Bulletin of the American Physical Society
56th Annual Meeting of the APS Division of Plasma Physics
Volume 59, Number 15
Monday–Friday, October 27–31, 2014; New Orleans, Louisiana
Session UO5: High-intensity Laser-plasma Interactions |
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Chair: Hui Chen, Lawrence Livermore National Laboratory Room: Galerie 2 |
Thursday, October 30, 2014 2:00PM - 2:12PM |
UO5.00001: Absorption of high-contrast, intense short laser pulses on solids Andreas Kemp, Laurent Divol We study the interaction of a 10J / 100fs intense laser pulse with solid aluminum using 1D and 2D kinetic / collisional particle simulations. In particular we are interested in an accurate description of the early phase of the interaction where the target is still cold, assuming that no plasma formation has set in before the arrival of the pulse. While most of the laser pulse is reflected, penetration of light into the skin layer and collisional heating lead to fast heating of the skin layer, and an increasing absorption of light into several groups of energetic electrons. We discuss details of the resulting electron spectrum, and plasma conditions expected immediately behind the interaction region under realistic conditions. [Preview Abstract] |
Thursday, October 30, 2014 2:12PM - 2:24PM |
UO5.00002: Simulations of High Intensity Short Pulse Lasers Incident on Reduced Mass Targets Using LSP Frank W. King, Chris Orban, Kramer U. Akli, Douglass Schumacher We present the results of a series of fully kinetic 2D simulations using the PIC code LSP for the study of the heating and deformation of reduced mass targets. These simulations model a full scale laser pulse incident on full scale targets as a function of intensity, spot size, pre-plasma, and target lateral extent and thickness. We observe that the target deformation and heating has a strong dependence on intensity of the laser pulse and creation of a shock in the target. We also include a comparison of 2D and 3D kinetic runs that allows us to compare temperatures. [Preview Abstract] |
Thursday, October 30, 2014 2:24PM - 2:36PM |
UO5.00003: Simulation of Laser Pulse Driven Terahertz Generation in Inhomogeneous Plasmas Chenlong Miao, John Palastro, Thomas Antonsen Intense, short laser pulses propagating through plasma generate THz radiation. Full format PIC simulations and theoretical analysis are conducted to investigate two mechanisms of ponderomotively driven THz radiation: transition radiation, and slow wave phase matching enabled by corrugated plasma channels. The first mechanism occurs as a laser pulse crosses a plasma boundary [1] and is analogous to transition radiation emitted by charged particle beams. The THz radiation resulting from this transition radiation mechanism (TRM) is characterized by conical emission and a broad spectrum with the maximum frequency occurring near the plasma frequency. The second mechanism occurs in axially periodic plasma channels [2, 3]. These channels support electromagnetic modes with slow wave (Floquet-type) dispersion, which can be phase matched to the ponderomotive current. The slow wave phase-matched radiation (SWPM) is characterized by lateral emission and a coherent spectrum with sharp modes at frequencies associated with the channel. \\[4pt] [1] L. M. Gorbunov et. al., Plasmas Physics Reports Vol. 32, No. 10 (2006).\\[0pt] [2] T. M. Antonsen et. al., Phys. Plasmas 14, 033107 (2007).\\[0pt] [3] A. J. Pearson et. al., Phys. Review E 83, 056403 (2011). [Preview Abstract] |
Thursday, October 30, 2014 2:36PM - 2:48PM |
UO5.00004: Temperature Measurements of Fusion Plasmas Produced by Laser-Irradiated D$_{2}-^{3}$He or CD$_{4}-^{3}$He Clustering Gases W. Bang, T. Ditmire, H. Quevedo, G. Dyer, A.C. Bernstein, M. Donovan, E. Gaul, M. Barbui, A. Bonasera, K. Hagel, J.B. Natowitz We report on experiments in which a mixture of D$_{2}$ or CD$_{4}$ clusters and $^{3}$He gas was irradiated by a petawatt-laser pulse, generating nuclear fusion reactions such as D($d$, $^{3}$He)$n$, D($d$, $t)p$, and $^{3}$He($d$, $p)^{4}$He. We measured the yields of fusion neutrons and protons from these reactions and found them to agree with yields based on a simple cylindrical plasma model. The plasma temperature was determined by two different methods. In the first, it was derived from time-of-flight data of deuterium ions ejected from exploding D$_{2}$ or CD$_{4}$ clusters. In the second, it was measured from the ratio of neutron yield to proton yield from D($d$, $^{3}$He)$n$ and $^{3}$He($d$, $p)^{4}$He reactions, respectively. The temperatures determined by these two methods agree well, indicating (i) the ion energy distribution is not significantly distorted when ions travel in the disassembling plasma; (ii) the kinetic energy of deuterium ions, especially the hottest part responsible for nuclear fusion, is well described by a near-Maxwellian distribution. [Preview Abstract] |
