Channel Multiplier Instrumentation for the Measurement of Low-Energy Auroral Particles

Channel multiplier instruments have been developed and used to measure the low-energy electron and proton auroral fluxes from a polar-orbiting satellite. Seven channel multipliers preceded by individual 90° magnetic analyzers were used to measure the differential electron energy spectrum. The central energies of the analyzers were 1.1, 2.1, 5.3, 14, 31, and 76 keV; the seventh channel was designed to be a background monitor. The integral proton number spectrum was measured using four channel multiplier threshold counters. Proton thresholds, determined by nickel foils, were chosen to be 21, 38, 56, and 1000 keV. A broom magnet was used to sweep out low-energy electrons. The saturated output pulses from each channel multiplier were amplified and fed into a logarithmic ratemeter. The in-flight operation of the instruments was monitored with low-level radioactive sources. The ratemeter calibration was independently monitored using a programmed pulser which was activated by ground command. Data obtained from these instruments during a three-day period in November, 1965, will be presented. Improved versions of these instruments, described herein, have been designed and tested for future flights.