Nonlinear dynamics of plasmas under intense electromagnetic radiation.

摘要

Under intense high-frequency radiation, a charged particle undergoes fast oscillations superimposed on the average drift motion. If the particle drift displacement on the period of these oscillations is small compared to the scale of the field, the average effect of the ac drive can often be approximated with an effective "ponderomotive" potential. The average ponderomotive (Miller) force is well known and underlies many nonlinear plasma phenomena. However, we show that interesting and very new effects come into play, particularly in regimes when the approximation of a conservative Miller force is violated.; The thesis is devoted to deriving rigorously the principles of generalized ponderomotive forces, discovering unusual particle behavior in intense fields, and identifying novel applications.; Three major topics are studied. The first part of the thesis contemplates new methods of selective manipulations with plasma constituents by means of intense electromagnetic radiation resonant to particle natural oscillations, particularly Larmor rotation in a dc magnetic field. An analytical model of particle nonadiabatic dynamics under resonant drive is proposed. We develop a theory of the "Maxwell demon effect", which occurs when an ac field acts on particles selectively, by reflecting or transmitting them depending on the direction of the particle average motion. New methods of producing one-way radio-frequency walls are predicted. The second part of the thesis is devoted to particle interaction with relativistically intense laser radiation. A new Lagrangian formalism for average relativistic dynamics of particles is developed; we explain how GeV electrons can be produced by focused radiation of currently available laser sources. In the third part, two applications of stimulated Raman backscattering (SRBS) in plasmas are studied: a method of producing ultra-intense short laser pulses by SRBS is suggested, and a new holography technique is proposed, which allows recording and retrieving of optical information by SRBS in Raman media.; Although the emphasis here is on analytical rigor and numerical simulation, this work is carried out with a view toward proposing specific experiments and toward identifying and developing practical applications.