Research on the co-doping effects of 4-6 group cations on scintillation properties in various Ce doped single crystal scintillators and their performance improvement mechanism

2019 Fiscal Year Research-status Report

• Project/Area Number: 19K12626
• Research Institution: Tohoku University
• Principal Investigator: 金 敬鎭 東北大学, 金属材料研究所, 学術研究員 (10521768)
• Co-Investigator(Kenkyū-buntansha): 鎌田 圭 東北大学, 未来科学技術共同研究センター, 准教授 (60639649)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: シンチレータ / 結晶成長 / 共添加 / LYSO / GAGG / LuAG

Outline of Annual Research Achievements

本研究の目的は、Ce:(Lu,Y)2SiO5 (LYSO)、 Ce:Gd3(Ga,Al)5O12 (GAGG)、Ce:Lu3Al5O12 (LuAG)、Ce:LaBr3といった、バンド構造や各種欠陥の発生要因が異なるシンチレータに対し、4~6族陽イオンを共添加することで、各シンチレータに対する特性改善メカニズムを解明することにある。さらに、添加元素、添加量の最適化を各シンチレータに対し実施し、発光量、エネルギー分解能、蛍光寿命、放射線応答の線径性といったシンチレータ特性の最大化も狙う。
2019年度には、まず各シンチレータに対する共添加元素の添加量の最適化を行うべく、 Ce:LYSO、Ce:GAGG、Ce:LuAGのホスト結晶に対し、Zr, Hf, V, Nb, Ta, Mo, Wの7種の共添加イオンを200, 500, 1000, 3000ppm添加した結晶をMicro-pulling-down（m-PD）法により育成した。得られた結晶に対し、加工研磨ののち光学、発光量、蛍光寿命を評価し、共添加イオンとシンチレータ特性変動との関連性を現象論的に明確化した。Ce:LaBr3ホスト結晶の場合、m-PD法ではなく、Vertical Bridgeman（VB）装置を用いて育成を行った。1回に1つの結晶育成ではなく、共添加されていないCe:LaBr3と共添加元素の添加量変えた多数の結晶を同時に育成するためのホットゾーンと治具を検討し、作製された治具を用いた育成テストに成功した。
また、1インチCz法を用いた結晶育成条件とホットゾーンの検討を行い、LYSO、GAGG、LuAGのホスト結晶の成長条件を早期に確保することができた。これを基に次年度の共添加した1インチ結晶育成と検討がよりスムーズに行われることができると考えられる。

Current Status of Research Progress

2: Research has progressed on the whole more than it was originally planned.

Reason

m-PD法を用いた最適組成探索のための結晶成長は順調に行われた。Ce:LYSO、Ce:GAGG、Ce:LuAGのホスト結晶に対し、Zr, Hf, V, Nb, Ta, Mo, Wの7種の共添加イオンを200, 500, 1000, 3000ppm添加した結晶をm-PD法により育成した。成長した結晶に対し、光学研磨を行った後、結晶組成、結晶相の分析を実施し、光学、発光、シンチレータ特性評価を順次行った。これにより、各シンチレータホスト結晶におけるZr, Hf, V, Nb, Ta, Mo, W共添加のシンチレータ特性に与える影響を計画通りに探索することができた。さらに、1インチCz法を用いた結晶育成条件とホットゾーンの検討を行い、LYSO、GAGG、LuAGのホスト結晶の成長条件を早期に確保することができた。これを基に、2020年度の研究が加速化可能と考えられ、計画よりも順調に研究が進捗している。

Strategy for Future Research Activity

2020年度には第2ステップとして、m-PD法による組成探索の結果判明した、共添加元素、添加量を含め結晶組成に対し、1インチサイズでのチョクラルスキー（CZ）法により結晶作製を行い、前年度と同様に作製結晶のシンチレータ特性を評価することで、発光量、蛍光寿命に加え、エネルギー分解能、放射線応答の線径性を確定する。厳密なエネルギー分解能、放射線応答の線径性評価には、サンプル中のCeおよび共添加イオン濃度が十分に均一であり、結晶性が良い、10㎜cubic以上の結晶が必須である。高速育成、高速スキャンのm-PD法と、高品質、大型、組成均一性に優れるCZ法の優位点を活かした、材料研究を展開する。
m-PD法による最適組成探索と並行し、現状で良好な結果が得られているMo, W共添加イオンについて、1インチサイズでのCZ法により各共添加イオンとCe仕込み濃度における結晶作製を行い、共添加元素偏析係数の評価と最適共添加仕込み量を決定する。m-PD法での検討結果に従い他の共添加元素についても、順次Cz法による結晶作製と評価のフィードバックを進める。
また、Ce:LaBr3ホスト結晶もVB法による最適組成探索と並行し、1インチサイズでの結晶作製を行い、作製結晶のシンチレータ特性を評価する。

