Bulletin of the American Physical Society
58th Annual Meeting of the APS Division of Plasma Physics
Volume 61, Number 18
Monday–Friday, October 31–November 4 2016; San Jose, California
Session CO6: Ultra-high Intensity Physics and Accelerators |
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Chair: Alec Thomas, University of Michigan/University of Lancaster Room: 230 C |
Monday, October 31, 2016 2:00PM - 2:12PM |
CO6.00001: Dense gamma-ray and pair creation using ultra-intense lasers Edison Liang, Willie Lo, Hannah Hasson, Gilliss Dyer, Taylor Clarke, Fabio Fasanelli, Kelly Yao, Ilija Marchenka, Alexander Henderson, Andriy Dashko, Yuling Zhang, Todd Ditmire We report recent results of gamma-ray and e$+$e- pair creation experiments using the Texas Petawatt laser (TPW) in Austin and the Trident laser at LANL irradiating solid high-Z targets. In addition to achieving record high densities of emerging gamma-rays and pairs at TPW, we measured in detail the spectra of hot electrons, positrons, and gamma-rays, and studied their spectral variation with laser and target parameters. A new type of gamma-ray spectrometer, called the scintillator attenuation spectrometer (SAS), was successfully demonstrated in Trident experiments in 2015. We will discuss the design and results of the SAS. Preliminary results of new experiments at TPW carried out in the summer of 2016 will also be presented. [Preview Abstract] |
Monday, October 31, 2016 2:12PM - 2:24PM |
CO6.00002: Gamma-ray emission enhanced by direct laser acceleration in a laser-driven magnetic field Alexey Arefiev, Tao Wang, Toma Toncian, David Stark Recently published particle-in-cell simulations [Phys. Rev. Lett. 116, 185003 (2016)] indicate that a high-intensity laser irradiating an over-critical plasma can induce relativistic transparency and drive a Megatesla magnetic field while propagating into the plasma. We have examined the role of such an azimuthal Megatesla-level magnetic field on electron dynamics in a laser pulse with intensities around $5 \times 10^{22}$ W/cm$^2$, within reach for the existing laser facilities. We find that the magnetic field can be utilized in two complementary ways: to enhance direct laser acceleration, generating a GeV-level electron beam in the plasma, and to boost synchrotron emission by the accelerated electrons, producing copious multi-MeV photons in the form of a collimated beam. This regime potentially opens an opportunity for generating dense gamma-ray beams using existing laser facilities, thus fast-tracking a number of eagerly awaited applications. [Preview Abstract] |
Monday, October 31, 2016 2:24PM - 2:36PM |
CO6.00003: Brilliant XUV radiation from laser-illuminated near-critical plasmas T G Blackburn, A A Gonoskov, M Marklund Bursts of XUV radiation are generated by nanoscale oscillations of surface electrons in plasmas illuminated by intense, linearly-polarised laser light. For plasmas with near-critical electron density, these bursts are characterised by high conversion efficiency into harmonics of order 100 and brilliance comparable to that of a third-generation synchrotron light source. We present particle-in-cell simulations of the source that explore experimentally relevant parameters, and demonstrate that it could be realised in today's high-intensity laser facilities. [Preview Abstract] |
Monday, October 31, 2016 2:36PM - 2:48PM |
CO6.00004: Gamma-ray emission in ultra-intense laser interaction with solid targets Ondrej Klimo, Jiri Vyskocil, Deepak Kumar, Jiri Limpouch, Stefan Weber Electrons moving in ultra-intense laser fields emit hard radiation due to radiation reaction and non-linear Compton scattering. Multi-MeV $\gamma$-rays were measured by scattering of electrons generated from laser wakefield with a focused laser of intensity $a_0 \sim 1$. However, non-linear Compton scattering and radiation reaction is also an efficient mechanism for generating copious amount of $\gamma$-rays in laser interaction with solids at intensities approaching $\sim 10^{22}$ W/cm$^{2}$. Emission of $\gamma$-rays due to radiation reaction and bremsstrahlung are investigated here in the high intensity regime of laser-solid target interaction by using a combination of Particle-in-Cell and Monte Carlo radiation transport simulations. The relative contribution of these processes is analyzed as a function of the target parameters. We concentrate on the influence of the target thickness, material, preplasma conditions or a surface structure on the generation of high energy photons and study separately their energy and angular distributions. It is demonstrated that the presence of preplasma or a special surface structure may significantly enhance emission of hard $\gamma$ photons and their cut-off energy and change their angular distribution. [Preview Abstract] |
