JP6343785B2 - Neutron scintillator - Google Patents

Description

The present invention relates to a translucent neutron scintillator that combines a zinc sulfide (ZnS) phosphor and ⁶ Li or ¹⁰ B as a neutron converter. More specifically, the present invention is characterized in that a dye as a wavelength conversion agent is added to a scintillator composed of zinc sulfide (ZnS) phosphor and ⁶ Li or ¹⁰ B as a neutron converter to increase the detection efficiency for neutrons. It relates to translucent neutron scintillators.

Conventionally, a neutron detector in which a neutron scintillator containing ⁶ Li or ¹⁰ B, which is a neutron converter, and a photodetection element such as a photomultiplier tube have been used for neutron detection.

In the neutron scintillator, the nuclear reaction between ⁶ Li and neutrons:
n + ⁶ Li-> ³ H + α
Neutron detection by detecting triton ( ³ H) and alpha rays emitted by neutron, or nuclear reaction between neutron converter ¹⁰ B and neutron:
n + ¹⁰ B-> ⁷ Li + α
Neutron detection is carried out by detecting ⁷ Li and alpha rays emitted by the above.

As a translucent neutron scintillator, a ZnS / ⁶ LiF translucent neutron scintillator manufactured by mixing a ZnS phosphor and ⁶ LiF, which is a neutron converter, and then mixing with an adhesive and applying it to a substrate has been commercially available for many years. Widely used and marketed (Non-Patent Document 1).

^As a neutron scintillator using ¹⁰ B as a converter, ZnS / ¹⁰ B ₂ O ₃ translucent is manufactured by mixing ZnS phosphor and ¹⁰ B concentrated boric acid (H ₃ ¹⁰ B ₂ O ₃ ) and then sintering. Neutron scintillators have been developed and used in neutron image detectors (Non-patent Document 2, Patent Document 1).

ZnS phosphors have been used in these scintillators because of their low gamma-ray detection sensitivity and extremely high fluorescence with respect to alpha rays. However, since these scintillators are translucent, increasing the thickness prevents light emitted in the back from coming out to the scintillator surface, so increasing the scintillator thickness increases neutron detection efficiency. There were limits. On the other hand, as a transparent scintillator capable of increasing the thickness of the scintillator, it is commercially available glass scintillator containing ⁶ Li ⁽⁶ Li glass scintillator) have been widely used conventionally. However, since the ⁶ Li glass scintillator has a high gamma ray sensitivity, it is difficult to use it in a place with a high gamma ray background.

  Since the beginning of the 21st century, research on single crystal scintillators for neutrons has progressed, and neutron single crystal scintillators such as LiYF4: Ce have been developed and used. However, although the decay time of these single crystal scintillators is reduced to a fraction of that of the conventional translucent neutron scintillator using ZnS phosphor, the sensitivity to gamma rays is lower than that of the translucent neutron scintillator using ZnS phosphor. It is very difficult to use in neutron scattering research or neutron radiography, which requires a large and low gamma ray background. Therefore, in some scintillators of these single crystal scintillators, attempts have been made to perform neutron / gamma ray discrimination by utilizing the fact that the scintillation signal waveforms generated when gamma rays and neutrons are incident are different. However, the signal generated by gamma rays uses the phenomenon that the rising edge of the scintillation signal is fast in the case of a single crystal scintillator, so the circuit for discrimination becomes complicated, which is an important issue in manufacturing a large-area neutron image detector. There are significant problems in terms of technical and cost related to the multi-channel signal processing circuit (Non-patent Document 3).

  A scintillator detector combining a scintillator and a wavelength conversion agent (dye) or a wavelength shift fiber has been proposed.

  A liquid scintillation detector was proposed, alpha or beta rays were detected by an organic scintillator, and the emitted fluorescence was wavelength-converted by a wavelength conversion agent, and shifted to around 420 nm, the wavelength region with the highest quantum efficiency of a photomultiplier tube. The method of increasing the detection sensitivity is often used. However, since the scintillator itself is transparent, the purpose of using the wavelength conversion agent is to convert the wavelength to match the sensitivity of the photomultiplier tube (Non-patent Document 4).

  Many single crystal neutron scintillators have an emission spectrum peak wavelength of 350 nm or less. Since the quantum efficiency of photodetection elements such as photomultiplier tubes is in a very low wavelength region, a method is used in which the fluorescence generated in the scintillator is converted to a long wavelength using a dye or a wavelength shifter plate and then detected. (Non-Patent Document 4).

These dyes and wavelength shifter plate use examples all play a role of converting the wavelength of fluorescence emitted from the neutron scintillator into the optimum sensitivity wavelength region of a photodetector such as a photomultiplier tube. On the other hand, there is a use example of a two-dimensional image detector in which a ZnS: Ag / ⁶ LiF neutron scintillator and a wavelength shifter plate are combined. The role of the wavelength shifter plate is to efficiently collect the fluorescence emitted from the neutron scintillator and distribute it to the X-axis and Y-axis fluorescence (Patent Document 2).

Further, in a neutron radiography apparatus using fast neutrons, a screen having a structure in which a ZnS / ⁶ LiF neutron detector is embedded between wavelength-shifted fibers spread as a screen for a CCD camera is used. The thickness is increased to several mm. In this case, since the fluorescence emitted from the ZnS / ⁶ LiF neutron detector is wavelength-converted by the wavelength shift fiber once and passes through the wavelength shift fiber to reach the surface of the scintillator, only a few percent of the emitted fluorescence is emitted. Is only released from the screen surface (Non-Patent Document 6).

  Furthermore, a method has been proposed in which a colorant is attached to a silver activated zinc sulfide phosphor to impart non-aggregating ability (Patent Document 3). However, the purpose relates to a method for producing a zinc fluorescent material with a colorant for coating the fluorescent material, and no consideration is given to a neutron scintillator.

  Improvement of neutron scattering research in neutron image detectors using neutron scintillators used in neutron scattering experiments at pulsed neutron research facilities using accelerators such as J-PARC in Japan, ISIS in the UK, and SNS in the United States In addition, with the enhancement of the accelerator output, improvement in detection efficiency for pulsed neutrons, neutron imaging measurement at a high count rate, and further reduction in gamma ray sensitivity are required.

In order to reduce the gamma-ray sensitivity, the present inventors use a conventional silver-activated zinc sulfide (ZnS: Ag) phosphor and use an optical filter that passes a wavelength shorter than 450 nm to have a short-lived component (with alpha rays). It has been proposed that the sensitivity spectrum) is taken out and the gamma ray sensitivity is lowered (Patent Document 4). Accordingly, the present inventor attempted to reduce decay time and afterglow, which are indispensable for high count rate measurement, and simultaneously detect silver activated zinc sulfide (ZnS: Ag) for particle beam detection that enables neutron image detection with high count efficiency. ) We are studying phosphors. However, this particle beam detecting ZnS: Ag phosphor is colored very light brown to light brown in order to reduce the gamma ray sensitivity. In particular, in a semi-transparent neutron scintillator that uses a structure in which multiple layers of phosphors and neutron converters are stacked, fluorescence in the short wavelength region that is emitted during α-ray irradiation is absorbed by the phosphors and the neutron converter, and is reflected on the surface It becomes difficult to reach and detection efficiency cannot be increased. On the other hand, P11, which is a conventional ZnS: Ag phosphor, or 1109-041 manufactured by Nichia Corporation, which is the same type of phosphor, is white. For this reason, when a scintillator having the same thickness is made by the conventional manufacturing method, it is difficult to obtain the neutron detection efficiency of the conventional ZnS / ⁶ LiF translucent neutron scintillator using a ZnS: Ag phosphor such as P11. there were.

  Moreover, the neutron image detector used for the neutron scattering experiment apparatus using pulsed neutrons needs to detect a wide range of neutrons at a time from about 10 to 0.5 mm as the wavelength of neutrons. First, in order to measure short wavelength neutrons, that is, high energy neutrons, it is necessary to increase the detection efficiency by increasing the thickness of the scintillator. On the other hand, when detecting long-wavelength neutrons, that is, low-energy neutrons, the probability of neutrons to react and emit light near the scintillator substrate near the neutron source increases due to the capture reaction with the neutron converter. When the thickness is increased, fluorescence cannot reach the scintillator surface, and the neutron detection efficiency decreases. Therefore, in order to detect neutrons with a long wavelength, it is necessary to use a semi-transparent neutron scintillator with a thin thickness, and it is necessary to satisfy the requirements contrary to the case of neutrons with a short wavelength. For this reason, it has been very difficult to detect neutrons in a wide range from 10 to 0.5 to the best state at all wavelengths.

JP 2005-200461 A JP 2010-175570 A Japanese Patent Laid-Open No. 01-313587 JP-A-2005-300479

Nulcl. Instr. And Meth. 75 (1969) 35-42 Nucl. Instrum. & Meth., A529 (2004) 325-328 Nucl. Instr. & Meth., A652 (2011) 435-438 Nulcl. Instr. & Meth., 112 (1973) 111-116 Nucl. Instr. & Meth., A601 (2009) 282-293 Nucl. Instr. & Meth., A510 (2003) 325-333

  It is an object of the present invention to provide a neutron scintillator that lowers gamma ray sensitivity, improves detection efficiency for pulsed neutrons, and enables neutron imaging measurement at a high count rate.

  It is another object of the present invention to provide a neutron scintillator that can reduce gamma ray sensitivity and cope with detection of a wide range of neutron wavelengths, improve detection efficiency, and enable neutron image measurement at a high count rate.

  It is another object of the present invention to provide a screen optimal for radiography using pulsed neutrons that can detect a wide range of neutron wavelengths.

  The present inventors considered that a translucent neutron scintillator using a ZnS-based phosphor having low sensitivity to gamma rays is useful for solving the problems, and as a result of intensive studies, the present invention has been completed.

