The Anticoincidence Shield of the PAMELA Satellite Experiment

Abstract: The PAMELA space experiment is scheduled for launch towards the end of 2004 on-board a Russian Resurs DK1 satellite, orbiting Earth at an altitude of 300– 600 km. The main scientific goal is a study of the antimatter component of the cosmic radiation. The semipolar orbit (70.4◦) allows PAMELA to investigate a wide range of energies for antiprotons (80 MeV–190 GeV) and positrons (50 MeV– 270 GeV). Three years of data taking will provide unprecedented statistics in this energy range and will set the upper limit for the ratio He/He below 10−7. PAMELA is built around a permanent magnet silicon spectrometer, surrounded by a plastic scintillator anticoincidence shield built at KTH. The anticounter scintillators are used to aid in the rejection of background from particles not cleanly entering the acceptance of the tracker. Information from the anticounter system will be included as a veto in a second level trigger, to exclude the acquisition of events generated by false triggers.An LED-based monitoring system has been developed for the anticounter system. The LEDs mimic the light signal produced in the scintillator by an ionising particle. This allows the functionality of the AC system to be verified in-orbit. The development and testing of the monitoring system are presented and comparisons have been made with independent radioactive source-based calibration methods. The anticounter system has also been extensively tested with cosmic rays and particle beams. Most of these tests have been performed with the anticounters integrated with the other PAMELA subdetectors in a flight-like configuration.