Kinetic and finite ion mass effects on the transition to relativistic self-induced transparency in laser-driven ion acceleration. (22nd December 2017)

• Record Type: Journal Article
• Authors: Siminos, E; Grech, M; Wettervik, B Svedung; Fülöp, T
• Is Part Of: New journal of physics. Volume 19:Number 12(2017:Dec.)
• Publication Date: 2017-12-22
• Subjects: laser plasma interaction -- relativistic transparency -- hole-boring -- near critical plasmas -- Hamiltonian -- separatrices; 52.20.Dq -- 52.35.Mw -- 52.38.-r; Physics -- Periodicals; Physics; Periodicals; 530.05
• DOI: 10.1088/1367-2630/aa8e66
• Languages: English
• ISSNs: 1367-2630

Abstract

Abstract: We study kinetic effects responsible for the transition to relativistic self-induced transparency in the interaction of a circularly-polarized laser-pulse with an overdense plasma and their relation to hole-boring (HB) and ion acceleration. It is demonstrated using particle-in-cell simulations and an analysis of separatrices in single-electron phase-space, that ion motion can suppress fast electron escape to the vacuum, which would otherwise lead to transition to the relativistic transparency regime. A simple analytical estimate shows that for large laser pulse amplitude a 0 the time scale over which ion motion becomes important is much shorter than usually anticipated. As a result of enhanced ion mobility, the threshold density above which HB occurs decreases with the charge-to-mass ratio. Moreover, the transition threshold is seen to depend on the laser temporal profile, due to the effect that the latter has on electron heating. Finally, we report a new regime in which a transition from relativistic transparency to HB occurs dynamically during the course of the interaction. It is shown that, for a fixed laser intensity, this dynamic transition regime allows optimal ion acceleration in terms of both energy and energy spread.