According to this invention, the neutron scintillator of the following aspect is provided.
[1] A translucent ZnS-based neutron scintillator including a substrate and a neutron detector including an adhesive substance in which a dye as a ZnS-based phosphor, a neutron converter, and a wavelength conversion agent on the substrate is dispersed.
[2] The ZnS phosphor according to [1], wherein the ZnS phosphor for particle beam detection is a ZnS: Ag phosphor, a ZnS: Ag, Cl phosphor, a ZnS: Ag, Al phosphor, or a ZnS: Cu phosphor. Translucent ZnS neutron scintillator.
[3] The translucent ZnS neutron scintillator according to [1] or [2], wherein the neutron converter is a ⁶ LiF or ¹⁰ B neutron converter.
[4] The dye as the wavelength converting agent is BisMSB (1,4-Bis (2-methylstyryl) benzene), POPOP (1,4-Bis (5-phenyl-2-oxazolyl) benzene), Coumarin 30 (7 -(Diethylamino) -3- (1-methyl-1H-benzimidazol-2-yl) -2H-1-benzopyran-2-one), anthracene derivative (7,12-dimethylbenz [α] anthracene), 4-dimethylamino Translucent as described in any one of [1] to [3], which is 4-Dimethylamino-4-Nitrostilbene or Nile Red (9-diethylamino-5-benzo [α] phenoxazinone) ZnS-based neutron scintillator.
[5] The neutron detector comprises (1) a curing agent mainly composed of a modified alicyclic polyamine, modified aliphatic polyamine or aliphatic diamine, and (2) water, ethyl alcohol, methyl alcohol, water and ethyl alcohol. A ZnS phosphor and a dye are mixed with an adhesive substance containing a mixed solution of the above or a solvent selected from a mixed solution of water and methyl alcohol, and the mixture is applied on a substrate, dried and solidified. The translucent ZnS neutron scintillator according to any one of [1] to [4].

  In the present invention, by adding an appropriate amount of an appropriate dye as a wavelength conversion agent, the fluorescence generated from the ZnS-based phosphor can be transmitted from a short wavelength (430 to 380 nm) spectral region in which the transmittance decreases, and the transmittance is long. The wavelength can be converted into fluorescence in the wavelength (440 nm or more) region. Since the wavelength-converted fluorescence passes through the neutron scintillator, neutron detection efficiency is improved.

  According to the present invention, there is provided a neutron scintillator that reduces gamma ray sensitivity, improves detection efficiency for pulsed neutrons, and enables neutron imaging measurement at a high count rate.

  In addition, a neutron scintillator is provided that has low gamma-ray sensitivity, supports detection of a wide range of neutron wavelengths, improves detection efficiency, and enables neutron image measurement at a high count rate.

  The neutron scintillator of the present invention can be applied to a screen optimal for radiography using pulsed neutrons corresponding to detection of a wide range of neutron wavelengths.

It is a graph showing the transmittance of ⁶ LiF and ¹⁰ B neutron converter. It is a schematic diagram which shows the structure of the neutron scintillator of this invention. It is a graph which compares and shows the transmittance | permeability of ZnS: Ag fluorescent substance for particle beam detection (alpha ray detection ratio 0.63) and P11 type ZnS: Ag fluorescent substance (alpha ray detection ratio 0.29). It is a graph which compares and shows the fluorescence spectrum of ZnS: Ag fluorescent substance for particle beam detection (alpha ray detection ratio 0.63), and P11 type ZnS: Ag fluorescent substance (alpha ray detection ratio 0.29). It is a graph which compares and shows the fluorescence spectrum of the ZnS: Ag fluorescent substance for particle beam detection (alpha ray detection ratio 0.63), the absorption spectrum of BisMSB, and the wavelength conversion fluorescence spectrum. It is a graph which shows the change of the detection efficiency with respect to a neutron when the weight of the wavelength conversion agent of Example 1 is changed, and decay time. Wavelength conversion agent added in Example ^{2 (0.25wt%) ZnS / 6} LiF the number of photons distribution translucent neutron scintillator emits, ^ZnS / 6 LiF translucent neutron scintillator without additives, and AST, Inc., commercially available It is a graph shown in comparison with the photon number distribution of the manufactured ZnS / ⁶ LiF translucent neutron scintillator. It is a graph which shows the fluorescence spectrum and transmittance | permeability of the ZnS: Ag fluorescent substance for particle beam detection (alpha ray detection ratio 0.51) used in Example 3. It is a graph which compares and shows the fluorescence spectrum of the ZnS: Ag fluorescent substance for particle beam detection (alpha ray detection ratio 0.51) used in Example 3, the absorption spectrum of BisMSB, and the wavelength conversion fluorescence spectrum. It is a graph which shows the change of the detection efficiency with respect to a neutron when the weight of the wavelength conversion agent of Example 3 is changed, and decay time. It is a graph which shows the fluorescence spectrum and transmittance | permeability characteristic of 1109-041 fluorescent substance used in Example 4. FIG. It is a graph which compares and shows the fluorescence spectrum of 1109-041 fluorescent substance of Example 4, the absorption spectrum of BisMSB, and a wavelength conversion fluorescence spectrum. It is a graph which shows the change of the detection efficiency with respect to a neutron at the time of changing the weight of the wavelength conversion agent of Example 4, and decay time. It is a graph which shows the fluorescence spectrum of the ZnS: Ag, Al fluorescent substance used in Example 5, and the transmittance | permeability characteristic of fluorescent substance. It is a graph which compares and shows the fluorescence spectrum of 1055-152 fluorescent substance of Example 5, the absorption spectrum of BisMSB, and a wavelength conversion fluorescence spectrum. It is a graph which shows the change of the detection efficiency with respect to a neutron at the time of changing the weight of the wavelength conversion agent of Example 5, and decay time. It is a graph which compares and compares the fluorescence spectrum of the ZnS: Ag fluorescent substance for particle beam detection (alpha ray detection ratio 0.51) used in Example 6, the absorption spectrum of anthracene, and a wavelength conversion fluorescence spectrum. It is a graph which shows the change of the detection efficiency with respect to a neutron at the time of changing the weight of the wavelength conversion agent of Example 6, and decay time. It is a graph which compares and shows the fluorescence spectrum of the ZnS: Ag fluorescent substance (alpha ray detection ratio 0.63) used in Example 7, the absorption spectrum of POPOP, and a wavelength conversion fluorescence spectrum. It is a graph which compares and shows the fluorescence spectrum of the ZnS: Ag fluorescent substance for particle beam detection used in Example 8, the absorption spectrum of coumarin 30, and the wavelength conversion fluorescence spectrum. 10 is a graph showing a comparison of a fluorescence spectrum of a ZnS: Ag phosphor for particle beam detection used in Example 9, an absorption spectrum of 4-Dimethylamino-4-Nitrostilbene, and a wavelength-converted fluorescence spectrum. It is a graph which shows the fluorescence spectrum and transmittance | permeability characteristic of Nichia Chemical Co., Ltd. 1108-110 fluorescent substance which are ZnS: Cu fluorescent substance used in Example 10. FIG. It is a graph which compares and shows the fluorescence spectrum of the ZnS: Cu fluorescent substance used in Example 10, the absorption spectrum of Nile Red, and the wavelength conversion fluorescence spectrum. It is a graph which shows each fluorescence spectrum of alpha ray irradiation of the ZnS fluorescent substance for particle beam detection whose alpha ray detection ratio is 0.63, gamma ray irradiation, and alpha ray sensitivity. It is a graph which shows each fluorescence spectrum of alpha ray irradiation, gamma ray irradiation, and alpha ray sensitive of the ZnS fluorescent substance for particle beam detection whose alpha ray detection ratio is 0.51.

Preferred embodiment

  Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings, but the present invention is not limited thereto.

FIG. 2 is a schematic diagram showing the structure of the ZnS / ⁶ LiF translucent neutron scintillator of the present invention. An aluminum plate is usually used as the scintillator substrate. It is a structure in which a neutron detector in which a ZnS phosphor, ⁶ LiF powder as a neutron converter, and a trace amount of dye as a wavelength conversion agent are mixed with an adhesive on an aluminum plate is applied. Usually, the thickness of the neutron detector is 250 μm to 500 μm. Neutrons are irradiated from the front of the aluminum substrate. In a conventional scintillator, the alpha rays and triton ( ³ H) released by capture reaction with ⁶ Li of ⁶ LiF cause the ZnS phosphor to emit light, and the emitted fluorescence reaches the scintillator surface while being absorbed by the neutron detector. Is done. For this reason, especially when neutrons are captured near the substrate, the emitted fluorescence decreases while reaching the scintillator surface and cannot be detected as a neutron signal. In order to minimize absorption by the neutron detector including absorption by the neutron converter as much as possible, the present invention converts the emitted fluorescence into a long wavelength band with good transmittance and transmits it through the neutron detector. Make it easier.

  As the ZnS phosphor, those having an alpha ray detection ratio of 0.35 to 1.00 are preferable. The alpha ray detection ratio emits fluorescence over 320 nm to 580 nm when irradiated with alpha rays, and emits when irradiated with an alpha ray sensitive fluorescence spectrum whose peak wavelength is 395 nm to 410 nm and gamma rays or electron beams. In the ZnS: Ag phosphor for particle beam detection showing a synthesized fluorescence spectrum, the fluorescence spectrum ranging from 380 nm to 560 nm and corresponding to the fluorescence spectrum having a peak wavelength of 435 nm to 450 nm is alpha-sensitive It means the ratio of the intensity of the alpha-sensitive fluorescent spectrum to the intensity of the total fluorescent spectrum (corresponding to the alpha-irradiated spectrum) obtained by adding the fluorescent spectrum and the gamma-irradiated fluorescent spectrum. In the ZnS phosphors shown in FIGS. 24 and 25, the alpha ray detection ratios are 0.63 and 0 from the alpha ray irradiation fluorescence spectrum, the gamma ray irradiation fluorescence spectrum, and the alpha ray sensitive fluorescence spectrum of the particle beam detection ZnS phosphor, respectively. .51.

