[go: up one dir, main page]

WO2011115179A1 - Scintillateur pour la détection de neutrons, détecteur de neutrons et appareil d'imagerie neutronique - Google Patents

Scintillateur pour la détection de neutrons, détecteur de neutrons et appareil d'imagerie neutronique Download PDF

Info

Publication number
WO2011115179A1
WO2011115179A1 PCT/JP2011/056250 JP2011056250W WO2011115179A1 WO 2011115179 A1 WO2011115179 A1 WO 2011115179A1 JP 2011056250 W JP2011056250 W JP 2011056250W WO 2011115179 A1 WO2011115179 A1 WO 2011115179A1
Authority
WO
WIPO (PCT)
Prior art keywords
neutron
scintillator
crystal
licaalf
detection
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/JP2011/056250
Other languages
English (en)
Japanese (ja)
Inventor
範明 河口
健太郎 福田
敏尚 須山
彰 吉川
健之 柳田
有為 横田
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Tohoku University NUC
Tokuyama Corp
Original Assignee
Tohoku University NUC
Tokuyama Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tohoku University NUC, Tokuyama Corp filed Critical Tohoku University NUC
Publication of WO2011115179A1 publication Critical patent/WO2011115179A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
    • C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
    • C09K11/7715—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing cerium
    • C09K11/7719—Halogenides
    • C09K11/772—Halogenides with alkali or alkaline earth metals
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/20—Measuring radiation intensity with scintillation detectors
    • G01T1/202—Measuring radiation intensity with scintillation detectors the detector being a crystal
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T3/00—Measuring neutron radiation
    • G01T3/06—Measuring neutron radiation with scintillation detectors
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K4/00—Conversion screens for the conversion of the spatial distribution of X-rays or particle radiation into visible images, e.g. fluoroscopic screens

