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 VP12: Poster Session: HED: Laboratory Astrophysics (2:00pm - 5:00pm)On Demand
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VP12.00001: High Repetition Rate Volumetric Measurements of Spontaneously Generated Magnetic Fields in Laser Produced Plasmas Jessica Pilgram, Carmen Constantin, Peter Heuer, Robert Dorst, Derek Schaeffer, Christoph Niemann The Biermann Battery effect is the spontaneous generation of magnetic fields due to misaligned temperature and density gradients in a plasma. This effect is known to spontaneously generate magnetic fields in many astrophysical phenomena and is theorized to be an important source of the primordial magnetic fields of the universe. Biermann Battery generated fields can be replicated and studied using high energy density laboratory plasmas where this effect occurs in the corona of an expanding laser produced plasma (LPP). In this poster we present a high repetition rate (HRR) experiment examining the three-dimensional spatial structure of these Biermann generated fields and their dependence on laser energy. A 10 J HRR laser is incident on a high-density polyethylene (C$_{\mathrm{2}}$H$_{\mathrm{4}})$ target creating a collisional LPP. The spatial structure of the resulting Biermann Battery fields is measured with a magnetic flux probe. Volumetric datasets containing thousands of points are recorded by moving the probe to various spatial positions between laser shots. Preliminary measurements show azimuthally symmetric magnetic fields with peak magnitudes of up to 160 G in our closest transverse planes which are a distance of 7 mm from the target surface. [Preview Abstract] |
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VP12.00002: Time Resolved Spectroscopic Measurements of Electron Temperature and Ion Density in a High Repetition Rate Experiment Robert Dorst, Peter Heuer, Derek Schaeffer, Jessica Pilgram, Carmen Constantin, Christoph Niemann Many laboratory plasmas of interest are transient (\textless 1 ms) and tenuous (\textless 10$^{\mathrm{15}}$ cm$^{\mathrm{-3}})$ in nature, but measuring time-resolved temperatures and densities in this regime is challenging. The intensity ratios of spectral lines corresponding to successive ionization states are highly dependent on electron temperature, and Stark broadening is a well-established and reliable technique for determining density. However, these techniques are generally performed on steady-state plasmas, or time integrated to the point where valuable information is lost. We present a comparison between high-temporal resolution (\textasciitilde 10 ns) spectroscopic data and a collisional-radiative model in order to characterize the evolution of the temperature and density of carbon ablated plasma in a regime where Thomson scattering and Langmuir probes prove challenging. A high repetition rate laser allows for individual time resolved spectral lines to be assembled into a highly resolved (\textasciitilde 2 {\AA}) composite spectrum for analysis. [Preview Abstract] |
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VP12.00003: Investigation of Magnetic Field Topology in Counter-Propagating Flows from Proton Fluence Data S. Ghosh, R. Jonnalagdda, M.J.-E. Manuel, C.M. Huntington, M. Adams, A. Higginson, B.A. Remington, J.S. Ross, D.D. Ryutov, Y. Sakawa, H. Sio, G.F. Swadling, S.C. Wilks, F.N. Beg, H.-S. Park Collisionless shocks are present in many astrophysical systems. These shocks are generated experimentally at OMEGA laser facility to study Weibel instabilities. The proton probing technique has been used in these experiments to probe the self-generated magnetic fields in the plasma interaction region. We are using the numerical code to assess the B-field strength from the proton flux image data. In particular, we will focus on using the perpendicular deflection field function to calculate path integrated magnetic field. We will also discuss on reconstructing the proton flux image from the path integrated magnetic field. [Preview Abstract] |
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VP12.00004: On the Current Filamentation Instability in counterpropagating plasma setups Cinzia Chiappetta, MariaElena Innocenti, Nitin Shukla, Elisabetta Boella The Current Filamentation Instability (CFI) is currently being studied in the context of both astrophysical and laboratory settings to explain the generation of the magnetic field in unmagnetized plasmas [1]. However, the long-term development of the instability is still poorly understood. In this work, we investigate the evolution of the CFI following the interpenetration of sub-relativistic plasma slabs of finite length, similar to those produced in the laboratory. By resorting to multi-dimensional Particle-In-Cell simulations performed with the semi-implicit energy conserving code ECsim [2], we explore the spatio-temporal development of the instability. Taking full advantage of the implicit time discretization, we are able to follow the plasma dynamics on ion timescales. This allows us to probe the merging process of the magnetic field filaments, the transition towards smaller wavenumbers, and the saturation mechanism. Finally, we analyze the role of the instability globally slowing down the plasma clouds. [1] N. Shukla et al, Phys Rev Research 2, 023129 (2020). C. M. Huntington et al, Nat Phys 11, 173 (2015). W. Fox et al, Phys Rev Lett 111, 225002 (2013). L. O. Silva et al Astrophys J Lett 596, L121G (2003). [2] G. Lapenta et al, J Plasma Phys 83, 705830205 (2017). [Preview Abstract] |
