Observation of TeV Electrons in Collaboration with NASA

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We have developed a new-type electron detector(BETS) for balloon observations to resolve the acceleration mechanism of electrons in super nova. We have successfully carried out several balloon flights in Japan for measuring the electron energy spectrum from 10 GeV to a few hundred GeV. For measuring the electrons in TeV region, it is necessary to carry out a long term observation as 100 days, and we have tried to make a proposal for the NASA Research Announcement of Ultra Long Duration Ballooning(ULDB) in collaboration with NASA members. We have organized a Japan-US collaboration team for the common proposal, and we had some workshops both in Japan and US. The proposal was not accepted with a grade of "Very Good", and we are trying to be successful in next chance.As other opportunities of ULDB, we have a plan to do a long observation with a Polar Patrol Ballon(PPB) by National Institute of Polar Research in Japan and the trans-continental long duration ballooning between Brazil and Australia by Institute of Space and Astronautical Science(ISAS). Our ISAS members have visited Brazil for the planning. Both of them are very promising for balloon flights within a few years. As a future project, we are proposing a 3-year observation of electrons at Japanese Experiment Module/Exposure Facility on International Space Station. A collaboration plan for this was discussed between us and the US collaborators.We have also carried out developments of instruments at GERN by using the proton beams. As a result, it is proved the 64-anode PMT by Hamamatsu Photonics Co. Ltd has enough capability to detect a minimum ionizing particle for 1mm square scintillating fibers. We have, moreover, done simulation calculations for the detector design and theoretical studies on the relation between high-energy electrons and gamma-ray and for the diffusion characteristics of electrons in the Galaxy.