Monday, October 31, 2016 2:48PM - 3:00PM |
CO6.00005: Radiation damping induced electron trapping and positron creation Yanjun Gu, Ondrej Klimo, Stefan Weber, Georg Korn High power laser facilities with intensities up to $\mathrm{10^{22}~W/cm^2}$ have been realized and the forthcoming installations are expected to reach $\mathrm{10^{22-24}~W/cm^2}$ or even higher. At these intensities, the radiation effects and quantum electrodynamics description come into play. The emitted photon momentum becomes comparable to the momentum of the emitting electrons. In this work, we propose a regime of electron self-injection and trapping in the ultra-high intensity laser-plasma interaction. The electrons accumulated at the head of the laser pulse are injected into the pulse centre due to the strong longitudinal electrostatic field created by the high density shell. These electrons, which experience a restoring force provided by the emitted photons, can be confined in the laser pulse for a long time. The corresponding photons are produced in the region where the laser field is strong. High energy and well collimated positron bunches are produced. This regime may be beneficial for the potential experiments to be carried out on large laser facilities such as ELI. [Preview Abstract] |
Monday, October 31, 2016 3:00PM - 3:12PM |
CO6.00006: Electromagnetic cascades and the depletion of intense fields. Stepan Bulanov, Daniel Seipt, Thomas Heinzl, Mattias Marklund, Qing Ji, Sven Steinke, Carl Schroeder, Eric Esarey, Wim P. Leemans The interaction of electrons, positrons, and photons with intense electromagnetic fields gives rise to multi-photon Compton and Breit-Wheeler processes.~It is shown that electrons and/or positrons undergo a cascade-type process involving multiple~emissions of photons. These photons can consequently convert into electron-positron pairs. As a result charged~particles quickly lose their energy developing an exponentially decaying energy distribution. Moreover the multi-photon nature of~Compton and Breit-Wheeler processes implies the absorption of a significant number of photons. As a result, the interaction of a highly charged electron bunch with an intense laser pulse can lead to a significant depletion of the laser pulse energy, thus rendering the external field approximation invalid. The relevance of these results to the proposed BELLA-i beamline at BELLA center at LBNL is discussed. [Preview Abstract] |
Monday, October 31, 2016 3:12PM - 3:24PM |
CO6.00007: Ion acceleration through radiation pressure in quanto-electrodynamical regimes Dario Del Sorbo, Chris Ridgers The strong radiation pressure carried by high-intensity lasers interacting with plasmas can accelerate ions over very short distances. The resulting compact particle accelerator could find applications in medical physics (radiotherapy) as well as in fundamental physics (hadron interactions). With next-generation multi-petawatt lasers, reaching focused intensity $\sim 10^{23}\;\mbox{Wcm}^{-2}$, ions could potentially reach GeV energies. However, the physics of laser-matter interactions at these extreme intensities is not well understood. In particular, on acceleration by the electromagnetic fields of the laser, the electrons in the plasma start to radiate hard photons prolifically. These hard photons can decay to electron-positron pairs, a cascade of pair production can ensue leading to the formation of an over-dense pair plasma which can absorb the laser-pulse. We have developed a self-consistent theory for both hole boring and light sail radiation pressure ion-acceleration, accounting for radiation-reaction and pair-creation. We show that the key role is played by a pair plasma that arises between the laser and the accelerated ions, strongly modifying the laser absorption. [Preview Abstract] |
Monday, October 31, 2016 3:24PM - 3:36PM |
