WO2016158495A1 - シンチレータ - Google Patents
シンチレータ Download PDFInfo
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- WO2016158495A1 WO2016158495A1 PCT/JP2016/058703 JP2016058703W WO2016158495A1 WO 2016158495 A1 WO2016158495 A1 WO 2016158495A1 JP 2016058703 W JP2016058703 W JP 2016058703W WO 2016158495 A1 WO2016158495 A1 WO 2016158495A1
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- scintillator
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- 239000013078 crystal Substances 0.000 claims abstract description 82
- XQPRBTXUXXVTKB-UHFFFAOYSA-M caesium iodide Chemical compound [I-].[Cs+] XQPRBTXUXXVTKB-UHFFFAOYSA-M 0.000 claims abstract description 51
- 229910052797 bismuth Inorganic materials 0.000 claims abstract description 24
- 229910052716 thallium Inorganic materials 0.000 claims abstract description 19
- 229910052760 oxygen Inorganic materials 0.000 claims description 19
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 abstract description 14
- BKVIYDNLLOSFOA-UHFFFAOYSA-N thallium Chemical compound [Tl] BKVIYDNLLOSFOA-UHFFFAOYSA-N 0.000 abstract description 12
- 239000011159 matrix material Substances 0.000 abstract description 4
- 238000005259 measurement Methods 0.000 description 28
- 238000000034 method Methods 0.000 description 27
- 239000002994 raw material Substances 0.000 description 24
- 239000010453 quartz Substances 0.000 description 14
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 14
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 13
- 238000010438 heat treatment Methods 0.000 description 13
- 239000001301 oxygen Substances 0.000 description 13
- 230000005855 radiation Effects 0.000 description 11
- 239000002585 base Substances 0.000 description 9
- 230000000694 effects Effects 0.000 description 8
- 238000004519 manufacturing process Methods 0.000 description 8
- 150000001875 compounds Chemical class 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 6
- 239000000843 powder Substances 0.000 description 6
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 238000002109 crystal growth method Methods 0.000 description 4
- 230000007547 defect Effects 0.000 description 4
- 238000000921 elemental analysis Methods 0.000 description 4
- 239000011261 inert gas Substances 0.000 description 4
- 238000002844 melting Methods 0.000 description 4
- 230000008018 melting Effects 0.000 description 4
- CMJCEVKJYRZMIA-UHFFFAOYSA-M thallium(i) iodide Chemical compound [Tl]I CMJCEVKJYRZMIA-UHFFFAOYSA-M 0.000 description 4
- 239000010409 thin film Substances 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000000155 melt Substances 0.000 description 3
- 239000004570 mortar (masonry) Substances 0.000 description 3
- 238000002600 positron emission tomography Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- -1 Tl or Bi iodide Chemical class 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 239000002270 dispersing agent Substances 0.000 description 2
- 238000010894 electron beam technology Methods 0.000 description 2
- 150000004820 halides Chemical class 0.000 description 2
- 238000007689 inspection Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 230000001678 irradiating effect Effects 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000005204 segregation Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 238000002591 computed tomography Methods 0.000 description 1
- 238000012790 confirmation Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- XMBWDFGMSWQBCA-UHFFFAOYSA-N hydrogen iodide Chemical compound I XMBWDFGMSWQBCA-UHFFFAOYSA-N 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- 238000001095 inductively coupled plasma mass spectrometry Methods 0.000 description 1
- 238000002354 inductively-coupled plasma atomic emission spectroscopy Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 238000013507 mapping Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 150000002736 metal compounds Chemical class 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 238000000634 powder X-ray diffraction Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- 238000001771 vacuum deposition Methods 0.000 description 1
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- 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
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/12—Halides
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- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
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- C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
- C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
- C09K11/0827—Halogenides
- C09K11/0833—Halogenides with alkali or alkaline earth metals
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- C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
- C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
- C09K11/61—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing fluorine, chlorine, bromine, iodine or unspecified halogen elements
- C09K11/615—Halogenides
- C09K11/616—Halogenides with alkali or alkaline earth metals
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- C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
- C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
- C09K11/74—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing arsenic, antimony or bismuth
- C09K11/7428—Halogenides
- C09K11/7435—Halogenides with alkali or alkaline earth metals
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- C30B11/06—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method adding crystallising materials or reactants forming it in situ to the melt at least one but not all components of the crystal composition being added
- C30B11/065—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method adding crystallising materials or reactants forming it in situ to the melt at least one but not all components of the crystal composition being added before crystallising, e.g. synthesis
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- C30B13/00—Single-crystal growth by zone-melting; Refining by zone-melting
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- C30B13/10—Single-crystal growth by zone-melting; Refining by zone-melting adding crystallising materials or reactants forming it in situ to the molten zone with addition of doping materials
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- C—CHEMISTRY; METALLURGY
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- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
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- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
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- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B28/00—Production of homogeneous polycrystalline material with defined structure
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- C30B28/00—Production of homogeneous polycrystalline material with defined structure
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- C30B28/00—Production of homogeneous polycrystalline material with defined structure
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- C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
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- 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
- G21K2004/06—Conversion screens for the conversion of the spatial distribution of X-rays or particle radiation into visible images, e.g. fluoroscopic screens with a phosphor layer
Definitions
- the present invention relates to a scintillator that can be suitably used for an X-ray detector, for example.
