Alpha-ray spectrum measuring device

Abstract

It is miniaturized for portability, has improved resolution enabling high-precision discrimination and identification of alpha nuclides, and allows switching between measurements in air and vacuum. [Solution] The alpha-ray spectrum measuring device 100 comprises a detector 10 having an ion-implanted silicon sensor 12 with a window diameter of 30 mm or less, a sealing jig 20 that houses the alpha-ray source to be measured and can be attached to the tip of the detector 10, and a depressurization mechanism 30 that can reduce the pressure inside the sealing jig 20.

Description

Technical Field

[0001] The present invention relates to an α-ray spectrum measuring apparatus. Background Art

[0002] In recent years, targeted radionuclide therapy, particularly radiopharmaceuticals using α-emitting nuclides, has been expected for global clinical application. As medical radioisotopes, 226 produced from Ra 225 Ac, and 209 produced from Bi 211 At, etc., are produced, discriminated and utilized.

[0003] In the production of radionuclides using nuclear reactors or accelerators, radionuclides produced by raw material quantities and irradiation contain by-products in addition to the target nuclide. In order to sufficiently remove radioactive impurities that are such radionuclides, purity testing of radionuclides is extremely important. For example, in the production of 226 Ac from Ra 225 using a cyclotron, examples of main radioactive impurities include 226 Ac, 224 Ac, 226 and Ra.

[0004] Here, it is necessary to improve energy resolution to a degree that allows discrimination of nuclides such as 148 Gd, 237 Np, 241 Am, 244 and Cm, which have main energy peaks at 3.3 MeV, 4.8 MeV, 5.5 MeV, and 5.8 MeV.

[0005] Conventional α-ray spectrometers are structured such that an α sample is sampled, placed in a dedicated measuring instrument, and then measured. In addition, since the sampled sample is placed in a large vacuum container and measured in vacuum using a vacuum pump, the measuring instrument system becomes large and lacks portability. Prior Art Documents Non-Patent Literature

[0006] [Non-Patent Document 1] Mihei Y, Tani K, Ichonose J, Nagatsu K, Fukushi M, Kurihara O, Inoue K. Energy resolution improvement in simplified alpha spectroscopy for radionuclidic purity tests on 225Ac production floors, Radiation Protection Dosimetry, 2024, 200(15), 1443-1449 [Overview of the project] [Problems that the invention aims to solve]

[0007] This hybrid alpha-ray spectrum survey meter, capable of measuring alpha rays in both air and vacuum—something not possible with conventional methods—is needed to enable alpha-nuclide discrimination in clinical settings for nuclear medicine internal therapy using alpha rays and in facilities that manufacture alpha-nuclides.

[0008] This invention has been made in view of the above circumstances, and aims to achieve the objective of providing an alpha-ray spectrum measuring device that is miniaturized and portable, has improved resolution enabling high-precision discrimination and identification of alpha nuclides, and allows switching between measurements in air and vacuum. [Means for solving the problem]

[0009] (1) An alpha-ray spectrum measuring device according to one aspect of the present invention is A detector having an ion implantation type silicon sensor with a window diameter of 30 mm or less, A sealed jig that houses the alpha-ray source to be measured and can be attached to the tip of the detector, A depressurization mechanism capable of reducing the pressure inside the aforementioned sealing jig, Having This resolved the above issues. (2) The α-ray spectrum measuring apparatus according to the present invention, in the above (1), by switching the decompression mechanism, with respect to the α-ray source to be measured within the sealing jig and the detector, measurement in air in which the interior of the sealing jig is an air atmosphere, and measurement under reduced pressure in which the interior of the sealing jig is a reduced pressure (vacuum) atmosphere, can be selected, . (3) The α-ray spectrum measuring apparatus according to the present invention, in the above (1), has a collimator attachable to a tip end of the detector, . (4) The α-ray spectrum measuring apparatus according to the present invention, in the above (1), the decompression mechanism is either of a portable type or a stationary type, . (5) The α-ray spectrum measuring apparatus according to the present invention, in the above (1), a sealing mechanism is provided at a fitting portion between the tip end of the detector and the sealing jig, .

[0010] In the configuration described in the above (1), by including an ion-implanted silicon sensor of 1 inch with a window diameter of 30 mm or less, which is smaller than a conventional 2-inch sensor, for example, when the radiation source is 241 Am (5.5 MeV), the bias voltage is 35 V, and the incident angle in vacuum is 85° to 95°, detection sensitivity can be improved by using a sensor having an FWHM value of 42 keV or less in air and 22 keV or less in vacuum. Unlike the prior art, the detector is formed into a probe shape, which makes it possible to use a so-called 1-inch ion-implanted silicon detector with high resolution, enabling α-ray spectrum measurement in air, and the structure can be excellent in portability and high in versatility. This enables the structure to allow alpha ray spectrum measurement in air, have excellent portability, and high versatility. Furthermore, it enables high-precision discrimination of alpha nuclides, improves portability through miniaturization, and can be easily used in clinical settings of endoradionuclide therapy and nuclide production sites that manufacture alpha nuclides. Furthermore, while maintaining portability, the present invention can be used as a survey meter in an air atmosphere, and enables identification of contamination sites of alpha nuclides. In addition, by enabling measurement in a reduced-pressure atmosphere or a vacuum atmosphere, collecting an alpha nuclide sample from a contaminated site and placing the sample to be detected in a sealing jig, high-precision nuclide identification can be achieved. In other words, by attaching a tip sealing jig to the detector, the device can also have the same functions as conventional alpha ray spectrometers. This enables measurement in air and measurement in vacuum with the same device, allows the device to have both the functions of a survey meter and a spectrometer, and provides the remarkable effect of enabling one device to serve two purposes.