Thursday, October 30, 2014 2:48PM - 3:00PM |
UO5.00005: Measurements of Surface Magnetic Fields Driven by Refluxing Electrons in OMEGA EP Experiments A. Davies, D. Haberberger, A.A. Solodov, D.H. Froula, L. Ceurvorst, P.A. Norreys A polarimeter was used to measure the field strength, spatial extent, and temporal evolution of magnetic fields generated around the focus of an intense ($I \approx 9\times 10^{18}$ W/cm$^{2}$) 100-ps OMEGA EP laser pulse. The interaction of the laser with solid Cu targets was probed using the 4$\omega $ diagnostic system.\footnote{ A. Davies \textit{et al.}, ``Polarimetry Diagnostic on OMEGA EP Using a 10-ps, 263-nm Probe Beam,'' submitted to Review of Scientific Instruments.} The magnetic field was observed to expand radially from the focal point along the target surface as a coronal plasma forms. The laser--plasma interactions were modeled using \textit{OSIRIS} particle-in-cell and \textit{LSP} hybrid model simulations. Initial results suggest that the magnetic field is generated by electrons traveling near the speed of light spreading radially from the interaction point. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944. [Preview Abstract] |
Thursday, October 30, 2014 3:00PM - 3:12PM |
UO5.00006: OMEGA EP OPAL: A Path to a 100-PW Laser System D.D. Meyerhofer, S.-W. Bahk, J. Bromage, D.H. Froula, D. Haberberger, S.X. Hu, B.E. Kruschwitz, R.L. McCrory, J.F. Myatt, P.M. Nilson, J.B. Oliver, C. Stoeckl, W. Theobald, L.J. Waxer, J.D. Zuegel The four-beam OMEGA EP Laser System at the Laboratory for Laser Energetics could be reconfigured to pump an optical parametric chirped-pulse--amplification (OPCPA) laser system. Current estimates suggest that energies in excess of 2 kJ in a 20-fs pulse would be possible with four-beam pumping. This could lead to peak intensities above $10^{23}$ W/cm$^2$. Additional configurations could include two femtosecond beams, or a combination of femtosecond, picosecond, and nanosecond kilojoule-class laser beams. This talk will describe the potential system and some of the physics opportunities for which it would provide access. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944. [Preview Abstract] |
Thursday, October 30, 2014 3:12PM - 3:24PM |
UO5.00007: Ultra-intense Pair Creation using the Texas Petawatt Laser and Applications Edison Liang, Alexander Henderson, Taylor Clarke, Willie Lo, Petr Chaguine, Gilliss Dyer, Nathan Riley, Kristina Serratto, Michael Donovan, Todd Ditmire Pair plasmas and intense gamma-ray sources are ubiquitous in the high-energy universe, from pulser winds to gamma-ray bursts (GRB). Their study can be greatly enhanced if such sources can be recreated in the laboratory under controlled conditions. In 2012 and 2013, a joint Rice-University of Texas team performed over 130 laser shots on thick gold and platinum targets using the 100 Joule Texas Petawatt Laser in Austin. The laser intensity of many shots exceeded 10$^{21}$ W.cm$^{-2}$ with pulses as short as 130 fs. These experiments probe a new extreme regime of ultra-intense laser - high-Z solid target interactions never achieved before. In addition to creating copious pairs with the highest density (\textgreater 10$^{15}$/cc) and emergent e$+$/e- ratio exceeding 20{\%} in many shots, these experiments also created the highest density multi-MeV gamma-rays, comparable in absolute numbers to those found inside a gamma-ray burst (GRB). Potential applications of such intense pair and gamma-ray sources to laboratory astrophysics and innovative technologies will be discussed. [Preview Abstract] |
Thursday, October 30, 2014 3:24PM - 3:36PM |
