Bulletin of the American Physical Society
53rd Annual Meeting of the APS Division of Plasma Physics
Volume 56, Number 16
Monday–Friday, November 14–18, 2011; Salt Lake City, Utah
Session GO8: High Intensity Laser Plasma Interactions |
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Chair: Alec Thomas, University of Michigan Room: Ballroom I |
Tuesday, November 15, 2011 9:30AM - 9:42AM |
GO8.00001: Evidence of fountain effect through self-proton/ion radiography in relativistic laser target interaction N. Renard-Le Galloudec, Y. Paudel, A. Merwin, A. Ya Faenov, E. d'Humieres, Ph. Nicolai, V.L. Kantsyrev, I. Shresta, V.V. Shlyaptseva, G.C. Osborne, M.E. Weller, A.S. Safronova In the last 10 years laser-produced proton beams have emerged as a useful tool for applications from proton therapy to proton radiography of high-energy density phenomena. In our case, in addition to protons accelerated from the back different low and high Z target by the Target Normal Sheath Acceleration (TNSA) mechanism, protons and multi-charged ions with an energy of more than 7MeV/u are stripped from the front surface of the target, move away from it They are then turned around by self-generated fields in the front side expanding plasma, which then pull them back toward the target. They then go through the target and stalk and radiograph it, producing a self-radiography of the target with one laser beam. These two processes are recorded on the same RCF layers after the target. Observed proton/multicharged ions self-radiography phenomena could in future allow measurement the value of magnetic field produced in relativistic laser -- solid target interaction. [Preview Abstract] |
Tuesday, November 15, 2011 9:42AM - 9:54AM |
GO8.00002: Ultrafast Electron Beam Radiography of Self-Generated Magnetic Fields from High Intensity Laser-Solid Interactions W. Schumaker, C. McGuffey, A.G.R. Thomas, C. Zulick, V. Chvykov, F.J. Dollar, G. Kalintchenko, V. Yanovsky, A. Maksimchuk, K. Krushelnick, N. Nakanii, K.A. Tanaka Using $\sim 30$ $fs$ electron bunches generated with laser wakefield acceleration (LWFA) as a probe, the femtosecond temporal evolution of a $\sim 4 \times 10^{19}$ $W/cm^2$ short laser pulse with solid targets has been studied experimentally. Magnetic fields of $\sim 100$ $megagauss$ were observed travelling outward from the interaction point of the laser with a $10$ $\mu m$ aluminum foil at nearly the speed of light under ideal laser conditions. With degraded contrast, a pre-plasma forms on the front surface, containing the front surface magnetic field to the hole-boring region. This proof-of-principle experiment demonstrates the utility of LWFA electrons as a diagnostic technique for magnetic fields with femtosecond timescale and/or in sufficiently dense plasma. These results are supported by OSIRIS particle-in-cell simulations. [Preview Abstract] |
Tuesday, November 15, 2011 9:54AM - 10:06AM |
GO8.00003: Raman backscattering from subpicosecond laser pulses in a relativistic laser-plasma interaction Jun Ren, K. Flippo, S. Gaillard, D. Offermann, J. Cobble, E. Dodd, M. Schmitt, T. Kwan, M. Geissel, M. Schollmeier, T. Kluge, M. Bussmann, J. Rassuchine, T. Burris-Mog, K. Zeil, S. Kraft, J. Metzkes, T. Cowan, T. Lockard, C. Plechaty, Y. Sentoku, B. Gall, X. Yang, G. Miley In the course of a high-intensity short laser pulse interacting with a solid target mediated by laser-generated plasma, back scattered light from Raman backscattering (RBS) can substantially affect the evolution of the laser pulse in the plasma. Therefore, the RBS measurement is important in diagnosing processes occurring in the interaction. We will present time-integrated spectrum and power measurements of back scattered light centered at 1$\omega$, 2$\omega$ and 3$\omega$ from coupling high-contrast ultra intense lasers (at $\sim $ 10$^{20}$ W/cm$^{2})$ to a solid. The backscattered spectra show distributed peaks between 300nm -1750nm with broadened width. From analysis we determine plasma conditions including scale length, density profile and temperature. Collisional particle-in-cell simulations (LSP) reveal the effect of this inhomogeneous plasma on heating and acceleration of electrons through stochastic heating and ponderomotive acceleration, as well as the succeeding ion acceleration through the target normal sheath acceleration (TNSA) mechanism. [Preview Abstract] |
