Bulletin of the American Physical Society
63rd Annual Meeting of the APS Division of Plasma Physics
Volume 66, Number 13
Monday–Friday, November 8–12, 2021; Pittsburgh, PA
Session CO03: HED: Hydrodynamics and Magnetohydrodynamics IIOn Demand
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Chair: Fernando Garcia-Rubio, University of Rochester Room: Rooms 302-303 |
Monday, November 8, 2021 2:00PM - 2:12PM |
CO03.00001: Drive Asymmetry in Directly-Driven Cylindrical Implosion Experiments at the National Ignition Facility Joshua P Sauppe, Mark J Schmitt, Sasi Palaniyappan, Kirk A Flippo, Lynn Kot, Rebecca Roycroft, Alex Strickland, Thomas Day, John L Kline We present results from recent directly-driven cylindrical implosion experiments fielded at the National Ignition Facility (NIF) that demonstrate a clear m=8 drive asymmetry. Cylinders are used to measure hydrodynamic instability growth in regimes relevant to inertial confinement fusion implosions, as they include the effects of convergence while retaining direct diagnostic access. The drive asymmetry is observed for both 3 mm and 4 mm outer diameter cylinders, and it is most readily apparent in nominally smooth targets that lack any machined perturbation. The m=8 asymmetry appears with the same phase for three different laser drive configurations, despite vastly different initial intensity patterns, and we conjecture that the asymmetry arises from differential absorption of the 44 degree beams (relative to the cylinder axis) and the 50 degree beams that are used to drive the cylinder. Radiation-hydrodynamics simulations in 2D can reproduce the observed pattern using an ad hoc variation of the laser power in the different cones, but 3D laser-driven simulations are needed to accurately model the drive asymmetry. Several alternative laser drive configurations are proposed for future experiments, and preliminary simulation predictions under these conditions are presented. |
Monday, November 8, 2021 2:12PM - 2:24PM |
CO03.00002: Acceleration Phase Rayleigh-Taylor Instability in Planned Double Cylinder Experiments for OMEGA and NIF Rebecca Roycroft, Joshua P Sauppe, Paul A Bradley, Sasi Palaniyappan Cylindrical implosions are used to study hydrodynamic instability growth for ICF applications, as the cylindrical geometry allows for easier diagnostic access while retaining convergence effects. We are working on a double cylinder experimental platform as an analogue to the double shell ICF capsule in order to study hydrodynamic instability growth on the inner shell. We present designs for double cylinder targets that will be fielded at the OMEGA laser facility and the National Ignition Facility. Our design work is done with xRAGE [Comput. Sci. & Disc. 1, 015005] radiation-hydrodynamics simulations, considering the axial uniformity of the implosion in multiple laser drive configurations, the effects of radiation diffusion, and the feasibility of measuring the instability growth with pre-seeded single mode perturbations. We evaluate the designs for visibility of instability growth, finding for the OMEGA design that spikes on the tamper/inner cylinder interface grow to a maximum of 50-70μm in length. Axial bowing extent is at most 4μm radially, and with a diagnostic resolution of ~10μm, we expect the spikes to be visible. Preheat due to radiation diffusion reduces the length of the spikes by up to 30μm; however, synthetic radiographs show that the spikes should still be visible. |
Monday, November 8, 2021 2:24PM - 2:36PM |
CO03.00003: Uncertainty Quantification for the Sensitivity Analysis and Prediction Error of 1D Radiation-Hydrodynamics Simulations of Cylindrical Implosions William Gammel, Joshua P Sauppe, Samy Missoum, Bharath Pidaparthi Cylindrical targets are used to study instability growth in regimes relevant to inertial confinement fusion implosions, as they retain the effects of convergence while allowing for direct diagnostic access. Design parameters for experiments on the National Ignition Facility are informed by one-dimensional (1D) and two-dimensional (2D) radiation-hydrodynamics simulations, and these cylindrical implosions are most sensitive to parameters such as target radius, fill composition, and laser pulse shape. Even in 1D, the parameter space responsible for dictating the behavior of various implosion performance metrics is vast, and it can be difficult to ascertain which model parameters, or combinations thereof, have the most influence on these metrics. Additionally, uncertainty introduced via the addition of ad hoc parameters which are used as a proxy for complex underlying physics can result in mismatches between model results and experimental data. This talk applies model calibration techniques based on fidelity mapping to 1D simulations in order to examine the sensitivity of our model to such parameters, as well as identify regions of space where the error between model predictions and experimental results is relatively low. |
