Plasma emission and radiation from ultra-relativistic Brunel electrons in femtosecond laser-plasma interactions

15th Latin American Workshop on Plasma Physics; 21st IAEA TM on Research Using Small Fusion Devices

Ondarza-Rovira, R.^1 ; Boyd, T.J.M.^2

Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, México, Distrito Federal

11801, Mexico^1

Centre for Theoretical Physics, University of Essex, Wivenhoe Park, Colchester

CO4 3SQ, United Kingdom^2

关键词: Femtosecond laser plasma;    High order harmonics;    Intense femtosecond laser pulse;    Normalized parameters;    Particle-in-cell simulations;    Similarity parameter;    Single-particle model;    Supercritical densities;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/591/1/012036/pdf
DOI  :  10.1088/1742-6596/591/1/012036

来源: IOP

【 摘 要 】

A highly intense femtosecond laser pulse incident on a plasma target of supercritical density, gives rise to reflected high-order harmonics of the laser frequency. The radiation model adopted here considers Brunel electrons -those reinjected into the plasma after performing a vacuum excursion- perturbed by a localized turbulent region of an electrostatic field that is generated during the interaction, and characterized by a soliton-like structure. The observed power spectrum is characterized by a power-law decay scaled as Pm∼ m-p, where m denotes the harmonic order. In this work an appeal is made to a radiation mechanism from a single particle model that shows harmonic power decays described -as previously reported from particle-in-cell simulations- within the range 2/3 ≤ p ≤ 5/3. Plasma emission is strongest for values of the similarity parameter S = ne/(nca0) in the range 1 ≤ S ≤ 5, and where neand ncare the ambient electron plasma density and the critical density, respectively, and a0is the normalized parameter of the electric field of the incident light. It was found that the radiation spectra obtained from the single particle model here presented is consistent with previously reported power-law 5/3 decays from particle-in-cell simulations.