Tuesday, November 15, 2011 10:06AM - 10:18AM |
GO8.00004: Propagation of Laser-Driven Relativistic Electron Beam inside Solid Dielectric G.S. Sarkisov, D. Jobe, R. Spielman, V.V. Ivanov, P. Leblanc, Y. Sentoku, K. Yates, P. Wiewior, V.Yu. Bychenkov Laser probing diagnostics shadowgraphy, interferometry and polarimetry was used for comprehensive characterization of ionization wave dynamics inside glass target induced by laser-driven relativistic electron beam. Experiment was done using 50-TW Leopard laser at University of Nevada Reno. It has been shown that for laser flax $\sim $2$\times $10$^{18}$W/cm$^{2}$ hemispheric ionization wave propagates with c/3 speed has smooth electron density distribution, absorbing probing green beam in 2-10 times. Maximum of free-electron density inside glass target is $\sim $2x10$^{19}$cm$^{-3}$, which correspond to ionization $\sim $0.1{\%}. Magnetic and electric fields do not exceed $\sim $15 kG and $\sim $1 MV/cm. Electron temperature has hot-ring structure with maximum 0.1-0.5 eV. The topology of the interference phase shift shows the signature of the ``fountain effect'', a narrow electron beam that fans out from the propagation axis and heads back to the target surface. Two-dimensional PIC-simulations demonstrate radial spreading of fast electrons by self-consistent electrostatic fields. The very low ionization, $\sim $0.1{\%}, observed after the heating pulse suggests a fast recombination at the sub-ps time scale. Work was supported by the DOE/NNSA under UNR grant DE-FC52-06NA27616 and grant DE-PS02-08ER08-16. [Preview Abstract] |
Tuesday, November 15, 2011 10:18AM - 10:30AM |
GO8.00005: Bremsstrahlung Temperature Scaling in Ultra-Intense Laser-Plasma Interactions C. Zulick, B. Hou, J. Nees, A.G.R. Thomas, K. Krushelnick The absorption of laser energy during ultra-intense (I $\textgreater$ $10^{18}$ W/cm$^{2}$) laser-plasma interactions results in the production of a hot electron current, which can subsequently generate energetic protons, ions, and photons. The energetic photons are of particular interest in isomer excitation, positron production, and homeland security applications. Experiments were performed on the high repetition rate (500 Hz) Lambda Cubed laser (I $\approx$ $5 \cdot 10^{18}$, duration $30$ fs) allowing high resolution ($\lambda$/$\Delta\lambda$ = 300) spectroscopy of X-ray and $\gamma$-ray bremsstrahlung photons in the 20 keV to 3 MeV energy range. The effective bremsstrahlung temperature was measured over a range of laser energies, target materials, and detection angles. Additionally, simulations (MCNPX and GEANT4) were used to correlate experimental bremsstrahlung temperatures with hot electron temperatures, which were compared to existing electron temperature scaling laws. [Preview Abstract] |
Tuesday, November 15, 2011 10:30AM - 10:42AM |
GO8.00006: Hot Electron and Gamma-Ray Production using the Texas Petawatt Laser irradiating Thick Gold Targets Edison Liang, Gilliss Dyer, David Taylor, Taylor Clarke, Alexander Henderson, Xin Wang, Nathan Riley, Kristina Serratto, Petr Shagin, Todd Ditmire We report preliminary experimental results of using the Texas Petawatt laser (TPW) to create relativistic hot electrons and bremsstrahlung gamma-rays by irradiating thick gold targets. Using the f/3 focus in the TC1 target chamber, we focussed TPW to peak intensities of 10$^{19}$ to 10$^{20}$ W/cm$^2$. Results were obtained for gold targets of thicknesses ranging from 1mm to 4 mm. We measured the hot electron and bremsstrahlung gamma-ray spectra in both the front and back of the target. Hot electrons with energies exceeding several tens of MeV were detected. We also measured the gamma-ray angular distribution. This work was supported by DOE grant DE-SC-000-1481. [Preview Abstract] |
