The ISS-CREAM Silicon Charge Detector for identification of the charge of cosmic rays up to Z = 26: Design, fabrication and ground-test performance

The Cosmic Ray Energetics And Mass experiment for the International Space Station (ISS-CREAM) is a space-borne mission designed for the precision measurement of the energy and elemental composition of cosmic rays. The Silicon Charge Detector (SCD), placed at the top of the ISS-CREAM payload, consists of 4 layers. Each layer has 2688 silicon pixels and associated electronics arranged in such a fashion that its active detection area of 78.2 × 73.6 cm ² is free of dead area. The foremost goal of the SCD is to efficiently and precisely measure the charge of cosmic rays passing through it. The 4-layer configuration was chosen to achieve the best precision in measuring the charge of cosmic rays within the constraints on the mass, volume and power allotted to it. The amount of material used for its support structure was minimized as well to reduce the chance of interactions of the cosmic ray within the structure. Given the placement of the SCD, its 4-layer configuration and the minimal amount of material in the cosmic-ray trajectory, the SCD is designed to measure the charge of cosmic rays ranging from protons to iron nuclei with excellent detection efficiency and charge resolution. We present the design and fabrication of the SCD as well as its performance during space environment tests which it underwent successfully. We also present its performance in charge measurement using heavy ions in a beam test at CERN, the European Organization for Nuclear Research.