PHOTO CATHODS (Ph.D Physics )
  Coatings:  Although a plain metallic cathode will exhibit photoelectric properties, the specialized coating greatly increases the effect. A photocathode usually consists of alkali metals with very low work function.The coating releases electrons much more readily than the underlying metal, allowing it to detect the low-energy photons in infrared radiation. The lens transmits the radiation from the object being viewed to a layer of coated glass. The photons strike the metal surface and transfer electrons to its rear side. The freed electrons are then collected to produce the final image.A new processing technology and the properties of multialkali antimonide photocathodes are described. The technique requires an initial antimony layer to be deposited on a fiber-optic window at a suitable temperature. After that, the layer is activated by multialkali and antimonide. Thus, the multialkali photocathodes named "The Modern Multialkali Photocathode" are obtained. It has been found that a photocathode thus processed gives a sensitivity of 200 to 300ÎÜA/lm for white light at a color temperature of 2854K. This paper shows the variation of photosensitivity during processing of a Modern Multialkali Photocathode and the variation of spectral sensitivity at different wavelengths. The author discusses the results, gives a supposition of "photoemission center", and discusses the role of Cs in multialkali photocathodes.