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 TO03: HED: Short-pulse laser applications to HED and ICFOn Demand
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Chair: Hui Chen, Lawrence Livermore National Laboratory Room: Rooms 302-303 |
Thursday, November 11, 2021 9:30AM - 9:42AM |
TO03.00001: Improving spectral analysis of buried layer experiments at the Orion Laser Facility Dylan T Cliche, Madison E Martin, Gregory V Brown, Mark E Foord, Richard A London, Duane A Liedahl, Mike J MacDonald, Joseph Nilsen, Mehul V Patel, Howard A Scott, Ronnie L Shepherd, Klaus Widmann, Heather D Whitley, Robert F Heeter, David J Hoarty High energy density (HED) plasmas are present throughout the Universe in stars, planetary interiors, accreting black holes, and in laboratory experiments. HED matter has proven difficult to study experimentally, and there are significant challenges in our ability to model and predict the properties of HED systems with high confidence. Short-pulse laser-driven opacity experiments have been conducted at the Atomic Weapons Establishment’s Orion Laser Facility [1] — resulting in a collection of x-ray emission data from a variety of materials. During these experimental campaigns, the spectral diagnostics have become increasingly sophisticated, and now include multiple time-resolved spectrometers as well as different imaging diagnostics. In this talk, we discuss improvements made to create synthetic spectroscopic data for comparison to measurements from recent iron experiments. We focus on the post-processing of radiation-hydrodynamic models with Cretin [2]. Comparisons between synthetic and measured spectra aid in understanding the evolution of plasmas produced in short-pulse laser-driven buried layer experiments performed at the Orion laser facility. |
Thursday, November 11, 2021 9:42AM - 9:54AM |
TO03.00002: Radiation Transfer in the Spectra of Short-Pulse Laser Heated Targets Richard A London, Gregory V Brown, Mark E Foord, Duane A Liedahl, Madison E Martin, Howard A Scott, Ronnie L Shepherd Short pulse lasers are useful for creating high energy density (HED) plasmas. Typical experiments have used ps-duration, 102 J pulses, focused to 102 µm diameter spots on thin targets to create plasmas with temperatures ~107 K and densities ~3 g/cm-3 [1]. HED plasmas are studied primarily by their emitted x-ray spectra. Comparisons of measured-to-simulated line strengths and widths are used to diagnose the temperature and density. The validity of this method depends on accurate spectra modeling. Many previous applications of such diagnostics have assumed optically thin plasmas. However, some of the x-ray lines that are used, particularly the H- and He-like alpha lines of elements such as S, have optical depths of 1 to 10. This calls for the inclusion of radiation transfer in the models. To this end, coupled atomic kinetics/radiation transfer simulations have been carried out with the Cretin code [2]. Simulated spectra with and without radiation transfer effects are presented. Comparisons to data obtained at the Orion Laser Facility are analyzed to determine the effect of radiation transfer on the inferred temperatures. |
Thursday, November 11, 2021 9:54AM - 10:06AM |
TO03.00003: Simulations of short-pulse laser driven buried layer experiments at Orion Madison E Martin, Gregory V Brown, Mark E Foord, Dylan T Cliche, Richard A London, Duane A Liedahl, Joseph Nilsen, Mike J MacDonald, Mehul V Patel, Ronnie L Shepherd, Klaus Widmann, Heather D Whitley, Robert F Heeter, Howard A Scott, David J Hoarty Opacity is a critical parameter in the transport of radiation in high energy density (HED) systems such as inertial confinement fusion capsules and stars. Over the years, experimental capabilities have expanded to allow the study of plasmas at even higher densities and temperatures. Time-integrated and time-resolved spectra of iron at conditions greater than 1 g/cc and 1 keV were measured at the Orion short-pulse laser [1]. We have applied 1-dimensional radiation-hydrodynamic models using HYDRA [2] to simulate plasma conditions and used a simple ray tracing methodology to synthesize x-ray emission in order to study sensitivities of synthetic x-ray emission to modeling assumptions. We show that while our 1-D methodology has been useful for predicting and matching many aspects of the experimental spectra, this simplified method does not create a consistent picture for all materials in the experiment. We therefore introduce potential improvements to the methodology that may aid in understanding sensitivities of our emission-based opacity platform. |
Thursday, November 11, 2021 10:06AM - 10:18AM |
