Relativistic and ponderomotive selffocusing of a laser beam in a radially inhomogeneous plasma. I. Paraxial approximation
Abstract
The propagation of a highirradiance laser beam in a plasma whose optical index depends nonlinearly on the light intensity is investigated through both theoretical and numerical analyses. The nonlinear effects examined herein are the relativistic decrease of the plasma frequency and the ponderomotive expelling of the electrons. This paper is devoted to focusing and defocusing effects of a beam assumed to remain cylindrical and for a plasma supposed homogeneous along the propagation direction but radially inhomogeneous with a parabolic density profile. A twoparameter perturbation expansion is used; these two parameters, assumed small with respect to unity, are the ratio of the laser wavelength to the radial electricfield gradient length and the ratio of the plasma frequency to the laser frequency. The laser field is described in the context of a time envelope and spatial paraxial approximations. An analytical expression is provided for the critical beam power beyond which selffocusing appears; it depends strongly on the plasma inhomogeneity and suggests the plasma density tailoring in order to lower this critical power. The beam energy radius evolution is obtained as a function of the propagation distance by numerically solving the paraxial equation given by the twoparameter expansion. The relativistic mass variation ismore »
 Authors:

 Service des Photons, Atomes et Molecules, Centre d' Etudes de Saclay, Bat. 522, 91191 GifsurYvette Cedex (France)
 Laboratoire PMI, Ecole Polytechnique, 91128 Palaiseau (France)
 Commissariat a l'Energie Atomique, Centre d'Etudes de LimeilValenton, 94195 VilleneuveStGeorges (France)
 Publication Date:
 OSTI Identifier:
 6212912
 Resource Type:
 Journal Article
 Journal Name:
 Physics of Fluids B; (United States)
 Additional Journal Information:
 Journal Volume: 5:10; Journal ID: ISSN 08998221
 Country of Publication:
 United States
 Language:
 English
 Subject:
 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; INHOMOGENEOUS PLASMA; LASER RADIATION; PONDEROMOTIVE FORCE; ANALYTICAL SOLUTION; BEAMPLASMA SYSTEMS; COMPUTER CODES; ELECTRIC FIELDS; PERTURBATION THEORY; PLASMA DENSITY; RELATIVISTIC PLASMA; ELECTROMAGNETIC RADIATION; PLASMA; RADIATIONS; 700350*  Plasma Production, Heating, Current Drive, & Interactions (1992)
Citation Formats
Brandi, H S, Manus, C, Mainfray, G, Lehner, T, and Bonnaud, G. Relativistic and ponderomotive selffocusing of a laser beam in a radially inhomogeneous plasma. I. Paraxial approximation. United States: N. p., 1993.
Web. doi:10.1063/1.860828.
Brandi, H S, Manus, C, Mainfray, G, Lehner, T, & Bonnaud, G. Relativistic and ponderomotive selffocusing of a laser beam in a radially inhomogeneous plasma. I. Paraxial approximation. United States. https://doi.org/10.1063/1.860828
Brandi, H S, Manus, C, Mainfray, G, Lehner, T, and Bonnaud, G. Fri .
"Relativistic and ponderomotive selffocusing of a laser beam in a radially inhomogeneous plasma. I. Paraxial approximation". United States. https://doi.org/10.1063/1.860828.
@article{osti_6212912,
title = {Relativistic and ponderomotive selffocusing of a laser beam in a radially inhomogeneous plasma. I. Paraxial approximation},
author = {Brandi, H S and Manus, C and Mainfray, G and Lehner, T and Bonnaud, G},
abstractNote = {The propagation of a highirradiance laser beam in a plasma whose optical index depends nonlinearly on the light intensity is investigated through both theoretical and numerical analyses. The nonlinear effects examined herein are the relativistic decrease of the plasma frequency and the ponderomotive expelling of the electrons. This paper is devoted to focusing and defocusing effects of a beam assumed to remain cylindrical and for a plasma supposed homogeneous along the propagation direction but radially inhomogeneous with a parabolic density profile. A twoparameter perturbation expansion is used; these two parameters, assumed small with respect to unity, are the ratio of the laser wavelength to the radial electricfield gradient length and the ratio of the plasma frequency to the laser frequency. The laser field is described in the context of a time envelope and spatial paraxial approximations. An analytical expression is provided for the critical beam power beyond which selffocusing appears; it depends strongly on the plasma inhomogeneity and suggests the plasma density tailoring in order to lower this critical power. The beam energy radius evolution is obtained as a function of the propagation distance by numerically solving the paraxial equation given by the twoparameter expansion. The relativistic mass variation is shown to dominate the ponderomotive effect. For strong laser fields, selffocusing saturates due to corrections of fourth order in the electric field involved by both contributions.},
doi = {10.1063/1.860828},
url = {https://www.osti.gov/biblio/6212912},
journal = {Physics of Fluids B; (United States)},
issn = {08998221},
number = ,
volume = 5:10,
place = {United States},
year = {1993},
month = {10}
}