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VP12.00005: Particle-in-cell simulations of laser-driven, ion-scale magnetospheres in laboratory plasmas F. D. Cruz, F. Cruz, L.O. Silva, D. B. Schaeffer, A. Bhattacharjee, R. S. Dorst, P. Heuer, C. G. Constantin, P. Pribyl, C. Niemann Ion-scale magnetospheres have been observed around comets, weakly-magnetized asteroids, and localized regions on the Moon. These mini-magnetospheres provide a unique environment to study kinetic-scale plasma physics, in particular in the collisionless regime. In this work, we present collisionless particle-in-cell (PIC) simulations of ion-scale magnetospheres that reproduce recent laboratory experiments performed on the Large Plasma Device (LAPD) at UCLA. Utilizing high-repetition rate lasers to drive super-Alfv\'{e}nic plasma flows into a dipole magnetic field embedded in a uniform background magnetic field, these experiments examine the evolution of local and global magnetosphere structure for a range of dipole and upstream parameters. PIC simulations are employed to interpret highly-resolved, volumetric experimental datasets, and used to determine the magnetospheric structure, magnetopause location and kinetic-scale structures of the plasma current distribution. Single and multiple ion species simulations are compared to investigate the role of heavy ion debris from the laser target in the interaction. [Preview Abstract] |
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VP12.00006: Shock formation in pulsed-power driven counter-propagating jets F. Suzuki-Vidal, C. Seyler, S.N. Bland, L.G. Suttle, S.V. Lebedev We present experiments and numerical simulations looking at the formation of shocks from the collision of two counter-propagating supersonic jets. The jets were driven on the MAGPIE pulsed-power facility which delivered a $\sim$900 kA, 300 ns zero to peak current through two aluminum radial foils connected in series and separated by 30 mm. The jets have a tip velocity of $\sim$100 km/s and are surrounded by a low-density plasma ‘wind’ that acts as a mass source and supports advected toroidal magnetic surrounding the jet. The collision between the two jets leads to the formation of a bow shock surrounded by an extended standing shock. These experimental results [1] are investigated with the Extended-MHD code PERSEUS, which shows that the opposite direction of the current through each foil leads to different plasma dynamics that form the shocks through a combination of hydrodynamic and magnetized plasma flows. [1] F. Suzuki-Vidal, S.V. Lebedev, A. Ciardi, L.A. Pickworth, R. Rodriguez, J.M. Gil, G. Espinosa, P. Hartigan, G.F. Swadling, J. Skidmore, G.N. Hall, M. Bennett, S.N. Bland, G. Burdiak, P. de Grouchy, J. Music, L. Suttle, E. Hansen, and A. Frank, ApJ 815:96 (2015). [Preview Abstract] |
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VP12.00007: A Theoretical Approach for Shock Strengthening in High-Energy-Density Laser Compression Experiments Michael Wadas, Griffin Cearley, Eric Johnsen, Marius Millot The design of shock compression experiments in high-energy-density systems typically requires shocks to pass through different materials to achieve the desired state of compression. In this study, a theoretical approach for strengthening such shock waves is examined. A method based on characteristic analysis is used to semi-analytically solve the problem of a shock passing through a region of non-uniform density to increase the strength of the shock initially transmitted into the experimental target. It is found that incorporating multiple intermediate density steps between two materials can increase the strength of the transmitted wave. Furthermore, it is shown that an exponential discretization of intermediate density steps is the most efficient distribution for shock strengthening. The technique is applied to the design of laser-driven dynamic compression experiments, and the results of the analysis are verified via comparison to simulations performed with the HYADES hydrodynamics code. [Preview Abstract] |
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VP12.00008: Cloud Collapse Laboratory Astrophysical Experiment Compared to CRASH Simulations Matthew Trantham, Robert VanDervort, Paul Keiter, Carolyn Kuranz Recent laboratory experiments explored radiation hydrodynamics relevant to irradiated molecular clouds, by using X-rays from a laser-driven gold foil to irradiate a foam sphere. We used CRASH, an Eulerian code developed at the U. of Michigan, which includes block adaptive mesh refinement, multigroup diffusive radiation transport, and electron heat conduction. We present results from a series of simulations aimed at understanding the experimental results. In order to compare our simulations to experimental results we focus on features that are clearly visible in the radiographic experimental images. The position of the shock traveling through the foam sphere and the position of bow shock are both easily seen and tracked in the radiographic images. This study will show the ability of CRASH code to reproduce this experiment and aid in the analysis of the features we observe in the experimental results. This work is funded by the U.S. Department of Energy NNSA Center of Excellence under cooperative agreement number DE-NA0003869 and the National Science Foundation through the Basic Plasma Science and Engineering program NSF 16-564, grant number 1707260. [Preview Abstract] |