TO03.00004: Absorption of relativistic multi-picosecond laser pulses in wire arrays Andreas J Kemp, Scott Wilks, Ginevra E Cochran, Shaun M Kerr, Jaebum Park, Gary Grim, Riccardo Tommasini We study the interaction of intense multi-picosecond laser pulses with arrays of carbon wires attached to solid substrates. We find that laser absorption in wire arrays resembles that in flat targets with very large uniform plasma density gradients. Performing two-dimensional particle-in-cell simulations, we optimize target parameters like wire thickness and -distance for energy absorption of a 2ps laser pulse with a large focal spot; this has implications for x-ray- and charged particle source development. |
Thursday, November 11, 2021 10:18AM - 10:30AM |
TO03.00005: Analysis and development of a NIF-ARC backlighter for high-resolution >40 keV x-ray radiography Jackson J Williams, Matthew P Hill, Alex B Zylstra, Camelia V Stan, Edward Gumbrell, Tom E Lockard, Robert E Rudd, Damian C Swift, David A Martinez, David Alessi, Daniel H Kalantar, James M McNaney, Hye-Sook Park We present on the analysis of x-ray backlighter data using a multi-component test object to reconstruct the spatial and spectral profiles. The Advanced Radiographic Capability (ARC) short pulse laser at the National Ignition Facility (NIF) irradiated a 5μm-thin dysprosium foil in an edge-on line-projection radiography orientation that produced a hard x-ray source with high resolution in one dimension. Analysis using forward fitting and genetic algorithms are used to provide understanding of the spectral content, including line emission, while Monte Carlo simulations provide an estimate of the spatially dependent changes in backlighter characteristics. This ARC platform has superior spatial and temporal resolution compared to an existing long-pulse-driven backlighter and is being evaluated for use on indirectly and directly driven dynamic strength experiments at the NIF. |
Thursday, November 11, 2021 10:30AM - 10:42AM |
TO03.00006: K-shell emission of highly-ionized copper from relativistically-intense laser pulses Nicholas Beier, Hunter G Allison, Yasmeen Musthafa, Franklin J Dollar, Vigneshvar Senthilkumaran, Reed C Hollinger, Ryan Nedbailo, Huanyu Song, Shoujun Wang, Jorge J Rocca, Philip C Efthimion, Lan Gao, Brian F Kraus, Kenneth W Hill, Kirk A Flippo, Stephanie B Hansen, Ronnie L Shepherd, Amina E Hussein We will discuss our recent work performing high-resolution (E/ΔE > 5000) X-ray spectroscopy of copper K-shell emission from high-intensity (I ∼1021 W/cm2) laser experiments using the high contrast (> 10-11) ALEPH 400 nm laser at Colorado State University. Through simultaneous measurement of front- and rear-side K-shell fluorescence and accompanying collisional-radiative modeling we examine the generation and propagation of energetic electrons in thin foil and layered targets to elucidate the physics of ultra high-intensity, laser-solid interactions. |
Thursday, November 11, 2021 10:42AM - 10:54AM |
TO03.00007: Impact of moving to 2 micron laser wavelengths on High Energy Density Science applications Scott Wilks, Andreas J Kemp, Tom Spinka, Brendan Reagan, Edward P Hartouni, Stephen B Libby, Elizabeth S Grace, Edison P Liang High peak power ( > 100 TW) short pulse ( < 10 ps) lasers operating near 1 μm now provide bright particle and photon sources for a myriad of applications, from proton deflectometry[1] to flash radiography[2]. The utility of these lasers, however, is limited by their low average power. A new laser architecture, based on Tm:YLF, has been proposed that has the potential to dramatically increase average power by 1000 fold, thereby allowing a laser source to access a whole new class of applications (e.g., static radiography and medical applications) that require high average power that are currently accessible only by conventional particle accelerators. However, Tm:YLF systems produce laser light closer to 2 μm, rather than the usual 1 μm light used now. We compare and contrast the performance of sample HEDS applications for both wavelengths via simulation studies, and consider the impact this switch to longer wavelength would have on these existing and future applications. [1] P.-E. Masson-Laborde et al. PRE 99, 053207 (2019) [2] R. Tommasini et al. PRL 125, 155003 (2020) |
Thursday, November 11, 2021 10:54AM - 11:06AM |
