Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Plasma Physics
Volume 67, Number 15
Monday–Friday, October 17–21, 2022; Spokane, Washington
Session TO08: Beams: X-Ray Sources and X-Ray DiagnosticsLive Streamed
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Chair: Matthew Edwards, Lawrence Livermore Natl Lab Room: 402 ABC |
Thursday, October 20, 2022 9:30AM - 9:42AM |
TO08.00001: Optimization of bremsstrahlung MeV X-ray generation from laser-plasma interaction Adeola C Aghedo, Dean Rusby, Nuno Lemos, Andreas J Kemp, Felicie Albert, Carol Y Scarlett, Andrew Mackinnon, Hui Chen, Jeff D Bude A. Aghedo, D.R. Rusby, N. Lemos, H. Chen, A. Kemp, J. Bude, F. Albert, C. Scarlett and A.J. Mackinnon |
Thursday, October 20, 2022 9:42AM - 9:54AM |
TO08.00002: Dynamic X-ray imaging of shock evolution and plasma instability formation using a laser wakefield accelerator Mario Balcazar, Tobias Ostermayr, Hai-En Tsai, Matthew Trantham, Paul T Campbell, Sahel Hakimi, Robert E Jacob, Yong Ma, Rachel Young, Paul King, Raspberry A Simpson, Elizabeth S Grace, Brendan Kettle, Eva E Los, Felicie Albert, Jeroen van Tilborg, Stuart P.D. Mangles, John Nees, Eric H Esarey, Cameron R Geddes, Alexander G Thomas, Carolyn C Kuranz Laser wakefield acceleration is a source of ultrafast, and spatially-coherent X-ray pulses with small source size suitable for high resolution imaging. In combination with a high-repetition-rate scheme, the radiation bursts permit recording submicron scale time-dependent systems such as hydrodynamic instabilities. In this work we performed dynamic phase-contrast X-ray imaging of the interaction of a long laser pulse with a liquid target, thus observing the evolution of a shock wave in water with unprecedented spatio-temporal resolution. CRASH hydrodynamic simulations complement the experimental results agreeing qualitatively well for t < 1ns, yet the data reveals unforeseen physics later in time. This includes multi-shock generation within the liquid jet, and plasma instability formation. It is suspected that the absence of charge separation in CRASH is responsible for some of the effects observed with the X-rays. To this end, innovative electron-beam radiography was used to probe the laser-plasma interplay finding evidence of bilateral heating of the water followed by strong electric field generation. These measurements help explaining some of the discrepancies between simulation and experiment and pave the way to better plasma diagnostic systems in HED physics experiments. |
Thursday, October 20, 2022 9:54AM - 10:06AM |
TO08.00003: Exponent of the spectral power–law from High–order Harmonic generation Shikha Bhadoria, Thomas G Blackburn, Arkady Gonoskov, Mattias Marklund Visible or near infra-red light can be manipulated to produce bursts of coherent extreme ultraviolet (XUV) or X-rays via the relativistic high-order harmonic generation process, when a laser irradiates a solid plasma target. The intensity of spectral components decays with increase of harmonic order and the efficiency of this non-linear process largely hinges on how prompt this decay is. This is governed by the conditions of the laser-plasma interaction, for which various models have been proposed. Using 1D PIC simulations, we analyse the trends for the reemitted spectral decay for different laser-plasma interaction parameters, particularly the pre-plasma scale length, the incidence angle and the carrier envelope phase, and discuss the optimization opportunities. Our simulations show that, rather than there being one universal exponent, the spectral decay is a continuous function of laser-plasma interaction parameters [1]. Such thorough parameter-scans of an individual interaction scenario with additional machine-learning-based diagnostics [2] can advance plasma-HHG as a rich radiation source. |
Thursday, October 20, 2022 10:06AM - 10:18AM |