Definitions

  • the present invention relates to a scintillator (Neutron Scintillator) for neutron detection for use in the detection of neutron radiation (Neutron), detail lithium fluoride calcium aluminum which contains cerium (Ce) is (LiCaAlF 6) scintillator for neutron detection of crystalline, And a neutron detector or neutron imaging apparatus using the crystal.
  • a scintillator for neutron detection for use in the detection of neutron radiation (Neutron)
  • detail lithium fluoride calcium aluminum which contains cerium (Ce) is (LiCaAlF 6) scintillator for neutron detection of crystalline
  • a neutron detector or neutron imaging apparatus using the crystal a neutron detector or neutron imaging apparatus using the crystal.
  • a scintillator is a substance that absorbs the radiation and emits fluorescence when irradiated with radiation such as ⁇ -rays, ⁇ -rays, ⁇ -rays, X-rays, and neutrons, and is a photomultiplier tube (PMT). It is used for radiation detection by combining with a photodetector. It has various application fields such as medical field such as tomography, industrial field such as non-destructive inspection, security field such as inventory inspection, academic field such as high energy physics.
  • this scintillator there are various types of scintillators depending on the type of radiation and purpose of use, and inorganic such as bismuth germanium oxide (Bi 4 Ge 3 O 12 ) and cerium-containing gadolinium silicon oxide (Gd 2 SiO 5 : Ce). Crystals; organic crystals such as anthracene; high molecular weight materials such as polystyrene and polyvinyltoluene containing organic phosphors; liquid scintillators; gas scintillators and the like.
  • inorganic such as bismuth germanium oxide (Bi 4 Ge 3 O 12 ) and cerium-containing gadolinium silicon oxide (Gd 2 SiO 5 : Ce).
  • Crystals organic crystals such as anthracene
  • high molecular weight materials such as polystyrene and polyvinyltoluene containing organic phosphors
  • liquid scintillators gas scintillators and the like.
  • a neutron beam detector using a solid neutron detection scintillator is one of the promising alternatives.
  • Typical characteristics required of scintillators include high light emission (Light Yield), high radiation stopping power, and fast fluorescence decay.
  • scintillators that detect neutrons neutrons and absorbing substances Since a radiation capture reaction occurs between the ⁇ -ray and ⁇ -rays easily, discrimination ability from the ⁇ -rays is required.
  • the amount of luminescence in the present invention is a technical term used in the scintillator field, and the total number of photons in a single luminescence of the scintillator by radiation excitation is divided by the energy of the radiation of the excitation source. Indicates the value.
  • the unit is, for example, photons / MeV for ⁇ -ray and ⁇ -ray excitation, and photons / neutron for neutron beam excitation.
  • a 6 Li glass scintillator As a solid scintillator for detecting neutrons, a 6 Li glass scintillator has been used as a material having no deliquescence and high-speed response. However, it is expensive due to the complicated manufacturing process, and there is a limit to enlargement. It was. In contrast, a neutron detection scintillator made of a fluoride crystal has an advantage that a large scintillator can be manufactured at a low cost. For example, a scintillator made of lithium barium fluoride (LiBaF 3 ) crystal has been proposed.
  • LiBaF 3 lithium barium fluoride
  • Non-Patent Document 1 Since the scintillator is highly sensitive to ⁇ rays and has a large background noise derived from ⁇ rays, special measures have to be taken when used as a scintillator for neutron detection (see Non-Patent Document 1).
  • the present inventors performed evaluation by irradiating a neutron beam for some crystals containing LiCaAlF 6 containing Ce in order to try application as a scintillator for detecting neutrons.
  • a scintillator for detecting neutrons 1.1 to 20 atoms (atom / nm 3 ) 6 Li per unit volume was contained in the fluoride single crystal, and the Ce content in the LiCaAlF 6 crystal was 0.005 to 5 to 100 mol of Li. It has been found that by making it a mole, it has particularly good characteristics as a scintillator for neutron detection (see Patent Document 1).
  • the ⁇ / ⁇ ratio of the luminescence amount is a value obtained by dividing the luminescence amount at the time of ⁇ -ray excitation by the luminescence amount at the time of ⁇ -ray excitation, and affects the discrimination ability between neutrons and ⁇ rays.
  • CeCa-containing LiCaAlF 6 crystals generate secondary radiation (primary mechanism) due to the nuclear reaction between incident neutrons and 6 Li, followed by electronic transition of Ce ions by this alpha radiation.
  • the light emission is caused by a two-stage mechanism called ultraviolet light emission (secondary mechanism) of about 290 to 310 nm. For this reason, since light emission is finally caused by excitation by ⁇ rays, the ratio of the light emission amount at the time of ⁇ ray excitation and the light emission amount at the time of ⁇ ray excitation affects the discrimination ability.
  • neutron imaging devices have been studied mainly using a neutron source having a radioactivity that is extremely harmful to a human body such as a nuclear reactor so far, and is not highly versatile. It is expected to spread more application range, consider an example of radioactivity less neutron source (e.g.
  • a substance made of a substance that emits fluorescence when a neutron beam collides is referred to as a neutron detection scintillator.
  • the inventors of the present invention prepared CeCa-containing LiCaAlF 6 crystals with various compositions and evaluated the discriminating ability between neutron rays and ⁇ rays. The amount of luminescence was measured and compared. As a result, it was found that good discrimination ability was obtained when a specific amount of Ce was contained. Furthermore, it has been found that the crystal of the present invention can be operated as a neutron detector by combining with a photomultiplier tube, and can be operated as a neutron imaging device by combining with a position sensitive photomultiplier tube (position sensitive PMT). It came to complete.
  • the present invention relates to a scintillator for neutron detection comprising a LiCaAlF 6 single crystal containing 0.04 to 0.16 mol% of Ce and containing 1.1 to 10 atoms (atom / nm 3 ) of 6 Li per unit volume. It is.
  • a neutron beam detector characterized by combining the scintillator and a photomultiplier tube.
  • another invention is a neutron beam imaging apparatus characterized by combining the scintillator and a position sensitive photomultiplier tube.
