LLE Review 161

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Highlights

This volume of LLE Review 161, covering the period October–December 2019, is sectioned among research areas at LLE and external users of the Omega Laser Facility. Articles appearing in this volume are the principal summarized results of long-form research articles. Readers seeking a more-detailed account of research activities are invited to seek out the primary materials appearing 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:

• K. M. Woo et al. demonstrate that it is possible to infer the thermal ion temperature from nuclear measurements (p. 1). The inferred DD minimum ion temperatures demonstrate a strong correlation with the experimental yields in the OMEGA implosion database.
• H. G. Rinderknecht et al. describe the asymmetry limits of inertial confinement fusion implosions at the National Ignition Facility (NIF) (p. 3). Analysis of hot-spot plasma flows and areal densities point to an unexpected low-mode asymmetry. Investigation into causes of this asymmetry is ongoing.
• X. Bian et al. perform simulations of the effects of perturbation Reynolds number and Atwood number on the late-time growth of the Rayleigh–Taylor instability (p. 7). The analysis shows a strong correlation between vorticity and bubble velocity.
• J. P. Palastro et al. design a dephasingless laser wakefield accelerator (p. 10). A spatiotemporal technique is described and shown to deliver an ultrashort pulse without chromatic aberrations.
• R. K. Follett et al. present 3-D calculations of multibeam absolute stimulated Raman scattering thresholds (p. 13). The multi-beam coupling is shown to be weaker for stimulated Raman scattering than two-plasmon decay, consistent with OMEGA and NIF experiments.
• D. Haberberger et al. discuss a novel high-temperature Raman amplifier where laser–plasma instabilities are mitigated (p. 16).
• A. Kar et al. describe a microphysics model for hydrodynamic simulations (p. 19). Implementation of this model predicts higher values of electron density and pressure than the previously used ad hoc model.
• S. X. Hu et al. apply a thermal density function theory to investigate the radiation spectra of superdense plasma mixtures (p. 23). Calculations reveal interspecies and dipole-forbidden transitions that were not previously considered.
• M. J. Rosenberg et al. discuss stimulated Raman scattering mechanisms on the NIF (p. 25). Tangential sidescatter and near-backscatter were observed at lower densities.L. S. Leal et al. discuss a series of HYDRA simulations to model magnetic confinement of a laser-generated plasma (p. 28). It is shown that applying strong external fields to laser-generated plasmas leads to complex plasma structures.
• J. L. Peebles et al. demonstrate the diagnostic technique of axial proton probing of a laser-driven coil (p. 31).
• S. Zhang, H. D. Whitley, and T. Ogitsu calculate the equation of state and shock Hugoniot of various boron phases (p. 37). Results indicate inconsistency between Hugoniots of the equilibrium phases and those measured by shock experiments.
• O. M. Mannion et al. describe a suite of neutron time-of-flight detectors (p. 40). By combining neutron velocity measurements made by each detector, the neutron-averaged hot-spot velocity has been measured for the first time on OMEGA.
• T. Filkins and J. Katz present a design for a free-space, image-relay optical time domain reflectometer (p. 43). The uncertainty of the fiber-optic time delay is determined to be approximately 2 ps.
• J. Puth et al. summarize operations of the Omega Laser Facility during the first quarter of FY20 (p. 45).