| 研究実績の概要 |
One of the primary sources of near-field gravitational waves [GW], core collapse supernova explosions are among the most dramatic and important events to take place in the universe. Supernova neutrinos, famously observed from SN1987A, provide a unique and vital probe into the inner dynamics of these events. Released together with GW during the initial stellar collapse, neutrinos and GW are both certain to travel through any obscuring dust or gas and remain undiminished upon their arrival at Earth. Neutrinos also carry information regarding the end state of the star: for explosions within our galaxy, collapses into neutron stars or black holes, the eventual sources of far-field GW, can be differentiated via observations of neutrino emissions.
During FY2017, we began preparations to upgrade the existing Super-Kamiokande [SK] detector to an advanced-technology, gadolinium-loaded supernova neutrino detector. The first step involved enhancing its online data processing capability to extract the most detailed, accurate supernova neutrino data as rapidly as possible, in order to get word out to the astronomical, neutrino, and GW communities. This was accomplished via the purchase and installation of three custom-built, 28-core high-performance computers in the SK control room. In addition, using the K Computer, 6D Boltzmann supernova simulations were run to explore the explosion mechanism and provide the neutrino spectra, theoretically extracting basic characteristics of neutrino signals emitted from the collapse of massive stars.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
Our ultimate goal is to make theory and experiment work together so we will be ready to make the best possible observations of the next galactic explosion and maximize our extraction of information on the explosion mechanism, progenitor, and nuclear physics ingredients.
We have accomplished what we set out to do this year, and are making good progress toward this ultimate goal. What's more, we have already begun forming strong functional links between our experimental and theory members, vital for efficient future progress in understanding supernova explosions.
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| 今後の研究の推進方策 |
During FY2018, Super-Kamiokande will be drained of water, internally refurbished, and completely inspected. Lessons learned in the pathfinder EGADS project regarding detector cleanliness and material selection will be applied to make SK ready for the addition of gadolinium.This will be the first time for Super-Kamiokande to be drained and serviced since 2006. There will be four main tasks:
1) fix a longstanding water leak in the SK tank; 2) clean up the interior of the detector (i.e., rust removal and re-passivation of the stainless steel surfaces); 3) replace those photomultiplier tubes which have failed since the last maintenance, and; 4) install additional piping inside the tank for better circulation of Gd-loaded water.
After the detector is refilled with ultrapure water, a new Gd-capable selective water filtration system will be commissioned and its ability to maintain the clarity of SK's pure water will be demonstrated. After that, the detector will be ready for enrichment with gadolinium.
On the theory side, additional simulations will be performed to clarify the dependence on progenitors and nuclear physics, and new features of neutrino signals in multi-D supernova explosions will be explored. The theory and experimental groups will continue to work together, including collaborating on joint publications already under discussion.
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