JPH0732968U - Radiation detector - Google Patents

Abstract

(57) [Summary] [Object] To provide a radiation detector capable of preventing a characteristic X-ray from escaping to an adjacent detection region with a simple structure and measuring the concentration distribution of incident radiation with higher accuracy. [Structure] When the radiation 5 is incident on the compound semiconductor substrate 4, an induced charge q is generated in the detection region 4n and the characteristic X
The line 6 is generated, and the generated characteristic X-ray 6 is directed to the adjacent detection region 4n-1. At this time, dummy electrodes ... 3n-1, 3
Since n ··· is formed with a width of about the mean free path of the characteristic X-ray, the characteristic X-ray 6 is adjacent to the detection region 4n-1.
The induced electric charge q'is generated in the interference region 4'n-1 without reaching to. Since the generated induced charges are attracted to the dummy electrode 3n-1, there is almost no detection error due to the characteristic X-ray 6 generated in the adjacent detection region 4n or the like, and the concentration distribution of incident radiation can be accurately measured.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a radiation detector used for a radiation image receiving device for medical use, a radiation inspection device for destructive inspection, and the like.

[0002]

[Prior art]

 Generally, as shown in FIG. 5, a radiation detector is provided with electrodes 52 and 53 on both sides of a compound semiconductor substrate 51 such as a CdTe crystal or a Ga As crystal, and a predetermined distance between the electrodes 52 and 53. It is configured to apply a level voltage. Then, the amount of incident radiation can be detected by detecting a current or a pulse generated by the induced electric charge q generated by the incidence of the radiation γ. Conventionally, in order to perform one-dimensional or two-dimensional imaging of an object, a large number of signal extraction electrodes ... 62n-1, 62n, 62n + are formed on one surface of the compound semiconductor substrate 64 as shown in FIG. By forming 1 ..., a large number of detection channels are arrayed.

[0003]

[Problems to be solved by the device]

 However, in such a configuration in which a large number of detection channels are arrayed, for example, the characteristic X-ray 66 generated in the detection region 64n due to the incident radiation 65 is escaped to the adjacent detection region 64n-1 so as to be adjacent to this. Since the induced conductive charge q is generated in the detection region 64n-1, there is a problem that the detection error of the incident radiation due to the characteristic X-ray escaped from the adjacent detection region occurs and the spatial resolution is lowered.

Therefore, in order to solve these problems, the present invention prevents the characteristic X-rays from escaping to the adjacent detection area with a simple structure, and enables more accurate measurement of the concentration distribution of incident radiation. An object is to provide a radiation detector.

[0005]

In a radiation detector for detecting incident radiation by forming electrodes on both surfaces of a compound semiconductor substrate and applying a predetermined voltage between the electrodes, one surface of the compound semiconductor substrate is provided. It is characterized in that a plurality of signal extraction electrodes and a plurality of dummy electrodes having a width of the mean free path of characteristic X-rays are alternately formed.

[0006]

[Action]

 The operation of the present invention will be described with reference to FIG. When the radiation 5 is incident on the compound semiconductor substrate 4, the induced charges q are generated in the detection region 4n and the characteristic X-ray 6 is generated, and the generated characteristic X-ray 6 is directed to the adjacent detection region 4n-1. At this time, since the dummy electrodes ... 3n-1, 3n ... Are formed with a width of about the mean free path of the characteristic X-rays, the characteristic X-rays 6 reach the adjacent detection area 4n-1. However, the induced charge q'is generated in the interference region 4'n-1. Since the generated induced charges are attracted to the dummy electrode 3n-1, there is almost no detection error due to the characteristic X-ray 6 generated in the adjacent detection region 4n or the like, and the concentration distribution of incident radiation can be accurately measured.

[0007]

【Example】

 An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is an example showing a case where the present invention is applied to a one-dimensional array type radiation detector. FIG. 1a is a front view thereof, and FIG. 1b is a plan view seen from the signal extraction electrode side. . In the figure, reference numeral 1 denotes a bias electrode formed on the radiation incident surface side of the compound semiconductor substrate 4 so as to cover the entire surface thereof. Reference numeral 2 denotes a signal extraction electrode, which is formed in a large number on the surface facing the bias electrode 1, and detects the induced charge generated by the incident radiation 5 at each electrode. 3 is a dummy electrode formed by alternately arranging with the signal extraction electrodes 2 formed in large numbers, each having a width of about the mean free path of the characteristic X-ray, and generated in the compound semiconductor substrate 4. Absorbs the induced conductive load generated by characteristic X-rays. A predetermined voltage is applied between the bias electrode 1 and the signal extraction electrode 2 so that the bias electrode 1 serves as a cathode, and the dummy electrode 3 is connected to a common dummy potential supply electrode 6. , It is held at a predetermined potential so that the generated induced charges can be effectively absorbed.

