Bulletin of the American Physical Society
38th Annual Meeting of the Division of Atomic, Molecular, and Optical Physics
Volume 52, Number 7
Tuesday–Saturday, June 5–9, 2007; Calgary, Alberta, Canada
Session Q2: Focus Session: The Ultra Intense Laser Frontier |
Hide Abstracts |
Chair: L. DiMauro, Ohio State University Room: TELUS Convention Centre Macleod C |
Friday, June 8, 2007 1:30PM - 2:06PM |
Q2.00001: High Energy Density Physics with the Texas Petawatt Laser and a Look Toward Exawatt Lasers Invited Speaker: Using a combination of high peak power chirped pulse amplification technologies we are developing a unique petawatt peak power laser at the University of Texas. One of the new frontiers opened by a lasers like the Texas Petawatt is in high energy-density (HED) science. The Texas Petawatt will deliver 100 fs pulses with energy of over 200 J. In this talk I will discuss some of the recent experiments in high energy density science we have conducted using existing high intensity short pulse lasers with illustrative examples that point to applications on the Texas Petawatt. These areas of HED investigation include exotic physics such Gbar pressures in heated solids, radiative hydrodynamics and nuclear fusion. I will, for example, discuss experiments on isochoric heating of solid targets for high temperature and pressure equation of state measurements. I will examine some of the ways that plasma and hydrodynamic regimes of astrophysical significance can be accessed with petawatt-class lasers. I will also discuss applications in the generation of ultrafast, bright bursts of radiation including hard x-rays, protons and fast neutrons. Finally, I will discuss how the technology being implemented in the Texas Petawatt could be scaled to the exawatt peak power level in a straightforward way. [Preview Abstract] |
Friday, June 8, 2007 2:06PM - 2:18PM |
Q2.00002: Classical Ensemble Studies of Double Ionization at 390 nm S.L. Haan, Z.S. Smith An ensemble of 400,000 classical 3d atoms is employed to investigate double ionization of helium for laser wavelength 390 nm and intensity 1.1PW/cm$^2$. It has previously been shown by Parker {\it et al.} [1] that electrons of energy above 2U$_p$ are produced under these conditions. Such electrons are also produced in the classical model. Trajectories which lead to energy above 2U$_p$ are analyzed and shown to have a median time delay of 0.56 cycle between recollision and final ionization, with over 99\% having time delay of at least 0.16 cycle. Two characteristic recollision sequences are presented in detail, one of which can be described as excitation-backscatter-escape and the other as recapture ionization with prompt nuclear scattering. It is shown how the nuclear and laser forces combine in each case to give an electron--usually the struck electron--final energy above the usual 2U$_p$ cap. [1] J. S. Parker, {\it et al.}, Phys. Rev. Lett. {\bf96}, 133001 (2006). [Preview Abstract] |
Friday, June 8, 2007 2:18PM - 2:30PM |
Q2.00003: Intense field ionization of methane, butane, and octane: transition from molecular to atomic response Sasikumar Palaniyappan, Robert Mitchell, Robert Sauer, Barry Walker We report the ion yield measurements of C$^{+n}$ atomic ionic fragments up to n$<$6 from strong/ultra strong laser field ionization of methane, butane, and octane at intensities from 10$^{13}$ W/cm$^{2}$ to 10$^{19}$ W/cm$^{2 }$and try to identify the transition from a molecular response to an atomic response in terms of laser intensity when a molecule interacts with an intense laser. Measured carbon ion yields from C$^{+2}$ to C$^{+4}$ from CH$_{4}$, C$_{4}$H$_{10}$, and C$_{8}$H$_{18}$ are almost identical. For C$^{+2}$, C$^{+3}$ and C$^{+4}$ from all these molecules, ADK results agree with the measured yields near saturation and below saturation the measured yields are higher than the ADK results. The C$^{+4}$ ion curves for all these molecules exhibit a knee structure associated with a non sequential ionization or multiple molecular ionization mechanisms. In addition to the knee structure, ion yields of C$^{+4}$ from all these molecules exceed the ion yields of C$^{+2}$ and C$^{+3}$ at $\sim $10$^{14}$ W/cm$^{2}$. The C$^{+4}$ ion yields from methane measured with both circularly and linearly polarized fields are almost identical, which rules out the recollision mechanism being the significant contribution to the knee structure. We will also present results on C$^{+5}$ ion yields and compare these at 10$^{19 }$W/cm$^{2}$ to the atomic response. [Preview Abstract] |
Friday, June 8, 2007 2:30PM - 2:42PM |
Q2.00004: Quantum Interference Effects In Radiation From Atomic Ionization In Ultrahigh Fields Isaac Ghebregziabher, B.C. Walker We quantify electron wavefunction interference effects on radiation by calculating the angle- and energy-resolved Larmor radiation from atomic ionization in the focus of ultra-intense field. Our calculations use a semi-classical, trajectory ensemble model of ionization for intensities in the range of 10$^{16}$ to 10$^{20}$ W/cm$^{2}$. For non-relativistic intensities, wave function interference leads to a negligible effect on radiation which decreased by less than 50{\%} from that of a classical electron calculation. For relativistic intensities, including the quantum nature of ionization decreases the radiation by an order of magnitude due to destructive interference effects in the extended probability of the electron wavefunction and the quantum nature of ionization. The interference effect is largest for high energy photons since ionization extends to a spatial width of $\sim $300nm and electron quiver width is $\sim $1$\mu $m. Our results also show the decrease in radiation due to the quantum nature of an electron is larger when emitted photons are observed in the laser polarization direction than in the propagation direction. [Preview Abstract] |
