Bulletin of the American Physical Society
55th Annual Meeting of the APS Division of Plasma Physics
Volume 58, Number 16
Monday–Friday, November 11–15, 2013; Denver, Colorado
Session PO7: Magnetized HEDP and Laser X-ray Source |
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Chair: Vyacheslav Lukin, Naval Research Laboratory Room: Governor's Square 12 |
Wednesday, November 13, 2013 2:00PM - 2:12PM |
PO7.00001: Magnetic Reconnection of an Externally Applied Magnetic Field in a High-Energy Density Plasma G. Fiksel, D. Barnak, P.-Y. Chang, S.X. Hu, P.M. Nilson, R. Betti, W. Fox, K. Germaschewski, A. Bhattacharjee An experiment on magnetic reconnection of an externally applied magnetic field in counter-propagating high-energy density plasmas was conducted on the OMEGA EP Laser System.\footnote{L. J. Waxer\textit{ et al.}, Opt. Photonics News \textbf{16}, 30 (2005).} Two counter-propagating plasma flows were created by irradiating oppositely placed plastic (CH) targets with 1.8-kJ, 2-ns laser beams. An external magnetic field was imposed perpendicular to the plasma flow by MIFEDS (magneto-inertial fusion electrical discharge system).\footnote{O. V. Gotchev\textit{ et al.}, Rev. Sci. Instrum. \textbf{80}, 043504 (2009).} The magnetic field has a null-x-point geometry with $B=5\mbox{\thinspace T}$ at the targets. The plasma interaction was imaged by laser-driven, fast-proton radiography. The radiography images demonstrate formation of a pair of counter-propagating magnetized ``ribbons'' that collide and reconnect at the midplane. The results will be compared with particle-in-cell simulations and interpreted with predictions from the \textit{DRACO} code. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944, and NLUF Grant DE-SC0008655. [Preview Abstract] |
Wednesday, November 13, 2013 2:12PM - 2:24PM |
PO7.00002: Launching and Colliding Magnetized Plasma Jets on the OMEGA Laser R.P. Young, C.C. Kuranz, R.P. Drake, D. Froula, J. Ross, C.K. Li, G. Fiksel In April 2012, we had a successful shot day on the OMEGA-60 laser, proving that rear irradiation of thin, conical, acrylic foils can produce a fast, hot, dense plasma jet. We will present a selection of data from that day, focusing on the Thomson scattering data and its implications for fundamental fluid parameters such as Reynolds and magnetic Reynolds numbers. We may also present preliminary data from our shot day in August 2013, which is in final planning as this abstract goes to press. The August shot day will build upon our success in April 2012 by adding an imposed magnetic field and proton radiography capabilities to the experiment. This work is funded by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, grant number DE-FG52-09NA29548, and by the National Laser User Facility Program, grant number DE-NA0000850. [Preview Abstract] |
Wednesday, November 13, 2013 2:24PM - 2:36PM |
PO7.00003: Generating Long Scale-Length Plasma Jets Embedded in a Uniform, Multi-Tesla Magnetic-Field Mario Manuel, Carolyn Kuranz, Alex Rasmus, Sallee Klein, Jeff Fein, Patrick Belancourt, R.P. Drake, Brad Pollock, Andrew Hazi, Jaebum Park, Jackson WIlliams, Hui Chen Collimated plasma jets emerge in many classes of astrophysical objects and are of great interest to explore in the laboratory. In many cases, these astrophysical jets exist within a background magnetic field where the magnetic pressure approaches the plasma pressure. Recent experiments performed at the Jupiter Laser Facility utilized a custom-designed solenoid to generate the multi-tesla fields necessary to achieve proper magnetization of the plasma. Time-gated interferometry, Schlieren imaging, and proton radiography were used to characterize jet evolution and collimation under varying degrees of magnetization. Experimental results will be presented and discussed. This work is funded by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, grant number~DE-NA0001840, by the National Laser User Facility Program, grant number~DE-NA0000850, by the Predictive Sciences Academic Alliances Program in NNSA-ASC, grant number DEFC52-08NA28616, and by NASA through Einstein Postdoctoral Fellowship grant number PF3-140111 awarded by the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical Observatory for NASA under contract NAS8-03060. [Preview Abstract] |
Wednesday, November 13, 2013 2:36PM - 2:48PM |
