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Now showing items 1 - 4 of 4

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

    Volpe, L.   Fedosejevs, R.   Gatti, G.   Pérez-Hernández, J. A.   Méndez, C.   Apiñaniz, J.   Vaisseau, X.   Salgado, C.   Huault, M.   Malko, S.   Zeraouli, G.   Ospina, V.   Longman, A.   De Luis, D.   Li, K.   Varela, O.   García, E.   Hernández, I.   Pisonero, J. D.   García Ajates, J.   Alvarez, J. M.   García, C.   Rico, M.   Arana, D.   Hernández-Toro, J.   Roso, L.  

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  • Time evolution of stimulated Raman scattering and two-plasmon decay at laser intensities relevant for shock ignition in a hot plasma

    Cristoforetti, G.   Antonelli, L.   Mancelli, D.   Atzeni, S.   Baffigi, F.   Barbato, F.   Batani, D.   Boutoux, G.   D'Amato, F.   Dostal, J.   Dudzak, R.   Filippov, E.   Gu, Y. J.   Juha, L.   Klimo, O.   Krus, M.   Malko, S.   Martynenko, A. S.   Nicolai, Ph   Ospina, V   Pikuz, S.   Renner, O.   Santos, J.   Tikhonchuk, V. T.   Trela, J.   Viciani, S.   Volpe, L.   Weber, S.   Gizzi, L. A.  

    Laser-plasma interaction (LPI) at intensities 10(15)-10(16) is dominated by parametric instabilities which can be responsible for a significant amount of non-collisional absorption and generate large fluxes of high-energy nonthermal electrons. Such a regime is of paramount importance for inertial confinement fusion (ICF) and in particular for the shock ignition scheme. In this paper we report on an experiment carried out at the Prague Asterix Laser System (PALS) facility to investigate the extent and time history of stimulated Raman scattering (SRS) and two-plasmon decay (TPD) instabilities, driven by the interaction of an infrared laser pulse at an intensity similar to 1:2 x 1016 with a similar to 100 mu m scalelength plasma produced from irradiation of a flat plastic target. The laser pulse duration (300 ps) and the high value of plasma temperature (similar to 4 keV) expected from hydrodynamic simulations make these results interesting for a deeper understanding of LPI in shock ignition conditions. Experimental results show that absolute TPD/SRS, driven at a quarter of the critical density, and convective SRS, driven at lower plasma densities, are well separated in time, with absolute instabilities driven at early times of interaction and convective backward SRS emerging at the laser peak and persisting all over the tail of the pulse. Side-scattering SRS, driven at low plasma densities, is also clearly observed. Experimental results are compared to fully kinetic large-scale, two-dimensional simulations. Particle-in-cell results, beyond reproducing the framework delineated by the experimental measurements, reveal the importance of filamentation instability in ruling the onset of SRS and stimulated Brillouin scattering instabilities and confirm the crucial role of collisionless absorption in the LPI energy balance.
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  • Generation of high energy laser-driven electron and proton sources with the 200 TW system VEGA 2 at the Centro de Laseres Pulsados

    Volpe, L.   Fedosejevs, R.   Gatti, G.   Perez-Hernandez, J. A.   Mendez, C.   Apinaniz, J.   Vaisseau, X.   Salgado, C.   Huault, M.   Malko, S.   Zeraouli, G.   Spina, V   Longman, A.   De Luis, D.   Li, K.   Varela, O.   Garcia, E.   Hernandez, I   Pisonero, J. D.   Garcia Ajates, J.   Alvarez, J. M.   Garcia, C.   Rico, M.   Arana, D.   Hernandez-Toro, J.   Roso, L.  

    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 =3D 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 =3D 40 cm) is for overdense laser-matter interaction where VEGA 2 is focused onto a 5 mu m 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.
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  • Soft X-ray measurements with a gas detector coupled to microchips in laser-plasma experiments at VEGA-2

    Claps, G.   Cordella, F.   Pacella, D.   Romano, A.   Murtas, F.   Batani, D.   Turianska, O.   Raffestin, D.   Volpe, L.   Zeraouli, G.   Perez-Hernandez, J. A.   Malko, S.  

    This work presents an innovative usage of the GEMpix detector for soft X-rays (SXR) measurements aimed to make an estimate of the electron temperature of a Laser Produced Plasma (LPP). The GEMpix is a proportional gas detector based on three Gas Electron Multipliers (GEMs) with a Front-End Electronics (FEE) based on four Timepix chips. This FEE provides the Time over Threshold (ToT) acquisition mode pixel by pixel and then a digital measure of the released charge in the gas mixture. In addition, the charge can be amplified through the GEM foils with 4 orders of magnitude spanning gain offering, in this way, a big dynamic range and adjustable sensitivity. Chip design provides a threshold for each channel. All the thresholds are set in order to cut electronic noise and detect X-rays. In this configuration, a cut on the low amplitude signals is set, but the gain has been tuned in order to observe the main signal due to the soft X-rays reaching the detector. This detector works in an energy range between 2 to 15 keV. It offers good imaging properties, high efficiency and absolute calibration. It offers a good immunity to Electromagnetic Pulse (EMP), as checked at VEGA-2 laser facility (hundreds of TWin about 30 fs). In these experiments, where the formation of warm dense matter produced by blast waves has been studied, a measure of the plasma temperature was required. This measurement was realized applying some filters on the active area of the detector, in correspondence of three chips. With this configuration a study of the GEMpix response due to the photons coming from the coronal plasma produced by the laser on the target has been done for each single shot. GEMpix revealed innovative and attractive features, compared to the state of the art where passive films or detectors based on indirect conversion are used, for SXR imaging and spectral analysis to infer the electron temperature.
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