Measurements of cosmic-ray electron and gamma-ray flux with balloon-borne CALET prototype

We carried out the balloon experiments using CALET (CALorimetric Electron Telescope) prototype detectors in May 2006 (bCALET-1) and August 2009 (bCALET-2) for verification of both the detector performance and the capability of measuring the cosmic rays at higher atmosphere. The bCALET-2 instrument for observing the electrons and the gamma rays at energies in 1-100 GeV is composed of an imaging calorimeter consisting of 4096 scintillating fibers with a total of 3.6 radiation lengths of tungsten plates, and a total absorption calorimeter consisting of crossed 60 BGO logs with a total of 13.4 radiation lengths depth. The bCALET-2 was launched from the Taiki Aerospace Research Field, Japan Aerospace Exploration Agency, in Hokkaido, and flew successfully for 2.5 hours at a level altitude of 35 km. In this paper, we will present the spectra of electrons and gamma rays in the energy range of 1-100 GeV measured by bCALET-2, comparing with our previous observations, bCALET-1 and BETS. The detector performance is studied by comparing with the simulations, and the observed fluxes are found to be compatible with the expected.