JP6238344B2 - Large solid angle gamma ray and beta ray simultaneous detection device - Google Patents

Description

  The present invention relates to a gamma ray / beta ray simultaneous detection apparatus, which relates to a detection apparatus assumed to be used for quick measurement of radioactive substances that do not require chemical separation as a use, and in particular, the measurement accuracy of gamma rays and beta rays is improved. The present invention relates to an apparatus for simultaneous detection of gamma rays and beta rays which is increased in size and reduced in size.

  The current measurement of radioactivity is widely carried out by gamma-ray spectrometry using a Ge (germanium) detector or the like. As a method for complementing it, the inventors have already proposed a rapid absolute measurement method of radioactive strontium which does not require chemical separation according to Patent Document 1 below. In that method, in addition to cesium 134 and cesium 137, the radioactivity of potassium 40 can be measured separately, and then radioactive strontium can be measured absolutely. The requirements for the main large solid angle gamma ray / beta ray simultaneous detection device (a combination device of a γ ray detector and a β ray detector) that has been conventionally considered as an apparatus for realizing the measurement method are classified as follows.

(1) Requirements for the following (a), (b), and (c) as a β-ray detector:
(A) Proportional counter containing a thin film sample (b) Liquid scintillation counter in which the sample is dropped and mixed (c) Plastic scintillator in which the sample is dropped and dried (2) Requirements for the following (d) and (e) as a γ-ray detector :
(D) Materials: scintillators such as thallium activated sodium iodide (NaI (Tl)), thallium activated cesium iodide (CsI (Tl)), and the like.
(E) Shape: (A) Cylindrical opposed type, (A) Well cylindrical type.
Among the combinations of detectors with these requirements, in general sample handling, β-ray detectors using (c) and γ-ray detection using either (d) or (e) It was thought that the instrument has applicability to measurement.

The requirements required for the combined gamma ray / beta ray simultaneous detection apparatus having the above applicability are mainly (1) requirements for beta ray detection characteristics, and (2) requirements for equipment layout.
(1) The requirements in the beta ray detection characteristics include the following (a), (b), and (c).
(A) In order to increase the detection efficiency of beta rays, the detection element (scintillator) is configured by two plate-like members so as to enclose the measurement sample, and both plate-like members are overlapped so as to sandwich the measurement sample. Place in state. The measurement sample is a solution obtained by dripping and drying the solution, and is composed of extremely thin flakes.
(B) In order to reduce individual noise of the light receiver and to receive weak light with high sensitivity, a light emission event by one beta ray is simultaneously measured by a plurality of light receivers.
(C) In order to obtain a weak light emission event with high sensitivity, the light receiver is placed close to the detection element (scintillator) and arranged with a large light receiving solid angle.

(2) The following (d) and (e) are requirements for equipment arrangement, that is, requirements for increasing both gamma ray detection efficiency and beta ray detection efficiency.
(D) To increase the detection efficiency of gamma rays, bring the gamma ray detector as close to the measurement sample as possible.
(E) In order to increase the detection efficiency of beta rays, the light emitting event of the detection element (scintillator) is arranged so as to be obtained with high sensitivity and low noise.

FIG. 2 is a schematic cross-sectional view of a beta ray scintillator showing a configuration in which a beta ray scintillator is disposed so as to surround a sample as a precondition for satisfying the requirements in the beta ray measurement.
The scintillator can be applied to a variety of inorganic and organic materials. However, for the beta ray of the present invention described later, a plastic scintillator is mainly used, and for the gamma ray, thallium activated sodium iodide (NaI (Tl)) is mainly used. In the following, each example will be described.
The beta ray plastic scintillator 2 includes a pair of upper beta ray plastic scintillators 3 and a lower beta ray plastic scintillator 5. A pair of upper beta-ray plastic scintillator 3 and lower beta-ray plastic scintillator 5 is sandwiched so as to enclose measurement sample 10 obtained by dropping and drying the solution, thereby forming beta-ray plastic scintillator assembly 7. An air layer is interposed between the pair of upper beta ray plastic scintillators 3 and the lower beta ray plastic scintillator 5.

  A pair of upper beta ray light receivers 12 and a lower beta ray light receiver 15 are disposed in contact with the opposite sides of the upper beta ray plastic scintillator 3 and the lower beta ray plastic scintillator 5 from the measurement sample 10. The beta ray receiver 11 includes a pair of beta ray receivers 12 and 15 and is configured to receive as much light as possible in the upper beta ray plastic scintillator 3 and the lower beta ray plastic scintillator 5. ing. When the beta ray generated in the measurement sample 10 imparts energy in the upper beta ray plastic scintillator 4 and the lower beta ray plastic scintillator 5, the organic light emitting substance fluoresces. This fluorescence is received by a pair of upper and lower beta ray receivers 12 and 15.

  Here, a conventional combination detection apparatus of a beta ray detector and a gamma ray detector based on the premise that a plastic scintillator is used will be described as type 1 and type 2 according to structure.

  The type 1 detection device includes a plastic scintillator and a surrounding light guide unit, a pair of cylindrical gamma ray detectors provided so as to sandwich the plastic scintillator, and a light guide unit exposed between the gamma ray detectors. It is a gamma ray and beta ray simultaneous detection device composed of a line light receiver.

FIG. 4 shows a type 1 simultaneous detection apparatus 100 for gamma rays and beta rays.
The detection apparatus 100 includes a sample 104 sandwiched between a pair of disc-shaped plastic scintillators 106, and a plate-shaped light guide 105 is provided in contact with an outer surface within the thickness of the pair of plate-shaped plastic scintillators 106. A pair of cylindrical gamma ray detectors so as to sandwich a pair of disk-shaped plastic scintillators 106 and a light guide portion 105 outside the pair of cylindrical gamma ray detectors 101, 101 between the end faces formed by circular planes. 101 is disposed, and beta light receivers 103 and 103 facing each other are provided in contact with the light guide portion 105 exposed between the pair of gamma ray detectors 101 and 101. Each component described above is attached and fixed to the detector arrangement jig 102 in order to maintain its position.