Tuesday, November 15, 2011 10:42AM - 10:54AM |
GO8.00007: Production of picosecond, kilojoule, petawatt laser pulses via Raman amplification of nanosecond pulses R. Trines, R. Bingham, P. Norreys, F. Fi\'uza, R.A. Fonseca, L.O. Silva, R.A. Cairns The demonstration of fast-ignition (FI) inertial confinement fusion (ICF) requires the delivery of 40 kJ - 100 kJ of laser energy to the hot spot within 16 ps. In addition, third harmonic conversion to 351 nm is needed to optimize $I\lambda^2$ to obtain the correct hot electron energy. High-energy picosecond petawatt beams at 351 nm are difficult to generate using conventional solid-state laser systems. Previous studies of Raman amplification concentrated on maximizing the intensity and power of femtosecond pulses [Trines et al., Nature Physics (2010)]. Here we present particle-in-cell simulations and analytic theory that confirm that Raman amplification of high-energy nanosecond pulses in plasma can generate petawatt peak power pulses of picosecond duration with high efficiency (up to 60\%), even at 351 nm wavelength. This scheme provides a potential new route for the realization of fast ignition ICF in the laboratory, as well as access to wide range of other high energy density physics research applications. This work was supported by STFC's CLF and CfFP, by EPSRC through grant EP/G04239X/1 and by FCT (Portugal) through grants PTDC/FIS/66823/2006 and SFRH/BD/38952/2007. [Preview Abstract] |
Tuesday, November 15, 2011 10:54AM - 11:06AM |
GO8.00008: Effects of radiation damping in ultra-intense laser matter interaction at extreme intensity regime Yasuhiko Sentoku, Rishi Pandit Effects of the radiation damping in the interaction of extremely intense laser ($> 10^{22}$W/cm$^2$) with metal targets are studied via a relativistic collisional particle- in-cell simulation, PICLS. We had introduced the Landau-Lifshitz equation, which is the first order term of the Lorentz-Dirac equation to PIC, and also derived the second order term to check its effect. We had implemented these damping terms in the two- dimensional PICLS code, and had studied the laser plasma interaction at $> 10^{22}$W/cm$^2$ intensities. Hot electrons generated by such extreme-intense laser lights on the target get the relativistic energy with relativistic Lorentz factor $\gamma > 100$, and lose energy strongly by emitting radiations. Especially, we had studied the second term's effect in a comparison with the first order damping term, and found that the second term becomes comparable to the first order term when the laser intensity $> 10^{23}$W/cm$^2$. With the higher order term, the hot electrons with energies greater than 500 MeV are totally suppressed and hard them to go beyond that energy even increasing the laser intensity $> 10^{23}$W/cm$^2$. [Preview Abstract] |
Tuesday, November 15, 2011 11:06AM - 11:18AM |
GO8.00009: Plasma as ultra-fast optical switch using relativistic transparency Sasikumar Palaniyappan, Rahul Shah, Hui Wu, Daniel Jung, Donald Gautier, Lin Yin, Brian Albright, Randall Johnson, Tsutomo Shimada, Samuel Letzring, Juan Fernandez, Bjorn Hegelich Laser-plasma interaction leading to relativistic transparency (RT) in 100 nm thick Diamond-Like-Carbon (DLC) nanofoil has been directly observed at an intensity of 2 10$^{20}$ W/cm$^{2}$ by measuring the shape and temporal phase of the pulse reflected from the plasma using a single shot Frequency-Resolved-Optical-Gating (FROG). The reflected light intensity drops sharply at the onset of RT with its temporal phase capturing the time dependant interaction dynamics. The corresponding spectrum is shifted to the red side extending up to $\sim $100 nm from the laser light pressure rapidly moving the critical surface away from the laser. Results from a 2D-VPIC simulation are very well consistent with measurements. [Preview Abstract] |
