JP3815730B2 - CHARGED PARTICLE DETECTOR, CHARGED PARTICLE DETECTOR MANUFACTURING METHOD, AND SENSING DEVICE HAVING CHARGED PARTICLE DETECTOR - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a charged particle detector that detects charged particles, a method for manufacturing the same, and a detection device including the same.
[0002]
[Prior art]
Examples of charged particle detectors used for detecting charged particles include gas detectors, semiconductor detectors, organic scintillation detectors, and inorganic scintillation detectors.
[0003]
Among these, the gas detector is operated by utilizing the ionizing action that occurs when radiation passes through the gas. Ionization chambers, proportional counters, Geiger-Muller counters, etc. There is. The ionization chamber is a detector that operates in a region (ionization region) where the collected charge is constant regardless of a change in applied voltage. Since the output signal is proportional to the energy of the charged particles, the energy of the charged particles can be measured. The proportional counter is a detector that operates in the region where primary ionization electrons created by charged particles cause secondary ionization and charge multiplication. The amplification factor is constant when the gas and applied voltage are determined. Therefore, as with the ionization chamber, the output signal is proportional to the energy of the charged particles, so that the energy of the charged particles can be measured. The Geiger-Muller counter is a detector that operates in a region where primary ionization electrons produced by charged particles cause electron avalanche, and has a shape and wave height that are determined only by the electronic circuit of the detector regardless of the primary ionization electrons. To create the signal, the number of charged particles can be counted, but the energy of the charged particles cannot be measured. Even in ionization chambers and proportional counters capable of measuring the energy of charged particles, the rise of the signal is as slow as a few milliseconds, so a high count rate (10 ^Five Measurement of high time resolution (1 nanosecond or less).
[0004]
A semiconductor detector is a detector that essentially operates in the same manner as an ionization chamber, and uses electrons and holes in a semiconductor instead of electrons and ions of a gas detector. Since it has superior energy resolution compared to other charged particle detectors, it is mainly used for measurements that require high energy resolution. In addition, compared with a gas detector, since the region for detecting charged particles is thinner and the velocity of electrons and holes is higher, a high count rate (10 ^Five Measurement per unit / second) and high time resolution (1 nanosecond or less). However, a semiconductor detector using silicon in which germanium or lithium is diffused needs to be kept at a low temperature during measurement, and must be continuously cooled with liquid nitrogen or the like. In addition, a surface-barrier silicon detector with an electrode that oxidizes the surface of high-purity silicon and deposits thin gold on the surface of the oxide film can be used at room temperature. Is likely to occur. For example, detection area 1 cm ² Surface barrier type silicon detectors with high count rate (10 ^Five It has been reported that when used for the measurement of α particles at a rate of 30 pcs / second or more, performance degradation occurs after about 30 hours of use.
[0005]
The scintillation detector is composed of a substance (scintillator) that generates fluorescence when charged particles enter and a device that converts and amplifies the fluorescence into an electrical signal. A detector using a scintillator made of an organic material is called an organic scintillation detector, and a detector using an scintillator made of an inorganic material is called an inorganic scintillation detector. Usually, a photomultiplier tube is used as a device for converting fluorescence into an electric signal and amplifying the electric signal. In addition, a photodiode is used as a device that converts fluorescence into an electrical signal. The amount of fluorescence emitted when a charged particle is incident has a proportional coefficient according to the type of charged particle and is almost proportional to the energy of the charged particle. If the type of charged particle can be identified, the energy of the charged particle can be measured. can do. Organic scintillation detectors have a very fast response time, so high count rates (10 ^Five Used for measurement with high time resolution (1 nanosecond or less). However, since the heat resistant temperature is about 150 ° C. because it is made of an organic material, it cannot be placed in a high temperature atmosphere of 200 ° C., for example. Since the inorganic scintillation detector has a high heat-resistant temperature (600 ° C. or higher), it can be placed in a high-temperature atmosphere of 200 ° C. or higher. However, since the response time is generally slow, a high count rate (10 ^Five Per unit / second) and high time resolution (1 nanosecond or less). However, even an inorganic scintillation detector using zinc oxide to which gallium is added is known as an inorganic scintillator having a very fast response time. If this scintillator is used, a high count rate (10 ^Five Measurement per unit / second) and high time resolution (1 nanosecond or less). However, since zinc oxide to which gallium is added has only been obtained in powder form, a binder that hardens the powder is necessary to use it in a scintillator. From the heat resistance of the binder, a high-temperature atmosphere of 200 ° C. or higher I could n’t put it inside.