The type 1 detection device 100 can reduce individual noises by beta ray coincidence in the beta ray receivers 103 and 103 arranged opposite to each other.
Type 2 detector is a gamma ray detector that has a well-shaped cylindrical hole from one end, and a plastic scintillator and beta ray receiver are inserted into the well from the bottom. Device.

FIG. 5 shows a type 2 detection device 110.
In the detection apparatus 110, a sample 113 is sandwiched between a pair of disc-shaped plastic scintillators 114, and the sample 113 is sequentially formed from the bottom into the well of the gamma ray detector 111 in which a cylindrical hole 115 having a well structure is opened from one end. A pair of disc-shaped plastic scintillators 114 and a cylindrical beta ray receiver 112 are inserted and arranged.
The type 2 detection device 110 can increase the solid angle of light received by the plastic scintillator 114.
For these type 1 and type 2 detectors, the relationship with the required requirements will be examined.

  The type 1 detection device 100 in FIG. 4 has the merit of reducing individual noise by beta ray coincidence in the beta ray receivers 103 and 103 arranged opposite to each other, but the solid angle of light received by the plastic scintillators 106 and 106 that emit light. However, there are disadvantages that are disadvantageous for measuring weak light emission, that is, low-energy beta rays. In addition, there is a demerit that the entire apparatus becomes large.

  The type 2 detection device 110 in FIG. 5 has the advantage that the solid angle of light received by the plastic scintillators 114 and 114 is large, but has the disadvantage that the noise of the light receiver 112 itself cannot be separated from the low energy beta component. Further, although the sample 113 is sandwiched between two plastic scintillators 114, 114, there is a demerit that light emitted from the scintillator far from the light receiver 112 does not easily reach the light receiver 112.

Japanese Patent Application No. 2012-081420

  It is an object of the present invention to provide a large solid angle gamma ray / beta ray simultaneous detection device in which the solid angle of light received by a plastic scintillator is increased, the noise of each beta ray receiver is reduced, and the entire device is reduced. .

The present invention employs the following solutions in order to achieve the above object.
The large solid angle gamma ray / beta ray simultaneous detection apparatus of type 3 according to the present invention employs the following solution means in order to achieve the above object.
(1) A gamma ray scintillator is arranged around the through hole of the gamma ray detector case, and a beta ray receiver having a beta ray plastic scintillator is inserted into the through hole of the gamma ray detector.

Specifically, in the type 3 detection device, a through hole is formed on the side surface excluding the end face of the gamma ray detector, and a scintillator for gamma rays is arranged around the through hole, and the pair of beta rays is disposed in the through hole. A beta ray receiver assembly composed of a photodetector and a pair of beta ray plastic scintillators is inserted in close contact therewith.
In particular, the gamma ray scintillator is arranged around the through hole of the gamma ray detector, and the gamma ray solid angle with respect to the measurement sample in the beta ray receiver assembly inserted into the through hole is configured to have a wide angle excluding the through hole direction. The

(2) In (1), the through hole is provided on a side surface of the gamma ray detector so as to be orthogonal to the axis of the gamma ray detector.
Specifically, in the type 3 detection device, a cylindrical through hole is formed on the side surface excluding the end face of the gamma ray detector so as to be orthogonal to the axis of the gamma ray detector, and a beta ray receiver assembly is formed in the through hole. It is placed in close contact.

(3) In the above (1) or (2), the beta ray receiver is a pair of an upper beta ray receiver and a lower beta ray receiver, and the upper and lower beta ray plastic scintillators are provided A beta ray receiver assembly is sandwiched between a pair of beta ray receivers.
Specifically, at the time of detection, a measurement sample is sandwiched between a pair of upper and lower disk-shaped plastic scintillators for beta rays and assembled as a plastic scintillator assembly for beta rays, and a pair of cylindrical upper and lower beta scintillators is assembled. A beta ray receiver assembly is formed by connecting the beta ray receivers so as to sandwich the beta ray plastic scintillator assembly at each end face of the beta ray receivers, and a circular shape of a cylindrical gamma ray detector. A cylindrical through hole is formed on a side surface excluding the end face of the plane so as to be orthogonal to the axis of the gamma ray detector, and the pair of beta ray receivers and the pair of measurement samples are stored in the through hole in the detection. A beta ray receiver assembly made of a beta ray plastic scintillator is inserted and arranged so as to reduce the gap.
However, the above “upper side” and “lower side” do not mean an absolute vertical relationship, and represent each of which constitutes a pair so as to be identifiable. The same applies below.

(4) The gamma ray detector according to any one of (1) to (3), wherein the through hole is cylindrical, the plastic scintillator is disk-shaped, the beta ray receiver is cylindrical. Is cylindrical.
Thus, by making it disk-shaped or cylindrical, it is aligned with a circular shape common to the cylindrical through-hole, eliminating the mounting angle restriction at the time of assembly, and having a configuration that is easy to assemble.

  The detection apparatus of the present invention adopting the above-described solution means that a measurement sample at the time of detection is sandwiched between a pair of upper and lower disc-shaped beta ray scintillators and assembled as a beta ray scintillator assembly, and a pair of cylinders The upper and lower beta ray receivers are connected in series so as to sandwich the beta ray scintillator assembly at each end face of the beta ray receiver to form a beta ray receiver assembly, and cylindrical gamma rays A cylindrical through-hole is formed on the side surface excluding the end face of the circular plane of the detector so as to be perpendicular to the axis of the gamma-ray detector, and a gamma-ray scintillator is arranged around the through-hole of the gamma-ray detector case. The beta ray receiver assembly is inserted into the hole so that the gap is reduced.

