Evaluation of emulsions and other recording media for 100 and 1000kV electron microscopes

Abstract

Since specimens are normally viewed and photographed in the electron microscope at high levels of electron beam radiation damage, it becomes important to choose a recording medium for a particular operating voltage which has the maximum sensitivity to electrons, consistent with the required recording resolution and contrast. It is shown that commonly used emulsions show a wide range of sensitivity. There is a need for manufacturere to specify the electron sensitivity, resolution and contrast of available emulsions over accelerating voltages of 40 to 1000kV and also to specify the X-ray fluorescence and back scatter characteristics for each kind of emulsion backing and cassette material. In addition, the fluorescent light and X-ray sensitivity of each emulsion should be specified. New sensitivity measurements on films and plates are reported. The extra high sensitivity of some X-ray films is emphasized and their usefulness in conventional and high voltage microscopy discussed. Suggestions are made for the manufacture of improved emulsions for high voltage work and for their protection from fogging during use. In addition, high voltage electron microscopy of biological materials requires the availability of high gain image intensifier/TV system for scanning specimens at low radiation levels and for the recording of dynamic images.