[0011] Here, as the pressure reduction mechanism, a stationary vacuum suction device having a suction hole arranged on a wall surface can be used in medical settings. Since the detector and the sealing jig are portable, the vacuum device can be connected to the sealing device at a required location and when required, to perform discrimination of alpha nuclides in vacuum. Alternatively, even when a stationary vacuum device is not available in a medical setting or the like, it is possible to easily reduce pressure or evacuate the inside of the sealing device and perform discrimination of alpha nuclides in vacuum. In addition, measurement in an atmospheric environment can be performed without connecting a pressure reduction mechanism, to detect alpha radiation sources in medical settings and the like. Alternatively, at an alpha nuclide production site or the like, a stationary vacuum device capable of achieving high vacuum can be connected to the sealing device to perform discrimination of alpha nuclides in vacuum. In addition, measurement in an atmospheric environment can be performed without connecting a pressure reduction mechanism, to detect alpha radiation sources at alpha nuclide production sites and the like. Moreover, switching between these modes can be easily performed simply by turning on or off the connected pressure reduction mechanism.

[0012] In the configuration described in (2) above, by simply connecting or not connecting a pressure reduction mechanism, or by turning the connected pressure reduction mechanism on or off, it is possible to select between measurement in air, where the sealed jig is in an air atmosphere, and measurement in a reduced pressure (vacuum) atmosphere, where the sealed jig is in a reduced pressure (vacuum) atmosphere. This makes it possible to perform measurements in air and in a vacuum with the same device, and it can combine the functions of a survey meter and a spectrometer, exhibiting the remarkable effect of being able to perform two functions with a single device.

[0013] In the configuration described in (3) above, by adding a collimator to the tip of the detector, the incident angle of alpha rays entering the sensor can be adjusted, enabling even higher resolution. Therefore, while maintaining improved portability, it is possible to provide a highly versatile device that can measure alpha rays in air and function as both a survey meter and a spectrometer.

[0014] In the configuration described in (4) above, it is possible to easily select between air measurement, where the sealed jig is in an air atmosphere, and reduced-pressure measurement, where the sealed jig is in a reduced-pressure (vacuum) atmosphere, and switch between these modes simply by turning the connected reduced-pressure mechanism on and off. Furthermore, as a decompression mechanism, a stationary vacuum device with suction holes on the wall surface can be used in medical settings. Since the detector and sealing jig are portable, the vacuum device can be connected to the sealing device at the required location and time to perform alpha nuclide discrimination in a vacuum. Alternatively, even if a stationary vacuum device is not available in a medical setting, the inside of the sealing device can be simply decompressed or vacuumed to perform alpha nuclide discrimination in a vacuum. It is also possible to perform measurements in an atmospheric environment without connecting a decompression mechanism to detect alpha radiation sources in medical settings. Alternatively, at alpha-nuclide production sites, a stationary vacuum pump capable of achieving a high vacuum can be connected to a sealed device to perform discrimination of alpha-nuclides in a vacuum. Furthermore, measurements can be performed in an atmospheric environment without connecting a depressurization mechanism to detect alpha-ray sources at alpha-nuclide production sites.

[0015] In the configuration described in (5) above, when the inside of the sealing jig is depressurized by the depressurization mechanism, the detector is pressed against the sealing jig by atmospheric pressure, and the sealing mechanism can improve the degree of sealing between the sealing jig and the detector, with respect to the inside of the sealing jig. In this case, a sealing mechanism such as an O-ring can also be provided so as to be crushed between the sealing jig and the detector pressed against the sealing jig. This allows for the extraction of air and dust contained within the sealed fixture, reducing the factors that interfere with alpha radiation emitted from the alpha source and improving detection accuracy. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide an alpha-ray spectrum measuring device that is miniaturized and portable, has improved resolution enabling high-precision discrimination and identification of alpha nuclides, and allows switching between measurements in air and vacuum. [Brief explanation of the drawing]

[0017] [Figure 1] This is a schematic diagram showing a first embodiment of the alpha-ray spectrum measuring device according to the present invention. [Figure 2] This is a plan view showing a sealing jig in the first embodiment of the alpha-ray spectrum measuring device according to the present invention. [Figure 3] This is a plan view showing a collimator in a second embodiment of the alpha-ray spectrum measuring device according to the present invention. [Figure 4] This is a side view showing the detector in a second embodiment of the alpha-ray spectrum measuring device according to the present invention. [Figure 5] This is a plan view showing another example of a collimator in a second embodiment of the alpha-ray spectrum measuring device according to the present invention. [Figure 6] This is a plan view showing another example of a collimator in a second embodiment of the alpha-ray spectrum measuring device according to the present invention. [Figure 7]This is a schematic diagram showing a partial cross-sectional view of a third embodiment of the alpha-ray spectrum measuring device according to the present invention. [Figure 8] This is a schematic side view showing the detector in the fourth embodiment of the alpha-ray spectrum measuring device according to the present invention. [Figure 9] This graph shows an example of detection using the alpha-ray spectrum measuring device according to the present invention. [Figure 10] This graph shows an example of detection using the alpha-ray spectrum measuring device according to the present invention. [Figure 11] This graph shows an example of detection using the alpha-ray spectrum measuring device according to the present invention. [Figure 12] This graph shows an example of detection using the alpha-ray spectrum measuring device according to the present invention. [Figure 13] This graph shows an example of detection using the alpha-ray spectrum measuring device according to the present invention. [Figure 14] This graph shows an example of detection using the alpha-ray spectrum measuring device according to the present invention. [Figure 15] This graph shows examples of detections using an alpha-ray spectrum analyzer. [Modes for carrying out the invention]

