Bulletin of the American Physical Society
59th Annual Meeting of the APS Division of Plasma Physics
Volume 62, Number 12
Monday–Friday, October 23–27, 2017; Milwaukee, Wisconsin
Session GO5: Laser Acceleration of Protons and Ions |
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Chair: Farhat Beg, University of California, San Diego Room: 202AB |
Tuesday, October 24, 2017 9:30AM - 9:42AM |
GO5.00001: Controlling laser-ion acceleration with chirped pulses Felix Mackenroth, Arkady Gonoskov, Mattias Marklund The recently proposed novel laser-ion acceleration scheme \textit{Chirped-standing-wave acceleration} (CSWA) makes use of chirped high-intensity laser pulses to gain enhanced control over the accelerated ions' phase space distribution. The first proof-of-principle analysis of this scheme promised favorable scaling properties of ion energies and densities while simultaneously offering unprecedented spatial and temporal control over the ion beam itself. In this talk we provide an extended analysis of the schemes' further capabilities accessible through, e.g., customized laser chirps and targets. We provide quantitative estimates for existing and upcoming experimental facilities to highlight the scheme's versatility. Furthermore, we benchmark the newly proposed scheme against conventional laser-ion acceleration schemes. To this end we use the accelerated ions' flux as a measure for the conversion efficiency of laser energy into ion kinetic energy and provide a systematic comparison of the theoretically achievable performances of the most common laser-ion acceleration schemes. We find CSWA to be highly competitive in terms of reachable ion energies and fluxes. [Preview Abstract] |
Tuesday, October 24, 2017 9:42AM - 9:54AM |
GO5.00002: Proton acceleration in laser-driven megatesla magnetic fields Alexey Arefiev, S. S. Bulanov, T. Toncian The next generation of laser facilities will make it possible to access laser intensities well beyond $10^{22}$ W⁄cm$^2$. At these intensities, a laser pulse would rapidly energize electrons, making them ultra-relativistic and rendering an otherwise opaque solid material transparent. This phenomenon of relativistically-induced transparency enables a volumetric interaction between the intense laser pulse and the irradiated solid-density matter. Recent 3D simulations of this regime have demonstrated that a laser pulse can drive an unprecedented quasi-static MT-level magnetic field inside the solid-density material [Stark, Toncian, Arefiev, PRL 116, 185003 (2016)]. This talk will present a novel regime for ion acceleration enabled by the MT-level magnetic field. If the laser pulse is able to burn through a massive target, then the electrons exiting the target with the laser pulse generate a field structure that produces dense mono-energetic proton bunches (20 nC in charge and 250 MeV in energy) by an acceleration mechanism not encountered before in experimental and analytical studies [S. S. Bulanov et al. PoP 23, 056703 (2016)]. [Preview Abstract] |
Tuesday, October 24, 2017 9:54AM - 10:06AM |
GO5.00003: Achieving Stable Radiation Pressure Acceleration of Heavy Ions via Successive Electron Replenishment from Ionization of a High-Z Material Coating Bin Qiao, X. F. Shen, H. Zhang, S. Kar, C. T. Zhou, H. X. Chang, M. Borghesi, X. T. He Among various laser-driven acceleration schemes, radiation pressure acceleration (RPA) is regarded as one of the most promising schemes to obtain high-quality ion beams. Although RPA is very attractive in principle, it is difficult to be achieved experimentally. One of the most important reasons is the dramatic growth of the multi-dimensional Rayleigh-Taylor-like (RT) instabilities. In this talk, we report a novel method to achieve stable RPA [2,3] of ions from laser-irradiated ultrathin foils, where a high-Z material coating in front is used. The coated high-Z material, acting as a moving electron repository, continuously replenishes the accelerating ion foil with comoving electrons in the light-sail acceleration stage due to its successive ionization under laser fields with Gaussian temporal profile. As a result, the detrimental effects such as electron loss induced by the RT and other instabilities are significantly offset and suppressed so that stable acceleration of ions are maintained. [1] B. Qiao et al., PRL 108, 115002 (2012); [2] X. F. Shen, B. Qiao* et al., PRL 118, 204802 (2017); [3] X. F. Shen, B. Qiao* et al., NJP 19, 033034 (2017). [Preview Abstract] |
Tuesday, October 24, 2017 10:06AM - 10:18AM |
