JPH065291B2 - Radiation detector - Google Patents

Description

The present invention relates to a semiconductor radiation detector, and more particularly to α-rays and β-rays.
Ray, γ ray, in a radiation atmosphere in which two or more of neutron rays coexist, a semiconductor radiation detector suitable for identifying each radiation quality and quantitatively measuring the dose rate for each radiation quality . [Prior Art] A conventional semiconductor radiation detector is disclosed in JP-A-59-10836.
As described in No. 7, one type of radiation quality (mainly γ-rays) is targeted and the aim is to increase the sensitivity or expand the range of dose rate linearity. In this known example, the voltage applied to the semiconductor detection element is varied to control the thickness of the depletion layer generated in the detection element or its spread. The depletion layer is a radiation sensitive region, and the sensitivity of the detection element can be directly controlled. However, no consideration was given to the identification of radiation quality. Further, in the known example of Japanese Patent Laid-Open No. 56-148873, in order to identify the radiation quality, the applied voltage of one semiconductor detection element is changed and the depletion layer thickness is set to the target radiation range (transmission distance). To do. Alternatively, the radiation quality of each radiation is identified from the output value under the condition that the filters corresponding to the target radiation transmission power are individually attached to and detached from the detection element. However, no consideration has been given to the quantitative measurement of the dose rate for each radiation when the radiation of different radiation is mixed. [Problems to be Solved by the Invention] As described above, the prior art does not consider the quantification of the dose rate for each radiation quality, and is applied to a radiation monitor in which dose rate measurement for each radiation quality is essential. Had a problem. An object of the present invention is to provide a semiconductor radiation detector capable of simultaneously detecting the dose rate of each radiation for each radiation quality. [Means for Solving the Problems] A plurality of semiconductor radiation detecting elements for collecting and detecting electron-hole pairs generated by radiation at the electrodes are arranged in parallel in the depletion layer of the semiconductor sandwiched between the electrodes. The electrodes of these sensing elements are
Among the rays, the β rays, and the α rays, the γ rays only, the γ rays and the β rays only, and the above three elements are transmitted in the order of strong penetrating power. Furthermore, α reacts with neutron rays on the back side of the electrode that transmits neutron rays and γ rays or γ rays and β rays, and α
A detection element having a structure in which a material for generating particles is provided and electron-hole pairs generated by the γ-rays or the γ-rays and β-rays transmitted through the α-particles and the electrodes are collected and detected by the electrodes is also provided. The output of these detection elements is subtracted by multiplying it by a correction coefficient to calculate outputs corresponding to the dose rates of the respective radiation qualities by a logical operation circuit, and a display is provided to display these outputs respectively. It is also possible to adopt a configuration in which some of at least two of the radioactive substances are measured by not providing all of the above-mentioned detection elements but providing some of them. [Function] The output of the detection element that transmits only γ-rays shows the dose rate of only γ-rays, and by multiplying this by a correction coefficient, subtract it from the output of the detection element that transmits only γ-rays and β-rays. , Β-ray dose rate is calculated. By subtracting those obtained by multiplying the outputs corresponding to the respective dose rates of γ-rays and β-rays by the correction coefficient from the output of the detection element that transmits γ-rays, β-rays and α-rays, α
Line-only dose rates are calculated. Further, when the material of the α-particles that react with neutron rays and the electrode of the detection element provided on the back side of the electrode are those that transmit neutron rays and γ rays,
From the output of the detection element, the dose rate of neutron rays is obtained by subtracting the obtained dose rate of γ-rays multiplied by a correction coefficient, and the electrode is neutron rays, γ-rays and β
In the case of transmitting a ray, the dose rate of the neutron ray can be obtained by subtracting the obtained dose rates of the γ-ray and β-ray from the output of the detection element, each of which is multiplied by a correction coefficient. The dose rate thus obtained for each radiation quality is displayed on the display. [Embodiment] An embodiment of the present invention will be described with reference to FIG. Electrodes 2, 3, 4, 5) having different structures and respective output signal lines 6 are provided on the plate-shaped semiconductor material 1. A common applied voltage V _B is applied to the output signal line 6 via the resistor R. The back side of the semiconductor material 1 is provided with a common electrode 7 forming an ohmic contact. Each output signal line 6 is connected to a logical operation unit 10 via an amplifier 8 and an integrator 9. Furthermore, the radiation quality (α rays, β rays,
A display unit 11 for displaying the dose rate for each γ ray or neutron ray is provided. The above is the overall configuration of the semiconductor radiation detector according to the present embodiment. As the semiconductor material 1, high-purity silicon, cadmium telluride, or the like is used. When an applied voltage V _B is applied to this detector, a depletion layer 12 is formed in the semiconductor for each electrode.
