Ray-Based Calculations with DEPLETE of Laser Backscatter in ICF Targets

Conference · Mon May 19 04:00:00 EDT 2008

OSTI ID:945813

Strozzi, D J; Williams, E; Hinkel, D; Froula, D; London, R; Callahan, D

A steady-state model for Brillouin and Raman backscatter along a laser ray path is presented. The daughter plasma waves are treated in the strong damping limit, and have amplitudes given by the (linear) kinetic response to the ponderomotive drive. Pump depletion, inverse-bremsstrahlung damping, bremsstrahlung emission, Thomson scattering off density fluctuations, and whole-beam focusing are included. The numerical code Deplete, which implements this model, is described. The model is compared with traditional linear gain calculations, as well as 'plane-wave' simulations with the paraxial propagation code pF3D. Comparisons with Brillouin-scattering experiments at the Omega Laser Facility show that laser speckles greatly enhance the reflectivity over the Deplete results. An approximate upper bound on this enhancement is given by doubling the Deplete coupling coefficient. Analysis with Deplete of an ignition design for the National Ignition Facility (NIF), with a peak radiation temperature of 285 eV, shows encouragingly low reflectivity. Doubling the coupling to bracket speckle effects suggests a less optimistic picture. Re-absorption of Raman light is seen to be significant in this design.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA
• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 945813
• Report Number(s): LLNL-CONF-404196
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ABSORPTION
AMPLITUDES
BREMSSTRAHLUNG
BRILLOUIN EFFECT
DAMPING
DESIGN
FLUCTUATIONS
FOCUSING
IGNITION
KINETICS
LASERS
PLASMA WAVES
RADIATIONS
REFLECTIVITY
THOMSON SCATTERING
US NATIONAL IGNITION FACILITY