Photographic Study Of Rapid Events By Picosecond Techniques

Abstract

Former studies of high-speed events, e.g. sparkformation and laser produced plasmas by nanosecond light pulses revealed the necessity of shorter exposure times. - This can be done by aid of picosecond light pulses - either a single one or a train of pulses - generated in the cavity of a mode-locked neodymium or a ruby laser. - Schlierenphotos of laser triggered open-air sparks taken by multiple exposure with a series of pulses from a neodymium laser show the advantages of these techniques compared to one dimensional streak photographs. As another example, photos of a plasma induced by a series of ps-light-pulses on a metal surface are shown. - The application of single-pulse techniques is demonstrated by the study of a laser spark, induced by one or two ps pulses in air. In order to get sufficient power for breakdown, the single pulse extracted fro the mode-locked laser passes a two-stage ruby amplifier. - After focalisation, the main part of the pulse energy produces the break-down. The remaining part of the pulse passes a variable optical delay system, and serves as a light source for a schlieren system. In this way, single-shot schlierenphotos of laser sparks with life-times less than one nanosecond are obtained. For the study of later stages in spark development multiple exposure by a train of pulses is used. The above mentioned experimental arrangements are discussed in detail, the measurement of pulse duration by TPF and image converter is described, and some results about the plasma-behaviour are presented.© (1977) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.