Bulletin of the American Physical Society
57th Annual Meeting of the APS Division of Plasma Physics
Volume 60, Number 19
Monday–Friday, November 16–20, 2015; Savannah, Georgia
Session PO7: High Field Physics and Relativistic Plasmas |
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Chair: Thomas Grismayer, Instituto Superior Técnico, Portugal Room: 203 |
Wednesday, November 18, 2015 2:00PM - 2:12PM |
PO7.00001: Multi-laser QED cascades in 2D and 3D geometry Marija Vranic, Thomas Grismayer, Ricardo A. Fonseca, Luis O. Silva Studying the plasma dynamics in the presence of extreme laser fields requires taking into account physics beyond classical electrodynamics. Pair production seeded by an electron has a lowest threshold among the first quantum mechanisms that appear as the intensity increases, which makes it relevant for the future experiments planned at ELI [1] and other facilities. We have included the two-step pair production process (non linear Compton scattering $+$ Breit-Wheeler) in a massively parallel PIC code (Osiris 2.0 framework) via a Monte Carlo module. With this approach, we take self-consistently into account the interaction of the intense fields with the generated pair plasma. We have also developed a macroparticle merging algorithm that reduces the number of macroparticles in the simulations, while conserving local particle distributions [2]. This algorithm is crucial for simulating scenarios where a large number of pairs are being created, such as QED cascades.~ We present 2D and 3D PIC-QED study of pair cascades induced with multiple laser pulses. The polarization dependence is discussed, together with the properties of the emitted radiation and experimental signatures.~ \\[4pt] [1] http://www.eli-laser.eu/\\[0pt] [2] M. Vranic et al., CPC 191, 65-73 (2015) [Preview Abstract] |
Wednesday, November 18, 2015 2:12PM - 2:24PM |
PO7.00002: High Intensity Particle Physics at PW-class laser facilities Stepan Bulanov, Carl Schroeder, Eric Esarey, Timur Esirkepov, Masaki Kando, Nikolay Rosanov, Georg Korn, Sergey V. Bulanov, Wim P. Leemans The processes typical for high intensity particle physics, i.e., the interactions of charged particles with strong electromagnetic fields, have attracted considerable interest recently. Some of these processes, previously believed to be of theoretical interest only, are now becoming experimentally accessible. High intensity electromagnetic (EM) fields significantly modify the interactions of particles and EM fields, giving rise to the phenomena that are not encountered either in classical or perturbative quantum theory of these interactions. One of such phenomena is the radiation reaction, which radically influences the electron motion in an electromagnetic standing wave formed by two super-intense counter-propagating laser pulses. Depending on the laser intensity and wavelength, either classical or quantum mode of radiation reaction prevail, or both are strong. When radiation reaction dominates, electron motion evolves to limit cycles and strange attractors. This creates a new framework for high energy physics experiments on an interaction of energetic charged particle beams and colliding super-intense laser pulses. Work supported by U.S. DOE under Contract No. DE-AC02-05CH11231. [Preview Abstract] |
Wednesday, November 18, 2015 2:24PM - 2:36PM |
PO7.00003: Photon emission and pair production in the interaction of ultra-intense lasers with electrons Martin Jirka, Ondrej Klimo, Sergei Bulanov, Stefan Weber With the advent of 10 PW laser facilities, new regimes of laser-matter interaction are opening since QED effects come into play. Due to the radiation reaction which takes place in ultra-intense laser-matter interactions, charged particles lose their energy by emitting high-energy photons. These photons can in the strong laser field create electron-positron pairs via Breit-Wheeler process. One possible interaction scenario leading to efficient generation of pairs is the interaction of two colliding laser pulses with an electron target lying in the common focal spot. In our PIC simulations, gamma-ray photon emission and pair production are studied for different laser wavelengths, intensities and both laser polarization. According to our results, linearly polarized laser pulses seem to be more convenient for efficient pair creation. The role of ions contained in the target and its density are also assessed. Results are compared with the different interaction configuration when the energetic electron bunch interacts with one counter-propagating laser pulse. [Preview Abstract] |
Wednesday, November 18, 2015 2:36PM - 2:48PM |
