The Energetic Particle Telescope

   The Energetic Particle Telescope (EPT) will measure the high-energy particle fluxes with very good energy, angular and mass resolutions. It measures the energy deposited by charged particles into twelve sensitive elements and processes the information to identify the particles (0.2-10 MeV electrons, 4-300 MeV H and 16-1000 MeV He ions) and to determine their energy spectra and angular distribution.
The EPT consists of two "particle telescopes" placed in series separately adapted to low and high-energy ranges. The low-energy section consists of two silicon detectors. The high-energy section is a so-called "range telescope" in which the thicker silicon detector is used as a (DE) sensor and a stack of absorbers and scintillator-based detectors produces a digital measurement of the total energy (E).
The EPT overall dimensions are 205 mm x 205 mm x 190 mm (see Housing box on Figure 2). Its weight is about 6 kg, with the electronic readout included. The power consumption is lower than 6 Watts. The maximum energy-dependent geometrical factor of the detector is ~1.5 cm2sr. The radius of the EPT circular aperture was set to a diameter of 35 mm. The resulting maximum field of view angle is 50 Deg.
Due to the widely varying fluences of electrons, protons and heavy ions within the radiation belts, it was found necessary to provide this instrument with a stunning in-flight particle discrimination capability. This was achieved by performing a thorough characterisation of the EPT by an intensive Monte-Carlo simulation using GEANT4 software (see Model of the sensor assembly in Figure 1). With this optimised design procedure we get background-free counting, even in the channels devoted to particles of very low abundance in space.

The development is carried out under ESA contract 22582/09/NL/AT