JPH09101371A - Gamma ray detection method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for remotely detecting the direction where a gamma ray source exists or the location of the gamma ray source without using a collimator. SOLUTION: Split-type germanium detectors 1 and 2 are arranged before and behind, an incidence angle θ of gamma rays 52 is repeatedly obtained based on the positional relationship between two detection cells A and B and the energy detected by the detection cells A and B for the gamma rays 52 which are incident on the detection cell A of the forward detector 1 and are subjected to Compton scattering and then incident on the detection cell B of the backward detection cell B to be absorbed, and a plurality of obtained incidence angles are combined, thus detecting the direction and position where the gamma ray source exists.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gamma ray detecting method and a gamma ray detecting device, and more particularly to a gamma ray detecting method and a gamma ray detecting device capable of specifying a direction or a position of a gamma ray source.

[0002]

2. Description of the Related Art At present, as a simple gamma ray detector,
A scintillation detector using a crystal such as sodium iodide as a scintillator or a semiconductor detector using germanium or silicon is known. In order to use these gamma-ray detectors to find the location of radioactive contamination at reactor facilities, etc., a two-dimensional sodium iodide crystal detector that has a directional orientation by equipping a perforated lead shielding collimator is used. A radioactive contamination position is specified by a method of moving or a method of measuring a radiation intensity by bringing a portable survey meter incorporating the detector close to a place where there is a possibility of contamination.

[0003] Positron C in the field of nuclear medicine
At T, a number of small gamma ray detectors are installed around the subject, and emitted in the opposite direction as the positron annihilation occurs.
It has been practiced to measure the distribution of positron emitters by measuring a large number of gamma rays in a book and use it for diagnosis.

[0004]

The sodium iodide crystal detector equipped with the perforated lead shield is large in size and heavy, and requires a mechanism for moving it. Becomes In addition, since the sodium iodide detector has poor energy resolution with respect to gamma rays, it is difficult to identify many nuclides at the same time. On the other hand, various survey meters are light, but cannot determine the position of the source unless they are very close to the source, and have very low or no energy resolution for gamma rays. Therefore, it is difficult to identify nuclides.

The gamma ray detector used in the positron CT is very expensive, and the radiation source whose position can be identified by this detector is limited to positron emitting nuclides. The present invention has been made in view of the present situation of such a gamma ray detector, and has provided a method and apparatus capable of remotely detecting the direction in which the gamma ray source exists, and thus the position of the gamma ray source, without using a collimator. The purpose is to provide.

[0006]

According to the present invention, two divided detectors are used, a gamma ray detection position in each of the divided detectors is identified, and the detection positional relationship and the kinematics of Compton scattering are used. In other words, the gamma ray detection method of the present invention performs gamma rays incident on the first detection cell and subjected to Compton scattering and then incident on the second detection cell and absorbed. 1st and 2nd
By repeatedly performing the operation of obtaining the gamma ray incident angle based on the positional relationship of the detection cells and the energy detected by the first and second detection cells, and combining the obtained plurality of incident angles. Is characterized by detecting a direction or a position in which is present.

At this time, a specific energy is obtained by combining a plurality of incident angles obtained for gamma rays having the same sum of the energy detected by the first detection cell and the energy detected by the second detection cell. Direction or existence distribution of nuclides that emit gamma rays can be detected. Further, the detected gamma rays are grouped according to the sum of the energy detected by the first detection cell and the energy detected by the second detection cell, and the gamma rays belonging to the group are obtained for each group. When a plurality of nuclides are present, the direction or existence distribution of each nuclide can be detected by combining the given incident angles.

A gamma ray detecting apparatus according to the present invention excludes first and second gamma ray detectors each comprising a plurality of detection cells arranged side by side and a gamma ray incident surface of the first and second gamma ray detectors. A scintillation detector surrounding the periphery, a first gamma ray detector and a second
A plurality of peak-height analyzers for analyzing the output signals of the respective detection cells of the gamma-ray detectors, the output signals of the detection cells of the first and second gamma-ray detectors, and the output signal of the scintillation detector, And the output signal from one detection cell of the second gamma ray detector and the output signal from one detection cell of the second gamma ray detector are simultaneously inputted, and the output signal from the scintillation detector is not inputted. A coincidence circuit that outputs a gate signal to the
An electronic computer to which a signal from the pulse height analyzer is input when the gate signal is output, and a display device for displaying an output of the electronic computer, wherein the electronic computer generates an output signal in the first gamma ray detector. The direction or position of the gamma ray source is calculated based on the position information of the detected detection cell and the detection cell that has generated the output signal in the second gamma ray detector and the output signal from the pulse height analyzer, and the result is displayed. The information is displayed on a device.

