SYMPOSIA PAPER Published: 01 January 1964

Variable Bias Illumination Control for the Electron Microscope


Continuously variable control of illumination intensity in the electron microscope can be achieved by use of photoconductive cells for the grid bias resistance in a self-biased electron gun. The simple, highly stable device consists of several photo cells connected in series facing a control lamp, all positioned in a light-tight compartment. Changing the lamp brightness varies the grid resistance from 500,000 ohms to more than 30 megohms, controlling illuminating beam current over a wide range. Microscope stability is unaffected.

Author Information

McPartland, J.
Ceramics Research Operation, Richland, Wash.
Daniel, J.
Ceramics Research Operation, Richland, Wash.
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Developed by Committee: E04
Pages: 51–53
DOI: 10.1520/STP48333S
ISBN-EB: 978-0-8031-6802-2
ISBN-13: 978-0-8031-6612-7