ΔE×E Silicon Telescope of Energetic Heavy Ions Trapped in Radiation Belts

Abstract

Heavy Ion Telescope (HIT) is an instrument onboard the Japanese satellite “TSUBASA”, which was launched in February 2002 for the observation of heavy ions in radiation belts. The HIT instrument, based on the ΔE×E particle identification method, consists of two position-sensitive silicon detectors and 16 PIN-type Si detectors with 420 µm in thickness. The geometric factor varies from 12 to 18 cm2 sr being dependent on the energy of ions. This instrument was designed to measure the fluxes of heavy ions from He to Fe nuclei in the energy range from 18 to 179 MeV/n, though dependent on the nuclear species to be measured. The nuclear charge separation in this instrument was highly sophisticated as 0.06 charge units for nuclei such as C and O, for instances, in observing energetic ions from He to Fe. Furthermore, isotopic separation was sufficient for the observations of nuclei such as He, Ne, Mg and Si. The observation of energetic ions in radiation belts was successfully achieved during both quiet and disturbed periods of solar activity. The detector system and observational results of ions in the radiation belts are described as the performance of the HIT instrument in space.