La technique de l’amplification à dérive de fréquence a donné accès à la production d’impulsions lumineuses ultra-courtes, quelques femtosecondes, et ultrapuissantes, plusieurs dizaines de pétawatts, ...ouvrant le champ à de nombreuses applications. Nous fournissons ici quelques informations historiques et présentons les fondements de la technique.
The Petawatt Aquitaine Laser (PETAL) facility was designed and constructed by the French Commissariat à l'énergie atomique et aux énergies alternatives (CEA) as an additional PW beamline to the Laser ...MegaJoule (LMJ) facility. PETAL energy is limited to 1 kJ at the beginning due to the damage threshold of the final optics. In this paper, we present the commissioning of the PW PETAL beamline. The first kJ shots in the amplifier section with a large spectrum front end, the alignment of the synthetic aperture compression stage and the initial demonstration of the 1.15 PW @ 850 J operations in the compression stage are detailed. Issues encountered relating to damage to optics are also addressed.
We present the experimental demonstration of a subaperture compression scheme achieved in the PETAL (PETawatt Aquitaine Laser) facility. We evidence that by dividing the beam into small subapertures ...fitting the available grating size, the sub-beam can be individually compressed below 1 ps, synchronized below 50 fs and then coherently added thanks to a segmented mirror.
The high-energy petawatt PETAL laser system was commissioned at CEA’s Laser Mégajoule 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/cm2) 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 (∼100 μm) 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.
Laser-driven neutron sources could offer a promising alternative to those based on conventional accelerator technologies in delivering compact beams of high brightness and short duration. We examine ...this through particle-in-cell and Monte Carlo simulations that model, respectively, the laser acceleration of protons from thin-foil targets and their subsequent conversion into neutrons in secondary lead targets. Laser parameters relevant to the 0.5 PW LMJ-PETAL and 0.6–6 PW Apollon systems are considered. Owing to its high intensity, the 20-fs-duration 0.6 PW Apollon laser is expected to accelerate protons up to above 100 MeV, thereby unlocking efficient neutron generation via spallation reactions. As a result, despite a 30-fold lower pulse energy than the LMJ-PETAL laser, the 0.6 PW Apollon laser should perform comparably well both in terms of neutron yield and flux. Notably, we predict that very compact neutron pulses, of ∼10 ps duration and ∼100 μm spot size, can be released provided the lead convertor target is thin enough (∼100 μm). These sources are characterized by extreme fluxes, of the order of 1023 n cm−2 s−1, and even ten times higher when using the 6 PW Apollon laser. Such values surpass those currently achievable at large-scale accelerator-based neutron sources (∼1016 n cm−2 s−1), or reported from previous laser experiments using low-Z converters (∼1018 n cm−2 s−1). By showing that such laser systems can produce neutron pulses significantly brighter than existing sources, our findings open a path toward attractive novel applications, such as flash neutron radiography and laboratory studies of heavy-ion nucleosynthesis.
Electromagnetic pulses (EMP) present a serious threat for operation of high-power, high-energy laser facilities. Here, we present an efficient strategy for EMP mitigation with a resistive and ...inductive holder, which is supported by extended numerical simulations and validated in dedicated experiments at the kilojoule/picosecond (kJ/ps) Petawatt Aquitaine Laser (PETAL) facility. Moreover, we demonstrate how a combination of PETAL with the tens of kJ/ns Laser MegaJoule (LMJ) beams may suppress the EMP emission. This method opens another efficient way for the EMP control on high-power, high-energy laser facilities.
In this paper we present a self-referenced interferometric single-shot measurement technique that we use to evaluate the longitudinal chromatism compensation made by a diffractive lens corrector. A ...diffractive lens with a delay of 1 ps is qualified for a 60 mm beam aperture. This corrector was implemented on the Alisé Nd:glass power chain. We qualify the corrector and the Alisé power chain chromatism, demonstrating the potential of this measuring principle as well as the interest of diffractive lenses to correct longitudinal chromatism of petawatt-class lasers.
The first experiments on the National Ignition Facility (NIF) in the US started and will be followed by the Laser MégaJoule (LMJ) in France. Such facilities will provide unique tools for inertial ...confinement fusion (ICF) physics & for basic science. A petawatt short pulse laser (ps) is being added to the ns pulse beams of the LMJ. This is PETAL (PETawatt Aquitaine Laser), under construction on the LMJ site near Bordeaux (France). The Petal+ project is aiming at the design and construction of diagnostics dedicated to experiments with PETAL and LMJ laser beams. Within Petal+, three types of diagnostics are under study: a proton spectrometer, an electron spectrometer and a large-band X-ray spectrometer. The first goal of these diagnostics will be to characterize the secondary radiation and particle sources produced with PETAL. They will also be used for experiments using both ns and ps beams. In the present paper emphasis is put on the charged-particle diagnostics.
The status of the PETAL project is presented in this paper. The global architecture and performances of this facility are detailed with the first experimental results obtained on the LIL facility, ...and with the main steps which will allow shooting in the center of the target chamber. Some technical issues like wavefront correction, damage threshold in femtosecond regime and focusing are presented.
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