Bulletin of the American Physical Society
60th Annual Meeting of the APS Division of Plasma Physics
Volume 63, Number 11
Monday–Friday, November 5–9, 2018; Portland, Oregon
Session PO8: Relativistic Laser Plasma Interaction and Particles (ions, electrons, positrons, neutrons) III |
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Chair: Louise Willingale, University of Michigan Room: OCC C120-122 |
Wednesday, November 7, 2018 2:00PM - 2:12PM |
PO8.00001: Sustainable High Repetition Rate Plasma Mirrors for Petawatt Lasers Anthony Zingale, Sven Steinke, Jianhui Bin, Ginevra E Cochran, Christopher V Pieronek, Jeroen Van Tilborg, Fumika Isono, Samuel Barber, Nick Czapla, Jordan Purcell, Patrick L. Poole, Wim Pieter Leemans, Douglass W Schumacher Free standing liquid crystal films have shown utility as moderate repetition rate plasma mirrors in ultra-high intensity laser matter interactions (Poole et al., Scientific Reports 6, 32041 (2016)). We report the results of a test of film durability in the BELLA gas capillary electron acceleration environment (Leemans, et al., PRL 113, 245002 (2014)). It was found that films as thin as 10 nm can withstand blow-out plasma 6 cm from the capillary discharge as well as the peak of a nanosecond laser pulse with a fluence of ~400 J/cm2 used for heating. These results inform the suitability of liquid crystal films for short laser pulse redirection in wakefield electron accelerators. A new high repetition rate device (> 1 Hz) is described for inserting 10-30 nm thick plasma mirrors with low weak field reflectivity, good film uniformity, flatness, pointing, and low cost. The design innovations necessary to achieve this performance are described. |
Wednesday, November 7, 2018 2:12PM - 2:24PM |
PO8.00002: Plasma Mirrors as Optical Components for the Manipulation of Intense Light Matthew R Edwards, Tim Bennett, Alec Griffith, Nicholas Fasano, Bradley O'Brien, Nikita Turley, Julia Mikhailova The replacement of standard optical components with a toolkit of plasma-based optics allows the construction of compact high-peak-power laser systems. Plasma mirrors form a key part of this toolkit, permitting reflection of relativistic intensities, temporal contrast and spatial mode cleaning, and the efficient generation of harmonics of the initial laser pulse. We characterize the emission of upshifted frequencies from plasma mirrors into the relativistic regime both experimentally, with a 25 fs, 400 mJ laser system, and with particle-in-cell simulations across a broad range of parameters, showing in particular how sequences of cascaded plasma mirrors can improve beam quality and the efficiency of harmonic generation. |
Wednesday, November 7, 2018 2:24PM - 2:36PM |
PO8.00003: Time and Space-Resolved Thermometry Using Neutron Resonance Spectroscopy (NRS): Requirements and Prospects for Laser-Driven Neutron Sources Juan Carlos Fernandez, Cris William Barnes, Michael Jeffrey Mocko, Lukas Zavorka Neutron spallation sources have enabled localized volumetric (bulk) thermometry of materials based on NRS. Temperature, an independent thermodynamic variable in the equations of state, is needed to validate theoretical models of condensed and warm-dense matter. Yet bulk thermometry of materials under transient extreme conditions is an unmet scientific need due to the difficulty of dynamic measurements and of co-locating dynamic drivers at a spallation facility. Thus NRS thermometry of dynamic materials has been reported only once [1]. Alternatives to NRS have drawbacks or are inapplicable. More compact neutron sources would enable dynamic bulk NRS thermometry. Ultrafast high-intensity optical lasers may deliver such a source. To evaluate such possibilities, we determine the sensitivities of the temperature estimate on neutron-beam and diagnostic parameters. Based on those, requirements are set on a pulsed neutron-source and diagnostics to make a meaningful dynamic measurement. Forward MCNP6 calculations of fast-neutron generation with lasers are discussed. With a high-intensity high-contrast ultrafast laser pulse of sufficient energy (~ a few hundred Joules), a suitable compact neutron source is within reach. [1] V. W. Yuan, et al., PRL 94, 125504 (2005) |
Wednesday, November 7, 2018 2:36PM - 2:48PM |
PO8.00004: Deuteron acceleration in nanowire arrays irradiated at highly relativistic intensities Alden H Curtis, Chase N Calvi, Shoujun Wang, Yong Wang, Alex Rockwood, Reed Hollinger, Adam Moreau, Vyacheslav Shlyaptsev, Stephen Kasdorf, Vural Kaymak, Alexander Pukhov, Jorge Rocca The irradiation of arrays of aligned deuterated polyethylene nanowires (CD2) with ultra-high contrast femtosecond laser pulses of relativistic intensity was recently shown to accelerate deuterons to multi-MeV energy and to efficiently produce quasi-monoenergetic fusion neutrons [1]. The number of fusion neutron produced exceeds by > 500 times that produced by irradiating flat solid CD2 targets under the same conditions. Those experiments were conducted at irradiation intensities below 1 x 10 20 W cm-2 . Here we present the first results of deuteron acceleration from nanowire experiments conducted at irradiation intensities of ~ 2x1021 W cm-2. The deuterons are measured to be accelerated to energies of several tens of MeVs and to be emitted in a cone of approximately 10 degrees half-angle. 3-D fully relativistic particle in cell computations are used to elucidate the mechanisms of ions acceleration in the nanowire arrays. 1. Alden Curtis, C. Calvi, J. Tinsley, R. Hollinger, V. Kaymak, A. Pukhov, S. Wang, A. Rockwood, Y. Wang, V.N. Shlyaptsev, J.J. Rocca, “Micro-Scale Fusion in Dense Relativistic Nanowire Array Plasmas”, Nat. Commun. 9, 1077 (2018) |