TO03.00008: Laser driven shocks in aluminum using a short pulse table-top system Sophie E Parsons, Michael R Armstrong, Ross E Turner, Christian Childs, Paulius Grivickas, Tanner Cordova, Harry B Radousky, Javier E Garay, Farhat N Beg In laser induced shock wave experiments, a short pulse, high intensity laser is used to drive a high pressure shock wave into a material. These experiments often employ an aluminum driver layer. We report on a joint experimental and theoretical effort to better understand the behavior of this aluminum driver layer under the high pressure conditions relevant to ultrafast compression present during shock experiments. This study aims to further enhance the maximum pressure capabilities of short pulse table top laser systems. The samples pre- pared for study consisted of an aluminum driver layer with a sapphire tamper. The drive pressure induced was studied as a function of thicknesses of both the Al drive layer and the tamper. The pressure induced in the aluminum will be obtained using wave speeds measured via linear spectroscopy. To support this study, simulations were used to model the induced pressure for various ex- perimental setups using both hydro-codes and codes capable of simulating the laser-matter interaction interaction. Comparisons with the experimental data give insight into the hydrodynamics of the shock, as well as to verify the validity of these codes in this regime. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.This work was supported by the Defense Threat Reduction Agency under Award No. HDTRA12020001. LLNL-ABS-824421. |
Thursday, November 11, 2021 11:06AM - 11:18AM |
TO03.00009: Maximizing MeV photon dose of a short-pulse, laser-driven source via large-scale simulations of solid target laser-plasma interactions Kyle G Miller, Dean R Rusby, Andreas J Kemp, Scott Wilks, Warren B Mori There is interest in using intense, short-pulse lasers to produce bright high-energy sources for the probing of hot, dense material in high-energy density science. We are particularly interested in producing large quantities of hot electrons through laser-solid interactions, which can then provide high-energy X-rays through Bremsstrahlung radiation. At facilities of interest, laser amplitude and duration can be varied with the desire to produce an optimal quantity of MeV X-rays. We present a set of large-scale (100s of μm wide) and long-duration (10s of ps) particle-in-cell simulations with varied laser parameters that maintain constant pulse energy. Characteristics of the hot-electron population are examined, showing clear trends in electron temperature as a function of the normalized vector potential a0. The electron spectrum is also used to calculate the X-ray Bremsstrahlung radiation spectrum for various target thicknesses. The results provide guidance as to the optimal laser intensity and duration for the greatest number of 1–5 MeV X-rays. |
Thursday, November 11, 2021 11:18AM - 11:30AM |
TO03.00010: Ionization states for the multi-petawatt laser-QED regime Iustin Ouatu, Ben T Spiers, Ramy Aboushelbaya, Qingsong Feng, Marko W Mayr, Robert W Paddock, Robin Timmis, Peter A Norreys, Karl M Krushelnick A paradigm shift in the physics of laser-plasma interactions is approaching with the commissioning of multi-petawatt laser facilities world-wide. Radiation reaction processes will result in the onset of electron-positron pair cascades and, with that, the absorption and partitioning of the incident laser energy, as well as the energy transport throughout the irradiated targets. To accurately quantify these effects, one must know the focused intensity on target in-situ. In this work, a new way of measuring the focused intensity on target is proposed based upon the ionization of Xe gas at low ambient pressure. The field ionization rates from Phys. Rev. A 59, 569 (1999) and from Phys. Rev. A 98, 043407 (2018), where the latter has been derived using Quantum Mechanics methods, have been implemented for the first time in the particle-in-cell code Smilei [Comput. Phys. Commun. 222, 351-373 (2018)]. A series of one- and two-dimensional particle-in-cell simulations are compared and shown to reproduce the charge states without presenting visible differences when increasing simulation dimensionality. The results provide a way to accurately verify the intensity on target using in-situ measurements. |
Thursday, November 11, 2021 11:30AM - 11:42AM |
TO03.00011: Neutron and Hot Electron Production in Nanofoam Targets Using Ultra-Intense Short Pulse Lasers Ginevra E Cochran, Christopher M Cooper, Nicholas Czapla, Rebecca L Daskalova, Zac Gavin, Kevin Glennon, David Hanggi, Edward P Hartouni, Andreas J Kemp, Shaun M Kerr, Derek Nasir, Patrick Poole, Pedro L Spingola, German Tiscareno, Scott Wilks, Jarrod Williams, Douglass W Schumacher, Gary Grim Generating ion distributions with tens of keV energies at near solid density has the potential to allow nuclear reaction cross section measurements of relevance to astrophysics. Recently, a platform has been proposed [1] which can accomplish this using an ultra-intense short pulse laser and unstructured nanofoam CH or CD targets, which consist of ~100 nm ligaments with a few micron thick plastic front surface. The laser impinging on this front surface produces hot electrons, which stream through the foam, accelerating ions via TNSA normal to the ligaments and creating a plasma in which charged particle reactions can take place. Experimental results using these targets at the Scarlet laser facility in f/17 mode (≤5x1020 W/cm2, 30 fs) including the neutron and hot electron production from nanofoam targets as a function of foam composition, converter layer thickness, and incident laser parameters, will be presented. |