- a scintillator is a substance that absorbs radiation such as ⁇ -rays and X-rays and emits visible light or electromagnetic waves having a wavelength close to that of visible light.
- Applications include, for example, medical PET (positron emission tomography), TOF-PET (time of flight positron emission tomography), X-ray CT (X-ray computed tomography), airports, etc.
- Various radiation detectors such as personal belongings inspection devices, baggage inspection devices used in harbors, petroleum exploration devices, exposure dose measurement devices and high energy particle measurement devices can be mentioned.
- Such a radiation detector generally includes a scintillator unit that receives radiation and converts it into visible light, and a photomultiplier tube (hereinafter referred to as an electrical signal) that detects visible light converted and transmitted by the scintillator unit. (Hereinafter referred to as “PMT”) and a photo detector such as a photodiode.
- a scintillator used for this type of application is desired to be a scintillator with a high light emission output in order to reduce noise and increase measurement accuracy.
- alkali halide crystals such as CsI and NaI have been widely used as scintillators.
- scintillators based on CsI are used because they have a relatively high radiation absorption efficiency, a relatively small amount of radiation damage, and a relatively easy thin film production by a vacuum deposition method or the like.
- Patent Document 1 discloses cesium iodide: thallium (CsI: Tl) in which cesium iodide (CsI) is doped with thallium (Tl).
- Patent Document 2 discloses a scintillator with improved afterglow characteristics obtained by doping bismuth (Bi) into a crystal material containing CsI (cesium iodide) as a base and thallium (Tl) as an emission center. A scintillator is disclosed.
- the present invention relates to a scintillator having a crystal containing CsI (cesium iodide) as a base and containing thallium (Tl) and bismuth (Bi), which can further enhance afterglow characteristics while maintaining high output.
- CsI cesium iodide
- Ti thallium
- Bi bismuth
- the present invention is a scintillator having a crystal comprising CsI (cesium iodide) as a base and containing Tl, Bi and O, wherein the Bi-containing concentration a relative to Cs in the crystal is 0.001 at. ppm ⁇ a ⁇ 5 at.
- the ratio (a / b) of the O content concentration b to I in the crystal and the Bi content concentration a to Cs in the crystal is 0.005 ⁇ 10 ⁇ 4 to 200 ⁇ 10 ⁇ 4 .
- the present invention relates to a scintillator having a crystal containing CsI (cesium iodide) as a base and containing thallium (Tl), bismuth (Bi), and oxygen (O). While maintaining the ratio (a / b) with the Bi content concentration a to Cs within a predetermined range, the Bi content concentration a with respect to Cs in the crystal is decreased and adjusted to the predetermined range, thereby maintaining a high output.
- the scintillator proposed by the present invention can further increase the output of the radiation detector by combining it with a PD (photodiode) as a detector, for example, and further clarify the image of the radiation detector, or check the baggage. For example, it is possible to suitably capture an image of a moving subject using a machine.
- FIG. 6 is a dynamic SIMS image of the crystal body (measurement sample) obtained in Example 8.
- FIG. 3 is a dynamic SIMS image of the crystal body (measurement sample) obtained in Comparative Example 1.
- the scintillator according to the present embodiment is a scintillator having a crystal made of CsI (cesium iodide) as a base (host) and containing Tl, Bi, and O.
- CsI cesium iodide
- the matrix of the present scintillator may contain a Tl compound or a Bi compound or both in addition to CsI (cesium iodide). That is, the matrix of the present scintillator may be made of CsI (cesium iodide), or may contain CsI (cesium iodide) and a Tl compound or Bi compound, or both.
