Plasma Electron Detector Using an Open Electron Multiplier

The Triaxial Electron Spectrometer, scheduled for flight on the OGO-E spacecraft, measures flux and energy distributions of electrons reaching the detector with from zero to 10 kilovolts energy. Electrons are analyzed in a curved-plate, electrostatic analyzer, and detected with a windowless continuous-dynode electron multiplier. The multiplier is operated in a constant-output, variablegain, current mode as the null detector in a feedback circuit. Five decades of dynamic range for flux measurements are obtained with a logarithmically compressed analog telemetry signal. Tests of the gain stability of two different channel multipliers have been made for periods of up to 850 hours. These tests indicate that the gain loss can be limited to a factor of two or three during the one year lifetime of the spacecraft.