The use of the time-energy dispersion in an electron energy analyzer

The time-energy dispersion (TED) characteristics of a spherical electrostatic mirror are used to design an unusual electron energy analyzer. It is shown that TED of a retarding spherical field in an electron mirror configuration is positive and it increases with the electron kinetic energy. This is due to an increasing penetration of electrons with high kinetic energy in the retarding field and provides the basis for developing a new type of time-of-flight spectrometer (TOF). Two limiting cases for the geometry of the proposed spectrometer are considered and for both of them the energy resolution of the TOF device depends on the combined time resolution of electron detector and readout electronics. In the case of a 10-cm inner sphere radius (22 cm outer sphere radius) for the electrostatic mirror, the spectrometer is expected to have an energy resolution of about 0.5 eV/ns and an acceptance solid angle of about 2.2 srad for electrons of 75 eV kinetic energy. A position sensitive detector allows retrieving the energy and the emission angle on the basis of the measured time-of-flight and detection point position. In the second case the inner sphere radius is 6 cm and the outer spherical segment has a radius of 120 cm. The energy resolution is expected to be about 160 meV/ns at the electron kinetic energy of 1 keV and the acceptance solid angle is 0.1 srad. In both cases changing the retarding potential can easily change the energy range within which the TOF analysis is performed. (C) 2003 Elsevier B.V. All rights reserved.