Experimental observation of parametric instabilities at laser intensities relevant for shock ignition

¹ Intense Laser Irradiation Laboratory, INO CNR (National Council of Research) - Pisa, Italy
² Université de Bordeaux, CNRS, CEA, CELIA (Centre Lasers Intenses et Applications) - Talence, France
³ Dipartimento SBAI, Università di Roma “La Sapienza” - Rome, Italy
⁴ National Research Nuclear University MEPhI, Department of Plasma Physics - Moscow, Russia
⁵ Empa Swiss Federal Laboratories for Materials Science and Technology - Dübendorf, Switzerland
⁶ Prague Asterix Laser System - Prague, Czech Republic
⁷ Institute of Physics & ELI Beamlines, ASCR - Prague, Czech Republic
⁸ Vinca Institute of Nuclear Sciences - Belgrade, Serbia

Received: 11 January 2017
Accepted: 15 March 2017

Abstract

We report measurements of parametric instabilities and hot electron generation in a laser intensity regime up to 6 × 10¹⁵ W/cm², typical of the shock ignition approach to inertial fusion. Experiments performed at the PALS laboratory in Prague show that the incident laser energy losses are dominated by Stimulated Brillouin Scattering (SBS) rather than by Stimulated Raman Scattering (SRS) or Two-Plasmon Decay (TPD). Results are compared to hydrodynamics simulations using a code that includes self-consistent calculations of non-linear laser plasma interactions and accounts for the laser intensity statistics contained in the beam speckles. Good agreement is found for the backscattered SRS light, and for temperature and flux of hot electrons. The effect of high-intensity speckles on backscattered SRS is also underlined numerically and experimentally.