Is generated. In the depletion layer 12, the charged particle radiation (α
Line, β ray) forms an electron-hole pair and is extracted as a current pulse signal from the electrodes on both sides of the semiconductor material 1. When γ-rays enter the depletion layer 12, secondary electrons generated by the interaction between the γ-rays and the semiconductor material (Compton scattering, etc.) form electron-hole pairs. When a neutron beam is incident, the neutron beam has no charge, and the depletion layer 12 remains as it is.
Do not generate electron-hole pairs inside. The thickness of the depletion layer 12 of each detection element in which the depletion layer is independently formed by the electrodes 2, 3, 4, and 5 of this detector is exactly the same because the applied voltage is common. If the structure of each electrode is the same, effective information for identifying the radiation quality of the radiation cannot be obtained from each detection element. It is provided with a thickness that can block the incidence of α-rays and β-rays, and only the γ-rays are detected from the detection element to which this electrode 2 belongs.
Since the penetrating power of rays is large, only the blocking of β rays should be considered. Generally, the energy E of β-rays is 5 MeV or less, so the thickness of the electrode 2 can be determined from the material of the electrode 2 and the range R of β-rays. When the electrode material is aluminum, the range R of β-rays is calculated from R = 407E ^1.38 (mg / cm ² ), and the thickness of the electrode 2 can be determined by R / ρ from the density ρ of aluminum. This value is about 1.4 mm. The detection element to which the electrode 2 thus designed belongs is an element for selectively detecting only γ rays. Next, the thickness of the electrode 3 is set so as to prevent the incidence of α rays, and the detection element to which the electrode 3 belongs extracts only the output signal generated by the incidence of β rays and γ rays. The determination of this thickness can also be calculated from the range of α rays in aluminum. The energy of α rays is 5.1 MeV at ²³⁹ Pu,
²³⁸ U has 4.1 Me, and aluminum having a thickness of about 30 μm is enough to block α rays of 5 Me. Next, the thickness of the electrode 4 is set so that all radiation can enter. If the thickness of aluminum is selected to be several μm, the thickness should not interfere with the incidence of α rays, which has a small penetrating power, and should not hinder the collection of charges (electron / hole pairs) in the detection element. Good. In the detection element to which the electrode 4 belongs, output signals generated by incidence of α rays, β rays, and γ rays are extracted. Electrode attachment to semiconductor materials is generally easily attached by vapor deposition. The thick electrode may be formed by depositing a thin electrode and then bonding a thin electrode having a predetermined thickness. In this case, the signal lines are led out from the electrodes deposited on the semiconductor. Next, in order to make the electrode 5 sensitive to neutron rays, an aluminum electrode of the same size as the electrode 4 of several μm is provided, ⁶ Li (lithium) of several μm is provided on the upper part thereof, and 30 μm which is the same as the electrode 3 is provided on the upper part thereof. Provide thick aluminum. In the detection element to which this electrode 5 belongs, the uppermost aluminum layer blocks α rays incident from the outside, and α generated by the reaction of ⁶ Li and neutron rays (nuclear reaction of n and α) provided in the intermediate layer. Output signals generated by the particles and β rays and γ rays incident from the outside are extracted. The outputs of the above detection elements are summarized as follows. Output of detection element to which electrode 2 belongs: Output of detection element to which detection electrode 3 of γ-rays belongs: Output of detection element to which detection electrode 4 of γ-rays and γ-rays: Detection electrode 5 of α-rays, β-rays and γ-rays Output of the detection element to which the electrode belongs: Detection of neutron rays, β rays, and γ rays As it is, an output signal that identifies only the γ ray can be obtained from the detection element to which the electrode 2 belongs, but a detection element to which another electrode belongs Does not give an output that clearly identifies the radiation quality. FIG. 2 shows a configuration for obtaining a dose rate in which the radiation quality is discriminated based on these detection element output signals. As shown in the figure, the output signal from each detection element to which each electrode 2, 3, 4, 5 belongs is input to the logic operation unit 10 via the amplifier 8 and the integrator 9. The output of the detection element to which the electrode 2 belongs is directly sent to a display unit 11 including a dose rate correction circuit (converting mR / hr, CPS, etc.) 20 and a display element 21, and displays the dose rate of only γ rays. On the other hand, the output of the detection element to which the electrode 3 belongs is subtracted by the value obtained by multiplying the output of the detection element to which the electrode 2 belongs by the correction