Submicrosecond Flash Sources

Design details are given for two submicrosecond flash sources for photography by reflected light, silhouette and schlieren techniques. The source for reflected-light photography uses a “guided” air spark operated at 18 kv with 0.05 μf to produce a 0.4-μsec flash with a peak light of 5 million candlepower. The flashtube, a special design, is described, together with its power supply and trigger circuit. The trigger circuit can be operated by a microphone, phototube, contactor or other electrical signal, and incorporates an adjustable time delay. A photograph taken with the unit is shown. — A small spark source capable of producing flashes of about 10 mμsec duration for silhouette and schlieren photography is described. Relative peak light output and flash duration are given as a function of pressure for air, nitrogen, oxygen, carbon dioxide, hydrogen and argon. Gap resistance is given as a function of gap length, for air.