  • the LiCaAlF 6 crystal containing Ce of the present invention can be a scintillator for detecting neutrons with less background noise derived from ⁇ rays than before.
  • This scintillator is useful as a neutron detector that can be used for applications such as determining the presence or absence of neutrons in the environment by combining a photomultiplier tube.
  • the neutron imager can be suitably used in non-destructive inspection using the imager.
  • FIG. 1 It is the schematic of the crystal manufacturing apparatus by the micro pulling-down method used for manufacture of the scintillator of this invention. It is a wave height distribution spectrum figure at the time of 241 Am, 137 Cs irradiation of the scintillator for neutron detection of Example 1.
  • FIG. 2 It is a wave height distribution spectrum figure at the time of 241 Am and 137 Cs irradiation of the scintillator for neutron detection of Example 2.
  • FIG. It is a wave height distribution spectrum figure at the time of 241 Am, 137 Cs irradiation of the scintillator for neutron detection of Example 3.
  • FIG. It is a wave height distribution spectrum figure at the time of 241 Am and 137 Cs irradiation of the scintillator for neutron detection of the reference example 1.
  • FIG. It is the schematic which shows the neutron beam detector of this invention. It is a wave height distribution spectrum figure at the time of 252 Cf irradiation by the neutron beam detector of this invention. It is the schematic which shows the neutron beam imaging device of this invention. It is a schematic diagram for demonstrating the operation
  • FIG. It is a neutron imaging figure by 252 Cf irradiation by the neutron beam imaging device of the present invention and Example 6.
  • the scintillator for neutron detection of the present invention is a LiCaAlF 6 crystal containing Ce, and has a specific feature of having a specific Ce content and a 6 Li content.
  • the 6 Li content refers to the number of Li elements contained per 1 nm 3 of the scintillator.
  • the incident neutron causes a nuclear reaction with the 6 Li to generate ⁇ rays. Therefore, the 6 Li content affects the sensitivity to neutron beams, and the sensitivity to neutron beams increases as the 6 Li content increases.
  • Such 6 Li content select the chemical composition of the scintillator for neutron detection, also, it can be appropriately adjusted by adjusting the 6 Li content of LiF or the like used as the Li raw material.
  • the 6 Li content is the elemental ratio of 6 Li isotopes with respect to the total Li elements, and is about 7.6% for natural Li.
  • a method of adjusting the 6 Li content is as a starting material a general purpose material having a natural isotopic ratio
  • a method of adjusting by concentrating the 6 Li isotope to the desired 6 Li content or advance 6 Li is There is a method in which a concentrated raw material concentrated to a desired 6 Li content or more is prepared, and the concentrated raw material and the general-purpose raw material are mixed and adjusted.
  • the content of 6 Li needs to be 1.1 atom / nm 3 or more.
  • the 6 Li content can be achieved by selecting the type of metal fluoride crystal without using a Li raw material with a specially increased 6 Li content, so that a neutron detection scintillator can be provided at low cost.
  • the upper limit of the 6 Li content is 10 atoms / nm 3 .
  • the 6 Li content in the LiCaAlF 6 crystal containing Ce is about 10 atom / nm 3 at the maximum in the calculation, and a 6 Li content higher than this cannot be obtained.
  • 6 Li content A ⁇ C ⁇ ⁇ ⁇ 10 ⁇ 21 / M [1] (Wherein ⁇ is the density [g / cm 3 ] of the LiCaAlF 6 crystal containing Ce, M is the molecular weight [g / mol], C is the 6 Li content in the Li element [%], and A is the Avogadro number [6.02 ⁇ 10 23 ] is shown.)
  • the scintillator When the scintillator is irradiated with ⁇ rays as the secondary radiation, Ce of the scintillator is excited and emits light.
  • the light emission is light emission due to the electron orbital transition of Ce, and in particular, a scintillator with a short fluorescence lifetime and thus excellent high-speed response can be obtained.
  • the range of the Ce content contained in the LiCaAlF 6 crystal is the greatest feature of the present invention, and is 0.04 to 0.16 mol% with respect to LiCaAlF 6 .
  • the Ce content increases, the effective atomic number increases, and therefore background noise derived from ⁇ rays tends to increase (Patent Document 1).
  • Patent Document 1 the higher the Ce content, the lower the amount of light emitted at the time of ⁇ -ray incidence relative to the amount of light emitted at the time of neutron beam incidence, and thus the ability to discriminate between a signal from neutron rays and noise from gamma rays.
  • the Ce content is 0.04 mol% or more with respect to LiCaAlF 6 , it is preferable because good discrimination ability is obtained.
  • the content is 0.05 mol% or more, as a scintillator for detecting LiCaAlF 6 neutrons containing Ce, an unprecedented high discrimination ability can be obtained.
  • it exceeds 0.16 mol% with respect to LiCaAlF 6 , white turbidity and cracking occur and it becomes difficult to grow a single crystal. Therefore, it is preferably 0.16 mol% or less.
  • the existence state of Ce contained in the crystal is not certain, but it is presumed that it exists in place of part of the elements Ca and Al atoms constituting the crystal lattices or between the crystal lattices.
  • C s kC 0 (1-g) k ⁇ 1 [2] ⁇
  • C s Ce content of the metal fluoride crystal [mol% (Ce / Ca) ]
  • k is the effective segregation coefficient
  • C 0 is Ce content in the raw material [mol% (Ce / Ca) ]
  • G represents the solidification rate.
  • the effective segregation coefficient a value described in literature (for example, Growth of Ce-doped LiCaAlF6 and LiSrAlF6 single crystals by the Czochralski technique under CF4 atmosphere) can be adopted.
  • the effective segregation coefficient varies depending on the growth method, and according to the study by the present inventors, the effective segregation coefficient of Ce with respect to LiCaAlF 6 is 0.02 in the Czochralski method, and is 0.2 in the micro pull-down method. 04.
  • the Ce content in the actual crystal can be examined by a general elemental analysis technique such as ICP mass spectrometry or ICP atomic emission spectrometry.
  • the crystal of the present invention is a single crystal or a polycrystal, but by using a single crystal, emission intensity does not occur without causing loss due to non-radiative transition caused by lattice defects or scintillation light dissipation at grain boundaries.
  • a single crystal is preferable because a neutron scintillator with a high neutron can be obtained.
