Bulletin of the American Physical Society
62nd Annual Meeting of the APS Division of Plasma Physics
Volume 65, Number 11
Monday–Friday, November 9–13, 2020; Remote; Time Zone: Central Standard Time, USA
Session CP17: Poster Session: ICF: Fundamental (2:00pm  5:00pm)On Demand

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CP17.00001: Implosions for Studying Solar CNO Reactions Justin Jeet, Yongho Kim, Maria Johnson, Alex Zylstra Inertial fusion implosions can be utilized to study nuclear astrophysics. In the `CNO process', hydrogen burning is catalyzed in the presence of $^{\mathrm{12}}$C. These reactions are more strongly dependent on temperature than the pp cycle reactions and dominate only in massive stars. For research using ICF facilities, an implosion platform using heavier nuclei in the fuel and capable of creating ion temperatures of at least 30 keV is required. A potential route to reach these conditions is to take advantage of kinetic effects in lowconvergence shockdriven `exploding pusher' implosions. Ion thermal decoupling has been observed in such implosions. While the exact mechanism for shock heating is not clear (collisional vs electrostatic), a significant boost in ion temperature, up to a factor of 612x vs a hydrogen ion, is expected for carbon or heavier ions. Shots will be conducted at the OMEGA laser facility using the surrogate reaction $^{\mathrm{13}}$C $+$ D. Its cross section is substantially higher than the actual astrophysical CNO reactions. The results will inform whether ion decoupling physics occurs according to simple theory and if it can be exploited to generate effective reaction temperatures exceeding 20 keV for relevant CNO reactions. [Preview Abstract] 

CP17.00002: Modeling of the OpacityonNIF hohlraum for Anchor 2 ES Dodd, NS Krasheninnikova, NB Ramey, P Hakel, CJ Fontes, RA London, IL Tregillis, TS Perry, RF Heeter, HM Johns, YP Opachich, TH Day, T Cardenas, BH Wilde, TJ Urbatsch, MR Douglas The OpacityonNIF experiments have begun taking data for LTE opacity measurements of iron at conditions referred to as Anchor 2: 180 eV and 3\texttimes 10$^{\mathrm{22}}$ cm$^{\mathrm{3}}$ [1]. Iron opacities are important for understanding the structure of the sun, yet there is an ongoing disagreement between opacity theory and data that makes corroboration highly important. Complex hohlraum geometries are required to achieve the necessary iron plasma conditions and minimize spectrometer background [2], however moving to the Anchor 2 conditions has forced a reexamination of background sources. Windows on the hohlraum have been used to create a plasma fill that holds the expanding gold wall out of the spectrometer lineofsight. We will discuss the role of windows and the prepulse used to disassemble them in creating spectrometer background, based on Lasnex calculations. We will also examine the use of Be liners on the hohlraum wall, instead of windows, to better reduce background in the measured spectra. [1] J. E. Bailey, \textit{et al.}, \textit{Nature,} \textbf{517} 56 (2015). [2] E. S. Dodd, \textit{et al.}, Phys. Plasmas \textbf{25}, 063301 (2018). [Preview Abstract] 

CP17.00003: Modeling the cold side expansion of directly driven CH foils, driven by radiative preheat Mordecai Rosen 

CP17.00004: Abstract Withdrawn We discuss a fully kinetic (electrons and ions) algorithm for solving the 1D2V VlasovFokkerPlanckAmpere system. The numerical stiffness of fast timescales is addressed through a fully implicit temporal discretization (BDF2), which is accelerated via a multiscale momentbased preconditioner (HOLO). A system of Lagrangemultiplierlike nonlinear constraint functions are used to enforce discrete conservation of mass, momentum, energy, and charge proportionally to the nonlinear convergence tolerance of the solver. We demonstrate the algorithmic performance of the solver and present results for benchmark problems. In addition, we demonstrate application of the solver to a fully kinetic planar plasma shock, including a preliminary investigation of the effects of fully kinetic electrons (e.g., nonlocal heat transport). 

CP17.00005: A Geometric ParticleinCell Method for Magnetized and Polarized Media William Barham, Philip Morrison, Eric Sonnendruecker The MaxwellVlasov equations were shown to possess a noncanonical Hamiltonian structure in [1]. The Poisson bracket of this Hamiltonian theory demonstrates that the MaxwellVlasov equations possess a geometric structure. Of particular interest are the conserved quantities known as Casimir invariants. The geometric electromagnetic particleincell (GEMPIC) computational framework exposited in [2] provides a means of discretizing the MaxwellVlasov equations in a manner that replicates in finite dimensions the Poisson manifold structure of the continuous model. A method of lifting the characteristics of a particle model to a kinetic model in a gauge invariant manner was given in [3]. Moreover, it was shown that many kinetic models of interest, such as drift kinetic models or gyrokinetic models, yield Maxwell's equations in a polarized and magnetized medium with these fields related to the electric and magnetic fields selfconsistently through an energy functional. This work incorporates such models into the GEMPIC framework. \\ {[1]} P. J. Morrison. Phys. Lett. {\bf80A}, 383 1980. \\ {[2]} M. Kraus, K. Kormann, P.J. Morrison, and Eric Sonnendr\”ucker. J. Plasma Phys. {\bf83}, 905830401 (2017). \\ {[3]} P. J. Morrison. Phys. Plasmas, {\bf 20}, 012104 (2013). [Preview Abstract] 