Research Products

• [Journal Article] Tungsten co-doping effects on Ce:Gd3Ga3Al2O12 scintillator grown by the micro-pulling down method (2020)
  • Author(s): Ueno Mutsumi、Kim Kyoung Jin、Kamada Kei、Nihei Takayuki、Yoshino Masao、Yamaji Akihiro、Toyoda Satoshi、Sato Hiroki、Yokota Yuui、Kurosawa Shunsuke、Ohashi Yuji、Nikl Martin、Kochurikhin Vladimir、Yoshikawa Akira
  • Journal Title: Journal of Crystal Growth Volume: 539 Pages: 125513～125513
  • DOI: 10.1016/j.jcrysgro.2020.125513
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Multiple shaped-crystal growth of oxide scintillators using Mo crucible and die by the edge defined film fed growth method (2020)
  • Author(s): Kamada Kei、Nikl Martin、Kotaki Toshiro、Saito Hironori、Horikoshi Fumiya、Miyazaki Masayuki、Kim Kyoung Jin、Murakami Rikito、Yoshino Masao、Yamaji Akihiro、Shoji Yasuhiro、Kurosawa Shunsuke、Toyoda Satoshi、Sato Hiroki、Yokota Yuui、Ohashi Yuji、Kochurikhin Vladimir、Yoshikawa Akira
  • Journal Title: Journal of Crystal Growth Volume: 535 Pages: 125510～125510
  • DOI: 10.1016/j.jcrysgro.2020.125510
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] High-light-yield calcium iodide (CaI2) scintillator for astroparticle physics (2020)
  • Author(s): Iida Takashi、Kamada Kei、Yoshino Masao、Kim Kyoung Jin、Ichimura Koichi、Yoshikawa Akira
  • Journal Title: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment Volume: 958 Pages: 162629～162629
  • DOI: 10.1016/j.nima.2019.162629
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Czochralski growth of 4-inch diameter Ce:Gd3Al2Ga3O12 single crystals for scintillator applications (2020)
  • Author(s): Kochurikhin Vladimir、Kamada Kei、Jin Kim Kyoung、Ivanov Mikhail、Gushchina Liudmila、Shoji Yasuhiro、Yoshino Masao、Yoshikawa Akira
  • Journal Title: Journal of Crystal Growth Volume: 531 Pages: 125384～125384
  • DOI: 10.1016/j.jcrysgro.2019.125384
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Crystal growth and scintillation properties of Eu-doped Ca(BrxI1-x)2 crystals (2019)
  • Author(s): Kamada Kei、Iida Takashi、Furuya Yuki、Kim Kyoung Jin、Yoshino Masao、Murakami Rikito、Shoji Yasuhiro、Kochurikhin Vladimir V.、Yamaj Akihiro、Kurosawa Shunsuke、Ohashi Yuji、Yokota Yuui、Yoshikawa Akira
  • Journal Title: Radiation Measurements Volume: 127 Pages: 106139～106139
  • DOI: 10.1016/j.radmeas.2019.106139
  • Peer Reviewed / Int'l Joint Research
• [Presentation] Study on a Multi-Photon Gamma-Ray Coincidence Imaging Method 2 (Development of Scintilaltors) (2020)
  • Author(s): Kei Kamada, Kyoung Jin Kim, Masao Yoshino, Yasuhiro Shoji, Akihiro Yamaji, Shunsuke Kurosawa, Yuui Yokota, Yuji Ohashi, Kenji Shimazoe, Miwako Takahashi, Hiromitsu Haba, Toshimitsu Momose, Hiroyuki Takahashi, Akira Yoshikawa
  • Organizer: 2020 第67回 応用物理学会 春季学術講演会
• [Presentation] The development and performance evaluation of 1 mm-pixelated CeBr3 scintillator arrays (2019)
  • Author(s): Masao Yoshino, Kyoung Jin Kim, Kei Kamada, Yuui Yokota, Shunsuke Kurosawa, Akihiro Yamaji, Yasuhiro Shoji, Yuji Ohashi, Hiroki Sato, Kazuya Fujieda, Ryo Tanaka, Jun Kataoka, And Akira Yoshikawa
