A new monochromator with multiple offset cylindrical lenses

Abstract

This article presents the optics and performance of a new monochromator (MC) with multiple offset cylindrical lenses (CLs). From ray trace simulations and a regression analysis, a single-offset CL is described in first-order matrix expressions. Based on the matrix, a new optics using multiple CLs is constituted. It is capable of energy filtering internally and forms stigmatic and non-energy dispersive images at the exit. It consists of an offset CL doublet located at a specified distance. It is also equipped with two transfer lenses and two apertures. From simulations, an energy dispersion of 23 µm/eV and an energy resolution better than 10 meV for 4keV incident energy are achieved. Compared to previous MCs with multi-pole optics, the proposed MC has the additional advantage of a simplified structure. This MC realizes improvements in spatial resolutions for transmission electron microscopy, scanning transmission electron microscopy, and scanning electron microscopy and in energy resolutions for electron energy loss spectroscopy.