Simulations of wave–particle interactions in stimulated Raman forward scattering in a magnetized plasma

Abstract

Stimulated Raman forward scattering in a high-temperature, magnetized plasma is investigated with relativistic Vlasov–Maxwell simulations and with envelope and test particle calculations. The parameters correspond to Raman current drive by free-electron lasers in reactor grade tokamak plasmas. The phase velocity of the Raman excited plasma wave is large, and therefore the Landau damping is initially weak. The electron plasma wave grows to a large amplitude and accelerates electrons to high energies. Simultaneous pump depletion weakens the driving ponderomotive force, which leads to a collapse of the plasma wave if the number of the interacting electrons is large enough. Spatially the wave–particle interaction takes place in a distance of a few wavelengths of the plasma wave. The electron energies can largely exceed the kinetic energy at the phase velocity of the electron plasma wave. Short-wavelength amplitude modulations of the plasma wave appear at high amplitudes. Efficient generation of the nonresonant anti-Stokes wave and of the second Stokes wave are also observed. Analytical growth rates and envelope calculations explain well the early evolution of the Raman process. Later on, nonlinear wave–particle interactions and relativistic effects start to dominate, and the system is not satisfactorily described by simple envelope equations.

Effect of external magnetic field on wakefield generation in underdense plasma slab using backward semi-Lagrangian Vlasov code

“…where Ω c ¼ σω cx . The above mentioned equations have already been presented for beat wave current drive [57] and raman forward scattering [58] in magnetized plasma. In the absence of external magnetic field Ω c ¼ 0, Eq.…”

Long-time discrete particle effects versus kinetic theory in the self-consistent single-wave model

“…This simplified model, supposing only a harmonic oscillation for |V |, shows that the amplitude of the wave oscillations depends directly on the occurrence of (x, p)-space inhomogeneities. Actually, for a homogeneous phase space, (17) implies that ∆V scales at most as N −1/2 and vanishes in the kinetic limit. However, consider now the case where α − θ is the barycentric position, in the reference frame of the wave, of an inhomogeneity (clump) composed of a finite fraction |M | of the particles.…”

“…The function f (interpolated by cubic splines) is transported along the characteristic lines of the kinetic equation, i.e. along trajectories of the original particles [17]. Therefore, in addition to the truly physical effects of the discrepancies between finite N and kinetic systems on long time simulations, we shall also compare in this article computational finite grid effects of the kinetic solver with the granular aspects of the Nparticle system [18].…”

A hybrid Eulerian Vlasov code. I. Study of high-frequency beatwave experiment and Manley–Rowe action evolution in a finite causal system

“…The details of the way in which the equations are advanced and the boundary conditions are imposed have been extensively described elsewhere. 7,8 B. The Hilbert-Vlasov code…”