Nonstationary ponderomotive self-focusing of a Gaussian laser pulse in a plasma

Journal Article · Mon Nov 15 04:00:00 EST 2010 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.3518759· OSTI ID:21532017

Tripathi, Deepak; Uma, R ^[1]; Bhasin, Lalita; Tripathi, V K ^[2]

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1. Center for Energy Studies, Indian Institute of Technology Delhi, New Delhi 110016 (India)
2. Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016 (India)

A model of relaxing ponderomotive nonlinearity is developed to study the nonstationary self-focusing of a Gaussian laser pulse in a plasma. The ponderomotive force acts on the electrons instantaneously but the plasma density redistribution via the process of ambipolar diffusion is taken to evolve on the time scale {tau}{sub R} congruent with r{sub 0}/c{sub s}, where r{sub 0} is the laser spot size and c{sub s} is the sound speed. The paraxial ray approximation is used to solve the wave equation. The focusing is stronger at the rear of the pulse than at the front, causing considerable distortion of the pulse when pulse duration is comparable to nonlinearity relaxation time. The saturation effect of nonlinearity leads to focusing of any portion of the pulse to a minimum spot size r{sub 0}f{sub min} at an optimum distance z{sub op} and then the spot size increases. f{sub min} and z{sub op} depend on the intensity of the portion of the pulse.

• OSTI ID: 21532017
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 11 Vol. 17; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
AMBIPOLAR DIFFUSION
APPROXIMATIONS
CALCULATION METHODS
DIFFERENTIAL EQUATIONS
DIFFUSION
EQUATIONS
FOCUSING
LASERS
NONLINEAR PROBLEMS
PARTIAL DIFFERENTIAL EQUATIONS
PLASMA
PLASMA DENSITY
PONDEROMOTIVE FORCE
PULSES
RELAXATION TIME
WAVE EQUATIONS