Transmission characteristics and fringing field effect of a 270° spherical electrostatic analyzer

Abstract

Three-dimensional transmission characteristics of a 270° spherical section electrostatic analyzer are studied with respect to both theoretical calculation and calibration experiment. A fairly good agreement is obtained between both results which confirm a well-defined response as a function of energy and angle of incident particles and a high-resolution ability of a 270° analyzer in contrast with a 90° analyzer which has a strong energy-angle coupling. A particular particle guide is used as the entrance slit of our analyzer in order to suppress the fringing field effect. When we replace this particle-guide slit by a simple slit of square shape, the transmission characteristics of the analyzer become distant from the calculated one. The numerical solution of a two-dimensional fringing field of an approximated model is derived and the ray tracing calculation of particles in this field is done. This model calculation approach also suggests the strong effect of the fringing field near the entrance aperture in the case of the analyzer with a simple slit. These investigations demonstrate the effectiveness of the particular slit at the entrance aperture used.