As the scintillator, the beta ray scintillator of the present invention will be described using a plastic scintillator, and the gamma ray scintillator will be described using thallium activated sodium iodide (NaI (Tl)).
Since the light emitted from the scintillator is very weak light, a photomultiplier (hereinafter referred to as PMT) is used to amplify the light. The PMT, also called a photomultiplier tube, converts light into an electrical signal.

  In the embodiment, the gamma ray / beta ray simultaneous detection device is joined to the upper and lower plate-like plastic scintillators for detecting the beta rays, and the plastic scintillator is arranged to place the measurement sample at the center position. In this plastic scintillator, a pair of upper and lower beta ray receivers composed of upper and lower PMTs (not shown) for detecting the fluorescence generated due to beta rays and generating signals, and gamma ray detection Gamma rays comprising a NaI (Tl) (thallium activated sodium iodide scintillation) detector (not shown) and a PMT (not shown) that converts fluorescence generated by the NaI (Tl) detector into a signal and outputs the signal. When equipped with a detector, the beta (β) ray generated by the measurement sample is captured by the upper and lower plastic scintillators, converted into a signal, and output. , The gamma (gamma) rays sample occurs captured with NaI (Tl) detector around the through hole, and outputs the converted signal.

A plastic scintillator for cylindrical gamma rays is arranged so as to be surrounded in all directions by the plastic scintillator for beta rays, with the measurement sample as the center, and to cover directions other than the through-hole direction. With this configuration, beta rays and gamma rays can be detected accurately and efficiently in almost all directions.

The effects of the present invention will be described in detail below.
(1) The large solid angle gamma ray / beta ray simultaneous detection device of the present invention is for a beta ray in which a gamma ray scintillator is disposed around a through hole of a gamma ray detector case and a plastic scintillator is provided in the through hole of the gamma ray detector case. Insert the receiver.
This will be described with reference to the embodiment. The type 3 detection apparatus of the present invention forms a cylindrical through-hole so as to be perpendicular to the axis of the gamma ray detector on the side surface except the end face of the gamma ray detector. The scintillator is disposed around a through hole in the gamma ray detector case, and the pair of beta ray light receivers and the light receiver assembly including the plastic scintillator are inserted into the through holes in close contact with each other.

Since it is configured in this way, a small type beta ray detector is arranged in the gamma ray detector to reduce the use space, and by using one gamma ray detector, the entire device is reduced. it can.
Furthermore, since the beta-ray receiver and the gamma-ray detector are crossed around the measurement sample at the through-hole portion, the distance from the measurement sample to the receiver and detector can be shortened, resulting in improved measurement sensitivity. be able to. In addition, the gamma ray scintillator is arranged around the through hole in the gamma ray detector case, and the gamma ray solid angle with respect to the measurement sample in the beta light receiver assembly inserted into the through hole is widened excluding the through hole direction. Can be configured to angle.

(2) In (1), the through hole is provided on a side surface of the gamma ray detector so as to be orthogonal to the axis of the gamma ray detector.
In the detection device of the present invention, a cylindrical through hole is formed on a side surface excluding the end face of the gamma ray detector so as to be perpendicular to the axis of the gamma ray detector, and the beta ray receiver assembly is brought into close contact with the through hole. Insertion is arranged.
By configuring in this way, the beta ray receiver and the gamma ray detector are arranged orthogonally around the measurement sample in the through hole portion, so that the sensitivity can be maximized. As a result, the uncertainty of counting statistics can be reduced.

  In addition, the beta light guide direction and the gamma ray guide direction can be measured without overlapping, and the arrangement of detectors is reduced, preventing external noise from entering the gamma ray detector. The entire apparatus-related configuration including the shielding body (usually a stacked body of lead blocks) can be reduced in size. Furthermore, since it can be miniaturized in this way, it can be made a size and weight that can be hand-carried and can be measured outside the laboratory. In the embodiment, for example, there is a configuration example having a diameter of 100 mm and a length in the central axis direction of 320 mm.

(3) In the above (1) or (2), the beta ray photoreceiver is a pair of an upper beta ray photoreceiver and a lower beta ray photoreceiver, and the beta ray plastic scintillator is the pair of beta rays. A beta light receiver assembly is sandwiched between the light receivers.
Specifically, a measurement specimen is sandwiched between a pair of disc-shaped plastic scintillators for beta rays and assembled as a plastic scintillator assembly for beta rays, and a pair of cylindrical beta-ray photoreceivers The beta-ray plastic scintillator assembly is sandwiched between the opposing end faces of the laser to form a light receiver assembly. The cylindrical gamma ray detector has a circular plane that is perpendicular to the axis of the gamma ray detector on the side face except the end face In this way, a cylindrical through hole is formed, and the beta ray receiver assembly is inserted into the through hole so as to reduce the gap.

With this configuration, the measurement sample can be sandwiched between a pair of disc-shaped plastic scintillators for beta rays and assembled as a plastic scintillator assembly for beta rays, so that the assembly can be easily performed.
Furthermore, since the beta ray plastic scintillator assembly can be continuously arranged so as to sandwich the beta ray plastic scintillator assembly between the opposing end faces of the pair of beta ray photodetectors, the beta ray receiver assembly can be easily assembled. .

(4) The gamma ray detector according to any one of (1) to (3), wherein the through hole is cylindrical, the plastic scintillator is disk-shaped, the beta ray receiver is cylindrical. Is cylindrical.
Thus, by making it disk-shaped or cylindrical, it is possible to align with a circular shape common to the cylindrical through hole, eliminate the mounting angle restriction during assembly, and facilitate assembly.