- the Tl compound and the Bi compound are a Tl raw material, a Bi raw material, or a compound thereof described later.
- the Bi content concentration a to Cs in the crystal is decreased.
- the concentration a of bismuth (Bi) with respect to Cs in the crystal is 0.001 at. ppm ⁇ a ⁇ 5 at. ppm is preferable, and 0.001 at. ppm or more or 1 at. ppm or less, among which 0.003 at. ppm or more or 0.5 at. It is particularly preferred that it is ppm or less.
- the content concentration a of bismuth (Bi) is set to 5 at. By setting it as ppm or less, an afterglow reduction effect can be exhibited without impairing output characteristics.
- the content concentration a of bismuth (Bi) is set to 0.001 at. By setting it as ppm or more, the effect of low afterglow can be obtained.
- the content of oxygen (O) with respect to I in the crystal is not particularly limited as long as it is within the range of the above ratio (a / b).
- the O content concentration b with respect to I in the crystal is 0 at. % ⁇ B ⁇ 0.30 at. %, In particular 0.001 at. % Or more or 0.10 at. % Or less, of which 0.01 at. % Or more or 0.08 at. % Or less is particularly preferable.
- the content of thallium (Tl) in the crystal is not particularly limited.
- the concentration of thallium (Tl) relative to Cs in CsI is 100 at. ppm to 10,000 at. ppm is preferable, and in particular, 300 at. ppm or more or 4000 at. It is particularly preferred that it is ppm or less.
- the concentration of thallium (Tl) is 100 at. If it is more than ppm, the scintillation luminous efficiency of the grown crystal can be sufficiently obtained. On the other hand, 10,000 at. If it is less than or equal to ppm, it is possible to avoid a decrease in light emission amount due to concentration quenching.
- the preparation concentration of Bi in other words, the blending amount at the time of manufacturing the scintillator is 0.01 at. % Or less, preferably 0.00001 at. % Or more or 0.01 at. % Or less is more preferable. Further, in order to obtain the above-mentioned Tl concentration with respect to Cs, the Tl preparation concentration is 0.05 at. % Or more and 1.00 at. % Or less is preferable.
- the form of the scintillator may be any of a bulk shape, a column shape, and a thin film shape. In either case, the effect of reducing afterglow can be enjoyed.
- the scintillator may be single crystal or polycrystal. Whether the scintillator is a single crystal or a polycrystal, afterglow can be reduced.
- single crystal refers to a crystal that is recognized as a CsI single-phase crystal when the crystal is measured by XRD.
- a scintillator crystal usually has crystal defects and strains in its production process.
- this scintillator supplies a small amount of oxygen together with Bi during CsI crystal growth, so that Bi and O exert a dispersant effect on Tl, and the concentration of Tl is locally increased. Therefore, crystal defects and distortion can be reduced, and high output and low afterglow can be achieved.
- This scintillator can be obtained by growing a crystal after mixing and melting a raw material containing a CsI raw material, a Tl raw material and a Bi raw material.
- the Tl raw material and Bi raw material include Tl or Bi halides such as Tl or Bi iodide, oxides, metals, or metal compounds.
- the crystal growth method at this time is not particularly limited.
- the Bridgman-Stockbarger method also referred to as “BS method”
- the temperature gradient fixing method such as VGF method
- Czochralski also referred to as “CZ method”.
- Well-known crystal growth methods such as the Kilopros method, the micro pull-down method, the zone melt method, these improved methods, and other melt growth methods can be appropriately employed.
- typical BS method and CZ method will be described.
- the BS method is a method in which raw materials are put in a crucible and melted, and crystals are grown from the bottom of the crucible while the crucible is pulled down.
- the crystal growing apparatus is relatively inexpensive and has a feature that a large-diameter crystal can be grown relatively easily.
- it is difficult to control the crystal growth orientation, and excessive stress is applied during crystal growth or cooling, so that it is said that the stress distribution remains in the crystal and strain and dislocations are easily induced.
- the CZ method is a method in which a raw material is put in a crucible and melted, and a seed (seed crystal) is brought into contact with the melt surface to grow (crystallize) while rotating the crystal.
- the CZ method is said to facilitate the growth of the target crystal orientation because it is possible to identify and crystallize the crystal orientation.
- BS method An example of the BS method according to an example of the crystal growth method will be described more specifically.
- CsI powder as a raw material were weighed and mixed TlI powder and BiI 3 powder in a predetermined amount, filling the mixture in a quartz crucible, enclosing the crucible while vacuuming as necessary. If necessary, a seed crystal can be placed at the bottom of the crucible.