TO08.00004: Characterization of sub-picosecond laser-produced fast electrons via modeling of bremsstrahlung with 3-D hybrid PIC simulations for hard x-ray radiography Lei Chen, Hiroshi Sawada Broadband hard x-rays from an intense laser-solid interaction are essential for radiographs of high areal density objects and Inertial Confinement Fusion implosion cores. To accurately simulate angular- and time-dependent bremsstrahlung, it is critical to benchmark a numerical code with well-defined fast electron characteristics: an electron energy distribution, divergence angle, and laser-to-electron conversion efficiency. Here, we show validation of a 3-D hybrid particle-in-cell LSP code using angularly resolved bremsstrahlung. By irradiating a 100 µm thick Cu foil with or without a large CH backing (Cu-CH) with a 50 TW Leopard laser (15J, 0.35 ps, 2×1019 W/cm2), we measured escaped electrons and angularly resolved bremsstrahlung from the refluxing and non-refluxing targets. The measured bremsstrahlung at two angular positions was simultaneously fit to determine a divergence angle and energy of an injected electron beam, while a single slope temperature was inferred from the electron measurement. A fitting result for the Cu-CH target shows that the divergence angle and conversion efficiency are estimated to be 52° ± 8° and 10.8 ± 1.4% when the slope temperature of 1.15 MeV is used. A parameter study for the Cu target shows a similar conversion efficiency, but simulations with any divergence angle match the measurement, indicating that strong electron recirculation in the Cu foil makes the divergence angle indistinguishable. The benchmarked code is further used to simulate angular- and time-dependent bremsstrahlung. Details of the simulated x-ray source for radiography applications will be discussed. |
Thursday, October 20, 2022 10:18AM - 10:30AM |
TO08.00005: Bright and stable betatron beams from various injection schemes in laser-driven plasma wakefield Harsh Harsh, Daniel Ullman, Felipe Cezar Salgado, Andreas Seidel, Alexander Sävert, Georg Schaefer, Ingo Uschmann, Matt Zepf With the evolution of various injection techniques[1] in laser-driven wakefield acceleration (LWFA) since 2004 [2], we now have more control over our resultant electron beams. This in turn facilitates a bright and stable betatron beam. |
Thursday, October 20, 2022 10:30AM - 10:42AM |
TO08.00006: Time resolved high resolution K-shell spectroscopy of Ti nanowire plasmas heated with highly relativistic laser pulses Reed C Hollinger, Shoujun Wang, Ryan Nedbailo, Jaebum Park, Huanyu Song, Vyacheslav Shlyaptsev, Jorge J Rocca, Jerry Clark, Ronnie L Shepherd, Jim A Emig, Ed Magee, Mike J MacDonald, Cuyler B Beatty, Christoph Baumann, Alexander Pukhov, Brooklyn Frances Kraus, Lan Gao, Philip C Efthimion, Kenneth W Hill, Manfred L Bitter High resolution (E/DE > 5000) spectra were taken from Ti nanostructured arrays irradiated at highly relativistic intensities (>1021Wcm-2) at the ALEPH laser facility at Colorado State University using a suite of crystal x-ray spectrometers. The x-ray emission was simultaneously observed with time integrated and time resolved crystal spectrometers, the latter with sub picosecond temporal resolution. The laser targets consisted of TiO2 nanotubes, ~100nm in diameter with ~20nm wall thickness, arranged with different spacings corresponding to 7%, 15% and 27% of solid density. The time integrated spectrometer, comprised of three individual spherically bent crystals, observed emission from the He-a, He-b and Ly-a line series while the time resolved spectrometer observed emission from the He-a and He-like intercombination line. Doppler and Stark broadened profiles were studied systematically versus plasma density along with density sensitive features such as the He-b. Time-resolved x-ray emission reveals that the lower density nanowire arrays reach higher temperatures and radiate for longer durations of time (~25 ps) whereas the higher density nanowire arrays radiate for shorter times, converging with the x-ray emission of solid density foils. The experimental results will be compared to three-dimensional particle-in-cell simulations and detailed atomic physics code computations. |
Thursday, October 20, 2022 10:42AM - 10:54AM |