It is the schematic of the large solid angle gamma ray and beta ray simultaneous detection apparatus which combined the beta ray detector of this invention, and the gamma ray detector. It is a schematic sectional drawing of the plastic scintillator for beta rays arrange | positioned so that a sample may be enclosed. It is a block diagram of the Example of the large solid angle gamma ray and beta ray simultaneous detection apparatus of this invention. A conventional beta-ray detector that is provided with a pair of cylindrical gamma ray detectors in a direction to sandwich the plastic scintillator and the surrounding light guide unit, and is connected to the light guide unit so as to surround the gamma ray detector. It is sectional drawing (figure cut | disconnected by the center) of the gamma ray and beta ray simultaneous detection apparatus provided. Cross-sectional view of a conventional gamma ray / beta ray simultaneous detector with a structure in which a plastic scintillator and a beta ray receiver are inserted into the well in order from the bottom into a conventional gamma ray detector with a well-shaped cylindrical hole from one end. (Figure cut at the center).

  A large solid angle gamma ray / beta ray simultaneous detection device combining a gamma (γ) ray detector and a beta (β) ray detector of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic diagram of a first embodiment of a large solid angle gamma ray / beta ray simultaneous detection apparatus 1 of type 3 according to the present invention. 1A is a bird's eye view, and FIG. 1B is a cross-sectional view taken along the line BB in FIG. 1A (the cylindrical axis of the gamma ray detector 4 in FIG. FIG. 1C is a cross-sectional view including the cylindrical axis of the beta ray receiver 3b. FIG. 1C is a plan view taken along line AA of FIG.

The type 3 detector 1 of the present invention includes a beta ray plastic scintillator 2, a beta ray receiver 11, and a gamma ray detector 30 provided with a through hole 32.
The beta-ray plastic scintillator 2 includes a pair of an upper beta-ray plastic scintillator 3 and a lower beta-ray plastic scintillator 5. The measurement sample 10 is sandwiched between the upper and lower beta-ray plastic scintillators 3 and 5. The measurement sample 10 is a solution obtained by dripping and drying a solution, and is composed of extremely thin flakes.

Practically, the scintillators 3 and 5 containing the measurement sample 10 are sealed with optical cement. The plastic scintillator assembly 2 for beta rays is formed by the plastic scintillator 3 for upper beta rays, the measurement sample 10 and the plastic scintillator 5 for lower beta rays.
Both the beta-ray plastic scintillators 3 and 5 are formed in a plate shape, preferably a disc shape as a whole. The upper and lower beta-ray plastic scintillators 3 and 5 are configured to enclose the measurement sample 10 in the central region, preferably the radial central region, of the opposing end surfaces.

  The beta ray photoreceiver 11 is composed of a pair of an upper beta ray photoreceiver 12 and a lower beta ray photoreceiver 15. The beta ray receiver 11 includes a beta ray plastic scintillator 2 and a beta ray PMT (not shown) for detecting scintillator fluorescence generated in the beta ray plastic scintillator 2 due to the beta ray and generating a signal. And a beta ray PMT drive / detection circuit (not shown).

The upper beta ray receiver 12 includes an upper beta ray receiver case 13, an upper beta ray PMT (not shown) and an upper beta ray PMT drive / detection circuit (not shown) housed in the case 13. Have.
The upper beta ray PMT drive / detection circuit includes a high voltage application circuit for the PMT, a circuit for outputting a signal from the PMT, and the like.

  The case 13 is formed in a cylindrical shape with lids on the top and bottom, preferably in a cylindrical shape. One of the lids is formed so as to position and fix the end portion of the upper beta ray plastic scintillator 3. In order to position and fix the scintillator 3, the end surface of the lid preferably has an end surface structure having a concave groove (not shown). The scintillator 3 is fitted and fixed in this concave groove. The depth of the concave groove is set to such a small dimension that the scintillator 3 can be positioned and accommodated. Practically, the scintillator 3 is housed in a concave groove and sealed with a light-shielding tape for preventing light from entering the light receiver 11 and the light receiver 12 from the outside.

The beta ray light receiving surface, which is the end surface of the upper beta ray PMT, is disposed opposite to the end surface of the upper beta ray plastic scintillator 3 via the lid of the light receiver case 13 (not shown). With this configuration, beta rays from the measurement sample can be detected in a wide angle and close state.
The lower beta ray receiver 15 includes a lower beta ray receiver case 16, a lower beta ray PMT (not shown) and a lower beta ray PMT drive / detection circuit (not shown) housed in the case 16. (Not shown).

The lower beta ray PMT drive / detection circuit includes a high voltage application circuit for the PMT, a circuit for outputting a signal from the PMT, and the like.
The case 16 is formed in a cylindrical shape with lids on the upper and lower sides, preferably in a cylindrical shape. One of the lids is formed so as to position and fix the end portion of the lower beta ray plastic scintillator 5. In order to position and fix the scintillator 5, the end surface of the lid preferably has an end surface structure having a concave groove (not shown). The scintillator 5 is fitted and fixed in this concave groove. The depth of the concave groove is set to a minute dimension that allows the scintillator 5 to be positioned and accommodated. Practically, the scintillator 5 is housed in a concave groove and sealed with a light shielding tape for preventing light from entering the light receiver 11 and the light receiver 12 from the outside.

  The beta-ray light-receiving surface, which is the end surface of the lower beta-ray PMT, is disposed in close proximity to the end surface of the lower beta-ray plastic scintillator 5 via the lid of the receiver case 16 (not shown). . With this configuration, beta rays from the measurement sample can be detected in a wide angle and close state.

