AnnualReport2015
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Photonics technology enables advances in scienceIn 2015, the Nobel Prize in Physics was co-awarded to Professor Takaaki Kajita, Director of the Institute of Cosmic Ray Research (University of Tokyo), who made a signicant discovery that subatomic particles called neutrinos have mass – an experimental result which forces theorists to reconsider the Standard Model of particle physics. Data for this discovery was collected at the Super Kamiokande, an underground facility that was constructed as a higher performance successor to the original Kamiokande detector.In both the Kamiokande and the Super Kamiokande, the “eyes” of the experiment were specially-made large diameter PMTs from Hamamatsu. At the original facility, these unique PMTs helped make the rst-ever observation of neutrinos in 1987, when a team led by Nobel laureate Masatoshi Koshiba (also of the University of Tokyo) observed neutrinos that had originated from a supernova in the Large Magellanic Cloud, a nearby galaxy. The PMTs were then dramatically improved for use in the Super Kamiokande, which began operation in 1996.At the Super Kamiokande, the observation of atmospheric neutrinos over two years indicated their possible mass. This theory was then put to the test in 1999 by articially generating a large number of muon neutrinos with a proton accelerator located roughly 250 km away. The muon neutrinos were directed through the earth at the Super Kamiokande, where Professor Kajita’s team found neutrino oscillation to occur even in these man-made neutrinos and thus concluded that neutrinos have mass. (In this experiment, Hamamatsu’s large-diameter PMTs and large-diameter image intensiers were also used in the proton accelerator.)Hamamatsu is proud to be a part of these great scientic endeavors, and will continue to develop photonics technologies as our way of contributing to the advancement of science.Inside the Super Kamiokande are 11,200 of the 20-inch PMTsLarge diameter 20-inch PMTsTOPICS10

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