TO08.00007: Controlling laser-driven electron distribution functions through nanostructured targets in the high intensity short-pulse regime Andreas J Kemp, Scott Wilks, Joshua Ludwig, Dean Rusby, Nuno Candeias Lemos, Ginevra Cochran, Jeffrey Bude, Andrew Mackinnon, Riccardo Tommasini, Gary P Grim Nanostructured materials consisting of solid-density wires with diameters ranging from tens of nanometers to several micrometers and lengths up to hundreds of micrometers, either as uniformly oriented wires or foams, have recently seen a surge in interest as targets for intense short laser pulses (ie sub-nanosecond pulse durations, intensity >1e18W/cm2). This is thanks to novel manufacturing techniques and improved energy contrast in high power laser systems. The very high absorption of optical light makes the nanostructured targets a trace for applications like short-pulse laser driven x-ray genera=on, particle acceleration and studies of atomic and nuclear physics at extreme conditions, all topics at the heart of high energy density physics (HEDP). One aspect of nanostructured targets that will be highlighted in this talk is our ability to control the directionality and energy spectra of laser-generated hot electrons via manipulating the structure and shape of the target. |
Thursday, October 20, 2022 10:54AM - 11:06AM |
TO08.00008: OPTIMIZED CONTINUUM X-RAY EMISSION FROM LASER-GENERATED PLASMA Andrew Krygier, Gregory E Kemp, Federica Coppari, Daniel Thorn, David K Bradley, Alexandre Do, Jon H Eggert, Warren W Hsing, Shahab F Khan, Christine M Krauland, Otto L Landen, Michael J MacDonald, James M McNaney, Hye-Sook Park, Bruce A Remington, Michael S Rubery, Marilyn B Schneider, H. Sio, Yuan Ping We study continuum x-ray emission from hot plasma at the National Ignition Facility (NIF). We find that the x-ray yield in the multi-keV photon energy range is larger in Ti than in Ag or Au. This apparent paradox is due to Ti K-shell vacancies generated by the extraordinary energy density achieved by the NIF lasers. This is supported by direct observations of large continuum enhancement above the Ti K-series limit due to both free–bound (recombination) emission and strong Ly a (H-like) emission. Detailed calculations agree well with our measurements and support our conclusions. Results of extended x-ray absorption fine structure measurements of highly compressed solids at NIF using this source will also be presented. |
Thursday, October 20, 2022 11:06AM - 11:18AM |
TO08.00009: Small Scale Hohlraums Useful as High Fluence X-Ray Sources Mark J May, William A Farmer, Natalie Kostinski, Patrick Poole, Peter A Amendt, Scott Brandon, Marilyn B Schneider, Shon T Prisbrey, Richard L Berger High fluence x-ray sources are needed for various high energy density physics experiments. Photon energies between a few hundred eV to ~ 100 keV are desirable in a source. One method for creating a bright source utilizes the laser heating of a small scale hohlraum target. These hohlraums have an LEH of 2208 micron and a length of 1380 micron. and are heated with 200 TW for 1.68 ns from 96 beams of the NIF laser. We report a T(rad) ~ 370 eV from these targets with a laser coupling of greater than 96%. In addition, these targets have a significant emission of ~ 20 J/sr for photon energies above 10 keV. Experimental results and comparisons with simulations will be presented. This work was done under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344. |
Thursday, October 20, 2022 11:18AM - 11:30AM |