  The ZnS: Ag phosphor for particle beam detection with an alpha ray detection ratio of 0.63 is a ZnS: Ag, Cl phosphor whose alpha in the short wavelength region ranging from 350 nm to 450 nm is typified by conventional P11 (alpha ray detection ratio: It is increased 2.2 times compared to 0.29). As the alpha ray detection rate increases, the decay time characteristic is improved, the afterglow component is reduced, and the gamma ray sensitivity is also reduced. However, as the alpha ray detection ratio increases, the phosphor color becomes darker from light brown to light brown. For this reason, when this phosphor is used in a translucent neutron scintillator, it is necessary to derive fluorescence of a short wavelength component in this region to the scintillator surface.

  In order to investigate the reason why the emitted fluorescence does not appear on the surface of the scintillator, the transmittance of various types of ZnS: Ag phosphors including P11 was measured. FIG. 3 shows transmittance characteristics of a conventional P11 type ZnS: Ag phosphor and a ZnS: Ag phosphor for particle beam having an alpha ray detection ratio of 0.63. As a result, in both cases of ZnS: Ag phosphor, although the rate of decrease is different, it gradually begins to decrease from around 500 nm, deteriorates from 450 nm, deteriorates rapidly from 430 nm, and hardly transmits at 380 nm. It was. This region exactly matches the short wavelength region of the fluorescence spectrum of the ZnS: Ag phosphor.

  For this reason, in the present invention, a dye which is a wavelength converting agent is added to the scintillator, and the fluorescence in the wavelength region that suddenly deteriorates from 430 nm and hardly transmits at 380 nm has a wavelength in the wavelength region of 440 nm or more with good transmittance. The amount of fluorescence that reaches the surface of the scintillator is increased by increasing the amount of fluorescence that reaches the surface of the scintillator by making it easier to transmit through the inside of the scintillator. This method is particularly effective when the thickness of the translucent neutron scintillator is increased, and is particularly effective when neutrons cause a capture reaction with the neutron converter in the back and emit light. On the other hand, in the case of light emission in the vicinity of the surface of the scintillator, the amount of fluorescence guided to the surface is large because there is little absorption by the scintillator itself, and the amount of fluorescence required for detecting neutrons is secured.

  The wavelength conversion agent used has an absorption spectrum that matches the alpha-sensitive spectrum of the ZnS-based phosphor as much as possible, and that the spectrum after wavelength conversion can be as high as the wavelength with the highest quantum efficiency of the photodetector that detects fluorescence. It is preferable that they are close. Further, the quantum efficiency of the wavelength conversion agent is preferably as high as possible, and is preferably 50% or more, more preferably 80% or more.

The addition amount of the wavelength conversion agent has an optimum amount that varies depending on the combination of the ZnS-based phosphor, the neutron converter, and the dye used as the wavelength conversion agent. For example, when a ZnS phosphor for particle beam detection with an alpha ray detection ratio of 0.63 and a ⁶ LiF neutron converter are used, the optimum range is 0.125 wt% to 0.75 wt% when the dye is BisMSB. When using a ZnS phosphor for particle beam detection with an alpha ray detection ratio of 0.51 and a ⁶ LiF neutron converter, the optimum range is from 0.25 wt% to 1.0 wt% when the dye is anthracene. When a conventional P11 type ZnS phosphor 1109-041 phosphor and a ⁶ LiF neutron converter are used, the optimum range is 0.5 wt% to 1.5 wt% when the dye is BisMSB. In addition, when using a 1055-152 phosphor which is a ZnS: Ag, Al type phosphor and a ⁶ LiF neutron converter, the optimum range is 1.5 wt% to 2.5 wt% when the dye is BisMSB. On the other hand, when a ZnS phosphor for particle beam detection with an alpha ray detection ratio of 0.51 and a ¹⁰ B neutron converter are used, the optimum range is 0.075 wt% to 0.15 wt% when the dye is BisMSB.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. In the following examples, the measurement of the fluorescence spectrum obtained by irradiating with alpha rays and gamma rays was performed under the equipment and conditions shown below.
Measuring device: Hitachi Ltd. spectrofluorometer F-2500
Fluorescent slit: fixed at 20 nm. For this reason, the fluorescence intensity in alpha ray irradiation and the fluorescence intensity in gamma ray irradiation are the same unit.
Radiation source for alpha irradiation: ²⁴¹ Am alpha source (diameter 5 mmφ, source intensity: about 1 MBq) manufactured by Amersham, UK
Radiation source for gamma-ray irradiation: The same ²⁴¹ Am alpha-ray source (diameter 5 mmφ, radiation source intensity: about 1 MBq) is attached with an alpha-ray shield consisting of four aluminum foils (thickness 12 μm) and irradiated with 60 keV gamma rays.
In addition, the transmittance characteristics of the ZnS phosphor and the neutron converter were measured under the following equipment and conditions.
Measuring apparatus: Hitachi Ltd. spectrophotometer U-3300
Lamp: Tungsten lamp only Resolution: 1 nm
Measurement range: 300nm-700nm
[Example 1]
Among the fluorescence generated from the ZnS phosphor in the scintillator by adding a dye as a wavelength conversion agent to the translucent neutron scintillator composed of ZnS phosphor and ⁶ LiF which is a neutron converter, and adding a dye as a wavelength conversion agent to the scintillator ZnS / ⁶ LiF translucent neutron with improved detection efficiency for neutrons by converting the wavelength of fluorescent light in the short wavelength spectrum where the transmittance of the ZnS phosphor decreases into a long wavelength region with good transmittance and transmitting it through the scintillator The scintillator will be described.

  As the ZnS phosphor, a particle beam detection ZnS: Ag phosphor having an alpha ray detection ratio of 0.63 was used. A ZnS: Ag phosphor for particle beam detection having an alpha ray detection ratio of 0.63 was manufactured by the following process.

  For 50 g of zinc sulfide having a center particle size of 8 μm, silver nitrate equivalent to 0.015% of the weight of zinc sulfide, lithium chloride equivalent to 6% of the weight of zinc sulfide, and 0.175 of the weight of zinc sulfide. % Of strontium sulfide corresponding to% was added, 20 cc of distilled water was added and mixed, and then dried.

Graphite crucible (outside is 60 mmφ, length is 50 mm, inside is 30 mmφ, bottom thickness is 10 mm, top lid thickness is 10 mm, volume for material is 30 mmφ, length is 30 mm, center of top lid is The dried baked material was put in a hole in which a part of the sublimate generated from the baked material was released in step 1), and then the upper lid was closed and baked in an electric furnace. An electric furnace KDF-S70 type manufactured by Denken Co., Ltd. was used as the electric furnace. Firing was performed under the following conditions.
Firing temperature: 820 ° C
Cover gas: Firing time of flowing CO ₂ at 2 liters / minute: 2 hours After the fired sintered product was powdered, it was washed with water to obtain a ZnS: Ag phosphor for particle beam detection.

  The fluorescence characteristics of the ZnS: Ag phosphor for particle beam detection with respect to alpha ray irradiation and gamma ray irradiation were examined. Samples for measuring fluorescence characteristics were coated with Nitoms double-sided tape on a microscope cover glass (size: 18 mm x 18 m, thickness 0.15 mm) and then coated with powder of ZnS: Ag phosphor for particle beam detection on one side. did. By this operation, almost one layer of ZnS: Ag phosphor particles can be applied to one side of the double-sided tape. When this method is used, the measurement error with respect to the amount of fluorescence (integrated value of the fluorescence intensity of the fluorescence spectrum) with respect to irradiation with alpha rays is ± 10%.

  The measurement sample was placed at the sample position of the excitation light irradiation system of the fluorometer, and the fluorescence spectrum was measured by alpha ray irradiation and gamma ray irradiation.

  The obtained fluorescence spectrum obtained by normalizing the alpha-ray-irradiated fluorescence spectrum of the obtained ZnS: Ag phosphor added with 0.175% strontium sulfide and the gamma-ray-irradiated fluorescence spectrum obtained by gamma-ray irradiation with the maximum value as 1, respectively. Then, by subtracting the gamma ray irradiation fluorescence spectrum from the alpha ray irradiation fluorescence spectrum, the alpha ray sensitive fluorescence spectrum was obtained, and these three types of fluorescence spectra obtained are shown in FIG.

  From FIG. 24, an alpha-sensitive fluorescence spectrum having a peak wavelength of 395 nm to 410 nm with a fluorescence spectrum of 320 nm to 580 nm emitted when irradiated with alpha rays, and 380 nm emitted when irradiated with gamma rays or electron beams. In a silver activated zinc sulfide (ZnS: Ag) phosphor for particle beam detection showing a synthesized fluorescence spectrum, a gamma ray sensitive fluorescence spectrum corresponding to a fluorescence spectrum having a peak wavelength of 435 nm to 450 nm in a fluorescence spectrum extending up to 560 nm The ratio of the intensity of the gamma ray sensitive fluorescence spectrum (alpha ray detection ratio) to the intensity of the total fluorescence spectrum obtained by adding the alpha ray sensitive fluorescence spectrum and the gamma ray sensitive fluorescence spectrum was 0.63. there were.

  For comparison, the alpha-irradiated fluorescence spectrum of the particle beam detection ZnS: Ag phosphor is shown in FIG. 4 together with the fluorescence spectrum of the 1109-041 phosphor manufactured by Nichia Corporation, which is a conventional P11 type ZnS: Ag phosphor. Show. It can be clearly seen that the short wavelength component of the present particle beam detection ZnS: Ag phosphor is increased as compared with the conventional P11 phosphor. BisMSB (1,4-Bis (2-methylstyryl) benzene: 1,4-bis (2-methylstyryl) benzene) was used as a wavelength conversion agent (dye) having an absorption spectrum suitable for this short wavelength component. BisMSB has a very high conversion efficiency of 94% quantum efficiency.

