Speaker
Gabriele Cristoforetti
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/I1.204.pdf
I1.204
for shock ignition at PALS
G. Cristoforetti1, L. Antonelli2, S. Atzeni3, F. Baffigi1, F. Barbato4, D. Batani5, G.
Boutoux5, A. Colaitis5, F. D’Amato1, J. Dostal6,7, R. Dudzak7,6, L. Juha7,6, P. Koester1, M.
Krus6, D. Mancelli5,9, O. Renner7,6, J. J. Santos5, M.M. Skoric10, S. Viciani1, L.A. Gizzi1
1 National Institute of Optics, CNR, Pisa and Florence, Italy
2 York Plasma Institute, department of Physics, University of York, UK
3 Dipartimento SBAI, Università di Roma “La Sapienza”, Roma, Italy
4 Empa Swiss Federal Laboratories for Materials Science and Technology, 8600
Dübendorf, Switzerland
5 Université Bordeaux, CNRS, CEA, CELIA, UMR 5107, Talence, France
6 Institute of Plasma Physics, Czech Academy of Sciences, Prague 8, Czech Republic
7 Institute of Physics, Czech Academy of Sciences, Prague 8, Czech Republic
8 INFN, Laboratori Nazionali di Frascati, Frascati (Roma) Italy
9 Donostia International Physics Center (DIPC), 20018 Donostia/San Sebastian,
Basque Country, Spain
10 National Institutes of Natural Sciences, Tokyo, Japan
A major issue in the Shock Ignition scheme for Inertial Confinement Fusion (ICF) is the
relevance of parametric instabilities (LPI), as
Stimulated Brillouin Scattering (SBS), Stimulated
Raman Scattering (SRS) and Two Plasmon Decay
(TPD), and the role of generated hot electrons. Here
we present the main results of several campaigns
at the PALS facility, where parametric instabilities
at laser intensities (0.2-2)x1016 W/cm2 at 1 and
3 irradiation (438 and 1314 nm, 250 ps) have
been investigated in planar geometry. Such an
intensity settles the interaction in a regime relevant
for Shock Ignition. Time-resolved
spectroscopy and calorimetry of scattered light
and characterization of hot electrons via K and
bremsstrahlung emission spectroscopy allowed a
detailed description of LPI and hot electron
generation. Experimental data show that the energy
transfer is limited by laser light Top: Time-resolved SRS spectrum from
3 irradiation. Below: SRS spectrum
reflection and SBS rather than by SRS in all the from 1 irradiation.
irradiation conditions. As expected, Backward Raman Scattering grows by 1-2 orders
of magnitude passing from 3 to 1 irradiation and the region where it is driven moves
toward higher density plasma, due to the higher plasma temperature obtained at 1
irradiation. Hot electron temperature (30-40 keV) and flux are compatible with a
predominant generation via SRS rather than via TPD, despite the data suggest the presence
of a component of high energy hot electrons (Thot>100 keV), which could be possibly
generated by TPD or hybrid TPD/SRS. SRS reflectivity exhibits spikes both in the spectral
and temporal domains, suggesting that the process is dominated by kinetic effects. Results
are compared to hydrodynamic 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. Fully kinetic simulations of laser plasma
interaction at different times of irradiation are also in progress.