TO08.00010: Recent progress in flying-focus research John P Palastro, Manfred Virgil Ambat, Antonino Di Piazza, Martin Formanek, Philip Franke, Dustin Froula, Bernardo Malaca, Warren B Mori, Miguel Pardal, Jacob R Pierce, Jeremy Pigeon, Dillon Ramsey, Hans Rinderknecht, Jessical L Shaw, Tanner Simpson, David Turnbull, Jorge Vieira, Marija Vranic, Kathleen Weichman Flying focus pulses feature a programmable-velocity intensity peak that can travel distances far greater than a Rayleigh range while maintaining a near-constant spatiotemporal profile. These features promise to revolutionize a wide range of laser-based applications that require velocity control or extended interaction lengths at high intensity. Here we present recent developments in flying-focus research, including a new optical design for creating flying focus pulses with improved properties; analytical and numerical techniques for modeling these pulses; applications, such as nonlinear Thomson scattering, photon acceleration, and radiation reaction detection; and ongoing proof-of-principle propagation experiments. |
Thursday, October 20, 2022 11:30AM - 11:42AM |
TO08.00011: Increases in high-intensity laser-driven electron, positron, and x-ray sources using microstructure targets Dean R Rusby, Nuno Lemos, Hui Chen, Adeola Aghedo, Andrew M Longman, Scott Wilks, Jackson G Williams, Anthony J Link, Andy J Mackinnon, Shaun M Kerr, Jeff D Bude, Andreas J Kemp The efficient generation of bright, high-energy sources of MeV x-rays, electrons and positrons using high-intensity lasers is vital if they are to be considered competitive to conventional accelerator sources. Using microstructure/wire targets on the front surface of a 1mm thick gold converter and the Omega-EP high-intensity laser driver (>1019 W/cm2) at the Laboratory for Laser Energetics, we have demonstrated enhancement in the flux and energies of measured electrons, positrons, and x-rays. The Omega-EP laser delivered up to 900 Joules over the duration of the 10-picosecond laser pulse. During the laser pulse the target microstructures expand, filling the gaps in-between the structures with a low-density plasma. As the separation of the microstructure is increased, we observe the highest enhancements in yield of energetic particles. Experimentally, we observe increases in the numbers of electrons and x-rays with little change to the measured spectral shape. The positrons, whose energy depends on the laser driven electric fields at the surface of the target, increase in both peak energy and total number. For some shots, the number of measured positrons emitted from the target exceed the number of escaping electrons. These results will be compared to Particle in Cell modeling of these interactions [1,2]. |
Thursday, October 20, 2022 11:42AM - 11:54AM |
TO08.00012: Betatron X-rays for high-resolution imaging of micrometer-scale features in advanced materials Vigneshvar Senthilkumaran, Nicholas F Beier, Sylvain Fourmaux, Amina E Hussein During laser wakefield acceleration (LWFA), relativistic electrons trapped in the focusing phase of plasma wakefield undergo transverse oscillations leading to the emission of broadband keV X-rays, also known as betatron X-rays. Betatron X-rays have small, micro-meter source sizes with few-femtosecond pulse duration, making them ideally suited for high-resolution and time-resolved imaging of dense materials. Here, we will present characterization of the X-ray spectrum, spatial resolution, and source size of betatron X-rays generated using the Advanced Laser Light Source in Varennes, Canada. We present the optimization of these sources for imaging of defect evolution in additively manufactured AlSi10Mg alloys under tensile stress to elucidate the fracture mechanics of these novel materials. We also explore the application of betatron sources for probing of plasma structures generated in pulsed discharges in water to help address open questions about breakdown mechanisms in liquids. |
Thursday, October 20, 2022 11:54AM - 12:06PM |