  FIG. 5 shows a fluorescence spectrum of a ZnS: Ag phosphor for particle beam detection having an alpha ray detection ratio of 0.63, and an absorption spectrum and a wavelength-converted fluorescence spectrum of BisMSB. The absorption spectrum of BisMSB has a peak at 410 nm and absorbs well in the range of 350 nm to 435 nm (FWHM). The absorption spectrum of BisMSB is in good agreement with the fluorescence spectrum of the ZnS: Ag phosphor. On the other hand, the wavelength-converted fluorescence spectrum of BisMSB has a peak at 450 nm, and shows that the wavelength-converted fluorescence spectrum is in the range of 440 nm to 475 nm (FWHM).

  Using the fluorescence spectrum and transmittance characteristics of the ZnS: Ag phosphor for particle beam detection and the absorption spectrum and wavelength conversion fluorescence spectrum of BisMSB, the fluorescence yield of the phosphor alone and the fluorescence when the wavelength conversion agent is added to the phosphor Yield can be evaluated. The evaluation calculation is performed according to the following procedure.

  The fluorescence intensities of all wavelengths in the fluorescence spectrum of the particle beam detection ZnS: Ag phosphor are integrated, and the integrated value is set to 1 to normalize the fluorescence intensities at the respective wavelengths. As for the transmittance characteristic, the transmittance at all wavelengths is normalized by setting the transmittance at 700 nm to 1. By multiplying the normalized fluorescence intensity for each wavelength by the normalized transmittance and integrating for all wavelengths, the fluorescence yield of only the phosphor can be obtained.

  On the other hand, when a wavelength conversion agent is added, first, the fluorescence intensities of all wavelengths in the fluorescence spectrum are integrated, and the integrated value is set to 1, and the fluorescence intensities at the respective wavelengths are normalized. Next, the absorption spectrum and wavelength-shifted fluorescence intensity of BisMSB are normalized with the maximum value of each spectrum as 1, and the absorption rate and wavelength-shifted fluorescence intensity of each wavelength are normalized. For each wavelength, the normalized fluorescence intensity and the normalized absorption intensity are multiplied and integrated for all wavelengths to obtain the yield at which the fluorescence of the phosphor is absorbed by BisMSB. When the fluorescence wavelength is long and not absorbed by the wavelength conversion agent, the normalized fluorescence intensity for each wavelength is multiplied by the normalized transmittance and integrated for wavelengths after 440 nm where the BisMSB absorption hardly disappears. It is possible to obtain the fluorescence yield of only the phosphor in the wavelength region where there is no light. Next, by multiplying the normalized wavelength shift fluorescence intensity of BisMSB and the normalized transmittance for each wavelength and integrating for wavelengths of 440 nm and later, wavelength conversion is performed when BisMSB is added to the phosphor. Fluorescence yield can be determined.

  The yield of fluorescence when a wavelength conversion agent is added to the phosphor is the yield in which the fluorescence of the phosphor is absorbed by BisMSB, the quantum efficiency of BisMSB 0.94, the yield of wavelength-converted fluorescence, Can be obtained by adding the yield of fluorescence of only the phosphor in the wavelength region where there is no BisMSB absorption.

  As a result of the above evaluation calculation, the case where BisMSB is not added to the ZnS: Ag phosphor for particle beam detection whose alpha ray detection ratio is 0.63 and the yield when added are 0.544 and 0.670, respectively. there were. It was possible to obtain an evaluation result that the fluorescence yield increased by about 0.13 in absolute value and about 23% as a relative value. This evaluation is an evaluation that takes into account only the absorption effect of the ZnS phosphor, and as described above, the difference in the fluorescence yield is further increased when the absorption effect by the neutron converter is added.

[Example 2]
Next, ⁶ LiF is added to the ZnS: Ag phosphor for particle beam detection whose alpha ray detection ratio is actually 0.63, and the addition amount of BisMSB which is a wavelength conversion agent is added to the adhesive. In addition, an experiment was performed to obtain an optimum amount of the wavelength converting agent using a ZnS / ⁶ LiF translucent neutron scintillator prepared by mixing and applying to a substrate.

^{As 6} LiF, 90% ⁶ Li-concentrated ⁶ LiF manufactured by APPLIED CHEMISTRY was used, and this ⁶ LiF was finely powdered, and the average particle size was 3 μm. As the adhesive, SU Premium [Soft] manufactured by Konishi Co., Ltd. was used. Moreover, the lacquer thin liquid S was used as a solvent which melt | dissolves this adhesive agent. BisMSB (dye) manufactured by Kanto Chemical Co., Ltd. was used as the wavelength conversion agent.

  First, 80 mg of an adhesive was put into a pottery crucible having a volume of 30 cc, and after adding 600 mg of lacquer thin solution S, ultrasonic waves were applied for 3 minutes with an ultrasonic cleaner to dissolve it to obtain an adhesive solution. As the ultrasonic cleaner, a W-113 type ultrasonic cleaner (frequency 45 kHz, output 100 W) manufactured by Honda Electronics Co., Ltd. was used.

To this adhesive solution, the weight ratio of ZnS: Ag phosphor for particle beam detection and ⁶ LiF was set to 1: 1, 900 mg of ZnS: Ag phosphor for particle beam detection and 600 mg of ⁶ LiF were added, followed by ultrasonic cleaning. Mix by adding ultrasonic for 3 minutes. A total of 15 types of samples were prepared when no wavelength conversion agent was added to this mixed solution and when 14 types of wavelength conversion agents having different weights were added. After adding the wavelength converting agent, ultrasonically applied for 3 minutes with an ultrasonic cleaner, mixed, applied to an aluminum substrate of 5 cm x 5 cm x 0.3 mm (thickness), dried and solidified to produce 15 types ZnS / ⁶ LiF translucent neutron scintillator samples 1-15 were fabricated. The weights of the 14 types of wavelength converting agents were 0.06 wt%, 0.13 wt%, 0.25 wt%, 0 with respect to a total weight of 1200 mg including 900 mg of ZnS: Ag phosphor for particle beam detection and 600 mg of ⁶ LiF, respectively. 0.5 wt%, 0.75 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%. As a result of measuring the thickness of these ZnS / ⁶ LiF translucent neutron scintillators after fabrication, all were about 280 μm.

About 15 types of semi-transparent ^ZnS / 6 LiF converter neutron scintillator samples 1 to 15 was produced, using a Am-Li-ray source 7.4GBq as neutron sources, it was measured detection characteristics with thermalized in paraffin blocks 5cm thickness.

The pulse signal obtained when the translucent ZnS / ⁶ LiF neutron scintillator was irradiated with neutrons was measured with an oscilloscope, and the detection characteristics for neutrons were measured. A neutron signal was detected by placing a photomultiplier tube on one side of the scintillator sample. R1924A manufactured by Hamamatsu Photonics was used as the photomultiplier tube, and it was used at an applied voltage of 1000V. The obtained neutron fluorescence signal was subjected to waveform data collection using an LT344 type oscilloscope manufactured by LeCroy. As collection conditions, vertical sensitivity was set to 100 mV / div, time sensitivity was set to 1 μs / div, and trigger level was set to 32 mV, and measurement was performed at a sampling frequency of 500 MHz.

The detection efficiency for thermal neutrons is determined by examining the time stamp recorded at the time of acquisition of each pulse signal waveform, deriving the count rate by obtaining the number of pulse signal waveforms acquired within a certain time, and then the detection efficiency is known ^It calculated | required by performing a relative comparison with the count rate of a 6Li glass scintillator.

In order to investigate the influence of decay time and afterglow based on the obtained signal, the fluorescence lifetime characteristics were analyzed. Since it is said that the decay time corresponding to a short component of ZnS: Ag phosphor is 1 μs or less, the value corresponds to 0.632 times (corresponding to 1-e ⁻¹ ) of the total signal voltage obtained by integrating up to 1 μs. The elapsed time when the integrated signal voltage reached is defined as “short decay time”. Then, the elapsed time when the integrated signal voltage reaches the value corresponding to 0.632 times the total signal voltage obtained by integration up to 8 μs (corresponding to 1-e ⁻¹ ) is set as the “long time”. It was defined as “decay time”. In the present embodiment, when the decay time is described, a short decay time is indicated.

For the 13 types of translucent ZnS / ⁶ LiF converter neutron scintillators, the detection efficiency and decay time for neutrons were determined by the above-described characteristic tests. FIG. 6 shows changes in detection efficiency and decay time for neutrons when the weight of the wavelength conversion agent is changed. From the results of detection efficiency with respect to neutrons, it was found that the best detection efficiency of 28.3% was obtained when the weight of the wavelength conversion agent was 0.25 wt%. Since the effect of the wavelength conversion agent has already been obtained even when the weight is extremely low, 0.06 wt%, the case of the ZnS: Ag phosphor for particle beam detection having an alpha ray detection ratio of 0.63 is very high. It was found that the maximum effect was obtained with a small amount of wavelength converting agent.

  Further, since the detection efficiency in the case where no wavelength converting agent was added was 24.1%, the absolute value was improved by 4.2%, and the ratio was improved by 17%.

  As a result of the detection efficiency for neutrons, an evaluation calculation result for evaluating the fluorescence yield of only the phosphor described above and the fluorescence yield when a wavelength conversion agent is added to the phosphor is about 17 This is a result of the fact that the fluorescence emitted in the back of the scintillator can be detected as a neutron signal corresponding to the increase in the yield of% fluorescence.