- This quartz crucible is installed in a crystal growth apparatus. At this time, when the crucible is not sealed, it is preferable to select an appropriate atmosphere while adjusting the oxygen concentration.
- the quartz crucible is heated to the melting point or higher by a heating device to melt the raw material filled in the crucible.
- the raw material in the crucible After the raw material in the crucible is melted, when the crucible is pulled down vertically at a speed of about 0.1 mm / hour to 3 mm / hour, the raw material that has become the melt starts to solidify from the bottom of the crucible and crystals grow.
- the ingot-like crystal can be grown by ending the pulling down of the crucible when all the melt in the crucible is solidified and cooling it to about room temperature while gradually cooling it with a heating device.
- the oxygen concentration in the crystal can be adjusted by filling the crucible with the raw material and then evacuating the crucible with a pump or the like to adjust the oxygen concentration in the crucible and heat it.
- the oxygen concentration in the crystal can be adjusted by using a crucible partly open and filling the crucible in the atmosphere with the raw material, and then adjusting the oxygen concentration in the heating furnace and heating. Can do.
- the atmosphere in the heating furnace is preferably an inert gas atmosphere containing a little oxygen by flowing an inert gas such as N 2 .
- the ingot-like crystal grown as described above may be cut into a predetermined size and then processed into a desired scintillator shape.
- the crystal can be heat-treated as necessary, but is not necessarily heat-treated.
- a heat treatment method for example, the crystal grown in the above process is placed in a container, the container is placed in a heat treatment furnace, and the temperature in the heat treatment furnace is soaked to about 80 to 90% of the melting point. The strain remaining in the crystal can be removed by heating.
- the atmosphere in the heat treatment may be an inert gas atmosphere such as high-purity argon (Ar) gas. However, it is not limited to such a heat treatment method.
- the “scintillator” means that it absorbs radiation such as X-rays and ⁇ -rays, and has a wavelength close to that of visible light or visible light (the wavelength range of light may extend from near ultraviolet to near infrared). It means a substance that radiates electromagnetic waves (scintillation light) and a component of a radiation detector having such a function.
- X to Y (X and Y are arbitrary numbers) is described, it means “preferably greater than X” or “preferably greater than Y” with the meaning of “X to Y” unless otherwise specified. The meaning of “small” is also included. Further, when “X or more” (X is an arbitrary number) or “Y or less” (Y is an arbitrary number), the intention of “preferably larger than X” or “preferably smaller than Y” Is included.
- the output (nA) and afterglow (ppm) were measured using the measuring apparatus shown in FIG.
- the measurement sample sintillator plate
- 8 mm ⁇ 8 mm ⁇ 2 mm thickness was used as the measurement sample (scintillator plate).
- the output is an output of the photodiode when the PIN photodiode receives scintillation light generated in the measurement sample by irradiating the measurement sample with predetermined X-rays.
- the afterglow means afterglow after a predetermined time after X-ray irradiation.
- a target made of tungsten (W) is irradiated with an electron beam having an applied voltage of 120 kV and an applied current of 20 mA to generate an X-ray, and this X-ray is irradiated to a measurement sample, and the output of scintillation light and transmitted X-ray is a PIN photodiode. (“S1723-5” manufactured by Hamamatsu Photonics Co., Ltd.).
- a scintillation light was shielded by placing a light shielding tape over a hole in a lead plate having a thickness of 2.2 mm, and the output of only transmitted X-rays was measured. And the output by the transmitted X-ray was subtracted, and the output by the scintillation light was obtained.
- the current value flowing through the PIN photodiode was measured as the background value (I bg ) before the measurement sample was irradiated with the X-ray, and the afterglow (@ 20 ms) was calculated from the following equation.
- Afterglow (@ 20ms) ( I20ms -Ibg ) / (I- Ibg )
- X-ray diffraction (XRD) measurement uses “RINT-TTRIII (50 kV, 300 mA)” manufactured by Rigaku Corporation as a measuring device, a Cu target is used as a radiation source, and 2 ⁇ ranges from 10 to 80 degrees. An XRD pattern was obtained.
- the elemental analysis of O uses an inert gas melting-non-dispersive infrared absorption method (model: EMGA-620, device manufacturer: Horiba, Ltd.) to determine the O content concentration (at.%) Of CsI with respect to I. It was.
