A Trochoidal Monochromator to Measure Electron Beam Energy Distribution in Axial Magnetic Field

Abstract: The trochoidal monochromator is commonly used to produce a monoenergetic electron beam in an axial magnetic field. By adding a retarding electric field system at the entrance, and a Faraday cup at the exit of the monochromator, such a dispersive device can be used to measure the energy dismbution of an electron beam. An experimental set-up composed of an electron gun and the trochoidal analyser is described. A monoenergetic cold beam is produced and analysed in an axial magnetic field. This set-up will be used in a travelling wave tube in order to study wave particle interactions. A ExB energy analyser for electrons has been used by W. L. Barr and W. A. Perkins[l] to measure energy distribution functions of the "hot electron plasma " produced in a compression mirror machine. This analyser works with electron energies up to 20 keV with 1,2 kG. The use of trochoidal motion of electrons in crossed electric and magnetic field for energy dispersion was first reported by Stamatovic and Shulz[2]. The trochoidal monochromator has been used to prepare monoenergetic electron beams for electron transmission and dissociative attachment studies. Recently, M. Allan[3] uses a trochoidal analyser both to prepare a beam of monoenergetic electron and to analyse the energy of the scattered electrons. With two analysers in series and several attemps to overcome severe background problems, he presented a 36 meV resolution for this instrument. The analyser described here can determine th