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VP12.00009: Laboratory Generated Photoionization Fronts Relevant to Cosmology Michael Springstead, Heath LeFevre, Taisuke Nagayama, Guillaume Loisel, James Bailey, Sallee Klein, Roberto Mancini, Kyle Swanson, Don Winget, Bart Dunlap, Joshua Davis, William Gray, Carolyn Kuranz, Paul Drake Photoionization Fronts (commonly referred to as Ionization Fronts or PI fronts) are a type of radiation-driven heat front that dictate important physics in reionization era of the early universe. The first galaxies of the reionization era merged to form minihalos. Subsequently, these minihalos emitted ionizing radiation to the surrounding gas clouds, which generated PI fronts. The asymmetric propagation and attenuation of a PI front within a gas cloud is an active area of study in the early universe cosmology. In the laboratory setting, the Z Astrophysical Plasma Properties (ZAPP) platform on Sandia’s Z-Machine facility is capable of generating an intense radiation source to drive a PI front through a 0.75atm nitrogen gas cell. To better understand upcoming ZAPP experiments on Sandia’s Z-Machine, this work presents an initial experimental design, accompanied by HELIOS radiation-hydrodynamic simulations, and PrismSPECT atomic kinetics calculations. [Preview Abstract] |
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VP12.00010: Observation of Photoionization Fronts in Laboratory Experiments Kwyntero Kelso, Heath LeFevre, Sallee Klein, Paul Keiter, William Gray, Joshua Davis, R Paul Drake, Carolyn Kuranz Photoionization fronts are meaningful drivers of transformation for astrophysical phenomena and remain difficult to produce in laboratory experiments. As the universe evolved, the first dense structures were galaxies made mostly of dark matter which lead to sustained ionizing radiation, starting the reionization epoch. When minihalos cooled atomically, populations of stars emerged creating photoionization fronts forming these galaxies. Experiments at the OMEGA Laser Facility can create relevant photoionization conditions. One can generate an X-ray source with radiation temperature of about 90eV that irradiates a nitrogen medium held at high pressures. A laser irradiated gold foil generates an X-ray source which propagate deeper into a nitrogen gas cell. Measuring the temperature, density, and ionization state of the heated region yields ratios for the calculation of atomic rate coefficients. [Preview Abstract] |
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VP12.00011: Characterization of a Long Duration X-ray Source for Laboratory Photoionized Plasmas in Steady-State Ryan Schoenfeld, Roberto Mancini, Dan Mayes, Kyle Carpenter, Jeffrey Rowland, Robert Heeter, Duane Liedahl, Sean Regan Long duration, i.e. tens of ns, broadband x-ray sources are important for driving photoionized plasma experiments in steady-state relevant to astrophysics. In a series of experiments performed at the OMEGA EP laser, we have used the Gatling-Gun x-ray source to produce a 30ns x-ray drive with a 90-eV radiation temperature. The Gatling-Gun source consists of three TPX-foam filled Cu-hohlraums. By driving each hohlraum sequentially with a 10ns square pulsed 4.4kJ UV laser beam we have achieved the 30ns-duration broadband x-ray source$^{\mathrm{1}}$. A long duration x-ray source is paramount to produce laboratory photoionized plasmas in steady-state. We present measurements of the performance of the Gatling-Gun x-ray source recorded in multiple experiment series with the VISAR, SOP and 4$\omega $-probe diagnostics as well as a grating spectrometer in order to characterize the energy content and spectral distribution of the Gatling-Gun x-ray flux, respectively. We also discuss radiation-hydrodynamic and view factor simulations to interpret the data, and model a photoionzed plasma experiment produced by the x-ray flux. $^{\mathrm{1}}$D. Martinez, 2017 Annual OLUG Workshop. [Preview Abstract] |