CO6.00008: Pair plasma formation in the interaction of a thin plasma with ultra-intense counter-propagating lasers Cody Slade-lowther Next-generation lasers (e.g. ELI) expect to reach peak intensities of $\sim 10^{23}$ Wcm$^{-2}$. At such intensities, the electromagnetic field strength is sufficient for non-linear Quantum Electrodynamics effects to become important. The processes of non-linear Compton scattering and Breit-Wheeler Pair production become likely at intensities $\geq 10^{23}$ Wcm$^{-2}$, and have been predicted to lead to prolific pair and $\gamma$-ray production via electromagnetic cascades. We present results for the case of two counter-propagating circularly- polarized lasers of intensity $I\in [10^{23},10^{25}]$ Wcm$^{24}$ interacting with a plasma of initial density $n_0\in [10^{25},10^{35}]$ via the Monte-Carlo- particle-in-cell code EPOCH. We show the maximum pair plasma density in $I$ vs $n_0$ space. We further discuss the variation within this space on the plasma characteristics, including laser absorption and field-particle energy distribution. [Preview Abstract] |
Monday, October 31, 2016 3:36PM - 3:48PM |
CO6.00009: QED-driven laser absorption Matthew Levy, T Blackburn, N Ratan, J Sadler, C Ridgers, M Kasim, L Ceurvorst, J Holloway, M Baring, A Bell, S Glenzer, G Gregori, A Ilderton, M Marklund, M Tabak, S Wilks, P Norreys Absorption covers the physical processes which convert intense photon flux into energetic particles when a high-power laser (I \textgreater 10$^{\mathrm{18}}$ W cm$^{\mathrm{-2}}$ where I is intensity at 1$\mu $m wavelength) illuminates optically-thick matter.~It underpins important applications of petawatt laser systems today, e.g., in isochoric heating of materials. Next-generation lasers such as ELI are anticipated to produce quantum electrodynamical (QED) bursts of $\gamma $-rays and anti-matter via the multiphoton Breit-Wheeler process which could enable scaled laboratory probes, e.g., of black hole winds. Here, applying strong-field QED to advances in plasma kinematic theory, we present a model elucidating absorption limited only by an avalanche of self-created electron-positron pairs at ultra-high-field. The model, confirmed by multidimensional QED-PIC simulations, works over six orders of magnitude in optical intensity and reveals this cascade is initiated at 1.8 x 10$^{\mathrm{25}}$ W cm$^{\mathrm{-2}}$ using a realistic linearly-polarized laser pulse. Here the laser couples its energy into highly-collimated electrons, ions, $\gamma $-rays, and positrons at 12{\%}, 6{\%}, 58{\%} and 13{\%} efficiency, respectively. We remark on attributes of the QED plasma state and possible applications. [Preview Abstract] |
Monday, October 31, 2016 3:48PM - 4:00PM |
CO6.00010: Controlled high-energy ion acceleration with intense chirped standing waves Felix Mackenroth, Arkady Gonoskov, Mattias Marklund We present the latest results of the recently proposed ion acceleration mechanism "chirped standing wave acceleration". This mechanism is based on locking the electrons of a thin plasma layer to the moving nodes of a standing wave formed by a chirped laser pulse reflected from a mirror behind the thin layer. The resulting longitudinal charge separation field between the displaced electrons and the residual ions then accelerates the latter. Since the plasma layer is stabilized by the standing wave, the formation of plasma instabilities is suppressed. Furthermore, the experimentally accessible laser chirp provides a versatile tool for manipulating the resulting ion beam in terms of maximum particle energy, particle number and spectral distribution. Through this scheme, proton beams, with energy spectra peaked around 100 MeV, were shown to be feasible for pulse energies at the level of 10 J. [Preview Abstract] |
Monday, October 31, 2016 4:00PM - 4:12PM |
CO6.00011: ABSTRACT WITHDRAWN |
Monday, October 31, 2016 4:12PM - 4:24PM |
CO6.00012: Design Study on a G-Band Folded Waveguide Traveling Wave Tube Amplifier Using 3D CFDTD PIC Method for Future Advanced Imaging Applications M. C. Lin, Heather Song, Jinwoo Shin, Joonho So Design study on a G-band (220 GHz) folded waveguide traveling wave tube (FWTWT) is presented. Due to ease of fabrication, wide bandwidth, and versatility in operation, a FWTWT structure was chosen for future advanced broadband amplifier for imaging applications. The cold test simulations were carried out employing finite element method (FEM) to determine dispersion relation, circuit dimensions, and operating beam parameters of the device. Beam optics study was performed to eliminate interception to the circuit wall and minimize beam scalloping. While precise control of beam location and size is very important to device performance, hot test simulations based on a 3D conformal finite-difference time-domain (CFDTD) particle-in-cell (PIC) method have been extensively used to predict performance of the beam transport and stability characteristics in order to optimize the electrical operating parameters. The 3D CFDTD PIC simulations of the full model have demonstrated a greater than 26 dB large signal gain at 220 GHz and beam voltage of approximately 18 kV. The effects of beam filling ratio, magnetic field, and beam interception on the gain have been studied in considerable detail and will be presented. [Preview Abstract] |