  • the crystal of the present invention is a transparent crystal that is colorless or slightly colored, and has excellent scintillation light transmission. In addition, it has good chemical stability, and in normal use, no performance degradation is observed in a short period of time. Furthermore, mechanical strength and workability are also good, and it is easy to process and use it in a desired shape.
  • the method for producing the crystal of the present invention is not particularly limited and can be produced by a known crystal production method, but is produced by the Czochralski method or the micro-pulling-down method. It is preferable.
  • a LiCaAlF 6 crystal containing Ce having excellent quality such as transparency can be produced.
  • the micro-pulling down method the crystal can be directly manufactured in a specific shape and can be manufactured in a short time.
  • a large crystal having a diameter of several inches can be manufactured at low cost.
  • a predetermined amount of raw material is filled in a crucible 1.
  • the purity of the following raw materials is not particularly limited, but is preferably 99.99% or more.
  • the raw material may be a powdery or granular raw material, or may be used after being sintered or melted and solidified in advance.
  • a metal fluoride of lithium fluoride (LiF), calcium fluoride (CaF 2 ), aluminum fluoride (AlF 3 ), or cerium fluoride (CeF 3 ) is used as a raw material.
  • the mixing ratio of these raw materials is 1: 1 for LiF, CaF 2 and AlF 3. Weigh to a molar ratio of 1. However, since LiF and AlF 3 are easy to volatilize, they may be weighed by about 1 to 10%. Since the volatilization amount is completely different depending on crystal growth conditions (temperature, atmosphere, and process), it is desirable to determine the weighing value by examining the volatilization amount of LiF and AlF 3 in advance.
  • LiF and AlF 3 may need to be weighed more than 10%.
  • the volatilization of CaF 2 and CeF 3 hardly poses a problem under normal LiCaAlF 6 crystal growth conditions.
  • the amount of CeF 3 determines the mixing ratio of the raw materials using the effective segregation coefficient as described above in consideration of the segregation phenomenon of Ce. At that time, the mixing ratio of the raw materials is calculated so that Ce is contained in the range of 0.04 to 0.16 mol% with respect to LiCaAlF 6 . Crystals having good discrimination ability can be obtained by adjusting the content to 0.04% mol or more, and crystals having no cloudiness or cracks can be produced by adjusting the content to 0.16 mol% or less.
  • the crucible 1, the heater 2, the heat insulating material 3, and the movable stage 4 filled with the raw materials are set as shown in FIG.
  • another crucible with a hole at the bottom may be installed, and fixed to the heater 2 or the like, and hung with a double crucible structure.
  • the seed crystal 5 is attached to the tip of the automatic diameter control device 6.
  • the seed crystal may be a high melting point metal such as platinum, but the LiCaAlF 6 single crystal or a single crystal having a crystal structure close to it has a crystallinity of the grown crystal. It tends to be good.
  • a LiCaAlF 6 single crystal having a rectangular parallelepiped shape having a size of about 6 ⁇ 6 ⁇ 30 mm 3 and cut, ground, and polished so that a side of 30 mm is along the c-axis direction can be used.
  • the automatic diameter control device measures the total weight of the seed crystal and the grown crystal, adjusts the growth rate of the seed crystal from the information, and can control the diameter of the crystal to be grown.
  • a load cell for a pulling apparatus that is commercially available for crystal growth of the Chocrasky method can be used.
  • the inside of the chamber 7 is evacuated to 1.0 ⁇ 10 ⁇ 3 Pa or less using an evacuation apparatus, and then an inert gas such as high purity argon is introduced into the chamber to perform gas replacement.
  • the pressure in the chamber after gas replacement is not particularly limited, but atmospheric pressure is common.
  • a solid scavenger such as zinc fluoride or a gas scavenger such as tetrafluoromethane.
  • a method of mixing in the raw material in advance is preferable, and when using a gas scavenger, a method of mixing with the above inert gas and introducing it into the chamber is preferable.
  • the raw material is heated and melted by the high frequency coil 8 and the heater 2.
  • the heating method is not particularly limited, and for example, a resistance heating type carbon heater or the like can be appropriately used instead of the configuration of the high frequency coil and the heater.
  • the melted raw material melt is brought into contact with the seed crystal. After adjusting the heater output so that the temperature at which the portion in contact with the seed crystal is solidified, the crystal is pulled up while automatically adjusting the pulling speed under the control of the automatic diameter control device 6.
  • the movable stage 4 may be appropriately moved in the vertical direction in order to adjust the liquid level.
  • Annealing treatment may be performed on the grown crystal for the purpose of removing crystal defects caused by fluorine atom defects or thermal strain.
  • the obtained Ce-containing LiCaAlF 6 crystal has good workability and can be easily processed into a desired shape.
  • a known cutting machine such as a blade saw or wire saw, a grinding machine, or a polishing machine can be used without any limitation.
  • the scintillator of the present invention can be combined with a photomultiplier tube to form a neutron detector. That is, the light (scintillation light) emitted from the neutron detection scintillator by the irradiation of the neutron beam is converted into an electric signal by a photomultiplier tube, so that the presence and intensity of the neutron beam can be grasped as an electric signal. it can.
  • the scintillation light emitted from the scintillator of the present invention is light having a wavelength of about 290 to 310 nm, and a photomultiplier tube capable of detecting light in this region can be preferably used. Specific examples of such photomultiplier tubes include R7600U and H7416 manufactured by Hamamatsu Photonics.
  • a LiCaAlF 6 crystal block containing Ce is bonded to the light entrance window of a photomultiplier tube with optical grease or the like, and a high voltage is applied to the photomultiplier tube.
  • a method of observing an electric signal output from the photomultiplier tube For the purpose of analyzing the intensity of the neutron beam using the electrical signal output from the photomultiplier tube, a shaping amplifier, a multi-channel analyzer, etc. are provided after the photomultiplier tube. May be provided.