[0006]
Here, for example, in a detection device for explosives and forbidden drugs using neutrons generated by a nuclear fusion reaction as exemplified in Non-Patent Document 1 and Patent Document 1, the background in the γ-ray detector is reduced. Therefore, in order to specify the position of explosives and forbidden drugs, it is necessary to detect α-rays, which are charged particles generated by a fusion reaction. For this reason, such a detection device requires a charged particle detector that detects charged particles. However, in order for the detection device to realize a low false detection rate and high-speed processing, the charged particle detector has a high heat resistance (200 ° C. or higher) and a high count rate (10 ^Five Etc.) and high time resolution (1 nanosecond or less) is required. Further, it is required that the performance does not deteriorate even when used for a long time. However, as described above, there is no conventional charged particle detector that satisfies such a requirement.
[0007]
[Non-Patent Document 1]
Report No. ANL / RE / CP-87590, ED RHODES, C.I. E. DICKERMAN, “NEW DE VELOPMENTS IN APSTNG NEUTRON PROBE DIAGNOSTICS”, Non-Instrumental Inspection Technology 1995, NDPP International Tec. 1-11.
[Patent Document 1]
Public information of National Table of Heisei 10-510621 (pages 17-19, Fig. 5)
[0008]
[Problems to be solved by the invention]
Therefore, the present invention has high heat resistance (200 ° C. or higher) and a high count rate (10 ^Five It is an object of the present invention to provide a charged particle detector that can measure with high temporal resolution (1 nanosecond or less) and has little deterioration due to changes over time. Another object of the present invention is to provide a high-performance detection device including such a charged particle detector.
[0009]
[Means for Solving the Problems]
As means for solving the above-described problems, a gallium-doped zinc oxide film formed by sputtering a mixture of zinc oxide and gallium oxide is used for the charged particle detector. Since the gallium-doped zinc oxide film is an inorganic scintillator with a very fast response time, a high count rate (10 ^Five Measurement per unit / second) and high time resolution (1 nanosecond or less). Further, a binder required for firing the powder is unnecessary, and high heat resistance (200 ° C. to 600 ° C.) and resistance to changes with time can be secured. Moreover, it was set as the detection apparatus provided with such a charged particle detector. Details thereof will be described in the embodiment.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described in detail with reference to the drawings.
First, the structure of the charged particle detector in this embodiment is demonstrated using FIG. A specific application of charged particle detection will be described later with an example.
[0011]
The charged particle detector 1 of the present embodiment shown in FIG. 1 uses a gallium-doped zinc oxide film 4 formed on a glass substrate 3 by sputtering film formation processing for a detection element 2 containing a scintillation substance that detects charged particles. It is characterized by that. An aluminum light-shielding film 5 is formed on the detection element 2 by sputtering film deposition or vapor deposition so as to cover the gallium-doped zinc oxide film 4 and the glass substrate 3, and the back surface of the glass substrate 3, that is, gallium-doped zinc oxide. A glass window 6a for the photocathode of the photomultiplier tube 6 is in close contact with the surface 3a opposite to the surface on which the film 4 is formed using optical grease or optical cement. The side surface of the glass substrate 3 and the photomultiplier tube 6 are covered with a light shielding container 7 so that stray light from the outside does not enter. A terminal 8 for applying a high voltage to the photomultiplier tube 6 and taking out a signal from the photomultiplier tube 6 is provided on the bottom surface of the light shielding container 7.
[0012]
Here, in the charged particle detector 1, the charged particles pass through the aluminum light-shielding film 5 and enter the gallium-doped zinc oxide film 4. The portion of the gallium-doped zinc oxide film 4 where the charged particles are incident emits fluorescence, and this fluorescence reaches the photocathode (not shown) of the photomultiplier tube 6 through the glass substrate 3 and the photocathode glass window 6a. The fluorescence that has reached the photocathode is converted into electrons on the photocathode, and the electrons are amplified in the photomultiplier tube 6 to become an electric signal. When the electric signal is taken out through the terminal 7 and the peak value of the signal is measured, the energy of the charged particles can be measured.
