TEARES: a toroidal energy- and angle-resolved electron spectrometer

The toroidal energy- and angle-resolved electron spectrometer (TEARES) is a state-of-the-art high-resolution electron detector, which measures both the energy and ejection angle of electrons simultaneously over a range of angles. A double-focus sing cylindrical slit entrance lens transports and focusses electrons that are ejected near the plane perpendicular to the main axis of the spectrometer and which originate from an interaction volume of approximately I mm(3) to the entrance of the toroidal analyser. In addition, the lens adjusts the kinetic energy of the electrons to be analysed to match the pass energy of the analyser with a relatively constant unit magnification. The toroidal deflector analyser is comprised of an inner and an outer toroidal sector, which disperses and focuses the electrons according to their energy in the radial dimension, it is defined by a spherical radius of 125 mm, a cylindrical radius of 120 mm and a sector angle of 142degrees. These dimensions have been chosen to ensure optimum focussing properties. A I mm high entrance slit provides an analyser resolution (DeltaE/PE) of 0.0081 (= 1/125). A single-focus sing conical slit exit lens transports, demagnifies, focuses and accelerates the electrons from the exit of the analyser onto an imaging detector. Electrons travel through the spectrometer with their initial angular direction preserved. The whole of the spectrometer has no blind spots and incorporates a working distance defined by a 38-40 rum radius. The TEARES system is designed to operate over a kinetic energy range of < 0.5 less than or equal to KE less than or equal to 1000 eV and a pass energy range of similar to0.5 less than or equal to PE less than or equal to 25 eV with a useful angular range of similar to230degrees. Crown Copyright (C) 2004 Published by Elsevier B.V. All rights reserved.