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 UO06: HED Measurements and Diagnostic TechniquesOn Demand
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Chair: Edward Marley, Lawrence Livermore Natl Lab Room: Rooms 310-311 |
Thursday, November 11, 2021 2:00PM - 2:12PM |
UO06.00001: Quantitative reconstruction of magnetic fields from proton radiography for colliding magnetized plasmas William R Fox, Derek B Schaeffer, Gennady Fiksel, Michael J Rosenberg, Archie Bott, Amitava Bhattacharjee, Hye-Sook Park, Daniel H Kalantar, Bruce Remington We present techniques for quantitative reconstruction of magnetic fields for magnetic reconnection experiments in laser-produced plasmas, including uncertainty analysis. Proton radiography uses a source of high-energy protons, which is sent through a plasma experiment, where the protons undergo deflections from the plasma electromagnetic fields, before being imaged on a detector. Recently, algorithms have been developed which allow inversion of the proton fluence images to obtain the plasma magnetic fields. We describe application of these techniques using data from the NIF Magnetic Reconnection experiments to obtain magnetic fields with quantitative error bars. We develop strategies for two key sources of uncertainty: the "zero" proton level or noise floor, which is especially important in the current sheet region; and, long-wavelength non-uniformities in the initial (undeflected) protons which manifest as spurious long-wavelength components of the magnetic fields. |
Thursday, November 11, 2021 2:12PM - 2:24PM |
UO06.00002: Evaluation of Direct Inversion of Proton Radiographs in the Context of Cylindrical Implosions Jonathan R Davies, Peter V Heuer Three publicly available direct inversion routines for proton radiography have been applied to laser-driven cylindrical implosions. The inversion routines used were a Monge-Ampere solver [1], a power-diagram method [2] and a probabilistic method that does not require a specified source profile [3]. The routines were first applied to four different test problems generated using specified fields in proton-tracing routines, three of them cylindrical and one spherical. Two of the test problems included field discontinuities that generate caustics, representative of ion fronts, shock fronts, and material interfaces. Only the power-diagram method successfully inverted test problems with caustics. The power-diagram method was then applied to proton radiographs obtained from cylindrical implosions on the OMEGA laser. In the experiments, proton trajectories intersected one another so there was not a unique solution for the path-integrated transverse Lorentz force on the protons. Nonetheless, the power-diagram method was able to find a solution that minimized proton deflection. Another solution was found by proton tracing using PlasmaPy [4] in fields from 3-D magneto-hydrodynamic simulations with the self-generated magnetic field reduced until adequate agreement was obtained. The direct inversion shows that the self-generated magnetic field could be even lower than indicated by the scaled-simulation results. [1] M. F. Kasim, Invert Shadowgraphy and Proton Radiography, Accessed 8 July 2021, https://github.com/mfkasim1/invert-shadowgraphy/tree/fast-inverse. [2] M. F. Kasim, Invert Shadowgraphy and Proton Radiography, Accessed 8 July 2021, https://github.com/mfkasim1/invert-shadowgraphy. [3] M. F. Kasim et al., Phys. Rev. E 100, 033208 (2019). [4] PlasmaPy Community et al., PlasmaPy (Version 0.6.0), Zenodo, Accessed 14 March 2021, http://doi.org/10.5281/zenodo.4602818. |
Thursday, November 11, 2021 2:24PM - 2:36PM |
UO06.00003: Characterization of NIF spectrometers at the new LLNL calibration station Maylis m Dozieres, Christine M Krauland, Jay Ayers, Nathaniel B Thompson, Jose E Castaneda, Tom McCarville, Joshua A Tabimina, Jeremy Huckins, Mai S Beach, Vern Rekow, Marilyn B Schneider A variety of research projects performed at the National Ignition Facility (NIF) utilize X-ray spectrometers. Characterizing and calibrating such instruments is of paramount importance in order to extract meaningful results from experiments. |
Thursday, November 11, 2021 2:36PM - 2:48PM |
UO06.00004: Broadband 2D Imaging Spectroscopic Diagnostic Showera H Haque, Radu Presura, Matthew S Wallace, Isiah Pohl, James Heinmiller, Patrick Lake, Ming Wu Two-dimensional imaging spectroscopic techniques are powerful tools in diagnosing HED plasmas for measuring spatial distributions of the plasma electron temperature and density. This has been achieved by using arrays of either spherically bent crystals with very high spectral and space resolution but with limited spectral coverage, or pinholes with flat Bragg reflectors with extended spectral coverage but lower resolution. Both methods work optimally for mm-size sources. Our instrument utilizes a convex crystal to produce a 2D image of the x-ray source in each spectral line over a broad spectral range. This instrument is compatible with cm-sized sources, making it an attractive diagnostic for z-pinches or fusion targets. We present measurement techniques established through ray-tracing and measurements made on tabletop x-ray sources to illustrate the spectral coverage and resolution capabilities of this instrument. |