[0013]
A method for manufacturing the detection element 2 used for detecting charged particles will be described.
First, as shown in FIG. 2A, a mask M for limiting a region for film formation on the glass substrate 3 is applied. Here, an example in which the charged particle detection position is divided into a plurality of regions is shown, but the presence or absence of the mask M and the shape and arrangement of the mask M can be selected as appropriate. Subsequently, as shown in FIG. 2B, a gallium-added zinc oxide film 4 is formed on the glass substrate 3 by sputtering film formation so as to have the same thickness as the range of the charged particles to be measured. For example, when used as a detector for charged particles having an energy of about 3.5 MeV, it is necessary to form a film with a thickness corresponding to the range (up to 10 μm) of the gallium-doped zinc oxide film of charged particles of 3.5 MeV. There is.
[0014]
As shown in FIG. 2C, when the gallium-doped zinc oxide film 4 is formed and aluminum is deposited on the glass substrate 3 from which the mask M is removed, the aluminum light-shielding film 5 is formed, thereby forming the detection element 2 ( (See FIGS. 2D and 2E). Since the detection element 2 uses a lattice-like mask M, the detection region is divided at a predetermined interval, and has a two-dimensional array shape. Therefore, the position of the incident charged particle can be identified, and for example, the flight direction of the charged particle can be estimated or the generation position can be estimated. The aluminum light-shielding film 5 needs to be sufficiently thinner than the thickness corresponding to the range of the charged particles in the aluminum film when the charged particles to be detected enter the same aluminum film with the energy. In addition, since it is used as a light shielding film, it needs to have sufficient light shielding performance. Therefore, in order to use it for light shielding of charged particles having an energy of about 3.5 MeV, the thickness needs to be about 1 to 2 μm. Even when the aluminum light-shielding film 5 is formed by vapor deposition, it is necessary to have the same thickness.
[0015]
Here, examples of the sputtering film forming method used in the present embodiment include a first method performed by the apparatus configuration shown in FIG. 3 and a second method performed by the apparatus configuration shown in FIG.
[0016]
The first method is performed by the sputtering apparatus 11 shown in FIG. This sputtering apparatus 11 has a grounded anode 12 and a cathode 14 connected to a high-frequency power source 13, holds the glass substrate 3 on the anode 12 side, and arranges a sputtering target 15 on the cathode 14 side. It is configured. The target 15 may be gallium oxide or zinc oxide added with gallium, or may be a gallium oxide target or a zinc oxide target. When a high frequency voltage is applied to the cathode 14 after filling the space between the anode 12 and the cathode 14 with an inert gas (pressure 0.1 to 10 Pa), a glow discharge plasma of an inert gas is generated between the electrodes 12 and 14. The inert gas is ionized. Ionized inert gas, that is, inert gas ions, is incident on the target 15 in accordance with the electric field generated by the anode 12 and the cathode 14 and the magnetic field generated by the electromagnet 16, and the target 15 is sputtered. The constituent material of the sputtered target 15 is deposited on the glass substrate 3 and the mask M held by the anode 12 according to the electric field generated by the anode 12 and the cathode 14 and the magnetic field generated by the electromagnet 16. When the gallium-doped zinc oxide is deposited to a thickness corresponding to the predetermined film thickness as described above, the voltage application is terminated and the glass substrate 3 is taken out.
[0017]
The second method is performed by the sputtering apparatus 17 shown in FIG. This sputtering apparatus 17 has a grounded anode 12 and a cathode 14 connected to a DC power source 18. A plurality of electromagnets 19 are arranged on the cathode 14 at intervals so that different poles are adjacent to each other. Yes. A gap between the anode 12 and the cathode 14 is filled with an inert gas (pressure 0.2 to 1.5 Pa), and a voltage is applied to the cathode 14 to generate a glow discharge plasma of an inert gas between the electrodes 12 and 14. . As a result, the ionized inert gas is incident on the target 15 similar to the above according to the electric field created by the anode 12 and the cathode 14 and the magnetic field created by the electromagnet 19 to sputter the target material. The sputtered target material is deposited on the glass substrate 3 and the mask M installed on the anode 12 according to the electric field created by the anode 12 and the cathode 14 and the magnetic field created by the electromagnet 19. When the gallium-doped zinc oxide is deposited to a thickness corresponding to the predetermined film thickness as described above, the voltage application is terminated and the glass substrate 3 is taken out.