Monday, October 31, 2016 4:24PM - 4:36PM |
CO6.00013: Electric and Magnetic Field Measurements in High Energy Electron Beam Diode Plasmas using Optical Spectroscopy$^{\mathrm{1}}$ Mark Johnston, Sonal Patel, Mark Kiefer, S. Biswas, R. Doron, E. Stambulchik, V. Bernshtam, Yitzhak Maron The RITS accelerator (5-11MV, 100-200kA) at Sandia National Laboratories is being used to evaluate the Self-Magnetic Pinch (SMP) diode as a potential flash x-ray radiography source. This diode consists of a small, hollowed metal cathode and a planar, high atomic mass anode, with a small vacuum gap of approximately one centimeter. The electron beam is focused, due to its self-field, to a few millimeters at the target, generating bremsstrahlung x-rays. During this process, plasmas form on the electrode surfaces and propagate into the vacuum gap, with a velocity of a 1-10 cm's/microseconds. These plasmas are measured spectroscopically using a Czerny-Turner spectrometer with a gated, ICCD detector, and input optical fiber array. Local magnetic and electric fields of several Tesla and several MV/cm were measured through Zeeman splitting and Stark shifting of spectral lines. Specific transitions susceptible to quantum magnetic and electric field effects were utilized through the application of dopants. Data was analyzed using detailed, time-dependent, collisional-radiative (CR) and radiation transport modeling. Recent results will be presented. $^{\mathrm{1}}$Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Monday, October 31, 2016 4:36PM - 4:48PM |
CO6.00014: Experimental Verification on Remote Detectability of Concealed Radioactive Material Based on the Plasma Discharge Delay Time using High-Power Millimeter-Wave Dongsung Kim, Dongho Yu, Ashwini Sawant, Mun Seok Choe, Ingeun Lee, EunMi Choi We experimentally demonstrate a remote detection method of a radioactive source by plasma breakdown using high-power millimeter-wave source, gyrotron. A number of free electrons near the radioactive source are much higher than those of without the radioactive source (roughly 10 particles/cm$^{\mathrm{3}})$ owing to the interaction of air molecules and strong gamma rays generated by radioactive material. The RF wave beam is focused in ambient air, and the plasmas discharge occurs involving random delay time which means a time interval between the RF wave and a fluorescent light caused by the plasma. We observed that the delay time decreased significantly due to the high density of free electrons in Ar plasma with an existence of Co60 radioactive material. This technique of delay time measurement shows 1000 times more sensitive than a method of detectable mass equation to identify the existence of radioactive source remotely. It is the first experimental verification of radioactive material detection using a high power gyrotron. This study shows that a remote detection of radioactive material based on analysis of precise delay time measurement could be feasible by using a high power millimeter/THz wave gyrotron. [Preview Abstract] |
Monday, October 31, 2016 4:48PM - 5:00PM |
CO6.00015: Generation of attosecond pulse in interaction of chirped femtosecond laser pulse with nitrous oxide molecule Sakineh Kosar Sadighi, Mohammad Monfared, Elnaz Irani, Rasoul Sadighi Bonabi High harmonic generation in interaction of femtosecond chirped laser pulse with nitrous oxide molecule is investigated. The effects of positive and negative chirp are studied in this plasmas. Three dimensional calculation of molecular dynamics is formulated using time-dependent density functional approach. Extending of cut-off frequency for positive chip and increasing of attosecond pulse intensity for negative chirp is the remarkable results of this work. [Preview Abstract] |
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