The recording of optical transients

Four methods of recording the transient optical phenomena associated with the spark breakdown of gases are described in the paper. The duration of such transients may vary between the limits 10¿3 sec down to 10¿8 sec. The consequent problems, limitations and characteristics of the methods are discussed, so that their application to the recording of similar optical phenomena may be appreciated. The first two methods of recording are direct photographic techniques which make use of the Kerr cell and the rotating-mirror camera respectively. The third method described is an indirect one, in which a photo-multiplier tube is used to convert the optical transient to an electrical one; the latter is then displayed on the screen of a high-speed oscillograph and photographed. This method makes use of a sealed off cathode-ray tube which has a 9-cm screen and is operated from a 10-kV supply. The design of the oscillograph and the associated photo-multiplier and amplifier circuits are described and oscillograms are included to illustrate the performance of the equipment. In the latter part of the paper, a recording technique is considered, which is based on the application of television techniques to this work. The principles of the method, which makes use of an iconoscope type of tube, are stated.