Instrument to Measure Energy and Charge of Low Energy Interplanetary Particles

An experiment to measure the charge composition and energy spectra of ultra low energy charged particles in interplanetary space has been developed and launched on the IMP 8 (Explorer 50) satellite on 26 October 1973. The instrument consists of two separate sensors sharing common electronics. One of these sensors, developed by Max Planck Institut, uses a thin window gas proportional counter to measure the rate of energy loss and a totally depleted silicon surface barrier detector to measure total energy of incoming particles. The energy range for two dimensional analysis extends from 300 KeV to 2.5 MeV for protons and 60 KeV/nucleon to % 25 MeV/nucleon for iron with excellent resolution of individual chemical elements. The other sensor, developed at the University of Maryland, cobines electrostatic deflection with total energy measurements in silicon surface barrier detectors to give the ionic charge and kinetic energy of the particle. The overall energy range of the electrostatic analyzer is from ~125 KeV to ~1.25 MeV for singly charged ions and from 37 KeV/charge to 1.25 MeV/charge for particles with charge ≥4.