The photography of cathode-ray-tube traces

The investigations described in this paper were undertaken to meet u number of isolated requests from the Services for information on photographic oscillography. Although the circumstances were not favourable for a planned investigation, information was obtained of the properties of luminescent materials for use as c.r.t. screens for photographic cathode-ray oscillograph tubes, and parts of the problem of the photography of c.r.t. traces was studied. Blue zinc-sulphide screens were found to be the best for general photographic work, and to have about the same ¿speed¿ to fast panchromatic, orthochromatic, or non-colour-sensitized photographic materials. Light from this screen is about six times as actinic as white light with a panchromatic emulsion, and about twelve times as actinic with an orthochromatic emulsion. Green willemite screens approach the actinic value of the blue zinc sulphide when used at very low anode voltages (less than 1 000 volts) in conjunction with a fully green-sensitized emulsion. At higher voltages, however, the blue screen is greatly superior. The recording of fast transients was studied, and the results tabulated in the form of an exposure table. Writing speeds above 2 000 km/sec can be recorded under suitable conditions. The effect of the electrical arrangements of the cathode-ray tube was also studied, and some special photographic techniques have been investigated. It was found that, for general photographic oscillography, little is to be gained by the use of special emulsions, as the standard range of photographic recording materials is adequate for most purposes. Similarly, little improvement over standard screens can be achieved by special phosphors and screening methods. Only in extreme cases is a combination of a special screen and emulsion justified.