[0018]
Here, in both the first method and the second method, it is desirable to perform sputtering in an inert gas atmosphere or an oxygen gas atmosphere. This is to prevent the composition of the gallium-doped zinc oxide film 4 from changing due to reaction with the atmospheric gas during sputtering. In particular, the oxygen gas atmosphere is used to prevent the oxygen element amount from being insufficient. Further, the formation process of the gallium-doped zinc oxide film 4 and the aluminum light-shielding film 5 may be performed at a high temperature of 200 ° C. or higher, preferably in the range of 200 ° C. to 600 ° C. This is because a film having high thermal stability can be obtained and the deposition rate and film density of the film can be improved.
[0019]
The charged particle detector may be configured to include a plurality of photomultiplier tubes 6 as shown in FIG. 5, FIG. 6, or FIG.
A charged particle detector 21 shown in FIG. 5 includes a detection element 22 obtained by sputtering a gallium-doped zinc oxide film 4 on a single glass substrate 3 and a film formation of each gallium-doped zinc oxide film 4. A plurality of photomultiplier tubes 6 adhered to the glass substrate 3 with optical grease or the like corresponding to the positions are provided. The sputtering film forming process is performed by the first method or the second method described above, and each gallium-added zinc oxide film 4 is formed in a two-dimensional array as shown in FIG. The aluminum light shielding film 5 and the light shielding container 27 prevent stray light from entering the photomultiplier tube 6 as described above. Such a charged particle detector 21 can increase the detection area of the charged particles. The charged particle detector 21 has a configuration in which a flange mounting metal frame 28a that facilitates mounting to a vacuum vessel (not shown) is joined in advance. The flange-mounting metal frame 28a is joined so that the vacuum is not broken from the joint portion between the flange-mounting metal frame 28a and the glass substrate 3 when attached to the vacuum vessel.
[0020]
A charged particle detector 31 shown in FIG. 6 has a detection element 32 in which a plurality of gallium-doped zinc oxide films 4 and an aluminum light-shielding film 5 are formed on a glass substrate 3 in a two-dimensional array. In this detection element 32, each gallium-doped zinc oxide film 4 is formed at a narrower interval than the photomultiplier tube 6. For this reason, a light guide 33 is mounted between the glass substrate 3 and the photomultiplier tube 6. The light guide 33 is composed of one or a plurality of optical fibers, and the end surface of one end 33a is bonded to the surface 3a opposite to the film forming side of the glass substrate 3 with optical grease, optical cement, or the like, and the other end 33b The end face is bonded to the photocathode glass window 6a of the photomultiplier tube 6 with optical grease, optical cement or the like. Similarly to the above, the photomultiplier tube 6 is covered with the light shielding container 37, but it is desirable that the side surface from the one end 33a to the other end 33b of the light guide 33 is subjected to light shielding processing. In such a charged particle detector 31, even if the size of the photocathode glass window 6 a of the photomultiplier tube 6 is sufficiently larger than that of the gallium-doped zinc oxide film 4 by using the light guide 33. The fluorescence generated in the gallium-doped zinc oxide film 4 can be efficiently carried to the photomultiplier tube 6. It is also useful when it is desired to investigate the detection position of charged particles in detail. The charged particle detector 31 and the charged particle detector 1 in FIG. 1 may be configured to include a flange mounting metal frame 28a as shown in FIG.