Thursday, November 11, 2021 2:48PM - 3:00PM |
UO06.00005: Measurements of unequilibrated ions in hot, solid-density plasmas via x-ray lineshapes Brian F Kraus, Lan Gao, Kenneth W Hill, Manfred L Bitter, Philip C Efthimion, Thomas A Gomez, Adam F Moreau, Reed C Hollinger, Shoujun Wang, Huanyu Song, Jorge J Rocca, Roberto C Mancini Ion-electron equilibration drives plasma dynamics but is challenging to model at high densities. We present simultaneous measurements of electron and ion temperatures in solid-density, highly ionized Ti based on high-resolution x-ray Stark lineshapes; analysis implies that ions are significantly cooler than electrons. Foils with buried Ti layers are heated with a high-intensity laser with extreme temporal contrast. The localized Ti regions emit x-ray lineshapes that are both double-peaked and redshifted; these features, both hallmarks of Stark broadening, are differently affected by electron density and ion temperature. The data is interpreted with a new lineshape code that abandons the common assumption of dipole interactions for the electron broadening; comparing the data with this model strongly constrains both the ion temperature and the electron density. The electron temperature is independently constrained by x-ray line ratios. Measured plasmas are near solid density and support a significant temperature differential between hot electrons and cooler ions. The lack of equilibration suggests that either (1) the equilibration rate is substantially slower than the Spitzer equation predicts or (2) ion heat transport plays an important role in the system. |
Thursday, November 11, 2021 3:00PM - 3:12PM |
UO06.00006: Ultra-Compact X-ray Spectrometer (UCXS) for high repetition rate laser plasma experiments Ghassan Zeraouli, Derek Mariscal, Elizabeth S Grace, Graeme G Scott, Kelly Swanson, Raspberry A Simpson, Blagoje Z Djordjevic, Ryan Nedbailo, Huanyu Song, John Morrison, Jaebum Park, Reed C Hollinger, Shoujun Wang, Jorge J Rocca, Tammy Ma X-ray spectrometers have always been considered as indispensable tools for understanding plasma physics [1]. Indeed, they permit both reliable (direct and indirect) quantification and characterization of important physical properties such as absorbed laser energy, plasma temperature, plasma density etc... Thus, accessing such key parameters allows for a better description of laser plasma processes at extreme conditions. |
Thursday, November 11, 2021 3:12PM - 3:24PM |
UO06.00007: Characterization of the X-Ray Emission from Spherical Shells for X-Ray Absorption Fine Structure Spectroscopy Experiments on OMEGA-60 David A Chin, Philip M Nilson, John J Ruby, David T Bishel, Stephen Craxton, J. Ryan R Rygg, Gilbert Collins, Yuan Ping, Federica Coppari, Amy L Coleman X-ray absorption fine structure (XAFS) spectroscopy characterizes the local structure, chemistry and temperature of materials compressed to Earth’s core conditions. Thin plastic shells have previously been demonstrated to produce a bright, broadband, small, short-duration x-ray source, which is required to perform XAFS spectroscopy on the OMEGA laser at the Laboratory for Laser Energetics. By completing a detailed characterization of the x-ray emission from these thin plastic shells, we identified that ~25% of the x-ray emission around 7 keV occurs at a different time or larger radius than previously considered. Furthermore, we describe preliminary results introducing mid-Z metals into the implosion core, which indicate a significant increase in the total x-ray emission. The characterization of the x-ray emission and improved source brightness will allow for a more accurate and precise measurement of temperature in materials compressed to extreme conditions. |
Thursday, November 11, 2021 3:24PM - 3:36PM |
UO06.00008: Demonstration of geometric effects and resonant scattering in the X-Ray spectra of high-energy-density plasmas Gabriel Perez Callejo, Edward V Marley, Duane A Liedahl, Leonard C Jarrott, Gregory E Kemp, Robert F Heeter, Jim A Emig, Mark E Foord, Marilyn B Schneider, Steven J Rose, Justin S Wark In a plasma of sufficient size and density, photons can be absorbed and reemitted multiple times—what is known in astrophysics as resonant scattering. This process alters the ratio of optically thick to optically thin lines, depending on the plasma geometry and viewing angle. This has significant implications for the spectra observed in a number of astrophysical environments and in laser-produced plasmas, but has not previously been studied in a controlled laboratory setting. |
Thursday, November 11, 2021 3:36PM - 3:48PM |
