Readout electronics of a prototype spectrometer for measuring low-energy ions in solar wind plasma

Readout electronics is developed for a prototype spectrometer for in situ measurement of low-energy ions of 30 eV/e-20 keV/e in the solar wind plasma. A low-noise preamplifier/discriminator (A111F) is employed for each channel to process the signal from micro-channel plate (MCP) detectors. A high-voltage (HV) supply solution based on a HV module and a HV optocoupler is adopted to generate a fast sweeping HV and a fixed HV. Due to limitation of telemetry bandwidth in space communication, an algorithm is implemented in an FPGA (field programmable gate array) to compress the raw data. Test results show that the electronics achieves a 1 MHz event rate and a large input dynamic range of 95 pC. A slew rate of 0.8 V/μs and an integral nonlinearity of 0.7-LSB for the sweeping HV, and a precision of less than 0.8% for the fixed HV are obtained. A vacuum beam test shows an energy resolution of 12 ± 0.7% full width at half maximum (FWHM) is achieved, and noise counts are less than 10/sec, indicating that the performance meets the physical requirement. (authors)