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 a0 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.
Highlights
Modern high intensity laser technology has made the regime of relativistic optics experimentally accessible
In this work we show that the transition from the relativistic self-induced transparency (RSIT) to the holeattribution to the boring (HB) regime is associated with a much richer dynamical behavior than previously reported, owing to the complex interplay of fast electron generation and ion motion
Before concluding on this work, we wish to briefly stress that various ion acceleration mechanisms have been identified in near-critical plasmas, which are clearly different from the ion acceleration process in the dynamic transition regime discussed here
Summary
Any further distribution of this work must maintain interaction of a circularly-polarized laser-pulse with an overdense plasma and their relation to holeattribution to the boring (HB) and ion acceleration. It is demonstrated using particle-in-cell simulations and an analysis author(s) and the title of the work, journal citation of separatrices in single-electron phase-space, that ion motion can suppress fast electron escape to the and DOI. We report a new regime in which a transition from relativistic transparency to HB occurs dynamically during the course of the interaction. For a fixed laser intensity, this dynamic transition regime allows optimal ion acceleration in terms of both energy and energy spread
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