GO5.00004: Controllable robust laser driven ion acceleration from near-critical density relativistic self-transparent plasma Bin Liu, Juergen Meyer-ter-Vehn, Hartmut Ruhl We introduce an alternative approach for laser driven self-injected high quality ion acceleration. We call it ion wave breaking acceleration [1]. It operates in relativistic self-transparent plasma for ultra-intense ultra-short laser pulses. Laser propagating in a transparent plasma excites an electron wave as well as an ion wave. When the ion wave breaks, a fraction of ions is self-injected into the positive part of the laser driven wake. This leads to a superior ion pulse with peaked energy spectra; in particular in realistic three-dimensional geometry, the injection occurs localized close to the laser axis producing highly directed bunches. A theory is developed to investigate the ion wave breaking dynamics. Three dimensional Particle-in-Cell simulations with pure-gaussian laser pulses and pre-expanded near-critical density plasma targets have been done to verify the theoretical results. It is shown that hundreds of MeV, easily controllable and manipulable, micron-scale size, highly collimated and quasi-mono-energetic ion beams can be produced by using ultra-intense ultra-short laser pulses with total laser energies less than 10 Joules. Such ion beams may find important applications in tumour therapy. Reference: [1] B. Liu, et.al., Phys. Rev. Accel. Beams 19, 073401 (2016). [Preview Abstract] |
Tuesday, October 24, 2017 10:18AM - 10:30AM |
GO5.00005: Effects of dimensionality and laser polarization on kinetic simulations of laser-ion acceleration in the transparency regime David Stark, Lin Yin, Brian Albright, Fan Guo The often cost-prohibitive nature of three-dimensional (3D) kinetic simulations of laser-plasma interactions has resulted in heavy use of two-dimensional (2D) simulations to extract physics. However, depending on whether the polarization is modeled as 2D-S or 2D-P (laser polarization in and out of the simulation plane, respectively), different results arise. In laser-ion acceleration in the transparency regime, VPIC particle-in-cell simulations show that 2D-S and 2D-P capture different physics that appears in 3D simulations. The electron momentum distribution is virtually two-dimensional in 2D-P, unlike the more isotropic distributions in 2D-S and 3D, leading to greater heating in the simulation plane. As a result, target expansion time scales and density thresholds for the onset of relativistic transparency differ dramatically between 2D-S and 2D-P [1]. The artificial electron heating in 2D-P exaggerates the effectiveness of target-normal sheath acceleration (TNSA) into its dominant acceleration mechanism, whereas 2D-S and 3D both have populations accelerated preferentially during transparency to higher energies than those of TNSA. [1] D. J. Stark, L. Yin, B. J. Albright, and F. Guo. Phys. Plasmas 24, 053103 (2017). [Preview Abstract] |
Tuesday, October 24, 2017 10:30AM - 10:42AM |
GO5.00006: Stable quasi-monoenergetic ion acceleration from the laser-driven shocks in a collisional plasma Shikha Bhadoria, Naveen Kumar, Christoph H. Keitel Effect of collisions on the shock formation and subsequent ion acceleration from the laser-plasma interaction is explored by the means of particle-in-cell simulations. In this setup, the incident laser pushes the laser-plasma interface inside the plasma target through the hole-boring effect and generates hot electrons. The propagation of these hot electrons inside the target excites a return plasma current, leading to filamentary structures caused by the Weibel/filamentation instability. Weakening of the space-charge effects due to collisions results in the shock formation with a higher density jump than in a collisionless plasma. This results in the formation of a stronger shock leading to a stable quasi-monoenergetic acceleration of ions. [Preview Abstract] |
Tuesday, October 24, 2017 10:42AM - 10:54AM |
GO5.00007: Spatiospectral Analysis of Accelerated Protons from Sub-Micron Liquid Crystal Films Christopher Willis, Patrick Poole, Ginevra Cochran, Linn Van Woerkom, Douglass Schumacher Recent studies on ion acceleration have trended towards ultra-thin (\textless 1 $\mu $m) targets due to improved ion energies and yields from these targets. As discussed here, ultra-thin targets may exhibit unusual spatial distributions in the accelerated ions, such that ion spectrometer data may not be representative of the overall distribution. More complete characterization of the ions requires spectral unfolding of radiochromic film (RCF) data, yielding spatially dependent spectra. Spatiospectral data will be presented from several experiments using sub-micron liquid crystal film targets at the Scarlet (OSU), Texas Petawatt (UT, Austin) and PHELIX (GSI, Darmstadt) laser facilities, including evidence of \textgreater 75 MeV protons from \textasciitilde 300 nm films at PHELIX. Analysis of RCF data is supported by Monte-Carlo modeling of RCF response to ions and electrons using FLUKA. Trends in the resulting ion distributions will be discussed including spatially varying slope temperature and observation of annular ring features at moderate ion energies on many shots. [Preview Abstract] |