PO7.00004: Observation of astrophysical Weibel instability in counterstreaming laser-produced plasmas W. Fox, G. Fiksel, A. Bhattacharjee, K. Germaschewski, P.-Y. Chang, S.X. Hu, P.M. Nilson Astrophysical shocks are typically collisionless and require collective electromagnetic fields to couple the upstream and downstream plasmas. The Weibel instability has been proposed to be one of such collective mechanism. Here we present laboratory tests of this process through observations of the Weibel instability generated between two counterstreaming, supersonic plasma flows, generated on the OMEGA~EP laser facility by irradiating of a pair of opposing parallel CH targets by UV laser pulses (0.351~$\mu$m, 1.8~kJ, 2~ns). The Weibel-generated electromagnetic fields were probed with an ultrafast proton beam, generated with a high-intensity laser pulse (1.053 $\mu$m, 800~J, 10~ps) focused to $>10^{18}$ W/cm$^2$ onto a thin Cu disk. Growth of a striated, transverse instability is observed at the midplane as the two plasmas interpenetrate, which is identified as the Weibel instability through agreement with analytic theory and particle-in-cell simulations. These laboratory observations directly demonstrate the existence of this astrophysical process, and pave the way for further detailed laboratory study of this instability and its consequences for particle energization and shock formation.\\[4pt] This work was supported by DOE grant DE-SC0007168. [Preview Abstract] |
Wednesday, November 13, 2013 2:48PM - 3:00PM |
PO7.00005: Increasing Magnetic-Field Capability of MIFEDS Using an Inductively Coupled Coil D.H. Barnak, P.-Y. Chang, G. Fiksel, R. Betti, C. Taylor Magnetized high-energy-density plasma (HEDP) science is a very active and relatively unexplored field that has applications in inertial confinement fusion (ICF), astrophysical plasma science, and basic plasma physics. A self-contained device, the magneto-inertial fusion electrical discharge system (MIFEDS) was developed at the Laboratory for Laser Energetics to conduct magnetized HEDP experiments on both the OMEGA and OMEGA EP Laser Systems. Extremely high magnetic fields are a necessity for magnetized HEDP and continue to drive the redevelopment of the MIFEDS device. The MIFEDS device has recently been upgraded to quadruple the stored energy, reduce the internal impedance of the device, and double the magnetic field. A redesign of the MIFEDS targets allows for robust and repeatable operation and for accommodation of various experimental arrangements. A new design for an inductively coupled coil for MIFEDS is presented. Details of this new design and its performance are provided, as well as a brief overview of the critical design features and limitations. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and DE-FC02-04ER54789 (Fusion Science Center). [Preview Abstract] |
Wednesday, November 13, 2013 3:00PM - 3:12PM |
PO7.00006: Demonstration of a 13 keV Kr K-shell X-Ray Source at the National Ignition Facility K.B. Fournier, M.J. May, J.D. Colvin, M.A. Barrios, J.R. Patterson, S.P. Regan We report 3{\%} conversion efficiency of laser energy into Kr K-shell ($\approx$13~keV) radiation, consistent with theoretical predictions. This is $\approx$10$\times$ greater than previous work. The emission was produced from a 4.1 mm diameter, 4 mm tall gas pipe target filled with 1.2 or 1.5~atm of Kr gas. 160 of the NIF laser beams deposited $\approx$700~kJ of 3$\omega$ light into the target in a $\approx$140~TW, 5.0 ns duration square pulse. This laser configuration sufficiently heated the targets to optimize the K-shell x-ray emission. The Dante diagnostics measured $\approx$5~TW into 4{$\pi$} solid angle of $\geq$12~keV x~rays for $\approx$4~ns, which includes both continuum emission and flux in the Kr He$_{\alpha}$ line at 13~keV. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. [Preview Abstract] |
Wednesday, November 13, 2013 3:12PM - 3:24PM |
PO7.00007: High-Ti-concentration foams as laser-driven x-ray sources J.D. Colvin, F. Perez, J.R. Patterson, M.J. May, J. Emig, M.M. Biener, A. Wittstock, J.H. Satcher, S.A. Gammon, J.F. Poco, S. Fujioka, Z. Zhang, H. Nishimura, K.B. Fournier Metals between Ti and Ge are used for bright x-ray sources in the 4-10 keV range when irradiated by energetic nanosecond lasers. To maximize their laser-to-x-ray conversion efficiency (CE), lower density is preferred, achieved usually with pre-exploded thin foils or very-low-density foams (\textless 10 mg/cm$^{3})$. We present recent experimental results using novel foams of high Ti concentration. Previous foams were doped with less than 5 at{\%} of Ti. We manufactured two new types of foams with density $\sim$ 5 mg/cm$^{3}$ and Ti concentrations 20 and 33 at{\%}. They have been tested as x-ray sources in two laser facilities, OMEGA (USA) and GEKKO XII (Japan). CEs \textgreater 5{\%} are measured, significantly higher than previous achievements with the lower-concentration foams. We describe laser-heating dynamics simulation results and comparisons to time-resolved measurements, indicating strong differences between the several foams used. [Preview Abstract] |