  • Organizer: 15th International conference on Scintillating Materials and their Applications (SCINT2019)
  • Int'l Joint Research
• [Presentation] Effects of 4-6 group ions co-doping on luminescence and scintillation properties in Ce doped Gd3(Ga,Al)5O12 single crystals (2019)
  • Author(s): Mutsumi Ueno, Kyoung Jin Kim, Kei Kamada, Takahiro Nihei, Masao Yoshino, Akihiro Yamaji, Shunsuke Kurosawa, Yuui Yokota, Yuji Ohashi, Akira Yoshikawa
  • Organizer: 15th International conference on Scintillating Materials and their Applications (SCINT2019)
  • Int'l Joint Research
• [Presentation] Development of calcium iodide (CaI2) scintillator for the study of double beta decay of 48Ca (2019)
  • Author(s): Takashi Iida, Kei Kamada, Masao Yoshino, Kyoung Jin Kim, Akira Yoshikawa
  • Organizer: 15th International conference on Scintillating Materials and their Applications (SCINT2019)
  • Int'l Joint Research
• [Presentation] Effect of Mo co-doping on scintillation properties of Ce:Gd3(Ga, Al)5O12 single crystal scintillators with various Al-to-Ga ratios (2019)
  • Author(s): Kyoung Jin Kim, Kei Kamada, Masao Yoshino, Yasuhiro Shoji, Vladimir V. Kochurikhin, Akihiro Yamaji, Satoshi Toyoda, Hiroki Sato, Shunsuke Kurosawa, Yuui Yokota, Yuji Ohashi, Akira Yoshikawa
  • Organizer: 2019 第80回 応用物理学会 秋季学術講演会
• [Presentation] Effect of Mo co-doping to Yttrium-aluminum oxcide scintillators (2019)
  • Author(s): Mutsumi Ueno, Kyoung Jin Kim, Kei Kamada, Takayuki Nihei, Masao Yoshino, Akihiro Yamaji, Satoshi Toyoda, Hiroki Sato, Shunsuke Kurosawa, Yuui Yokota, Yuji Ohashi, Akira Yoshikawa
  • Organizer: 2019 第80回 応用物理学会 秋季学術講演会
• [Presentation] Growth and characterization of Ce:LaBr3 based eutectic systems (2019)
  • Author(s): Kei Kamada, Hiroyuki Chiba, Yuki Furuya, Kyoung Jin Kim,Masao Yoshino, Rikito Murakami, Yasuhiro Shoji, Vladimir V. Kochurikhin, Akihiro Yamaji, Shunsuke Kurosawa, Yuji Ohashi, Yuui Yokota, Akira Yoshikawa
  • Organizer: The Sixth Directionally Solidified Eutectics Conference (DSEC VI)
  • Int'l Joint Research
• [Presentation] Development of X-ray Talbot-Lau imaging system using large area Tb doped GAP/α-Al2O3 eutectic scintillator plates (2019)
  • Author(s): Kei Kamada, Akihiro Yamaji, Nobuhiro Yasui, Ryota Ohashi, Toru Den, Kyoung Jin Kim, Shunsuke Kurosawa, Yasuhiro Shoji, Yuui Yokota,Yuji Ohashi, Akira Yoshikawa
  • Organizer: The Sixth Directionally Solidified Eutectics Conference (DSEC VI)
  • Int'l Joint Research
• [Presentation] Difference of Mg2+ and Mo6+ co-doping effects on luminescence and scintillation properties of Ce:LuAG single crystal scintillators (2019)
  • Author(s): Kyoung Jin KIM, Kei KAMADA, Masao YOSHINO, Yasuhiro SHOJI, Vladimir KOCHURIKHIN, Akihiro YAMAJI, Satoshi TOYODA, Shunsuke KUROSAWA, Yuui YOKOTA, Yuji OHASHI, Akira YOSHIKAWA
  • Organizer: 8th International Workshop on Photoluminescence in Rare Earths: Photonic Materials and Devices (PRE'19)
