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 TO7: Ion Acceleration and Generation and Intense Laser and Laser-plasma Physics |
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Chair: Lin Yin, Los Alamos National Laboratory Room: Governor's Square 12 |
Thursday, November 14, 2013 9:30AM - 9:42AM |
TO7.00001: Scaling on Spot Size in Laser Acceleration of Protons Using Multi-Ion Foils Tung-Chang Liu, Xi Shao, Chuan-Sheng Liu We present the numerical study of the effect of the spot size of the circularly polarized laser beam on the energy of quasi-monoenergetic protons in laser proton acceleration with a thin carbon-hydrogen foil. In this acceleration scheme, protons are accelerated by a combination of laser radiation pressure and shielded Coulomb repulsion of carbon. We observed that the spot size plays a crucial role in determining the net charge of the electron-shielded carbon ion foil and consequently the efficiency of proton acceleration. Using a laser pulse with half-sine time profile and fixed input power and energy impinging on a carbon-hydrogen foil, we found that a laser beam with smaller spot sizes can generate higher energy but fewer quasi-monoenergetic protons. We also studied the scaling of the proton energy with respect to the laser spot size and obtained an optimal spot size for maximum proton energy flux. With such an optimal spot size, we can generate a 80 MeV quasi-monoenergetic proton beam containing more than $10^8$ protons using a laser beam with power 250 TW and energy 10 J. [Preview Abstract] |
Thursday, November 14, 2013 9:42AM - 9:54AM |
TO7.00002: Survey and Optimization of Laser-Driven Ion Beams Sasikumar Palaniyappan, Juan Fernandez, Rahul Shah, Brian Albright, Jim Cobble, Donald Gautier, Chris Hamilton, Chengkun Huang, Lin Yin, Jim Williams, Bjorn Hegelich, Daniel Jung Laser-driven ion acceleration mechanisms have been studied in a series of experiments at the Trident laser facility. Access to multiple such mechanisms has been enabled by a variety of laser targets, ranging from nanofoil targets of different materials to foams that provide near-critical-density plasmas. The operative physics has been constrained by an extensive set of diagnostics, including ion spectrometers, electron spectrometers, frequency-resolved optical gating of the reflected and transmitted laser beams, and a transmitted-laser-beam profiler. Ion acceleration has been observed in both the regimes where the laser plasma remains opaque and where it becomes transparent. In some cases a measure of ion-spectral control has been demonstrated, beyond the typical Maxwellian ion distribution. Simulations have been performed to clarify our understanding of the underlying physics. In this presentation, the salient ion-beam results are shown, along with key measurements that identify the dominant acceleration mechanism. The theoretical considerations behind the observed performance optimizations are summarized. [Preview Abstract] |
Thursday, November 14, 2013 9:54AM - 10:06AM |
TO7.00003: Shock driven acceleration of impurity free ion beam using low density targets Olivier Tresca, Nicholas Dover, Nathan Cook, Chakra Maharjan, Zulfikar Najmudin, Mikhail Polyanskiy, Peter Shkolnikov, Igor Pogorelsky Recent progress in COlaser technology has allowed for the creation of intense, 10Wcm$^{-2}$, pulses at lambda $\sim$10 $\mu $m. The longer wavelength of these pulses, compare to solid state lasers, allow for the use of low density targets, $\sim$10cm$^{-3}$. In these conditions ion beams can be accelerated by a laser generated shock-wave to multi MeV energies with a narrow energy spread smaller than 10{\%}. The CO laser at the Accelerator Test Facility has the unique capability of producing single, picoseconds-scale, pulses with 1TW peak power, enabling us to study this acceleration regime in detail. The spatial density profile of the gas target has been found to be critical to the successful acceleration of ion beams. We report on recent PIC and fluid simulations results exploring the propagation of shock-wave and resulting ion acceleration for various plasma density profiles. Recent experimental results will also be discussed. [Preview Abstract] |
Thursday, November 14, 2013 10:06AM - 10:18AM |
