JPS62124485A - Semiconductor radiation detector - Google Patents

Abstract

PURPOSE:To improve the sensitivity by removing a noise current of low frequency characteristic to a semiconductor detector by a one-shot circuit and outputting only signal currents inputted from a couple of one-shot circuits at the same time by a simultaneous counting circuit. CONSTITUTION:Signal pulse is and a noise current in are amplified by amplifiers 7 and 7' and outputted to one-shot circuits 10 and 10'. The one-shot circuits 10 and 10' operates only with a fast-rising signal (high frequency signal) and does not respond to the noise signal of low frequency, so the one-shot circuits 10 and 10' output the signal pulses Is and a noise N induced on a signal line, so that the noise signal in is removed. Then, the simultaneous counting circuit 11 judges the outputs of the one-shot circuits 10 and 10' to output only the signal pulses Is which are inputted at the same time to a counting circuit 9 and remove the induced noise N because it is not inputted at the same time. Thus, noises characteristics to the semiconductor detector can be removed, so even low-energy radiation is detected.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to semiconductor radiation detectors.

[Technical background of the invention and its problems]

A pn junction type semiconductor radiation detector using a silicon or germanium plate is known as a semiconductor radiation detector. For example, as shown in Figure 4, the n-layer (3) and 2
When a voltage (2) that provides a reverse bias to the pn junction is applied between the layer (5) and the pn junction via the electrodes (1) and (2), the depletion layer (4) expands. This depletion layer (4) is exposed to radiation (
6), electron-hole pairs are generated, and the applied voltage carries the holes to the electrode (2) and the electrons to the electrode (1), causing a pulse current to flow.

This pulse current is amplified by a preamplifier (7), the wave height is discriminated by a disc amplifier (8), and the radiation level is measured by a counting circuit (9).

When detecting radiation with a low counting rate using such a semiconductor radiation detector, it was necessary to increase the surface area to increase counting efficiency, but as the surface area increases, the surface leakage current of the pn junction increases. This method had the disadvantage that low-energy radiation could not be detected due to increased noise.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor radiation detector capable of detecting even low-energy radiation without being affected by noise inherent in the detector.

[Summary of the invention]

The present invention provides a semiconductor radiation detector in which p of a bovine and horse body plate is
'A plurality of electrodes are provided on the surface of one of the n layers, for example, the n layer, and one electrode is provided on the other, for example, the 2nd layer, and a reverse bias voltage is applied between the 2nd layer and the n layer via each electrode. is applied, and the plurality of electrodes are divided into two groups, each group is connected to a one-shot circuit via a preamplifier, and the output of this pair of one-shot circuits is connected to a counting circuit via a coincidence counting circuit. By configuring this to The induced noise induced in the signal line is cut by not being input at the same time, making it possible to detect even low-energy radiation.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

A semiconductor radiation detector according to the present invention is shown in FIG. pn
A plurality of electrodes (a,) are formed on the surface of one of the p'n layers of the silicon plate, for example the n layer (3), on which the junction is formed.

(a2)...(an) are provided at intervals shorter than the average range of the incident radiation. Moreover, one electrode (2) is provided on the surface of the other two layers (5) of the p'n layers. A reverse bias voltage (■) is applied between each electrode (a,), (a2), . . . (an) and electrode (2). and,
Two groups of multiple electrodes (a□), (a,)...(an),
For example, divide the electrodes into two groups, odd-numbered and even-numbered, connect the even-numbered electrodes together to the one-shot circuit (10) via the preamplifier (7), and connect the odd-numbered electrodes together to the preamplifier (10). 7') through the one-shot circuit (1
0'). In addition, a pair of one-shot circuits (
10), (1o') output to coincidence circuit (11)
Connect to the counting circuit (9) via.

The operation of the semiconductor radiation detector according to one embodiment of the present invention configured as described above will be explained. Generally, when a semiconductor radiation detector is used with a reverse bias voltage applied, the noise current is l
It is expressed as n=&go.

Here, e: electron charge, ■: leakage current, and B: noise bandwidth.

By making the distance between the electrodes (a□), (a,)...(an) shorter than the average range of the radiation incident on the depletion layer (4), the electrons generated by the radiation (6) are equally input to preamplifiers (7) and (7') as signal pulses. This signal current has high frequency components (~1o8H
On the other hand, the noise current in has a low frequency component (~102 Hz), and this state is shown in FIGS. 2(a) and 2(b). In the figure, is represents a signal pulse, and in represents a noise current.

