An imaging filter for high voltage electron microscopy

An imaging filter suitable for energy-filtered electron microscopy at up to 1.25 MeV has been designed and built. The filter uses a single magnetic sector with curved faces and 25 cm bending radius, 6 strong quadrupole and 5 strong sextupole lenses. It corrects all important aberrations and distortions in both the spectrum and image planes to second order. The filterʹs primary detector is a lens-coupled, 1024 × 1024 pixel slow-scan CCD camera designed for operation above 400 keV. The performance of the filter mounted on three different JEOL ARM microscopes is illustrated with examples including spectra of energy resolution better than 1 eV recorded at 1.25 MeV, zero-loss-filtered images with spatial resolution of 1.1 إ recorded at 1.25 MeV, inner shell loss spectra and elemental maps. The future applications of the filter are discussed briefly.