Wednesday, November 7, 2018 2:48PM - 3:00PM |
PO8.00005: Unstable expansion of plasma foils irradiated by circularly-polarized laser pulses in non-transparent regimes Teyoun Kang, Young-Kuk Kim, Min Sup Hur A new instability has been observed in one-dimensional (1D) particle-in-cell (PIC) simulations. Plasma foils, irradiated by circularly-polarized (CP) laser pulses, were observed to expand even when aI < ζe, which is the conventional condition of the stable laser-foil interactions. We derived a modified condition aI < ζe / (1 + kL2de2)1/2, where de is the thickness of the foil, by assuming slab-like plasma distributions. The modified stability condition shows excellent agreement with the simulation results; stable interactions satisfied the new condition while the instability didn't. In this talk we present the derivation of the equation, and its comparison with 1D PIC simulations. We also suggest a criterion of the pulse duration to prevent the unstable expansion. Furthermore, thresholds for the instability and the self-induced transparency of the foil, and its physical meaning will be discussed. |
Wednesday, November 7, 2018 3:00PM - 3:12PM |
PO8.00006: Temporally Resolved Optical Probing of Laser Propagation in Underdense and Near-Critical Density Plasmas on Picosecond Timescales Zoë E Davidson, Ross J Gray, Adam Higginson, Bruno Gonzalez-Izquierdo, Samuel D R Williamson, Martin King, Damon Farely, Kate L Lancaster, Emer Montgomery, David Neely, Paul McKenna Experimentally probing the fast evolving nature of intense, short pulse laser-plasma interactions remains an important challenge that is crucial to understanding interaction dynamics. Transverse optical probe techniques are commonly used to characterise changes to plasma density and ionisation induced in plasma at a single point in time. Building a profile of these characteristics evolving requires many repeat shots over which the probe time is varied. This approach is inherently susceptible to shot-to-shot variations in the drive laser parameters and therefore can fail to provide reliable insight into the evolution of the interaction. Using a new 4-channel optical probe, with picosecond temporal resolution, we demonstrate 2D multi-frame measurements of plasma processes from a single intense laser pulse. In an experiment using the Vulcan laser system at the Rutherford Appleton Laboratory, we have applied this new approach to investigate intense laser propagation in underdense and near-critical density plasmas. The development of this diagnostic technique will be presented, together with results from an investigation into the dynamics of laser self-focusing and filamentation in an underdense plasma. |
Wednesday, November 7, 2018 3:12PM - 3:24PM |
PO8.00007: Highly collimated electron acceleration by longitudinal laser fields in a hollow channel Zheng Gong, Alex Robinson, Oliver Jansen, Tao Wang, Alexey Arefiev A longitudinal electric field is associated with the transverse profile of a laser pulse. Exploiting this longitudinal laser electric field, a novel mechanism to achieve collimated super-ponderomotive electron acceleration is proposed. To realize efficient acceleration, a tailored hollow-core target is used to suppress diffraction and enhance the longitudinal laser electric field. In addition, this structure eliminates the net restoring force that produces transverse electron oscillations in laser-generated ion channels, allowing for improved collimation of accelerated electrons. We use two-dimensional particle-in-cell simulation to demonstrate how energy is transferred from the laser to the electrons. |
Wednesday, November 7, 2018 3:24PM - 3:36PM |
PO8.00008: Control of fast electron propagation in plastic foam by doping high-Z elements Xiaohu Yang, Han Xu, Yanyun Ma, Chuang Ren Fast electron propagation in foam target is studied by a newly developed hybrid particle-in-cell (PIC)/fluid simulation code named HEETS. The code employs an explicit time-stepping approach, treats the fast electrons by a standard, relativistic PIC method (including scattering and drag by the background plasmas), and models the background plasma as a collisional fluid. A scheme of doping high-Z elements (like bromine (Br)) into low-Z target (polystyrene foam) in order to confine ultraintense laser-driven fast electron propagation in target is proposed. It is found that fast electrons can be confined better in doped target compared to that in pure low-Z target, attributing to its increasing resistivity and density, which induce an intenser resistive magnetic field to collimate the fast electron propagation. The increase of energy deposition in targets is slightly for doped targets, suggesting that it is suitable for long propagation of fast electrons. The scheme is also effective for fast electrons driven by higher laser intensities, like intensity required by fast ignition (I = 1020W/cm2). The results here should be helpful for the applications of ultraintense laser-driven fast electrons.