The first and second gamma ray detectors are preferably split germanium detectors, and the scintillation detector preferably has a scintillator made of a single crystal of bismuth germanate. As a display device for displaying the detection result, a display device or an image display device that can easily display a direction by combining a marker line and a display element such as a light emitting diode in a housing of a gamma ray detection device may be employed. it can. When an image display device is adopted as the display device, an image pickup device having an optical axis substantially coincident with the optical axis of the gamma ray detection device is provided, and the direction or the position of the gamma ray source determined by the computer is displayed on the display device. Specify in the displayed image.

According to the present invention, a plurality of source positions can be identified at the same time without moving two divided gamma ray detectors. Further, since the two germanium detectors are housed in one vacuum vessel, the apparatus becomes compact and has excellent mobility. The gamma ray detection device of the present invention uses a split germanium detector and a Compton suppression shield made of bismuth germanate crystal, so that a gamma ray spectrum with an extremely low background can be obtained.
High sensitivity can be realized. Further, since the energy resolution with respect to gamma rays is high, it is also excellent in the ability to identify nuclides.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to examples. FIG. 1 is a schematic diagram showing one embodiment of a gamma ray detecting device according to the present invention. The gamma ray detection device in FIG. 1 includes a detection unit 10 that generates an electric signal pulse when gamma rays are incident, and a signal processing unit 30 that processes the electric signal generated by the detection unit 10. The detection unit 10 includes a germanium detector arranged in the vacuum container 4.
The germanium detector includes a first split type germanium detector 1 disposed on the light receiving surface, and a second split type germanium detector disposed behind the first type germanium detector.
And two split-type detectors.

The first split type germanium detector 1 of this embodiment has a size of about 5 cm × 5 cm × 2 cm, and as shown in detail in FIG. 2, 5 × 5, ie, 25 cells A _mn.
(M = 1-5, n = 1-5), and each detector cell _Amn of the detector is supplied such that an output signal indicating the interaction between the cell and the gamma ray is generated independently. Electric wires and output wires are connected. The second split germanium detector 2 arranged behind the first split germanium detector 1 also has a size of approximately 5 cm × 5 cm × 2 cm and has 5 × 5, ie 25 cells B _mn. (M = 1-5, n
= 1 to 5), and the feeder line and the output line are connected such that output signals indicating the interaction between the cell and the gamma ray are generated independently from each cell B _mn of the detector. I have. However, the number of divisions of the detectors 1 and 2 is not limited to 25. The number of divisions is increased when high positional accuracy is required, and is decreased when high accuracy is not required. For example, an appropriate number can be set according to the required detection accuracy. The split germanium detectors 1 and 2 are used after being cooled to a low temperature by an appropriate cooling means using a refrigerant, a cryopump, or the like. The example shown in FIG. 1 uses liquid nitrogen as the cooling means, and the split detectors 1 and 2 are fixed and cooled by a copper cold finger 6 cooled by liquid nitrogen in a liquid nitrogen container 5.
In use, a high DC voltage is applied to each cell of the split type germanium detectors 1 and 2 from the high voltage power supplies 31a and 31b.

The periphery of the vacuum container 4 except for the light receiving side is surrounded by a scintillation detector 7. As the scintillator of the scintillation detector 7, it is preferable to use a bismuth germanate single crystal from the viewpoint of gamma ray detection efficiency. In this embodiment, four rectangular plate-like bismuth germanate single crystals having a trapezoidal cross section are combined to form a hollow quadrangular prism, and the vacuum vessel 4 is disposed in the central hollow portion. The scintillation detector 7 is a photomultiplier tube 8
a, 8b, and a high-voltage power supply 31
High voltage is applied from c and 31d. Although only two photomultiplier tubes are shown, a larger number, for example, four photomultiplier tubes are provided in order to increase the light collection efficiency of scintillation. Output signals from the plurality of photomultiplier tubes 8a and 8b are finally coupled to one signal line and used for anti-simultaneous measurement as described later.

