Efficient energy spectrometer for charged particle detection in surface studies

Abstract

We have recently built a spectrometer that efficiently collects the energy spectrum of charged particles that emerge from targets bombarded by low-flux (10−15 A) incident beams. The spectrometer is used to detect positron-induced secondary electrons and low-energy positron-stimulated Auger electron emission. Slow positrons and positron-induced secondary electrons are generated from a cold neon positron moderator deposited onto an encapsulated 22Na source. The moderated beam is magnetically transported to the target with two sets of E×B plates. The particles emerging from the target are energy dispersed by a third set of plates and are detected with a one-dimensional position-sensitive detector. The data-collection rate for the energy-distribution spectrum is ∼10–100 times faster for this experiment relative to the more common method of sweeping grids or the plates.