Improved cathodoluminescence microscopy

SUMMARY Methods are described for the use of a sensitive photomultiplier, improved photomultiplier voltage supply circuitry, quartz lens and a half‐parabolic mirror to increase the amount of light collected from a luminescing specimen examined in the scanning electron microscope. The combined effect of these improvements increases cathodoluminescence detection twenty times. Sources of background light are investigated and recommendations are made for decreasing this noise component, which seriously limits sensitivity of cathodoluminescence signal detection. An appendix describes the natural luminescence (autoluminescence) of plant tissues under the impact of the electron beam. The biological applications of this mode of scanning microscopy have been little explored, but autocathodoluminescence is found to be of wide occurrence in plant tissues.