Development of Photo-sensors for 1 Megaton size Proton Decay and Neutrino Detectors

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The goal of this research project is to develop new photo sensors for next generation 1Megaton size proton decay/neutrino detectors. Requirements of the sensor are cheap and having good tinning/charge resolutions. We developed 13inch size prototype of hybrid photo detector (HPD) and performed detailed tests and several, improvements. Here is the list of problems and solutions we reached.1.electric discharge due to 25kV applied to avalanche diodes (AD). → heat up a support insulator when making photo cathode material.2.short lifetime of AD. → develop long life 5mmφ AD3.effective photo cathode area is 240mm out of 300mm. → fine tuning of the position of AD and the shape of the photo cathode surface.4.optimization of HPD structure → made optimization plan to minimize the number of parts and improve the pressure resistance and the shape of the photo cathode surface.From the research above, we conclude that large size HPD has excellent characteristics. (good timing/charge resolution) and there is no big technical problems. We would perform further optimization of the HPD design and cost reduction by enlarge the detector size.