[0018] Hereinafter, a first embodiment of the alpha-ray spectrum measuring device according to the present invention will be described with reference to the drawings. Figure 1 is a schematic cross-sectional view of the maintenance section of the alpha-ray spectrum measuring device according to this embodiment. Figure 2 is a plan view showing the sealing jig of the alpha-ray spectrum measuring device according to this embodiment. In the figures, reference numeral 100 denotes the alpha-ray spectrum measuring device.

[0019] As shown in Figure 1, the alpha-ray spectrum measuring device 100 according to this embodiment includes a detector 10, a sealing jig 20, a depressurization mechanism 30, and a control unit 40. The detector 10 includes a probe portion 11, a tip surface 11a, an ion implantation type silicon sensor (sensor) 12, and an enlarged diameter portion 13.

[0020] The probe portion 11 has a roughly cylindrical outer shape. An ion-implanted silicon sensor (sensor) 12 for detecting alpha rays is positioned at the tip of the probe portion 11. The probe portion 11 is connected to the control unit 40 via wiring 41 from its rear end. An enlarged diameter portion 13 with an enlarged circumferential surface is formed at the tip of the probe portion 11. The end face of the probe portion 11, the tip surface 11a, is flat.

[0021] Sensor 12 employs an ion-implanted silicon semiconductor detection mechanism. Sensor 12 is exposed on the tip surface 11a of the probe portion 11. The exposed surface of sensor 12 is the alpha-ray detection surface. Sensor 12 can detect alpha rays incident on its detection surface and detect the energy of the alpha rays. The detection surface of sensor 12 has a planar shape. The detection surface of sensor 12 intersects or is perpendicular to the axial direction of the probe portion 11. The detection surface of sensor 12 is recessed in the axial direction compared to the tip surface 11a. The diameter of the detection surface of sensor 12 can be approximately 1 inch or less. The detection surface of sensor 12 is sometimes referred to as the incident window. The diameter of the detection surface of sensor 12 is sometimes referred to as the window diameter. Here, the statement that the diameter of the detection surface of sensor 12 is 1 inch or less refers to the size of sensor 12, but at the same time, it indicates the detection accuracy.

[0022] Sensor 12 can have a detection surface diameter dimension, i.e., a window diameter of 30 mm or less. For example, if the window diameter of sensor 12 is 28 mm, the radiation source is 241 With an Am (5.5 MeV), a bias voltage of 35V, and an incidence angle of 85° to 95° in a vacuum, the FWHM value can be 42 keV or less in air and 22 keV or less in a vacuum. Alternatively, the sensor 12 may have a window diameter of 22 mm and a radiation source 241 With an Am (5.5 MeV), a bias voltage of 35V, and an incidence angle of 85° to 95° in vacuum, the FWHM value can be 38 keV or less in air and 18 keV or less in vacuum.

[0023] The sensor 12 has an entrance window covered with aluminum foil to block visible light and the like. The output signal from the sensor 12 is sent to the control unit 40 via a signal processing unit (not shown) located in the probe unit 11. Sensor 12 can be used to detect alpha particles in both air and a vacuum.

[0024] The outer circumferential surface of the enlarged diameter portion 13 is cylindrical. As will be described later, the tip of the enlarged diameter portion 13 is inserted into the sealing jig 20. The enlarged diameter portion 13 has approximately the same diameter dimension as the probe portion 11 in the axial direction. Alternatively, the outer circumferential diameter dimension of the enlarged diameter portion 13 may be slightly smaller than that of the tip surface 11a in the axial direction of the probe portion 11. A sealing mechanism 25 may be arranged on the outer circumferential surface of the enlarged diameter portion 13, as will be described later. Near the tip surface 11a, the outer circumferential surface of the enlarged diameter portion 13 may be inclined to narrow towards the end, or its corners may be rounded. The detector 10 can be fitted into the sealing jig 20. The detector 10 can be combined with the sealing jig 20.

[0025] As shown in Figures 1 and 2, the sealing jig 20 includes a cylindrical portion 21, an upper surface 21a, a bottom surface 22, an inner circumferential surface 22a, a stepped surface 23, an inner surface of the outer ring 24, a sealing mechanism 25, a pressure relief hole 26, and a flange portion 27. The sealing jig 20 can be formed from resin.

