JP2930466B2 - 2D image radiation detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a detection unit of a radiation camera for detecting the shape or output density distribution of a radiation source such as X-rays or gamma rays as a two-dimensional image with high sensitivity.
It is useful when applied to space telescopes in artificial satellites, observatories, etc., in addition to various industrial radiation cameras.

[0002]

2. Description of the Related Art Conventionally, there has been an image intensifying detector (camera) for detecting a two-dimensional image of visible light with high sensitivity. Absent.

FIG. 3 shows a configuration of an image intensifying detector for weak visible light. In FIG. 3, the entire front opening of the cylindrical vacuum vessel 2 is closed by a glass entrance window 11, and a micro channel plate (Micro Channel Plate; a sensitive part) is provided in front of the rear opening of the vacuum vessel 2.
(Hereinafter abbreviated as MCP) 3 and a fluorescent screen 4 are provided,
The optical fiber plate 5 is inserted into the rear opening of the vacuum vessel 2 and the whole is vacuum-sealed.

In operation, light 13 generated from a visible light source 14 is imaged on a microchannel plate 3 in a vacuum vessel 2 by an optical lens 12 and amplified and visualized by the microchannel plate 3 and a fluorescent screen 4.
CCD (Charge Coupled) through the optical fiber plate 5
Device) Light is incident on the element 6.

[0005]

The conventional image-enhanced detector cannot detect a two-dimensional image of low-energy X-rays or weak X-rays. The reasons are shown in (1) and (2) below. (1) Since the entrance window 11 is made of glass for transmitting visible light, radiation such as X-rays has a large absorption loss in the glass,
Therefore, detection of low energy radiation is not possible. (2) Since the entire front opening of the vacuum vessel 2 is closed by the entrance window 11, the thickness of the glass needs to be increased, and the attenuation of radiation increases accordingly.
It is difficult to detect weak X-rays.

The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to provide a two-dimensional image radiation detector with high sensitivity.

[0007]

According to the present invention, there is provided a two-dimensional image radiation detector comprising: a vacuum vessel having a radiation entrance window made of a material such as beryllium foil which absorbs less radiation than glass; A pinhole member close to the entrance window and a CsI
A microchannel plate and a fluorescent plate coated with a substance having a small work function and an optical fiber plate provided behind the fluorescent plate through the vacuum vessel wall,
CCD coupled to optical fiber plate outside vacuum vessel
And an element. In this case, the vacuum vessel may be provided with a bellows for varying the distance between the pinhole member and the microchannel plate.

[0008]

[Action]

 (1) Radiation such as electron beam and X-ray is vacuumed through the entrance window.
Once inside the vessel, the microchannel is
Image on the plate, where it is amplified by electron multiplication
Visible when the multiplied electrons hit the fluorescent screen and emit light.
Optical signal passes through the fiber optic plate
It is guided to an external CCD element and becomes a video signal. Bellows
If there is a pinhole member and microchannel press
By changing the distance to the port, the imaging magnification changes. (2) In this case, the entrance window is made of glass such as beryllium foil.
Is made of a material with low radiation absorption loss.
Low loss when passing through the window, improving detection sensitivity
Noh. (3) Also, a pinhole member is provided near the entrance window.
Therefore, the opening area of the entrance window is
The very narrow required is sufficient, and therefore the thickness of the entrance window
Can be made thinner, and radiation attenuation
Detect low energy and weak radiation
Can be. In addition, the plate thickness of the entrance window
In the case of a circular flat plate fixed to the periphery under the cloth load, its maximum bending
Stress σ _maxIs σ_max= (3/4) (ωR^Two) / T^Two Here, ω: Uniformly distributed load R: Radius of flat plate t: Thickness of flat plate
By reducing to 1/30 to 0.5mm, the thickness is reduced to 1/3
0, and the attenuation due to the material of the entrance window
Reduce.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1 shows a configuration of a two-dimensional image radiation detector according to a first embodiment of the present invention. In FIG. 1, only a part of the center of the front surface of a small cylindrical vacuum vessel 2 has an opening with a small area, and this narrow opening is formed by using a thin plate of a material having good radiation transmittance such as beryllium (Be) foil. The entrance window 1 having a small opening area is closed. 1A is a fixture for the entrance window 1. A pinhole member 7 such as lead or gold having a pinhole 7A is brought into contact with the entrance window 1 by a vacuum container 2.
It is fixed inside. An optical fiber plate 5 is inserted and fixed in the rear opening of the vacuum vessel 2, and a CCD element 6 is connected to an output end of the optical fiber plate 5 outside the vacuum vessel 2. In the vacuum vessel 2, a microchannel plate 3 and a fluorescent plate 4 which are superposed are arranged and fixed at an input end of an optical fiber plate 5. The vacuum container 2 is vacuum-sealed by the entrance window 1 and the optical fiber plate 5.

