Design of rotationally symmetrical electrostatic mirror for time-of-flight mass spectrometry

Abstract

In order to be able to use it in time-of-flight mass spectrometry, we have tried to find a mirror with as few spherical and chromatic aberrations as possible. We have studied the characteristics of the mirror with charged particles whose initial energy varies by ±1% around a central value and which go through an imaginary input pupil of radius 0.2 ρ (ρ being the radius of the three cylinders which go to make up the mirror). The best operating conditions are calculated for different source points on the axis, taking into account separate residual chromatic and spherical aberrations, and also in the case of simultaneous chromatic and spherical aberrations. The second part of the paper deals with flight time (internal mirror flight time and object-image flight time). The data enable us to establish that this convergent mirror plays an essential compensating role; it eliminates not only the initial energy spread effects, but also those of the ion bunch divergence. Consequently, all the above-mentioned particles have a flight time which is virtually constant.