UO06.00009: Characterization of laser heated gas jet targets for use as spectral emission sources Channprit Kaur, John M gjevre, Robert Fedosejevs Laser irradiated submillimeter gas puff targets are being developed as a source of narrow linewidth visible and UV emission lines, to be used for time resolved Zeeman splitting measurements of intense laser driven magnetic fields [1]. Accurate temporal and spatial characterization of the temperature and density profiles in these plasmas is important to optimize the spectral lines of interest. We have studied the generation of such low density plasmas both experimentally and with 2D hydrodynamic modelling. In the experiments, the emission plasma is produced using a few hundred millijoule, 10 ns, 1.06 um, laser pulse focussed into the exit plane of 500 um diameter nozzle, with backing pressures of 1 to 8 bar. The starting neutral gas density profile for the nozzle is measured using Rayleigh scattering and modeled using 2 D fluid simulations for carbon dioxide and nitrogen gasses. This density profile is incorporated into the hydrodynamics code to calculate the heating and ionization as a function of position with respect to the nozzle tip for different gas densities and laser energies. 1. Santos, J. J., et al. "Laser-driven platform for generation and characterization of strong quasi-static magnetic fields." New Journal of Physics 17.8 (2015): 083051. |
Thursday, November 11, 2021 3:48PM - 4:00PM |
UO06.00010: Modeling and Analysis of Background Oscillations on Hybrid-CMOS Ultrafast X-Ray Imagers Brian Hassard, Clement A Trosseille, Laura Robin Benedetti, Matthew S Dayton, Sabrina R Nagel Hybrid-CMOS (hCMOS) nanosecond X-Ray Imagers are a powerful time-resolved HED diagnostic due to their sensitivity to visible light, x-rays, and charged particles. However, significant pseudo-sinusoidal background oscillations have been observed in these sensors when exposed to an early incident excitation, a phenomenon that has been experimentally linked the sensor’s bond wire inductance. We analyze the oscillations both in the time domain and spatially to account for variations on the pixel level. Both theoretical techniques and analysis of experimental data have shown that the oscillations are a global sensor phenomenon. In addition, we effectively describe the oscillations with a physics-based model, giving further insight into the processes affecting them. This technique allows the hCMOS user to subtract out the oscillations from their measurements and improve accuracy. |
Thursday, November 11, 2021 4:00PM - 4:12PM Not Participating |
UO06.00011: New features and initial characterization of the hardened Single Line Of Sight camera Clement A Trosseille, Matthew S Dayton, Tae Chung, Cassadra E Durand, Anne M Garafalo, Jonathan D Hares, Eirc R Imhoff, Brad T Funsten, Ken Piston, Anthony Raymond, Adrianne C Welton, Arthur C Carpenter, Sabrina R Nagel A new generation of pulse dilation-based x-ray cameras has been developed at the National Ignition Facility. Building upon the lessons learned from a prototype version of the system, the hardened Single Line Of Sight camera will record up to height 30 ps images of Inertial Confinement Fusion implosion experiments, with improved image quality and under the most severe neutron yields. Following its commissioning on NIF, the camera will be used in conjunction with advanced x-ray optics such as the Crystal Backlighter Imager and the Imaging and Spectroscopy Snout. In preparation for its use on these shots, extensive performance tuning of the camera has been performed using a picosecond UV laser system. An overview of the tuning process and its challenges will be presented, and performance comparison with the prototype will be established, including temporal gate profiles, spatial instrument response function and space charge broadening-limited dynamic range. |
Thursday, November 11, 2021 4:12PM - 4:24PM |
UO06.00012: Development of Talbot-Lau interferometry for the study of laser generated HED plasmas at SACLA XFEL Bouffetier Victorien, Gabriel Perez Callejo, Maria Pia Valdivia Leiva, Gabriel Rigon, Dan Stutman, Tatiana Pikuz, Masato Ota, Luke Ceurvorst, Thibault GOUDAL, Bruno Albertazzi, Norimasa Ozaki, Kohei Miyanishi, Toshinori Yabuuchi, Keiichi Sueda, Tadashi Togashi, Shinsuke Fujioka, Hiroki Morita, Donaldi Mancelli, Joao J Santos, Tommaso Vinci, Paul Mabey, Michel Koenig, Alexis Casner Talbot interferometers are well known systems originally developed in synchrotron facilities for medical purposes. When set up in Moiré configuration, the advantage of these grating-based interferometers lies in their ability to furnish multiple sets of data in a single probing in a single shot. The on-detector mean illumination gives the X-ray attenuation and is equivalent to classical radiography. Additionally, the interference pattern provides a phase image of the probed medium thereby giving a direct measure of its refraction and electron density gradients. Finally, scattering can be captured through dark-field imaging. Recently, this