Theory and numerical simulation of some wide-angle wide-bandpass plasma particle analyzers.

摘要

Conventional electrostatic analyzers, employing restrictive apertures and electrically biased plates of many designs, are frequently used to measure plasma velocity distributions in space. In such devices, one recovers the ambient differential flux j of particles in a single channel of energy and solid angle by dividing a collection rate c in a single collector by the geometrical factor G of the device. We propose devices which possess a geometrical matrix G{dollar}sb{lcub}munu{rcub}{dollar}, and deconvolute the ambient particle fluxes j{dollar}sbnu{dollar} from several particle collection rates c{dollar}sbmu{dollar} by inversion of the system c{dollar}sbmu{dollar} = {dollar}Sigmasbnu{lcub}it j/{rcub}sbnu{dollar}. By relaxing the need to focus single energy-angle channels to single collectors, analyzers of wider aperture and hence faster operating speed become possible, but likely at the expense of resolution in energy and angle. In principle one might also use this concept to refine the resolution of analyzers whose energy or angular transmission is wider than the resolution of interest, but likely at the expense of increased measuring error.; We present a method for modelling analyzers employing cylindrically symmetric electromagnetic fields and intended for gyrotropic distributions. We also present a theory for calculating G{dollar}sb{lcub}munu{rcub}{dollar} for such analyzers, and we discuss how this theory could be generalized to more arbitrary geometries. We employ these techniques to study several cylindrically symmetric electrostatic analyzer candidates, and conclude that some show limited promise as analyzers. We suggest that the application of the theory to existing analyzer designs may offer some opportunities to extend their performance.