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Journal Articles Physics of Plasmas Year : 2023

Stationary Bragg reflection of laser light in inhomogeneous absorbing plasmas inside inertial confinement fusion Hohlraums

M. Vandenboomgaerde
M. Casanova
  • Function : Author
F. Chaland
M. Bonnefille
A. Grisollet
L. Videau
S. Depierreux
V. Tassin
C. Courtois
H. Chen

Abstract

Laser-produced plasma in inertial confinement fusion (ICF) Hohlraums are marked with density non-uniformity whose length scale can go down to micrometers. This scale is of the order of the laser wavelength. The WKB approximation, which is classically used in radiation-hydrodynamic codes to compute the laser trajectory, cannot correctly take into account such small-scale inhomogeneity of the plasma. Going beyond this approximation, we predict a novel mechanism for the laser reflection. We show that an electromagnetic plane wave with wave number k resonates with the kB=2 k Fourier component of a multimode perturbation of the background density and generates a reflected wave. It is the first time that this reflection is considered for stationary inhomogeneous ICF plasmas, and the energy absorption is taken into account. This mechanism, which is a form of Bragg reflection, can occur away from the critical surface and generate a drift of the location of the laser absorption. Furthermore, this absorption will be periodically modulated with a kB wave number. The stationary Bragg reflection can explain ongoing discrepancies between experimental and numerical data about laser trajectory and absorption in ICF Hohlraums.

Dates and versions

hal-04392295 , version 1 (13-01-2024)

Identifiers

Cite

M. Vandenboomgaerde, M. Casanova, F. Chaland, M. Bonnefille, A. Grisollet, et al.. Stationary Bragg reflection of laser light in inhomogeneous absorbing plasmas inside inertial confinement fusion Hohlraums. Physics of Plasmas, 2023, 30 (12), pp.122702. ⟨10.1063/5.0170189⟩. ⟨hal-04392295⟩
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