An advanced post-column energy filter is being assessed for spectroscopic imaging on a 200-keV transmission electron microscope. The filter is equipped with a series of quadruple and sextuple lenses and a YAG-coupled, cooled, slow-scan CCD camera, which has been shown to have a detective quantum efficiency close to unity for incident fluxes greater than 10 fast electrons per pixel. This performance of the imaging filter has enabled high-quality elemental maps to be recorded from core-edges in the range from 100eV to 500eV, including phosphorus, sulfur, and nitrogen. It has also been shown that spectra containing 10/8 fast electrons per channel can be acquired, corresponding to counting statistics at the 0.01% level. This filter is expected to reduce calcium detection limits below those currently achievable with a photodiode array detector. The imaging filter has also been used to record zero-loss digital micrographs of freeze-etch replicas of cellular structures with enhanced contrast.