[0026] The cylindrical portion 21 has a bottomed cylindrical shape. When the detector 10 and the sealing jig 20 are combined, the cylindrical portion 21 is coaxial with the combined probe portion 11. The cylindrical portion 21 has a recess that opens to the upper surface 21a. The cylindrical portion 21 has a bottom surface 22. The bottom surface 22 has a circular contour when viewed from above. The bottom surface 22 is a plane along a plane perpendicular to the axis of the cylindrical portion 21. The bottom surface 22 is parallel to the top surface 21a. A stepped surface 23 is formed on the side wall of the cylindrical portion 21 on the radially outer side of the bottom surface 22. The bottom surface 22 is spaced apart from the top surface 21a in the axial direction of the assembled probe portion 11. The bottom surface 22 is spaced further apart from the top surface 21a than the stepped surface 23 in the axial direction of the assembled probe portion 11. The bottom surface 22 and the stepped surface 23 are connected by an inner circumferential surface 22a. The inner circumferential surface 22a is a cylindrical surface. The diameter of the inner circumferential surface 22a is smaller than the outer diameter of the tip surface 11a. The diameter of the inner circumferential surface 22a is equal to or slightly smaller than the inner diameter of the stepped surface 23. The inner circumferential surface 22a and the bottom surface 22 form a sample storage space.

[0027] The stepped surface 23 is located around the entire circumference of the bottom surface 22 in the circumferential direction. The stepped surface 23 is annular when viewed from above. The stepped surface 23 is arranged coaxially with the bottom surface 22. The stepped surface 23 is formed along a plane perpendicular to the axial direction of the cylindrical portion 21. The stepped surface 23 and the top surface 21a are parallel. The stepped surface 23 and the bottom surface 22 are parallel. The radial width dimension of the stepped surface 23 is equal around the entire circumference. The inner diameter dimension of the stepped surface 23 is equal to the diameter dimension of the inner circumferential surface 22a. The stepped surface 23 can contact the tip surface 11a around the entire circumference when the detector 10 and the sealing jig 20 are combined. The inner circumferential surface 22a and the stepped surface 23 form a sample storage space forming section that houses the object to be measured when alpha-ray detection is performed. An outer ring inner surface 24 is formed on the outer circumference of the stepped surface 23.

[0028] The inner surface 24 of the outer ring is cylindrical. The inner surface 24 of the outer ring is continuous in the axial direction from the stepped surface 23 to the upper surface 21a. The upper end of the inner surface 24 of the outer ring forms the opening of the cylindrical portion 21. The inner surface 24 of the outer ring is larger in diameter than the inner circumferential surface 22a. The diameter of the inner surface 24 of the outer ring is approximately equal to the total length in the axial direction. The diameter of the inner surface 24 of the outer ring is approximately equal to or slightly larger than the diameter of the enlarged diameter section 13. The axial dimension of the inner surface 24 of the outer ring is smaller than the dimension from the tip surface 11a of the enlarged diameter section 13 in the axial direction. The diameter of the inner surface 24 of the outer ring is larger than the diameter of the inner circumferential surface 22a. The inner surface 24 of the outer ring and the stepped surface 23 form a detector fixing and sealing section that positions and fixes the detector 10 to the sealing jig 20 and seals the inside of the cylindrical section 21. A sealing mechanism 25 is positioned on the inner surface 24 of the outer ring.

[0029] The sealing mechanism 25 can be an O-ring and an O-ring groove. The sealing mechanism 25 is formed around the entire circumference of the inner surface 24 of the outer ring. When the detector 10 and the sealing jig 20 are assembled, the sealing mechanism 25 contacts the entire circumference of the outer surface of the enlarged diameter portion 13. When the detector 10 and the sealing jig 20 are assembled, the sealing mechanism 25 seals the inside of the cylindrical portion 21 from the outside. When the inside of the cylindrical portion 21 is depressurized, the sealing mechanism 25 maintains a depressurized state that allows at least alpha radiation measurement. The sealing mechanism 25 is capable of maintaining the vacuum level inside the depressurized cylindrical portion 21.

[0030] The depressurization hole 26 penetrates the side wall of the cylindrical portion 21 in the radial direction. The depressurization hole 26 opens into the inner circumferential surface 22a. The depressurization hole 26 opens into the side circumferential surface of the cylindrical portion 21. In the axial direction, the depressurization hole 26 is located between the bottom surface 22 and the stepped surface 23. A depressurization mechanism 30 is connected to the depressurization hole 26. When the detector 10 and the sealing jig 20 are combined, the connected depressurization mechanism 30 can reduce the pressure inside the cylindrical portion 21.

[0031] The flange portion 27 is formed on the outer circumference of the lower end of the cylindrical portion 21. The diameter of the flange portion 27 is larger than the diameter of the cylindrical portion 21. The diameter of the flange portion 27 is such that the detector 10 can be stably erected when the detector 10 and the sealing jig 20 are combined. The flange portion 27 is parallel to the bottom surface 22. The lower surface of the flange portion 27 and the lower surface of the cylindrical portion 21 are flush. The upper surface of the flange portion 27 may also be flush with the bottom surface 22.

[0032] The pressure reducing mechanism 30 includes a cylinder 31, a piston 32, piping 33, and a valve 34. The pressure reducing mechanism 30 of this embodiment is portable. The pressure reducing mechanism 30 can reduce pressure by moving the piston 32 axially relative to the cylinder 31, thereby increasing the size of the internal space between the cylinder 31 and the piston 32.

[0033] The cylinder 31 is connected to the pressure relief port 26 via piping 33. A valve 34 is provided in piping 33. The size of the cylinder 31 and piston 32 is such that, when the detector 10 and the sealing jig 20 are combined, the required vacuum level can be achieved compared to the size of the internal space of the cylindrical portion 21 formed by the tip surface 11a, sensor 12, inner circumferential surface 22a, and bottom surface 22. Specifically, the cylinder 31 can have a capacity of about 500 mL. The pressure reduction mechanism 30 reduces the internal space of the cylindrical portion 21 using the cylinder 31 and piston 32, and then closes the valve 34 to maintain a reduced pressure state in the internal space of the cylindrical portion 21 that is sufficient to measure at least alpha rays.

