Experimental study of radiative shocks at PALS facility

We report on the investigation of strong radiative shocks generated with the high energy, sub-nanosecond iodine laser at PALS. These shock waves are characterized by a developed radiative precursor and their dynamics is analyzed over long time scales (~50 ns), approaching a quasi-stationary limit. We present the first preliminary results on the rear side XUV spectroscopy. These studies are relevant to the understanding of the spectroscopic signatures of accretion shocks in Classical T Tauri Stars.Comment: 21 pages, 1 table, 7 figure

Laboratory experiments of Radiative Shocks, in the context of stellar accretion

International audienceRadiative shocks are high Mach number shocks with a strong coupling between radiation and hydrodynamics. These shocks occour in astrophysical system and in high-energy density laboratory experiments. High-energy lasers can be used to simulate astrophysical phenomena in the Laboratory. PALS Laser facility provides irradiance of 10¹4 W/cm², lasting less than 1 ns, and allows to produce radiative shocks in high atomic gas medium at low pressure. The radiative energy is converted into mechanical energy, generating the shock in the gas. The system is optimized for reaching conditions where the shock is radiative, i.e. it presents a radiative precursor. The experimental results of two new diagnostics: first a XUV instantaneous imaging at 21.2 mm, and second, a time and space resolved plasma self-emission using fast diodes will be highlighted. communication orale Atelier S08 Actes à paraître 2013 sur le site de la SF2

Experimental study of strong shocks driven by compact pulsed power

International audienceposter P.We₇

Hydrodynamic modeling of accretion shocks on a star with radiative transport and a chromospheric model

International audienceAccretion flows on the surface of a star is modeled using a high resolution hydrodynamic 1D ALE code (ASTROLABE) coupled to radiative transfer and line cooling, along with a model for the acoustic heating of the chromospheric plasma

X-ray laser imaging of a radiative shock

International audiencecommunication orale actes à paraître sur http://2013.sf2a.eu

Electromagnetic generation of strong shocks in low pressure gas

International audienceaffiche P71 atelier 12 PNPS The interstellar medium (ISM) is a wide object of research, especially for the phenomena leading to the building up of protostellar objects, like mass accretion or outflows and jets. Accretion shocks are of particular interest as their radiative signature can be related to the rate of mass accretion onto the forming star. In recent years, laboratory plasma experiments have been developed to study radiative shocks relevant to astrophysics. These scaled models of accretion shocks have been successfully generated on high power lasers by launching a fast moving piston in a stationary gaseous medium. Complementary to experiments on lasers, pulsed power generators are also able to create astrophysically relevant shocks. On these facilities, high-intensity currents can produce magnetic fields of several Tesla which act as a piston, accelerating an annular plasma sheath and driving a strong shock in a tenuous gas. The results presented will describe the pulsed power setup and a lumped-parameter model, linking the transient discharge dynamics and quantities like mass and speed of the plasma sheath. The results of this 0-D model will be compared to 3-D MHD simulations performed with the code GORGON. This work has lead to an optimization process of the setup. The diagnostics which are currently implemented will be presented to illustrate the model as well as experimental records of the plasma speed. Work supported by DIM ACAV Île-de-France region, Labex PLAS@PAR (ANR-11-IDEX-0004-02), Observatoire de Paris-Meudon and UPMC university

Line profiles of H-like ions of C, N, and O in stellar plasmas

International audienceTheoretical Stark profiles of Balmer and Lyman series of H-like ions of carbon, nitrogen, and oxygen are presented for a range of plasma conditions where these ions are dominant within their species. A convenient parametric formula is derived to fit the theoretical profiles, depending only on electronic density and the principal quantum number of the upper level of the transition. This analytic expression makes it easy to introduce these new profiles in many astrophysical applications. The effect of including these profiles in the calculation of radiative acceleration (g rad) following the method developed in an earlier paper is presented. The contributions of bound-bound (b-b) transitions of H-like ions to g rad is found to be smaller than previously computed, giving more importance to boundfree (b-f) and free-free (f-f) contributions