Wednesday, November 13, 2013 3:24PM - 3:36PM |
PO7.00008: Spectral and radiative characterization of multi-keV X-ray sources M.A. Barrios, R. Epstein, K.B. Fournier, S.P. Regan, M. May, K. Widmann, O. Landen, H.S. Park, B.R. Maddox, C. Huntington, D. Bradley, H.A. Scott, G.W. Collins K-shell emission line sources were generated using laser-irradiated targets for various high-Z materials including Zn (Z$=$30), Ge (Z$=$32), Br (Z$=$35), Rb (Z$=$37), Zr (Z$=$40), Mo (Z$=$42) and Ag (Z$=$47). The plasma x-ray emission was spectrally characterized using temporally resolved and time-integrated x-ray spectrometers, providing absolute x-ray fluence and time-integrated K-shell emission brightness. Targets were driven with up to 60 kJ of 3$\omega $ laser light leading to irradiance on target ranging from (0.5 to 18)x10$^{15}$ W/cm$^{2}$. The He-like resonance 1s$^{2}$-1s2p(1P) and intercombination 1s$^{2}$-1s2p(3P) and satellite transitions dominated the spectrum for all the elements except Ag, which emitted K-alpha light. T$_{\mathrm{e}}$ and n$_{\mathrm{e}}$ profiles from hydrodynamic simulations were used to evaluate detailed atomic models, providing comparison between calculated and absolute time-integrated measured line profiles and continuum levels. This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344. [Preview Abstract] |
Wednesday, November 13, 2013 3:36PM - 3:48PM |
PO7.00009: Optimizing 9-25 keV point projection 2D backlighters Kevin Baker, Steve MacLaren, Gail Glendinning, Richard Seugling, Nick Whiting, Chuck Source, Julie Fooks, Kevin Fournier, Monika Biener, David Martinez, Vladimir Smalyuk, Tom Dittrich, Alastair Moore, Tom Guymer The conversion efficiency of zinc He$_{\mathrm{\alpha }}$ backlighter and silver k$_{\mathrm{\alpha }}$ sources have been studied on the OMEGA laser. A common platform was used to evaluate the conversion efficiency from Zn foils with and without a 2.8 ns prepulse and from low density zinc foams containing varying quantities of zinc relative to low Z foam constituents. The common platform consisted of a 2 mm diameter by 2 mm long tube that was either filled with a low density foam or had two foils glued on the ends of an empty tube. The foam targets, which underwent volume ionization, exhibited more uniform radial emission above 1 keV than the foil targets. The thinnest Zn exploding foil targets stagnated in the middle of the tube producing a temporally longer He$_{\mathrm{\alpha }}$ emission than the other targets. The highest overall conversion efficiency came from a foil target driven with a 2.8 ns prepulse. Initial results from silver k$_{\mathrm{\alpha }}$ sources will also be presented. [Preview Abstract] |
Wednesday, November 13, 2013 3:48PM - 4:00PM |
PO7.00010: X-ray backlighter development for high energy density experiments on NIF Channing Huntington, Brian Maddox, Hye-Sook Park, Matthew Terry, Shon Prisbrey, Christopher Plechaty, Bruce Remington Bright, high-energy backlighters are an essential diagnostic tool for experiments on high energy density facilities. Laser driven 5-12 keV thermal He$_\alpha$ x-ray sources are widely used in ICF/HED experiments, and higher energy 17-50 keV cold K$_\alpha$ sources have been developed using short pulse, petawatt lasers. For many x-ray imaging applications, both source brightness and spatial resolution are crucial. In order to optimize these characteristics, we compared the x-ray emission from Ag foils irradiated with 1 $\mu$m and $^1$/$_3$ $\mu$m wavelength laser light. We find that single-sided laser illumination of $\mu$-flag foils tamped with diamond on the back side improves the spatial resolution in a point-projection imaging configuration. Monte Carlo methods are adopted to fully understand the diagnostic spatial resolution using x-ray knife-edge data. Experimental results from Omega and NIF are shown where 1D and 2D simulations have been employed to optimize brightness and spatial resolution. [Preview Abstract] |
Wednesday, November 13, 2013 4:00PM - 4:12PM |
PO7.00011: Characterization of x- and gamma- radiation in relativistically intense laser-solid interactions Bixue Hou, Calvin Zulick, Zhen Zhao, John Nees, Thomas Batson, Anatoly Maksimchuk, Alexander G.R. Thomas, Karl Krushelnick Using a high resolution ($\lambda $/$\Delta \lambda $\textgreater 100) high purity germanium detector, the angular and material dependence, and the intensity scaling, of bremsstrahlung gamma radiation from relativistically intense (I\textgreater 10$^{\mathrm{18}}$ W/cm$^{\mathrm{2}})$ laser-solid interactions have been characterized at energies between 0.1 and 1 MeV with the high-repetition rate (500 Hz) Lambda-Cubed laser facility. The bremsstrahlung spectra of SiO$_{\mathrm{2}}$, Mo, and Eu$_{\mathrm{2}}$O$_{\mathrm{3}}$ were observed to have two-temperature energy distributions, corresponding to two different groups of electrons and depending on both laser intensity and observation angle. The spectra and source sizes of hard x-radiation under 0.1 MeV are also studied. These x-ray sources are being developed for phase-contrast imaging. [Preview Abstract] |