[0034] The control unit 40 receives the signal detected by the sensor 12 via wiring 41 from the rear end of the probe unit 11. The control unit 40 can supply the necessary power to the sensor 12, etc. The control unit 40 can process the input signal. The control unit 40 may be equipped with a preamplifier, a multi-channel analyzer, etc. The control unit 40 can store the input signal. The control unit 40 can display the input signal. The wiring 41 is long enough to allow the signal from the sensor 12 to be input to the control unit 40 and to ensure the handling of the probe unit 11. Alternatively, the control unit 40 can be integrated with the probe unit 11 if the handling of the probe unit 11 is sufficient.

[0035] The alpha-ray spectrum measuring device 100 of this embodiment can switch between measuring in an atmospheric environment and measuring in a reduced-pressure environment, and can perform both. First, let's explain the measurement in air.

[0036] First, separate the detector 10 and the sealing jig 20. Place and fix the sealing jig 20 on a desk or the like. The sealing jig 20 should have the opening of the cylindrical part 21 facing upwards. At this time, the depressurization mechanism 30 does not need to be connected to or driven by the sealing jig 20. Next, the alpha-ray source to be measured is placed on the bottom surface 22. Then, the enlarged diameter section 13 is inserted into the opening of the cylindrical section 21. The detector 10 and the sealing jig 20 are assembled. The detector 10 has its probe section 11 erected. The probe section 11 and the cylindrical section 21 are coaxially positioned. The probe section 11 is pushed in until the stepped surface 23 contacts the tip surface 11a all around. In this case, the sealing mechanism 25 contacts the entire circumference of the outer surface of the enlarged diameter portion 13.

[0037] Next, the control unit 40 is operated to input the signal detected by the sensor 12 to the control unit 40 via the wiring 41 from the rear end of the probe unit 11. The detected data can then be processed as needed. In this case, since air is present in the internal space of the cylindrical portion 21, alpha particle detection is performed in the air.

[0038] Next, we will explain measurements in a vacuum or under reduced pressure.

[0039] Here, the decompression mechanism 30 is connected to the sealing jig 20. Similarly, after placing the alpha source to be measured on the bottom surface 22, the enlarged diameter portion 13 is inserted into the opening of the cylindrical portion 21. In this process, the sealing mechanism 25 contacts the entire circumference of the outer surface of the enlarged diameter portion 13. The internal space of the cylindrical portion 21 is sealed by the sealing mechanism 25. Next, the internal space of the cylindrical portion 21 is depressurized by the depressurization mechanism 30.

[0040] First, open valve 34. Next, the piston 32 is moved axially relative to the cylinder 31 to increase the internal size of the cylinder 31 and piston 32, thereby lowering the vacuum level inside the cylindrical portion 21. As a result, the air inside the cylindrical portion 21 and the dust contained in this air are drawn out through the decompression hole 26. This reduces the amount of fine particles, molecules, etc. that interfere with the alpha radiation being measured. In this state, valve 34 is closed. Furthermore, atmospheric pressure presses the detector 10 against the sealing jig 20, causing the tip surface 11a to be pressed against the stepped surface 23. In addition, the internal space of the cylindrical portion 21 is sealed by the sealing mechanism 25, and since no air flows in from the closed valve 34, the vacuum level inside the cylindrical portion 21 is maintained.

[0041] Next, the control unit 40 is operated to input the signal detected by the sensor 12 to the control unit 40 via the wiring 41 from the rear end of the probe unit 11. The detected data can then be processed as needed. In this case, since the internal space of the cylindrical portion 21 is under reduced pressure or in a vacuum, alpha particle detection is performed in a reduced pressure atmosphere or vacuum.

[0042] The alpha-ray spectrum measuring device 100 of this embodiment can be configured as a hybrid device that performs measurements in both an atmospheric and a reduced-pressure atmosphere using the same device, simply by switching whether or not the internal space of the cylindrical part 21 is depressurized by the depressurization mechanism 30. Furthermore, by using a detachable sealing jig 20 to which the depressurization mechanism 30 is connected, it is possible to perform measurements in both air and vacuum with a single detector 10. Furthermore, in this embodiment, since the pressure reduction mechanism 30 is a cylinder, high portability can be achieved.

[0043] Furthermore, by configuring the sensor 12 as described above, the alpha-ray resolution and nuclide discrimination ability can be improved. At the same time, by making the detector a compact and lightweight 1-inch type, its portability is enhanced, improving its versatility as a portable alpha-ray spectrum survey meter. Furthermore, the sealing jig 20 and the depressurization mechanism 30 enable measurements in a vacuum, allowing the device to combine functions similar to conventional alpha-ray spectrometers. This improves energy resolution and enables highly accurate discrimination of alpha nuclides. Therefore, it can combine the functions of both a survey meter and a spectrometer, offering the remarkable advantage of performing two roles in a single device. This makes it easily usable in both clinical settings for nuclear medicine internal therapy and in radionuclide manufacturing sites where alpha-nuclides are produced.