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Wednesday, November 7, 2018 3:36PM - 3:48PM |
PO8.00009: Enhanced electron generation in near-critical density plasma lens Yue Yang, Zhimeng Zhang, Jinlong Jiao, Weimin Zhou, Leifeng Cao, Yuqiu Gu, Zongqing Zhao The X-ray source based on ultraintense laser-plasma interactions has been widely applied in various fields. To meet the demand of high-resolution imaging for high-areal-density objects, the generation of bright micro-spot high-energy X-rays is urgently desired. Since the electrons accelerated in solid and gas plasmas are respectively limited in energy and yield, near-critical density (NCD) plasma lens is proposed based on the self-focusing effect to optimize the laser state, improve the energy conversion and get high-charge energetic electrons. By theoretical estimate and simulations, we prove that enhanced laser focusing in the self-formed NCD channel can contribute to the efficient energy absorption, thus producing near-μC multi-MeV electrons via direct laser acceleration mechanism. These findings offer a feasible access to the generation of micro-spot brilliant bremsstrahlung source, hopeful to realize the single-pulse transient imaging. Moreover, the production of tightly-focused, high-intensity laser pulse is of significant importance to related experimental researches and potential applications. |
Wednesday, November 7, 2018 3:48PM - 4:00PM |
PO8.00010: Decay of electron beam current in the presence of relativistically intense space charge wave Roopendra Singh Rajawat, Sudip Sengupta A numerical study of evolution of plasma electrons propagating as a beam against a background of cold homogeneous immobile ions in the presence of a relativistically intense space charge wave, has been carried out using 1D relativistic particle-in-cell code. It is observed that the electron beam current diminishes with time when perturbed longitudinally by imposing a relativistically intense wave. This novel effect is attributed to phase mixing phenomena arising because of variation of relativistic electron mass. Study has been conducted for various values of flow velocities (v0/c) and relativistic intensities (eE0/mωpec) of the perturbed wave. It is found that the rate of decrease of current decreases with increasing flow velocity and increases with increasing wave intensity. An analytical study of evolution of relativistic electron beam propagating through a cold homogeneous plasma with immobile ions has also been carried out by employing the method of Lagrangian transformation. The above mentioned results may be of relevance in fast-ignition scenarios. |
Wednesday, November 7, 2018 4:00PM - 4:12PM |
PO8.00011: Surface-Wave Excitation and Electron Acceleration at Ultra-High-Intensity Samuel Marini, Mickael Grech, Michèle Raynaud, Caterina Riconda The excitation of surface plasma waves (SPW) by an ultra-high intensity laser irradiating a micro-structured (e.g. grating-like) target offers new interesting opportunities for increasing the energy transfer from the laser to the plasma, as well as for high-energy electron beam production. In this work, we present two studies that rely on extensive Particle-In-Cell (PIC) simulations. The first investigates the effects of both the plasma density and laser intensity, in the relativistic regime of interaction, on the SPW excitation. The second investigates the effects of varying the laser pulse parameters (duration, chirp, etc.) on both the SPW excitation and electron acceleration in the SPW (along the target's surface). Our results can be used to optimize and control various possible applications of high-intensity laser-plasma produced SPW. |
Wednesday, November 7, 2018 4:12PM - 4:24PM |
PO8.00012: Electron beam driven generation and amplification of isolated relativistic sub-cycle pulses Illia Thiele, Evangelos Siminos, Tunde Fulop We propose a scheme for the generation of very intense sub-cycle pulses. Intense sub-cycle pulses find applications from reaction dynamics at the electronic level to the generation of isolated attosecond and zeptosecond X-ray pulses. However, methods like the parametric amplification are limited in terms of output energy to some tens of uJ due to material damage thresholds. To overcome these limitations we propose a method in which a pump electron beam is injected into an electromagnetic seed pulse as the latter is reflected by a mirror. The electron beam is shown to amplify the field of the seed pulse while upshifting its central frequency and reducing its number of cycles. We demonstrate the amplification by means of 1D and 2D particle-in-cell simulations. In order to explain and optimize the amplification process, a model based on fluid theory is proposed. We estimate that using currently available electron beams and terahertz pulse sources, our scheme is able to produce mJ-strong mid-infrared sub-cycle pulses. |
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