Monday, November 8, 2021 2:36PM - 2:48PM |
CO03.00004: Cylindrical compressions with embedded B-field to characterize strongly magnetized hot dense plasmas. Mathieu Bailly-Grandvaux, Chris Walsh, Ricardo Florido, Christopher McGuffey, Joao J Santos, Gabriel Peréz-Callejo, Francisco Suzuki-Vidal, Christos Vlachos, Marco A Gigosos, Roberto C Mancini, Farhat N Beg The use of external magnetic fields in ICF has been identified as a promising way to assist ignition. For this relatively new area of sustained research, the magnetic field transport during compression and related magnetized plasma dynamics must be studied. We propose a platform for the OMEGA-60 laser facility to study MHD effects in cylindrical implosions at regimes of large magnetic pressure and magnetization. Cylindrical targets are filled with Ar-doped D2 gas and are symmetrically imploded using a 36-beam, 15 kJ, 1.5 ns laser drive. To investigate the effects of magnetization, implosions are characterized using X-ray framed imaging and Ar K-shell line-emission spectroscopy. 2-D simulations using the MHD code GORGON predict that a seed B-field of 30 T is compressed to ~30 kT. As a result, the characteristic conditions of the compressed core and the emitted Ar spectrum are modified. We present results of implosions with a seed B-field induced in laser-driven coils and MIFEDS. According to proton probing, the seed B-field generated with laser-driven coils was <10 T, likely due to the large inductance of the coils. Carrying out such magnetized implosion experiments will advance modeling of B-field compression and diffusion, and benchmark atomic kinetics and line shape calculations in magnetized plasmas relevant to complex ICF-related experiments with embedded B-fields. |
Monday, November 8, 2021 2:48PM - 3:00PM |
CO03.00005: Interaction of radiation and mix at a hohlraum wall Kevin P Driver, Matthew P Hill, Peter Graham, Warren J Garbett, Steven H Langer, Shon T Prisbrey In laser-driven hohlraums, mix occurs at the interior wall as it radiates and ablates into foam liners and fill gas. A campaign on the National Ignition Facility, called the Hohlraum Wall Heating campaign, began taking data in 2020 with a platform designed to investigate the interaction of radiation and mix at hohlraum-relevant temperatures and optical depths. The goals of the campaign are two-fold: (1) quantify the effect of mix on radiation transport and (2) measure the mix profile variation with temperature. Initial shots have focused on platform qualification and taking data to optimize simultaneous burn-through and radiography configurations needed to tease out the interdependencies of radiation and mix. In this talk, we will discuss the modeling efforts used to design the platform and compare initial data with post-shot simulations as part of code-validation efforts. |
Monday, November 8, 2021 3:00PM - 3:12PM |
CO03.00006: Using self-similar solutions to understand magnetised transport in high-energy-density plasmas relevant to magneto-inertial fusion Griffin Farrow, Jeremy P Chittenden, Grigory Kagan The transport of magnetic fields and thermal energy are important processes in magneto-inertial fusion schemes. Accurate modelling of these effects is crucial for the success of future experiments. To this end, we develop semi-analytic self-similar solutions to subsonic magnetised transport. We solve the extended MHD equations in 1D planar geometry under assumption of pressure balance, for arbitrary plasma beta, using a Newton-Raphson steered shooting code. Agreement between the self-similar solutions and simulations using the MHD code Chimera is good, validating the use of these semi-analytic solutions as flexible test problems for extended MHD algorithms. We then use these self-similar solutions to assess the relative roles of the Nernst and resistive diffusion effects in magnetic field evolution. We find that the Ettingshausen and Ohmic heating terms can be significant even in an order unity beta plasma and dominate in low beta regimes, but their effect depends strongly on the plasma profiles. We also discuss the breakdown of these self-similar solutions as the Ohmic heating drives strong heating of the electrons, finding that the Ettingshausen effect prevents electron-ion temperature separation in this low beta limit. This suggests that the exclusion of the Ettingshausen effect may cause resistive MHD simulations to overestimate the electron temperature at a plasma-vacuum interface, such as at the edge of a z pinch. |
Monday, November 8, 2021 3:12PM - 3:24PM Not Participating |