coefficient f ₁ to obtain a value that depends only on β rays, and this value is displayed. The dose rate of only the β-rays sent is displayed at 11. The correction coefficient f ₁ is used to correct the attenuation of γ-rays due to the thickness of the electrode 2 and the normalization correction between the detection elements. The output of the detection element to which electrode 2 belongs is subtracted from the output of the detection element to which electrode 2 is multiplied by a correction coefficient f ₁ and the output of the detection element of electrode 3 is multiplied by a correction coefficient f _2. Therefore, the value depends only on α-rays, and this value is sent to the display unit 11 so that only α-rays are transmitted. Show dose rate. Correction factor f ₂ is attenuation correction of β-rays by the thickness of the electrode 3, is to implement correction of the normalized between the detecting elements. The output of the detection element that belongs electrode 5, electrode 2 by subtracting the value obtained by multiplying the output of the detection element to which the electrode 3 belongs by the correction coefficient f ₁ and by subtracting the value obtained by multiplying the output of the detection element to which the electrode 3 belongs by the correction coefficient f ₃ This value is sent to the display unit 11, and the correction coefficient f ₃ for displaying the dose rate of only the neutron beam is for correcting the standardization between the detection elements. Then, the dose rate for each radiation quality can be measured.Attenuation of various kinds of radiation due to the thickness of the electrode 4 and the thickness of the lithium layer provided on the electrode 5 is significantly smaller than the others, and each correction coefficient f ₁ , complement correction normalization between the detecting elements included in f _2, f ₃ Possible. In addition, the dose rate correction circuit 20 in the display unit 11 in accordance with a beam quality was identified, mR / hr in the case of γ-rays, alpha rays, for β-ray CPm, for neutron n / cm ² · It is converted based on the calibration data as the value of s, etc. The system of the applied voltage is not shown in Fig. 2. Further, it is provided at the output of each detection element to which each electrode belongs. The same logical processing can be easily performed by the digital processing by the one-chip microprocessor in the subsequent stages after the integrator 9. Needless to say, of the various elements shown in FIG. To two rows (Here, the rows arranged vertically in FIG. 2, that is, in the vertical direction, are called rows)
If only the circuit of the correction coefficient f ₁ between the above two columns among the circuits of the correction coefficient shown by the horizontal line in the logical operation unit 10 is provided, only the γ-ray and the β-ray are provided. The dose rate can be measured. Similarly, if only the three columns from the left are provided and only the circuits of the correction factors f ₁ and f ₂ between these three columns are provided, it is possible to measure each dose rate of only γ rays, β rays and α rays. Become. Similarly, if only three columns other than the third column from the left are provided and only the circuits having the correction factors f ₁ and f ₃ between these three columns are provided, each of only γ rays, β rays and neutron rays can be obtained. The dose rate can be measured. The above-described embodiment is an example in which detection elements having different electrode structures are provided in combination on the same semiconductor material 1. However, by combining detection elements made of independent semiconductor materials having different electrode structures, The present invention can also be implemented. FIG. 3 shows a state in which the detection elements 22, the amplifier 23, the logic unit 24, and the display unit 11 are hybridized and mounted. The actual size of each detecting element can be about 10 mm square × 1 mm thick, and even if the amplifier, the logic unit and the display unit are included, they can be mounted in an extremely small size of 50 mm ^□ × 5 mmt or less. In the above-described embodiment described with reference to FIGS. 1 and 2, 30 μm thick aluminum that blocks only transmission of α rays is provided on the uppermost part of the electrode 5 of the detection element for detecting neutron rays. , 1.4 mm thick aluminum for blocking transmission of α rays and β rays is provided on the uppermost part of the electrode 5, and the circuit of the correction coefficient f ₃ in the logical operation unit 10 is deleted. Even with the same configuration as the above-described embodiment of FIG. 2, each dose rate of α rays, β rays, γ rays and neutron rays can be measured. Needless to say, among the elements in such a configuration, only the first and fourth columns from the left in FIG. 2 are provided and only the circuit of the correction coefficient f ₁ between these two columns is provided. If provided, each dose rate of only γ-rays and neutrons can be measured, and only three columns except the third column from the left are provided and the correction factors f ₁ , f ₃ between these three columns are provided.