  • a position sensitive photomultiplier tube in which detectors having a sensitive area of several mm square are arranged in an array is used, and Ce having a size covering a part or all of the light incident window.
  • the position sensitive photomultiplier tube one capable of detecting light having a wavelength of about 290 to 310 nm, which is scintillation light emitted from the scintillator of the present invention (for example, XP85012 manufactured by PHOTONIS) is used.
  • Optical grease or the like may be used for joining the light incident window and the crystal.
  • the crystal may have any shape, and can be a scintillator array in which plate-like, block-like, or quadrangular prism-like crystals are regularly arranged.
  • the surface other than the incident surface of the neutron beam may be covered with a cadmium plate, a LiF block or the like so that the neutron beam does not enter from the surroundings.
  • the signal output from the position-sensitive photomultiplier tube can be read out using any reading device, and may be controlled using a control program on a control personal computer.
  • Examples 1 to 3 Manufacture of neutron detection scintillators
  • the production method will be described with respect to Example 1, but Examples 2 and 3 were produced in the same manner except that the raw material weighing values were different.
  • a LiCaAlF 6 crystal containing Ce was manufactured using the crystal manufacturing apparatus by the Czochralski method shown in FIG.
  • As a raw material high purity fluoride powder of LiF, CaF 2 , AlF 3 , and CeF 3 having a purity of 99.99% or more was used.
  • LiF is, 6 Li content was used for 50%.
  • the crucible 1, the heater 2, and the heat insulating material 3 were made of high purity carbon.
  • each material was weighed and mixed raw materials obtained by well mixing were filled in the crucible 1.
  • the crucible 1 filled with the raw material was placed on the movable stage 4, and the heater 2 and the heat insulating material 3 were sequentially set around the crucible 1.
  • a LiCaAlF 6 single crystal was cut, ground and polished so that a side of 30 mm along the c-axis direction with a 6 ⁇ 6 ⁇ 30 mm 3 rectangular parallelepiped shape was used as a seed crystal 5 and attached to the tip of an automatic diameter controller. .
  • the inside of the chamber 6 is evacuated to 5.0 ⁇ 10 ⁇ 4 Pa by using an evacuation device comprising an oil rotary pump and an oil diffusion pump, and then a tetrafluoromethane-argon mixed gas is brought into the chamber 7 to atmospheric pressure. The gas was replaced.
  • a high frequency current was applied to the high frequency coil 8, and the raw material was heated and melted by induction heating.
  • the seed crystal 5 was moved and brought into contact with the liquid surface of the melted raw material melt.
  • the crystal was pulled up under the control of the automatic diameter controller 6 while automatically adjusting the pulling speed with a diameter of 55 mm as a target.
  • the movable stage 4 is appropriately moved in order to adjust the liquid level to be constant, and continuously lifted while appropriately adjusting the output of the high frequency coil, and separated from the liquid level when the length becomes about 80 mm.
  • a LiCaAlF 6 crystal containing Ce having a diameter of 55 mm and a length of about 80 mm was obtained.
  • the obtained crystal was cut with a wire saw equipped with a diamond wire, ground and mirror-polished, and processed into a shape having a length of 7 mm, a width of 2 mm, and a thickness of 1 mm to obtain a neutron scintillator of the present invention.
  • the Ce content was about 0.08, 0.06, and 0.04 mol%, respectively, with respect to LiCaAlF 6 according to the formula [2].
  • the 6 Li content of the Li raw material of the neutron detection scintillators of Examples 1 to 3 was 50%. Therefore, from the formula [1], the 6 Li content was 5.1 atom / nm 3 .
  • a commercially available 6 Li glass scintillator GS20 manufactured by Saint-Gobain; length 7 mm, width 2 mm, thickness 1 mm was used.
  • the scintillation light was converted into an electric signal through a photomultiplier tube to which a high voltage of 800 V was applied.
  • the electrical signal output from the photomultiplier tube is a pulse signal reflecting the scintillation light
  • the pulse height represents the emission intensity of the scintillation light
  • the waveform is the decay time constant of the scintillation light.
  • FIGS. 2, 3, 4 and 5 show the wave height distribution spectra obtained for the neutron detection scintillators of Examples 1, 2, 3 and Reference Example 1, respectively.
  • the horizontal axis of the wave height distribution spectrum represents the wave height value of the electric signal, that is, the emission intensity of the scintillation light.
  • the vertical axis represents the frequency of the electrical signal indicating each peak value, and here, the frequency is represented by the number of times the electrical signal is measured (counts).
  • the peak value at the time of 241 Am ⁇ -ray excitation was set to 1, and the maximum value of the peak values in the wave height distribution at the time of 137 Cs ⁇ -ray excitation was compared.
  • the lower this value the lower the crest value of ⁇ -ray noise. Therefore, ⁇ -ray noise can be removed by setting a threshold and removing low crest value signals and selecting high crest value signals. Becomes easy.
  • any of Examples 1 to 3 is a neutron detection scintillator having a value that is lower than the value of 0.58 of the 6 Li glass scintillator of Reference Example 1 and having good discrimination ability. Among them, especially when the Ce content is 0.06 and 0.08 mol%, the discrimination ability is good, and if it is 0.05 mol% or more, it is clearly superior to Reference Example 1 6 Li glass scintillator. Discrimination ability is obtained.
  • Example 4 [Production of neutron detector] Using the neutron detection scintillator of Example 2, a neutron detector comprising a combination of a neutron detection scintillator made of a LiCaAlF 6 crystal containing Ce and a photomultiplier tube was produced as follows.
  • FIG. 6 shows the configuration of the neutron beam detector of the present invention.
  • R7600U made by Hamamatsu Photonics Co. is used for the photomultiplier tube 9, and the 7 mm long and 2 mm wide surface of the neutron detection scintillator of Example 2 is used as the neutron detection scintillator with respect to the light incident window of the photomultiplier tube And bonded with optical grease.
