COUNTING SLOW ELECTRONS WITH AN ELECTRON MULTIPLIER

Abstract

The efficiency of counting slow velocity electrons by a 12-stage activated beryllium-copper electron multiplier was investigated. The total electron current in the incident beam was measured using an electrometer tube circuit. The number of pulses produced in the multiplier by the whole beam was counted using high speed scaling circuits. The efficiency of counting was thus determined without depending on calibrated slits to divide the beam.Efficiency curves for primary energies between 200 and 900 ev. are shown for freshly activated surfaces and also for surfaces which had been exposed to still air for five months. The curves were similar in shape, the former being a few per cent above the latter. A maximum of 63% was obtained for 300 ev. input energies.