Relativistic and ponderomotive self-focusing of a laser beam in a radially inhomogeneous plasma. II. Beyond the paraxial approximation

Journal Article · Fri Apr 01 04:00:00 EST 1994 · Physics of Plasmas; (United States)

DOI:https://doi.org/10.1063/1.870756· OSTI ID:6685366

Bonnaud, G ^[1]; Brandi, H S; Manus, C; Mainfray, G ^[2]; Lehner, T ^[3]

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1. Commissariat a l'Energie Atomique, Centre d'Etudes de Limeil-Valenton, 94195 Villeneuve-St.-Georges (France)
2. Service des Photons, Atomes et Molecules, Centre d'Etudes de Saclay, Bat. 522, 91191 Gif-sur-Yvette Cedex (France)
3. Laboratoire PMI, Ecole Polytechnique, 91128 Palaiseau (France)

The propagation in a plasma of a high-intensity electromagnetic wave inducing both relativistic mass increase and ponderomotive expulsion of electrons is analyzed via two-dimensional simulations. The time/space evolution of the wave is modeled by an axisymmetric scalar wave equation in which the plasma frequency is an instantaneous and local function of the wave energy; the incident irradiance is assumed to be constant in time. The specific features of relativistic focusing are first discussed. The ponderomotive effect enforces the focusing process by expelling the plasma electrons, creating density bumps and sharp density gradient on the edge of the light beam; the nonlinear focusing is faster and stronger confirming the paraxial/Gaussian beam core analysis presented in Part I [Phys. Fluids B [bold 5], 3539 (1993)]. In contrast to Part I, the light is guided in a sharp-edged density channel. The influence of the radial density inhomogeneity is then examined by using both convex (basin shape) and concave (bump shape) profiles. The self-focusing threshold power is increased for concave profiles. For convex profiles, the natural refraction helps the self-focusing observation but weakens the light-guiding trend previously observed. Finally, new features characterizing wave self-focusing, such as self-steepening and light reflection, are shown.

• OSTI ID: 6685366
• Journal Information: Physics of Plasmas; (United States), Journal Name: Physics of Plasmas; (United States) Vol. 1:4; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700350* -- Plasma Production
Heating
Current Drive
& Interactions-- (1992-)
BEAM-PLASMA SYSTEMS
DIFFERENTIAL EQUATIONS
ELECTROMAGNETIC RADIATION
EQUATIONS
INHOMOGENEOUS PLASMA
LASER RADIATION
PARTIAL DIFFERENTIAL EQUATIONS
PLASMA
PLASMA SIMULATION
PONDEROMOTIVE FORCE
RADIATIONS
RELATIVISTIC PLASMA
SIMULATION
WAVE EQUATIONS