  On the other hand, when the result of the decay time with respect to the change in the wavelength of the wavelength conversion agent was examined, the weight of the wavelength conversion agent was once reduced at 0.125 wt% and 0.25 wt%, which was 0.26 μs, as in the case of detection efficiency. After that, it was found that after becoming a little longer, it gradually became shorter as the weight of the wavelength converting agent increased. Since the decay time when no wavelength conversion agent was added was 0.28 μs, the absolute value was improved by 0.02 μs. From this result, it can be seen that when the weight of the wavelength converting agent is 0.25 wt%, the effect of the wavelength converting agent is greatly effective, thereby increasing the amount of fluorescence in the short wavelength component region and shortening the decay time.

  Regarding the influence of the afterglow, a comparison was made in the long decay time, which is a measure of the afterglow, when the wavelength conversion agent was not added and when the weight of the wavelength conversion agent was added at 0.25 wt%. As a result, it was found that the long decay time when the wavelength conversion agent was not added was 1.33 μs, and that when the wavelength conversion agent was added, the time was shortened to 1.09 μs, and the influence of afterglow was also improved.

In addition, since the total signal voltage obtained by integrating up to 1 μs is proportional to the amount of fluorescence emitted during the time of 1 μs, the total signal voltage of the ⁶ Li glass scintillator in which the photon emission amount is known in advance is used. The number of photons was obtained for each neutron signal. The number of photons ^{distribution ZnS} / 6 LiF translucent neutron scintillator was added by weight 0.25 wt% of the wavelength conversion agent is released, without the addition ^ZnS / 6 LiF translucent neutron scintillator, and commercially available AST Inc. ZnS / FIG. 7 shows a comparison with the photon number distribution of a ⁶ LiF translucent neutron scintillator. From this result, the photon number distribution of the ZnS / ⁶ LiF translucent neutron scintillator produced without addition is shown although there is a peak in the region where the photon number is slightly smaller than the photon number distribution of the conventional AST scintillator. Was found to be obtained.

  Furthermore, it has been found that the average photon emission amount of 1 μs is a little less than 22300 photons / pulse, compared to 24700 photons / pulse in the conventional AST scintillator.

[Example 3]
Of the fluorescence generated from the ZnS phosphor in the scintillator in the semitransparent neutron scintillator combined with the ¹⁰ B neutron converter using the ZnS: Ag phosphor for particle beam detection as the ZnS phosphor, the ZnS phosphor Adds a dye, which is a wavelength conversion agent, to the scintillator for the fluorescence in the short wavelength spectral region where the transmittance of the light decreases, converts the wavelength to a long wavelength region with good transmittance, and transmits it through the scintillator to increase the detection efficiency for neutrons A ZnS / ¹⁰ B neutron converter translucent neutron scintillator will be described.

The ZnS / ¹⁰ B neutron converter translucent neutron scintillator was manufactured by the following method.

¹⁰ B prepared by mixing and polymerizing a mixed solution of ¹⁰ B concentrated boric acid, modified alicyclic polyamine, and water and ethyl alcohol having a 90 B isotope concentration of 90% or more, and then adding blending medium to prepare ¹⁰ A B-containing transparent adhesive substance was used as a neutron converter / adhesive and mixed with a ZnS: Ag phosphor to produce a translucent ZnS / ¹⁰ B converter neutron scintillator.

  As the ZnS phosphor, a particle beam detection ZnS: Ag phosphor having an alpha ray detection ratio value of 0.51 times was used. The ZnS: Ag phosphor for particle beam detection having an alpha ray detection ratio of 0.51 was manufactured by the following process.

For 50 g of zinc sulfide having a center particle size of 8 μm, silver nitrate corresponding to 0.015% of the weight of zinc sulfide, lithium chloride corresponding to 6% of the weight of zinc sulfide, and 0.12 of the weight of zinc sulfide. % Strontium sulfide corresponding to%, 20 cc of distilled water was added and mixed, and then dried. Graphite crucible (outside is 60 mmφ, length is 50 mm, inside is 30 mmφ, bottom thickness is 10 mm, top lid thickness is 10 mm, volume for material is 30 mmφ, length is 30 mm, center of top lid is And 1 mmφ hole for releasing a part of the sublimate generated from the fired material was put in, and then the upper lid was closed and fired in an electric furnace. An electric furnace KDF-S70 type manufactured by Denken Co., Ltd. was used as the electric furnace. Firing was performed under the following conditions.
Firing temperature: 820 ° C
Cover gas: Firing time of flowing CO ₂ at 2 liters / minute: 2 hours After the fired sintered product was powdered, it was washed with water to obtain a ZnS: Ag phosphor for particle beam detection.

  The fluorescence characteristics of the ZnS: Ag phosphor for particle beam detection with respect to alpha ray irradiation and gamma ray irradiation were examined. Samples for measuring fluorescence characteristics were coated with Nitoms double-sided tape on a microscope cover glass (size: 18 mm x 18 m, thickness 0.15 mm) and then coated with powder of ZnS: Ag phosphor for particle beam detection on one side. did. By this operation, almost one layer of ZnS: Ag phosphor particles can be applied to one side of the double-sided tape. When this method is used, the measurement error with respect to the amount of fluorescence (integrated value of the fluorescence intensity of the fluorescence spectrum) with respect to irradiation with alpha rays is ± 10%.

  The measurement sample was placed at the sample position of the excitation light irradiation system of the fluorometer, and the fluorescence spectrum was measured by alpha ray irradiation and gamma ray irradiation.

  The obtained fluorescence spectrum obtained by normalizing the alpha-ray-irradiated fluorescence spectrum of the obtained ZnS: Ag phosphor added with 0.12% strontium sulfide and the gamma-ray-irradiated fluorescence spectrum obtained by gamma-ray irradiation with the maximum value as 1, respectively. Then, by subtracting the gamma ray irradiation fluorescence spectrum from the alpha ray irradiation fluorescence spectrum, an alpha ray sensitive fluorescence spectrum was obtained, and these three types of fluorescence spectra obtained are shown in FIG.

  From FIG. 25, an alpha-sensitive fluorescence spectrum having a peak wavelength of 395 nm to 410 nm with a fluorescence spectrum of 320 nm to 580 nm emitted upon irradiation with alpha rays, and 380 nm emitted upon irradiation with gamma rays or electron beams. In a silver activated zinc sulfide (ZnS: Ag) phosphor for particle beam detection showing a synthesized fluorescence spectrum, a gamma ray sensitive fluorescence spectrum corresponding to a fluorescence spectrum having a peak wavelength of 435 nm to 450 nm in a fluorescence spectrum extending up to 560 nm The intensity ratio (alpha ray detection ratio) of the gamma ray sensitive fluorescence spectrum was 0.51 with respect to the intensity of the total fluorescence spectrum obtained by adding the alpha ray sensitive fluorescence spectrum and the gamma ray sensitive fluorescence spectrum.

  FIG. 8 shows the fluorescence spectrum and transmittance characteristics of the present ZnS: Ag phosphor for particle beam detection. It can be seen that the deterioration of the transmittance starts around 450 nm, suddenly worsens as the fluorescence wavelength becomes shorter, and does not transmit around 390 nm. Further, it is well understood from the fluorescence spectrum that the short wavelength component of the present particle beam detection ZnS: Ag phosphor is increased.

  As the wavelength converting agent, BisMSB was used as a wavelength converting agent (dye) having an absorption spectrum suitable for this short wavelength component.

  FIG. 9 shows a fluorescence spectrum of a particle beam detection ZnS: Ag phosphor having an alpha ray detection ratio of 0.51, a BisMSB absorption spectrum, and a wavelength-converted fluorescence spectrum. The absorption spectrum of BisMSB has a peak at 410 nm and absorbs well in the range of 350 nm to 435 nm (FWHM). Therefore, the absorption spectrum of BisMSB is in good agreement with the fluorescence spectrum of the ZnS: Ag phosphor.

^{As 10} B concentrated boric acid, 96% ¹⁰ B concentrated boric acid manufactured by Stella Chemifa Co. was used, and the ¹⁰ B concentrated boric acid was pulverized, and the average particle size was 1.6 μm. For the modified alicyclic polyamine of the epoxy curing agent, an 80 minute curing agent which is a modified alicyclic polyamine type curing agent for the main agent Z-1 manufactured by Nissin Resin Co., Ltd. was used.

After ¹⁰ B a mixture of concentrated boric acid 500 mg, 80 minutes curing agent 130mg and water 200mg methyl alcohol 200mg were mixed and polymerized, particle beam ¹⁰ B containing translucent adhesive material prepared by mixing the addition of blending medium 1250 mg of ZnS: Ag phosphor for detection was added and mixed.

A total of nine types of samples were prepared when no wavelength conversion agent was added to this mixed solution and when eight types of weights of wavelength conversion agent were added. As the wavelength converting agent, BisMSB was used as a wavelength converting agent (dye) having an absorption spectrum suitable for this short wavelength component. After adding the wavelength converting agent, ultrasonic waves were applied for 3 minutes with an ultrasonic cleaner, mixed, applied to an aluminum substrate of 5 cm × 5 cm × 0.3 mm (thickness), dried and solidified to obtain 8 types. A translucent ZnS / ¹⁰ B converter neutron scintillator was fabricated. The weights of the eight wavelength conversion agents were 0.05 wt% and 0%, respectively, based on a total weight of 1880 mg including ¹⁰ B concentrated boric acid 500 mg, 80 minute curing agent 130 mg and particle beam detection ZnS: Ag phosphor 1250 mg. 0.075 wt%, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, and 0.5 wt%.

As a result of measuring the thickness of these translucent ZnS / ¹⁰ B converter neutron scintillators after fabrication, all were about 350 μm.

About the produced nine types of translucent ZnS / ¹⁰ B converter neutron scintillators, Am-Li radiation source 7.4 GBq was used as a neutron radiation source, and thermal neutronization was performed with a paraffin block of 5 cm thickness, and detection characteristics were measured. The measurement method of the detection characteristic was the same as the measurement method described in Example 1.