technique has been adapted to investigate high-energy-density physics (HEDP) at laser facilities. This talk will present the continuation of this diagnostic’s development on XFEL facilities, examining the evolution of laser-generated dense plasmas obtained at the BL3, EH5 end station at SACLA XFEL. These plasmas were formed when a metallic foil was ablated by a 5 ns laser pulse with intensities of . The dynamics of this system were captured using a Talbot-Lau interferometer designed for use with the facility’s monochromatic X-ray probe to observe the evolution of the rear foil’s surface. The output interferograms were then post-processed to retrieve attenuation, phase, and dark-field images of the generated plasma. The resulting images accurately captured the plasma and scattering profiles, establishing the viability of this technique and paving the way for future HEDP studies on XFEL facilities. |
Thursday, November 11, 2021 4:24PM - 4:36PM |
UO06.00013: Talbot-Lau X-ray Deflectometry of laser-irradiated foils: comparison of experimental results and simulations Maria Pia Valdivia Leiva, Christian Stoeckl, Victorien Bouffetier, Gabriel Perez Callejo, Chad Mileham, Kazuki Matsuo, Mathieu Bailly-Grandvaux, Sarah Fess, Jun Zou, Alexis Casner, Farhat Beg, Sean P Regan, Dan Stutman For the first time, the ablation front of an irradiated CH foil (150 J, 2 ns) was imaged on Omega EP with the newly established TIM-based Talbot-Lau X-ray Deflectometer (TXD). TXD diagnostics can measure electron density gradients to characterize HED plasmas through phase-contrast methods. A Moiré fringe pattern was recorded using 8 keV x-ray backlighting generated by irradiating a thin copper foil with a short pulse laser (150 J, 10 ps, 70 µm) 5 ns after main driving beam. A 2D refraction angle map (<150 µradians) was obtained through phase-retrieval methods even though the fringe contrast measured was less than the theoretical maximum. The experimentally retrieved map matches post-processed 8 keV refraction angle maps obtained using 2D FLASH electron density simulations. Additionally, the experimental Moire image was analyzed using the newly developed Talbot Interferometry Analysis (TIA) tool which can produce synthetic Moire images using electron density and temperature information from FLASH simulations. The comparison between experimental and simulated results, including advanced analysis tools and techniques, demonstrates the potential of Talbot-Lau x-ray interferometry as a reliable HEDP diagnostic. Further developments to the TXD diagnostic, including monochromatic backlighting to improve fringe contrast and x-ray backlighter optimization to improve spatial resolution, are discussed. |
Thursday, November 11, 2021 4:36PM - 4:48PM |
UO06.00014: Planar laser induced fluorescence mapping of a carbon laser produced plasma Robert S Dorst, Derek B Schaeffer, Jessica J Pilgram, Carmen G Constantin, Stephen T Vincena, Shreekrishna Tripathi, Christoph Niemann We present measurements of ion velocity profiles obtained by planar laser induced fluorescence (PLIF) on an explosive laser produced plasma (LPP) from recent experiments on the Large Plasma Device at the University of California, Los Angeles. We utilized a tunable, diode pumped solid state laser to scan through doppler shifted wavelengths in order to map out carbon ion velocities as a function of space and time. Unlike many LIF schemes that excite the ions or atoms at a wavelength different than the observed wavelength, our population is only susceptible to a two-level model where the ions are excited and fluoresce at the same wavelength. These measurements are compared to a study in which hydrodynamic and collisional-radiative simulations are used to estimate the expected signal-to-noise ratio, as well as employed to benchmark a hybrid simulation code. |
Thursday, November 11, 2021 4:48PM - 5:00PM |
UO06.00015: Long-duration x-ray source development for x-ray diffraction at the National Ignition Facility Kalpani - Werellapatha, Gareth N Hall, Federica Coppari, Gregory E Kemp, Nathan E Palmer, Andrew Krygier, Christine M Krauland, Shahab F Khan, Amy E Lazicki, Martin G Gorman, Sabrina R Nagel, Chuck Heinbockel, Neal Bhandarkar, Nathan Masters, David K Bradley, Jon H Eggert, Laura Robin Benedetti We study the feasibility of producing x-ray sources over timescales relevant to support time-resolved x-ray diffraction (XRDt) measurements during laser-driven dynamic compression experiments at the National Ignition Facility (NIF) [1]. XRDt probes the atomic structure in-situ of transformations at extreme thermodynamic conditions. To record XRD of phase transitions as they occur, we use high-speed (~1 ns) gated hybrid CMOS imagers [2], which provide multiple frames of data over a timescale of a few to tens of ns. To make effective use of these imagers, the x-ray source needs to be temporally and spectrally uniform as long as the sensors remain active. |
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