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174 results on '"P. Nicolaï"'

1. Collisionless shock acceleration of protons in a plasma slab produced in a gas jet by the collision of two laser-driven hydrodynamic shockwaves

Author

J.-R. Marquès, L. Lancia, P. Loiseau, P. Forestier-Colleoni, M. Tarisien, E. Atukpor, V. Bagnoud, C. Brabetz, F. Consoli, J. Domange, F. Hannachi, P. Nicolaï, M. Salvadori, and B. Zielbauer

Subjects
Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

We have recently proposed a new technique of plasma tailoring by laser-driven hydrodynamic shockwaves generated on both sides of a gas jet [Marquès et al., Phys. Plasmas 28, 023103 (2021)]. In a continuation of this numerical work, we study experimentally the influence of the tailoring on proton acceleration driven by a high-intensity picosecond laser in three cases: without tailoring, by tailoring only the entrance side of the picosecond laser, and by tailoring both sides of the gas jet. Without tailoring, the acceleration is transverse to the laser axis, with a low-energy exponential spectrum, produced by Coulomb explosion. When the front side of the gas jet is tailored, a forward acceleration appears, which is significantly enhanced when both the front and back sides of the plasma are tailored. This forward acceleration produces higher-energy protons, with a peaked spectrum, and is in good agreement with the mechanism of collisionless shock acceleration (CSA). The spatiotemporal evolution of the plasma profile is characterized by optical shadowgraphy of a probe beam. The refraction and absorption of this beam are simulated by post-processing 3D hydrodynamic simulations of the plasma tailoring. Comparison with the experimental results allows estimation of the thickness and near-critical density of the plasma slab produced by tailoring both sides of the gas jet. These parameters are in good agreement with those required for CSA.

Published
2024
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2. Experimental investigation of the interplay between optical and plasma smoothing induced on a laser megajoule beamline

Author

S. Depierreux, D. Pesme, R. Wrobel, D. T. Michel, P.-E. Masson-Laborde, G. Riazuelo, E. Alozy, N. Borisenko, A. Orekhov, M. Casanova, A. Casner, M. Grech, A. Heron, S. Huller, P. Loiseau, C. Meyer, P. Nicolaï, C. Riconda, V. Tikhonchuk, and C. Labaune

Subjects
Physics, QC1-999
Abstract

Past experiments [S. Depierreux et al., Phys. Rev. Lett. 102, 195005 (2009)10.1103/PhysRevLett.102.195005] have exhibited the plasma-induced incoherence (PII) process and the reduced imprint in the multikilojoule regime when a thin low-density foam is disposed in front of a solid target. Complementary experiments have been designed to analyze the mechanisms involved, the important parameters, and the role of the optical smoothing in the case of the laser megajoule. Forward stimulated Brillouin scattering (FSBS) is identified as the dominant mechanism governing the angular spray of the laser. FSBS also increases the laser bandwidth and imparts levels of temporal and spatial incoherencies beyond the present capacities of the optical smoothing of the megajoule laser facilities. Such a PII beam becomes suitable to achieve the high degree of irradiation uniformity required to experiment high-convergence efficient direct-drive inertial confinement fusion configurations at the megajoule scale which would otherwise require major changes in the laser chains. By reducing backscattering losses and/or allowing less optically applied smoothing, PII could relax the constraints imposed on the laser system and open the road to an increase in the energy coupled to the target in indirect-drive experiments.

Published
2023
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14. The Blursday database as a resource to study subjective temporalities during COVID-19

Author

Chaumon, Maximilien, Rioux, Pier-Alexandre, Herbst, Sophie K., Spiousas, Ignacio, Kübel, Sebastian L., Gallego Hiroyasu, Elisa M., Runyun, Şerife Leman, Micillo, Luigi, Thanopoulos, Vassilis, Mendoza-Duran, Esteban, Wagelmans, Anna, Mudumba, Ramya, Tachmatzidou, Ourania, Cellini, Nicola, D’Argembeau, Arnaud, Giersch, Anne, Grondin, Simon, Gronfier, Claude, Igarzábal, Federico Alvarez, Klarsfeld, André, Jovanovic, Ljubica, Laje, Rodrigo, Lannelongue, Elisa, Mioni, Giovanna, Nicolaï, Cyril, Srinivasan, Narayanan, Sugiyama, Shogo, Wittmann, Marc, Yotsumoto, Yuko, Vatakis, Argiro, Balcı, Fuat, and van Wassenhove, Virginie

Published
2022
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21. Growth Mindset and Its Predictive Validity--Do Migration Background and Academic Validation Matter?

Author

Corradi, David, Nicolaï, Jonas, and Levrau, François

Abstract

A wide range of mindset interventions has been designed to tackle the educational gap and improve the academic achievements of underperforming students. These interventions often target small student samples in experimental or homogeneous educational settings. This paper will explicitly emphasize the role of context in the relationship between growth mindset and academic achievement in order to optimize the potential impact of mindset interventions. Based on the Self-System of Motivational Development, we offer a framework which allows for investigating the mediating function of growth mindset between the contextual factors of "minority background" and "academic validation," as well as students' levels of academic adjustment and academic outcome. Our data, drawn from survey research (N = 1549) in a Belgian university, indicate both an inverse, negative effect of mindset on academic outcomes--with little impact of context on mindset--as well as positive effects of academic validation on academic outcome among minority students. These results suggest that academic outcome depends on more than whether students are located on the positive or negative side of the mindset spectrum.

Published
2019
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