UO5.00008: Absorption of ultra-intense intense laser pulse in self-generated pair plasma Thomas Grismayer, Marija Vranic, Ricardo Fonseca, Luis Silva Plasma physics in extreme fields requires taking into account Quantum Electrodynamics effects such as non-linear Compton scattering and Breit-Wheeler pair production. Such effects intervene in laser-plasma interactions at ultra high intensities (I \textgreater 1023 W/cm$^2$). The self-consistent modeling of these scenarios is challenging since some localized regions of ultra-intense field will produce a vast number of pairs that may cause memory overflow during the simulation. To overcome this issue, we have developed a merging algorithm that allows merging a large number of particles into fewer particles with higher particle weights while conserving local particle distributions. This algorithm is crucial to investigate the laser absorption in self-generated pair plasmas. During the interaction, the laser energy is converted into pairs and photons and the absorption become significant when the plasma density reaches the critical density. We present the results of 3D PIC-QED simulations (Osiris 2.0) showing the respective fraction of laser energy transferred into pairs and photons. The dependence of the laser absorption on the laser parameters for various configurations is also discussed. [Preview Abstract] |
Thursday, October 30, 2014 3:36PM - 3:48PM |
UO5.00009: The Scaling of Positron Production in Intense Laser-Solid Interactions Hui Chen, A. Link, F. Fiuza, A. Hazi, S.R. Nagel, J. Park, R. Tommasini, G.J. Williams, Y. Sentoku, D.D. Meyerhofer, J.F. Myatt, P. Audebert, R. Fedosejevs, S. Kerr, M. Hill, D. Hoarty, L. Hobbs, S. James The dependence of positron yield on laser energy was observed to be nonlinear through experiments using the laser facilities at Jupiter, OMEGA EP, and ORION for laser energies of 100 - 1500 J and intensities of 10$^{18} - 10^{20}$ Watts/cm$^{2}$. The measured yield increases as $\sim$E$^{2}$, faster than that predicted by simple estimates using GEANT4. This scaling results from a combination of higher energy electrons produced at increased laser intensity and the presence of unexpected recirculation of MeV electrons in the mm-thick target. Experimental results together with analytical and Monte-Carlo simulations of the data will be presented. [Preview Abstract] |
Thursday, October 30, 2014 3:48PM - 4:00PM |
UO5.00010: Investigating ultra-fast phenomena in laser-plasma interactions using DIXI (dilation x-ray imager) S.R. Nagel, H. Chen, M.E. Foord, P.M. Bell, D.K. Bradley, A.U. Hazi, E.V. Marley, J. Park, G.J. Williams, S.M. Kerr, T.J. Hilsabeck, J.D. Kilkenny, A.K.L. Dymoke-Bradshaw, J.D. Hares Time resolved x-ray images with 7 ps resolution were recorded on relativistic short-pulse laser-plasma experiments at the TITAN laser at LLNL. The data was recorded using the dilation x-ray imager (DIXI), a new high-speed x-ray framing camera sensitive to x-rays in the range of $\sim$1-17 keV. DIXI, a 2D imager, uses the pulse-dilation technique to achieve a temporal resolution down to 5 ps, otherwise only attainable with 1D-streaked imaging. Using titanium foils as targets and as buried layers in plastic targets, we measured the electron beam divergence and the effects of target back thickness and laser pre-pulse on the emission evolution through the time-resolved 2D images of the x-ray emission. This technique allows for the investigation of fast electron transport within the target with unprecedented temporal resolution. The data interpretation is supported by LSP simulations. Work supported by U.S. Department of Energy under Contract DE-AC52-06NA27279. LLNL-ABS-656682 [Preview Abstract] |
Thursday, October 30, 2014 4:00PM - 4:12PM |
UO5.00011: Proton probing of a relativistic laser interaction with near-critical plasma Louise Willingale, C. Zulick, A.G.R. Thomas, A. Maksimchuk, K. Krushelnick, P.M. Nilson, C. Stoeckl, T.C. Sangster, W. Nazarov The Omega EP laser (1000 J in 10 ps pulses) was used to investigate a relativistic intensity laser interaction with near-critical density plasma using a transverse proton beam to diagnose the large electromagnetic fields generated. A very low density foam target mounted in a washer provided the near-critical density conditions. The fields from a scaled, two-dimensional particle-in-cell simulation were inputed into a particle-tracking code to create simulated proton probe images. This allows us to understand the origins of the complex features in the experimental images, including a rapidly expanding sheath field, evidence for ponderomotive channeling and fields at the foam-washer interface. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0002028. [Preview Abstract] |
