Novel charged particle analyzer for momentum determination in the multichanneling mode: I. Design aspects and electron/ion optical properties

Abstract

We present a novel electrostatic, energy-dispersive particle analyzer whose astigmatism can be used to measure the polar angle distribution of charged particles originating in a sample spot, in a multichanneling mode. The analyzer consists of a toroidal prism and a truncated conical lens, both coaxial on an axis through the particle source. The toroidal prism is used in an unusual way, in that the axial radius of the central equipotential surface varies from infinity to a certain minimal value for varying deflection angles in the prism. We develop design criteria for an analyzer using this principle, suitable for measurements on solid samples. The energy resolution of the analyzer lies between those of a 127 ° cylindrical and of a 180 ° spherical analyzer. Angular resolutions of <2.6 ° (FWHM) can be achieved.