JPH01239749A - Charged particle detector - Google Patents

Abstract

PURPOSE:To make the assembly and the regulation works easier and to multiply the number of releasing electrons remarkably by binding and composing plural taper-form channel tubes for electron multiplying purpose in an unparallel and tapered form. CONSTITUTION:Since channel tubes 21,... are formed in a taper-form making the diameters smaller as they approach the electron injection side, the distances between passages of the secondary electrons are shortened as the secondary electrons advance inside the channel tubes 21,..., and the striking numbers of them are multiplied indicatively. Furthermore, not only the channel tubes 21,... are formed in a taper-form, but also the whole electron multiplying tube is formed in a so-called taper-form forming unparallel and making the particle incident side higher while the electron output side lower. As a result, the taper- form coefficient is increased, and the numbers of striking of the secondary electrons are increased much more. And since the size of the electron output side is small as a whole even though numerous channel tubes 21,... are bound, the assembly and the regulation works are made much easier.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a charged particle detector suitable for nuclear fusion measurement technology such as neutral particle meter n1 and other radiation measurements, and in particular, This invention relates to a charged particle detector that eliminates problems with assembly, adjustment, etc., and has improved electron amplification function.

(Prior Art) Conventionally, there are two types of charged particle detectors of this type: a Ceratron detector and a microchannel plate detector.

The former Ceratron detector, as shown in FIGS. 6 and 7, has a plurality of support members 2, 2 having support and terminal functions installed upright at both ends of a flat insulating base 1 of a predetermined length. An alumina tube 3 having an inner diameter of about 21 mm and a length of about 100 mm formed into a wave or spiral shape is provided in between, and the inner wall of the alumina tube 3 is coated with a thin oxide film (M g O etc.) that causes secondary electron emission. Coated. An accelerating electrode 4 and a bias electrode 5 are provided on the charged particle entrance side and the electron exit side of the alumina tube 3, respectively, and lead wires are led out from these electrodes 4 and 5 to connect the support member 2. It is fixed to...

Furthermore, about 0.1 from the electron exit side of the alumina tube 3
A collector 6 is arranged at an opposing position separated by about mII, and after the output electrons from the electron exit are converted into an electric signal by the collector 6, they are introduced into the preamplifier through a capacitor 7. 8 is an acceleration power source, and 9 is a bias power source.

Therefore, in the Ceratron detector as described above, when a charged particle a is incident from the entrance side with the acceleration power source 8 and the bias power source 9 applied, the charged particle a passes through the alumina tube 3 which has an electron multiplication function. They collide with the oxide thin film on the inner wall and emit a plurality of secondary electrons. This alumina tube 3
The secondary electrons emitted on the inner wall of By repeating the operation many times, a large number of multiplied secondary electrons are emitted.

On the other hand, the latter microchannel plate detector is constructed by uniformly tilting a large number of lead glass channel plates 11 coated with a thin oxide film and having an inner diameter of about 12 μm, as shown in FIG. 8 and 'MS9. It has a flat plate configuration in which channel plates 11°... are bundled in parallel. 12 is alumina, and 13 is a screw.

This microchannel plate detector includes each channel plate 11. Each has an independent secondary electron multiplication function, and hydrogen reduction is performed after plate production to increase the secondary electron emission rate.

This microchannel detector also operates in the same way as the Ceratron detector, emitting a large number of electrons while multiplying the secondary electrons emitted from the inner wall of the plate.

(Problems to be Solved by the Invention) However, the above-mentioned detector has a complicated overall structure and has the following problems in order to improve detection performance.

(2) In the microchannel plate detector, since the inner diameter of each channel plate 11 is about 10 μm, not only is the production cost high, but also the yield is very poor because variations in the production process directly result in variations in the product.

(2) Furthermore, the gap between the electron exit port of each detector and the collector 6 must be maintained at 0.1 mm and set parallel to each other, which requires a long time to assemble and adjust.