With respect to nine types of translucent ZnS / ¹⁰ B converter neutron scintillators, the detection efficiency and decay time for neutrons were determined by the above characteristic tests. FIG. 10 shows changes in detection efficiency and decay time for neutrons when the weight of the wavelength conversion agent is changed. As for the detection efficiency for neutrons, it was found that the best detection efficiency was 23.2% when the weight of the wavelength conversion agent was 0.075 wt%. Since the detection efficiency when no wavelength converting agent was added was 18.2%, the detection efficiency increased by 5% in absolute value, and increased by 27% in relative value.

From this result, in the same manner as when ⁶ LiF of Example 1 was used as a neutron converter, even when a ¹⁰ B neutron converter was used, ZnS: Ag fluorescence for particle beam detection with an alpha ray detection ratio of 0.51 was obtained. In the case of the body, it was found that the effect can be obtained with a very small amount of the wavelength converting agent.

  On the other hand, when the result of the decay time with respect to the change in the weight of the wavelength conversion agent was examined, the wavelength conversion agent was shortened once at 0.075 wt%, which was 0.256 μs, and then once again, as in the case of detection efficiency. It was found that the weight of the post-wavelength converting agent gradually decreased with an increase. Since the decay time when no wavelength conversion agent was added was 0.261 μs, the absolute value was improved by 0.005 μs.

[Example 4]
Among semi-transparent neutron scintillators using a P11 type ZnS: Ag, Cl phosphor as the ZnS phosphor and ⁶ LiF as the neutron converter, among the fluorescence generated from the ZnS phosphor in the scintillator when neutrons are incident, ZnS fluorescence Fluorescence in the short wavelength spectral region where the transmittance of the body is reduced Adds a dye that is a wavelength conversion agent to the scintillator, converts the wavelength to a long wavelength region with good transmittance, and transmits the scintillator to improve the detection efficiency for neutrons The raised ZnS / ⁶ LiF translucent neutron scintillator will be described.

  As the ZnS phosphor, a 1109-041 phosphor manufactured by Nichia Corporation, which is a P11 type ZnS: Ag, Cl phosphor, was used.

  A ZnS: Ag, Cl phosphor represented by P11 has a low fluorescence in a short wavelength region ranging from 350 nm to 450 nm, and an alpha ray detection ratio is 0.29. However, the color of the phosphor is white.

  FIG. 11 shows the fluorescence spectrum and transmittance characteristics of the 1109-041 phosphor. As a result, it can be seen that the deterioration of the transmittance starts from around 450 nm, suddenly worsens as the fluorescence wavelength becomes shorter, and does not transmit around 390 nm. Further, it is well understood from the fluorescence spectrum that the short wavelength component of the ZnS: Ag, Cl phosphor is small. BisMSB was used as a wavelength conversion agent having an absorption spectrum suitable for this short wavelength component.

  FIG. 12 shows the fluorescence spectrum of the 1109-041 phosphor, the absorption spectrum of BisMSB, and the wavelength-converted fluorescence spectrum. The absorption spectrum of BisMSB has a peak at 410 nm and absorbs well in the range of 350 nm to 435 nm (FWHM). Therefore, the absorption spectrum of BisMSB closely matches the bulging wavelength region of the short wavelength side fluorescence spectrum of the 1109-041 phosphor.

ZnS / ⁶ LiF translucent neutron scintillator prepared by adding ⁶ LiF to a 1109-041 phosphor, adding a different amount of BisMSB, which is a wavelength conversion agent, and then mixing with an adhesive and applying to a substrate An experiment was conducted to determine the optimum amount of wavelength converting agent to be used.

^{As 6} LiF, 90% ⁶ Li-concentrated ⁶ LiF made in Russia was used. This ⁶ LiF was pulverized, and the average particle size was 3 μm. As an adhesive, SU Premium [Soft] manufactured by Konishi Co., Ltd. was used. Moreover, Asahi Pen Co., Ltd. lacquer thin solution S (lacquer thinner) was used as a solvent for melting the adhesive. BisMSB manufactured by Kanto Chemical Co., Ltd. was used as the wavelength converting agent.

  First, 80 mg of the adhesive was put into a ceramic pot with a capacity of 30 cc, and after adding 800 mg of lacquer thin solution S, ultrasonic was applied for 3 minutes with an ultrasonic cleaner to dissolve it to obtain an adhesive solution. As the ultrasonic cleaner, a W-113 type ultrasonic cleaner (frequency 45 kHz, output 100 W) manufactured by Honda Electronics Co., Ltd. was used.

In this solution, 1109-041 phosphor and ⁶ LiF were mixed at a weight ratio of 2: 1, 1200 mg of 1109-041 phosphor and 600 mg of ⁶ LiF were added, and then ultrasonically added for 3 minutes with an ultrasonic cleaner. To do. A total of 11 types of samples were prepared when no wavelength conversion agent was added to the mixed solution and when 10 types of weight conversion agents were added. After adding the wavelength conversion agent, ultrasonic waves were applied for 3 minutes with an ultrasonic cleaner and mixed, then applied to an aluminum substrate of 5 cm × 5 cm × 0.3 mm (thickness), dried and solidified to be 11 types. A ZnS / ⁶ LiF translucent neutron scintillator sample was fabricated. The weights of the 10 types of wavelength conversion agents were 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, and 2.5 wt%, respectively, based on a total weight of 1800 mg including 1200 mg of 1109-041 phosphor and 600 mg of ⁶ LiF. 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, and 5 wt%.

As a result of measuring the thickness of these ZnS / ⁶ LiF translucent neutron scintillators after fabrication, all were about 350 μm.

About 11 types of produced ZnS / ⁶ LiF translucent neutron scintillators, Am-Li radiation source 7.4GBq was used as a neutron radiation source, and thermal neutronization was performed with a paraffin block of 5 cm thickness, and detection characteristics were measured. The measurement method of the detection characteristic was the same as the measurement method described in Example 1.

For eleven types of ZnS / ⁶ LiF translucent neutron scintillators, the detection efficiency and decay time for neutrons were determined by the above-described characteristic tests. FIG. 13 shows changes in detection efficiency and decay time for neutrons when the weight of the wavelength conversion agent is changed. As for the detection efficiency for neutrons, it was found that the best detection efficiency of 28.2% was obtained when the weight of the wavelength conversion agent was 1 wt%. Since the detection efficiency when no wavelength conversion agent was added was 23.6%, the detection efficiency increased by 4.6% in absolute value and increased by 20% in relative value.

  On the other hand, when the result of the decay time with respect to the change in the weight of the wavelength conversion agent is examined, it shows 0.392 μs when the weight of the wavelength conversion agent having the highest detection efficiency is 1 wt%, and 0.460 μs when no wavelength conversion agent is added. Therefore, it was found that the absolute value was improved by 0.068 μs. Thereafter, it was found that the weight of the wavelength converting agent gradually decreased with an increase, and was improved to 0.360 μs. It was found that the detection efficiency decreased even when the amount of the wavelength conversion agent added was increased, and was not improved much.

[Example 5]
In a translucent neutron scintillator using ZnS: Ag, Al phosphor as the ZnS phosphor and ⁶ LiF as the neutron converter, among the fluorescence generated from the ZnS phosphor in the scintillator when neutrons are incident, the ZnS phosphor Increasing the detection efficiency for neutrons by adding a wavelength conversion agent dye to the scintillator to convert the fluorescence in the short wavelength spectral region where the transmittance decreases into the scintillator, and converting the wavelength into a long wavelength region with good transmittance, and transmitting the scintillator. A ZnS / ⁶ LiF translucent neutron scintillator will be described.

  As the ZnS phosphor, a 1055-152 phosphor manufactured by Nichia Corporation, which is a ZnS: Ag, Al phosphor, was used. FIG. 14 shows the fluorescence spectrum of the ZnS: Ag, Al phosphor and the transmittance characteristics of the phosphor. The color of the phosphor is white.

  The characteristics of the ZnS: Ag, Al phosphor are found from the fluorescence spectrum shown in FIG. 14 that there is no rise in the fluorescence in the short wavelength range from 350 nm to 450 nm, and there is almost no alpha ray detection ratio. However, since the transmittance suddenly deteriorates from 440 nm and does not transmit at 390 nm, BisMSB was used as a wavelength conversion agent having an absorption spectrum in this wavelength region.

  The fluorescence spectrum of the 1055-152 phosphor, the absorption spectrum of BisMSB, and the wavelength converted fluorescence spectrum are shown in FIG. The absorption spectrum of BisMSB has a peak at 410 nm and absorbs well in the range of 350 nm to 435 nm (FWHM). Therefore, it can be seen that the absorption spectrum of BisMSB matches the partial wavelength region of the short wavelength side fluorescence spectrum of 1055-152 phosphor.

ZnS: ⁶ LiF translucent neutron produced by adding ⁶ LiF to a ZnS: Ag, Al phosphor, changing the addition amount of the wavelength conversion agent BisMSB, mixing with an adhesive, and applying to the substrate. An example in which an experiment for obtaining the optimum amount of addition of the wavelength conversion agent using a scintillator was conducted will be described.

^{As 6} LiF, 90% ⁶ Li-concentrated ⁶ LiF made in Russia was used. This ⁶ LiF was pulverized, and the average particle size was 3 μm. As the adhesive, SU Premium [Soft] manufactured by Konishi Co., Ltd. was used. Moreover, the lacquer thin liquid S was used as a solvent which melt | dissolves this adhesive agent. BisMSB manufactured by Kanto Chemical Co., Ltd. was used as the wavelength converting agent.

  First, 80 mg of an adhesive was put in a ceramic pot with a capacity of 30 cc, and after adding 600 mg of lacquer thin solution S, ultrasonic waves were applied for 3 minutes with an ultrasonic cleaner to dissolve it to obtain an adhesive solution. As the ultrasonic cleaner, a W-113 type ultrasonic cleaner (frequency 45 kHz, output 100 W) manufactured by Honda Electronics Co., Ltd. was used.

