A study of the Double-pass Jost Electron Energy Analyzer

Abstract

A Double-pass Jost Electron Energy Analyzer (modified spherical electron energy analyzer) including a four-element input lens has been constructed for studies of gases and high temperature vapors. Its electron optical properties have been studied by numerical ray-tracing calculation. Effects of separate factors affecting the resolution have been studied by calculating corresponding partial broadening functions. A total resolution function is obtained as the convolution of partial broadening functions. An advantage of this method is that complete profile of partial and total broadening functions is obtained, thus making optimization easier and more reliable. The calculated results have been compared with experimental results and close agreement has been found. According to the calculations and practical measurements a reasonable slit width for this analyzer is between 0.65 and 1 mm. The most critical factors concerning the energy resolution are the vertical and horizontal angular acceptances Δ θ and Δ α, for which obtained, acceptable, upper limits are Δ θ=±3.2°, and Δ α=±6° for the 0.65 mm slits. The numerical deconvolution of a single, well-separated Ar 1S 0 peak of the L 2,3M 2,3M 2,3 group gives the spectrometer function, which is fairly close to a Gaussian shape of 140±8 meV (FWHM) and gives 0.64%, after correction for Doppler effect, for the relative energy resolution at a 20 eV the pass energy. Line widths Δ E exp (FWHM) of Ar 1S 0 measured at six pass energies – 3, 5, 10, 20, 30 and 50 eV – give the values: n=1.303±0.042, Δ E Rest=48.50±7.20 meV and resolution R=0.76±0.13% using least-squares optimization of equation Δ E n exp=Δ E n Lor+Δ E n Doppler+( R· E pass) n +Δ E n Re st .