Nonlinear electromagnetic plasma eigenmodes and their stability to stimulated Raman scattering

Journal Article · Tue Aug 15 04:00:00 EDT 2006 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2234647· OSTI ID:20860169

Pathak, Vishwa Bandhu; Tripathi, V K ^[1]

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1. Physics Department, Indian Institute of Technology, New Delhi-110016 (India)

Transverse mode structure of nonlinear laser eigenmodes in underdense and overdense plasmas has been obtained by numerically solving the wave equation under relativistic and ponderomotive nonlinearities. The mode structure closely resembles a Lorentzian with half width scaling inversely as the axial intensity of the laser. The threshold condition for laser penetration in an overdense plasma turns out to be {gamma}{sub 0}{identical_to}(1+a{sub 0}{sup 2}/2){sup 1/2}{>=}2n{sub 0}/n{sub cr}-1, where n{sub 0} is the equilibrium electron density, n{sub cr} is the critical density at laser frequency, and {gamma}{sub 0} is the electron Lorentz factor due to the laser of normalized axial intensity a{sub 0}{sup 2}. The nonlinear laser eigenmode, in a low density plasma, is unstable to stimulated Raman backscattering off a copropagating space charge reactive quasimode. The growth rate increases with laser intensity as a{sub 0} rises up to a{sub 0}{approx}1. Beyond this value, growth rate decreases with a{sub 0}, due to the enhancement of electron mass and depletion of electrons from the axial region. Geometrical effects also reduce the growth rate.

• OSTI ID: 20860169
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 8 Vol. 13; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BACKSCATTERING
ELECTRON DENSITY
ELECTRONS
LASERS
LIGHT TRANSMISSION
NONLINEAR PROBLEMS
NUMERICAL ANALYSIS
PLASMA DENSITY
PLASMA INSTABILITY
PONDEROMOTIVE FORCE
RAMAN EFFECT
RELATIVISTIC PLASMA
RELATIVISTIC RANGE
SPACE CHARGE
STABILITY
WAVE EQUATIONS