CO03.00007: Measurement of magnetic cavitation driven by heat flow in a plasma Christopher Arran, Nigel C Woolsey, Christopher P Ridgers Under extreme conditions, heat flow and magnetic fields in plasmas are strongly coupled. However, the Nernst effect, where heat flow drives advection of the magnetic fields, is seldomly described and is often neglected from magneto-hydrodynamic models. Using laser-driven proton radiography, we demonstrate that this heat-flow-driven advection in fact dominates changes to the magnetic field in underdense plasmas on the nanosecond timescale. Through laser-heating of a gas within an applied magnetic field, we measure expulsion of the magnetic field from the hottest regions of the plasma. We reconstruct the magnetic field map and find almost complete cavitation of an applied magnetic field, with the field advected by heat flow at velocities around (6±2)x105 m/s, in advance of the hydrodynamic expansion. Furthermore, we show how changes in the magnetic field can be used as a proxy for heat flow and use the measured advection to explore non-local effects in the heat transport. |
Monday, November 8, 2021 3:24PM - 3:36PM |
CO03.00008: Measuring magnetic flux suppression in high-power laser-plasma interactions Louise Willingale, Paul T Campbell, Chris Walsh, Brandon K Russell, Gennady Fiksel, Alexander G Thomas, Karl M Krushelnick, Jeremy P Chittenden, Aidan C Crilly, Lan Gao, Igor Igumenshchev, Philip M Nilson Experiments performed with the OMEGA EP laser are used to measure Biermann battery magnetic field generation driven by high power laser-solid interactions. Proton deflectometry observes changes to the strength, spatial profile, and temporal dynamics of the self-generated magnetic fields. By varying the target material or laser intensity, measurements of the magnetic flux during the interaction are used to help validate extended magnetohydrodynamic (MHD) simulations using the code GORGON. Comparison of the experimental and simulation results suggest that kinetic effects cause suppression of the Biermann battery mechanism in laser-plasma interactions. Counter to a standard MHD understanding, the experiments generated more magnetic flux as the target atomic number is increased. These results are relevant to both direct and indirect-drive inertial confinement fusion. |
Monday, November 8, 2021 3:36PM - 3:48PM |
CO03.00009: Measurements of Diamagnetic Cavity Formation and Collapse using Proton Radiography in HED Plasmas Sophia Malko, Derek B Schaeffer, William R Fox, Courtney L Johnson, Gennady Fiksel, Amitava Bhattacharjee, Anatoly Spitkovsky, Patrick F Knapp, Andrea Ciardi, Jonathan R Davies The interaction of laser-produced high-energy-density (HED) plasma with a magnetic field plays a key role in magnetized fusion schemes and laboratory astrophysics experiments such as magnetic reconnection and magnetized collisionless shocks. |
Monday, November 8, 2021 3:48PM - 4:00PM |
CO03.00010: Spectroscopic diagnosis of core conditions in highly magnetized cylindrical implosions Ricardo Florido, Marco A Gigosos, Chris Walsh, Mathieu Bailly-Grandvaux, Farhat N Beg, Chris McGuffey, Roberto C Mancini, Gabriel Perez Callejo, Francisco Suzuki-Vidal, Christos Vlachos, Joao J Santos We discuss the application of time-resolved Ar K-shell spectroscopy to diagnose the core conditions in highly magnetized cylindrical implosions. An external seed B-field of ∽30 T is applied to Ar-doped, D2-filled cylindrical targets, which are directly-driven by using 40 OMEGA laser-beams. The plasma dynamics are numerically investigated in 2-D with the MHD code GORGON, proving that an extreme magnetization regime is attainable. Post-processing the MHD output by means of detailed Non-LTE atomic kinetics and Stark-broadened line profiles permits to obtain synthetic spectra that approximate the expected observations. The impact of the B-field produces significant variations on the core conditions throughout the implosion collapse which leads to distinctive spectral features measurable by available streaked spectrometers. Difficulties to extract representative values of core conditons due to the large spatial gradients arising in the magnetized scenario are discussed. By assuming the magnetic field is frozen into the plasma motion, the spectroscopic analysis is used to estimate a collection of metrics about the relative importance of magnetization processes in the compressed core. A preliminary analysis of recently recorded Ar K-shell spectra will be also presented. |
Monday, November 8, 2021 4:00PM - 4:12PM |
