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American Institute of Physics, Physics of Plasmas, 9(29), p. 092704, 2022

DOI: 10.1063/5.0099937

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Specular reflections (“glint”) of the inner beams in a gas-filled cylindrical hohlraum

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

We report on the experimental measurement of specular reflection (“glint”) of laser beams off the hohlraum wall in inertial confinement fusion experiments at the National Ignition Facility. In a hohlraum, glinted light can escape the opposite laser entrance hole of the hohlraum and is a potential laser energy loss mechanism. The total measured glint on the inner cones of beams is measured to be less than 8 TW (when using the full National Ignition Facility laser), which is <2% of incident peak power. The simulated x-ray flux exceeds the measurement by 10%–20%, and glinted laser light is unable to account for this discrepancy. Similar inner beam glint was measured for ρ = 0.3 and 0.6 mg/cc gas fill hohlraums, but no glint was detected for 1.2 mg/cc densities. Inner beam glint is dominated by the lowest angle 21.5 beams within a 23.5 quad, and it is at most 30% sensitive to different quad polarization arrangements.