- EMGA-620 inert gas melting-non-dispersive infrared absorption method
- Imaging-Dynamic-SIMS (referred to as “dynamic SIMS”. Model: IMS-7f, apparatus manufacturer: Ametech Co., Ltd.) was used.
- the measurement sample was cut to a size of 5 mm ⁇ 5 mm ⁇ thickness 2 mm, and the measurement was performed after the measurement surface was sputtered to a depth of about 100 ⁇ m as pretreatment before measurement.
- the area of measurement was an area of 50 ⁇ m ⁇ 50 ⁇ m, irradiated with oxygen of primary ions to a depth of about 5 ⁇ m, and the detected 205 Tl secondary ion intensity data was subjected to a three-dimensional mapping process.
- Examples 1 and 3-11 and Comparative Examples 1-2 and 4 CsI powder (99.999%), TlI powder (99.999%), and BiI 3 powder (99.999%) are weighed in the amounts shown in Table 1, mixed in a mortar, and the crystal growing apparatus shown in FIG. To grow crystals.
- the doping amount of the Tl and Bi elements is shown as the atomic percentage (at.%) With respect to the Cs element in the base material CsI.
- Crystal growth was performed by the following vertical Bridgman method. That is, hydrofluoric acid adjusted to a hydrofluoric acid concentration of 10% was put in a quartz crucible having a diameter of 45 mm in diameter and a bottom having a conical shape of 100 mm and washed for 5 minutes. The quartz crucible thus washed was washed thoroughly with water and then naturally dried. The raw material mixed in the mortar as described above is put into the quartz crucible pretreated in this way, and heated to 300 ° C. while evacuating to a predetermined internal pressure of the crucible (see Table 1) using a rotary pump and an oil diffusion pump. After holding for 12 hours to remove moisture contained in the raw material, quartz was heated and melted with a burner while maintaining the vacuum state, and the raw material was sealed.
- the quartz crucible was set in a furnace having a nitrogen gas atmosphere, heated with a heater until the raw material was melted, and maintained at that temperature for 24 hours after melting the raw material. Thereafter, the quartz crucible was pulled down at a speed of 0.5 mm / hour, lowered for 250 hours, then stopped, and the heating of the heater was gradually stopped over 24 hours. The crystal body thus obtained was cut out in a predetermined size and a predetermined direction to obtain the respective measurement samples.
- Example 2 and Comparative Example 3 using a quartz crucible having a diameter of 45 mm, a length of 100 mm, and an open top, the quartz crucible was washed in the same manner as in Example 1 and then thoroughly washed with water and allowed to dry naturally. After that, the raw materials mixed in a mortar were put, a quartz crucible was set in the furnace, and the flow rate was adjusted by flowing N 2 into the furnace in an air atmosphere. After heating to 300 ° C. in this state and holding for 12 hours to remove moisture contained in the raw material, a measurement sample was obtained in the same manner as in Example 1 above. At this time, the oxygen concentration of the processing atmosphere was changed by controlling the flow rate when N 2 was passed.
- Example 12 a measurement sample was obtained in the same manner as in Example 1 except that a quartz crucible having a cylindrical body diameter of 120 mm and a length of 230 mm having a conical bottom was used.
- Example 1-12 A part of the crystal obtained in Example 1-12 was pulverized and subjected to powder XRD measurement. As a result, all the crystals obtained in Example 1-12 were CsI single-phase crystals, The other phases were not confirmed.
- the scintillator having a crystal containing CsI (cesium iodide) as a base and containing Tl, Bi, and O is equivalent to I in the crystal.
- CsI cesium iodide
- the ratio (a / b) of the O-containing concentration b and the Bi-containing concentration a to Cs in the crystal is 0.005 ⁇ 10 ⁇ 4 to 200 ⁇ 10 ⁇ 4
- Bi to Cs in the crystal The content concentration a is 0.001 at. ppm ⁇ a ⁇ 5 at. It was found that by setting the ppm, the afterglow characteristics can be further enhanced while maintaining a high output.
