Speaker
Evangelos Siminos
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.2038.pdf
Kinetic and finite ion mass effects on the transition to relativistic
self-induced transparency in laser-driven ion acceleration
E. Siminos1 , M. Grech2 , B. Svedung Wettervik3 , T. Fülöp3
1 Department of Physics, University of Gothenburg, Sweden
2 LULI, CNRS, UPMC, Ecole Polytechnique, CEA, 91128 Palaiseau, France
3 Department of Physics, Chalmers University of Technology, Gothenburg, Sweden
We study kinetic effects responsible for the transition to relativistic self-induced transparency
(RSIT) 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 8
HB IC)
and an analysis of separatrices in single-electron 7 s (P
1 + a02
ion
2
1/2
6 b . ∝ a0
r
phase-space, that ion motion can suppress fast elec-
o
imm
n SW
nc eff =
tron escape to the vacuum, which would otherwise 5
n0 /nc
lead to transition to the relativistic transparency 4
regime. A simple analytical estimate shows that 3 H
for large laser pulse amplitude a0 the time scale 2 RSIT He
over which ion motion becomes important is much 5 10 15 20 25
a0
shorter than usually anticipated. As a result, the
threshold density above which hole-boring occurs
Figure 1: Different transition thresholds be-
decreases with the charge-to-mass ratio. Moreover,
tween RSIT and HB: for infinite plane waves
the transition threshold is seen to depend on the
(black dashed line), cold-fluid threshold for
laser temporal profile, due to the effect that the latter existence of a standing wave [1] (red solid
has on electron heating. We report a new regime in line), PIC simulations with immobile ions [2]
which a transition from relativistic transparency to (green triangles), PIC simulations for hydro-
hole-boring occurs dynamically during the course gen and helium [3] (error bars). The dynamic
of the interaction. It is shown that, for a fixed laser transition regime lies within the error bars.
intensity, this dynamic transition regime allows op-
timal ion acceleration in terms of both energy and energy spread.
References
[1] F. Cattani et al, Phys. Rev. E 62, 1234 (2000)
[2] E. Siminos et al, Phys. Rev. E 86, 056404 (2012)
[3] E. Siminos et al, New J. Phys. 19, 123042 (2017)
