Electronic Image Intensification: Image Intensifier Using Cathodo-Conductivity

Recent work on an electron microscope image intensifier has established that thin films of amorphous selenium can give charge multiplication in the region of 2000 when bombarded with high energy electrons. A sealed-off tube achieving prescanning amplification in a similar selenium film is described. — In the “writing” function, electrons from a semitransparent photoemissive cathode are focused and accelerated into a 10-μ self-supporting selenium film. The provision of an electron transparent signal plate on the front surface of the film enables charges to be driven to the rear whence they are removed by a low-voltage scanning beam which returns the surface to reading gun cathode potential. Electrostatic scanning is used in combination with retarding field electrodes to achieve orthogonality. — Overall sensitivity is dependent on both photo-cathode efficiency and charge multiplication in the selenium—which is itself a function of the writing electron voltage. It can be shown theoretically that the use of a suitably restricted bandwidth and optimized amplifier conditions should enable single photoelectrons to be detected. Tests on experimental tubes have shown that prescanning gains of 500 should be practicable. In this case the tube should be capable of detecting 40 incident photons per cathode image point per frame.

Print ISSN

0361-4573

Published

1961-07

Content type

Original Research

DOI

10.5594/J14351