JPH08201525A - Semiconductor radiation detector and its measuring apparatus - Google Patents

Abstract

PURPOSE: To cut off an external noise with good efficiency by a method wherein a conductive metal sheet or a vapor-deposited sheet is formed on a mounting board for a detection element so as to be electrically insulated from the element. CONSTITUTION: A semiconductor radiation detection element 1 is mounted on a mounting board 2, and the board 2 is fixed to a detector case 3 by means of jigs 4. A radiation detection signal from the element 1 is taken out as a detection signal 6 via an electrode 5 for the element 1 in an insulated state from the case 3. Grounded conductive metal sheets (vapor-deposited films) 8 are formed on the excess surface and the rear surface of the board 2 on which the element 1 is mounted, and the element is attached to the case 3 via the jigs 4. Thereby, parts other than an incident window 7 are surrounded by the case 3, and external radio waves can be cut off completely. Since the grounded metal sheets 8 are formed on the same plane as the element 1, the external radio waves are drawn close to the metal sheets 8, and their incidence on the element 1 is relaxed.

Description

Detailed Description of the Invention

[0001]

The present invention relates to low energy X-rays, α, β
The present invention relates to a radiation detector for measuring radiation having a small penetrating power such as a line and a measuring device therefor.

[0002]

2. Description of the Related Art In order to measure radiation having small penetrating power with high sensitivity, it is desirable to reduce the radiation absorbing layer between the detector and the radiation source as much as possible. For this reason, in the conventional detector, the radiation entrance window is generally removed or the structure is made as thin as possible.

[0003]

With the conventional detector structure, the effect of shielding external radio waves is small, and noise cannot be completely blocked. This is the S / N of radiation measurement
Has a drawback that the sensitivity cannot be expected to be high. In addition, in order to completely block external noise, a large amount of equipment is required, such as performing measurements in a shielded room.

It is an object of the present invention to maintain a conventional detector structure in which the radiation absorption layer between the detector and the radiation source is reduced as much as possible, and at the same time, a semiconductor radiation detector capable of efficiently blocking external noise even in the measurement outside the shield room, It is to provide the measuring device.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a grounded conductive metal plate such as a copper plate on a front surface (a portion where the detection element is not mounted) or a rear surface of a substrate on which a semiconductor radiation detection element is mounted (evaporation). This can be achieved by providing a film) and changing the electric field distribution around the detection element.

[0006]

In order to block external noise, it is best to surround the entire semiconductor detection element with a shield material. However, in order to detect radiation with low penetrating power like this detector, it is necessary to remove the radiation entrance window or make it as thin as possible. The side surface and the back surface of the detection element can be surrounded by a detector case, but the radiation incident surface is in a state almost open. If a grounded conductive metal plate is provided on the same plane as the detection element, external radio waves entering the detection element are attracted to the grounded metal plate, and the electric field distribution changes. This allows
Effective noise shielding becomes possible.

[0007]

EXAMPLES The detailed description of the present invention will be given below with reference to examples. FIG. 1 shows an embodiment of the radiation detector of the present invention. The semiconductor radiation detection element 1 is provided on the mounting substrate 2,
The substrate 2 is fixed to the detector case 3 with the jig 4. The radiation detection signal from the detection element 1 passes through the electrode 5 of the detection element,
It is taken out as an external detection signal 6 while being insulated from the detector case 3. To detect radiation with low penetrating power, set the entrance window 7 to 1.
It must be made a thin film of about μm or deleted. A grounded conductive metal plate (evaporated film) 8 is provided on an extra surface (a part where the detection element is not mounted) or the back surface of the substrate 2 on which the radiation detection element 1 is mounted, and the detector case 3 is provided via the jig 4.
Ground to. Since the parts other than the entrance window 7 are surrounded by the detector case 3, external radio waves can be completely blocked. Since the radiation entrance window 7 is a thin film of about 1 μm, the effect of blocking external radio waves cannot be expected. That is, the entrance window is equivalent to the open state.
In the conventional detector structure, external radio waves directly enter the semiconductor detection element and become a large noise source. In the present invention, since the grounded metal plate is provided on the same plane as the detection element, external radio waves are attracted to the metal plate on the outer periphery of the detection element, and an effect of reducing the incidence of external radio waves on the detection element is produced.

FIG. 2 shows the construction of a radiation measuring apparatus using this detector. The radiation detection signal of the semiconductor detection element 1 is transmitted through the coupling capacitor 10 to the preamplifier 11, the linear amplifier 12, and the indicator 13 for displaying the calculation of the radioactivity concentration.
Sent to and display the measurement results.

FIG. 3 shows a comparison of the output signals of the detector using the conductive metal plate (deposition film) 8 of the present invention and the conventional detector. (A) is the noise level of the conventional detector,
(B) is the noise level of the detector of the present invention. (A)
Is several tens of mV and (b) is several mV, and it can be clearly seen that the noise reduction effect is 1/4 or less.

FIG. 4 shows the result of comparison of minute radiation detection signals. Similarly, (a) is the output signal of the conventional detector,
(B) is an output signal of the detector of the present invention. It is difficult to detect a minute detection signal with the conventional detector, and the detector of the present invention enables highly sensitive measurement of low penetrating power radiation.

Although this embodiment is an example in which conductive metal plates are provided on the front and back surfaces of the substrate on which the detection element is mounted, noise can be reduced by a structure provided on one of the front and back surfaces. Further, even when a conductive metal plate is provided but not grounded, the noise can be reduced.

FIG. 5 shows a modification of the present invention. This modification is an example using a circular detection element, and the detector case 3 and the electrode 5 are not shown. A grounded copper plate (deposited film) 8 is provided around the detection element 1 to reduce the incidence of external radio waves on the detection element. Since the conductive metal plate (deposited film) 8 having a uniform area is provided around the detection element 1, a uniform noise reduction effect is provided over the entire surface of the detection element.

According to the present embodiment, in a detector having a structure in which a radiation entrance window for detecting radiation having a low penetrating power is removed or a thin film entrance window is installed, external noise is effectively blocked and low penetration is achieved. It is possible to provide a measuring device that enables highly sensitive measurement of force radiation.

[0014]

According to the present invention, it is possible to provide a radiation measuring apparatus capable of highly sensitive measurement of low penetrating power radiation without using a shielded room which requires a large facility cost.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a radiation measuring apparatus of the present invention.

FIG. 3 is a waveform diagram showing a comparison between the radiation detector output of the present invention and the conventional detector output.

FIG. 4 is a waveform chart showing a result of comparing minute radiation detection signals of the radiation detector output of the present invention and the conventional detector output.

FIG. 5 is a sectional view showing a modified example of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor type radiation detection element, 2 ... Mounting board, 3 ... Detector case, 4 ... Jig, 5 ... Electrode, 6 ... Detection signal, 7 ... Incident window, 8 ... Conductive metal plate.

Front Page Continuation (72) Inventor Akihisa Umihara 5-2-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Omika Plant

Claims (3)

[Claims] 1. In a semiconductor radiation detector having an entrance window for radiation detection opened or a thin film provided, a mounting plate of the detection element is provided with a conductive metal plate or vapor deposition plate in a state of being electrically insulated from the detection element. A semiconductor type radiation detector characterized by being provided. 2. A semiconductor type radiation detector according to claim 1, wherein the conductive metal plate or vapor deposition plate is grounded. 3. A radioactivity measuring device comprising the semiconductor type radiation detector according to claim 1 or 2 provided with an amplifier and a radioactivity calculation display.