Analysis and simulation of Raman backscatter in underdense plasmas
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)
- Department of Physics, University of California, Berkeley, Berkeley , California 94270 (United States)
A new formalism to describe the spatiotemporal evolution of relativistic Raman backscatter (RBS) of ultrashort laser pulses in underdense plasma has been developed. This theory is based on an eikonal representation for the RBS field and averaging over the oscillation frequency. Equations are derived for the evolution of the RBS radiation field amplitude and phase and for particle motion in the ponderomotive potential of the pump and RBS fields. A technique similar to that used in Raman free electron lasers is used to include the plasma density oscillation and its electric field in the particle equations. The equations have been solved numerically in a code that provides an accurate description of the nonlinear electron motion on a short spatial scale of half the radiation wavelength, while at the same time evolving the laser field on a much coarser scale, characteristic of the growth rate of the instability. Two-dimensional nonlinear effects, such as the return current, are analytically estimated and phenomenologically incorporated in the numerical code. The results of recent (RBS) experiments are compared with the analytical and numerical predictions of the theory. A statistical theory of the linear RBS instability growing from plasma noise is developed. It is found that in the nonlinear regime backscattered radiation, seeded by random density fluctuations in the plasma, breaks up into spikes, which exhibit superradiant behavior. These effects might explain the spikiness of the RBS spectra in the nonlinear regime. {copyright} {ital 1997 American Institute of Physics.}
- OSTI ID:
- 560641
- Report Number(s):
- CONF-961102-; ISSN 1070-664X; TRN: 98:000736
- Journal Information:
- Physics of Plasmas, Vol. 4, Issue 5; Conference: Meeting of the Division of Plasma Physics of the American Physical Society, Denver, CO (United States), 11-15 Nov 1996; Other Information: PBD: May 1997
- Country of Publication:
- United States
- Language:
- English
Similar Records
Spectral anomalies in high intensity stimulated Raman backscattering in laser plasmas
Self-focusing of cosh-Gaussian laser beam and its effect on the excitation of ion-acoustic wave and stimulated Brillouin backscattering in collisionless plasma