JP2604114Y2 - 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 radiation detector used in a medical radiation image receiving apparatus, a radiation inspection apparatus for a destructive inspection, and the like.

[0002]

2. Description of the Related Art Generally, 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 GaAs crystal, as shown in FIG. It is configured to apply a predetermined level of voltage in between. Then, by detecting a current or a pulse generated by the induced charge q generated by the incidence of the radiation γ, the incident amount of the radiation can be detected. Conventionally, in order to perform one-dimensional or two-dimensional imaging of a subject, as shown in FIG.
A large number of signal extraction electrodes 62n-1, 62n, 6
A configuration in which a large number of detection channels are arrayed by forming 2n + 1.

[0003]

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 by the incident radiation 65 is transmitted to the adjacent detection region 64n-1. By escaping, an induced charge q is generated in the adjacent detection region 64n-1. Therefore, there is a problem that a detection error of incident radiation due to the characteristic X-rays escaped from the adjacent detection region occurs to lower the spatial resolution. there were.

In order to solve these problems, the present invention prevents characteristic X-rays from escaping to an adjacent detection region with a simple configuration, and enables more accurate measurement of the concentration distribution of incident radiation. It is an object to provide a radiation detector.

[0005]

In order to solve the above problems, a radiation detector according to the present invention detects electrodes by forming electrodes on both surfaces of a compound semiconductor substrate and applying a predetermined voltage between both electrodes. In the radiation detector, a plurality of signal extraction electrodes and dummy electrodes having a width of about the mean free path of characteristic X-rays are alternately formed on the surface of the compound semiconductor substrate opposite to the radiation incident side. And

[0006]

The operation of the present invention will be described with reference to FIG. When the radiation 5 enters the compound semiconductor substrate 4, the detection region 4n
Generates an induced charge q and a characteristic X-ray 6,
The generated characteristic X-ray 6 travels to the adjacent detection area 4n-1. At this time, the dummy electrodes... 3n-1, 3n.
Since the characteristic X-ray 6 is formed with a width about the mean free path of the line, the characteristic X-ray 6 generates the 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 the dummy electrode 3n-1, so that there is almost no detection error due to the characteristic X-rays 6 generated in the adjacent detection areas 4n and the like, and accurate measurement of the concentration distribution of incident radiation becomes possible.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows an example in which the present invention is applied to a one-dimensional array of radiation detectors. FIG. 1A is a front view thereof, and FIG. 1B is a plan view seen from a signal extraction electrode side. . In the figure, reference numeral 1 denotes a bias electrode which is formed on the radiation incident surface side of the compound semiconductor substrate 4 so as to cover the entire surface. Reference numeral 2 denotes a signal extraction electrode, which is formed in a large number on a surface facing the bias electrode 1, and detects an induced charge generated by the incident radiation 5 at each electrode. 3
Are dummy electrodes formed by alternately arranging the large number of signal extraction electrodes 2, each having a width of about the mean free path of characteristic X-rays, and having characteristics generated in the compound semiconductor substrate 4. Absorbs induced charge generated by 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. , And is maintained at a predetermined potential so that the generated induced charge 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 signal extraction electrodes 2n-1, 2n,
2n + 1 ··· Radiation detection area according to position ··· 4n-1,
4n, 4n + 1... And dummy electrodes 3n-1, 3n, 3n + 1
..Interference area according to the position of 4'n-1, 4'n, 4'n +
It is divided into 1 ... The radiation 5 incident on the compound semiconductor substrate 4 generates, for example, an induced charge q in the detection region 4n and also generates a 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 about the mean free path of the characteristic X-ray,
The characteristic X-ray 6 generated in the detection area 4n generates the induced charge q 'in the interference area 4'n-1 without reaching the adjacent detection area 4n-1. The induced charge generated is the dummy electrode 3n-
1 and is absorbed by the
Generation of induced charges due to characteristic X-rays generated at n or the like can be prevented, and accurate measurement of the concentration distribution of incident radiation with almost no detection error becomes possible.

Here, when a CdTe crystal is used for the compound semiconductor substrate 4, characteristic X-rays of about 30 keV and about 10 keV are generated when X-rays of about 30 keV or more are incident when a GaAs crystal is used. And
The mean free path is about 80 μm for CdTe and about 50 μm for GaAs. Accordingly, the electrode width of the dummy electrode 3 has a characteristic X determined by the material used for the compound semiconductor substrate 4 and the like.
What is necessary is just to determine suitably based on the mean free path of a line.

As described above, the bias electrode 1 is provided on the incident side of the incident radiation 5 and the signal extraction electrode 2 is provided on the opposite side thereof.
By providing the dummy electrode 3, the electric field from the signal extraction electrode 2 toward the bias electrode 1 becomes as indicated by an arrow 7. At this time, since most of the induced charges are generated in the vicinity of the bias electrode 1 on the incident side of the incident radiation 5, the detection area is smaller than when the signal extracting 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, which is the incident side of the incident radiation 5.

FIG. 3 is a schematic diagram showing a case where 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 a bump, an adhesive, or the like, and 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 to be counter-arrayed. It is counted at 7c. At this time, each dummy electrode 3
Is 0 potential via the dummy potential supply electrode 6 or
It is fixed to the same potential as the input gate of the amplifier array 7a, or to another appropriate potential.

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

[0014]

According to the present invention, a configuration is adopted in which dummy electrodes having a width of about the mean free path of characteristic X-rays are alternately formed between a large number of signal extraction electrodes formed on one surface of a compound semiconductor substrate. As a result, the characteristic X generated at the adjacent electrode portion
The escape of the line can be prevented, and the induced charge generated by the escaped characteristic X-ray can be absorbed by the dummy electrode. For this reason, the detection error of the incident radiation in the characteristic X-ray can be significantly reduced, and the concentration distribution of the incident radiation can be measured with a simpler configuration and with high accuracy.

[Brief description of the drawings]

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

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

FIG. 3 is a schematic view showing a case where 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]

 REFERENCE SIGNS LIST 1 bias electrode 2 signal extraction electrode 3 dummy electrode 4 compound semiconductor substrate 5 incident radiation

Claims (1)

(57) [Scope of request for utility model registration] An electrode is formed on both surfaces of a compound semiconductor substrate,
In a radiation detector that detects incident radiation by applying a predetermined voltage between both electrodes, a width of about an average free path of a signal extraction electrode and a characteristic X-ray is formed on a surface of the compound semiconductor substrate opposite to a radiation incident side. A radiation detector, wherein a plurality of dummy electrodes are alternately formed.