[0021]
The charged particle detector 41 of FIG. 7 includes a detection element 42 using a glass substrate 43 having a curved surface, and a gallium-added oxide film 4 and an aluminum light-shielding film 5 formed by sputtering film formation inside the curved surface. For each of the two-dimensional array of gallium-doped zinc oxide films 4, a glass surface 46a for the photocathode of the photomultiplier tube 6 using optical grease, optical cement, or the like on the surface 43a of the glass substrate 43 opposite to the film formation surface. The side surfaces of the individual photomultiplier tubes 6 are shielded from light so as to minimize the incidence of fluorescence entering the other photomultiplier tubes 6. In addition, a flange mounting metal frame 28a attached to the vacuum vessel is bonded in advance to the end face of the glass substrate 43 or the light shielding vessel 47. The charged particle detector 41 arranges the gallium-doped zinc oxide films 4 in a two-dimensional array along a curved surface so that when charged particles are generated from a substantially constant point, the distances from the generation point become equal. A gallium-doped zinc oxide film 4 can be provided. In this case, the curvature of the glass substrate 43 is determined by the generation position of the charged particles and the distance from the charged particle, but it may be hemispherical. In FIG. 7, the photomultiplier tubes 6 are arranged radially with respect to the curved surface, but may be arranged in parallel by using the light guide as described above.
[0022]
Next, as an example of applications of the charged particle detectors 1, 21, 31, and 41, a case where the charged particle detectors are used together with a neutron generator will be described with reference to FIG. Furthermore, the case where a charged particle detector and a neutron generator are applied to an explosive detection device will be described with reference to FIGS. In the following, the charged particle detector 21 shown in FIG. 5 is assumed, but other forms of charged particle detector (for example, the charged particle detector 1, the charged particle detector 31, or the charged particle detector 41). ).
[0023]
The charged particle detector 21 shown in FIG. 8 is attached to a neutron generator 51 that generates neutrons, and identifies the flight direction of neutrons by detecting charged particles emitted with a phase difference of about 180 ° with respect to the neutrons. Used to do. The direction of neutron flight can be determined by detecting charged particles because the flight direction of charged particles can be determined by identifying the generation and detection positions of charged particles. This is because the flight direction can be identified.
[0024]
This neutron generator 51 has 10 ^-1 It is maintained in a reduced pressure atmosphere of Pa or less, and generates fast neutrons (hereinafter simply referred to as neutrons) and charged particles (for example, α rays which are He nuclei) by irradiation with an ion beam. An ion source 53 that ionizes deuterium is provided, and the target 55 is irradiated with a deuterium ion beam extracted from the ion source 53 by the acceleration electrode 54. The target 55 is made of a hydrogen storage alloy in which tritium is occluded. When the target 55 is irradiated with a deuterium ion beam, charged particles and neutrons are generated by a fusion reaction (DT reaction) between deuterium and tritium. The generated charged particles and neutrons are each emitted with a phase difference of approximately 180 ° around the irradiation position. Neutrons are emitted through the side wall 52b opposite to the charged particle detector 21 with the target 55 as the center. On the other hand, charged particles emitted from the surface of the target 55 reach the charged particle detector 21 through the opening 52 a facing the target 55, pass through the aluminum light-shielding film 5, and enter the gallium-doped zinc oxide film 4. The gallium-doped zinc oxide film 4 on which the charged particles are incident emits fluorescence, and this fluorescence reaches the photocathode of the photomultiplier tube 6 through the glass substrate 3 and the photocathode glass window 6a (see FIG. 6). The fluorescence that has reached the photocathode is converted into electrons on the photocathode, and the electrons are amplified in the photomultiplier tube 6 to become an electric signal. The electric signal is taken out through the insulating terminal 8 and the peak value of the signal is measured, whereby the energy of the α ray can be measured. The neutron generator 51 may have a device configuration that generates charged particles and neutrons by a fusion reaction (DD reaction) between heavy waters.
[0025]
A process of manufacturing the neutron generator 51 to which the charged particle detector 21 of the present embodiment is attached will be briefly described.
