Speaker
Stefan Weber
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.2005.pdf
Kinetic Simulations of Parametric Instabilities and Hot Electrons
Production in the Context of the Shock Ignition
Y. J. Gu1, 2, O. Klimo1, 4, Ph. Nicolai3, V. T. Tikhonchuk1, 3, S. Weber1
1) Institute of Physics of ASCR, ELI-Beamlines, Na Slovance 2, Prague, Czech Republic
E-mail: stefan.weber@eli-beams.eu
2) Institute of Plasma Physics of the CAS, Za Slovankou 1782/3, Prague, Czech Republic
3) University of Bordeaux, CNRS, CEA, CELIA, Talence, France
4) Czech Technical University in Prague, FNSPE, Prague, Czech Republic
The shock ignition (SI) scheme in laser-driven Inertial Confinement Fusion (ICF) is attractive
since it allows significant reduction of the driving energy requirements and improved
hydrodynamic stability. It is achieved with a strong shock which is launched at the end of
implosion phase by abruptly raising the laser intensity by one or two orders of magnitude.
However, laser–plasma interactions at this stage are strongly nonlinear and the physics of laser
spike absorption is important, while it is still one of the major unknowns in the shock-ignition
scenario.
Recent experiments at Prague Asterix Laser System (PALS) conducted under the conditions
compatible with SI and at wavelength of 1.315 µm have shown that a large portion of laser energy
can be reflected by Stimulated Raman Scattering (SRS) with a relatively small number of
generated hot electrons. A big difference in the absorption process and hot electron generation is
not well understood. Simulations of the laser-plasma interaction for the conditions of this
experiment are necessary.
In this work, we demonstrate the kinetic simulations of laser interacting with the plasma corona.
The Particle-in-cell (PIC) simulations are based on the relativistic electromagnetic code EPOCH.
The initial conditions are obtained from the hydrodynamics simulations. A large fraction of laser
energy is transferred into hot electrons with temperature higher than hundreds keV and strong SRS
accompanied with cavitation at quarter critical density and density profile modification
(steepening around critical density). It is observed that the SRS becomes stronger and shifts to the
less dense plasma in front of the quarter critical density region. The temperature of hot electrons
oscillates due to the competition between different instabilities. A broad SRS spectrum is observed
with many fractional harmonics which is a signature of strong secondary parametric instabilities.
The processes of laser beam filamentation and two-plasmon decay are also discussed.
This work has been carried out within the framework of the EUROfusion Consortium and has
received funding from the Euratom research and training programme 2014-2018 under grant
agreement No 633053. The views and opinions expressed herein do not necessarily reflect those
of the European Commission.
