transmitted. Further, the photodetectors 17 are installed in places where there is no magnetic field, and individually detect the light transmitted through the optical cable 16. Furthermore, the data processing device 18 uses the output signals from each photodetector 17 as human power, determines the spatial distribution of particles based on these signals, and displays it.

Next, the operation of the particle detector configured as above will be explained.

In Figure 1, incident particles such as neutral particles and charged particles are
The secondary electron emission plate 11 is irradiated through the N incident ports 10, thereby generating secondary electrons. This secondary electron is
It is emitted in the direction along the magnetic field B in the form of being wrapped around magnetic lines of force. On the other hand, between the secondary electron emission plate 11 and the accelerating electrode 2,
By applying a voltage from the accelerating power source 3, the secondary electrons are commonly accelerated in the direction of the lines of magnetic force, and are irradiated onto the fluorescent screen 14 to generate light. Then, the light from each fluorescent screen 14 is transmitted through the end cable 16 to each photodetector 17 installed in a place without a magnetic field, with the light shielding plate 15 preventing the lights from mixing. 1
Detected at 7. Furthermore, the individual output signals from each photodetector 17 are input to a data processing device 18, based on which the spatial distribution of particles is determined, and the result is displayed on a CRT device or the like. In this case, in the accelerating electrode 12, an electric field is applied in a direction that matches the direction of the magnetic field B, and the electrons are accelerated while being wrapped around the magnetic lines of force, so the decrease in sensitivity due to the magnetic field will not occur as described above. do not have.

This particle detector uses an external magnetic field to focus secondary electrons, and since the blur of electrons is reduced to less than 1 city, it is possible to achieve spatial resolution easily. That is, if the electron blur is small, crosstalk between channels can be reduced even if each channel is made smaller, and spatial resolution can be improved by increasing the number of channels. Therefore, with the particle detector of this embodiment, in addition to the above-mentioned effects, it is possible to grasp the spatial distribution of particles.

In the above embodiment, a condenser lens and an optical cable were used to transmit the light from the fluorescent screen to a photodetector installed in a place without a magnetic field, but if transmission is not necessary, the fluorescent screen A configuration may also be adopted in which the light from the source is directly detected by a photodetector.

[Effects of the Invention] As described above, according to the present invention, a highly reliable particle detector that operates reliably even in a strong magnetic field and can detect incident particles with extremely high sensitivity can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of a particle detector according to the present invention, and FIG. 2 is a block diagram showing another embodiment of the particle detector according to the present invention. 0.10...Incidence aperture, 1,11...Secondary electron emission plate, 2.12...Acceleration electrode, 3,13...Acceleration power source,
4゜14... Fluorescent screen, 5... Condensing lens, 6,16
...Optical cable, 7.17...Photodetector, 15...
- Light shielding plate, 18 - Data processing device.

Claims (2)

[Claims] (1) In a particle detector that detects incident particles, such as neutral particles and charged particles, in a magnetic field in a direction different from the direction of the incident particles, when the incident particles are irradiated through one entrance, secondary particles are generated. a secondary electron emission plate that emits electrons; an accelerating electrode that has a configuration capable of applying an electric field in a direction that matches the direction of the magnetic field and accelerates the electrons emitted from the secondary electron emission plate; A particle detector comprising: a fluorescent screen that converts electrons accelerated by an electrode into light; and a photodetector that detects light from the fluorescent screen. (2) In a particle detector that detects incident particles such as neutral particles and charged particles in a magnetic field in a direction different from the direction of the incident particles, the incident particles are detected through N (N is an integer of 2 or more) entrance ports. A secondary electron emitting plate that emits secondary electrons when particles are irradiated; and a configuration capable of applying an electric field in a direction that matches the direction of the magnetic field, each electron emitted from the secondary electron emitting plate. an accelerating electrode that commonly accelerates the electrons, N fluorescent screens that individually convert each electron accelerated by the accelerating electrode into light, and N photodetectors that individually detect the light from each of the fluorescent screens. A particle detector comprising: a data processing means that receives output signals from each of the photodetectors and calculates the spatial distribution of the particles based on these signals.