Before describing the operation of the signal processing section 30 of FIG. 1, the principle of gamma ray detection of the present embodiment will be described with reference to FIG. 3, which is an enlarged sectional view of the detection section 10 shown in FIG.
It is assumed that there is a nuclide (gamma ray source) 50 that emits gamma rays at a certain position in front of the detection unit of the gamma ray detection device. The same nuclide emits gamma rays 51, 52, 53,... Of one or more kinds of fixed energy. The illustrated gamma ray 51 is subjected to Compton scattering in one cell of the first split-type germanium detector 1, and then does not enter the second split-type germanium detector, but the scintillator 7 does not.
Shows the incident light. The gamma ray 52 is incident on one cell A of the first split type germanium detector 1 and is subjected to Compton scattering there, and then is incident on the cell B of the second split type germanium detector 2 and loses all energy there. It is a thing. The gamma ray 53 is subjected to Compton scattering in one cell of the first split type germanium detector 1 and further Compton scattered in one cell of the second split type germanium detector 2 and is incident on the scintillator 7. Show things.

Here, a gamma ray having a constant energy E enters one cell of the first split type germanium detector 1 and undergoes Compton scattering, and the second split type germanium detector 2 arranged behind the same. Of the gamma ray 52 shown in FIG. This event can be selected by performing simultaneous measurement and anti-simultaneous measurement in the signal processing circuit 30 shown in FIG. Here, for the sake of simplicity, it is assumed that the scattering direction of the gamma ray is a direction parallel to the optical axis of the detection unit, and the two cells A and B on which the gamma ray is incident are located at a position overlapping the optical axis direction of the detection unit. At this time, gamma rays 5
2 imparts energy E _C in front of the cell A, in order to impart energy of E _a in the rear of the cell B, the following equation (1)
Holds. E = E _C + E _a (1)

From the kinematics of Compton scattering, the incident angle θ of the gamma ray 52 to the first split type germanium detector is α = E / m ₀ c ² (m ₀ c ² = 511 keV: static mass of electrons) , E is in keV) and R = E _C / E, and is calculated by the following equation (2). θ = cos ⁻¹ [1-R / {α · (1-R)}] (2)

From these relations, the incident angle θ of the gamma ray 52 with respect to the cell A of the first split type germanium detector 1 is known, and the gamma ray source has an apex angle with respect to a straight line connecting the cell A and the cell B behind. Is on the extension of the conical surface of 2θ. In practice, the angle of incidence θ is
Since it is determined as an angle range (θ ± Δθ) depending on the size of B, the distance between the first split type germanium detector 1 and the second split type germanium detector 2, etc., the possibility of the existence of a gamma ray source As shown in FIG.
Line 4 connecting cell A of the second detector and cell B of the second detector
5 as a conical surface 46 having a certain thickness. Therefore, when two or more sets of such events are measured, a conical surface is formed for each combination, and a region where the conical surfaces overlap is obtained, the region is a region where the gamma ray source 50 exists. As the number of measured events, that is, the number of conical surfaces, increases, the overlapping region can be narrowed, and the direction or position of the gamma ray source can be determined with high accuracy. The overlapping area of the conical surfaces is finally output to the display device as the direction (δ, ω) or position with respect to the central axis O of the detector as shown in FIG.

The above description is for the case where the scattering direction of the gamma rays is parallel to the optical axis of the detection unit, and the two cells A and B, on which the gamma rays have entered, are located at positions overlapping the optical axis direction of the detection unit. It is. As shown in FIG. 6, the gamma ray 54 from the gamma ray source 50 is Compton-scattered by the cell A _ij of the first split type detector 1 and the second split type detector 2
In general, when the _light is incident on the cell B _mn and the entire energy is absorbed therein, the above equation (2) is replaced by the following equation (3). Here, the angle φ (A _ij , B _mn ) is a straight line connecting the center of the cell A _ij in the first split type detector and the center of the cell B _mn in the second split type detector. Which is a known value. θ = cos ^-1 [1-R / {α · (1-R)}]-φ (3)

As understood from the equation (3), when this generalized relational equation (3) is used, the positional relationship φ (A _ij , B _mn ) between the preceding and _succeeding cells A _ij and B _mn. Since it is only necessary to know this, the first split type detector 1 and the second split type detector 2 are not necessarily required to have the same shape, and the cell A _mn in the first split type detector and its corresponding It is not necessary to arrange the cell B _mn in the second split type detector to overlap in the optical axis direction.

