| Project Area | New development in astrophysics through multimessenger observations of gravitational wave sources |
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| Project/Area Number | 24103004 |
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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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| Research Institution | The University of Tokyo |
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Principal Investigator |
ヴァギンズ マーク 東京大学, カブリ数物連携宇宙研究機構, 教授 (90509902)
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| Co-Investigator(Kenkyū-buntansha) |
小汐 由介 岡山大学, 自然科学研究科, 准教授 (80292960)
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| Project Fiscal Year |
2012-06-28 – 2017-03-31
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| Project Status |
Granted(Fiscal Year 2016)
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| Budget Amount *help |
¥119,990,000 (Direct Cost : ¥92,300,000、Indirect Cost : ¥27,690,000)
Fiscal Year 2016 : ¥23,400,000 (Direct Cost : ¥18,000,000、Indirect Cost : ¥5,400,000)
Fiscal Year 2015 : ¥23,400,000 (Direct Cost : ¥18,000,000、Indirect Cost : ¥5,400,000)
Fiscal Year 2014 : ¥26,390,000 (Direct Cost : ¥20,300,000、Indirect Cost : ¥6,090,000)
Fiscal Year 2013 : ¥20,540,000 (Direct Cost : ¥15,800,000、Indirect Cost : ¥4,740,000)
Fiscal Year 2012 : ¥26,260,000 (Direct Cost : ¥20,200,000、Indirect Cost : ¥6,060,000)
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| Keywords | 宇宙線 / 重力波 / 超新星爆発 / ニュートリノ / ガドリニウム |
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| Outline of Annual Research Achievements |
The EGADS (Evaluating Gadolinium's Action on Detector Systems) laboratory is located one km underground in the Mozumi mine in northern Gifu-ken, close to the Super-Kamiokande neutrino detector. Originally designed as an R&D test bed for studying the effects of dissolving gadolinium (Gd) salts in a water Cherenkov detector (Gd makes neutrons visible, which has many potential physics benefits), the purpose of this Kakenhi is to convert EGADS into the world's most advanced supernova neutrino detector.
The past year was one of rebuilding and recovery for EGADS. This was the result of an unfortunate mixup during construction in 2013. All components installed inside the detector must be made of high-grade stainless steel or other non-reactive materials. We were assured by our vendors this would be the case, but one minor component they sold us, a several meter long length of structural support wire, turned out to be made of low-grade, non-stainless iron. After installation it rapidly corroded in the liquid environment inside the detector. About half of the past year was therefore spent carefully cleaning the rust out the detector, repassivating the exposed stainless surfaces, and reassembling the detector using the originally specified materials.
The recovery has been a complete success, and for the past six months the refurbished EGADS detector has once again been full of water (and gadolinium), and has been operating better than ever before. The detector has been carefully calibrated and data taking now takes place 24 hours a day without interruption.
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| Current Status of Research Progress |
Current Status of Research Progress
Research has progressed on the whole more than it was originally planned.
Reason
I feel that (2) is the most representative answer for where the project stands - we are making excellent, steady progress toward our supernova detection goals. This is perhaps surprising, given the six months lost in the past year to the cleanup and recovery of EGADS following the discovery of the bad structural wire.
However, following this repair we have emerged with a detector that not only works better than before, but even better than could have been reasonably expected.
EGADS's all-important selective water filtration system, which keeps the water in the detector clean but does not remove the dissolved gadolinium, was upgraded during the battle against the rust. Now, thanks to this improved system, we have for the first time anywhere achieved - *with* dissolved gadolinium - salted water transparency equivalent to the ultrapure water in Super-Kamiokande. This is a major breakthrough, and will allow the highest possible efficiency for detection of supernova neutrinos. Indeed, EGADS now stands for Employing Gadolinium to Autonomously Detect Supernovas.
No one expected that Gd-loaded water (there are 400 kg of gadolinium sulfate dissolved in the 200-ton EGADS tank) would ever be as transparent at Super-K's ultrapure water, but that is what we are now seeing. This has powerful implications for this new Gd-loading technology, since extremely clear water is key to the success of all large water Cherenkov detectors.
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