In the charged particle detector 21, the flange mounting metal frame 28 a is attached to the flange mounting metal frame 28 b of the opening 52 a of the neutron generating tube 51 by welding or tightening with bolts. As described above, the inside of the neutron generating tube 52 is 10%. ^-1 Since it is necessary to set it to Pa or less, evacuation and outgassing are performed using the flange-mounting metal frames 28a and 28b and the glass substrate 3 as openings. This gas extraction is performed by heating the neutron generating tube 52 to a predetermined temperature (for example, 200 ° C.). At this time, the gallium-doped zinc oxide film 4 on the glass substrate 3 is also heated. However, since the gallium-doped zinc oxide film 4 of the present embodiment does not contain a binder or the like, there is no deterioration due to heating. Since the photomultiplier tube 6 generally has a low heat-resistant temperature, it is desirable to remove it from the glass substrate 3 while the neutron generator tube 52 is heated.
[0026]
Thus, if the charged particle detector 21 of this embodiment is attached to the neutron generator 51, it can endure the high heat at the time of manufacture. Furthermore, the flight direction of neutrons can be specified by the gallium-doped zinc oxide film 4 arranged in an array.
[0027]
Next, an example in which the charged particle detector 21 and the neutron generator 51 are applied to an explosive detection device will be described.
[0028]
The explosive detection device 61 shown in FIG. 9 irradiates the inspection object W with neutrons, detects γ rays generated isotropically therefrom, and the element of the substance irradiated with neutrons from the energy value of the γ rays Is identified. The configuration includes a charged particle detector 21, a charged particle signal processing device 62 that processes the detection signal, a neutron generator 51, a γ-ray detector 63 that detects γ-rays, and a γ-ray that processes the detection signal. A signal processing device 64, a data processing device 65 that processes data output from the charged particle signal processing device 62 and the γ-ray signal processing device 64, and an output device 66 that displays the processing results, are not shown in the figure. Integrated and controlled by the device. 9 includes a position / shape measuring device 68 that measures the position, size, and shape of the inspection object on the conveyor 67 in advance before irradiating neutrons. The position / shape measuring device 68 is not an essential component of the explosive detection device 61, but the following description will be made assuming that the position / shape measuring device 68 includes the position / shape measuring device 68.
[0029]
The charged particle signal processing device 62 generates an analog signal (charged particle peak value signal) indicating the wave height proportional to the energy of the charged particles and the detection position from the signal output from the charged particle detector 21. Further, a digital signal (charged particle detection signal) is generated simultaneously with the time when the charged particles are detected or with a certain temporal relationship. The charged particle detection signal informs the timing when the charged particles are detected.
[0030]
The γ-ray signal processing device 64 generates an analog signal (γ-ray peak value signal) having a wave height proportional to the energy of γ-rays from the signal input from the γ-ray detector 63. Furthermore, a digital signal (γ-ray detection signal) that is generated at the same time as the time when the γ-ray is detected or having a certain temporal relationship is generated. The γ-ray detection signal informs the timing when the γ-ray is detected, and is used to specify the generation position of the γ-ray by matching the charged particle and the detection timing in later processing.
[0031]
The position / shape measuring device 68 includes a measuring device 68a including an X-ray transmission device, an X-ray CT device, or a laser displacement measuring device, and a measurement signal processing device 68b that performs signal processing, and a conveyor 67 for the inspection object W. The upper position and dimensions / shape are output as three-dimensional position data. In order to efficiently acquire the three-dimensional position data, the radiation source and the corresponding detector are arranged so that measurement can be performed from at least two directions on a surface substantially orthogonal to the conveyance direction of the inspection target W. It is desirable.
[0032]
The data processing device 65 specifies the generation position of the γ-ray from the charged particle detection signal and the γ-ray detection signal, calculates the energy value of the γ-ray from the γ-ray peak value signal, and constitutes the constituent element of the inspection object W from the energy value. Is identified. Thus, since this explosives detection apparatus 61 can specify the generation | occurrence | production position of a gamma ray, it can specify the place where the structural element of the test target object W to be identified exists. Therefore, the distribution of constituent elements and the like can be displayed three-dimensionally in accordance with the shape of the inspection object W. Also, the abundance ratio is calculated by paying attention to a specific element, and matching with the elemental composition of explosives held as a reference is attempted. If it does in this way, it will become easy to judge whether explosives are contained in inspection subject W. Here, since the position / shape measuring device 68 is provided, the position and shape of the inspection object W are divided into γ-ray detection times for which data processing should be performed on each neutron according to the measurement result, and such The energy value is calculated only from the γ-ray peak value signal detected in the detection time zone. In this way, the data processing amount can be reduced.
