A Novel Monochromator with Double Cylindrical Lenses

Abstract

Recently, various types of monochromators (MCs) have been proposed for advanced instruments such as the (scanning) transmission electron microscope ((S)TEM) [1,2], the scanning electron microscope (SEM) [3], and microscopes that utilize electron energy loss spectroscopy (EELS). There are several advantages with regard to the use of MCs. First, these devices offer improvements in the spatial resolution in low-energy regimes by reducing the contribution of chromatic aberrations. Second, they offer improvements in the energy resolution of the EELS spectra. Further improvements are necessary to reveal new information about specimens, such as the phonon signals. In addition, industry applications require simple and robust structures for MCs. In this study, we propose a novel MC with a high energy resolution and a simple structure. It consists of two electrostatic cylindrical lenses (CLs) in highly excited retarding mode, similar to a Möllenstedt energy analyzer [4]. They are placed in mid-plane symmetry and both are shifted from the optical axis of a microscope. A detailed discussion of the MC is given below.

A Novel Monochromator with Offset Cylindrical Lenses and Its Application to a Low-Voltage Scanning Electron Microscope

“…In a series of studies, we have proposed and investigated a new MC based on an optical system using offset cylindrical lenses (CLs; Ogawa et al, 2015 a ). The highly excited CLs in an offset layout generate large energy dispersion and high energy-filtering capability.…”