- Chamber 2 Insulation 3: Heater 4: Pull-down mechanism 5: Quartz crucible
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Abstract
Description
例えば特許文献1には、ヨウ化セシウム(CsI)にタリウム(Tl)をドープしたヨウ化セシウム:タリウム(CsI:Tl)が開示されている。
本実施形態に係るシンチレータ(以下「本シンチレータ」という)は、CsI(ヨウ化セシウム)を母体(ホスト)とし、且つ、Tl、Bi及びOを含有してなる結晶を有するシンチレータである。
ここで、Tl化合物及びBi化合物は、後述するTl原料、Bi原料或いはそれらの化合物である。
かかる観点から、結晶中のIに対するO含有濃度bとCsに対するBi含有濃度aとの比率(a/b)は0.005×10-4~200×10-4であるのが好ましく、中でも0.01×10-4以上或いは100×10-4以下、その中でも0.05×10-4以上或いは50×10-4以下であるのが特に好ましい。
但し、好ましくは、結晶中のIに対するO含有濃度bが0at.%<b≦0.30at.%であり、中でも0.001at.%以上或いは0.10at.%以下、その中でも0.01at.%以上或いは0.08at.%以下であるのが特に好ましい。
酸素(O)をかかる濃度範囲となるように含有させることにより、単にビスマス(Bi)を少量含有させることだけでは達成されることのなかった性能、すなわち高出力を維持しつつ残光をより一層低減させることができる。
また、上述したCsに対するTl含有濃度とするために、Tlの仕込み濃度は0.05at.%以上1.00at.%以下とすることが好ましい。
なお、本発明において「単結晶」とは、結晶をXRDで測定した際にCsI単相の結晶体と認められるものをいう。
次に、本シンチレータの製造方法の一例について説明する。但し、本シンチレータの製造方法が次に説明する方法に限定されるものではない。
この際、Tl原料及びBi原料としては、Tl又はBiのヨウ化物などのようなTl又はBiのハロゲン化物や、酸化物、金属或いは金属化合物などを挙げることができる。但し、これらに限るものではない。
この際の結晶育成方法は、特に限定するものではなく、例えばBridgman-Stockbarger法(「BS法」ともいう)、温度勾配固定化法(例えばVGF法など)、Czochralski(「CZ法」ともいう)、キロプロス法、マイクロ引き下げ法、ゾーンメルト法、これらの改良法、その他の融液成長法等、公知の結晶育成方法を適宜採用することができる。
以下、代表的なBS法とCZ法について説明する。
例えば、原料となるCsI粉体、TlI粉体及びBiI3粉体を所定量に秤量・混合し、この混合物を石英坩堝に充填し、必要に応じて真空引きしながら坩堝を封入する。必要により坩堝底部に、種結晶を入れておくこともできる。この石英坩堝を結晶成長装置内に設置する。この際、坩堝を封入しない場合は、結晶成長装置内の雰囲気は、酸素濃度を調整しつつ適切な雰囲気を選択するのが好ましい。加熱装置によって石英坩堝を融点以上に加熱し、坩堝に充填した原料を溶融させる。
坩堝内の原料が融解した後、坩堝を0.1mm/時間~3mm/時間程度の速度で鉛直下方に引き下げると、融液となった原料は坩堝底部から固化が始まり、結晶が成長する。坩堝内の融液がすべて固化した段階で坩堝の引き下げを終了し、加熱装置により徐冷しつつ、室温程度にまで冷却することで、インゴット状の結晶を育成することができる。
例えば、坩堝に原料を充填した後、坩堝内をポンプなどで真空引きして坩堝内の酸素濃度を調整して加熱するようにすれば、結晶中の酸素濃度を調整することができる。
また、一部が開放された坩堝を用いて、大気中で坩堝に原料を充填した後、加熱炉内の酸素濃度を調整して加熱するようにしても、結晶中の酸素濃度を調整することができる。この際、加熱炉内の雰囲気は、例えばN2等の不活性ガスを流して酸素を若干含む不活性ガス雰囲気などとするのが好ましい。
熱処理の方法としては、例えば、前記工程で育成された結晶体を容器に入れ、この容器を熱処理炉内に設置し、熱処理炉内温度を融点の約80~90%の温度に均熱的に加熱して、結晶中に残留する歪を除去することができる。熱処理における雰囲気は、高純度アルゴン(Ar)ガス等の不活性ガス雰囲気とすればよい。但し、このような熱処理方法に限定するものではない。
本発明において「シンチレータ」とは、X線やγ線などの放射線を吸収し、可視光又は可視光に近い波長(光の波長域は近紫外~近赤外にまで広がっていてもよい)の電磁波(シンチレーション光)を放射する物質、並びに、そのような機能を備えた放射線検出器の構成部材を意味する。
また、「X以上」(Xは任意の数字)或いは「Y以下」(Yは任意の数字)と記載した場合、「Xより大きいことが好ましい」或いは「Yより小さいことが好ましい」旨の意図を包含する。
図1に示す測定装置を使用して、出力(nA)及び残光(ppm)を測定した。
測定サンプル(シンチレータ板)は、8mm×8mm×厚み2mmを使用した。
