JPS588753B2 - Ionization chamber type X-ray detector - Google Patents

Description

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

Conventionally, an ionization chamber type detector that measures the spatial distribution of X-ray photons has been used as a detector in a computerized X-ray tomography apparatus.

The general structure of this detector is as shown in FIG. 1, in which a plurality of planar anode electrodes 5 and planar cathode electrodes 6 are alternately arranged at approximately parallel intervals on an electrode holding plate (for example, an insulator) 1. These are provided in a case, and the inside thereof is sealed in a high atomic weight gas (for example, xenon gas) at a pressure in the range of about 10 atm to about 50 atm.

X-ray photons (X-rays are incident from the direction of the arrow in the figure) interact with this gas to produce photoelectron-ion pairs.

Electrons generated in the presence of an electric field are collected on the anode electrode 5, and ions are collected on the cathode electrode 6, resulting in a current in these electrodes that is proportional to the X-ray intensity in the vicinity of the electrode.

However, conventional ionization chamber type X-ray detectors have the disadvantage that dark current is generated due to creeping discharge along the insulator surface from the anode electrode to the cathode electrode, making it impossible to accurately detect the signal current.

In view of this, an object of the present invention is to provide an ionization chamber type X-ray detector that can eliminate the dark current and thereby accurately and stably detect a signal current.

In order to achieve this object, the present invention is characterized in that dark current is grounded at the electrode holding plate.

The present invention will be explained below with reference to the drawings.

FIGS. 2A to 2C are diagrams for explaining the structure of the electrode support plate according to the present invention together with its processing method.

As shown in Figure 2a, the electrode holding plate 1 consists of an insulator 2 and a metal 3.
The contact surfaces of the two are welded, silver soldered, or firmly adhered using the adhesive 4.

Next, using a cutting machine, the insulator 2 is cut into metal 3 as shown in Figure 2b.
Cut to a depth that reaches the part.

The groove created by this cutting is indicated by 7.

After this machining is completed, as shown in FIG. 2C, grooves for electrode insertion are made to a predetermined depth from the surface of the insulator 2.

This groove is indicated by 8 in the figure.

Therefore, in the electrode holding plate 1 which has undergone the above-mentioned grooving process, the insulators 2 are periodically arranged on the metal plate while maintaining the finely divided metal exposed parts.

As shown in FIG.
and cathode electrodes 6 are inserted alternately, and each electrode 5, 6 and insulator 2 are fixed to complete the detector.

Note that in FIG. 3, the groove 7 is omitted.

Therefore, if you use a multi-wire saw as a cutting machine,
Since the pitch interval of the grooves and the depth of the grooves can be highly controlled, the distance between each electrode can be accurately maintained and fixed.

Since the detector according to the present invention is used with the electrode holding plate 1 completely grounded during operation, the dark current that attempts to flow along the insulator surface from the anode electrode to the cathode electrode is exposed between the two electrodes. Since the metal part of the electrode is grounded, dark current from the anode electrode never flows into the cathode electrode, and the signal current can be detected stably.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a schematic configuration of the main parts of a conventional ionization chamber type X-ray detector, FIG. 2 is a diagram showing the configuration of an electrode holding plate according to the present invention, and FIG. FIG. 2 is a diagram showing a schematic configuration of an ionization chamber type X-ray detector used.

Claims (1)

[Claims] 1 An X-ray detector consisting of a plurality of electrodes arranged in parallel to each other in grooves of an electrode holding plate in a case, the electrode holding plate consisting of two layers of an insulator and a metal plate, and a groove for inserting the electrodes. An ionization chamber type X-ray detector, characterized in that one groove is provided in the insulator, and a second groove is provided between the grooves with a depth that reaches the metal plate.