This signal pulse 18 and noise current in are preamplified (
7) and (7'), and one-shot circuit (1o
) and (10'). To one-shot circuit 1 Since circuits (1o) and (10') operate only with fast-rising signals (high-frequency signals) and do not respond to low-frequency noise current, the output of one-shot circuits (10) and (10') is the signal pulse I as shown in Fig. 2(c) and (d).
s and the induced noise N induced in the signal line, and the noise current i, , is removed. Then, the coincidence circuit (11
) judges the output of the one-shot circuits (10) and (10') and outputs only the signal pulses S that are input at the same time to the counting circuit (9), and the induced noise N is removed by not inputting them at the same time. . This situation is shown in FIG. 2(e). The radiation level is measured by the counting circuit (9) to which only the signal pulse S is sent from the coincidence counting circuit (11).

As described above, the semiconductor radiation detector according to the embodiment of the present invention can remove noise inherent in semiconductor detectors, and therefore can detect even low-energy radiation. In addition, the noise current j, which depends on the surface leakage current of the pn junction,
, can be removed, the surface area of the semiconductor detector can be increased, and a highly sensitive detector can be realized.

The arrangement of the plurality of electrodes on the surface of the semiconductor n-layer (3) is shown in FIGS. 3(a), (b), and (c), for example.
) and (d) are possible. In each figure, the filled electrode (E) and the dotted electrode (E') indicate the grouping of a plurality of electrodes. Further, each time indicates a pattern, and the number of electrodes is an example and is not defined as shown.

〔Effect of the invention〕

As described in detail above, according to the present invention, in a semiconductor radiation detector, one of the p'n layers of the semiconductor plate, for example, n
A plurality of electrodes are provided on the surface of the layer, and the other one, e.g.
One electrode is provided in each layer, and a reverse bias voltage is applied between the second layer and the n layer through each electrode, and the plurality of electrodes are divided into two groups, and each group is connected together through a preamplifier. By connecting the pair of one-shot circuits to a one-shot circuit and connecting the outputs of this pair of one-shot circuits to a counting circuit via a coincidence circuit, the one-shot circuit can eliminate the low-frequency noise current inherent in semiconductor detectors. The coincidence counting circuit outputs only the signal currents input simultaneously from a pair of one-shot circuits to the counting circuit, and the induced noise induced in each signal line can be cut by not inputting them simultaneously. Even low-energy radiation can be detected without any effects. Further, since the noise current depending on the surface leakage current of the pn junction can be removed, the surface area of the semiconductor detector can be increased, and a highly sensitive detector can be realized.

[Brief explanation of drawings]

FIG. 1 is a block connection diagram showing an embodiment of a semiconductor radiation detector according to the present invention, and FIGS. 2(a) and (b). (c), (d), and (e) are respectively explanatory diagrams of the operation of the detector in Fig. 1, and Fig. 2 (a) and (b) are the inputs of the preamplifier, and Fig. 2 (c) and (d) is the output of the one-shot circuit, Figure 2 (,) is a waveform diagram showing the output of the coincidence circuit, Figure 3 (a), (b), (C),
(d) is a diagram showing different patterns of arrangement of a plurality of electrodes on the n-layer surface, and FIG. 4 is a block connection diagram showing the configuration of a conventional semiconductor radiation detector.

Claims (1)

[Claims] A semiconductor in which a pn junction is formed in a semiconductor plate and electron-hole pairs generated by the incidence of radiation into a depletion layer caused by a reverse bias voltage applied through electrodes provided on both sides of the semiconductor are extracted as a current by the electrodes. In the radiation detector, a plurality of electrodes are provided on the surface of one of the p/n layers of the semiconductor board at intervals shorter than the average range of the incident radiation, and one electrode is provided on the surface of the other layer of the semiconductor board. A reverse bias voltage is applied between the p layer and the n layer through each electrode, and the plurality of electrodes are
A semiconductor radiation detector characterized in that each group is divided into groups and connected to a one-shot circuit via a preamplifier, and the outputs of the pair of one-shot circuits are connected to a counting circuit via a coincidence circuit.