Optimizing EELS acquisition.

A method for spectral acquisition, called binned gain averaging, will be described and tested. Systematic or correlated noise is efficiently suppressed with this method by averaging the gain over a series of CCD pixels. As a result, improved signal-to-noise ratios are obtained that allow the detection of very weak signals. At the same time, the spectral energy resolution is not degraded--even for long acquisition periods. It will be demonstrated that with this method, it is possible to significantly enhance the acquisition speed and quality of electron energy-loss (EEL) spectra and EELS maps. Examples will be given of double ionic scattering (i.e. the detection of the second boron K-edge) and the mapping of gold surface plasmons in the near-infrared and visible energy range.