PO7.00004: Contrast and Intensity upgrades to the Texas Petawatt laser for hadron generation and non-linear QED experiments Bjorn M. Hegelich, Alexey Arefiev, Todd Ditmire, Michael E. Donovan, Gillis Dyer, Erhard Gaul, Lance Labun, Scott Luedtke, Mikael Martinez, Edward McCarry, David Stark, Ishay Pomerantz, Ganesh Tiwari, Toma Toncian Advances in laser-based hadron generation, especially with respect to particle energy, as well as reaching the new regime of radiation dominated plasmas and non-linear QED, require laser fields of Petavolts per meter that preferably interact with very high density, overcritical plasmas. To achieve these conditions we are upgrading the Texas Petawatt Laser both respect to on-target laser intensity and laser-contrast, aiming to reach intensities of $\sim$ 5x10$^{22}$ W/cm$^2$ and pulse contrast parameters allowing the interaction with overcritical, yet ultrathin, sub-micron targets. We will report on the planned experiments aimed at ion acceleration, neutron generation and the first experimental measurement of radiation reactions to motivate the chosen upgrade parameters. We will further report on the technical changes to the laser and present first measurements of the achieved intensity and contrast parameters. [Preview Abstract] |
Wednesday, November 18, 2015 2:48PM - 3:00PM |
PO7.00005: Magnetically collimated pair jets at the LLNL Titan laser Jackson Williams, Hui Chen, Daniel Barnak, Riccardo Betti, Gennady Fiksel, Andrew Hazi, Shaun Kerr, Christine Krauland, Anthony Link, Mario Manuel, David Meyerhofer, Sabrina Nagel, Jaebum Park, Jonathan Peebles, Bradley Pollock, Riccardo Tommasini Positron-electron pair production experiments were performed at the Titan laser at the Jupiter Laser Facility to investigate the dependence of target thickness and atomic number on pair yield. Externally applied axial magnetic fields, generated by a Helmholtz coil, were used to collimate positrons where the signal observed at the detector increased by a factor of 20 over reference shots without a field. This enabled the detection of positrons from a range of target materials. The emitted positron yield was found to be proportional to the square of the atomic number. This scaling is reduced from the Bethe-Heitler cross section of $Z^4$ by Compton scattering and the stopping power of the target. Monte Carlo simulations support these conclusions, providing a power-law scaling of emitted positrons for all materials and a range of mm-thick targets. [Preview Abstract] |
Wednesday, November 18, 2015 3:00PM - 3:12PM |
PO7.00006: Dense High e$+$/e- Ratio Pair Creation using the Texas Petawatt Laser Edison Liang, Alexander Henderson, Wen Fu, Taylor Clarke, Devin Taylor, Willie Lo, Petr Chaguine, Hannah Hasson, Gillis Dyer, Kristina Serratto, Nathan Riley, Michael Donovan, Todd Ditmire We report results of pair creation experiments using $\sim$ 100 Joule pulses of the Texas Petawatt Laser to irradiate solid gold and platinum targets, with intensities up to 1.9x10$^{21}$W.cm$^{-2}$ and pulse durations as short as 130 fs. Positron to electron (e$+$/e-) ratios exceeding 15{\%} were observed for many thick disks ( $\ge $4mm) and long narrow rod targets, with the highest observed e$+$/e- ratio approaching 50{\%} for a Pt rod. The inferred pair yield was few x10 $^{10}$ with emerging pair density reaching 10$^{15}$/cc so that the pair skin depth becomes \textless pair jet transverse size, the minimum criterion for the pairs to become a ``plasma.'' These results represent important milestones towards the goal of creating a significant quantity of dense pair-dominated plasma with e$+$/e- approaching 100{\%} and pair skin depth \textless \textless pair plasma size, which will have wide-ranging applications to astrophysics, fundamental physics and innovative technologies. We will discuss some of these potential applications. [Preview Abstract] |
Wednesday, November 18, 2015 3:12PM - 3:24PM |
PO7.00007: Slow down of a globally neutral relativistic e-e$+$ beam shearing the vacuum E.P. Alves, T. Grismayer, M.G. Silveirinha, R.A. Fonseca, L.O. Silva It has been recently found that the development of electromagnetic instabilities between shearing, globally neutral polarisable dielectric slabs, separated by a nanometer-scale gap, can result in an effective non-contact friction force between slavs, which is the classical analogue of the quantum friction effect proposed by Pendry (1997). This effect has been explored analytically in the sub-relativistic regime, where the development of unstable electromagnetic modes parallel to the direction of motion are responsible for the non-contact friction effect. We explore the interaction of a relativistic, globally neutral e-e$+$ beam streaming through a hollow plasma/dielectric in the absence of overlap (no contact). We show through analytic theory and 3D particle-in-cell simulations that this relativistic scenario excites unstable electromagnetic modes transverse to the direction of propagation. The onset of this electromagnetic instability leads to the conversion of the kinetic energy of the e-e$+$ beam into electric and magnetic field energy, effectively slowing down a relativistic, globally neutral body in the absence of contact. We demonstrate that this effect be explored using beam properties that are readily available at the SLAC National Accelerator Laboratory. [Preview Abstract] |
