Penetration enhancement transmission electron

Despite these rapid developments, transmission electron microscopy could not possibly contribute significantly to coatings and polymer research until commercial machines became available. The first Siemens microscope was marketed in 1938 (35). followed the next year by a more advanced unit. In this country, RCA marketed its first unit in 1941 (36). Even with commercial equipment available, many other problems had to be overcome. The main difficulty was that of sample preparation. Sections had to be extremely thin to be penetrated sufficiently by the electron beam. Often contrast was not sufficient to form a suitable image. In 1939, the shadowing technique was developed to enhance contrast... 

Photocathodes may be used in two configurations, opaque (or reflection) photocathodes and transmission photocathodes. Detailed calculations of the performance of both types of photocathode may be found in the articles of Henke (43-45). Opaque photocathodes usually are deposited directly onto the input face of the MCP such that the photocathode material penetrates a short distance into the channels. Thus incident radiation which enters the channels strikes the photocathode material, resulting in enhanced detection efficiency. As in the case of a bare MCP, radiation striking the interchannel web is not normally detected, so electron deflection grids in front of the MCP are sometimes used to further the enhancement of detection efficiency. 

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