Tuesday, October 24, 2017 10:54AM - 11:06AM |
GO5.00008: High peak current acceleration of narrow divergence ions beams with the BELLA-PW laser Sven Steinke, Qing Ji, Franziska Treffert, Stepan Bulanov, Jianhui Bin, Kei Nakamura, Anthony Gonsalves, Csaba Toth, Jaehong Park, Markus Roth, Eric Esarey, Thomas Schenkel, Wim Leemans We present a parameter study of ion acceleration driven by the BELLA-PW laser. The laser repetition rate of 1Hz allowed for scanning the laser pulse duration, relative focus location and target thickness for the first time at laser peak powers of above 1 petawatt. Further, the long focal length geometry of the experiment (f\textbackslash 65) and hence, large focus size provided ion beams of reduced divergence and unprecedented charge density. [Preview Abstract] |
Tuesday, October 24, 2017 11:06AM - 11:18AM |
GO5.00009: Generation of narrow energy spread ion beams via collisionless shock waves using ultra-intense 1 um wavelength laser systems Felicie Albert, A. Pak, S. Kerr, N. Lemos, A. Link, P. Patel, B. B. Pollock, D. Haberberger, D. Froula, M. Gauthier, S. H. Glenzer, A. Longman, L. Manzoor, R. Fedosejevs, S. Tochitsky, C. Joshi, F. Fiuza In this work, we report on electrostatic collisionless shock wave acceleration experiments that produced proton beams with peak energies between 10-17.5 MeV, with narrow energy spreads between $\Delta $ E / E of 10-20 {\%}, and with a total number of protons in these peaks of 1e7-1e8.~ These beams of ions were created by driving an electrostatic collisionless shock wave in a tailored near critical density plasma target using the ultra-intense ps duration Titan laser that operates at a wavelength of 1 um.~ The near critical density target was produced through the ablation of an initially 0.5 um thick Mylar foil with a separate low intensity laser. ~ A narrow energy spread distribution of carbon / oxygen ions with a similar velocity to the accelerated proton distribution, consistent with the reflection and acceleration of ions from an electrostatic field, was also observed. [Preview Abstract] |
Tuesday, October 24, 2017 11:18AM - 11:30AM |
GO5.00010: Near-critical density target experiments for ion acceleration using high-intensity laser pulses Peter Kordell, Paul Campbell, Anatoly Maksimchuk, Louise Willingale, Karl Krushelnick The interaction of a short-duration, relativistic intensity laser pulse with a near-critical density plasma can produce a collisionless electrostatic shock capable of accelerating ions. This effect has already been demonstrated using CO2 laser systems ($\lambda = 10 \; \mu \rm{m}$) where the specific plasma density profile enabled the acceleration of quasi-monoenergetic ion beams. We will present our experiments using the T-cubed laser system at the University of Michigan ($\lambda = 1.053 \; \mu \rm{m}$, 6J, 400fs). Due to the shorter wavelength, typical of most relativistic intensity laser systems, a higher plasma density and shorter scalelengths are required to achieve the conditions for shock ion acceleration. The target design and characterization as well as preliminary experimental results will be presented. [Preview Abstract] |
Tuesday, October 24, 2017 11:30AM - 11:42AM |
GO5.00011: High repetition rate laser-driven MeV ion acceleration at variable background pressures Joseph Snyder, Gregory Ngirmang, Chris Orban, Scott Feister, John Morrison, Kyle Frische, Enam Chowdhury, W. M. Roquemore Ultra-intense laser-plasma interactions (LPI) can produce highly energetic photons, electrons, and ions with numerous potential real-world applications. Many of these applications will require repeatable, high repetition targets that are suitable for LPI experiments. Liquid targets can meet many of these needs, but they typically require higher chamber pressure than is used for many low repetition rate experiments. The effect of background pressure on the LPI has not been thoroughly studied. With this in mind, the Extreme Light group at the Air Force Research Lab has carried out MeV ion and electron acceleration experiments at kHz repetition rate with background pressures ranging from 30 mTorr to \textgreater 1 Torr using a submicron ethylene glycol liquid sheet target. We present these results and provide two-dimensional particle-in-cell simulation results that offer insight on the thresholds for the efficient acceleration of electrons and ions. [Preview Abstract] |
Tuesday, October 24, 2017 11:42AM - 11:54AM |