If only the circuit of 1 is provided, each dose rate of only γ rays, β rays and neutron rays can be measured. FIG. 4 shows a modified embodiment. This has electrodes 31 and 32 of the same structure provided on both surfaces of the semiconductor material 1 of each detection element, and enables the dose rate measurement of the radiation incident from both surfaces for each radiation quality. The lithium ( ⁶ L
An embodiment using boron ( ¹⁰ B), helium ( ³ He) or the like instead of i) is also possible. Since helium is a gas, when it is used, the inside of the case housing the detector 33 is filled with helium 35 as shown in FIG. Further, as shown in FIG. 6, by using a detection element in which electrodes 36 and 37 are provided outside and in the center of a cylindrical semiconductor 38, radiation detection with higher sensitivity and near omnidirectionality can be realized. In the figure, V _B is the applied voltage, 12 is the depletion layer, and 39 is the detection output. [Effect of the Invention] According to the present invention, it is possible to realize a high-performance radiation detector capable of identifying each radiation quality in real time and measuring each dose rate in an atmosphere in which various radiations are mixed. In addition, even if all the applied voltages to the detection elements are the same, a radiation blocking material having a different ability to block incident radiation or a material that causes a (n, α) reaction with a neutron beam can be provided by a simple means. Output information that is significant to
According to the present invention, no external manual operation for identifying the radiation quality is required. In addition, since the voltage applied to the detection element can be commonly used, the circuit configuration is extremely simple, and it can be mounted in a small size. Therefore, the application to the individual exposure control measurement such as the conventional film batch and TLD, and the application to various radiation monitors and survey meters can be easily developed. Further, it can be applied to a reprocessing facility monitor in which neutron ray and α ray monitoring are important, and an inline monitor of a reprocessing process. In particular, the present invention greatly exerts its function for the measurement of the atmosphere in which various radiation ray qualities are mixed, such as in a reprocessing facility.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing the configuration of a logical operation unit of the same embodiment, and FIG. 3 is a mounting state of a hybridized detector. FIG. 4, FIG. 4 is a view showing a modification of the electrode, FIG. 5 is a view showing a gas-filled type detector, and FIG. 6 is a perspective view showing an example of another detection element. (Explanation of symbols) 1 ... Semiconductor 2, 3, 4, 5 ... Electrode 6 ... Output signal line 7 ... Electrode 8 ... Amplifier 9 ... Integrator 10 ... Logical operation unit 11 ... Display 12 ... Depletion layer 20 ... Dose rate correction circuit 21 ... display unit 22 ... detecting element 23 ... amplifier 24 ... logical Yunitsuto R ... resistance V _B ... applied voltage 31, 32 electrodes 33 ... detector 34 ... detector housing case 35 ... helium 38 ... semiconductor 39 ... detection signal output .

