Publications

2015

• Polarization analysis of CuXX-lines emitted from X-pinch
  
  • Baronova E O
  • Larour Jean
  • Rosmej F B
  • Khattak F y
  Journal of Physics: Conference Series, IOP Science, 2015, 653, pp.012145. Soft x-ray emission from CuXX L-shell lines emitted by a dense X-pinch plasma have been investigated with high-resolution curved Bragg crystals at different angles of orientation. Single shot time integrated spectra show clear evidences of polarization for the Ne-like spectral lines 2s22p6 1S0 → 2s22p53s 1P1 (λ = 12.570 Å), 2s22p6 1S0 → 2s22p53s 3P1 (λ = 12.8277 Å). The variation of the intensity ratio of these two well-separated L-shell lines is discussed in view of its application for suprathermal electron characterization under real experimental conditions of pinch plasmas. We demonstrated that the simultaneous use of two different polarization spectrometers (means 4 Bragg crystals) permitted a high level of confidence for the analysis of the variation of the line ratios due to polarization. (10.1088/1742-6596/653/1/012145)
  DOI : 10.1088/1742-6596/653/1/012145
• Laser-delayed double shock-wave generation in water-confinement regime
  
  • Courapied D
  • Berthe Laurent
  • Peyre Patrice
  • Coste Frédéric
  • Zou J-P
  • Sautivet A.-M.
  Journal of Laser Applications, Laser Institute of America, 2015, 27, pp.S29101. This paper investigates the different physical processes involved during laser-delayed double shock-wave generation in water-confined geometry. With this technique, two laser pulses, separated by a Δt duration, irradiate a target immersed in water at an intensity of a few GW/cm2 and form a high pressure plasma which results in a double shock-wave generation. This 2 pulses configuration is currently being investigated as an attractive method for improving the LASer Adhesion Test (LASAT) [L. M. Barker and R. E. Hollenbach, J. Appl. Phys. 43, 4669–4674 (1972)] technique by adapting the time delay Δt to the position of interfaces. The LASAT technique is a noncontact adhesion test allowing to generate a high-level tensile stress near interfaces with the use of laser-driven shock wave. The generation of two delayed high-intensity shock waves by laser plasma in the water-confinement regime has been investigated at 10ns@532 nm with the new Nd:YAG laser GAIA from Thales Laser company in the new facility HEPHAISTOS. For each incident Gaussian laser impulsion, the characterization of the high-amplitude laser-plasma-generated shock wave and its propagation through the target has been performed using a velocity interferometer system for any reflector [L. Berthe et al., “State-of-the-art laser adhesion test (LASAT),” Nondestr. Test. Eval. 26(3–4), 303–317 (2011)]. The new laser facility allows us a nanosecond-control of the time delay between the two laser pulses and a precise control of each laser maximum-intensity. Therefore, the influence of the first laser-induced plasma, on the second shock-wave generation has been studied by modifying different parameters such as the delay Δt and the intensity I1 and 12 of each pulse and different aluminum plate thicknesses from 0.2 to 1.5 mm. Preliminary tests show that the maximum pressure level of the second generated shock wave is sensitive to the time delay between the two impulsions and influenced by the plasma generated by the first laser pulse. (10.2351/1.4906382)
  DOI : 10.2351/1.4906382
• X-ray absorption K edge as a diagnostic of the electronic temperature in warm dense aluminum
  
  • Dorchies F.
  • Festa F.
  • Recoules V.
  • Peyrusse O.
  • Benuzzi-Mounaix A.
  • Brambrink E.
  • Lévy A.
  • Ravasio A.
  • Koenig M.
  • Hall T.
  • Mazevet S.
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2015, 92 (8). no abstract (10.1103/PhysRevB.92.085117)
  DOI : 10.1103/PhysRevB.92.085117
• Analysis of X-ray and Thomson scattering data from non-LTE Nb and Ta plasmas
  
  • Bastiani-Ceccotti S.
  • Bourgaux A. C.
  • Bowen C.
  • Dorchies F.
  • Gilleron F.
  • Marques J. R.
  • Pain J. C.
  • Silvert V.
  • Vinci T.
  High Energy Density Physics, Elsevier, 2015, 16, pp.41-52. no abstract
• X-ray absorption spectroscopy of iron at multimegabar pressures in laser shock experiments
  
