JPS6086480A - Radiant ray detector - Google Patents

Abstract

PURPOSE:To obtain a mechanically rigid radiant ray detector accurate in size with high detecting accuracy by forming metallic thin films on required surfaces of a scintillator by vacuum deposition or the like. CONSTITUTION:Metallic thin films 9 to be directly coupled with surfaces are formed on respective surfaces of the scintillator 8 other than surfaces guiding light into a semiconductor detecting element 13 which converts light emission due to radiant rays into an electric signal by ion plating method, plasma deposition method, vacuum deposition method or spattering method. Since the reflecting layers based upon the films 9 formed by direct coupling are formed without using coating method which may be easily peeled, the radiant ray detector is mechanically rigid and is precise in size. In addition, the whole light emitted from the scintillator 8 is effectively guided to the element 13, so that the highly sensitive and highly accurate detector is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a radiation detector, such as a radiation detector used in a computed tomography apparatus.

[Technical Background of the Invention and Problems Therewith] Conventionally, a radiation detector in a computed tomography apparatus, such as an X-ray detector in an X-ray CT apparatus, is configured as follows, for example. That is, as shown in FIG.
, width W is 0. It has a scintillator 1 molded into a rectangular parallelepiped with a height t of 2111111 gmm and a semiconductor photodetecting element 5, and a support member 6 is provided with a support member 6 along its longitudinal direction, approximately parallel to the bottom surface of the scintillator 1. By arranging a large number of semiconductor photodetecting elements 5 having the same sensitive portion in parallel at a predetermined pitch, and fixing the bottom surface of the scintillator 1 and the semiconductor photodetecting elements 5 with, for example, a transparent lens adhesive 7, The scintillators 1 are arranged, and between the scintillators 1, the metal foil 2 and the scintillator 1 are connected to each other via a metal foil 2 such as aluminum or lead and an adhesive layer 4 coated on the surface of the scintillator 1. A light-reflecting layer 3 containing titanium dioxide or the like as a main component is interposed between the scintillators 1 and 1, and the light-reflecting layer 3 is applied to the upper surface of each scintillator 1 and the side surface perpendicular to the direction in which the scintillators are arranged. It has a configuration. As shown in FIG. 1, when an X-ray flux X emitted from an The light is detected and photoelectrically converted by the photodetector element 5, and the semiconductor photodetector element 5 is configured to output a current signal proportional to the amount of incident X-rays.

However, the X-ray detector has the following problems. That is, (1) the adhesive @ 4 interposed between the scintillator 1 and the photoreflective layer 3 absorbs part of the light emitted by the scintillator 1, and all of the light emitted by the scintillator 1 is transferred to the semiconductor photodetector element 5; cannot be effectively guided.

Therefore, the sensitivity of the X-ray detector decreases, and the
5. Good X-ray tomographic images cannot be obtained with an X-ray CT device that has a radiation detector on its right side. (2) Since the paint used for the light reflection layer 3 generally contains an organic polymer binder, sufficient adhesion to the scintillator 1 cannot be exerted. Therefore, X-ray detectors lack mechanical robustness. ■In order to prevent X-ray crosstalk, metal materials such as lead, tungsten, or molybdenum are used for the metal foil 2, but lead has low rigidity and tends to separate from the anti-cocoon layer 3. Furthermore, tungsten and molybdenum have too high rigidity and are likely to separate from the scintillator 1. ■Also, since it includes a gluing process, workability is poor.

■Since scintillator 1 has deliquescent properties, it has a light anti-IFI
When applying the layer, part of the scintillator 1 deliquesces and its dimensions become distorted, making it impossible to achieve accurate X-ray detection.

[Object of the Invention] This invention has been made based on the above circumstances, and is a mechanically robust and dimensionally consistent material that can effectively guide all the light emitted within the scintillator to the semiconductor photodetector element. The purpose of this invention is to provide a radiation detector with high detection accuracy.

[Summary of the Invention] The summary of the present invention for achieving the above object is to provide a radiation detector having a scintillator capable of emitting radiation and a semiconductor photodetection element capable of converting light from the scintillator into an electrical signal.
In the 1iFA detector, a metal thin film is formed on each surface of the scintillator except for the surface that guides light to the semiconductor detection element by any one of an ion blating method, a plasma deposition method, a vacuum deposition method, and a sputtering method. It is characterized by this.

[Embodiment of the Invention] An embodiment of the invention will be described with reference to FIG.

A radiation detector, for example, an X-ray detector used in an X-ray CT apparatus, as shown in FIG. 2, includes a scintillator 8 molded to the same dimensions as shown in FIG. Similar to the conventional X-ray detector shown in FIG. A large number of scintillators 8 are arranged in parallel at a predetermined pitch, and the bottom surface of the scintillator 8 and a semiconductor photodetector are fixed with, for example, a transparent lens adhesive 12, so that a large number of scintillators 8 are arranged. . A metal thin film 9 is formed on each surface of the scintillator 8 other than the surface facing the semiconductor photodetector 11, and a metal thin film 9 is formed in the gap between each of the scintillators 8 arranged to connect each scintillator 8. An adhesive 10 is interposed.

The metal 31113!9 is made of one or more metal materials selected from the group consisting of aluminum, silver, lead, tungsten, and molybdenum using a vacuum evaporation method or a plasma evaporation method.
It is formed on the surface of the scintillator 8 by aperture deposition, ion blating, sputtering, or the like. As the gold material of the metal thin film 9, it is particularly preferable to use silver or aluminum, which has a high spectral reflectance in the visible light range. on the surface of
It is preferable to form a thin film of silver or aluminum as a first layer, and then form a thin film of lead, tungsten, or molybdenum with a large X-ray blocking ability as a second layer on the surface of the first layer. .