■ Also, alumina tube 3 and channel play 111
．． The inner diameter of ... may be very small and air may be trapped inside, so it is necessary to age it before use.

■, Furthermore, for the same reason as ■, high vacuum region, for example 1O
- Difficult to use in 6to, 1 environment.

The present invention has been made in order to improve the above-mentioned problems, and aims to provide a charged particle detector that is easy to assemble and adjust, and can dramatically improve the secondary electron multiplication function. purpose.

[Structure of the Invention] (Means for Achieving the Object) The present invention includes a plurality of tipper-shaped electron multiplier channel tubes coated with a secondary electron emitting material so as to be non-parallel and have a tipper. The bundled configuration 1 is a charged particle detector.

(Function) Therefore, the present invention has the above-mentioned means.
Charged particles incident from the charged particle entrance collide with the inner wall of each channel tube and emit secondary electrons, but each channel tube is converged toward the electron exit hole, and multiple channel tubes Since the bundle is non-parallel and has a tipper-like structure, the number of electron collisions increases as it approaches the electron exit side, and the number of emitted electrons can be increased exponentially.

(Example) An example of a charged particle detector according to the present invention will be described below with reference to FIGS. 1 and 2. In these figures, 21 has a large aperture on the charged particle entrance side and a small aperture on the electron exit side. It is an electron multiplier channel tube with a circular cross section formed in a so-called tipper shape, and is made of quartz glass, alumina, ceramic, etc., and its inner surface has a 2-layer tube with an appropriate resistance value.
It is coated with a secondary electron emitting material such as magnesium oxide (MgO). By the way, the electron multiplier tube is
A plurality of electron multiplier channel tubes 21 as described above.・
It is composed of bundles of... in a non-parallel manner and has a tipper shape.

Each channel tube 21. The charged particle incident surface and electron exit surface of ... are set at the same surface position. In addition, in actual manufacturing, a plurality of channel pipes 21. . . . are bundled non-parallelly in a tipper shape and cut so that each end becomes the same plane. A predetermined number of these channel pipes 21. A ring-shaped accelerating electrode 22 is provided on the outer periphery of the charged particle incident end side of the electron multiplier tube configured by . . . so as to bind a large number of channel tubes 21, . Similarly, a large number of channel pipes 21. A ring-shaped bias electrode 23 is provided to bind the...

Then, after being bundled, several channel pipes 21°...
The charged particle entrance side is inserted and fixed into the circular hole 25a of the accelerating electrode power supply plate 25 erected on one end side of the flat insulating base 24, while the electron exit side is fixed by the supporting member 26. It is installed at a position sufficiently lower than the particle entrance side, or it is installed directly on the insulating base 24. This support member 26 also has the function of a power supply terminal for a bias power supply. A metallic collector 27 collects electrons emitted from the electron exit aperture of the electron multiplier tube, and is disposed opposite to the electron exit aperture at a position slightly away from the electron exit aperture. Reference numeral 28 denotes an insulating support post that is erected on the insulating base 24, fixes the ml collector 27, and has the function of a signal output terminal 29 from the collector 27.

In the above charged particle detector, an acceleration power source 31 of, for example, 5000 V is applied between the acceleration electrode 22 and the bias electrode 23, and a bias power source 32 of about 100 to 150 V is applied between the bias electrode 23 and the collector 17. The collector 27 is also connected to a preamplifier 34 via a capacitor 33. In the figure, 35 is the output electron flow.

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

First, after applying a predetermined voltage between the electrodes 22 and 23 and between the electrode 23 and the collector 27, the charged particles 36 enter the entrance side of the electron multiplier tube at an angle at which they collide with the inner wall of each channel tube 21. Here, the charged particles 36 that have entered into each channel tube 21 collide with the inner wall of the tube and emit secondary electrons 37, but these emitted secondary electrons are
The charged particles 31 are accelerated by the potential gradient of the incident charged particles 31, and progress while drawing a parabolic trajectory determined by the initial velocity of the incident charged particles 36, and emit secondary electrons while constantly colliding with the inner wall on the opposite side.