  • a neutron beam from a 252 Cf sealed radiation source having a radioactivity of 3.7 MBq or less is about 40 mm. Irradiated with a thermal block through a polyethylene block of a thickness of. In order to measure the scintillation light emitted from the scintillator, a high voltage of 800 V was applied to the photomultiplier tube 9 from the power supply line to convert the scintillation light into an electric signal and output from the signal output line.
  • the electrical signal output from the photomultiplier tube is a pulse signal reflecting the scintillation light
  • the pulse height represents the emission intensity of the scintillation light
  • the waveform is the decay time constant of the scintillation light.
  • the obtained wave height distribution spectrum is shown in FIG. From FIG. 7, a clear peak indicating that a neutron beam has been detected can be confirmed, and it can be seen that the device is operating as a neutron beam detector.
  • the horizontal axis of the wave height distribution spectrum represents the wave height value of the electric signal, that is, the emission intensity of the scintillation light.
  • the wave height distribution spectrum is shown as a relative value where the peak value of the wave height distribution spectrum is 1.
  • the vertical axis represents the frequency of the electrical signal indicating each peak value, and here, the frequency is represented by the number of times the electrical signal is measured (counts).
  • Examples 5 and 6 [Production of neutron imaging system] A LiCaAlF 6 crystal containing Ce was used as a neutron detection scintillator, and a neutron imaging apparatus combined with a position sensitive photomultiplier tube was produced as follows.
  • FIG. 8 shows the configuration of the neutron imaging apparatus of the present invention.
  • the neutron detection scintillator unit 11 the neutron beam imaging devices of Examples 5 and 6 processed into different shapes were used.
  • the crystal used as the base of the neutron detection scintillator unit 11 is obtained by cutting the crystal used for the production of the neutron detection scintillator of Example 2 with a wire saw equipped with a diamond wire, grinding and mirror polishing. Using.
  • a scintillator plate processed into a shape having a diameter of 55 mm and a thickness of 2 mm was used.
  • 400 pieces processed to 2 ⁇ 2 ⁇ 4 mm 3 were prepared, and 20 ⁇ 20 2 ⁇ 2 mm 2 surfaces were arranged in rows and columns in an array form.
  • a scintillator array was used in which crystals were joined using barium sulfate having a high reflectance as a joining material.
  • the scintillator plate and the scintillator array were bonded to the light incident window of the position sensitive photomultiplier tube 12 using optical grease, thereby obtaining the neutron beam imaging apparatus of Examples 5 and 6.
  • As the position-sensitive photomultiplier tube 12 XP85012 made by PHOTONIS of 64 channels was used.
  • the position sensitive photomultiplier tube 12 was connected to the head amplifier unit 13 and then covered with a black vinyl sheet light shielding material 10 so that light from the outside did not enter the light incident window.
  • a black vinyl sheet light shielding material 10 for the head amplifier unit 13, an 80190 type multi-anode photomultiplier head amplifier unit manufactured by Clear Pulse is used, and connected to a personal computer from the signal line via an interface device (80190 type PCIF manufactured by Clear Pulse). It was operated using the company's control program so that the peak values of each of the 64 channels could be acquired every hour.
  • neutron transmission images were taken.
  • neutron beams from a 252 Cf sealed radiation source 14 having a radioactivity of 3.7 MBq or less are passed through a polyethylene block 15 having a thickness of about 40 mm with respect to the neutron detection scintillator unit 11 of FIG. And irradiated with thermal neutrons.
  • a lead block 16 having a thickness of 50 mm was installed between Examples 5 and 6 and the polyethylene block 15 for the purpose of removing ⁇ rays. Further, in order to prevent the neutron beam from being incident from an unexpected direction, the periphery of Examples 5 and 6 was covered with a LiF block 17 that hardly transmits the neutron beam except for the surface irradiated with the neutron beam. At this time, in order to confirm that a neutron transmission image can be taken, a T-shaped cadmium plate 18 having a thickness of 4 mm was placed on the surface irradiated with the neutron beam of Examples 5 and 6. Since cadmium absorbs neutrons well, when irradiated with neutrons, the portion of the T-shaped cadmium plate 18 does not transmit neutrons and a T-shaped shadow should be imaged.
  • a voltage of 2200 V was applied to operate the position sensitive photomultiplier tube 12 and the head amplifier unit 13.
  • Data was recorded when a peak value signal exceeding the value set as the threshold value was output from any of the 64 channels.
  • the threshold value was set for the purpose of acquiring as little as possible a signal due to the background noise of the device that occurs even when the neutron detection scintillator unit 11 does not emit light. Note that the integration time of one peak value is 5 microseconds, and the 64 channel signals obtained during that time are called events.
  • the recorded data were the serial number of the event and the information of the peak value of each of the 64 channels (8 ⁇ 8) in the event.
  • the total value of the peak values of 64 channels for each event was calculated, and a histogram of the total value (frequency distribution diagram) was created. In the histogram, a peak was observed in a portion where the total value was high. It was considered that the event of the total value corresponding to the peak portion was caused by the neutron beam and was adopted as an event for imaging described later.
  • the following calculation processing was performed. Arbitrary points were selected from the four corners of the 64 channels, and 8 ⁇ 8 coordinates (X A , Y A ) were determined. Next, the charge centroid (X D , Y D ) for each event was calculated from the coordinate value thus determined and the measured peak value.
  • the charge centroid are coordinates corresponding to the center of gravity of the group of electrons generated by the photoelectric surface of the position-sensitive photomultiplier tube (photocathode), in each occurrence of the 64 channels, with a value and its position of X A the sum of all 64 channels of a value obtained by multiplying the peak value, divided by the sum of the peak values of all 64 channels is X D.
  • the value of Y D is obtained by the same calculation with respect to Y A.
  • the calculated values of X D and Y D were each further multiplied by 8 and rounded off to convert to 64 ⁇ 64 coordinates.