[0033]
Moreover, like the explosives detection apparatus 71 shown in FIG. 10, the X-ray generator and X-ray measuring apparatus for acquiring the density distribution image of the test object W, and the above-described neutron generator 51 and γ-ray detector 63 may be arranged in a cross section perpendicular to the conveyance direction of the inspection object W (a method perpendicular to the paper surface in FIG. 10). This explosives detection device 71 is integrated and controlled by a control device (not shown), and an X-ray generator 73 and X-ray detector arrays 74 and 75 are arranged on the same cross section of a device wall 72 that also serves as a radiation shield. Similarly, a plurality of neutron generators 51 and γ-ray detectors 63 are arranged. Since the γ-ray energy to be measured is several MeV or more, while the X-ray energy is several hundred keV or less, the X-ray detector arrays 74 and 75 do not measure γ-rays. On the other hand, in order to detect X-rays, the γ-ray detector 63 is provided with an X-ray shield 76 made of lead or the like, and improves the quality of the γ-ray signal by shielding the X-rays.
[0034]
An X-ray transmission image can be obtained by detecting the X-rays generated from the X-ray generator 73 and transmitted through the baggage with the X-ray detector array 74 or 75. The X-ray detector arrays 74 and 75 are one-dimensional arrays, and a two-dimensional transmission image is obtained by moving the inspection object W. Further, by operating the X-ray detector arrays 74 and 75 simultaneously, transmission images in two directions can be obtained simultaneously.
[0035]
The processing system in the explosive detection device 71 is the same as the explosive detection device 61 described above, the signal from the charged particle detector 21 is processed by the charged particle signal processing device 62, and the signal from the γ-ray detector 63 is processed. Processing is performed by the γ-ray signal processing device 64. Further, the measurement signal processing device 68b processes signals from the X-ray detector arrays 74 and 75 and performs signal processing for creating a transmission X-ray image of the inspection object W. Then, the data processor 65 performs calculation of γ-ray energy spectrum and image processing, and displays them on the output device 66. According to the explosive detection device 71, a transmission X-ray image and a neutron CT image can be obtained almost simultaneously by each device arranged in the same plane, so that the device can be miniaturized. In addition, explosives can be detected quickly.
[0036]
Thus, by providing the charged particle detector 21 of the present embodiment, the explosion detection devices 61 and 71 can specify the generation position of γ rays and improve the detection rate of explosives. it can. Further, since the charged particle detector 21 is excellent in time resolution and the like, the time required for detection can be shortened. As a result, it is possible to realize a high-speed inspection and a low false detection rate, which are requirements for luggage inspection at airports.
[0037]
The present invention is not limited to the above-described embodiment and can be widely applied.
For example, the metal frame 28a for flange attachment may be attached in advance to the glass substrate 3, and the gallium-added zinc oxide film 4 and the aluminum light-shielding film 5 may be formed in this state. The glass substrate 3 can be easily handled, and the sputtering apparatuses 11 and 17 can be easily attached to the anode 12.
Further, a photodiode may be used in place of the photomultiplier tube 6. It is possible to reduce the size of the apparatus.
Furthermore, the application of the charged particle detectors 1, 21, 31, and 41 is not limited to the explosives detection devices 61 and 71, and can be used for other detection devices and analysis devices.
[0038]
【The invention's effect】
According to the present invention, it is possible to obtain a charged particle detector having a high counting rate, temporal resolution, and heat resistance, and having high resistance against changes with time. Moreover, a high-performance detection device can be realized by providing such a charged particle detector.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a charged particle detector according to an embodiment of the present invention.
FIG. 2 is a conceptual diagram illustrating a manufacturing process of a detection element.
FIG. 3 is a schematic diagram showing an example of thin film formation.
FIG. 4 is a schematic diagram showing an example of thin film formation.
FIG. 5 is a diagram showing a configuration of a charged particle detector in the embodiment of the present invention.
FIG. 6 is a diagram showing a configuration of a charged particle detector in the embodiment of the present invention.
FIG. 7 is a diagram showing a configuration of a charged particle detector in the embodiment of the present invention.