FIG. 2 is a detailed view of FIG. 1a showing a front view of a one-dimensional array of radiation detectors. In the figure, the compound semiconductor substrate 4 has a radiation detection region corresponding to the positions of the signal extraction electrodes, 2n-1, 2n, 2n + 1, ..., 4n-1, 4n, 4n + 1 ,. .. 3n-1, 3n, 3n + 1 .. are divided into interference regions according to the positions of the electrodes ... 4'n-1, 4'n, 4'n + 1. Then, the radiation 5 incident on the compound semiconductor substrate 4 causes, for example, the induced charges q in the detection region 4n to generate the characteristic X-ray 6, and the generated characteristic X-ray 6 travels to the adjacent detection region 4n-1. At this time, since the dummy electrodes 3n-1, 3n, 3n + 1 ... Are formed with a width of about the mean free path of the characteristic X-rays, the characteristic X-rays 6 generated in the detection region 4n Generates induced charge q'in the interference region 4'n-1 without reaching the adjacent detection region 4n-1. The generated induced charges are attracted to and absorbed by the dummy electrode 3n-1. Therefore, it is possible to prevent the generation of induced charges due to the characteristic X-rays generated in the adjacent detection region 4n, etc. Can be measured.

Characteristic X-rays of about 30 keV and about 10 keV are generated when an X-ray of about 30 keV is used when the CdTe crystal is used for the compound semiconductor substrate 4 and about 10 keV or more is used when the GaAs crystal is used, respectively. The mean free path is about 80 μm for CdTe and about 50 μm for GaAs. Therefore, the electrode width of the dummy electrode 3 may be appropriately determined based on the mean free path of the characteristic X-ray that is determined according to the material used for the compound semiconductor substrate 4.

As described above, by providing the bias electrode 1 on the incident side of the incident radiation 5 and the signal extraction electrode 2 and the dummy electrode 3 on the opposite side, the signal extraction electrode 2 is directed to the bias electrode 1. The electric field is as shown by arrow 7. At this time, most of the induced charges are generated in the vicinity of the bias electrode 1 on the incident side of the incident radiation 5, so that the detection area is larger than when the signal extraction electrode 2 and the dummy electrode 3 are provided on the incident side of the incident radiation 5. 4n and the interference region 3n-1 It is possible to more reliably detect the induced charges generated in the vicinity of the bias electrode 1 on the incident side of the incident radiation 5.

FIG. 3 is a schematic diagram when the one-dimensional array radiation detector shown in FIGS. 1 and 2 is actually used. The radiation detector is connected to the wiring board 7 by using bumps or adhesives, and the detection signals obtained from the plurality of signal extraction electrodes 2 are amplified by the amplifier array 7a and pulsed by the comparator array 7b and countered. It is counted in array 7c. At this time, each dummy electrode 3 is fixed to 0 potential, the same potential as the input gate of the amplifier array 7a, or another appropriate potential via the dummy potential supply electrode 6.

FIG. 4 is a plan view seen from the direction of the signal extraction electrode 42, which is a modified embodiment showing an example in which the present invention is applied to a two-dimensional array type radiation detector. As shown in the figure, substantially square signal extraction electrodes 42 are two-dimensionally formed at predetermined intervals on a planar compound semiconductor substrate 44, and the dummy electrode 43 uses the dummy potential supply electrode 46 as a common electrode for signal generation. It is formed in a lattice shape so as to surround the extraction electrode 42. As a result, the characteristic X-rays generated in the detection region of the compound semiconductor substrate 4 corresponding to each of the signal extraction electrodes 42 are generated in the same manner as in the case of the radiation detector formed in the one-dimensional array described above. Induced charges are generated in the interference region corresponding to the electrodes 3, and the generated induced charges are absorbed by the respective dummy electrodes 3.

[0014]

[Effect of device]

 According to the present invention, since the dummy electrodes having a width of about the mean free path of the characteristic X-rays are alternately formed between the plurality of signal extraction electrodes formed on one surface of the compound semiconductor substrate, adjacent electrodes are formed. The escape of the characteristic X-ray generated in the part can be prevented, and the induced charge generated by the escaped characteristic X-ray can be absorbed by the dummy electrode. Therefore, the detection error of the incident radiation on the characteristic X-ray can be greatly reduced, and the concentration distribution of the incident radiation can be measured with high accuracy by a simpler configuration.

[Brief description of drawings]

FIG. 1 is a diagram showing a case where the present invention is applied to a one-dimensional array radiation detector.

FIG. 2 is a view showing the operation of the present invention.

FIG. 3 is a view showing a schematic diagram when the present invention is actually used.

FIG. 4 is a view showing a modified embodiment of the present invention.

FIG. 5 is a diagram showing a conventional radiation detector.

FIG. 6 is a diagram showing a conventional radiation detector.

[Explanation of symbols]

 1 ... Bias electrode 2 ... Signal extraction electrode 3 ... Dummy electrode 4 ... Compound semiconductor substrate 5 ... Incident radiation

Claims (1)

[Scope of utility model registration request] 1. A radiation detector for detecting incident radiation by forming electrodes on both surfaces of a compound semiconductor substrate and applying a predetermined voltage between both electrodes, wherein a signal extraction electrode is provided on one surface of the compound semiconductor substrate. A radiation detector characterized in that a plurality of dummy electrodes having a width of the mean free path of characteristic X-rays are alternately formed.