Here, the resolution of the gamma ray detector according to the present invention will be briefly evaluated. The accuracy of determining the position of the gamma ray source by the gamma ray detector of the present invention depends on the cell size of the split type detector, the interval between the first split type detector and the second split type detector, and the gamma ray source and the detector. Depends on the distance between The position determination accuracy generally improves as the cell size decreases, the distance between the detectors increases, and the distance between the gamma ray source and the detection device increases.

As a typical example, one piece is 1 cm in size.
Consider a case where a first split type detector and a second split type detector composed of 25 cells of 1 cm × 2 cm are arranged at an interval of 10 cm. The gamma source is assumed to be at a distance of 50 cm on the central axis of the detector. The angle at which the gamma ray source sees one cell of the first split detector is 1.
Although it has a spread of 2 to 2.9 degrees, the gamma ray incident angles are all approximated to be 2.3 degrees. The positioning error due to this is less than 1 cm. Next, an error due to the uncertainty of the angle that the cells of the first and second split type detectors can see will be considered. When using the relationship of the above formula (3), the angle at which the uppermost cell of the first split type detector looks at the lowermost cell of the second split type detector is determined by the straight line connecting the centers of both cells. Although the angle formed with the optical axis is 18.4 degrees, it has a spread of 12 to 26.5 degrees. The position determination error due to this is estimated to be ± 7 cm. As described above, the position determination accuracy is determined by setting the cell size to, for example, 0.5 c
By making it as small as mx 0.5 cm x 2 cm, it is improved almost in inverse proportion to the cell size, and by increasing the interval between the two split type detectors, it is improved almost in proportion to the interval.

Next, returning to FIG. 1, the operation of the signal processing unit 30 will be described. The pulse signal generated from each cell of the first split type germanium detector 1 is a preamplifier 32a connected to each cell (only one is shown in FIG. 1).
After that, they are further shaped and amplified by the linear amplifier 33 and input to the wave height analyzer 34. The linear amplifier has a function of amplifying the input signal waveform proportionally without distortion. Similarly, pulse signals generated from each cell of the second split type germanium detector 2 were individually amplified by preamplifiers 32b (only one is shown in FIG. 1) connected to each cell. Thereafter, the signal is further shaped and amplified by the linear amplifier 33 and input to the wave height analyzer 34. FIG.
, A preamplifier, a linear amplifier, and a pulse height analyzer are provided for each cell.

The detection signals amplified by the preamplifiers 32a and 32b are also amplified by the high-speed amplifiers 36a and 36b.
It is input to the high-speed discriminators 37a and 37b. High-speed amplifier 3
6a, 36b and fast discriminator 37a, 37b is 10 ^-8
It has an extremely fast time response characteristic of about seconds. Therefore,
The high-speed discriminator 37a is the first split type germanium detector 1
When a gamma ray is incident on any of the cells, a signal is generated at the same time and a signal is input to the simultaneous measurement circuit 38. The high-speed discriminator 37b is connected to any of the cells of the second split type germanium detector 2. When gamma rays are incident,
At the same time, a signal is input to the simultaneous measurement circuit 8.

