Calibration of the High Energy Proton Spectrometer (HEPS) for the demonstration and science experiments (DSX) satellite space weather mission

HEPS was designed to measure high energy protons, with energies between 25 and 400 MeV, in the space environment. The instrument uses a collection of solid state Si particle detectors and Gadolinium Silicate (GSO) crystal scintillators to detect the protons and measure their energy. The sensors form a coaxial arrangement of four Si detectors, to provide an event trigger when struck by an incident proton. The energy measurement for each event is provided by the measurement of its energy losses in the two scintillator elements. Energy losses are determined by photodiodes that collect light produced in GSO by the protons. The HEPS flight unit was extensively calibrated in the 30-217 MeV energy range. The beam measurements were carried out at a series of angles in the instrument field-of-view as well as at larger angles to test its rejection capabilities. An extensive program of computer modeling of HEPS response has been carried out using the Monte Carlo particle interaction code MCNPX. Calibration data will be compared to the results of the calculations. Conclusions concerning the calibrated geometric factors will be discussed.