Wednesday, November 18, 2015 3:24PM - 3:36PM |
PO7.00008: Source of collimated multi-MeV photons driven by radiation-reaction of an electron beam in a self-generated magnetic field David J. Stark, Alexey V. Arefiev, Toma Toncian Several facilities are due to be commissioned in the next few years that will operate at intensities above $5\times10^{22}$ $\mathrm{W/cm^2}$, which will open up the possibility of developing radiation-reaction driven gamma-ray sources. In this talk, we will present a promising setup in which a high intensity pulse irradiates a relativistically overdense target containing a relativistically transparent channel. The channel is employed to guide the laser pulse, thus allowing stable propagation, and to enable generation of energetic electrons in the underdense region via direct laser acceleration. The resulting electron beam is collimated and, as expected, the photon emission due to the electron interaction with the laser pulse itself is low. Efficient and directed emission by the beam is triggered in this setup by a quasi-static magnetic field generated by the longitudinal electron current driven by the laser in the channel. We have performed 2D simulations of a laser-plasma interaction in this setup using PIC code EPOCH that includes a photon emission module. The simulations show that over 5{\%} of laser energy at an intensity of $5\times10^{22}$ $\mathrm{W/cm^2}$ can be converted into a collimated beam of photons with energies above 20 MeV. [Preview Abstract] |
Wednesday, November 18, 2015 3:36PM - 3:48PM |
PO7.00009: Scaling of Ion Acceleration in Super Intense Laser Matter Interaction in Radiative Damping Regime Rishi Pandit, Yasuhiko Sentoku, Edward Ackad We had derived the radiation reaction terms including the higher orders and implemented in PICLS codes [R. Pandit and Y. Sentoku, Phys. Plasmas 19, 073304(2012)]. It was found that higher order terms of radiation reaction reduce the ponderomotive force as well as the photon pressure. The ponderomotive scaling, in super intense laser matter interactions, changes due to the decrease of the ponderomotive force on the electron and ion's accelerations. A new scaling of ion acceleration has been derived which depends on the laser intensity and oscillatory energy of electron. At $10^{23}$ W/cm$^2$ almost half of the ponderomotive force is damped due to higher order terms. We will show how the theoretical result compares with PICLS simulations by varying laser intensities to understand the effect of the reduced ponderomotive force in super intense laser matter interaction. [Preview Abstract] |
Wednesday, November 18, 2015 3:48PM - 4:00PM |
PO7.00010: Relativistic Laser Pulse Intensification with 3D Printed Micro-Tube Plasma Target Liangliang Ji, Joseph Snyder, Alexander Pukhov, Kramer Akli The potential and applications of laser-plasma interactions (LPI) are restricted by the parameter space of existing lasers and targets. Advancing the laser intensity to the extreme regime is motivated by the production of energetic particle beams and by the quest to explore the exotic regimes of light-matter interaction. Target density and dimensions can always be varied to optimize the outcome. Here, we propose to create another degree of freedom in the parameter space of LPI using recent advances in 3D printing of materials. Fine structures at nm scale with high repetition and accuracy can nowadays be manufactured, allowing for a full precise control of the target. We demonstrate, via particle-in-cell (PIC) simulations, that 3D-printed micro-tube plasma (MTP) targets yield an intensity enhancement factor of 2-5. The novel MTP targets not only act as a plasma optical device to reach the 10$^{23}$W/cm$^{2}$ threshold based on today's intensities, but can also boost the generation of secondary particle and radiation sources. This work demonstrates that the combination of high contrast high power lasers and nano-3D printing techniques opens new paths in the intensity frontier and LPI micro-engineering. [Preview Abstract] |
Wednesday, November 18, 2015 4:00PM - 4:12PM |
