title: Electron kinetic effects on Raman backscatter in plasmas.
abstract: We augment the usual three-wave cold-fluid equations governing Raman backscatter (RBS) with a new kinetic thermal correction, proportional to an average of particle kinetic energy weighted by the ponderomotive phase. From closed-form analysis within a homogeneous kinetic three-wave model and ponderomotively averaged kinetic simulations in a more realistic pulsed case, the magnitude of these new contributions is shown to be a measure of the dynamical detuning between the pump laser, seed laser, and Langmuir wave. Saturation of RBS is analyzed, and the role of trapped particles illuminated. Simple estimates show that a small fraction of trapped particles (approximately 6%) can significantly suppress backscatter. We discuss the best operating regime of the Raman plasma amplifier to reduce these deleterious kinetic effects.
authors.affiliation: Center for Advanced Accelerators, KERI, Changwon, Kyongnam 641-120, Korea.
authors.forename: M S
authors.initials: MS
authors.lastname: Hur
authors.forename: R R
authors.initials: RR
authors.lastname: Lindberg
authors.forename: A E
authors.initials: AE
authors.lastname: Charman
authors.forename: J S
authors.initials: JS
authors.lastname: Wurtele
authors.forename: H
authors.initials: H
authors.lastname: Suk