  • Harmand M
  • Ravasio A
  • Mazevet S
  • Bouchet J
  • Denoeud A
  • Dorchies F
  • Feng Y
  • Fourment C
  • Galtier E
  • Gaudin Jerôme
  • Guyot F
  • Kodama R
  • Koenig M
  • Lee Hj.
  • Miyanishi K
  • Morard Guillaume
  • Musella R
  • Nagler B
  • Nakatsutsumi M
  • Ozaki N
  • Recoules V
  • Toleikis S
  • Vinci T
  • Zastrau U
  • Zhu D
  • Benuzzi-Mounaix A
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2015, 92 (2), pp.024108. Taking advantage of the new opportunities provided by x-ray free electron laser (FEL) sources when coupled to a long laser pulse as available at the Linear Coherent Light Source (LCLS), we have performed x-ray absorption near-edge spectroscopy (XANES) of laser shock compressed iron up to 420 GPa (±50) and 10 800 K (±1390). Visible diagnostics coupled with hydrodynamic simulations were used to infer the thermodynamical conditions along the Hugoniot and the release adiabat. A modification of the pre-edge feature at 7.12 keV in the XANES spectra is observed above pressures of 260 GPa along the Hugoniot. Comparing with ab initio calculations and with previous laser-heated diamond cell data, we propose that such changes in the XANES pre-edge could be a signature of molten iron. This interpretation then suggests that iron is molten at pressures and temperatures higher than 260 GPa (±29) and 5680 K (±700) along the principal Fe Hugoniot. (10.1103/PhysRevB.92.024108)
  DOI : 10.1103/PhysRevB.92.024108
• Simple scalings for various regimes of electron acceleration in surface plasma waves
  
  • Riconda C.
  • Raynaud M.
  • Vialis T.
  • Grech M.
  Physics of Plasmas, American Institute of Physics, 2015, 22 (7), pp.073103. Different electron acceleration regimes in the evanescent field of a surface plasma wave are studied by considering the interaction of a test electron with the high-frequency electromagnetic field of a surface wave. The non-relativistic and relativistic limits are investigated. Simple scalings are found demonstrating the possibility to achieve an efficient conversion of the surface wave field energy into electron kinetic energy. This mechanism of electron acceleration can provide a high-frequency pulsed source of relativistic electrons with a well defined energy. In the relativistic limit, the most energetic electrons are obtained in the so-called electromagnetic regime for surface waves. In this regime, the particles are accelerated to velocities larger than the wave phase velocity, mainly in the direction parallel to the plasma-vacuum interface. (10.1063/1.4923443)
  DOI : 10.1063/1.4923443
• Are long gamma-ray bursts biased tracers of star formation? Clues from the host galaxies of the Swift/BAT6 complete sample of LGRBs
  
  • Vergani S. D.
  • Salvaterra R.
  • Japelj J.
  • Le Floc’h E.
  • D’avanzo P.
  • Fernandez-Soto A.
  • Krühler T.
  • Melandri A.
  • Boissier Samuel
  • Covino S.
  • Puech M.
  • Greiner J.
  • Hunt L. K.
  • Perley D.
  • Petitjean P.
  • Vinci T.
  • Hammer F.
  • Levan A.
  • Mannucci F.
  • Campana S.
  • Flores H.
  • Gomboc A.
  • Tagliaferri G.
  Astronomy & Astrophysics - A&A, EDP Sciences, 2015, 581, pp.A102. Aims. Long gamma-ray bursts (LGRBs) are associated with massive stars and are therefore linked to star formation. However, the conditions needed for the progenitor stars to produce LGRBs can affect the relation between the LGRB rate and star formation. By using the power of a complete LGRB sample, our long-term aim is to understand whether such a bias exists and, if it does, what its origin is. Methods. To reach our goal we use the Swift/BAT6 complete sample of LGRBs. In this first paper, we build the spectral energy distribution (SED) of the 14 z < 1 host galaxies of the BAT6 LGRB sample and determine their stellar masses (M⋆) from SED fitting. To investigate the presence of a bias in the LGRB-star formation relation we compare the stellar mass distribution of the LGRB host galaxies (i) with star-forming galaxies observed in deep surveys (UltraVISTA) within the same redshift limit; (ii) with semi-analytical models of the z < 1 star-forming galaxy population; and (iii) with dedicated numerical simulations of LGRB hosts having different metallicity thresholds for the progenitor star environment. Results. We find that at z < 1, LGRBs tend to avoid massive galaxies and are very powerful for selecting a population of faint low-mass star-forming galaxies, partly below the completeness limits of galaxy surveys. The stellar mass distribution of the hosts is not consistent with that of the UltraVISTA star-forming galaxies weighted by their star formation rate (SFR). This implies that, at least at z < 1, LGRBs are not unbiased tracers of star formation. To make the two distributions consistent, a much steeper faint end of the mass function would be required or a very shallow SFR-mass relation for the low-mass galaxy population. The comparison with the GRB host galaxy simulations indicates that, to reproduce the stellar mass distribution, a metallicity threshold of the order of Zth = 0.3−0.5Z⊙ is necessary to form a LGRB. Models without a metallicity threshold or with an extreme threshold of Zth = 0.1 Z⊙ are excluded at z < 1. Under a very basic assumption, we estimate that the LGRB rate can directly trace the SFR starting from z ~ 4 and above. Conclusions. GRB hosts at z < 1 have lower luminosities and stellar masses than expected if LGRBs were unbiased star formation tracers. The use of the Swift/BAT6 complete sample keeps this result from being affected by possible biases that could have influenced past results based on incomplete samples. The preference for low metallicities (Z ≲ 0.5 Z⊙) inferred by the comparison with the simulations can be a consequence of the particular conditions needed for the progenitor star to produce a GRB. (10.1051/0004-6361/201425013)
  DOI : 10.1051/0004-6361/201425013