On the other hand, output signals from the photomultiplier tubes 8a and 8b of the scintillation detector 7 are amplified by a high-speed amplifier 39, and the amplified signals are further input to a high-speed discriminator 40. The output of the high-speed discrimination circuit 40 is
8 is provided as an anti-coincidence input. Simultaneous measurement circuit 3
8 outputs a gate signal to the pulse height analyzer 34 only when there is an input from the high-speed discriminators 37a and 37b at the same time and there is no anti-coincidence input from the high-speed discriminator 40. FIG.
The operation of the simultaneous measurement circuit 38 will now be described. In FIG.
a is the output signal of the high-speed discriminator 37a, b is the high-speed discriminator 37
b indicates an output signal, c indicates an output signal of the high-speed discriminator 40, and d indicates a gate signal output from the simultaneous measurement circuit 38. FIG.
Shown in the timing of T _1, a state where a and c is output b is not outputted, namely indicates the detection state of the gamma ray 51 in FIG. 3, the gate signal d is in this case is not output. Shown in the timing of T ₂ are,
This indicates a state in which a and b are output and c is not output, that is, a detection state of the gamma ray 52 in FIG. 3, and a gate signal d is output. Similarly, the timing of T ₃ indicates the detection state of the gamma rays 53 in FIG. 3, the gate signal d is not output.

By using the simultaneous measurement circuit 38 in this manner, noise data corresponding to the detection of the gamma rays 51 and 53 shown in FIG. 3 is discarded, and only data to which the above equation (2) or (3) is applied is discarded. Can be extracted. When receiving the gate signal from the coincidence circuit 38, the wave height analyzer 34 receives the two signals output from the linear amplifier 34, that is, the first split-type germanium detector that caused the generation of the gate signal. The result of pulse height analysis of the output pulse from one specific cell A _ij and the specific cell B _{mn of} the second split type germanium detector 2 is output to the electronic computer 35.

The electronic computer 35 includes a first split type detector 1
The angle data φ (A _ij , B _mn ) between each cell in the second divided type detector 2 is stored, and which cell A _ij , B _mn is the two cells that have generated the output. By knowing the angle φ, the angle φ is known. Further, the energy E _C detected in the cell A _ij and the energy E _a detected in the cell B _mn are known from the data transmitted from the pulse height analyzer 34,
The energy E of the gamma ray is obtained by adding the two energies based on the above equation (1). Then, data for a gamma ray having a predetermined specific energy E corresponding to a specific nuclide is selected, and by using the selected data, the calculation of the above equation (2) or (3) is performed. The incident angle θ ₁ is obtained, and as shown in the conceptual diagram of FIG.
A conical surface having a cell A _ij as a vertex and an apex angle of 2θ ₁ is calculated. Similarly, for a plurality of gamma ray incident angles θ ₂ ,
θ _3, ..., determine the theta _n, vertical angle 2 [Theta] ₂ incident cell A _ij of each as the vertex, 2θ _3, ..., and calculates the conical surface of the 2 [Theta] _n, calculates the overlap region. The overlapping area of the plurality of conical surfaces calculated in this manner represents the direction or position where the gamma ray source exists, and is displayed on the display device 42 in real time in relation to the axial direction of the gamma ray detecting device.

Also, without specifying the energy of the gamma ray,
The detected gamma ray is converted to energy E ₁, E_Two, E_Three……
Therefore, the incident angle θ for each gamma ray of each energy
₁(E₁), Θ_Two(E₁), Θ_Three(E₁),…, Θ_n(E₁); Θ
₁(E_Two), Θ_Two(E_Two), Θ_Three(E_Two),…, Θ_n(E_Two); Θ
₁(E_Three), Θ_Two(E_Three), Θ_Three(E_Three),…, Θ_n(E_Three);
Cell A where each gamma ray was incident_ijThe position of the vertex
Angle 2θ calculated₁(E₁), 2θ_Two(E₁), 2θ
_Three(E₁), ..., 2θ_n(E₁The area where the conical surface of
Lugie E₁Gamma ray source that emits gamma rays
Display as direction or position, apex angle 2θ₁(E_Two), 2θ
_Two(E_Two), 2θ_Three(E_Two), ..., 2θ_n(E_Two) Conical surface overlap
Energy E_TwoGamma ray emitting gamma ray of
Indicated as the direction or position where the source exists, the apex angle 2θ
₁(E_Three), 2θ_Two(E_Three), 2θ_Three(E_Three), ..., 2θ_n(E_Three) Circle
Energy E_ThreeEmits gamma rays
As the direction or position of the gamma ray source
By doing so, multiple sources and multiple nuclides can be
It can be identified simultaneously including the direction or position.

