A new hemispherical analyser with 2-D PSD and focusing lens for use in 0° electron spectroscopy

A new electron spectrograph has been developed to study electron emission in ion-atom collisions and in particular for use in 0 degrees Auger projectile spectroscopy. It incorporates a hemispherical analyser, a 2-dimensional position-sensitive detector (PSD) with multichannel plates and a resistive anode encoder. A novel feature of this analyser is the use of an asymmetric entrance aperture and a non-zero entrance potential to improve focusing by correcting for fringing field effects. A four-element lens mounted at the entrance of the analyser, provides a virtual slit, focusing and decelerating incoming electrons for improved enery resolution and reduction of the ion beam scattering at the spectrometer entrance. The analyser has an acceptance energy range of 20%. As a first test of the apparatus, the production of Binary Encounter electrons from 20 MeV F-9+,F-8+ + H-2 collisions was measured. The bare F9+ results were used for an in situ calibration of the 2D-PSD overall efficiency. The F8+ data were found to be in good agreement with the elastic electron scattering model. (C) 1998 Elsevier Science B.V. All rights reserved.