Hohlraum modeling for opacity experiments on the National Ignition Facility

Journal Article · 08 June 2018 · Physics of Plasmas

DOI: https://doi.org/10.1063/1.5026285 · OSTI ID:1479930

Dodd, Evan S.  ^[1]; DeVolder, Barbara Gloria ^[1]; Martin, M. E. ^[2]; Krasheninnikova, Natalia Sergeevna  ^[1]; Tregillis, Ian Lee ^[1]; Perry, Theodore Sonne  ^[1]; Heeter, R. F.  ^[2]; Opachich, Y. P.  ^[3]; Moore, A. S. ^[1]; Kline, John L.  ^[1]; Johns, Heather Marie  ^[1]; Liedahl, D. A. ^[2]; Cardenas, Tana ^[1]; Olson, Richard Edward  ^[1]; Wilde, Bernhard Heinz ^[1]; Urbatsch, Todd James  ^[1]

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1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
3. National Security Technologies, LLC, Livermore, CA (United States)

This paper discusses the modeling of experiments that measure iron opacity in local thermodynamic equilibrium (LTE) using laser-driven hohlraums at the National Ignition Facility (NIF). A previous set of experiments fielded at Sandia's Z facility [Bailey et al., Nature 517, 56 (2015)] have shown up to factors of two discrepancies between the theory and experiment, casting doubt on the validity of the opacity models. The purpose of the new experiments is to make corroborating measurements at the same densities and temperatures, with the initial measurements made at a temperature of 160 eV and an electron density of 0.7 × 10²² cm^-3. The X-ray hot spots of a laser-driven hohlraum are not in LTE, and the iron must be shielded from a direct line-of-sight to obtain the data [Perry et al., Phys. Rev. B 54, 5617 (1996)]. This shielding is provided either with the internal structure (e.g., baffles) or external wall shapes that divide the hohlraum into a laser-heated portion and an LTE portion. In contrast, most inertial confinement fusion hohlraums are simple cylinders lacking complex gold walls, and the design codes are not typically applied to targets like those for the opacity experiments. We will discuss the initial basis for the modeling using LASNEX, and the subsequent modeling of five different hohlraum geometries that have been fielded on the NIF to date. This includes a comparison of calculated and measured radiation temperatures.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC52-06NA25396; AC52-07NA27344; AC52-06NA25946
• OSTI ID: 1479930
• Alternate ID(s): OSTI ID: 1441085; OSTI ID: 1784605
• Report Number(s): LA-UR-17-28949; LLNL-JRNL-822929
• Journal Information: Physics of Plasmas, Vol. 25, Issue 6; ISSN 1070-664X
• Publisher: American Institute of Physics (AIP)Copyright Statement
• Country of Publication: United States
• Language: English