TO7.00004: LIGHT -- from laser ion acceleration to future applications Markus Roth Creation of high intensity multi-MeV ion bunches by high power lasers became a reliable tool during the last 15 years. The laser plasma source provides for TV/m accelerating field gradients and initially sub-ps bunch lengths. However, the large envelope divergence and the continuous exponential energy spectrum are substential drawbacks for many possible applications. To face this problem, the LIGHT collaboration was founded (Laser Ion Generation, Handling and Transport). The collaboration consists of several university groups and research centers, namely TU Darmstadt, JWGU Frankfurt, HI Jena, HZDR Dresden and GSI Darmstadt. The central goal is building a test beamline for merging laser ion acceleration with conventional accelerator infrastructure at the GSI facility. In the latest experiments, low divergent proton bunches with a central energy of up to 10 MeV and containing \textgreater\ 10$^{9}$ particles could be provided at up to 2.2 m behind the plasma source, using a pulsed solenoid. In a next step, a radiofrequency cavity will be added to the beamline for phase rotation of these bunches, giving access to sub-ns bunch lengths and reaching highest intensities. An overview of the LIGHT objectives and the recent experimental results will be given. [Preview Abstract] |
Thursday, November 14, 2013 10:18AM - 10:30AM |
TO7.00005: Laser Acceleration of Proton with Multi-Ion Plasma Gaseous Targets Chuan-Sheng Liu, Tung-Chang Liu, Xi Shao We present simulation results of quasi-monoenergetic proton acceleration with a circularly polarized laser irradiating on a carbon-hydrogen target with thickness 2.5 wavelength. We show that caviton, shock and radiation pressure accelerations are initially the dominant mechanisms. After 50 laser periods, when the electrons become transparent to laser, Coulomb repulsion then becomes the leading acceleration mechanism, stably accelerating the proton layer for 150 more periods. Quasi-monoenergetic protons of 80 MeV can be obtained by a laser with normalized amplitude a = 10 and pulse duration 150 wave periods. In comparison, using similar input parameters on single-species gas target, we can only obtain proton energy less than 40 MeV. [Preview Abstract] |
Thursday, November 14, 2013 10:30AM - 10:42AM |
TO7.00006: Acceleration of Ions from a near critical density gaseous target Michael Helle, Daniel Gordon, Dmitri Kaganovich, Antonio Ting Efficient acceleration of ions by means of high power laser radiation requires electron plasma densities at or in excess of the critical density. For optical wavelengths where most of the world's high intensity lasers operate, the critical density is n$_{\mathrm{CRIT}} \approx $ 2*10$^{\mathrm{21}}$ cm$^{\mathrm{-3}}$. This value lies between gaseous and solid like densities making it difficult to obtain. In order to reach these densities a ``gas foil'' target has been developed at the Naval Research Laboratory. The target is created by igniting an optically driven hydrodynamic shock into the gas flow of a gas jet in vacuum. Experiments have shown that a laser-ignited shock is capable of producing \textless 10 $\mu $m gradients, thicknesses $\approx $ 100 $\mu $m, and peak densities \textgreater 4 times ambient. 3D PIC simulations of the interaction of an intense laser pulse with this type of thin, near critical density target have shown characteristics of the recently purposed Magnetic Vortex Acceleration mechanism. This mechanism takes advantage of an inductive accelerating field at the rear of the target. This field is generated by the strong azimuthal magnetic field produced by electrons accelerating through the target. Simulations and preliminary experimental results using the TFL laser system at NRL will be discussed. [Preview Abstract] |
Thursday, November 14, 2013 10:42AM - 10:54AM |
TO7.00007: Proton Beams from Nanotube Accelerator Masakatsu Murakami, Motohiko Tanaka A carbon nanotube (CNT) is known to have extraordinary material and mechanical properties. Here we propose a novel ion acceleration scheme with nanometer-size CNT working at such an extreme circumstance as temperatures higher than billions of degree and durations shorter than tens of femtosecond, dubbed as nanotube accelerator, with which quasimonoenergetic and collimated MeV-order proton beams are generated. In nanotube accelerators, CNTs with fragments of a hydrogen compound embedded inside are irradiated by an ultrashort ultraintense laser. Under such laser and target conditions, low-Z materials such as hydrogen and carbon will be fully ionized. Substantial amount of electrons of the system are then blown off by the brutal laser electric field within only a few laser cycles. This leads to a new type of ion acceleration, in which the nanotube and embedded materials play the roles of a gun barrel and bullets, respectively, to produce highly collimated and quasimonoenergetic proton beams. Three-dimensional particle simulations, that take all the two-body Coulomb interactions into account, demonstrate generation of quasimonoenergetic 1.5-MeV proton beams under a super-intense electrostatic field $\sim$ 10$^{14}$ V m$^{-1}$. [Preview Abstract] |
Thursday, November 14, 2013 10:54AM - 11:06AM |