この際、前記出力とは、所定のX線を測定サンプルに照射したことにより測定サンプルに生じるシンチレーション光をPINフォトダイオードで受光した時のフォトダイオードの出力である。前記残光とは、X線照射後所定時間後の残光という意味である。
また、上記同様に、120kV、20mAの電子線を照射しX線を発生させ、このX線を測定サンプルに1秒間照射し、PINフォトダイオード(浜松ホトニクス株式会社製「S1723-5」)に流れる電流値(I)を測定した。次に、X線を測定サンプルに1秒間照射した後、X線の照射を遮断し、20ms後に前記PINフォトダイオードに流れる電流値(I20ms)を測定した。また、X線を測定サンプルに照射する前の状態において、PINフォトダイオードに流れる電流値をバックグラウンド値(Ibg)として測定し、次の式から残光(@20ms)を算出した。
残光(@20ms)=(I20ms-Ibg)/(I-Ibg)
X線回折(XRD)測定は、測定装置として株式会社リガク製「RINT-TTRIII(50kV、300mA)」を使用し、線源にはCuターゲットを用いて、2θが10度から80度の範囲でXRDパターンを得た。
各元素含有濃度の測定方法を以下に示す。
すなわち、Tlの元素分析は、ICP-AES(型式:SPS3525、装置メーカ:株式会社日立ハイテクサイエンス)を用いて、CsIのCsに対するTl含有濃度(at.ppm)を求めた。
Biの元素分析は、ICP-MS(型式:XSERIES2、装置メーカ:Thermo Scientific社)を用いて、CsIのCsに対するBi含有濃度(at.ppm)を求めた。但し、Bi含有濃度が0.001at.ppm未満の場合、測定値のばらつきが大きいため、表1には「<0.001」と表示した。この場合Bi/Oの比率を示す意味がないためこの項目は「-」と表示した。
Oの元素分析は、不活性ガス融解-非分散型赤外線吸収法(型式:EMGA-620、装置メーカ:株式会社堀場製作所)を用いて、CsIのIに対するO含有濃度(at.%)を求めた。
Oの元素分析測定の前処理として、バルク体のサンプルを窒素で充填したグローブボックス内で切断し、新鮮な面を得たサンプルを使用した。
Tlの偏析は、Imaging-Dynamic-SIMS(「ダイナミックSIMS」と称する。型式:IMS-7f、装置メーカ:アメテック株式会社)を用いた。測定サンプルは5mm×5mm×厚み2mmの寸法に切断し、測定前の前処理として測定面を約100μmの深さまでスパッタ処理を行った後に本測定を行った。測定の領域は50μm×50μmの面積を約5μmの深さまで1次イオンの酸素を照射して、検出された205Tlの2次イオン強度データを3次元マッピング処理した。
CsI粉(99.999%)、TlI粉(99.999%)、さらにBiI3粉(99.999%)を表1に示す量で秤量し、乳鉢で混合し、図2に示す結晶育成装置にセットし、結晶を育成した。ここで、Tl及びBi元素のドープ量は、母材であるCsI中のCs元素に対する原子数パーセント(at.%)として示した。
このように前処理した石英坩堝に、上記の如く乳鉢で混合した原料を入れ、ロータリーポンプと油拡散ポンプを用い所定の坩堝内圧(表1参照)となるように真空引きしながら300℃に加熱後に12時間保持して、原料に含まれている水分を飛ばした後、真空状態を維持したまま石英をバーナーで加熱して溶融させて原料を封入した。
このようにして得られた結晶体を、所定の大きさ・所定の方向に切り出して、それぞれの上記の測定サンプルを得た。
実施例2及び比較例3では、寸胴部直径45mm、長さ100mmで上端が開口した石英坩堝を用いて、実施例1と同様に石英坩堝の洗浄を行なった後水でよく洗い、自然乾燥させた後、乳鉢で混合した原料を入れて、石英坩堝を炉内にセットし、大気雰囲気下の炉内にN2を流して流量を調整した。この状態のまま300℃まで加熱した後に12時間保持して、原料に含まれている水分を飛ばした後は、上記実施例1と同様に測定サンプルを得た。この際、N2を流す際の流量を制御して処理雰囲気の酸素濃度を変更させた。
実施例12では、寸胴部直径120mm、長さ230mmの底部が円錐形状の石英坩堝を用いた以外、実施例1と同様に測定サンプルを得た。
実施例1-12で得られた結晶体の一部を粉砕し、粉末XRD測定を行ったところ、実施例1-12で得られた結晶体はいずれも、CsI単相の結晶体であり、他の相は確認されなかった。
実施例8以外の実施例もすべて同様の傾向を示し、Bi含有濃度及びO含有濃度も所定範囲内であったため、BiとOがTlを分散させる分散剤としての効果を発揮することを確認することができた。
2:断熱材
3:ヒーター
4:引き下げ機構
5:石英坩堝
Claims (2)
- CsI(ヨウ化セシウム)を母体とし、Tl、Bi及びOを含有してなる結晶を有するシンチレータであって、
前記結晶中のCsに対するBi含有濃度aが0.001at.ppm≦a≦5at.ppmであり、
前記結晶中のIに対するO含有濃度bと、前記結晶中のCsに対するBi含有濃度aとの比率(a/b)が0.005×10-4~200×10-4であることを特徴とするシンチレータ。 - 前記結晶中のIに対するO含有濃度bが0at.%<b≦0.30at.%であることを特徴とする請求項1記載のシンチレータ。