  The beta-ray plastic scintillator assembly 7 is fitted, fixed, and sandwiched between the upper and lower beta-ray receivers 12 and 15, and the upper beta-ray receiver 12, the beta-ray plastic scintillator assembly 7, and the lower side The beta ray receiver 15 forms a beta ray receiver assembly 28. At that time, the end faces of the beta-ray plastic scintillator assembly 7 are fixed to the opposite end faces of the cases 13 and 16 of the light receivers 12 and 15 in a state where the outer shapes are aligned, and finally the light receivers 12 and 15. The beta-ray plastic scintillator assembly 7 is connected in close contact with each other.

  The gamma ray detector 30 includes a gamma ray detector case 31, a gamma ray scintillator (for example, NaI (TI) detector) (not shown) 35, a gamma ray PMT (not shown), and a PMT of the PMT. And a gamma ray PMT drive / detection circuit (not shown) including a high-voltage application circuit and a circuit for outputting a signal from the PMT.

  The gamma ray scintillator 35 is mainly arranged in the case 31 in the vicinity of the through hole 32 of the case 31 through which the beta ray plastic scintillator assembly 7 containing the measurement sample 10 is inserted. The gamma ray PMT and the gamma ray PMT drive / detection circuit are arranged farther outward from the through hole 32 in the radial direction than the gamma ray scintillator 35.

The case 31 is formed in a cylindrical shape, preferably a cylindrical shape, having lids constituting the gamma ray detector end face 33 at both ends, and the cylindrical axis of the gamma ray detector 30 on the gamma ray detector side face 34 excluding the end face 33. A through hole 32 is formed so as to be orthogonal to
The beta ray receiver assembly 28 including the pair of upper and lower beta ray receivers 12 and 15 and the beta ray plastic scintillator assembly 7 is inserted into the through hole 32.

  The light receiving surfaces of the gamma ray scintillator 35 and the gamma ray PMT (not shown) are positioned on a surface orthogonal to the light guide direction of the beta ray plastic scintillators 3, 5, in other words, a surface along the axial direction of the through-hole 32. With this positioning arrangement, it is possible to detect gamma rays at a wide angle and in a close state while maintaining a high light receiving sensitivity of beta rays.

  As described above based on the schematic diagram of FIG. 1, the large solid angle gamma ray / beta ray simultaneous detection device 1 of the present invention is configured so that the measurement sample 10 is positioned and arranged at the center position. Beta-ray plastic scintillators 3 and 5 and upper and lower betas which are joined to the plastic scintillators 3 and 5 and detect scintillator fluorescence generated in the plastic scintillators 3 and 5 due to beta rays and generate signals. Line PMT (not shown), a high voltage application circuit for the PMT, a circuit for outputting a signal from the PMT, and the like, a PMT drive / detection circuit for beta rays on the lower side, and a gamma ray detection circuit A plastic scintillator 35 for gamma rays, and a PMT for gamma rays that converts the fluorescence generated by the scintillator 35 into a signal and outputs the signal. Provided with not shown), and a high-pressure injection circuit and consists of the circuit for outputting a signal from the PMT gamma for PMT driving and detecting circuit for that PMT (not shown).

  The beta ray generated by the measurement sample 10 is captured by the beta ray plastic scintillators 3 and 5, converted into a signal by the beta ray PMT, processed by the beta ray PMT drive / detection circuit and output, and the measurement sample 10 is output. Gamma rays generated by the gamma ray scintillator 35 are detected, and the fluorescence generated by the gamma ray scintillator 35 is converted into a signal by a gamma ray PMT (not shown), processed by a gamma ray PMT drive / detection circuit and output. The signal becomes a wave height signal of a predetermined magnitude.

  In the case of FIG. 1, the ratio of the diameter of the gamma ray detector 30 to the diameters of both the beta light receivers 12 and 15 is about 1: 3.7, but the ratio is not limited to this.

  Since the gamma ray / beta ray simultaneous detection apparatus 1 of type 3 of the present invention is configured as described above, the measurement sample 10 can be simply measured by simply sandwiching the measurement sample 10 between the pair of upper and lower plastic scintillators 3 and 5. 10 can be set, and small PMTs with high beta ray detection efficiency constituting the upper and lower beta ray receivers 12 and 15 can be provided close to the respective plastic scintillators 3 and 5 for beta rays. In addition, simultaneous measurement can be performed with the two upper and lower beta ray receivers, and the photodetectors 12 and 15 can be brought close to the measurement sample 10. As a result, the gamma ray detector 30 is measured in the through hole 32. Since the distance to the measurement sample is reduced, the detection efficiency of gamma rays can be increased. Furthermore, the beta light guide direction and the gamma ray guide direction can be measured without overlapping.

  In addition, since it is configured as described above, it is possible to obtain individual light reception by the beta ray receivers 12 and 15 disposed opposite to each other while obtaining a large light reception solid angle of the beta ray plastic scintillators 3 and 5 around the measurement sample 10. The function to reduce the noise of the vessel is retained. Further, since the gamma ray detector 30 and the beta light receivers 12 and 15 are arranged so as to intersect with each other through the through-hole 32, the entire detection device can be made smaller as compared with the case where they are provided separately.

Compared with other types of detection devices, type 3 gamma / beta ray simultaneous detection device 1 is
In the case of the type 1 detection device 100, the light receiving solid angle of the plastic scintillator that emits light is small and the light guide distance is increased, thereby eliminating the disadvantage of measuring weak light emission, that is, low energy beta rays,
In the case of the type 2 detector 110, the noise of the light receiver itself cannot be separated from the low energy beta component, and the disadvantage that the light emitted from the plastic scintillator far from the light receiver does not easily reach the light receiver is eliminated. .