CP17.00006: Evidence for species separation in directdrive DTHfilled capsule implosions based on statistical inference and predictions with quantified uncertainty Nelson Hoffman, Yongho Kim We are using the GPMSA (Gaussian Process Models for Simulation Analysis) statistical inference code to analyze inertialfusion capsule experiments carried out at OMEGA that were intended to investigate the separation of H, D, and T ions during the implosion. A set of DTfilled capsules provide a reference observeddata set, while radiationhydrodynamic simulations with an iondiffusion transport model provide a simulation tool for explaining the data. GPMSA is used to infer model parameter distributions, and generate the predicted behavior of DTHfilled capsules, with uncertainty bounds. If observed DTH capsule performance departs significantly from the predicted performance, we regard that departure as evidence for an unexplained degree of species separation in such implosions. This approach allows us to assign confidence levels to such conclusions. [Preview Abstract] 

CP17.00007: Examination of kinetic effects on electron transport in a hohlraum* Michael Marinak, Robert Kingham, Chris Ridgers, Mark Sherlock, Mehul Patel Integrated simulations of indirect drive targets performed with HYDRA can employ an extended version of the SNB$^{\mathrm{1}}$ model to treat electron preheat and thermal flux inhibition. Even with these effects included some adjustments are still required to match hohlraum drive. This motivates an assessment of the extent to which approximations in the nonlocal model change the electron transport compared to fully kinetic models. We have enabled HYDRA to operate in conjunction with electron VlasovFokkerPlanck (VFP) codes to compare this model with results obtained using electron transport. The K2 electron VFP code solves the timedependent VFP equations by expanding the distribution function in spherical harmonics and retaining only the first two expansion coefficients (f$_{\mathrm{0}}$ and f$_{\mathrm{1}})$. The IMPACT$^{\mathrm{2}}$ code employs a similar approach to solve timedependent VFP equations. We present results from calculations of a 1D gold hohlraum that show significant effects on the radiation drive spectrum compared to the reference model. *This work was performed under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract No. DEAC5207NA27344 $^{\mathrm{1\thinspace }}$G.P. Schurtz, P.D. Nicolai, and M. Busquet, Phys. Plasmas \textbf{7}, 4238 (2000) $^{\mathrm{2}}$ R. J. Kingham and A. R. Bell, J. Comput. Phys. \textbf{194}, 1 (2004) [Preview Abstract] 

CP17.00008: An Important Measure for NIF Ignition Capsules Baolian Cheng The performance of fusion capsules on the National Ignition Facility (NIF) is strongly affected by the physical properties of the hot deuteriumtritium fuel, such as the mass, areal density, pressure and neutron yield of the hot spot at the stagnation time. All of these critical quantities depend on one measured quantity, which is the ratio of the specific peak implosion energy to the specific internal energy of the hot spot. This unique physical quantity not only could measure the incremental progress of the ignition capsules towards ignition but also measures the efficiency of converting the implosion kinetic energy of the pusher shell into the internal energy of the hot fuel in each capsule. Analysis to existing NIF shots to date are performed. Distances to ignition from various ignition designs are quantified. Results provide a new look to the NIF experiments from another dimension that helps to improve future designs (LAUR 2024613). [Preview Abstract] 

CP17.00009: Summary of TwoShock Campaign results using 1D and 2D simulations Paul Bradley, Brain Haines The 2shock campaign$^2$ was a series of NIF capsule implosions that used a 675 micron outer radius capsule with a roughly 175 micron thick 1{\%} Sidoped ablator. These capsules were used to test several hypotheses for yield degradation, including shock convergence mistiming, increased surface roughness, and increases to the convergence ratio (initial to final inner radius ratio). We use the xRAGE Eulerian AdaptiveMeshRefinement computer code to model these implosions in 1D (using a turbulent mix model) and in 2D (no mix model). We find that in our 2D simulations, we do not require a mix model to match the data, as the fill tube, glue spot and surface roughness are enough. We start by comparing our results to DD, DT, and TT yields, along with the DT/TT ratio, burn weighted DT Tion value and burn width. We match most results for the gas filled capsules within the error bars. Many capsules have a separated reactant consisting of a 3 micron innermost CD layer surrounding an HT gas fill, where the DT yield is a mix diagnostic. We match the data where the convergence ratio is about 13; we underpredict the yield in 2D for convergence ratios of 16 to 20. $^2$G.A. Kyrala et al. Phys. Plasmas, 25, 102702 (2018). [Preview Abstract] 

CP17.00010: VisRad, 3D Target Design and Radiation Simulation Code James Sebald, Joseph MacFarlane, Igor Golovkin The 3D view factor code VISRAD is widely used in designing HEDP experiments at major laser and pulsedpower facilities, including NIF, OMEGA, OMEGAEP, ORION, LMJ, Z, and PLX. It simulates target designs by generating a 3D grid of surface elements, utilizing a variety of 3D primitives and surface removal algorithms, and can be used to compute the radiation flux throughout the surface element grid by computing elementtoelement view factors and solving power balance equations. Target setup and beam pointing are facilitated by allowing users to specify positions and angular orientations using a variety of coordinates systems ($e.g.$, that of any laser beam, target component, or diagnostic port). Analytic modeling for laser beam spatial profiles for OMEGA DPPs and NIF CPPs is used to compute laser intensity profiles throughout the grid of surface elements. We will discuss recent improvements to the software package and plans for future developments. [Preview Abstract] 
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