Landscapes

  • Chemical & Material Sciences (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Molecular Biology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • General Engineering & Computer Science (AREA)
  • Measurement Of Radiation (AREA)
  • Luminescent Compositions (AREA)
  • Conversion Of X-Rays Into Visible Images (AREA)

Abstract

L'invention porte sur : un scintillateur pour la détection de neutrons, qui est hautement sensible à des faisceaux de neutrons et qui produit peu de bruit de fond attribuable au rayonnement γ ; et un détecteur de neutrons et un appareil d'imagerie neutronique qui sont fabriqués à l'aide de celui-ci. De façon spécifique, l'invention porte sur un scintillateur pour la détection de neutrons, qui est constitué d'un cristal de LiCaAlF6 qui contient 0,04 à 0,16 % en mole, de préférence 0,05 à 0,09 % en mole, de Ce et 1,1 à 106 atomes de Li par unité de volume (en atome/nm3) ; et sur un détecteur de neutrons et un appareil d'imagerie neutronique qui sont fabriqués à l'aide du scintillateur.
PCT/JP2011/056250 2010-03-19 2011-03-16 Scintillateur pour la détection de neutrons, détecteur de neutrons et appareil d'imagerie neutronique Ceased WO2011115179A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2010064257A JP2013116926A (ja) 2010-03-19 2010-03-19 中性子検出用シンチレーター、中性子線検出器及び中性子線撮像装置
JP2010-064257 2010-03-19

Publications (1)

Publication Number Publication Date
WO2011115179A1 true WO2011115179A1 (fr) 2011-09-22

Family

ID=44649262

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2011/056250 Ceased WO2011115179A1 (fr) 2010-03-19 2011-03-16 Scintillateur pour la détection de neutrons, détecteur de neutrons et appareil d'imagerie neutronique

Country Status (2)