Claims (1)

Claim: What is claimed is: 1. An electron-hole pair produced by radiation passing through an electrode in a depletion layer formed in the semiconductor when a voltage is applied between electrodes sandwiching the semiconductor, is collected and detected by the electrode. In the radiation detecting element configured as
Radiation detecting element that allows only γ-rays to pass through the electrode as radiation that causes hole pairs, radiation detecting element that allows only γ-rays and β-rays to pass through the electrode, and radiation detection that allows γ-rays, β-rays and α-rays to pass through the electrode At least the former two of the elements are provided, and further, a subtraction process in which the correction coefficient is multiplied is performed between the detection outputs of the provided radiation detection elements to perform a γ-ray dose rate, a β-ray dose rate and A radiation detector comprising a logical operation circuit for calculating outputs corresponding to at least the former two of the dose rates of α rays, and a display for displaying these outputs of the logical operation circuit, respectively. 2. The radiation detector according to claim 1, wherein the electrode pair of each radiation detection element is provided at a different portion of a common semiconductor. 3. The radiation detector according to claim 1, wherein the electrode pair of each radiation detection element is provided on a separate semiconductor. 4. A semiconductor is sandwiched between electrodes provided with a material which allows transmission of only neutron rays, γ rays and β rays, and which is provided on the back side with a material which reacts with neutron rays to generate α particles, and a voltage is applied between the electrodes. To collect and detect α-particles generated by the reaction between the neutron beam that has passed through the electrode and the above material in the depletion layer formed in the inside and electron-hole pairs generated by γ- and β-rays that have passed through the electrode In addition to being equipped with a radiation detection element configured as described above, the electrodes collect and detect electron-hole pairs generated by the radiation passing through the electrodes in the depletion layer formed in the semiconductor when a voltage is applied between the electrodes sandwiching the semiconductor. A radiation detecting element configured to perform radiation of only γ-rays as radiation that causes electron-hole pairs in the depletion layer, allowing radiation of only γ-rays and β-rays. No radiation detector In addition, at least the former two of the radiation detecting elements which allow the γ-ray, β-ray and α-ray to pass through the electrode are provided, and the detection output of each radiation detecting element provided above is multiplied by a correction coefficient. The subtraction process is applied to the neutron dose rate,
A logic operation circuit for calculating outputs corresponding to at least the former three of the γ-ray dose rate, β-ray dose rate and α-ray dose rate, and a display for displaying these outputs of the logic operation circuit, respectively. A radiation detector comprising: 5. The radiation detector according to claim 4, wherein the electrode pairs of the radiation detection elements are provided at different portions of a common semiconductor, respectively. 6. The radiation detector according to claim 4, wherein the electrode pair of each radiation detection element is provided on a separate semiconductor. 7. A semiconductor is sandwiched between electrodes provided with a material which allows only neutron rays and γ rays to pass therethrough and produces α particles by reacting with neutron rays on the back side, and is formed in the semiconductor by applying a voltage between the electrodes. Detection configured to collect and detect electron-hole pairs generated by α-particles generated by the reaction between the neutron beam transmitted through the electrode and the above-mentioned material in the depletion layer and γ-ray transmitted through the electrode at the electrode It is equipped with an element and is configured to collect and detect electron-hole pairs generated by the radiation transmitted through the electrode in the depletion layer formed in the semiconductor by applying a voltage between the electrodes sandwiching the semiconductor. A radiation detection element, which is a radiation detection element that allows only γ-rays to pass through the electrode as radiation that produces electron-hole pairs in the depletion layer, a radiation detection element and γ-rays that allows only γ-rays and β-rays to pass through the electrode, β rays and At least the first of the radiation detecting elements that allow the α-rays to pass through the electrode is provided, and further, the subtraction processing by multiplying the detection output of each of the provided radiation detecting elements by a correction coefficient Dose rate,
A logic operation circuit for calculating outputs corresponding to at least the former two of the γ-ray dose rate, β-ray dose rate, and α-ray dose rate, and a display for displaying these outputs of the logic operation circuit, respectively. A radiation detector comprising: 8. The radiation detector according to claim 7, wherein the electrode pair of each radiation detection element is provided at a different portion of a common semiconductor. 3. The radiation detector according to claim 7, wherein the electrode pair of each radiation detection element is provided on a separate semiconductor.