Design and Characterization of a double-layered silicon charge detector for cosmic ray measurements in CALET

CALET (CALorimetric Electron Telescope) is a space instrument to explore a new frontier at higher energies for the cosmic-rays (electrons, gamma rays and heavy nuclei) and to search for dark matter.1 This mission is designed for a long exposure observation on the external JEM-EF facility aboard the International Space Station. It is optimized for the search of nearby sources of acceleration of cosmic ray electrons in the TeV energy range and gamma rays up to several TeV range. It can also extend the available data on cosmic ray composition and on secondary-to-primary ratios to higher energies allowing to discriminate among different propagation models and to derive the acceleration spectra at the source. An accurate measurement of the charge of the incoming particle is performed in CALET by a double-layered array of pixelated silicon sensors (Silicon Array or SIA), covering a seamless sensitive area of the order of 0.3 m2 and providing single-element identification up to Fe and above. The design of SIA instrument and its characterization are presented.