Principle of high accuracy for the nonlinear theory of the acceleration of electrons in a vacuum by lasers at relativistic intensities

Abstract

Acceleration of electrons by lasers in a vacuum was considered impossible based on the fact that plane-wave and phase symmetric wave packets cannot transfer energy to electrons apart from Thomson or Compton scattering or the Kapitza–Dirac effect. The nonlinear nature of the electrodynamic forces of the fields to the electrons, expressed as nonlinear forces including ponderomotion or the Lorentz force, permits an energy transfer if the conditions of plane waves in favor of the beams and/or the phase symmetry are broken. The resulting electron acceleration by lasers in a vacuum is now well understood as “free wave acceleration”, as “ponderomotive scattering”, as “violent acceleration”, or as “vacuum beat wave acceleration”. The basic understanding of these phenomena relates to an accuracy principle of nonlinearity for explaining numerous discrepancies on the way to the mentioned achievement of “vacuum laser acceleration”, which goes beyond the well-known experience of necessary accuracy in both modeling and experimental work experiences among theorists and experimentalists in the field of nonlinearity. From mathematically designed beam conditions, an absolute maximum of electron energy per laser interaction has been established. It is shown here how numerical results strongly (both essentially and gradually) depend on the accuracy of the used laser fields for which examples are presented and finally tested by the criterion of the absolute maximum.

Direct Electron Acceleration with Radially Polarized Laser Beams

“…Despite the controversy that has surrounded the experimental observation of ponderomotive electron acceleration in Gaussian laser beams [50][51][52][53], the mechanism by which the particles acquire a significant (relativistic) momentum is now well understood and accepted [54]. The relativistic generalization of the original PF model [45][46][47][48][49] helped to explain and understand experimental observations in terms of relativistic ponderomotive scattering (RPS), where particles are expelled out of the beam focus within only a few laser cycles [55,56].…”

“…Third and finally, the longitudinal electric field component takes over and provides a final extra push. Although the amplitude of the longitudinal component is usually tiny (∝ E 0 λ 0 /w 0 ), including it into calculations changes the result from vanishingly small to considerable acceleration [54,55,57]. This can be explained by the fact that an electron moving longitudinally can possibly stay in phase with the longitudinal electric field over longer distances.…”

High Brightness Laser Induced Multi-Mev Electron/Proton Sources

“…In fact, thanks to CPA, pulses of a few joules in tens of femtoseconds can now be produced and used to induce the judge electric fields that can accelerate charged particles up to lGeV in a few mm length. In the last years theoretical and experimental activity has been developed achieving more and more encouraging results concerning the energy and the quality of the electron/proton beam produced by laser-driven acceleration mechanisms [3,4,5,6,7,8,9,10,11,12,13,14].…”

Comment on “Electron acceleration by a short laser beam in the presence of a long-wavelength electromagnetic wave” [J. Appl. Phys. 102, 056106 (2007)]

“…Before this, many schemes had been proposed for acceleration of charged particles in double-frequency laser fields. [2][3][4][5][6] The model given in Ref. 1 is simple and clear, but its calculation parameters are not presented clearly.…”