  In the example of the schematic diagram of FIG. 1, the plastic scintillator 2 for beta rays is used for detecting beta rays, but may be, for example, an inorganic scintillator, a liquid scintillator, a proportional counter, a GM counter, or the like. Further, although a gamma ray scintillator, for example, a NaI (Tl) detector (not shown) is used for gamma ray detection, other organic scintillators, inorganic scintillators, etc. may be used.

  The detection apparatus 1 of the present invention employing the above-described solution is assembled as a beta-ray plastic scintillator assembly 7 by sandwiching a measurement sample 10 between a pair of disk-like upper and lower beta-ray plastic scintillators 3 and 5. A pair of cylindrical upper and lower beta ray receivers 12 and 15 are connected in series so that the beta ray plastic scintillator assembly 7 is sandwiched between the opposite end faces of the beta ray receivers 12 and 15. A beta ray receiver assembly 28 is formed, and a cylindrical through hole 32 is formed on a side surface 34 of the cylindrical gamma ray detector 30 except for the end surface 23 of the circular plane so as to be orthogonal to the axis of the gamma ray detector 30. In this through hole 32, the beta ray receiver assembly 28 comprising the pair of beta ray receivers 12 and 15 and the beta ray plastic scintillators 3 and 5 has a small gap. It is inserted and arranged in Kunar so.

Since it is comprised in this way, the type 3 detection apparatus 1 of this invention has the effect | action and effect of following (a)-(j) description.
(A) The measurement sample 10 can be easily set by simply sandwiching it between a pair of upper and lower plastic scintillators 3 and 5 for beta rays,
(B) The upper and lower beta-ray plastic scintillators 3 and 5 that house the measurement sample 10 at the center position are flat plates, particularly discs, which are used as the upper and lower beta-ray receivers 12 and 15. Since the positioning is performed in close contact with the ends of the cases 13 and 16, the distance from the measurement sample 10 to the beta ray receivers 12 and 15 is closer than the conventional one, and the measurement sample 10 has a wide angle in almost all directions. Can measure beta rays.

  (C) From the opposite viewpoint, the upper and lower beta ray light receivers 12 and 15 can be provided close to the beta ray plastic scintillators 3 and 5. This is because, for example, the PMT constituting the upper and lower beta ray receivers 12 and 15, that is, a small PMT having a large beta ray detection efficiency, is applied to the upper and lower beta ray plastic scintillators 3 and 5. Since they can be provided close to each other, simultaneous measurement can be performed with two light receivers, and the light receivers 12 and 15 can be disposed close to the measurement sample 10. At the same time, the gamma ray detector 30 can be disposed close to and opposite to the measurement sample 10 other than the beta-ray plastic scintillators 3 and 5 without any inclusions, so that the distance from the measurement sample 10 is reduced and the gamma ray detection efficiency is improved. Can be bigger.

(D) While obtaining a large light receiving solid angle with the plastic scintillators 3 and 5 for beta rays, the noises of the individual light receivers can be reduced by the upper and lower beta ray light receivers 12 and 15 arranged opposite to each other.
(E) Since the gamma ray scintillator is arranged around the through hole of the gamma ray detector case, and the beta ray receiver having the beta ray plastic scintillator is inserted into the through hole of the gamma ray detector, In addition to reducing the space used by placing the beta ray detector inside the gamma ray detector, the entire device can be made smaller by using only one gamma ray detector.

  Furthermore, since the beta-ray receiver and the gamma-ray detector are crossed around the measurement sample at the through-hole portion, the distance from the measurement sample to the receiver and detector can be shortened, resulting in improved measurement sensitivity. be able to. Also, the gamma ray scintillator is arranged around the through hole of the gamma ray detector case, and the gamma ray solid angle with respect to the measurement sample in the beta ray receiver assembly inserted into the through hole is a wide angle excluding the through hole direction. Can be configured.

  (F) Since the upper and lower beta light receivers 12 and 15 are arranged in the through-hole 32 provided in the gamma ray detector 30, the entire apparatus can be made smaller by the amount of connection. Further, since the beta light receivers 12 and 15 are connected to the measurement sample 10, the beta ray measurement sensitivity can be improved, and the gamma ray detector 30 is connected to the measurement sample 10 through the through hole 32. Since the two are arranged close to each other, the uncertainty of measurement accuracy can be reduced by the amount close to the measurement sample 10.

(G) Compared with the type 1 and type 2 detectors, the gamma ray / beta ray simultaneous detection device 1 of type 3 of the present invention has the above-described configuration.
In the case of the type 1 detection device 100, the light receiving solid angle of the plastic scintillator that emits light is small and the light guide distance is increased, thereby eliminating the disadvantage of measuring weak light emission, that is, low energy beta rays,
In the case of the type 2 detection device 110, the noise of the light receiver itself cannot be separated from the low energy beta component, and the disadvantage that the light emitted from the plastic scintillator far from the light receiver does not easily reach the light receiver is eliminated.

  (H) In the gamma ray / beta ray simultaneous detection apparatus 1 of the present invention, the through-hole 32 is provided in the gamma ray detector 30 and the upper and lower beta-ray plastic scintillators 3 and 5 that house the measurement sample 10 are overlapped. Are provided with beta ray receivers 12 and 15 made of PMT (not shown) for detecting scintillator fluorescence caused by beta rays and generating signals, and the upper and lower beta ray plastic scintillators 3 and 5 are overlapped. A gamma ray detector 30 including a NaI (Tl) (thallium activated sodium iodide scintillation) detector 35 was provided in a direction orthogonal to the direction.

  As a result, the fluorescence in the upper and lower beta-ray plastic scintillators 3 and 5 generated by the energy application in the upper and lower beta-ray plastic scintillators 3 and 5 by the beta rays is reflected in the scintillators 3 and 5. And is measured by a beta ray PMT in the overlapping direction.