Thursday, November 11, 2021 11:42AM - 11:54AM |
TO03.00012: Amplification of sub-ns pulses in plasma optic at NIF Patrick Poole, Robert K Kirkwood, Thomas D Chapman, Scott Wilks, Matthew R Edwards, Daniel H Kalantar, Pierre A Michel, Laurent Divol, Nathaniel J Fisch, Peter A Norreys, Wojciech Rozmus, Jeff Bude, Brent E Blue, Kevin B Fournier, Bruno Van Wonterghem Future laser applications require increases in pulse energy, power, and intensity beyond the limitations of conventional solid-state media. Plasma optics are a promising solution due to their increased resiliency to damage but require characterization in the linear and nonlinear response regimes. The plasma amplifier platform at NIF has transferred energy between up to 21 beams to nearly 8 kJ in 1 ns and investigated details such as the time history of this power transfer and the amplification of a focusing pulse. Recent efforts have targeted the design of a second amplification stage intended to boost a short pulse (100 ps) to higher power, for which an understanding of fast ion wave response on the kJ energy scale is critical. Experimental results demonstrating the amplification of sub-ns pulses down to 100 ps with kJ-class pumps in the beam combiner geometry will be presented along with accompanying simulations. |
Thursday, November 11, 2021 11:54AM - 12:06PM |
TO03.00013: Frequency upshifting a CO2 laser pulse by collision with a relativistic ionization front Mitchell Sinclair, Chaojie Zhang, Yipeng Wu, Audrey Farrell, Zan Nie, Kenneth A Marsh, Navid Vafaei-Najafabadi, Irina Petrushina, Rotem Kupfer, Mikhail Polyanskiy, Igor Pogorelsky, Marcus Babzien, Mikhail Fedurin, Karl Kusche, Mark A Palmer, Chandrashekhar Joshi Research into tunable lasers is a well-developed field that has a broad range of applications including coherent IR spectroscopy, high-harmonic generation, and single cycle and attosecond pulse generation. We show simulation and experimental results of a novel method of frequency upshifting a 9.2 μm, two picosecond, CO2 laser pulse of intensity Io = 140 TW/cm2 by colliding it with a relativistic ionization front. A high-intensity Ti:Sapphire laser driver propagates through a hydrogen gas jet and is used to create a step-like ionization front that propagates close to the speed of light. As observed by the CO2 pulse, the driver induces a temporal change to the index of refraction, which causes frequency upshift and pulse duration compression of the CO2 laser pulse as it collides with the ionization front. Particle-in-Cell (PIC) simulations show that the wavelength of the upshifted pulse can be tuned in a broad range with high efficiency by changing the plasma density. For experimental demonstration of this effect, we are presently conducting an experiment at the Accelerator Test Facility (ATF) at Brookhaven National Laboratory where we expect to continuously upshift the frequency of the incident CO2 laser in the wavelength range from 9.2 μm to 4.6 μm. We have designed a single-shot spectrometer for the transmitted radiation that is capable of characterizing the energy, frequency, and bandwidth of the upshifted pulse. This experimental work is performed in collaboration with Stony Brook University and the ATF at Brookhaven National Laboratory. |
Thursday, November 11, 2021 12:06PM - 12:18PM |
TO03.00014: Focusing High-Power Laser Pulses with Diffractive Plasma Lenses Matthew R Edwards, Nicholas M Fasano, Vadim R Munirov, Nuno Lemos, Eugene Kur, Julia M Mikhailova, Jonathan S Wurtele, Pierre A Michel The construction of compact high-power laser systems requires the manipulation of light at intensities above the ionization threshold of optical materials. Diffractive plasma optics, based on spatial patterns of either ionization or ion-displacement driven by interfering pump beams, provide damage-resistant control of high intensity light that is relatively resistant to plasma inhomogeneity and nonlinearity. We describe here how two pump lasers can be overlapped to produce zone-plate-like diffractive plasma lenses that focus and collimate high-intensity light. Results from analytic models are supported by particle-in-cell simulations, nonlinear pulse propagation calculations, and experimental measurements of ionization gratings. Simulations suggest that femtosecond pulses can be focused by experimentally feasible plasma lenses with greater than 70% efficiency at up to sub-relativistic unfocused intensities. The development of plasma replacements for key components of short-pulse lasers will allow continued advancement towards higher-power light sources. |
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