Therefore, in the device of the present invention, each channel pipe 21
．． . . are formed in a tipper shape so that the closer they get to the electron exit side, the smaller the diameter of the channel tubes 21 . As it progresses into the interior of ..., its orbital distance becomes shorter, and the number of collisions increases exponentially, resulting in the number of emitted electrons expressed by the following formula: . That is, in the conventional device, the number of emitted electrons is nm, but in the device of the present invention, it is (nlll
)K, and the synergistic effect of multiplying the number of emitted electrons is more pronounced than in the conventional case. In the above equation, n is the number of incident charged particles, 1 is the number of collisions, and k is the tipper coefficient (
k<1).

Moreover, this device has each channel tube 21. Not only are the electron multipliers tipper-shaped, but the electron multiplier tube as a whole is also non-parallel, and, for example, the particle entrance side is made higher and the electron exit side is made lower. Since it is formed in a so-called tipper shape, the tipper shape coefficient increases and the number of collisions of secondary electrons increases. In addition, the inner diameter is smaller and more uniform than before.
There is no need for a thicker one, and the particle entrance side only needs to be made larger than the electron exit side, so manufacturing variations do not become such a problem and the problem of yield can be solved. In addition, since the electron exit side is small as a whole even if a large number of channel tubes 21, etc. are bundled, the entire exit exit and the collector are parallel with a gap of about 0.1+nm, as in a conventional microchannel plate detector. It is very easy to assemble and adjust compared to other products. moreover,
Since the aperture of each channel tube 21 on the side of the charged particle entrance is large, aging before use is unnecessary, and the usable vacuum area is as wide as 10"'t or less.

Note that the present invention is not limited to the above embodiments.
That is, the one in FIG. 1 has a channel pipe 2 with a circular cross section.
1 was used, and the cross section of the entire electron multiplier tube was also circular. However, as shown in FIGS. 3 and 4, for example, each channel tube 21a, . It is also possible to use a quadrangular pyramid-like structure having a multilayer structure in which a large number of them are formed and stacked one on top of the other. Further, as the electron multiplier tube, a triangular type as shown in Fig. 5(a), a hemispherical type as shown in Fig. 5(b), or a polygonal type as shown in Fig. 5(C) may be used. . It goes without saying that the structures shown in FIGS. 3 and 5 are non-parallel and tipper-shaped as a whole, similar to the structure shown in FIG. In addition, the present invention can be implemented with various modifications without departing from the gist thereof.

[Effects of the Invention] As detailed above, according to the present invention, by bundling a large number of tipper-shaped channel pipes in a non-parallel and tipper-shaped manner, assembly and adjustment work is easy;
It is possible to provide a charged particle detector that can greatly increase the number of emitted electrons by increasing the number of collisions of secondary electrons, and can greatly increase the number of emitted electrons compared to conventional ones, and can also expand the usable vacuum region.

[Brief explanation of the drawing]

Figures 1 and 2 are shown to explain one embodiment of a charged particle detector according to the present invention. Figure 1 is a partially cutaway external perspective view, and Figure 2 is a diagram showing a state in which a voltage is applied. 3 and 4 show other embodiments of the device of the present invention, and FIG. 3 is an external perspective view,
Fig. 4 shows 21... Channel tube, 22... Accelerating electrode, 23... Bias electrode, 25... Accelerating electrode power supply plate, 26... Power supply terminal, 27... Collector, 28...
...Insulating pillar, 31...Acceleration power source, 32...Bias power source, 35...Output electron flow, 36...Charged particle, 37...Secondary electron. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 (a) (b) Figure 6 Figure 8

Claims (1)

[Claims] A charged particle detector characterized in that a plurality of tipper-shaped electron multiplier channel tubes coated with a secondary electron emitting material are bundled in a non-parallel manner so as to have a tipper.