  On the other hand, a NaI (Tl) (thallium activated sodium iodide scintillation) detector 35 was provided in a direction orthogonal to the overlapping direction of the upper and lower beta-ray plastic scintillators 3 and 5. As a result, the light guide direction of the beta rays and the light guide direction of the gamma rays can be measured without overlapping, and restrictions on the arrangement of the light receivers 12 and 15 and the detector 30 are reduced, and measurement is facilitated. As a result, it is possible to detect radiation mechanically, easily, and with high accuracy without requiring an artificial processing of liquid as in the prior art. Further, the configuration is portable and can be made compact.

(I) A through-hole 32 is provided in the gamma ray detector 30, and the beta ray detection unit and the gamma ray detection unit are arranged in different directions, that is, in a direction orthogonal to the measurement sample, thereby enabling easy exchange of the measurement sample. However, since the solid angle of measurement is extended efficiently, accurate measurement can be performed while greatly reducing the labor of measurement.
(J) The sensitivity is higher than that of the conventional radioactivity measurement by gamma ray spectrometry, the amount of measurement sample to be prepared can be reduced, and the measurement time and cost can be reduced.

A second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 3 is a block diagram of an embodiment of the large solid angle gamma ray / beta ray simultaneous detection apparatus of the present invention.
FIG. 3A is a sectional view corresponding to FIG. 1B in the case of the embodiment. FIG. 3B is an exploded enlarged view of the circled portion of FIG.

The large solid angle gamma ray / beta ray simultaneous detection apparatus 1 of FIG. 3 is a beta ray light receiver assembly 28 which is schematically shown in FIG. 1 and includes a beta ray plastic scintillator assembly 7 and a beta ray light receiver 11. And a specific configuration of the gamma ray detector 30.
As shown in FIG. 3B, the beta-ray plastic scintillator assembly 7 includes a measurement sample 10, a concave beta-ray plastic scintillator 8 having a concave end surface 4 on a disk, and a convex end surface 6 on the disk. Is formed of a plastic scintillator 9 for convex beta rays.

  At the time of assembly, the measurement sample 10 is placed in the concave portion of the concave end surface 4 and the convex portion of the convex end surface 6 is concavo-convexly fitted. The concave end surface 4 and the convex end surface 6 preferably have a circular outer peripheral shape. The measurement sample 10 is a solution obtained by dripping and drying a solution, and is composed of extremely thin flakes. Practically, the scintillators 8 and 9 containing the measurement sample 10 are sealed with optical cement.

  The beta-ray plastic scintillator assembly 7 assembled in this way has a recess in the upper concave end face 14 of the upper beta-ray receiver case 13 and a lower beta-ray receiver case 16 as shown in FIG. The lower concave end surface 17 is fitted into the concave portion. In other words, it can be said that the upper and lower concave end faces 14 and 17 are formed by annular convex walls. The annular convex wall is constituted by the upper beta ray receiver case 13 or the upper beta ray PMT 22 and the lower beta ray receiver case 16 or the lower beta ray PMT 23.

  By adopting such a fitting structure, with the measurement sample 10 as the center, alignment of the beta ray plastic scintillator assembly 7, the upper beta ray PMT22, and the lower beta ray PMT23 is performed.

  The beta ray receiver 11 includes an upper beta ray receiver 12 and a lower beta ray receiver 15. The upper beta ray receiver 12 accommodates an upper beta ray PMT 22 and an upper beta ray PMT drive / detection circuit 24 in a cylindrical upper beta ray receiver case 13, and from the case 13 for signals and high voltage. The upper beta wire cable 26 for power feeding or the like is drawn out. Similarly, the lower beta ray receiver 15 accommodates a lower beta ray PMT 23 and a lower beta ray PMT drive / detection circuit 25 in a cylindrical lower beta ray receiver case 16. The lower beta wire cable 27 for signal or high voltage power supply is drawn from the case 16 so as to be drawn out.

  The PMT drive / detection circuits 24 and 25 for the upper and lower beta rays are composed of a high voltage application circuit for the PMT, a circuit for outputting a signal from the PMT, and the like.

  The gamma ray detector 30 is provided with a through hole 32 in a cylindrical gamma ray detector case 31 in a direction orthogonal to the longitudinal axis of the cylinder. The through hole 32 opens in a cylindrical surface on the side surface excluding both end surfaces. The through-hole 32 is provided with a thin metal cylinder 37 such as aluminum having a thickness of about 0.5 mm between the openings. The metal cylinder 37 is fixed to the gamma ray detector case 31. A gamma ray scintillator 35 is provided in the space inside the gamma ray detector case 31 partitioned by the optical window 39 and excluding the inside of the metal cylinder 37. A reflective material 36 is attached between the gamma ray detector case 31 and the gamma ray scintillator 35.

A magnetic shield 38 is embedded in the remaining gamma ray detector case 31 partitioned by the optical window 39, and a gamma ray PMT 40 and a gamma ray PMT drive / detection circuit 41 are housed in that order from the optical window 39.
The gamma ray PMT drive / detection circuit 41 includes a high voltage application circuit for the PMT, a circuit for outputting a signal from the PMT, and the like.

A gamma ray detector case 31 in contact with the gamma ray PMT drive / detection circuit 41 is provided with a connector 42 provided with a gamma cable 43 for signals and high voltage power supply.
When the beta ray receiver assembly 28 is combined with the gamma ray detector 30, a fixing device 50 with an arbitrary alignment as shown in FIG. 3A is used to specify the position of the measurement sample 10, for example. . At least one pair of the fixing devices 50 is provided on any opening side of the through hole 32.

