LLE Review 163

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Highlights

This volume of LLE Review 163 covers the period from April–June 2020. Articles appearing in this volume are the principal summarized results for long-form research articles. Readers seeing a more-detailed account of research activities are invited to seek out the primary materials appear in print, detailed in the publications and presentations section at the end of this volume.
Highlights of research presented in this volume include the following:

• R. C. Shah et al. characterize the onset of core x-ray emission from gated images of DT cryogenic implosions (p. 97). This onset is used to diagnose conditions at the start of deceleration of the shell and suggests that other perturbations, not included in models, cause decompression in more-stable, higher-adiabat implosions.
• O. M. Mannion et al. made the first temperature and velocity measurements of the shell in cryogenic implosions using the emitted neutron-energy spectrum (p. 100). These measurements, along with areal-density measurements of the shell, now provide a complete set of hydrodynamic properties of the dense fuel layer near peak compression.
• R. Epstein et al. develop a method where cryogenic implosions can be self-radiographed by their own core spectral emission without the need for spectral additives (p. 103).
• C. A. Thomas et al. analyze implosions on the “BigFoot” Platform at the National Ignition Facility and find that performance can be described by a simple function of the laser energy per unit mass, target scale, and implosion symmetry (p. 106).
• C. A. Thomas et al. also study implosions with different pulse shapes and find expressions the primary neutron yield and the neutron down-scatter ratio as functions of the laser energy per unit mass, target scale, implosion symmetry, and adiabat (p. 112).
• In addition, C. A. Thomas et al. find that the ion temperature, hot-spot areal density, and neutron yield implosion metrics for implosions using the BigFoot Platform are monotonic in laser energy (p. 118). Calculations agree well if the adiabat is increased by a factor of 1.4 relative to expectations.
• D. H. Barnak et al. completed analytical calculations that show that shifting the pointing of the OMEGA laser can eliminate the mode-5 perturbation in cylindrical implosions on OMEGA (p. 124).
• D. H. Barnak et al. also investigate measurements of the laser entrance hole window disassembly in terms of total emitted x-ray energy and compare this to other measurements and modeling results (p. 130).
• J. J. Ruby et al. present an application of Bayesian inference to derive quantitative physical information from integrated high-energy-density experiments (p. 138).
• S. Zhang and S. X. Hu apply a novel approach using many-body reactive force fields combined with first-principle ionization models to reveal species separation and hydrogen stream out of the CH upon shock release from inertial confinement fusion shells (p. 141).
• D. Turnbull et al. use a hot-spot model based on speckle statistics and simulation results from LPSE to explain higher levels of hot electrons from two-plasmon decay are observed when smoothing by spectral dispersion is turned off in direct-drive fusion experiments on OMEGA (p. 143).
• D. Ramsey et al. present a novel mechanism for the first vacuum acceleration of electrons in a single planar-like laser pulse in either the forward or backward direction (p. 146).
• L. E. Crandall et al. extend pressure and density measurements of the initially liquid and initially solid CO2 Hugoniot to 1 TPa and provide the first temperature measurements of shocked CO2 to 93,000 K (p. 149). They also propose a fluid phase diagram comprising at least three regimes to describe all existing shocked CO2 data.
• B. Henderson et al. present the principal Hugoniot and sound-speed data for silicon shocked to 320 to 2100 GPa (p. 153).
• R. Paul et al. use density functional theory to perform molecular dynamics and electro-optical calculations to study the effects of thermal excitations on the electronic properties of electride sodium (p. 156).
• C. Stoeckl et al. investigate a number of approaches to increase the brightness of x-ray backlighters and find that silicon targets with a CH shield showed the best performance (p. 159).
• F. J. Marshall et al. report on the development of Fresnel zone plates (FZP’s) to image x rays emitted by laser-generated plasma on OMEGA and OMEGA EP and show FZP results from Revolver experiments (p. 161).
• G. W. Jenkins, C. Feng, and J. Bromage examine the limits on hollow-core-fiber energy scaling and simulate divided-pulse nonlinear compression, which is a method to overcome those limits (p. 163).
• J. Puth et al. summarize operations of the Omega Laser Facility during the third quarter of FY20 (p. 166).