FIG. 8 is a diagram showing a neutron generator and a charged particle detector.
FIG. 9 is a diagram illustrating a configuration of a detection device including a charged particle detector.
FIG. 10 is a diagram illustrating a configuration of a detection device including a charged particle detector.
[Explanation of symbols]
1, 21, 31, 41 Charged particle detector
3,43 glass substrate
4 Gallium-doped zinc oxide film
5 Aluminum light shielding film
6 Photomultiplier tubes
7, 27, 37, 47 Shading container
11, 17 Sputtering equipment
28a Metal frame for flange mounting
33 Light guide
51 Neutron generator
61, 71 Explosives detection device
63 γ-ray detector
65 Data processing device
66 Output device
68 Position / Shape Measuring Device
73 X-ray generator
74,75 X-ray detector array

Claims (15)

A gallium-doped zinc oxide film formed on a glass substrate or a glass substrate sandwiched between a glass substrate or a metal frame by sputtering a mixture of zinc oxide and gallium oxide, and the gallium-doped zinc oxide film and aluminum formed on the glass substrate A charged particle detector comprising a film. The charged particle detector according to claim 1, wherein the gallium-doped zinc oxide film is formed in an array having a predetermined gap. 2. A glass surface covering a photoelectric surface of a photomultiplier tube or a photodiode is closely attached to a surface of the glass substrate opposite to the surface on which the gallium-doped zinc oxide film is formed. Or the charged particle detector of Claim 2. The end face of the optical fiber is closely attached to the surface of the glass substrate opposite to the face on which the gallium-doped zinc oxide film is formed, and the other end face of the optical fiber is covered with the photomultiplier tube or the photocathode of the photodiode. The charged particle detector according to claim 1, wherein the charged particle detector is closely attached to a glass surface. The charged particle detector according to any one of claims 1 to 4, wherein the glass substrate has a curved surface, and the gallium-doped zinc oxide film is formed along the curved surface. 2. The charged particle detector according to claim 1, wherein the gallium-doped zinc oxide film has a thickness equivalent to a thickness corresponding to a range of charged particles to be detected in the gallium-doped oxide film. . The charged particle detector according to claim 1 or 6, wherein a thickness of the aluminum film is thinner than a thickness corresponding to a range of charged particles to be detected in the aluminum film. A method for producing a charged particle detector for detecting charged particles by utilizing a light emission phenomenon of a gallium-doped zinc oxide film caused by incident charged particles,
Sputtering a mixture of zinc oxide and gallium oxide to form a gallium-doped zinc oxide film on a glass substrate or a glass substrate sandwiched between metal frames;
Forming an aluminum film on the glass substrate after forming the gallium-doped zinc oxide film so as to cover the gallium-doped zinc oxide film;
A method for producing a charged particle detector, comprising: The method for producing a charged particle detector according to claim 8, wherein the aluminum film is formed by sputtering or vacuum deposition. The method for producing a charged particle detector according to claim 8, further comprising a step of forming a lattice mask on the glass substrate before forming the gallium-doped zinc oxide film. The charged particle detector according to claim 8, wherein in the step of forming the gallium-doped zinc oxide film on the glass substrate, sputtering is performed using ions of inert gas or oxygen ions. The charged particle detector according to claim 8, wherein the step of forming the gallium-doped zinc oxide film on the glass substrate is performed while maintaining the temperature of the glass substrate at 200 ° C. to 600 ° C. A charged particle detector according to any one of claims 1 to 7, a neutron generator for generating charged particles and neutrons, and generated when the generated neutrons irradiate an inspection object. A charged particle detector comprising a γ-ray detector for detecting γ-rays and configured to identify constituent elements of an inspection object based on a detection result of charged particles and a detection result of γ-rays A detection device comprising:   The detection apparatus with a charged particle detector according to claim 13, further comprising a measurement device that measures the position and shape of the inspection object before irradiating the inspection object with neutrons.   An X-ray apparatus for measuring the shape of the inspection object is provided, and the X-ray apparatus is disposed on the same plane as the neutron generator in a plane substantially perpendicular to the conveyance direction of the inspection object. A detection device comprising the charged particle detector according to claim 13.

Images