  The fixing device 50 in FIG. 3 (a) is provided with a both-side tapered member 51 having tapered surfaces on both the upper and lower sides, a lower tapered member 52 having a tapered surface on the lower side, and a tapered surface on the upper side. It comprises an upper taper member 53 and a spring-loaded bolt 54 provided with a coil spring for pressurization. Both side taper members 51 project from the upper beta ray receiver case 13 (or lower beta ray receiver case 16) of the beta ray receiver assembly 28 outwardly perpendicular to the axial direction. An upper taper member 53 is fixed at a corresponding position of the gamma ray casing 31 facing the both side taper members 51, and a lower taper member 52 is placed thereon, and both members are fixed in a compressed state by spring-loaded bolts 54. .

When the bolts 54 are screwed together, the beta ray receiver assembly 28 is moved to a predetermined center position and fixed in a pressurized state by sliding operation of the tapered surfaces of the tapered members on both sides.
Prior to the screwing operation of the bolt 54, as described above, the beta-ray plastic scintillator assembly 7 is configured by positioning by concave-convex fitting as described above, and the upper beta-ray receiver 12 and the lower beta-beam receiver The connection of the line light receiver 15 is constituted by an uneven fitting of the assembly 7 with the upper and lower concave end faces 14 and 17.

Since it is configured as in the embodiment of FIG. 3, the following operations and effects are achieved.
(1) The measurement sample 10 can be appropriately positioned and fixed in the concave end face 4 of the concave beta ray plastic scintillator 8 by the convex end face 6 of the convex beta ray plastic scintillator 9.
(2) The concave and convex beta ray plastic scintillators 8 and 9 can be fixed by fitting the convex end surface 6 into the concave end surface 4.

(3) The beta ray plastic scintillator assembly 7 can be fitted and fixed in the recesses of the upper concave end surface 14 and the lower concave end surface 17 of the upper and lower beta ray receivers 12, 15.
(4) By fitting and fixing as in (3) above, the upper and lower beta ray receivers 12 and 15 can be aligned and connected at the center position.

(5) Since the beta ray receiver assembly 28 can be inserted into the through-hole 32 from both sides thereof, the upper beta ray PMT 22 having the concave end face 14 and the lower side having the concave end face 17 with respect to the measurement sample 10. The beta ray PMT 24 can be arranged oppositely, and the beta ray from the measurement sample material 10 can be detected almost in all directions.

(6) Since the beta ray receiver assembly 28 to which the measurement sample 10 is fixed is inserted and disposed in the through hole 32 and the gamma ray scintillator 35 is provided around the radial direction of the through hole 32, the detection of the beta ray is high. In addition to efficiency, gamma rays can be detected with high efficiency.
(7) Since the plastic scintillator assembly 7 for beta rays is configured to surround the measurement sample 10, beta rays can be detected in almost all directions.
Also, the gamma ray scintillator is arranged around the through hole of the gamma ray detector case, and the gamma ray solid angle with respect to the measurement sample in the beta ray receiver assembly inserted into the through hole is a wide angle excluding the through hole direction. Can be configured.
The embodiment shown in FIG. 3 described above is included in the technical idea described in the schematic diagram of the present invention shown in FIG.

DESCRIPTION OF SYMBOLS 1 Gamma ray and beta ray simultaneous detection apparatus 2 Beta ray plastic scintillator 3 Upper beta ray plastic scintillator 4 Concave end face 5 Lower beta ray plastic scintillator 6 Convex end face 7 Beta ray plastic scintillator assembly 8 Concave beta ray plastic Scintillator 9 Plastic scintillator for convex beta ray 10 Measurement sample 11 Beta ray receiver 12 Upper beta ray receiver 13 Upper beta ray receiver case 14 Upper concave end face 15 Lower beta ray receiver 16 Lower beta ray Receiver case 17 Lower concave end face 22 Upper beta wire PMT
23 PMT for lower beta line
24 Upper Beta Line PMT Drive / Detection Circuit 25 Lower Beta Line PMT Drive / Detection Circuit 26 Upper Beta Line Cable 27 Lower Beta Line Cable 28 Beta Line Receiver Assembly 30 Gamma Ray Detector 31 Gamma Ray Detector Case 32 Through-hole 33 Gamma-ray detector end face 34 Gamma-ray detector side face 35 Gamma-ray scintillator 36 Reflector 37 Metal cylinder 38 Magnetic shield 39 Optical window 40 GMT PMT
41 gamma ray PMT drive / detection circuit 42 connector 43 gamma ray cable 50 fixing device 51 taper member on both sides 52 upper taper member 53 lower taper member 54 bolt with spring

Claims (1)

The gamma ray detector has a cylindrical gamma ray scintillator and a gamma ray detector case that houses the gamma ray scintillator ,
A cylindrical through-hole is provided on the side surface of the cylindrical gamma ray scintillator and the side surface of the gamma ray detector case corresponding to the side surface so as to be orthogonal to the axis of the cylindrical gamma ray scintillator,
A beta ray receiver having a beta ray plastic scintillator is inserted in close contact with the through hole,
The beta ray receiver is a pair of an upper beta ray receiver and a lower beta ray receiver, and the beta ray plastic scintillator is sandwiched between the pair of beta ray receivers to form a receiver assembly,
The beta ray plastic scintillator has a disk shape, the beta ray receiver has a cylindrical shape,
The beta-ray plastic scintillator is an assembly comprising a measurement sample, a concave beta-ray plastic scintillator having a concave end surface on a disc, and a convex beta-ray plastic scintillator having a convex end surface on a disc,
The assembly includes a concave portion of an upper concave end surface of an upper beta ray receiver case in the upper beta ray receiver and a lower concave end surface of a lower beta ray receiver case in the lower beta ray receiver. A large solid angle gamma ray / beta ray simultaneous detection device characterized by being fitted in a recess .