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RU2016148861A RU2627387C1 (ru) | 2015-03-31 | 2016-03-18 | Сцинтиллятор |
EP16758076.0A EP3109294B1 (en) | 2015-03-31 | 2016-03-18 | Scintillator |
US15/322,206 US9869777B2 (en) | 2015-03-31 | 2016-03-18 | Scintillator |
JP2016545946A JP6011835B1 (ja) | 2015-03-31 | 2016-03-18 | シンチレータ |
UAA201612772A UA116850C2 (uk) | 2015-03-31 | 2016-03-18 | Сцинтилятор |
CN201680000932.3A CN106211779B (zh) | 2015-03-31 | 2016-03-18 | 闪烁体 |
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CN107229065A (zh) * | 2017-05-10 | 2017-10-03 | 江苏万略医药科技有限公司 | 闪烁液 |
EP3803467A4 (en) | 2018-05-25 | 2022-03-02 | Saint-Gobain Ceramics & Plastics Inc. | CSL(TI) SCINTILLATION CRYSTAL COMPRISING ANTIMONY AND OTHER MULTIVALENT CATIONS FOR REDUCING LATERING, AND RADIATION DETECTION APPARATUS COMPRISING THE SCINTILLATION CRYSTAL |
CN110054205B (zh) * | 2018-06-06 | 2021-11-09 | 南方科技大学 | 碘化铯纳米晶及其制备方法和应用 |
EP4051757A4 (en) * | 2019-10-28 | 2023-11-15 | Luxium Solutions, LLC | CSI(TL) SCINTILLATOR CRYSTAL COMPRISING MULTIVALENT CATIONS FOR REDUCING AFTERLUMINESCENCE, AND RADIATION DETECTION APPARATUS COMPRISING THE SCINTILLATION CRYSTAL |
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JP2008215951A (ja) | 2007-03-01 | 2008-09-18 | Toshiba Corp | 放射線検出器 |
WO2013027671A1 (ja) | 2011-08-19 | 2013-02-28 | 国立大学法人東北大学 | シンチレーター |
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JP2008215951A (ja) | 2007-03-01 | 2008-09-18 | Toshiba Corp | 放射線検出器 |
WO2013027671A1 (ja) | 2011-08-19 | 2013-02-28 | 国立大学法人東北大学 | シンチレーター |
Non-Patent Citations (1)
Title |
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TOTSUKA DAISUKE ET AL.: "Afterglow Suppression by Codoping with Bi in CsI:Tl Crystal Scintillator", APPLIED PHYSICS EXPRESS, vol. 5, 2012, pages 052601 - 1-052601-3, XP055325494 * |
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EP3109294A1 (en) | 2016-12-28 |
JPWO2016158495A1 (ja) | 2017-04-27 |
CN106211779A (zh) | 2016-12-07 |
CN106211779B (zh) | 2017-06-16 |
US9869777B2 (en) | 2018-01-16 |
US20170160407A1 (en) | 2017-06-08 |
JP6011835B1 (ja) | 2016-10-19 |
HUE039338T2 (hu) | 2018-12-28 |
EP3109294B1 (en) | 2018-08-01 |
RU2627387C1 (ru) | 2017-08-08 |
EP3109294A4 (en) | 2018-01-24 |
UA116850C2 (uk) | 2018-05-10 |
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