Analytic expression for non-linear ion extraction fields which yield ideal spatial focusing in time-of-flight mass spectrometry

摘要

One of the factors limiting the achievable mass resolution in time-of-flight mass spectrometers is the non-zero extent of the ion spatial distribution along the dimension parallel to the extraction axis. The effects of this spatial distribution are normally minimized by placing the detector at the position along the flight path where the temporal spread of an isomass ion packet is minimized. This position is known as the space-focus plane. In this paper, an analytic expression is obtained for the non-linear field in the extraction region which would yield theoretically perfect ion packet focusing at the space-focus plane. The mathematical techniques required are those commonly used in the solution of calculus of variations problems.