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VP12.00012: Laser Interferometry and X-ray Absorption Spectroscopy of Photoionized Neon Gas Jets using the 1MA Zebra Generator Kyle Swanson, Vladimir Ivanov, Roberto Mancini, Daniel Mayes, Enac Gallardo-Diaz, Ryan Schoenfeld, Noah Huerta Laboratory produced photoionized plasmas provide a method to systematically explore plasma conditions relevant to astrophysical phenomena. Neon and argon, mm-scale supersonic, gas jets have been used for photoionization experiments on Zebra, a university scale, 1MA and 0.5 TW, pulsed-power generator. A broadband X-ray flux of 15-20kJ is emitted from the implosion of a gold Z-pinch wire-array. The 25-30ns X-ray pulse photoionizes the gas jet as well as backlights it for x-ray absorption spectroscopy. Vertical and side-on laser diagnostics covering 1064, 532, 266, and 213nm, are employed to diagnose the neutral and photoionized jet via air-wedge interferometry, Mach-Zehnder interferometry, and shadowgraphy. A program has been developed to analyze Mach-Zehnder and air-wedge interferometry data allowing for accurate analysis. Interferometry and x-ray absorption spectroscopy measure electron areal densities in the range 1-3.5E18 cm-2. Volumetric electron density measured from laser interferometry is in the range of 1-4E19 cm-3. Average charge state measurements calculated from the X-ray absorption spectroscopy analysis and interferometry are 5.8 and 6.2, respectively. The absorption spectra indicate the photoionized neon plasma is mainly populated by B-, Be- and Li-like neon ions. [Preview Abstract] |
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VP12.00013: Sedov-Taylor-like blast waves as an in-situ measure of energy transport in laboratory experiments S. M. Finnegan, R. R. Peterson, T. J. Urbatsch, N. B. Meezan, J. R. Fein, D. J. Ampleford A principle mechanism for the formation and evolution of cosmic structures is the interaction of radiation and matter. Radiation propagating through the interstellar medium interacts with pre-existing obstructions, affecting the organization of interstellar shocks, leading to complex structures. Validating radiation transport models in the presence of obstructions is thus important to underwriting our understanding of such interactions. Here, we present the design of new experiments on the Z Pulsed Power Facility at Sandia National Laboratories in which the evolution and structure of Sedov-Taylor-like blast waves[1] are used as an in-situ measure[2] of the net radiative energy flow in the presence of obstructions. Through the use of opposing experiments, one serving as a fiducial for the net energy delivered, the relative energy flow in the presence of objects or through complex surfaces in the opposing experiment can be inferred. [1] G. I. Taylor, Proc. R. Soc. London, Ser. A 201, 159 (1949); L. I. Sedov, Prikl. Mat. Mekh. 10, 241, No. 2 (1946) [2] R. R. Peterson et al., Phys. Plasmas 13, 056901 (2006); Thomas E. Tierney et al., Rev. Sci. Instrum. 79, 10E919 (2008) [Preview Abstract] |
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VP12.00014: Testing Radiation Trapping Efficiency for Double Shell Inertial Confinement Fusion Targets John Kline, S. M. Finnegan, W. S Daughton, D. S. Montgomery We present experimental concepts for testing the efficiency of radiation ``trapping'' by high-Z materials for Inertial Confinement Fusion (ICF) capsules. ICF requires heating of the Deuterium-Tritium (DT) fuel by alpha particles released during fusion reactions at a rate higher than losses by heat conduction or radiation. A layer of high-Z material on the inner surface of a capsule next to the burning DT gas reduces radiation losses reducing the required gas temperature to exceed the self-heating threshold. It is hypothesized the radiation trapping efficiency for capsule implosions may be reduced by hydrodynamic instabilities affecting the shape of the high-Z layer. The distorted shape changes the efficiency of radiation trapping by increasing the surface area, thinning regions of the shell, and/or changing the radiation view factor. Assessing the efficiency of radiation trapping is critical for double shell capsule designs. We have developed experimental concepts to test the effects of the shape of high-Z materials on radiation trapping. The experimental designs and supporting simulations will be included in this presentation. [Preview Abstract] |
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VP12.00015: Kinetic Mix in Gas-filled Inverted Corona Fusion Experiments William Riedel, Nathan Meezan, Drew Higginson, Matthias Hohenberger, Mark Cappelli, Siegfried Glenzer In this work we investigate the effect of gas fill density on kinetic mixing and yield performance of laser-driven “inverted corona” fusion experiments. Inverted corona targets consist of a fuel layer lined along the interior surface of a hollow or gas-filled plastic hohlraum that is laser-ablated and expands inward towards the hohlraum center. Previous experiments have demonstrated the potential of such targets as neutron sources: DD yields over 10$^{10}$ have been achieved at OMEGA and DT yields at NIF are expected to exceed 10$^{14}$ using single-sided illumination and with low uniformity requirements. The plasma streams generated in these targets can be initially nearly collisionless as they converge and interpenetrate. Such interactions are difficult to model using standard magnetohydrodynamic (MHD) simulations, which assume high collisionality. Instead we model the system kinetically using the hybrid particle-in-cell (PIC) code Chicago to explore the importance of kinetic ion effects during stagnation. Simulations show that at low fill densities mixing can occur between the shell wall and the gas, modifying the plasma composition in the stagnation region and affecting yield performance. Predicted behavior is compared to OMEGA experimental results. [Preview Abstract] |
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