Thursday, October 30, 2014 4:12PM - 4:24PM |
UO5.00012: Investigation of collective electron dynamics in relativistically transparent laser-foil interactions Ross Gray, David MacLellan, Bruno Gonzalez-Izquierdo, Haydn Powell, David Carroll, Christopher Murphy, Luca Stockhausen, Dean Rusby, Graeme Scott, Robbie Wilson, Nicola Booth, Dan Symes, Steve Hawkes, Ricardo Torres, Marco Borghesi, David Neely, Paul McKenna The interaction of an intense laser pulse with a solid target produces high energy electrons at the target-vacuum boundary. For sufficiently high laser intensities and thin targets, the electrons become relativistic and rapidly expand into vacuum, lowering the peak electron density. The combined increase in the relativistically-corrected critical density and the reduction in the target electron density results in the onset of relativistic induced transparency (RIT) during the laser pulse, enabling the remainder of the pulse to propagate through the target and further interact with the accelerated electrons. We report on measurements of the collective dynamics of laser driven electrons in the RIT regime. The 2D profile of the beam of accelerated electrons is shown to change from an ellipse aligned along the laser polarization direction in the case of limited RIT, to a double-lobe structure aligned perpendicular to it, for a larger degree of RIT. The temporal dynamics of the interaction are investigated via PIC simulations. The implications of RIT for laser-driven ion acceleration is also explored. [Preview Abstract] |
Thursday, October 30, 2014 4:24PM - 4:36PM |
UO5.00013: The Effect of Pre-formed Plasmas on Relativistic Electron Acceleration Jaebum Park, Laurent Divol, Hui Chen, Sabrina Nagel, G. Jackson Williams, Shaun Kerr Pre-formed plasmas effects have been extensively studied and are known to affect relativistic electrons production via laser plasma interactions. However, there are still many unknowns, such as laser energy absorption vs. scale-length and material dependence. We have investigated the pre-formed plasmas effects on relativistic electrons by simultaneously measuring the plasma density with a 2w optical interferometer and relativistic electron energy distributions on the LLNL Titan laser. The pre-formed plasmas were produced on Parylene-N and Ti targets by a separate laser and/or the ASE of the short pulse (SP) laser with upper 10$^{19}$ W/cm$^2$ at 1w. A 3-D wedge geometry HYDRA simulation is used to benchmark sub-critical density and infer scale-length at the critical density. Electron energy ratios of along the SP beam to the target back normal show stronger pre-formed plasmas effects on creation of relativistic electrons from Parylene-N than Ti. [Preview Abstract] |
Thursday, October 30, 2014 4:36PM - 4:48PM |
UO5.00014: Investigation of time-resolved fast electron dynamics in ultra-intense laser-solid interactions James Green, Alex Robinson, Dean Rusby, Lucy Wilson, Chris Murphy, Rachel Dance, Ross Gray, David MacLellan, Paul McKenna, Chris Ridgers The study of fast electron transport in laser-solid interactions is crucial for many key applications. Laser-accelerated particle beams will require compact laser systems operating at high repetition rates, hence experimental effort to characterise acceleration processes using femtosecond laser sources is crucial. A thorough understanding of fast-electron acceleration and transport underpins the development of most of these applications, necessitating both temporally and spatially-resolved measurements. Here an overview will be presented of unique fast electron transport results from the Astra Gemini laser ($10^{21}$ Wcm$^{-2}$, 40 fs). Using high resolution rear surface optical probing, together with complementary ion acceleration measurements, we have undertaken a study of the earliest stages of fast electron dynamics. How various target and laser parameters directly affected both the electron distribution and subsequent ion acceleration will be detailed, with computational modeling supporting the experimental observations. [Preview Abstract] |
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