Friday, June 8, 2007 2:42PM - 3:18PM |
Q2.00005: First light from the Diocles laser: Relativistic laser-plasmas and beams Invited Speaker: Reported are first experimental results from a new high-power (150 TW) laser, Diocles, now in operation at the University of Nebraska, Lincoln. Discussed are novel approaches to using the ultra-high-intensity light from this laser to study relativistic laser plasma interactions. Bright, ultrashort duration (femtosecond ) pulses of energetic (keV -- MeV) x-ray and charged-particle beams are generated through these interactions. Also covered in this talk will be applications of these unique radiation sources for research in the physical sciences, as well as biomedicine, defense and homeland security. [Preview Abstract] |
Friday, June 8, 2007 3:18PM - 3:30PM |
Q2.00006: Measurements of ultraintense ultrafast laser pulse electron acceleration through analysis of radioactive products D.R. Schultz, C.R. Vane, J.R. Beene, S. Reed, A. Maksimchuk, V. Yanovsky, V. Chvykov, G. Kalintchenko, S. Banerjee, D. Umstadter Rapid progress has recently been achieved in development of techniques to controllably accelerate charged particles to relativistic energies using plasma wake fields generated in gas or dense media using ultraintense ultrafast laser pulses. An inherent technical difficulty in these experiments lies in complications of measuring the energy and angular distributions of large numbers ($>$ 10$^{9})$ of `simultaneously' ($\sim $ ps) accelerated particles. We will discuss experimental techniques developed for interrogation of laser accelerated electrons, including methods based on production of radioactive targets. [Preview Abstract] |
Friday, June 8, 2007 3:30PM - 3:42PM |
Q2.00007: Photoelectron Angular Distributions from an Ultrastrong Field Atom Interaction Anthony DiChiara, Isaac Ghebregziabher, Robert Sauer, Barry Walker Ultrastrong field laser physics has introduced a new regime for light-matter interactions. Photoelectrons in the continuum acquire relativistic kinetic energy from the laser electric field and the laser magnetic field can no longer be ignored. Therefore, the full Lorentz force is necessary to understand photoelectron continuum dynamics. As a result photoelectrons are pushed toward the direction of laser propagation. This effect impacts processes such as rescattering and high harmonic generation by preventing photoelectrons from revisiting the atomic core. In addition, the large photoelectron velocity could prove useful for laser based accelerator schemes. We report the photoelectron angular distributions measured for Argon atoms at an intensity of 5x10$^{18}$ W/cm$^{2}$. The experimental apparatus consists of a 780 nm, 45 fs Ti:Sapphire chirped pulse amplifier operating at the terawatt level. The laser is focused in a UHV chamber to a spot of 2 $\mu $m in diameter. We find that the isotropy increases with intensity and lower kinetic energy photoelectrons are more isotropic. [Preview Abstract] |
Friday, June 8, 2007 3:42PM - 3:54PM |
Q2.00008: Elongation of plasma channel for electron acceleration Liming Chen Experiments for the laser guiding studies has been carried out with the 30 fs, 100 TW Ti:Sapphier laser pulse interaction with the long slab (\textit{1.2x10 mm}$^{2})$ and discharged capillary of underdense plasma. Formation of extremely long plasma channel with its length (\textit{$\sim $ 10 mm}) 10 times above the Rayleigh length is observed when the laser pulse power is much higher than the critical power for relativistic self-focusing. The long self-guiding channel formation is accompanied by the quasi-monoenergetic electron acceleration with a low transverse emittance (\textit{$<$ 0.8 $\pi $ mm mrad}) and high electric current (up to \textit{$\sim $ 10 nC/shot}). In order to continuously elongate plasma channel, a 4 cm-scale discharged capillary was used. We successfully demonstrated laser-plasma acceleration of high-quality electron beams up to nearly GeV. Our results exactly verified the prediction of laser-wakefield acceleration through a cm-scale plasma channel in the ``blowout bubble'' regime, where a micro-scale plasma cavity produced through the ultra-relativistic laser-plasma interactions plays an essential role in the self-injection and acceleration of electrons. [Preview Abstract] |
Friday, June 8, 2007 3:54PM - 4:06PM |
Q2.00009: High harmonics and sub-attosecond pulses in the relativistic regime Teodora Baeva, Sergey Gordienko, Alexander Pukhov The theory of relativistic spikes explaining the high harmonics generation due to the interaction of a short ultra-relativistic laser pulse with overdense plasma in the relativistic regime is presented. The main analytical results based on microscopic analysis of the plasma as well as PIC simulations are discussed. This theory predicts universal spectrum of the high harmonics, which includes the power-law part $I_n\propto n^{-8/3}$ for $n<\sqrt{8\alpha}\gamma^3_{max}$, followed by exponential decay. Here $\gamma_{max}$ is the largest relativistic $\gamma$-factor of the plasma surface and $\alpha$ is the second derivative of the surface velocity at this moment. The high harmonic roll-over at $\gamma_{max}^3$ is parametrically larger than the $4\gamma_{max}^2$ predicted by the oscillating mirror model based on the Doppler effect. These predictions of relativistic spikes were confirmed experimentally. The cornerstone of the theory is the new physical phenomenon: spikes in the relativistic $\gamma$-factor of the plasma surface. These spikes define the high order harmonic spectrum and lead to a train of sub-attosecond pulses in the reflected radiation. The theory of relativistic spikes proposes a way to extract a single attosecond pulse out of the pulse train generated by a multi-cycle driver by means of the mechanism of Relativistic Plasma Control (RPC). [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700