Tuesday, November 15, 2011 11:18AM - 11:30AM |
GO8.00010: Close Proximity Laser Beam Manipulation for HEDP Experiments with Plasma Mirrors* M. Geissel, M. Schollmeier, M. Kimmel, P. Rambo, J. Schwarz, B. Atherton, E. Brambrink, J. Fuchs, M. Nakatsutsumi Many high energy/high power lasers such as Z-Petawatt at Sandia National Laboratories utilize extremely heavy and sensitive optical assemblies for final focusing. Redirecting the beams is very difficult if not impossible, and setups also often require long focal lengths, which may compromise the pointing stability. We suggest that the application of plasma mirrors can be very useful for HEDP experiments with such systems, regardless of the contrast enhancing feature (e.g. using a high reflector as plasma mirror substrate). Applications of plasma mirrors can be deflection of the beam close to the target for more convenient experimental geometries or debris mitigation for the last large sized optics. In case of the more advanced concept of ellipsoidal geometries, plasma mirrors can even be used for f{\#} translation, leading to focus intensity enhancement and improved pointing stability (if f{\#} is reduced). This presentation will explain applications along with laser requirements and performance challenges. -- *Sandia National Labs is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corp., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Tuesday, November 15, 2011 11:30AM - 11:42AM |
GO8.00011: Measurement of the cluster mass fraction in a pulsed supersonic gas jet by frequency domain holography Xiaohui Gao, Xiaoming Wang, Rick Korzekwa, Mike Downer Accurate interpretation and control of laser-cluster experiments require complete characterization of the cluster gas jet, of which the cluster mass fraction is usually difficult to measure. Here we present an in situ optical measurement of the cluster mass fraction. We measured the fs-time-resolved phase shifts from the gas jet after ionization and heating by a pump pulse using frequency domain holography. The distinct dynamics of the intense-laser-ionized monomer and cluster allow us to separate the monomer and cluster contribution to the phase shifts in the time domain and thus to determine the cluster mass fraction. The temporal evolution of the cluster fraction and various other influences on the cluster fraction in a pulsed supersonic gas jet is being investigated. We found that the cluster fraction is typically less than 0.5 in our jet. We aim to increase the cluster fraction to 0.8, which is crucial for phase-matched harmonic generation at high laser intensity in cluster jet. [Preview Abstract] |
Tuesday, November 15, 2011 11:42AM - 11:54AM |
GO8.00012: Propagation of Relativistic Laser Pulses in Cluster Plasmas Brian Layer, Sung Jun Yoon, Jennifer Elle, Yu-Hsin Chen, Andrew Goers, George Hine, Howard Milchberg As atomic clusters explode and ionize under irradiation by an intense femtosecond laser pulse, a transient positive contribution to the index of refraction can result from the transition from a supercritical to subcritical plasma [1]. This effect has been used to self-focus intense laser pulses[2], but has not yet been examined in the relativistic intensity regime (I$_{0} \quad >$ 10$^{18}$ W*cm$^{-2})$. We observe the propagation of relativistically intense femtosecond laser pulses with a peak power of up to 25 TW in plasma formed in atomic gas cluster targets with an interaction length of up to 15 mm. We observe the dependence of this effect upon the laser pulselength and energy, as well as mean size and density of the atomic clusters. Ionization and propagation dynamics are examined with soft X-ray spectroscopy and electron density profiles extracted from transverse interferometry. \\[4pt] [1] T. Taguchi, T. M. Antonsen, and H. M. Milchberg, ``Resonant Heating of a Cluster Plasma by Intense Laser Light,'' Phys. Rev. Lett. 92(20), 205003 (2004).\\[0pt] [2] I. Alexeev, T. M. Antonsen, K. Y. Kim, and H. M. Milchberg, ``Self-Focusing of Intense Laser Pulses in a Clustered Gas,'' Phys. Rev. Lett. 90(10), 103402 (2003). [Preview Abstract] |
