2018 Fiscal Year Final Research Report
Research on history of star formation through observations of supernova relic neutrinos
| Project Area | Revealing the history of the universe with underground particle and nuclear research |
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| Project/Area Number |
26104006
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| Research Category |
Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
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| Allocation Type | Single-year Grants |
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| Review Section |
Science and Engineering
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| Research Institution | Okayama University |
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Principal Investigator |
SAKUDA MAKOTO 岡山大学, 自然科学研究科, 教授 (40178596)
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| Co-Investigator(Kenkyū-buntansha) |
高久 雄一 公益財団法人環境科学技術研究所, 環境影響研究部, 研究部長 (40715497)
井上 睦夫 金沢大学, 環日本海域環境研究センター, 准教授 (60283090)
鈴木 英之 東京理科大学, 理工学部物理学科, 教授 (90211987)
池田 一得 東京大学, 宇宙線研究所, 助教 (90583477)
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| Research Collaborator |
NAKAZATO ken'ichiro
KOSHIO yusuke
ITO shinrato
SEKIYA hiroyuki
NAKAHATA masayuki
ALI Ajmi
PRONOST guillaume
BENHAR omar
ANKOWSKI artur
LORENZ sebastian
DHIR rohit
PRONOST guillaume
TOGASHI hajime
FURUSAWA shun
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| Project Period (FY) |
2014-07-10 – 2019-03-31
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| Keywords | 超新星背景ニュートリノ / 超新星爆発ニュートリノ / 極低放射線環境 / ガドリニウム熱中性子捕獲γ線 |
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| Outline of Final Research Achievements |
The SK-Gd project is a new experiment in which 0.2% gadolinium sulfate octahydrate will be loaded into the water Cherenkov detector of SK. The main goal of SK-Gd is to discover supernova relic neutrinos. When the material of gadolinium sulfate octahydrate is manufactured commercially at a company, it contains radioactive impurities (U, Th, Rn). After developing how to measure those impurities in the material and also in a test at a 200-ton Gd-loaded water Cherenkov detector, we have found that the level of radioactive impurities in the material after reducing those impurities at the production stage is less than our goal (0.3mBq/(Gd sulfate)kg and the water transparency is better than 77% (at 15m of water). The results have fulfiled our initial goal and convinced the SK collaborators to start the SK-Gd project. In addition, the theoretical development of supernova relic neutrinos and the development of gamma-ray decay model of the thermal neutron capture were successfully performed.
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| Free Research Field |
素粒子原子核物理学実験
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| Academic Significance and Societal Importance of the Research Achievements |
領領域内の連携により原料Gd化合物中の放射性不純物除去開発と水循環装置での陽イオン交換樹脂の開発を行い、低放射線バックグラウンドかつ高い水透過率(水15mに対するチェレンコフ光の透過率77%)が実現できた。従って、本研究の第1目標であった世界最先端のSK-Gd実験（超新星背景ニュートリノSRN観測）開始条件を達成できた。SRNだけでなく太陽ニュートリノも低閾値で継続観測できる。実験開始に伴うSRNモデルの理論的精密化もWeb公開され、Gd熱中性子捕獲γ線生成モデルの精密化もWeb公開された。本研究は、当初目標を完全に達成し、今後、SK-Gd実験開始により世界初のSRN観測が期待できる。
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