[0044] A second embodiment of the alpha-ray spectrum measuring device according to the present invention will be described below with reference to the drawings. Figure 3 is a plan view showing the collimator in the alpha-ray spectrum measuring device of this embodiment. Figure 4 is a side view showing the alpha-ray spectrum measuring device of this embodiment. In this embodiment, the only difference from the first embodiment described above is the collimator; other components corresponding to the first embodiment described above are denoted by the same reference numerals and their descriptions are omitted.

[0045] As shown in Figures 3 and 4, the alpha-ray spectrum measuring device 100 in this embodiment is equipped with a collimator 50 at the tip of the probe section 11. The collimator 50 is designed to increase the detection efficiency for radiation incident on the sensor 12 from a specific direction by restricting the path and incident area of ​​the radiation, thereby giving it directionality.

[0046] The collimator 50 covers the entire surface of the sensor 12 when viewed in the axial direction. The collimator 50 may also cover a portion of the tip surface 11a when viewed in the axial direction. The collimator 50 is spaced apart from the surface of the sensor 12. The periphery of the collimator 50 is connected to the tip surface 11a. The periphery of the collimator 50 does not come into contact with at least the stepped surface 23 when the detector 10 and the sealing jig 20 are assembled. The periphery of the collimator 50 may not come into contact with the inner circumferential surface 22a when the detector 10 and the sealing jig 20 are assembled.

[0047] The collimator 50 has multiple through-holes (cells) 51 formed by thin plate portions (foils) 52. All of the through-holes 51 have the same shape when viewed in the axial direction of the probe portion 11. The multiple through-holes 51 are arranged to cover at least the entire surface of the sensor 12 when viewed in the axial direction. Both the cell size and foil thickness are optimized for alpha-ray detection. The multiple through holes 51 are adjacent to each other when viewed in the axial direction of the probe portion 11. All of the through holes 51 are hexagonal when viewed in the axial direction of the probe portion 11. The thin plate portions 52 are all flat plates aligned with the normal to the sensor 12.

[0048] The collimator 50 can be made of, for example, a honeycomb-structured aluminum. The collimator 50 has an axial thickness dimension that is equal across its entire surface along the tip surface 11a. The collimator 50 has a thickness dimension such that it does not come into contact with the bottom surface 22 when the detector 10 and the sealing jig 20 are assembled. The collimator 50 has a thickness dimension such that it does not come into contact with the alpha-ray source on the bottom surface 22 when the detector 10 and the sealing jig 20 are assembled. Furthermore, the collimator 50 can be made detachable from the detector 10. The collimator 50 can also have a through hole 51 formed in the portion connected to the tip surface 11a.

[0049] In this embodiment, the same effects as those of the above-described embodiment can be achieved. Furthermore, in this embodiment, by adding a collimator 50 to the tip of the detector 10, even higher resolution is possible. In addition, by making the collimator disposable, contamination of the detector can be prevented.

[0050] In this embodiment, the collimator 50 can have a hexagonal cell structure as shown in Figure 3, as well as a square cell structure as shown in Figure 5, or a triangular cell structure as shown in Figure 6.

[0051] A third embodiment of the alpha-ray spectrum measuring device according to the present invention will be described below with reference to the drawings. Figure 7 is a schematic side view showing a partially cross-sectional view of the alpha-ray spectrum measuring apparatus in this embodiment. This embodiment differs from the first and second embodiments described above in respect to the sealing mechanism and the depressurization mechanism. Other corresponding components are denoted by the same reference numerals and their descriptions are omitted.

[0052] In this embodiment, as shown in Figure 7, a sealing mechanism 15 is provided at the tip of the probe portion 11. The sealing mechanism 15 is positioned on the tip surface 11a.

[0053] The sealing mechanism 15 can be an O-ring and an O-ring groove. The sealing mechanism 15 is formed around the entire circumference of the sensor 12 on the tip surface 11a. The sealing mechanism 15 contacts the entire circumference of the stepped surface 23 when the detector 10 and the sealing jig 20 are assembled. The sealing mechanism 15, together with the sealing mechanism 25, seals the inside of the cylindrical portion 21 from the outside when the detector 10 and the sealing jig 20 are assembled. The sealing mechanism 15 maintains a reduced pressure state that allows at least alpha radiation measurement when the inside of the cylindrical portion 21 is depressurized. The sealing mechanism 15 is capable of maintaining the vacuum level inside the depressurized cylindrical portion 21.

[0054] In this embodiment, the pressure reduction mechanism 30 includes a vacuum pump 35 instead of a cylinder 31. The vacuum pump 35, like the cylinder 31, is connected to the pressure relief port 26 via piping 33. A valve 34 is provided in the piping 33. The vacuum pump 35 is a stationary type. The vacuum pump 35 can employ an oil-sealed rotary pump or the like. The vacuum pump 35 can, for example, achieve a vacuum of approximately 1 to 20 Pa and have a capacity of 10 Pa.