Next, the formation of the metal thin film on the scintillator 8 by the ion blating method will be described in more detail.

FIG. 3 is a schematic diagram showing the ion blating device.

The ion brating device includes, for example, an exhaust device and a flow rate control valve 1 at the bottom via a flow rate control valve 15a.
A cylinder 16 filled with rare gas such as argon via 6a
An electrode 17 to which a DC voltage is applied by an external DC power supply 19 is disposed above the inside of the vacuum vessel 14, which can be opened and closed, and below the electrode 17, an external high-frequency voltage is applied. High frequency, for example 13.56M, is generated by the power supply 21.
A high frequency coil 20 to which a high frequency of H2 is applied is arranged,
Furthermore, a crucible 22 that accommodates a desired metal material to be evaporated and a heating device (not shown) that heats the crucible 22 are disposed on the bottom surface of the vacuum container 14.

Then, a predetermined metal material is housed in the crucible 22,
After placing the scintillator 8 on the electrode 17, the inside of the vacuum container 14 is evacuated to a high reduced pressure, and rare gas is supplied from the cylinder 16 into the vacuum container 14 to a pressure of 2 to several Torr. , the crucible '22 is heated to a predetermined temperature by a heating device (not shown) inside the vacuum container 14. When high frequency waves are applied to the high frequency coil 20, the rare gas becomes a plasma state inside the vacuum container 14, and the inside of the crucible 22 is heated. Metal atoms in the metal in the metal vapor generated by heating the metal material exchange charges with rare gas ions in a plasma state, and charged metal ions are generated at the electrode 17 by applying direct current. It is attracted by the DC electric field and reaches the scintillator 8 on the electrode 17, thereby forming a metal thin film on the surface of the scintillator 8.The metal thin film thus obtained forms a mirror surface and emits light. It has a large reflective power and also has a large adhesion force to the surface of the scintillator 80, making it suitable as a light reflecting film for the scintillator 8.

Next, the formation of the metal thin film on the scintillator 8 using the plasma deposition method will be briefly described in detail.

FIG. 4 is a schematic diagram showing a plasma deposition apparatus.

The plasma deposition apparatus includes, for example, a flow adjustment valve 31a.
A rare gas cylinder 27 filled with a rare gas through a flow rate adjustment valve 27a, and a cylinder 26 containing an organometallic compound such as trimethylaluminum, aluminum chloride, tetraethyl lead, etc. through a flow rate adjustment valve 26a. It has a support base 30 on which the scintillator 8 is placed in a vacuum container 23 which is coupled with a pair of capacitively coupled electric currents 1i! to which a high frequency is applied by an external high frequency power source 25. i24.

After evacuating the inside of the vacuum container 23 to a high reduced pressure, a gas of an organometallic compound and a rare gas are supplied into the vacuum container 23, and a plasma state is formed in the mixture of these gases by high-frequency discharge between the electrodes 24. metal atoms in a plasma state,
A gold a thin film is formed by contacting the scintillator 8 on the support stand 30. In this case, since the metal thin film is formed at a gas pressure of several Torr, the metal thin film can be suitably formed on the surface of a complex-shaped scintillator, for example, a comb-shaped scintillator as shown in FIG.

Since the X-ray detector of the above embodiment has an adhesive formed on the surface of the scintillator, all of the light emitted by the scintillator is guided to the semiconductor photodetector without loss, which significantly increases detection efficiency. be able to. Moreover,
Since the metal thin film is directly bonded to the scintillator surface, the metal thin film can be easily peeled off from the scintillator surface! it
! First, a robust X-ray detector can be obtained. Furthermore, if the metal film has a two-layer structure, an X-ray detector free from optical crosstalk and X-ray crosstalk can be obtained. Since there is no stone fitting process, assembly work can be simplified and time can be shortened.

Hereinafter, one embodiment of this invention has been described in detail, but this invention is not limited to the above embodiment, and can be implemented with appropriate modifications within the scope of the gist of this invention. Needless to say.

"Effects of the Invention" According to this invention, the complete part emitted by the scintillator can be guided to the semiconductor photodetector without being absorbed by the scintillator.
Therefore, a radiation detector with good sensitivity can be provided. Therefore, when the radiation detector according to the present invention is applied to a computed tomography apparatus, good tomographic images can be obtained. In addition, since the metal thin film is directly bonded and formed on the scintillator surface, the metal thin film does not peel off and is robust. i! A detector can be provided. By forming a metal thin film, a radiation detector free from optical crosstalk and radiation crosstalk can be provided. Furthermore, the metal thin film has 8
3.Since it is formed by vacuum thermal bonding, etc., without depending on the application of a certain anti-fouling layer, it is possible to obtain a scintillator element with accurate dimensions.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing a conventional radiation detector, Fig. 2 is a perspective view showing an embodiment of the present invention, Fig. 3 is an explanatory view showing an ion blating device, and Fig. 4 is a perspective view showing a plasma deposition device. The explanatory drawings shown and FIG. 5 are perspective views showing an example of a radiation detector according to the present invention. 8...Scintillator, 9...Metal thin film, 11...Semiconductor photodetector.

Claims (2)

[Claims] (1) In a radiation detector having a scintillator capable of emitting light with radiation and a semiconductor photodetecting element capable of converting light from the scintillator into an electrical signal, light is guided to the semiconductor detecting element (each surface of the scintillator except the surface A radiation detector characterized in that a metal thin film is formed by any one of an ion blasting method, a plasma deposition method, a vacuum deposition method, and a sputtering method. (2) Radiation detection according to claim 1, wherein the metal thin film is made of one or more metals selected from the group consisting of aluminum, silver, lead, tungsten, and molybdenum. vessel.