A Directional, Low Energy Electron Detector Employing Channel Electron Multipliers

A directional, low energy electron detector has been developed for flight aboard the Modular Auroral Probe sounding rocket. Low energy electrons incident in an aperture with a half-angle of 5° are observed at pitch angles of 50° and 130°. At each pitch angle the electron flux is measured as a function of electron energy in the range 1-16 kev. This energy discrimination is accomplished by sweeping the voltage of an electromagnet through values which focus the electrons at 160° into channel electron multipliers. In order to calibrate the instrument, an extensive experimental investigation of the fundamental properties of the recently-developed channel electron multiplier was made. The results of this investigation include values of electron detection efficiency as a function of (1) incident electron energy, (2) pumping time after vacuum conditions have been reached, and (3) orientation of the electron beam on the multiplier aperture. Effects such as variation of count rate and gain as a function of high voltage applied to the multiplier are discussed. Also presented are proton detection efficiencies as a function of incident proton energy in the range 0.1-3.5 kev.