HILT: a heavy ion large area proportional counter telescope for solar and anomalous cosmic rays

The HILT sensor has been designed to measure heavy ion elemental abundances, energy spectra, and direction of incidence in the mass range from helium to iron and in the energy range 4 to 250 MeV/nucleou. With its large geometric factor of 60 cm’sr the sensor is optimized to provide compositional and spectral measurements for low intensity cosmic rays, Le. for small solar energetic particle events and for the anomalous component of cosmic rays. The instrument combines a large area ion drift chamber-proportional counter system with two arrays of 16 Li-drift solid state detectors and 16 CsI crystals. The multi dE/dx-E technique provides a low background mass and energy determination. The sensor also measures particle direction. Combining these measurements with the information on the spacecraft position and attitude in the low altitude polar orbit, it will be possible to infer the ionic charge of the ions from the local cutoff of the Earth’s magnetic field. The ionic charge in this energy range is of particular interest because it provides unique clues to the origin of these particles and has not been investigated systematically so far. Together with the other instruments on board SAMPEX (LEICA, MAST, and PET), a comprehensive measurement of the entire solar and anomalous particle population will be achieved.