TO7.00008: Simulations of Ultra-HED Plasmas Created by Femtosecond Laser Irradiation of Vertically Aligned Nanowire Arrays V.N. Shlyaptsev, A. Pukhov, M.A. Purvis, R.C. Hollinger, C. Bargsten, J.J. Rocca We discuss PIC, hydrodynamic, atomic, and radiation transport modeling results of a new approach for the creation of ultra-high energy density multi-Gbar pressure plasmas in the ultrasonic heating regime utilizing femtosecond laser pulse irradiation of vertically aligned nanowire arrays. This regime, initially proposed for sub-critical density plasmas (foam, gas etc targets) and successfully used with large energy ns-duration lasers, was realized here with fs laser pulses by irradiating arrays of vertically aligned metal nanowires which allowed penetration and dissipation of laser radiation in densities 100x the critical density. This leads to the formation of almost classical plasmas that are simultaneously hot and dense, and to the generation of ultra-high pressures and extreme degrees ionizations (eg. Au $+$52). Applications of such plasma to the efficient generation of a point source of short duration multi-keV X-rays and atomic physics studies will be discussed. [Preview Abstract] |
Thursday, November 14, 2013 11:06AM - 11:18AM |
TO7.00009: Ultra-High Energy Density Relativistic Plasmas by Ultrafast Laser Irradiation of Aligned Nanowire Arrays J.J. Rocca, M.A. Purvis, V.N. Shlyaptsev, R.C. Hollinger, C. Bargsten, A. Pukhov, D. Keiss, A. Townsend, A. Prieto, Y. Wang, L. Yin, S. Wang, B. Luther, M. Woolston Long-lived plasmas that are simultaneously dense and hot (multi-keV) have been created by spherical compression with the world's largest lasers, and by supersonic heating of volumes with densities on the order of N$_{ec}$ using multi-kJ lasers pulses. We demonstrate volumetric heating of near-solid density plasmas to keV temperatures using ultra-high contrast $\lambda =$ 400 nm femtosecond laser pulses of only 0.5 J energy to irradiate arrays of vertically aligned nanowires with 12{\%} average solid density. X-ray spectra show that irradiation of Ni and Au nanowires arrays with relativistic intensities ionizes plasma volumes several micrometers in depth to the He-like and Co-like (Au 52$+)$ stages respectively. He-$\alpha $ line emission greatly exceeds that of the Ni K$\alpha $ line. This volumetric plasma heating approach creates a new laboratory plasma regime in which extreme plasma parameters can be accessed with table-top lasers. The increased hydrodynamic-to-radiative lifetime ratio is responsible for a great increase in the x-ray emission. [Preview Abstract] |
Thursday, November 14, 2013 11:18AM - 11:30AM |
TO7.00010: Interaction of relativistic laser pulses with near-critical density plasma L. Willingale, C. Zulick, F.J. Dollar, A. Maksimchuk, Z. Zhao, G.J. Williams, H. Chen, A.U. Hazi, E. Marley, W. Nazarov We perform fundamental studies using the relativistic-intensity Titan laser (LLNL) interacting with very low-density foam targets, to study a near-critical density plasma. The interactions are characterized through simultaneous measurements of electron and proton spectra and beam divergence, the reflected and transmitted optical light and the generated x-ray radiation. Trends with plasma density are cross-correlated across different diagnostics to investigate the transition electron heating mechanisms and channeling behavior. Two dimensional particle-in-cell simulations are performed to give better physical understanding of these phenomenon. [Preview Abstract] |
Thursday, November 14, 2013 11:30AM - 11:42AM |
TO7.00011: Effects of strong radiation reaction and quantum-electrodynamics on relativistic transparency Peng Zhang, A.G.R. Thomas, C.P. Ridgers Relativistic transparency is the process that optically switches the overdense plasma from opaque to transparent and enables light propagation through the otherwise opaque plasma, when light of sufficient intensity drives the electrons in the plasma to near light speeds. We study the relativistic transparency in radiation dominant and strong quantum electrodynamic (QED) regime, for the interaction of high-intensity laser pulses with a thin foil solid target. We analytically study the simplified motion of an electron in a circularly polarized plane wave to understand the physics of the transmissivity and absorption in the presence of classical and quantum-corrected, semiclassical radiation-reaction forces and the trapping of particles in nodes of laser standing wave through radiative cooling. These arguments are supported by both one dimensional and two dimensional particle-in-cell calculations including strong field QED effects. Measurement of the transmission of these pulses would be experimentally feasible and a robust test of the strong field QED particle-in-cell framework. [Preview Abstract] |
Thursday, November 14, 2013 11:42AM - 11:54AM |