Country Link
JP (1) JP2013116926A (fr)
WO (1) WO2011115179A1 (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012060381A1 (fr) * 2010-11-02 2012-05-10 株式会社トクヤマ Cristal de type colquiriite, scintillateur pour la détection de neutrons et détecteur de rayonnement neutronique
WO2012060382A1 (fr) * 2010-11-02 2012-05-10 株式会社トクヤマ Cristal de fluorure métallique et élément émettant de la lumière
WO2012115234A1 (fr) * 2011-02-24 2012-08-30 株式会社トクヤマ Scintillateur pour la détection des neutrons et détecteur de rayonnement de neutrons
WO2012121346A1 (fr) * 2011-03-08 2012-09-13 株式会社トクヤマ Dispositif de détection à faisceau de neutrons
EP2695928A4 (fr) * 2011-04-04 2014-10-22 Tokuyama Corp Scintillateur, détecteur de radiation et procédé de détection de radiation
JP2018505421A (ja) * 2014-11-28 2018-02-22 フォルシュングスツェントルム ユーリッヒ ゲーエムベーハー 高計数率シンチレーション検出器

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009119378A1 (fr) * 2008-03-24 2009-10-01 株式会社トクヤマ Scintillateur pour la détection de neutrons et détecteur de neutrons

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009119378A1 (fr) * 2008-03-24 2009-10-01 株式会社トクヤマ Scintillateur pour la détection de neutrons et détecteur de neutrons

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012060381A1 (fr) * 2010-11-02 2012-05-10 株式会社トクヤマ Cristal de type colquiriite, scintillateur pour la détection de neutrons et détecteur de rayonnement neutronique
WO2012060382A1 (fr) * 2010-11-02 2012-05-10 株式会社トクヤマ Cristal de fluorure métallique et élément émettant de la lumière
US8933408B2 (en) 2010-11-02 2015-01-13 Tokuyama Corporation Colquiriite-type crystal, scintillator for neutron detection and neutron detector
JP5868329B2 (ja) * 2010-11-02 2016-02-24 株式会社トクヤマ 中性子シンチレーター
WO2012115234A1 (fr) * 2011-02-24 2012-08-30 株式会社トクヤマ Scintillateur pour la détection des neutrons et détecteur de rayonnement de neutrons
EP2679652A4 (fr) * 2011-02-24 2014-09-10 Tokuyama Corp Scintillateur pour la détection des neutrons et détecteur de rayonnement de neutrons
WO2012121346A1 (fr) * 2011-03-08 2012-09-13 株式会社トクヤマ Dispositif de détection à faisceau de neutrons
EP2685286A4 (fr) * 2011-03-08 2014-09-10 Tokuyama Corp Dispositif de détection à faisceau de neutrons
EP2695928A4 (fr) * 2011-04-04 2014-10-22 Tokuyama Corp Scintillateur, détecteur de radiation et procédé de détection de radiation
US9920243B2 (en) 2011-04-04 2018-03-20 Tokuyama Corporation Scintillator, radiation detector, and method for detecting radiation
JP2018505421A (ja) * 2014-11-28 2018-02-22 フォルシュングスツェントルム ユーリッヒ ゲーエムベーハー 高計数率シンチレーション検出器
US10451750B2 (en) 2014-11-28 2019-10-22 Forschungszentrum Jülich GmbH Scintillation detector with a high count rate

Also Published As

Publication number Publication date
JP2013116926A (ja) 2013-06-13

Similar Documents

Publication Publication Date Title
RU2494416C2 (ru) Сцинтиллятор для детектирования нейтронов и нейтронный детектор
US8969812B2 (en) Garnet-type crystal for scintillator and radiation detector using the same
WO2011145651A1 (fr) Détecteur de faisceau de neutrons, scintillateur de détection de faisceau de neutrons et procédé permettant d'effectuer une discrimination entre un faisceau de neutrons et un faisceau γ
JPWO2012011506A1 (ja) ホスウィッチ型熱中性子検出器
EP2685286A1 (fr) Dispositif de détection à faisceau de neutrons
WO2011115179A1 (fr) Scintillateur pour la détection de neutrons, détecteur de neutrons et appareil d'imagerie neutronique
US9920243B2 (en) Scintillator, radiation detector, and method for detecting radiation
JP5877417B2 (ja) 中性子検出用シンチレーター及び中性子線検出器
JP5634285B2 (ja) コルキライト型結晶、中性子検出用シンチレーター及び中性子線検出器
JPWO2012115234A1 (ja) 中性子検出用シンチレーター及び中性子線検出器
JP5889202B2 (ja) 金属フッ化物共晶体、中性子用シンチレーター及び中性子撮像装置
JP5737978B2 (ja) 中性子検出用シンチレーター及び中性子線検出器
JP5737974B2 (ja) 中性子検出用シンチレーター及び中性子線検出器
WO2012026584A1 (fr) Scintillateur de détection de neutrons et détecteur de rayonnement neutronique

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 11756363

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 11756363

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: JP