When the equation (2) is used as an arithmetic expression, the first split type detector 1 and the second split type detector 2 detect a cell corresponding to the same split type detector. It is necessary to arrange them so as to overlap in the optical axis direction of the vessel. Also,
The electronic computer 35 selects and uses only the data in the case where the two cells that have generated the signal are located at positions overlapping in the optical axis direction of the detector among the data sent from the pulse height analyzer 34.

When the gamma ray detecting device of the present invention is used by being fixed to a gamma ray utilizing device, for example, a main body of a positron CT, the optical axis of the detecting device does not move in a predetermined direction with respect to the gamma ray utilizing device. The direction or spatial position of the detected gamma ray source can be specified by calibrating the angle output by the detecting device in advance for the gamma ray utilizing device. At that time, by installing two sets of the gamma ray detecting device of the present invention at a position separated by 90 °, for example, the spatial position measurement accuracy of the gamma ray source can be improved.

Next, a method of displaying a detection result when the gamma ray detecting device of the present invention is used as a portable device in a field will be described. FIG. 8 shows an embodiment in which the detected flight direction of the gamma ray is simply displayed by a light emitting diode. The gamma ray detection device 60 of the present embodiment has the detection unit 10 and the signal processing unit 30 described in FIG. 1 therein, and the marker lines 6 are provided on the top and side surfaces of the housing at intervals of, for example, 10 °.
1, 62 are provided, and a light emitting diode 65 is embedded at the tip of each marker line. The electronic computer 35 incorporated in the main body of the gamma ray detecting device 60 turns on or off the light emitting diode 67 indicating the angle δ and the light emitting diode 68 indicating the angle ω according to the angle information obtained by the above-described calculation. A person who handles the detection device 60 can easily know the direction in which the gamma ray source exists by displaying the light emitting diode.

FIG. 9 is a schematic diagram showing another embodiment of the display method when the gamma ray detecting device is portable. In this embodiment, the position of the gamma ray source detected by the gamma ray detecting device is displayed on a monitor screen, and the gamma ray detecting device 70 described with reference to FIG. 1 and an imaging device 80 such as a TV camera are used in combination. The optical axis 71 of the gamma ray detecting device 70 and the optical axis 81 of the imaging device 80 are set in parallel, and both observe the same field of view with an offset d. Data indicating the direction of the gamma ray source determined by the gamma ray detecting device 70, for example, (δ, ω), and image data from the imaging device 80 are input to the image processing device 83.

FIG. 10 schematically shows a relationship between a subject 95 picked up by the image pickup device 80 and an image 96 formed on the image pickup device 91 composed of a two-dimensional CCD by the image forming optical system 90. is there. Each point on the subject 95 corresponds to each point of the image sensor 91 on a one-to-one basis. That is, each element C _mn of the image sensor 91 receives a light beam in the angular direction (δ _m , ω _n ) with respect to the optical axis 81 of the image pickup device 80. Therefore, each pixel on the monitor 85 is also connected to the optical axis 8 of the imaging device 80.
1 corresponds to an angular direction of (δ _m , ω _n ).

The image processing device 83 uses the angle data from the gamma ray detecting device 70 by utilizing the above-described relationship.
0 image data is processed. For example, if an angle (δ, ω) is output from the gamma ray detection device 70 as the direction in which the gamma ray source exists with respect to the optical axis 71, the image processing device 83 corresponds to that angle in the image displayed on the monitor 85. The pixel 86 is highlighted, for example, by blinking or displaying the pixel 86 with a specific color. The intensity of blinking can be changed according to the intensity of the detected gamma ray, or the color can be changed according to the difference in the energy of the detected gamma ray, that is, the nuclide. In this case, there is a deviation of the offset d between the actual detection direction and the display position on the monitor 85. However, since the distance d is very small, it does not pose a practical problem. It is extremely easy to correct and to specify the actual gamma ray source position.

[0034]

According to the present invention, the direction or position of the gamma ray source can be specified without using a collimator.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one embodiment of a gamma ray detecting device according to the present invention.

FIG. 2 is a schematic view of a split type germanium detector.

FIG. 3 is a diagram illustrating the principle of detecting the direction of a gamma ray source.

FIG. 4 is an explanatory diagram of an area where a gamma ray source may exist.

