Modification of a transmission electron microscope to give energy-filtered images and diffraction patterns, and electron energy loss spectra

Abstract
A magnetic spectrometer of the Castaing-Henry type has been incorporated between the objective and intermediate lenses of a conventional 100 keV transmission electron microscope (AEI EM6). The electron optics of the spectrometer were adjusted to give semistigmatic focusing, allowing an overall energy resolution of 2 eV in spectra and energy selected images. Making use of the hysteresis properties of the magnetic circuit, energy-selected diffraction patterns are also obtained, with an energy window of about 8 eV. An electron counting system was incorporated to allow accurate recording of energy loss spectra. A simple Zener diode circuit is described, which provides calibration of the energy loss to within +or-0.2% for losses up to 690 eV.