Laser Interaction in Long-Scalelength Plasmas.
Abstract
Absorption of a short-pulse, high-intensity Nd-laser beam (vacuum irradiance of 10 to the 14th power to 10 to the 15th power W/sq cm) by preformed plasmas of different density scalelengths is investigated. Increased effects of plasma instabilities are found at longer scalelengths. The amount of backscattered light increases with plasma scalelength and limits the absorption fraction at the longest scalelength. The onset of suprathermal electron production, deduced from observations of energetic (20 to 50 keV) x rays, occurs at lower laser irrradiance for longer scalelength plasmas. A correlation between energetic x rays and 3 omega sub 0/2 emission suggests that the suprathermal electrons are produced by a plasma instability at quarter-critical density. At higher intensities there is evidence for severe perturbations of the preformed plasma and for self-focusing of the incident beam. Keywords: Long scalelength; Laser plasma interaction; Stimulated brillouin backscatter; Laser absorption.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 31, 1985
- Accession Number
- ADA163604
Entities
People
- F. C. Herbst
- John A. Stamper
- John H. Gardner
- M. J. Young
- Stephen P.P. Obenschain
Organizations
- United States Naval Research Laboratory