In the operation of the first embodiment, the radiation source 9
Radiation 8 such as X-rays enters the vacuum vessel 2 through a thin and small entrance window 1 such as beryllium foil and forms an image on the microchannel plate 3 through a pinhole member 7. At this time, the radiation of the two-dimensional image generates electrons in the microchannel plate 3 and is amplified by an electron multiplying action. The multiplied electrons impinge on the fluorescent screen 4 to emit light, thereby being visualized, and the optical signal is guided through the optical fiber plate 5 to the outside of the vacuum vessel 2, that is, to the CCD element 6 in the atmosphere, to become a video signal.

[Second Embodiment] FIG. 2 shows a configuration of a two-dimensional image radiation detector according to a second embodiment of the present invention. The configuration of this embodiment is the same as the first embodiment shown in FIG. 1 except that the vacuum vessel 2 is divided into two parts and connected by a bellows 10. Therefore, redundant description is omitted. That is, the bellows 10 has the pinhole 7A and the microchannel plate 3
It is provided at a position where the distance between them can be varied. Therefore, the imaging magnification can be changed by changing the length of the vacuum container 2 by expanding and contracting the bellows 10.

Here, the microchannel plate 3 will be described with reference to FIG. In FIG. 4A,
The fluorescent plate 4 is superimposed on the two microchannel plates 3, and the microchannel plate 3 has a large number of channels 3A, which are fine small holes, arranged two-dimensionally, as shown in FIG. 3A for each channel
Applying a voltage V _D across ends of incident and its exit end. The photocathode, which is the channel wall 3B, is coated with a material having a small work function such as CsI. Therefore, the output electrons are multiplied by the radiation incident on the channel 3A and being repeatedly reflected on the channel wall 3B.

The radius of the entrance window 1 of beryllium foil or the like is, for example, 0.5 if the radius of the vacuum vessel 2 is 15 mm.
It is extremely small, such as mm.

[0015]

According to the two-dimensional image radiation detector of the present invention, since the entrance window is made of a material such as beryllium which has extremely small radiation absorption loss as compared with conventional glass, low energy or weak radiation can be obtained. Could be detected. In addition, since the pinhole member is provided in contact with the entrance window in the vacuum vessel, the entrance window can be made smaller, and thus the plate thickness can be reduced, so that low-energy or weak radiation can be detected with high sensitivity. I was able to. Also, by varying the distance between the pinhole and the microchannel plate with the bellows, the size (imaging magnification) of the image formed on the microchannel plate can be adjusted, and the degree of freedom of two-dimensional image radiation detection is increased. Increased.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a two-dimensional image radiation detector according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a two-dimensional image radiation detector according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a conventional image enhancement detector.

FIG. 4 is an explanatory view of a microchannel plate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection window 2 Vacuum container 3 Microchannel plate 4 Fluorescent plate 5 Optical fiber plate 6 CCD element 7 Pinhole member 7A Pinhole 8 Radiation 9 Radiation source 10 Bellows

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01J 31/50

Claims (2)

(57) [Claims] 1. A vacuum vessel having a radiation entrance window made of a material such as beryllium foil, which has a smaller radiation absorption loss than glass, and pinholes respectively provided in the vacuum vessel and adjacent to the entrance window. CsI on member and photocathode
A microchannel plate and a fluorescent plate coated with a substance having a small work function and an optical fiber plate provided behind the fluorescent plate through the vacuum vessel wall,
CCD coupled to optical fiber plate outside vacuum vessel
Two-dimensional imaging radiation detector comprising: 2. The two-dimensional image radiation detector according to claim 1, wherein the vacuum container has a bellows for changing a distance between the pinhole member and the microchannel plate.