Tuesday, November 15, 2011 11:54AM - 12:06PM |
GO8.00013: Measurement of Ultrafast Plasma Currents in Two-Color Laser-Produced Plasma Yongsing You, Taek-Il Oh, Kiyong Kim We report the measurements of quasi-dc plasma currents produced in two-color laser-induced plasma. In the plasma current model proposed by Kim et al [1], the bound electrons of atoms or molecules undergo rapid tunneling ionization under an asymmetric laser field consisting of the fundamental and its second harmonic fields. The electrons liberated by the mixed laser fields form a directional transverse current on the timescale of sub-picosecond, simultaneously emitting radiation at THz frequencies. The principle of our photocurrent measurement is based on the Faraday rotation effect, in which the magnetic field induced by time-varying plasma current rotates the polarization of probe pulse propagating through the plasma. With polarization sensitive imaging and varying the pump-probe delay, we can map out the magnetic field profiles with high spatial and temporal resolution. We find that the magnetic field is confined within sub-100 microns in the transverse direction and lasts for sub-picosecond. The time derivatives of the plasma currents, calculated from our measured magnetic fields, are consistent with the measured THz waveforms. The correlation between them supports the plasma current model. \\[4pt] [1] K. Kim et al, Opt Express \textbf{15}, 4577 (2007). [Preview Abstract] |
Tuesday, November 15, 2011 12:06PM - 12:18PM |
GO8.00014: Properties of metals during the heating by intense laser irradiation using {\it ab initio} simulations Bastian Holst, Vanina Recoules, Marc Torrent, Stephane Mazevet Ultrashort laser pulses irradiating a target heat the electrons to very high temperatures. In contrast, the ionic lattice is unaffected on the time scale of the laser pulse since the heat capacity of electrons is much smaller than that of the lattice. This non-equilibrium system can be described as a composition of two subsystems: one consisting of hot electrons and the other of an ionic lattice at low temperature. We studied the effect of this intense electronic excitations on the optical properties of gold using {\it ab initio} simulations. We additionally use {\it ab initio} linear response to compute the phonon spectrum and the electron-phonon coupling constant within Density Functional Theory for several electronic temperatures of few eV. [Preview Abstract] |
Tuesday, November 15, 2011 12:18PM - 12:30PM |
GO8.00015: Status of the OMEGA EP Laser System D.D. Meyerhofer, S.-W. Bahk, J. Bromage, C. Dorrer, J.H. Kelly, B.E. Kruschwitz, S.J. Loucks, R.L. McCrory, S.F.B. Morse, J. Qiao, C. Stoeckl, L.J. Waxer, J.D. Zuegel The performance and experimental capabilities of the OMEGA EP Laser System continue to improve. The system, with four NIF-like beams, was completed in April 2008. All four beams can be operated at 351~nm into the OMEGA EP target chamber, with a total of 14 kJ in a 10-ns pulse and 6.3 kJ in a 2-ns pulse. Each UV beamline supports 100-ps operations with 100 J per beam. Two of the beams can be operated as high-energy-petawatt lasers (HEPW), with a maximum current energy of 1.5 kJ in a 1053-nm, 10-ps pulse. The HEPW beams can be directed into the OMEGA EP target chamber or into the 60-beam OMEGA target chamber for experiments that combine target compression with HEPW capability. The current and projected status of the laser system performance, laser and target diagnostics, and experimental capabilities will be presented. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
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