Enhanced ion acceleration using the high-energy petawatt PETAL laser

The high-energy petawatt PETAL laser system was commissioned at CEA’s Laser M´egajoule facility during the 2017–2018 period.This paper reports in detail on the first experimental results obtained at PETAL on energetic particle and photon generation from solid foil targets,with special emphasis on proton acceleration.Despite a moderately relativistic(<1019 W/cm^(2))laser intensity,proton energies as high as 51 MeV have been measured significantly above those expected from preliminary numerical simulations using idealized interaction conditions.Multidimensional hydrodynamic and kinetic simulations,taking into account the actual laser parameters,show the importance of the energetic electron production in the extended low-density preplasma created by the laser pedestal.This hot-electron generation occurs through two main pathways:(i)stimulated backscattering of the incoming laser light,triggering stochastic electron heating in the resulting counterpropagating laser beams;(ii)laser filamentation,leading to local intensifications of the laser field and plasma channeling,both of which tend to boost the electron acceleration.Moreover,owing to the large(∼100μm)waist and picosecond duration of the PETAL beam,the hot electrons can sustain a high electrostatic field at the target rear side for an extended period,thus enabling efficient target normal sheath acceleration of the rear-side protons.The particle distributions predicted by our numerical simulations are consistent with the measurements.

Generation of high energy laser-driven electron and proton sources with the 200 TW system VEGA 2 at the Centro de Laseres Pulsados

The Centro de Laseres Pulsados in Salamanca,Spain has recently started operation phase and the first user access period on the 6 J 30 fs 200 TW system(VEGA 2)already started at the beginning of 2018.In this paper we report on two commissioning experiments recently performed on the VEGA 2 system in preparation for the user campaign.VEGA 2 system has been tested in different configurations depending on the focusing optics and targets used.One configuration(long focal length F=130 cm)is for underdense laser-matter interaction where VEGA 2 is focused onto a low density gas-jet generating electron beams(via laser wake field acceleration mechanism)with maximum energy up to 500 MeV and an X-ray betatron source with a 10 keV critical energy.A second configuration(short focal length F= 40 cm)is for overdense laser-matter interaction where VEGA 2 is focused onto a 5 μm thick Al target generating a proton beam with a maximum energy of 10 MeV and temperature of 2.5 MeV.In this paper we present preliminary experimental results.