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Liotard R, Canaud B, Pineau A, Sollier A, Lescoute E, Colaïtis A, Duchateau G. Solid-to-plasma transition of polystyrene induced by a nanosecond laser pulse within the context of inertial confinement fusion. Phys Rev E 2024; 109:065207. [PMID: 39020904 DOI: 10.1103/physreve.109.065207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 04/01/2024] [Indexed: 07/20/2024]
Abstract
Laser direct drive (LDD) inertial confinement fusion (ICF) involves irradiating a spherical target of thermonuclear fuel coated with an ablator, usually made of polystyrene. Laser energy absorption near the target surface leads to matter ablation, hydrodynamic shocks, and ultimately capsule implosion. The conservation of spherical symmetry is crucial for implosion efficiency, yet spatial modulations in laser intensity can induce nonuniformities, causing the laser imprint phenomenon. Understanding laser imprint, especially considering the initial solid state, is essential for advancing LDD ICF. A first microscopic model of solid-to-plasma transition was built in 2019, accounting for laser absorption in the solid state with a band-structure-based ionization model. This model has been improved to include chemical fragmentation and a more accurate description of electron collision frequency in various matter states. The latest development involves assessing the model's reliability by comparing theoretical predictions with experimental observations. Despite the success of this approach, questions remain, leading to further investigations and observations under different irradiation conditions. This work presents an experiment with a nanosecond pulse, taking into account hydrodynamic effects, and measures transmission dynamics over the entire laser beam area to observe two-dimensional effects. The objective is to adapt the theoretical model, couple it with a hydrodynamic code, and observe additional effects related to the initial solid state.
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Affiliation(s)
| | - B Canaud
- Université Paris-Saclay, CEA, LMCE, F-91680 Bruyères-le-Châtel, France and CEA, DAM, DIF, F-91297 Arpajon, France
| | - A Pineau
- Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623, USA
| | - A Sollier
- Université Paris-Saclay, CEA, LMCE, F-91680 Bruyères-le-Châtel, France and CEA, DAM, DIF, F-91297 Arpajon, France
| | - E Lescoute
- Université Paris-Saclay, CEA, LMCE, F-91680 Bruyères-le-Châtel, France and CEA, DAM, DIF, F-91297 Arpajon, France
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Pineau A, Chimier B, Hu SX, Duchateau G. Improved modeling of the solid-to-plasma transition of polystyrene ablator for laser direct-drive inertial confinement fusion hydrocodes. Phys Rev E 2021; 104:015210. [PMID: 34412245 DOI: 10.1103/physreve.104.015210] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 06/25/2021] [Indexed: 11/07/2022]
Abstract
The target performance of laser direct-drive inertial confinement fusion (ICF) can be limited by the development of hydrodynamic instabilities resulting from the nonhomegeneous laser absorption at the target surface, i.e., the laser imprint on the ablator. To understand and describe the formation of these instabilities, the early ablator evolution during the laser irradiation should be considered. In this work, an improved modeling of the solid-to-plasma transition of a polystyrene ablator for laser direct-drive ICF is proposed. This model is devoted to be implemented in hydrocodes dedicated to ICF which generally assume an initial plasma state. The present approach consists of the two-temperature model coupled to the electron, ion and neutral dynamics including the chemical fragmentation of polystyrene. The solid-to-plasma transition is shown to significantly influence the temporal evolution of both free electron density and temperatures, which can lead to different shock formation and propagation compared with an initial plasma state. The influence of the solid-to-plasma transition on the shock dynamics is evidenced by considering the scaling law of the pressure with respect to the laser intensity. The ablator transition is shown to modify the scaling law exponent compared with an initial plasma state.
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Affiliation(s)
- A Pineau
- Université de Bordeaux-CNRS-CEA, Centre Lasers Intenses et Applications, UMR 5107, 351 Cours de la Libération, 33405 Talence Cedex, France
| | - B Chimier
- Université de Bordeaux-CNRS-CEA, Centre Lasers Intenses et Applications, UMR 5107, 351 Cours de la Libération, 33405 Talence Cedex, France
| | - S X Hu
- Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623, USA
| | - G Duchateau
- Université de Bordeaux-CNRS-CEA, Centre Lasers Intenses et Applications, UMR 5107, 351 Cours de la Libération, 33405 Talence Cedex, France.,CEA CESTA, 15 Avenue des Sablières, CS60001, 33116 Le Barp Cedex, France
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