  • Int'l Joint Research
• [Presentation] Comparison of Mo ion co-doping effects in Ce:Y3Al5O12 and Ce:YAlO3 single crystal scintillators (2019)
  • Author(s): Mutsumi UENO, Kyoung Jin KIM, Kei KAMADA, Takayuki NIHEI, Masao YOSHINO, Akira YAMAJI, Hiroki SATO, Shunsuke Kurosawa, Yuui YOKOTA, Yuji OHASHI, Akira YOSHIKAWA
  • Organizer: 8th International Workshop on Photoluminescence in Rare Earths: Photonic Materials and Devices (PRE'19)
  • Int'l Joint Research
• [Presentation] Single crystal growth and scintillation properties of Mo co-doped Ce:LYSO crystals (2019)
  • Author(s): Kyoung Jin Kim, Kei Kamada, Masao Yoshino, Yasuhiro Shoji, Vladimir Kochurikhin, Akihiro Yamaji, Shunsuke Kurosawa, Yuui Yokota, Yuji Ohashi, Akira Yoshikawa
  • Organizer: 19th International Conference on Crystal Growth and Epitaxy (ICCGE-29)
  • Int'l Joint Research
• [Presentation] Development of mass production technology of Ce:Gd3(Ga,Al)5O12 scintillator for radiation imaging applications (2019)
  • Author(s): Kei Kamada, Yasuhiro Shoji, Vladimir Kochurikhin, Gushchina Liudmila, Masao Yoshino, Kyoung Jin Kim, Akira Yamaji, Yuui Yokota, Yuji Ohashi, Akira Yoshikawa
  • Organizer: 19th International Conference on Crystal Growth and Epitaxy (ICCGE-29)
  • Int'l Joint Research / Invited
• [Presentation] Multiple shaped crystal growth of oxide scintillators using Mo crucible and dies by the edge defined film fed growth method (2019)
  • Author(s): Kei Kamada, T. Kotaki, H.Saito, F. Horikoshi, M. Miyazaki, Masao Yoshino, Akihiro Yamaji, Kyoung Jin Kim, Shunsuke Kurosawa, Yuui Yokota, Yuji Ohashi, Akira Yoshikawa
  • Organizer: 19th International Conference on Crystal Growth and Epitaxy (ICCGE-29)
  • Int'l Joint Research
• [Presentation] Comparison co-doping effects between Mg and W on Ce:Gd3Ga3Al2O12 scintillator grown by micro pulling down method (2019)
  • Author(s): Mutsumi Ueno, Kyoung Jin Kim, Kei Kamada, Takayuki Nihei, Masao Yoshino, Akira Yamaji, Shunsuke Kurosawa, Yuui Yokota, Yuji Ohashi, Hiroki Sato, Akira Yoshikawa
  • Organizer: 19th International Conference on Crystal Growth and Epitaxy (ICCGE-29)
  • Int'l Joint Research
• [Presentation] Bulk single crystal growth of W, Ce:Gd3Ga3Al2O12 by Czochralski method and their uniformity of scintillation properties (2019)
  • Author(s): Mutsumi Ueno, Kyoung Jin Kim, Kei Kamada, Takayuki Nihei, Masao Yoshino, Akira Yamaji, Hiroki Sato, Shunsuke Kurosawa, Yuui Yokota, Yuji Ohashi, Akira Yoshikawa
  • Organizer: 19th International Conference on Crystal Growth and Epitaxy (ICCGE-29)
  • Int'l Joint Research
• [Presentation] Single crystal growth of undoped and Tb doped Lu2O3 and HfO2 by indirect heating growth method using arc plasma (2019)
  • Author(s): Rikito Murakami, Kei Kamada, Vladimir Kochurikhin, Kyoung Jin Kim, Yasuhiro Shoji, Masao Yoshino, Akihiro Yamaji, Shunsuke Kurosawa, Yuji Ohashi, Yuui Yokota, Akira Yoshikawa
  • Organizer: 19th International Conference on Crystal Growth and Epitaxy (ICCGE-29)
  • Int'l Joint Research