Paul Scherrer Institut

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REM instrument

REM is designed to measure the flux of protons with energies above 30 MeV and electrons with energies above 1 MeV. REM contains two solid state detectors measuring the energy transfer of ionozing particles. Two detectors with different areas and shielding configurations are used making them selective sensitive to different ranges of particle properties (see figure below). Both detectors are covered with a spherical dome of aluminium. One detector has an additional shielding of tantalum. Whereas the detector without tantalum sees protons as well as electrons, the extra tantalum of the other detector reduces the penetration of electrons in the relevant energy range (1-10 MeV) significantly and makes this detector better at monitoring protons. The charge pulses produced by the particles passing through the silicon diodes are measured using charge sensitive pre-amplifier and 12-bit ADCs. In order to reduce the data amount the ADC outputs are compressed into 16-bin histograms.
Cutaway view of REM detectors
Cutaway view of the two REM silicon detectors and their shielding.
The REM instrument includes two modules, the detector suite and the electronics box (see figure below). The detector suite contains the two solid state detectors and the analog readout electronics. Its physical dimensions are 13 x 10 x 8 cm and has a weigth of approximately 1 kg. The electronics box contains the A/D conversion and the digital data processing electronics and provides the interface of the instrument with spacecraft telemetry and power. This unit measures 20 x 16 x 8 cm and weigths 1.8 kg. The maximum total power consumption is less than 5 W.
Scheme of REM detector suite and electronics box layout
Layout of the detector suite and the electronics box.
Reference: Nucl. Instr. and Meth. in Phys. Res. A, 386, 825, 1996 (REM_NIMA96.pdf, 0.3 MB)

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