The Ultra-Relativistic Electron Acceleration By Langmuir Plasmons In Laser Plasma

Laser plasma interaction in the relativistic regime is crucial for laser plasma acceleration and for inertial confinement fusion(ICF) with the fast ignitor scheme. It is well known that the interaction of a high-intensity laser and plasma is very complicated. One of the results of the interaction, the electron acceleration in the laser-plasma, is particularly interesting for the following reasons: (â…°) in the "fast ignitor" of the inertial confinement fusion (ICF), the laser-accelerated electron plays an important role in transporting the energy through an overdense plasma to the fuel; (â…±) the flux of relativistic (high-energy) electrons can be applied to many fields, such as nuclear reactions, radiation physics and so on.Interestingly, the exponential form of the electron energy spectrum has been manifested in a number of experiments and in three-dimensional particle-in cell (3D-PIC) simulations of the interactions of high-intensity laser and matter. Concomitant to these experiments and simulations, the electronic acceleration has been demonstrated by some theories; for example, the forced laser wake field acceleration (FLWFA), beat wave acceleration (BWA), laser wake field acceleration(LWFA), direct laser acceleration(DLA), self-modulate laser wake field acceleration(SMLWFA) and so on. These theories have successfully explained why electrons can obtain enough energy, but they have failed to explain the exponential form of the electron spectra measured experimentally.The strong Langmuir turbulence plasmons can be easily excited through wave-wave interactions in the active region of the laser-plasma, which can accelerate electrons effectively. The turbulence acceleration of non-relativistic particles has been presented by Li X Q(2002). Here we discuss a new mechanism of the ultra-relativistic electron acceleration in a laser-plasma, namely, the turbulence acceleration by strong Langmuir plasmons. The theory of Langmuir turbulence acceleration(LTA) is not only similar to the Fermi acceleration in the principium, but more efficient than that of the Fermi acceleration. The energy spectrum of hotelectrons undergoing LTA can be studied in terms of a diffusion equation in energy- momentum space.In this paper, Considering the physical conditions close to the critical surface in a plasma, we obtain a coincident result with experiments based on the FokkerPlanck equation. Through the analysis, the LTA would be the dominant process, where ultra-relativistic electrons are generated by the interaction of the high-intensity laser and plasma.