FIG. 5 is an explanatory diagram of a coordinate system for a detector.

FIG. 6 is a diagram illustrating the principle of detecting the direction of a gamma ray source.

FIG. 7 is a diagram showing a relationship between an input signal and an output signal of the coincidence circuit.

FIG. 8 is an explanatory diagram of one embodiment of a display device that displays the direction in which gamma rays exist.

FIG. 9 is a schematic diagram of an embodiment in which the direction in which gamma rays exist is displayed on a monitor.

FIG. 10 is a diagram illustrating a relationship between a subject and an image formed on an image sensor of the image capturing apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 1st division type germanium detector, 2 ... 2nd division type germanium detector, 4 ... vacuum container, 5 ... liquid nitrogen container, 6 ... cold finger, 7 ... scintillation detector, 8a, 8b ... photoelectron increase Double tube, 10 ... Detection unit, 30
... Signal processing units, 31a, 31b, 31c, 31d ... High voltage power supply, 33 ... Linear amplifier, 34 ... Pulse height analyzer, 35 ... Electronic computer, 36a, 36b ... High speed amplifier, 37a, 37
b: High-speed discriminator, 38: Simultaneous measurement circuit, 39: High-speed amplifier, 40: High-speed discriminator, 42: Display device, 50: Gamma ray source, 51, 52, 53, 54: Gamma ray, 60: Gamma ray detection device, 61 , 62: marker line, 65: light emitting diode, 70: gamma ray detecting device, 80: imaging device, 83
... image processing apparatus, 85 ... monitor, 90 ... imaging optical system,
91: image sensor, 95: subject, 96: subject image

Claims (7)

[Claims] 1. A gamma ray incident on a first detection cell and subjected to Compton scattering after being incident on a first detection cell, and a positional relationship between the first and second detection cells with respect to a gamma ray incident on and absorbed by the second detection cell. The operation of obtaining the gamma ray incident angle based on the energy detected by the first and second detection cells is repeatedly performed, and by combining the obtained plurality of incident angles, the direction or position where the gamma ray source is present A gamma ray detection method, characterized in that a gamma ray is detected. 2. The method according to claim 1, wherein a plurality of incident angles obtained for gamma rays having the same sum of energy detected by the first detection cell and energy detected by the second detection cell are combined. Item 7. The gamma ray detection method according to Item 1. 3. The detected gamma rays are grouped according to the value of the sum of the energy detected by the first detection cell and the energy detected by the second detection cell, and gamma rays belonging to the group for each group. 2. The gamma ray detecting method according to claim 1, wherein the incident angles determined for the gamma rays are combined. 4. A first and a second gamma ray detector comprising a plurality of detection cells arranged side by side and a plurality of detection cells, and arranged so as to surround the first and second gamma ray detectors except for a gamma ray incidence surface. A scintillation detector, and a plurality of wave height analyzers that perform wave height analysis on output signals of each detection cell of the first gamma ray detector and the second gamma ray detector;
An output signal of a detection cell of the first and second gamma ray detectors and an output signal of the scintillation detector are input, and an output signal from one detection cell of the first gamma ray detector and the second gamma ray A coincidence circuit for outputting a gate signal to the pulse height analyzer when an output signal from one detection cell of the detector is inputted simultaneously and an output signal from the scintillation detector is not inputted; And a display device for displaying the output of the computer when the signal from the pulse height analyzer is input, wherein the computer generates an output signal in the first gamma ray detector. Based on the detected cell and the position information of the detection cell that generated the output signal in the second gamma ray detector, and the output signal from the wave height analyzer. Calculates the existence direction or position of the comma-ray source, a gamma ray detection device and displaying the result on the display device. 5. The gamma ray detecting device according to claim 4, wherein said first and second gamma ray detectors are split-type germanium detectors. 6. The gamma ray detecting device according to claim 4, wherein the scintillation detector includes a scintillator made of a single crystal of bismuth germanate. 7. An image pickup device having an optical axis substantially coincident with an optical axis of a gamma ray detecting device, wherein the display device has an image display unit for displaying an image picked up by the image pickup device. 7. The gamma ray detecting device according to claim 4, wherein the determined direction or position of the gamma ray source is indicated in the image.