TO08.00013: Streaking of betatron X-rays in a curved laser wakefield accelerator Yong Ma, Jason A Cardarelli, Paul T Campbell, Rebecca Fitzgarrald, Mario Balcazar, Andre F Antoine, Nicholas F Beier, Sylvain Fourmaux, Meriame Berboucha, Amina E Hussein, Brendan Kettle, Sallee R Klein, Karl M Krushelnick, Stuart P.D. Mangles, Qian Qian, Gianluca Sarri, Daniel Seipt, Vigneshvar Senthilkumaran, Rob Shalloo, Matthew Streeter, Louise Willingale, Alec G.R. Thomas Experiments conducted on the Advanced Laser Light Source at INRS demonstrated, for the first time, the streaking of betatron X-rays in a curved laser wakefield accelerator via controlling of the plasma density gradient. In a plasma with a transverse density gradient, laser wavefront tilt develops gradually due to phase velocity differences in different plasma densities. The wavefront tilt leads to a parabolic trajectory of the plasma wakefield and hence the accelerated electron beam, which leads to an angular streaking of the emitted betatron radiation. In this way, the temporal evolution of the betatron X-ray spectra will be converted into angular "streak," i.e., having a critical energy-angle correlation. By controlling the plasma density and the density gradient with multi-stage 3D printed gas targets, we realized the steering of the laser driver, electron beam and betatron X-rays simultaneously. The experimental results were verified with a theoretical model and Particle-in-Cell simulations. Angularly resolved X-ray spectra from such a curved laser wakefield accelerator open an avenue towards single-shot diagnostic techniques for reconstructing the temporal evolution of the electron acceleration process. Moreover, our work could also find applications in advanced control of laser beam and particle propagation, such as generating curved plasma channel for coupling multiple wakefield accelerators as well as enabling compact synchrotron sources. |
Thursday, October 20, 2022 12:06PM - 12:18PM |
TO08.00014: High resolution radiography with Self-Modulated laser wakefield accelerator driven X-rays Isabella M Pagano, Nuno Lemos, Paul M King, Mitchell Sinclair, Adeola C Aghedo, Andrea Hannasch, Thanh Ha, Jose Alejandro Franco-Altamirano, Hernan J Quevedo, Michael M Spinks, Constantin Aniculaesei, Shahab Khan, B M Hegelich, Michael C Downer, Chandrashekhar Joshi, Felicie Albert We are developing broadband X-ray sources with high spatio-temporal resolution to better image High Energy Density Science (HEDS) phenomena. A broadband X-ray source driven by Self-Modulated laser wakefield acceleration (SM-LWFA) was generated at the Jupiter Laser Facility, with photon energies from 10 KeV to > 1 MeV, and used to image an inertial confinement fusion hohlraum target with tungsten sphere positioned at the center, as well as a modified air force resolution target. These X-ray radiographs enabled us to determine the source size of the X-rays, in addition to the spectra (measured separately), using either the diffraction pattern cast by the edge of the resolution target, or by comparing the radiograph with a simulated image created by a modified X-ray ray-tracing model. We compare several different methods using SM-LWFA accelerated electrons to generate X-rays, including Betatron, Inverse Compton Scattering, and Bremsstrahlung. Due to the different spectral and resolution characteristics of these processes, they offer different performances for use in radiography in HEDS experiments. We also compare these radiographs with images taken at the Texas Petawatt Laser, where the sources are driven by blowout LWFA. This work will help us understand the variation of X-ray source characteristics with different laser-plasma parameters, and its impact on HEDS application experiments. |
Thursday, October 20, 2022 12:18PM - 12:30PM |
TO08.00015: Study of the influence of various pre-plasma conditions on laser-proton acceleration via x-ray spectroscopy Radka Stefanikova, Xiayun Pan, Michal Smid, Lennart Gaus, Michaela Kozlova, Stefan Kraft, Florian Kroll, Irene Prencipe, Marvin Reimold, Hans-Peter Schlenvoigt, Marvin Umlandt, Ulrich Schramm, Karl Zeil, Josefine Metzkes-Ng, Katerina Falk Laser driven ion acceleration is a fast growing field, where understanding of the internal processes of laser-plasma interaction is crucial for optimization of such ion sources. Namely, x-ray spectroscopy offers a unique in-situ view at plasma conditions and electron signatures from within the target, which can help to identify important parameters for optimization of the laser-driven acceleration process. |
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