To this solution, ZnS: Ag, Al phosphor and ⁶ LiF weight ratio of 2: as 1, ZnS: Ag, was added to 1200mg and ⁶ LiF600mg Al phosphor, a 3 minutes ultrasound in an ultrasonic cleaner added And mix. A total of 11 types of samples were prepared when no wavelength conversion agent was added to the mixed solution and when 10 types of weight conversion agents were added. After adding the wavelength converting agent, ultrasonic waves were applied for 3 minutes with an ultrasonic cleaner and mixed, then applied to an aluminum substrate of 5 cm × 5 cm × 0.3 mm (thickness), dried and solidified to form 11 types of ZnS. / ^{6 A} LiF translucent neutron scintillator was fabricated. The weights of the ten types of wavelength conversion agents are 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, and 2. wt% with respect to a total weight of 1800 mg including ZnS: Ag, Al phosphor 1200 mg and ⁶ LiF 600 mg, respectively. 5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, and 5 wt%.

As a result of measuring the thickness of these ZnS / ⁶ LiF translucent neutron scintillators after fabrication, all were about 350 μm.

About 11 types of produced ZnS / ⁶ LiF translucent neutron scintillators, Am-Li radiation source 7.4GBq was used as a neutron radiation source, and thermal neutronization was performed with a paraffin block of 5 cm thickness, and detection characteristics were measured. The measurement method of the detection characteristic was the same as the measurement method described in Example 1.

With respect to eleven types of translucent ZnS / ⁶ LiF translucent neutron scintillators, the detection efficiency and decay time for neutrons were determined by the above-described characteristic tests. FIG. 16 shows changes in detection efficiency and decay time for neutrons when the weight of the wavelength conversion agent is changed. From the graph of detection efficiency for neutrons in FIG. 16, it was found that the best detection efficiency of 31.6% was obtained when the weight of the wavelength conversion agent was 2 wt%. Since the detection efficiency when no wavelength conversion agent was added was 26.3%, the detection efficiency increased by 5.3% in absolute value, and increased by 20% in relative value.

  On the other hand, when the result of the decay time with respect to the weight change of the wavelength conversion agent is examined, the weight of the wavelength conversion agent having the highest detection efficiency shows 0.450 μs when the weight is 2 wt%, and 0.475 μs when the wavelength conversion agent is not added. From this, it was found that the absolute value was improved by 0.025 μs. Thereafter, as the weight of the wavelength conversion agent increases, the decay time gradually decreases, the addition amount of the wavelength change agent is 4.5 wt%, the decay time is improved to 0.414 μs, and the detection efficiency is also 30.0%. It was found that it was improved.

[Example 6]
In a translucent neutron scintillator using a ZnS phosphor for particle beam detection with an alpha ray detection ratio value of 0.63 and using ⁶ LiF as a neutron converter, the fluorescence generated from the ZnS phosphor in the scintillator when neutrons are incident Among them, anthracene (7,12-dimethylbenz [a] anthracene) is added to the scintillator as a dye that is a wavelength conversion agent for the fluorescence in the short wavelength spectrum where the transmittance of the ZnS phosphor decreases. A ZnS / ⁶ LiF translucent neutron scintillator will be described in which the detection efficiency for neutrons is increased by converting the wavelength into a region and allowing the scintillator to pass through.

  As the ZnS phosphor, a particle beam detection ZnS: Ag phosphor having an alpha ray detection ratio value of 0.51 was used. The fluorescence spectrum and transmittance characteristics of the ZnS: Ag phosphor are shown in FIG. A characteristic of the ZnS: Ag phosphor is that the fluorescence in the short wavelength region extending from 350 nm to 450 nm has a high alpha ray detection ratio of 0.51. For this reason, the color of the phosphor is extremely light brown.

  In this example, anthracene (7,12-dimethylbenz [a] anthracene) was used as a wavelength conversion agent having an absorption spectrum suitable for this short wavelength component.

  FIG. 17 shows the fluorescence spectrum of the particle beam detection ZnS: Ag phosphor having an alpha ray detection ratio value of 0.51, the absorption spectrum of anthracene, and the wavelength-converted fluorescence spectrum. The absorption spectrum of anthracene has a peak at 407 nm and absorbs well in the range of 395 nm to 420 nm (FWHM). Therefore, it can be seen that the absorption spectrum of anthracene matches the wavelength region of the central portion of the short wavelength side fluorescence spectrum of the particle beam detecting ZnS: Ag phosphor.

  On the other hand, the wavelength-converted fluorescence spectrum of anthracene has large peaks at 424 nm and 445 nm, and shows that the wavelength spectrum is converted in the range of 418 nm to 450 nm (FWHM).

Using a ZnS / ⁶ LiF translucent neutron scintillator prepared by adding ⁶ LiF to the phosphor and changing the addition amount of anthracene, which is a wavelength converting agent, and then mixing with an adhesive and applying the mixture to a substrate. An experiment was conducted to determine the optimum amount of added wavelength converting agent.

^{As 6} LiF, 90% ⁶ Li-concentrated ⁶ LiF made in Russia was used. This ⁶ LiF was pulverized, and the average particle size was 3 μm. As an adhesive, SU Premium [Soft] manufactured by Konishi Co., Ltd. was used. Moreover, the lacquer thin liquid S was used as a solvent which melt | dissolves this adhesive agent. An anthracene (7,12-dimethylbenz [a] anthracene) manufactured by Kanto Chemical Co., Ltd. was used as the wavelength converting agent.

  First, 80 mg of an adhesive was put into a ceramic pot with a capacity of 30 cc, and after adding 600 mg of lacquer thin solution S, ultrasonic was applied for 3 minutes with an ultrasonic cleaner to dissolve it to obtain an adhesive solution. As the ultrasonic cleaner, a W-113 type ultrasonic cleaner (frequency 45 kHz, output 100 W) manufactured by Honda Electronics Co., Ltd. was used.

In this solution, ZnS: Ag phosphor for particle beam detection and ⁶ LiF are set to a weight ratio of 1: 1, and a ZnS: Ag phosphor for particle beam detection whose value of alpha ray detection ratio is 0.63 is 600 mg, ⁶ LiF 600 mg. Then, ultrasonic waves were added for 3 minutes with an ultrasonic cleaner to mix. A total of 13 types of samples were prepared when no wavelength conversion agent was added to this mixed solution and when 12 types of weights of wavelength conversion agent were added. After adding the wavelength conversion agent, ultrasonic waves were applied for 3 minutes with an ultrasonic cleaner and mixed, then applied to an aluminum substrate of 5 cm × 5 cm × 0.3 mm (thickness), dried and solidified to form 13 types. A ZnS / ⁶ LiF translucent neutron scintillator was fabricated. The weights of the 12 types of wavelength conversion agents were 0.25 wt%, 0.5 wt%, 0.75 wt%, and 1 wt, respectively, with respect to a total weight of 1200 mg including 600 mg of particle-detecting ZnS: Ag phosphor and 600 mg of ⁶ LiF. %, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%.

As a result of measuring the thickness of these ZnS / ⁶ LiF translucent neutron scintillators after fabrication, all were about 280 μm.

About the produced 13 types of ZnS / ⁶ LiF translucent neutron scintillators, Am-Li radiation source 7.4GBq was used as a neutron radiation source, and thermal neutronization was performed with a paraffin block of 5 cm thickness, and detection characteristics were measured. The measurement method of the detection characteristic was the same as the measurement method described in Example 1.

For the 13 types of translucent ZnS / ⁶ LiF translucent neutron scintillators, the detection efficiency and decay time for neutrons were determined by the above-described characteristic tests. FIG. 18 shows changes in detection efficiency and decay time for neutrons when the weight of the wavelength conversion agent is changed. From the detection efficiency for neutrons in FIG. 18, it was found that the best detection efficiency of 29.7% was obtained when the weight of the wavelength conversion agent was 0.25 wt%, which is the lowest. From this result, it was found that in the case of a ZnS: Ag phosphor for particle beam detection with an alpha ray detection ratio of 0.51, the maximum effect can be obtained with a very small amount of wavelength converting agent.

  Further, since the detection efficiency when no wavelength converting agent was added was 25.7%, the absolute value was improved by 4%, and the ratio was improved by 16%.

  On the other hand, when the result of the decay time with respect to the change in the weight of the wavelength conversion agent was examined, the weight of the wavelength conversion agent was reduced once at 0.25 wt% and 0.5 wt% as in the case of the detection efficiency, and showed 0.27 μs, It became clear that it became short gradually with the increase in the weight of a wavelength conversion agent after becoming once long after that. Since the decay time when no wavelength conversion agent was added was 0.29 μs, the absolute value was improved by 0.02 μs. From this result, it can be seen that the effect of the wavelength converting agent is greatly effective at 0.25 wt% where the weight of the wavelength converting agent is low, and the amount of fluorescence in the short wavelength component region is increased.

[Example 7]
An example of a translucent neutron scintillator in which the dye serving as the wavelength converting agent is POPOP (1,4-Bis (5-phenyl-2-oxazolyl) benzene) will be described.

