JPS5948354B2 - Ionization chamber type X-ray detector and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an X-ray detector, particularly an ionization chamber type X-ray detector suitable for use in a computerized X-ray tomography apparatus, and a method for manufacturing the same.

Conventionally, an ionization chamber type detector that measures the spatial distribution of X-ray photons has been used as a detector for this type of device.

The general structure of this detector is as shown in FIG. 1, and these electrodes are encapsulated in an electron-rich gas (for example, xenon gas) at a pressure in the range of about 10 to 50 atmospheres.

Note that the X-rays are incident from the direction of the arrow in FIG. 1A.

FIG. 1B is a diagram schematically showing an electrode section of the ionization chamber type X-ray detector shown in FIG. 1A.

In the figure, two electrode holding plates 1 each having grooves 5 formed in an insulating material at predetermined intervals are arranged vertically at a constant interval, and anode electrodes 2 and cathode electrodes 3 are inserted alternately into the grooves 5. Then, it is fixed with adhesive 4 inside the groove.

In such a detector, if the density of the detection elements is to be increased, the electrode spacing d must be reduced, which naturally shortens the creepage distance of the insulator.

Therefore, in this state, it becomes difficult to maintain the insulation resistance between the anode electrode 2 and the cathode electrode 3 at a high value, and the dark current from the anode electrode 2 flows along the insulator surface to the cathode electrode 3. Therefore, it is difficult to stably detect the signal current from the cathode electrode 3.

In view of this point, an object of the present invention is to provide an X-ray detector structure and a manufacturing method thereof that make it possible to eliminate dark current flowing from an anode electrode to a cathode electrode.

Hereinafter, a detector according to the present invention will be explained with reference to the drawings.

FIG. 2 shows an example of the present invention in which the configuration of the electrode portion of the ionization chamber type detector having the structure shown in FIG. 1 is shown along with a fixing method.

The material used for the electrode holding plate 1 is thermoplastic resin.

For example, the material may be polytetrafluoroethylene resin, vinylidene fluoride resin, 37-fluorinated chlorinated ethylene resin, 47-fluorinated ethylene-6-fluorinated propylene copolymer resin, or the like.

All of these materials have excellent electrical insulation properties, and have a volume resistivity of 1017 to 1011018.
Since 0h can be obtained, when used as an electrode holding plate of this type of device, it is effective for electrically insulating between the electrodes 2 and 3 as shown in FIG. 2B.

As shown in FIG. 2A, grooves are formed on the electrode holding plate 1 at predetermined intervals. Although this groove may be formed using a cutter, the above-mentioned resin material has good flowability when melted. Due to its unique characteristics, it can be easily produced by molding with a mold.

Electrode holding plates 1, which have been grooved to predetermined dimensions, are placed facing each other, and electrodes 2 and 3 are inserted alternately into the grooves, and then heated to a predetermined temperature (near the softening temperature of the resin) in a heating furnace. When heated, the contact area between electrodes 2 and 3 and electrode holding plate 1■
will be firmly fused.

In the X-ray detector shown in FIG. 2, the gap between the electrodes 2 and 3 is relatively large, and it is possible to eliminate dark current by increasing the creepage distance of the electrode holding plate that supports the electrodes 2 and 3. In order to increase the density of the detector, it is necessary to reduce the gap between each electrode.

In such a case, it is impossible to increase the creepage distance of the electrode holding plate, so the dark current flowing from the anode electrode 2 to the cathode electrode 3 along the electrode holding plate increases and the detector becomes unstable. It may stop working.

In such a case, as shown in Figure 3A, only one part of the electrode (only the part where the electrode is inserted into the groove) is coated with a release material 4 made of 47 fluoride resin on one side of each electrode. When heat treatment is performed after the coated material is inserted into the electrode holding plate 1, as shown in FIG. Because of the direct contact, it is possible to adhere to the electrode holding plate 1, but the surface coated with release material 4 is not adhered to the electrode holding plate 1, and if you look closely at the bonded area, you will notice that it has peeled off. On the side where material 4 is applied, d(
d=10 to 20 μm).

The reason for this is that the thermoplastic resin used for the electrode holding plate shrinks slightly due to heat treatment, but if such shrinkage occurs uniformly, This does not affect electrode assembly accuracy in any way.

As mentioned above, creating a gap on one side of the electrode helps to increase the creepage distance between the anode electrode 2 and the cathode electrode 3, and as a result, dark current flowing from the anode electrode 2 to the cathode electrode 3 can be completely eliminated. This makes it possible to realize an electrically stable detector.

As described above, according to the present invention, even if the electrode spacing is reduced, output signals can be stably detected, so that it is possible to realize a higher density of electrodes in an X-ray detector.

[Brief explanation of drawings]

Figures 1A and B are diagrams for explaining the configuration of a conventional X-ray detector, Figures 2A and B are diagrams showing the configuration of main parts of an embodiment of the present invention, and Figure 3A is a diagram for explaining the configuration of a conventional X-ray detector. and B are diagrams showing the configuration of main parts of another embodiment of the present invention.

Claims (1)

[Claims] 1. In an ionization chamber X-ray detector in which a plurality of planar anode electrodes and a plurality of planar cathode electrodes are arranged substantially in parallel in a predetermined gas medium, an electrode that supports the electrodes. The holding plate is made of a thermoplastic resin, and the thermoplastic resin is provided with a plurality of grooves at predetermined intervals, the electrode is inserted into the groove, and one side of the electrode is adhered to a side of the groove. An ionization chamber type X-ray detector characterized in that the other side has a resin that is removable from the resin. 2. A step of forming grooves at a predetermined interval in a predetermined thermoplastic resin, a step of inserting an electrode plate and a release material that releases the thermoplastic resin on the side surface of the electrode plate into the groove; a heat treatment step at a predetermined temperature in which the other side of the electrode plate is welded to one side, and there is a uniform gap between the peeling cut adhered to the electrode plate and the other side of the groove. A method for manufacturing an ionization chamber type X-ray detector characterized by its structure.