[0055] In this embodiment, when measuring in a vacuum, the internal space of the cylindrical portion 21 is depressurized by the depressurization mechanism 30. In this case, if the vacuum pump 35 is kept running and the vacuum level inside the cylindrical portion 21 is kept low, the valve 34 does not need to be closed. Furthermore, the vacuum pump 35 allows the vacuum level inside the cylindrical portion 21 to be set lower than that of the cylinder 31. As a result, the detector 10 is pressed more firmly toward the sealing jig 20 by atmospheric pressure, and the sealing mechanism 15 on the tip surface 11a is pressed against the stepped surface 23, thereby improving the degree of sealing. In particular, the sealing mechanism 15 is pressed axially by atmospheric pressure, but since it is compressible in the same direction as this pressing, it becomes easier to maintain the sealed state. As a result, the internal space of the cylindrical section 21 is doubly sealed by the sealing mechanism 15 and the sealing mechanism 25, and since no air flows in from the piping 33, the vacuum level inside the cylindrical section 21 can be maintained at an even lower level.

[0056] In this embodiment, the same effects as those of the above-described embodiment can be achieved. Furthermore, in this embodiment, by using a stationary vacuum pump 35 and a double sealing mechanism 15 and sealing mechanism 25, the vacuum level can be further reduced, enabling higher resolution.

[0057] A fourth embodiment of the alpha-ray spectrum measuring device according to the present invention will be described below with reference to the drawings. Figure 7 is a schematic side view showing a partially cross-sectional view of the alpha-ray spectrum measuring apparatus in this embodiment. This embodiment differs from the first and second embodiments described above in terms of the sealing mechanism; other corresponding components are denoted by the same reference numerals and their descriptions are omitted.

[0058] In this embodiment, as shown in Figure 7, an upper flange portion 16 is provided on the outer circumference of the enlarged diameter portion 13. The upper flange portion 16 is formed on the outer circumference of the enlarged diameter portion 13. The diameter of the upper flange portion 16 is larger than the diameter of the inner surface 24 of the outer ring. The lower surface of the upper flange portion 16 can abut against the opening of the cylindrical portion 21. A sealing mechanism 17 is positioned on the lower surface of the upper flange portion 16.

[0059] The sealing mechanism 17 can be an O-ring and an O-ring groove. The sealing mechanism 17 is formed around the entire circumference of the lower surface of the upper flange portion 16. When the detector 10 and the sealing jig 20 are assembled, the sealing mechanism 17 is formed in a position facing the entire circumference around the opening of the upper surface 21a of the cylindrical portion 21. When the detector 10 and the sealing jig 20 are assembled, the sealing mechanism 17 contacts the entire circumference of the upper surface 21a. When the detector 10 and the sealing jig 20 are assembled, the sealing mechanism 15, together with the sealing mechanism 15 and the sealing mechanism 25, seals the inside of the cylindrical portion 21 from the outside. When the inside of the cylindrical portion 21 is depressurized, the sealing mechanism 17 maintains a depressurized state that allows at least alpha radiation measurement. The sealing mechanism 17 is capable of maintaining the vacuum level inside the depressurized cylindrical portion 21.

[0060] In this embodiment, the internal space of the cylindrical portion 21 is depressurized by the depressurization mechanism 30, and when the detector 10 is pressed toward the sealing jig 20 by atmospheric pressure, the sealing mechanism 17 of the upper flange portion 16 is pressed against the upper surface 21a, thereby improving the degree of sealing. In particular, since the sealing mechanism 17 can be compressed in the same direction as the detector 10, which is pressed axially by atmospheric pressure, moves toward the sealing jig 20, it becomes easier to maintain the sealed state. As a result, the internal space of the cylindrical section 21 is triple-sealed by the sealing mechanism 17, sealing mechanism 15, and sealing mechanism 25, and since no air flows in from the piping 33, the vacuum level inside the cylindrical section 21 can be maintained at a low level.

[0061] In this embodiment, the same effects as those of the above-described embodiment can be achieved. Furthermore, in this embodiment, the triple sealing mechanism 17, sealing mechanism 15, and sealing mechanism 25 further maintain the seal, enabling higher resolution.

[0062] Furthermore, in the present invention, it is also possible to individually select and combine each of the configurations in the above-described embodiments. For example, the sealing mechanisms 15 and 17 can be provided on the surface of the sealing jig 20. Alternatively, the sealing mechanism 25 can be provided on the surface of the detector 10. Furthermore, a collimator 50 can be used as appropriate if necessary. [Examples]

[0063] The following describes embodiments of the present invention.

[0064] Here, we will describe specific examples of tests performed using the alpha-ray spectrum measuring device in the present invention.

[0065] <Experimental Example 1> First, without using the collimator 50, various alpha-rays were identified using the alpha-ray spectrum measuring device shown in Figure 1. Here, we prepared the alpha radiation source as follows: Alpha-emitting source: As a mixed source of three radionuclides, 148 Gd, 241 Am, 244 We performed radionuclide discrimination on Cm. These are various types, each with its main energy peaks at 3.3 MeV, 5.5 MeV, and 5.8 MeV, respectively. The specifications at that time are shown below. Collimator 50, Thickness: 0mm (None) Distance between the surface of sensor 12 and the radiation source on the bottom surface 22: 4.3 mm Vacuum degree: 10Pa

[0066] The results are shown in Figure 9. The energy resolution at this time is, :FWHM at 115keV ( 241 (Am; 5.5 MeV) That was the case.

[0067] <Experimental Example 2> Similar radionuclides were prepared, and various alpha-ray emission types were identified using an alpha-ray spectral analyzer equipped with a collimator 50. The specifications at that time are shown below. Collimator 50, Thickness: 0mm (None) Distance between the surface of sensor 12 and the radiation source on the bottom surface 22: 12.3 mm Vacuum degree: 10Pa

[0068] The results are shown in Figure 10. The energy resolution at this time is, :60keV with FWHM ( 241 (Am; 5.5 MeV) That was the case.