  A ZnS: Ag phosphor for particle beam detection having an alpha ray detection ratio of 0.63 was used as the ZnS: Ag phosphor. The fluorescence spectrum and transmittance characteristics of this phosphor are shown in FIG. POPOP was used as a wavelength conversion agent having an absorption spectrum suitable for the short wavelength component of the ZnS: Ag phosphor for particle beam detection. FIG. 19 shows the absorption spectrum and wavelength conversion fluorescence spectrum of POPOP together with the fluorescence spectrum of the particle beam detection ZnS: Ag phosphor having an alpha ray detection ratio of 0.63. POPOP has a quantum efficiency of 93% and a very high conversion efficiency. The absorption spectrum of POPOP has a peak at 418 nm and absorbs well in the range of 380 nm to 435 nm (FWHM), and therefore agrees well with the fluorescence spectrum in the short wavelength region of the ZnS: Ag phosphor for particle beam detection. Further, it can be seen that the fluorescence spectrum of POPOP shows a fluorescence spectrum having a peak at 443 nm and wavelength-converted in the range of 435 nm to 480 nm (FWHM). The absorption spectrum and wavelength-converted fluorescence spectrum of the present dye are very similar to the BisMSB described above, but are characterized in that the peak wavelength of the wavelength-converted fluorescence spectrum is shortened by 7 nm.

  Using the fluorescence spectrum and transmittance characteristics of the particle beam detection ZnS: Ag phosphor with an alpha ray detection ratio of 0.63, and the POPOP absorption spectrum and wavelength conversion fluorescence spectrum, the fluorescence yield and fluorescence of the phosphor alone The fluorescence yield when a wavelength converting agent is added to the body can be evaluated. For the evaluation calculation, the method described in Example 1 was used.

  As a result of the above evaluation calculation, the yields when adding and not adding POPOP to the ZnS: Ag phosphor for particle beam detection with an alpha ray detection ratio of 0.63 were 0.544 and 0.609, respectively. It was. An evaluation result that the yield of fluorescence by about 12% increases as a ratio could be obtained. Compared to BisMSB results with similar characteristics, the improvement in fluorescence yield was about half. The cause is that the absorption spectrum of POPOP is depressed compared with BisMSB in the wavelength range of 380 nm to 410 nm. It can be seen that the effect of the present invention is obtained as the overlap with the spectrum of the ZnS phosphor increases when a dye is selected.

[Example 8]
Example of translucent neutron scintillator in which the wavelength conversion agent is coumarin 30 (7- (Diethylamino) -3- (1-methyl-1H-benzimidazol-2-yl) 2H-1-benzopyran-2-one) Will be described.

  A ZnS: Ag phosphor for particle beam detection having an alpha ray detection ratio of 0.63 was used as the ZnS: Ag phosphor. The fluorescence spectrum and transmittance characteristics of this phosphor are shown in FIG. Coumarin 30 was used as a wavelength conversion agent having an absorption spectrum suitable for the short wavelength component of the ZnS: Ag phosphor for particle beam detection. The absorption spectrum and wavelength conversion fluorescence spectrum of coumarin 30 are shown in FIG. 20 together with the fluorescence spectrum of the particle beam detection ZnS: Ag phosphor having an alpha ray detection ratio of 0.63. Coumarin 30 has a high conversion efficiency of 64%. The absorption spectrum of coumarin 30 has a peak at 410 nm and absorbs well in the range of 380 nm to 430 nm (FWHM), and therefore agrees well with the fluorescence spectrum in the short wavelength region of the ZnS: Ag phosphor for particle beam detection. Moreover, it turns out that the fluorescence spectrum of coumarin 30 shows the fluorescence spectrum by which wavelength conversion was carried out in the range of 460 nm to 520 nm (FWHM) with a peak of 480 nm.

  Using the fluorescence spectrum and transmittance characteristics of a ZnS: Ag phosphor for particle beam detection with an alpha ray detection ratio of 0.63, and the absorption spectrum and wavelength conversion fluorescence spectrum of coumarin 30, the fluorescence yield of the phosphor alone The fluorescence yield can be evaluated when a wavelength conversion agent is added to the phosphor. For the evaluation calculation, the method described in Example 1 was used.

  As a result of the above evaluation calculation, the yield when the coumarin 30 is not added to the ZnS: Ag phosphor for particle beam detection with an alpha ray detection ratio of 0.63 and when it is added are 0.54 and 0.57, respectively. there were. An evaluation result that the yield of fluorescence by about 5% increases as a ratio could be obtained. Actually, since the effect of absorption of the neutron converter is included, a better result can be obtained by adding a wavelength conversion agent.

[Example 9]
An example of a translucent neutron scintillator in which the dye that is the wavelength converting agent is 4-Dimethylamino-4-Nitrostilbene will be described.

A ZnS: Ag phosphor for particle beam detection having an alpha ray detection ratio of 0.63 was used as the ZnS: Ag phosphor. The fluorescence spectrum of this phosphor is shown in FIG. 4-Dimethylamino-4-nitrostilbene was used as a wavelength conversion agent having an absorption spectrum suitable for the short wavelength component of the ZnS: Ag phosphor for particle beam detection. 4-Dimethylamino-4-Nitrostilbene has a high conversion efficiency of 80%. FIG. 21 shows the absorption spectrum and wavelength-converted fluorescence spectrum of this dye together with the fluorescence spectrum of the particle beam detection ZnS: Ag phosphor having an alpha ray detection ratio of 0.63. The absorption spectrum of the present dye has a peak at 430 nm and absorbs well in the range of 380 nm to 470 nm (FWHM), and therefore agrees well with the wavelength region of the fluorescence spectrum of the particle beam detection ZnS: Ag phosphor. Further, it can be seen that the fluorescence spectrum of the present dye has a peak of 590 nm and shows a fluorescence spectrum that has been wavelength-converted in the range of 535 nm to 665 nm (FWHM). This wavelength region coincides with the region having the highest quantum efficiency of the SiAPD photodetector as described above.
Further, when used as a screen and combined with a CCD camera element as a radiography apparatus, it matches the region with the highest quantum efficiency of the CCD camera element.

  Using the fluorescence spectrum and transmittance characteristics of ZnS: Ag phosphor for particle beam detection and the absorption spectrum and wavelength conversion fluorescence spectrum of 4-Dimethylamino-4-Nitrostilbene, the fluorescence yield of the phosphor alone and the wavelength conversion to the phosphor The yield of fluorescence when an agent is added can be evaluated. For the evaluation calculation, the method described in Example 1 was used.

  As a result of the above evaluation calculation, the yield in the case where 4-Dimethylamino-4-Nitrostilbene is not added to the ZnS: Ag phosphor for particle beam detection whose alpha ray detection ratio is 0.63 is 0.54 respectively. And 0.57. An evaluation result that the yield of fluorescence by about 5% increases as a ratio could be obtained.

[Example 10]
In translucent neutron scintillator composed of ZnS: Cu phosphor and ⁶ LiF neutron converter, translucent neutron with Nile Red (9-diethylamino-5-benzo [α] phenoxazinone) as the wavelength conversion agent added An example of the scintillator will be described.

  FIG. 22 shows the fluorescence spectrum and transmittance characteristics of a 1108-110 phosphor manufactured by Nichia Corporation, which is a ZnS: Cu phosphor. Nile Red was used as a wavelength conversion agent having an absorption spectrum suitable for this fluorescence spectrum. FIG. 23 shows the absorption spectrum and wavelength-converted fluorescence spectrum of Nile Red together with the fluorescence spectrum of the ZnS: Cu phosphor. Nile Red has a high conversion efficiency of 80%.

  The absorption spectrum of Nile Red has a peak at 520 nm and absorbs well in the range of 450 nm to 550 nm (FWHM). It can be seen that the absorption spectrum of Nile Red is in good agreement with the fluorescence spectrum of the ZnS: Ag phosphor. Further, it can be seen that the fluorescence spectrum of Nile Red shows a fluorescence spectrum having a peak at 580 nm and wavelength-converted in the range of 550 nm to 640 nm (FWHM). As described above, this wavelength region coincides with the region having the highest quantum efficiency of the SiAPD light detection element or the CCD camera element.

  Using the fluorescence spectrum and transmittance characteristics of the ZnS: Cu phosphor and the absorption spectrum and wavelength-shifted fluorescence spectrum of Nile Red, the fluorescence yield of the phosphor alone and the fluorescence collection when a wavelength conversion agent is added to the phosphor. Rate can be evaluated. For the evaluation calculation, the method described in Example 1 was used.

  As a result of the evaluation calculation, the yield in the case where Nile Red was not added to the ZnS: Cu phosphor and the case where it was added were 0.826 and 0.829, respectively. As a result, it was found that almost the same fluorescence yield was obtained when the wavelength conversion agent was added and when it was not added. As a photodetector used in combination with the scintillator, when used as a radiographic apparatus in combination with a CCD camera element using a SiAPD photodetector or a screen, the wavelength conversion fluorescence spectrum of the scintillator having the highest quantum efficiency. It can be seen that the effect of this scintillator is produced considering that the two are substantially in agreement.

Claims (4)

A translucent ZnS-based neutron scintillator comprising: a substrate; and a neutron detector including an adhesive substance in which a dye as a ZnS-based phosphor, a neutron converter, and a wavelength conversion agent on the substrate is dispersed. 2. The translucent material according to claim 1, wherein the ZnS-based phosphor is a particle beam detection ZnS: Ag phosphor, a ZnS: Ag, Cl phosphor, a ZnS: Ag, Al phosphor, or a ZnS: Cu phosphor. ZnS-based neutron scintillator. The translucent ZnS-based neutron scintillator according to claim 1 or 2, wherein the neutron converter is a ⁶ LiF or ¹⁰ B neutron converter. Examples of the color conversion agent include BisMSB (1,4-Bis (2-methylstyryl) benzene), POPOP (1,4-Bis (5-phenyl-2-oxazolyl) benzene), Coumarin 30 (7- (Diethylamino). ) -3- (1-methyl-1H-benzimidazol-2-yl) -2H-1-benzopyran-2-one), anthracene derivative (7,12-dimethylbenz [α] anthracene), 4-dimethylamino-4 ′ The translucent ZnS type | system | group neutron scintillator of any one of Claims 1-3 which is -nitrostilbene (4-Dimethylamino-4-Nitrostilbene) or Nile Red (9-diethylamino-5-benzo [(alpha)] phenoxazinone).