TO7.00012: Intense light pulses generated by parametric instabilities in laser-plasma interaction Caterina Riconda, Stefan Weber, Julien Fuchs, Livia Lancia, Jean-Raphael Marqu\`es, G\'erard Mourou Due to their extremely high damage threshold, plasmas can sustain much higher light intensities than conventional solid state optical materials. Because of this lately much attention has been devoted to the possibility of using parametric instabilities in plasmas to generate very intense light pulses. Alternative to short-pulse amplification based on the Raman approach, it is shown that using Brillouin in the so called strong-coupling regime (sc-SBS) has several advantages and is well suited to amplify and compress laser seed pulses on short distances to high intensities. We present here recent multi-dimensional kinetic simulations that show the feasibility of achieving amplified light pulses with high efficiency. Shaping the plasma and extending the laser beams diameter allows for effective energy transfer from the pump to the seed while minimizing other unwanted plasma processes. In order to obtain amplification to of up to $10^{18}$\, W/cm$^2$, we reduced the pulse duration of the initial seed to the order of ten femtoseconds. As the seed is amplified, the spectrum of the seed evolves and changes considerably so that it cannot be explained anymore by sc-SBS only: a mixing between SRS- and SBS-aspects (mixed mode regime) takes place. [Preview Abstract] |
Thursday, November 14, 2013 11:54AM - 12:06PM |
TO7.00013: Efficient laser pulse amplification by stimulated Brillouin scattering Peter Norreys, E. Guillaume, K. Humphrey, H. Nakamura, R.M.G.M. Trines, R. Bingham The energy transfer by stimulated Brillouin backscatter from a long pump pulse (15 ps) to a short seed pulse (1 ps) has been investigated in a proof-of-principle experiment. The two pulses were both amplified in different beamlines of a Nd:glass laser system, had a central wavelength of 1054 nm and a spectral bandwidth of 2 nm, and crossed each other in an underdense plasma in a counter-propagating geometry, off-set by 10 degrees. It is shown that the amplification factor and the wavelength of the generated Brillouin peak depends on the plasma density, the intensity of the laser pulses and the competition between two-plasmon decay and stimulated Raman scatter instabilities, by comparison with particle-in-cell simulations. The highest obtained energy transfer from pump to probe pulse was 2.5{\%}, at a plasma density of 0.17ncr, and this energy transfer increases significantly with plasma density. The results suggest that much higher efficiencies can be obtained when higher densities (above 0.25ncr) are used in future experiments. This work was done in Collaboration with IST, Imperial College, Queens University Belfast, Osaka University {\&} University of Cambridge [Preview Abstract] |
Thursday, November 14, 2013 12:06PM - 12:18PM |
TO7.00014: Laser Driven Neutron Generation at the Texas Petawatt Ishay Pomerantz, Eddie McCary, Alexander R. Meadows, Arantxa Cepeda Lestrade, Clay Chester, Jose Cortez, Gilliss Dyer, Erhard Gaul, Donald C. Gautier, David Hamilton, Daniel Jung, Rahul Shah, Chunhua Wang, Juan C. Fernandez, Todd Ditmire, Manuel Bjorn Hegelich We realized a bright laser-driven neutron source at the Texas Petawatt laser facility. We investigated the interplay between ion- and x-ray- driven neutron production regimes, by scanning a large range of target thicknesses, converter materials and laser parameters. We employed a large suite of electron, ion, gamma and neutron diagnostics to obtain a complete characterization of the interaction energetics. Neutron yields in excess of 10$^{9}$ neutrons/shot with a fairly isotropic distribution were measured. [Preview Abstract] |
Thursday, November 14, 2013 12:18PM - 12:30PM |
TO7.00015: Self-consistent PIC modeling of pair production with intense lasers pulses Thomas Grismayer, Ricardo Fonseca, Mattias Marklund, Luis Silva The availability of powerful lights sources offers in principle new possibilities for investigation of various quantum processes. Peak intensities up to 10$^{22}$ W/cm$^2$ are already available in some laser facilities and even greater intensity should be attainable with the development of the ELI project. Among various quantum phenomena, electron-positron pair production, at the focus of an intense laser, is currently a topic of considerable interest. As is typical for particle scattering experiments, many different processes may contribute to the final yields of pairs. Out of the possible mechanisms, pair production seeded by an electron is likely to be the most dominant at lower intensities. In this work, we include the two-step process (non linear Compton scattering $+$ Breit-Wheeler) in a massively parallel PIC code (using the Osiris 2.0 framework) via a Monte Carlo module, focusing on implementing in a self-consistent manner and multi-dimensions the interaction of the intense fields with the pair plasma dynamics. As an illustration we have investigated the pair cascades initiated by a single electron in counter-propagating lasers pulses for ELI parameters. The numerical results are also compared with analytical results. [Preview Abstract] |
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