PO7.00011: Plasma lens focusing for multi-petawatt lasers John Palastro, Daniel Gordon, Richard Hubbard, Bahman Hafizi, Michael Helle, Dmitri Kaganovich A plasma lens provides the focusing power of a small f-number$_{\mathrm{\thinspace }}$solid-state lens at a fraction of the diameter. These lenses offer flexibility to multi-petawatt (MPW) laser systems where the final focusing optic is likely a large, one-of-a-kind parabolic mirror that fixes the f-number for all experiments. Here, we examine plasma lenses for MPW systems using a combination of a computationally efficient, nonlinear thin-lens model that captures high-order optical aberrations and 3D PIC simulations. We identify parameters such as lens location and curvature, and plasma density that minimize aberrations and provide the highest focused intensity. [Preview Abstract] |
Wednesday, November 18, 2015 4:12PM - 4:24PM |
PO7.00012: Raman Amplification in the Wavebreaking Regime Matthew Edwards, Zeev Toroker, Julia Mikhailova, Nathaniel Fisch Stimulated Raman scattering provides a plasma-based mechanism for transferring energy between laser pulses, allowing for the amplification of short laser pulses to intensities far beyond what is achievable with solid-state systems, but the method's usefulness depends on the identification of efficient parameter regimes robust to small inhomogeneities. The wavebreaking regime, characterized by the breakup of the Langmuir wave as the electron longitudinal quiver velocity exceeds the plasma-wave phase velocity, has been proposed as a potentially efficient regime for plasma amplification. Here we present particle-in-cell simulations of Raman amplification in this regime, showing that the breakup of the Langmuir wave is associated with lower amplification efficiencies. These results suggest that the search for optimal Raman amplification parameters should take place below, or not too far above, the wavebreaking threshold. [Preview Abstract] |
Wednesday, November 18, 2015 4:24PM - 4:36PM |
PO7.00013: Exotic and intense lasers with orbital angular momentum for laser plasma interactions Jorge Vieira, Raoul Trines, Eduardo Alves, Ricardo Fonseca, Jose T. Mendonca, Peter Norreys, Robert Bingham, Luis Silva Ultra-intense lasers have a multitude of applications in astrophysics, particle acceleration and radiation generation. Most advances were reached by exploiting a narrow set of fundamental laser properties, such as intensity and duration. The orbital angular momentum (OAM) is a new fundamental degree of freedom that can be exploited to reach new laser-plasma interactions regimes. Here, we explore the interaction between exotic laser pulses with orbital angular momentum, and plasmas resorting to theory and three-dimensional particle-in-cell OSIRIS [1] simulations. We will then explore Raman scattering processes in plasmas, and show that these process can amplify OAM lasers to intensities beyond the PW, similarly to the case of a Gaussian laser. We also show a new set of selection rules for the creation of new, initially absent laser modes with well defined OAM. We show that these intense OAM laser pulses could then be used to drive strongly non-linear plasma waves in the doughnut blowout regime [2]. We then show that the doughnut blowout regime can accelerate ring shaped electron and positron bunches.\\[4pt] [1] R.A. Fonseca et al, PPCF, 55 124011 (2013);\\[0pt] [2] J.Vieira et al, PRL 112, 215001 (2014). [Preview Abstract] |
Wednesday, November 18, 2015 4:36PM - 4:48PM |
PO7.00014: Influence of chirp on laser-pulse amplification in Brillouin backscattering schemes Goetz Lehmann, Friedrich Schluck, Karl-Heinz Spatschek Plasma-based amplification of laser pulses is currently discussed as a key component for the next generation of high-intensity laser systems, possibly enabling the generation of ultra-short pulses in the exawatt-zetawatt regime [1]. In these scenarios the energy of a long pump pulse (several ps to ns of duration) is transferred to a short seed pulse via a plasma oscillation. Weakly- and strongly-coupled (sc) Brillouin backscattering have been identified as potential candidates for robust amplification scenarios. With the help of three-wave interaction models, we investigate the influence of a chirp of the pump beam on the seed amplification. We show that chirp can mitigate deleterious spontaneous Raman backscattering of the pump off noise and that at the same time the amplification dynamics due to Brillouin scattering is still intact [2, 3]. For the experimentally very interesting case of sc-Brillouin we find a dependence of the efficiency on the sign of the chirp.\\[4pt] [1] G.A. Mourou, N.J. Fisch, V.M. Malkin, Z. Toroker, E.A. Khazanov, A.M. Sergeev, T. Tajima, and B. Le Garrec, Optics Communications 285, 720 (2012)\\[0pt] [2] G. Lehmann and K.H. Spatschek, Phys. Plasmas 22, 043105 (2015)\\[0pt] [3] F. Schluck, G. Lehmann, and K.H. Spatschek, Phys. Plasmas, to be published (2015) [Preview Abstract] |
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