GO5.00012: Ultrathin Target Laser Ion Acceleration At Oblique Incidence G.E. Cochran, P.L. Poole, T. Cowan, T. Kluge, J. Metzkes, L. Obst, I. Principe, H.-P. Schlenvoigt, U. Schramm, K. Zeil, D.W. Schumacher Oblique laser incidence allows separate identification of target normal and laser axis ion acceleration mechanisms. A recent high-contrast experiment using the Draco laser ($\sim$3 J, $10^{21}$ $W/cm^2$) at 45 degrees angle of incidence on liquid crystal targets showed predominantly target normal directed ions for all target thicknesses from 10 $nm$ to $>$ 1 $\mu$m, with peak proton energies up to 26 MeV. We present 3D particle-in-cell simulations of this experiment which reproduce both the dominance of target normal acceleration as well as the transparency onset as a function of target thickness, with ion spectral and optical reflectivity trends in agreement with experimental observations. We find that high energy ions from the thinnest targets are accelerated volumetrically, in contrast to originating at the rear surface as in thicker targets. We discuss the acceleration mechanisms at play and the dominance of target normal ions. [Preview Abstract] |
Tuesday, October 24, 2017 11:54AM - 12:06PM |
GO5.00013: Ion acceleration via TNSA near and beyond the relativistic transparency limit Douglass Schumacher, Patrick Poole, Ginevra Cochran, Christopher Willis Ultra-intense laser-based ion acceleration can proceed via several mechanisms whose fundamental operation and interplay with each other are still not well understood. The details of Relativistically Induced Transparency (RIT) and its impact on ultra-thin target acceleration are of interest for fundamental studies and to progress toward applications requiring controlled, high energy secondary radiation, e.g. hadron cancer therapy. Liquid crystal film targets formed in-situ with thickness control between 10 nm and $>$ 50 $\mu$m uniquely allow study of how ion acceleration varies with target thickness. Several recent studies have investigated Target Normal Sheath Acceleration (TNSA) down to the thickness at which RIT occurs, with a wide range of laser conditions (energy, pulse duration, and contrast), using various ion and optical diagnostics to ascertain acceleration mechanisms and quality. Observation of target-normal directed ion acceleration enhancement at the RIT thickness onset will be discussed, including analysis of ion spatial and spectral features as well as particle-in-cell simulations investigating the underlying physical processes. [Preview Abstract] |
Tuesday, October 24, 2017 12:06PM - 12:18PM |
GO5.00014: Mono-energetic ion beams accelerated in the interaction of an ultrashort intense laser with ultra-thin solid targets Jun Li, Alexey Arefiev, Christopher Mcguffey, Farhat Beg We performed particle-in-cell (PIC) simulations to study the ion acceleration by the interaction of an ultra-short(35fs) intense laser (10$^{\mathrm{20}}$W/cm$^{\mathrm{2}})$ with ultra-thin(6-100nm) copper targets. We aimed at investigating how ions are accelerated from thin targets, and focus on the regime in which targets remain intact and not broken through by the laser pulse. The target thicknesses were scanned, and we found that the ionization of copper ions to high Z states occurred during the acceleration. The mono-energetic high Z ion beams were observed only for the target thickness of 20nm with energies near 400 MeV. We conducted the particle tracking diagnostic to study the underline physics and mechanism of the acceleration, and the details will be presented in the meeting. This work was performed using HPC resources provided by the Texas Advanced Computing Center at the University of Texas; This work also used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant number ACI-1548562. [Preview Abstract] |
Tuesday, October 24, 2017 12:18PM - 12:30PM |
GO5.00015: Proton and Ion Acceleration using Multi-kJ Lasers S. C. Wilks, T. Ma, A. J. Kemp, M. Tabak, A. J. Link, C. Haefner, M. R. Hermann, D. A. Mariscal, S. Rubenchik, P. Sterne, J. Kim, C. McGuffey, K. Bhutwala, F. Beg, M. Wei, S. M. Kerr, Y. Sentoku, N. Iwata, P. Norreys, A. Sevin Short ( \textless 50 ps) laser pulses are capable of accelerating protons and ions from solid (or dense gas jet) targets as demonstrated by a number of laser facilities around the world in the past 20 years accelerating protons to between 1 and 100 MeV, depending on specific laser parameters. Over this time, a distinct scaling with energy has emerged that shows a trend towards increasing maximum accelerated proton (ion) energy with increasing laser energy. We consider the physical basis underlying this scaling, and use this to estimate future results when multi-kJ laser systems begin operating in this new high energy regime. In particular, we consider the effects of laser prepulse, intensity, energy, and pulse length on the number and energy of the ions, as well as target size and composition. We also discuss potential uses of these ion beams in High Energy Density Physics Experiments. This work was performed under the auspices of the U.S. Department of Energy (DOE) by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and funded by the LLNL LDRD program under tracking code 17-ERD-039. [Preview Abstract] |
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