Kinetic and finite ion mass effects on the transition to relativistic self-induced transparency in laser-driven ion acceleration
Journal article, 2017

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 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.

separatrices

hole-boring

relativistic transparency

laser plasma interaction

Hamiltonian

near critical plasmas

Author

Evangelos Siminos

Chalmers, Physics, Subatomic and Plasma Physics

M Grech

The French Alternative Energies and Atomic Energy Commission (CEA)

Benjamin Svedung Wettervik

Chalmers, Physics, Subatomic and Plasma Physics

Tünde Fülöp

Chalmers, Physics, Subatomic and Plasma Physics

New Journal of Physics

1367-2630 (ISSN)

Vol. 19 12 123042- 123042

Roots

Basic sciences

Subject Categories

Fusion, Plasma and Space Physics

DOI

10.1088/1367-2630/aa8e66