Two-dimensional growth of laser-driven waves in a hydrogen free jet

Abstract
A Q‐switched ruby laser has been used to irradiate a free jet of hydrogen. The propagation of the luminous wave which originated in the breakdown spark has been monitored using an optical system which permitted simultaneous observation of the motion along and perpendicular to the coincident axes of the focused laser beam and the free jet. Correlation of the luminous frontal wave and the late‐time shock wave (made visible with a schlieren system) with the third root of the ratio of laser power to free‐jet plenum pressure was found to hold over a range of several orders of magnitude.