[0069] <Experimental Example 3> Similar radionuclides were prepared, and various alpha-ray emission types were identified using an alpha-ray spectral analyzer equipped with a collimator 50. The specifications at that time are shown below. Collimator 50, Thickness: 0mm (None) Distance between the surface of sensor 12 and the radiation source on the bottom surface 22: 20.3 mm Vacuum degree: 10Pa

[0070] The results are shown in Figure 10. The energy resolution at this time is, : 50keV with FWHM ( 241 (Am; 5.5 MeV) That was the case.

[0071] <Experimental Example 4> Similar radionuclides were prepared, and various alpha-ray emission types were identified using an alpha-ray spectral analyzer equipped with a collimator 50. The specifications at that time are shown below. Collimator 50, Thickness: 0mm (None) Distance between the surface of sensor 12 and the radiation source on the bottom surface 22: 1.5 mm Vacuum level; in the atmosphere

[0072] The results are shown in Figure 12. The energy resolution at this time is, :FWHM at 184.5keV ( 241 (Am; 5.5 MeV) That was the case.

[0073] <Experimental Example 5> Similar radionuclides were prepared, and various alpha-ray emission types were identified using an alpha-ray spectral analyzer equipped with a collimator 50. The specifications at that time are shown below. Collimator 50, thickness: 3mm Distance between the surface of sensor 12 and the radiation source on the bottom surface 22: 6.6 mm Vacuum level; in the atmosphere

[0074] The results are shown in Figure 13. The energy resolution at this time is, :FWHM at 132keV ( 241 (Am; 5.5 MeV) That was the case.

[0075] <Experimental Example 6> Similar radionuclides were prepared, and various alpha-ray emission types were identified using an alpha-ray spectral analyzer equipped with a collimator 50. The specifications at that time are shown below. Collimator 50, thickness: 6 mm Distance between the surface of sensor 12 and the radiation source on the bottom surface 22: 6.8 mm Vacuum level; in the atmosphere

[0076] The results are shown in Figure 14. The energy resolution at this time is, :FWHM at 192.5keV ( 241 (Am; 5.5 MeV) That was the case.

[0077] <Experimental Example 7> Using similar radionuclides, and without the collimator 50, various alpha-ray spectra were identified using a conventional alpha-ray spectrum analyzer equipped with a stainless steel vacuum chamber. The specifications at that time are shown below. Sensor diameter: 50mm Collimator 50, Thickness: 0mm Distance between sensor surface and radiation source: 7 mm Vacuum degree: 10Pa

[0078] The results are shown in Figure 15. The energy resolution at this time is, : 50keV with FWHM ( 241 (Am; 5.5 MeV) That was the case.

[0079] The results shown in Figures 9 to 15 demonstrate that the alpha-ray spectrum measuring device of the present invention has improved resolution by miniaturizing the detector size to 1 inch, enabling highly accurate discrimination of alpha nuclides. The alpha-ray spectrum measuring device of the present invention can be used as a survey meter in air, allowing for the identification of alpha-nuclide contamination sites. Furthermore, it can be seen that highly accurate nuclide identification is possible by separating alpha-nuclide samples from the contaminated sites and placing the samples in a sealed jig. It is clear that this is a hybrid type that enables measurements in both air and vacuum with a single detector. The alpha-ray spectrum measuring device of the present invention can be applied to clinical settings for nuclear medicine internal therapy using alpha rays, as well as to the differentiation of generated alpha-nuclides in facilities that manufacture alpha-nuclides. Furthermore, by attaching a sealing jig to the tip of the detector, it is possible to combine the same functions as conventional alpha-ray spectrometers. Therefore, it can combine the functions of a survey meter and a spectrometer, demonstrating the remarkable advantage of being able to perform two roles in one device. [Explanation of symbols]

[0080] 100... Alpha-ray spectrum measuring device 10… Detector 12...Sensor 13... Expanded diameter part 15,17,25…Sealing mechanism 20... Sealing jig 30…Decompression mechanism 40... Control Unit

Claims

1. A detector having an ion implantation type silicon sensor with a window diameter of 30 mm or less, A sealed jig that houses the alpha-ray source to be measured and can be attached to the tip of the detector, A depressurization mechanism capable of reducing the pressure inside the aforementioned sealing jig, Having An alpha-ray spectrum measuring device characterized by the following features.

2. By switching the aforementioned pressure reduction mechanism, With respect to the alpha-ray source to be measured and the detector inside the sealed jig, Air measurement in which the sealed jig is placed in an air atmosphere, Measurement under reduced pressure, where the inside of the sealing jig is in a reduced pressure (vacuum) atmosphere, It is possible to select The alpha-ray spectrum measuring device according to claim 1, characterized in that it is a feature of the present invention.

3. The detector has a collimator that can be attached to the tip of the detector. The alpha-ray spectrum measuring device according to claim 1, characterized in that it is a feature of the present invention.

4. The pressure reduction mechanism is either portable or stationary. The alpha-ray spectrum measuring device according to claim 1, characterized in that it is a feature of the present invention.

5. A sealing mechanism is provided at the fitting portion between the tip of the detector and the sealing jig. The alpha-ray spectrum measuring device according to claim 1, characterized in that it is a feature of the present invention.

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