Wednesday, November 13, 2013 4:12PM - 4:24PM |
PO7.00012: Investigation of the high-energy x-ray spectrum of pinhole point-projection backlighters Jeff Fein, Paul Keiter, Carolyn Kuranz, Christine Krauland, Jonathan Peebles, Charlie Jarrott, Sallee Klein, Josh Davis, Robb Gillespie, James Holloway, Paul Drake Laser-produced hot electrons may present many undesirable effects in high-energy-density physics experiments. In particular, the secondary production of high-energy x-rays produces a background that reduces the signal-to-noise. Experiments were performed to study the hot electron-induced high-energy x-ray background present in pinhole point-projection x-ray backlighters. In these experiments, bremsstrahlung x-ray spectrometers (BMXS) were used to measure the high-energy x-ray signal from the backlighter targets. The response of the BMXS diagnostic is capable of retrieving both the continuous x-ray spectrum and a best fit of the hot electron temperature describing the hot electron energy distribution. We will present the inferred hot electron temperatures and discuss how the x-ray spectra depend on backlighter and pinhole substrate material. Additionally, we will discuss the x-ray spectra angular dependence. Lastly, we will discuss the effect of the background on the quality of x-ray radiographic data. [Preview Abstract] |
Wednesday, November 13, 2013 4:24PM - 4:36PM |
PO7.00013: Production of petawatt laser pulses of picosecond duration via Brillouin amplification of nanosecond laser beams R. Trines, R. Bingham, P. Norreys, K. Humphrey, D. Speirs, R.A. Cairns, F. Fi\'uza, P. Alves, L.O. Silva The demonstration of fast-ignition (FI) inertial confinement fusion (ICF) requires the delivery of 40 kJ - 100 kJ of laser energy to the hot spot within 16 ps, preferrably at near-infrared wave lengths (351 nm). However, high-energy picosecond petawatt beams at 351 nm are extremely difficult to generate using conventional solid-state laser systems. Previous studies have shown that Raman amplification in plasma is a potential route for the production of petawatt pulses of picosecond duration at 351 nm [Trines et al., PRL, 2011]. In this paper we show, through analytic theory and particle-in-cell simulations, that similar results can also be obtained through Brillouin amplification of a short seed laser beam off a long pump beam at moderate intensity. Scaling laws governing the optimal parameter space for pump beam, seed beam and plasma will be derived using a self-similar model for Brillouin scattering, and verified via simulations. A comparison with Raman scattering will be made, to determine which scheme is most suitable for a range of laser-plasma configurations. [Preview Abstract] |
Wednesday, November 13, 2013 4:36PM - 4:48PM |
PO7.00014: Using XFELs to probe fast electron generation and filamentation in ultra-intense laser-solid interactions Thomas Kluge, Christian Gutt, Lingen Huang, Josefine Metzkes, Michael Bussmann, Ulrich Schramm, Thomas Cowan The interaction of ultra-intense lasers with solid density matter produces extreme current densities of relativistic electrons which are useful in many wide-ranging applications including high-gradient laser-ion acceleration, intense surface harmonic generation, isochoric heating, and investigation of fast ignition inertial fusion. The fundamental electron generation and transport physics is difficult to accurately model with PIC simulations, due to the strong influence of return current neutralization which relies on the full bulk material and plasma response of the target. Directly probing the laser-solid interaction, including the ionization dynamics, surface electron acceleration, and bulk return current structure would provide a major step forward in validating our modeling and understanding. The use of small angle x-ray scattering (SAXS) at hard x-ray XFELs will be described as a means to directly measure the solid-density plasma electron-electron correlations, and the resulting fast electron generation and associated filamentation instabilities. [see T. Kluge, C. Gutt et al, arXiv:1306.0420] [Preview Abstract] |
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