SEDL / STP / STP372-EB / STP48333S

Variable Bias Illumination Control for the Electron Microscope

McPartland, J. O.
Engineer and senior scientist, Ceramics Research Operation, Richland, Wash.

Daniel, J. L.
Engineer and senior scientist, Ceramics Research Operation, Richland, Wash.

Pages: 3    Published: Jan 1964

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Abstract

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.