| Co-Investigator(Kenkyū-buntansha) |
TORII Shoji Kanagawa University, Faculty of Engineering, Professor, 工学部, 教授 (90167536)
TAMURA Tadahisa Kanagawa University, Faculty of Engineering, Research Associate, 工学部, 助手 (90271361)
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| Budget Amount *help |
¥3,800,000 (Direct Cost: ¥3,800,000)
Fiscal Year 2003: ¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 2002: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
We have performed the basic study of the Total Absorption Calorimeter (TASC) for CALorimetric Electron Telescope (CALET) on-board the International Space Station. At first, we have tested the capability of two kinds of crystal scintillators, bismuth germanate (BGO) and lead tungstate (PbWO_4), as the material of TASC. Although PbWO_4 has advantages such as larger density, shorter radiation length, and lower cost than BGO, we found that the light yield of PbWO_4 is much lower than that of BGO by about 1/50, measuring the light yield of BGO and PbWO_4 with PMT. While BGO can be read-out with photo-diode (PD), PbWO_4 has to be read-out with higher amplified photo-sensors such as PMT or avalanche photo-diode (APD). Therefore we performed Monte-Carlo simulations and experiments with BGO crystals as the material of TASC, in particular, it is required to achieve a proton rejection power of 10^6 for the observation of electrons up to 10TeV. From the simulation studies, we found that TASC with BGO crystals of 32 r. l. can realize this capability, using the relation of energy deposition and lateral spread of showers at the bottom layer of TASC. To confirm this proton rejection power also with experiments, we made a BGO calorimeter for beam test that consists of 26 BGO logs (2.5cm×2.5cm×30cm) with 10 layers, whose BGO crystals are read out with photo-diodes. We performed beam tests with electron (50GeV, 100GeV), proton (150GeV), and muon (120GeV) at CERN-SPS in 2003. Applying the proton rejection method developed with the simulation studies to the BGO calorimeter for beam test, we confirmed the capability of the proton rejection power.
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