High energy electron observation by Polar Patrol Balloon flight in Antarctica

We accomplished a balloon observation of the high-energy cosmic-ray electronsin 10-1000 GeV to reveal the origin and the acceleration mechanism. Theobservation was carried out for 15 days at an average altitude of 35 km by the PolarPatrol Balloon (PPB) around Antarctica in January ,2004. The detector is an imagingcalorimeter composed of scintillating-fiber belts and plastic scintillation counterssandwiched between lead plates. The geometrical factor is about 600 cm^2sr, and thetotal thickness of lead absorber is 9 radiation lengths. The performance of thedetector has been confirmed by a test flight at the Sanriku Balloon Center and by anaccelerator beam test using the CERN-SPS (Super Proton Synchrotron at CERN).The new telemetry system using the Iridium satellite, the power system supplied bysolar panels and the automatic flight level control operated successfully during theflight. We collected 5.7*10^3 events over 100 GeV, and selected the electron candidatesby a preliminary data analysis of the shower images. We report here an outlineof both detector and observation, and the first result of the electron energy spectrumover 100 GeV obtained by an electronic counter