CO03.00011: Heat Transport Effects in Magnetised Laser-Plasmas with Large Temperature Gradients Adam Dearling, Christopher Arran, Christopher P Ridgers, Nigel C Woolsey Key to accurately predicting heat-flow in many laser-plasma systems is understanding the effect of non-local transport, where the heat-flow at a given point in the plasma is no longer determined solely by local conditions. For laser-plasma systems non-local transport is often most significant at the heat-front, where the mean-free-path of electrons can be long compared to the temperature length scale. Incorporating non-local effects on heat-flow in predictive models is challenging though, often requiring extended fluid or kinetic modelling. Moreover, magnetic fields in plasmas modify and restrict heat transport. Here we describe how a magnetic field can limit the emergence of non-local transport effects. Transitioning from the weakly magnetised regime where the gyrofrequency is smaller than the collision frequency and the Hall parameter is small, to a strongly magnetised case with a Hall parameter exceeding unity, the magnetic field acts to reduce the distance travelled by heat carriers. Here, the decreasing collisionality counter-intuitively leads to more local transport. This demonstrates that fluid models of magnetised plasmas can be valid even in a regime where the thermal mean-free-path of the electrons exceeds the temperature length scale. |
Monday, November 8, 2021 4:12PM - 4:24PM Not Participating |
CO03.00012: Laser scaling for generation of megatesla magnetic fields by microtube implosions Masakatsu Murakami, Didar Shokov, Javier Honrubia Microtube implosions are a novel scheme to generate ultrahigh magnetic fields on the megatesla order. These implosions are driven by ultraintense and ultrashort laser pulses. Using two- and three-dimensional particle simulations where megatesla-order magnetic fields can be achieved, we demonstrate scaling and criteria in terms of laser parameters such as laser intensity and laser energy to facilitate practical experiments toward the realization of extreme physical conditions, which have yet to be realized in laboratories. Microtube implosions should provide a new platform for studies in fundamental and applied physics relevant to ultrahigh magnetic fields. |
Monday, November 8, 2021 4:24PM - 4:36PM Not Participating |
CO03.00013: Effects of Resistivity and Extended MHD on HED and ICF Experiment Designs Kirk A Flippo, Shengtai Li, Yingchao Lu, Alexander Rasmus, Hui Li, James D Sadler, Jacopo Simoni, Jerome Daligault, Codie Y Fiedler Kawaguchi, Daniel H Barnak, Kwyntero Kelso Ideal MHD is known to insufficient to model most laser-driven laboratory experiments, and especially HED and laboratory astrophysics. But using extended MHD (exMHD) can be computationally expensive, and hard to implement in certain computational frameworks, thus it is important to know which terms are important for designing an HED experiment to study hydrodynamic instabilities, and if resistive MHD is sufficient, or if more terms (e.g. Biermann, Hall, Nernst) are need for more accurate modeling and design. Here we present design for an experiment with a series of simulations to understand the role of resistivity on the modeling and design of a HED Rayleigh-Taylor instability growth experiment under currently achievable laboratory conditions, and implications for other HED and ICF experiments with self-generated and applied fields. |
Monday, November 8, 2021 4:36PM - 4:48PM Not Participating |
CO03.00014: Computational investigation of x-ray impulse generation in solid materials Griffin S Cearley, Peter Porazik, Laura Berzak Hopkins, Steve J Moon, Israel Lopez, Eric Johnsen The generation of impulse in solid materials by x-ray absorption is difficult to model and relevant to many applications in high-energy-density physics. In these systems, x-rays are deposited within the material to a depth dictated by the material's opacity. This heated surface layer may blow off, imparting impulse to the remaining material. The thermal and mechanical dynamics of such systems are complex, and in general require full-physics simulation with appropriate models to account for all blow-off mechanisms ( eg. spallation, jetting, plasma ablation) that contribute to the impulse of the bulk material. Existing analytical models require closure of the final energy distribution of the blow-off material, which is not known a priori. |
Monday, November 8, 2021 4:48PM - 5:00PM |
CO03.00015: Direct laser impulse effects on titanium Eli Feinberg, Griffin S Cearley, Eric Johnsen, Carolyn C Kuranz, Patrick Poole, Peter Porazik, Steve J Moon, Brent E Blue, Laura Berzak Hopkins Direct Laser Impulse (DLI) is an experimental platform in which a high-power optical laser strikes a tamper material to emulate the impulse and shock generated by x-ray deposition in metal. Here, we present analysis of DLI experiments on titanium alloys. Simple, flat titanium targets adhered to a tamper were subjected to a direct laser impulse on the Orion Laser at the UK’s Atomic Weapons Establishment. In this analysis, we will compare the response of titanium in these DLI experiments to experiments on the National Ignition Facility (NIF) in which x-ray photons directly interacted with metal to generate a thermo-mechanical shock. Such comparisons will inform the design of future NIF x-ray experiments as well as experiments on a new NIF DLI capability coming online in 2022. |
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