Bulletin of the American Physical Society
43rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 57, Number 5
Monday–Friday, June 4–8, 2012; Orange County, California
Session B4: Invited Session: Frontiers of Intense Laser Physics |
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Chair: Anthony Starace, University of Nebraska Room: Garden 1-2 |
Tuesday, June 5, 2012 10:30AM - 11:00AM |
B4.00001: Gigavolt-Energy Electrons and Femtosecond-Duration Hard X-Rays Driven by Extreme Light Invited Speaker: Donald Umstadter The interactions of high-peak power laser light focused to extremely high intensity, or ``extreme light,'' is at the core of high-energy laser-driven electron accelerators, and novel laser-synchrotron x-ray light sources. The hallmark of extreme light is its ability to cause the instantaneous electron quiver motion to become relativistic. We discuss recent progress in understanding the physics of extreme light, and the advanced electron and x-ray technologies that it drives. Through the mechanism of relativistic self-guiding, focused light from our 100-TW Diocles laser was propagated in plasma at relativistic intensity for distance of 1 cm [corresponding to over 15 vacuum diffraction (Rayleigh) ranges]. As a result of this extended propagation length, electrons were accelerated by a laser-wakefield to near GeV energy in a well-collimated beam. The electron beam was measured to be tunable over a wide energy range, 100 -- 800 MeV, with 5-- 25{\%} energy spread, and 1-- 4-mrad divergence angle. The experimental results were found to be in reasonable agreement with the results of numerical simulation, which predict even higher electron energy (multi-GeV) with our recently upgraded peak laser power ($>$0.5 PW). These characteristics, along with their lack of any measurable amount of dark-current, make these electron beams good candidates for driving synchrotron x-ray sources. The development of one such x-ray source will also be discussed, one driven by inverse Compton scattering of laser light by laser-accelerated electrons. Its small radiation source size ($\sim $ 10 microns) and low angular beam divergence ($<$ 10 mrad) make it quite promising for applications in radiology. By virtue of its ultra-short pulse duration ($<$ 10 fs) and wide energy tunability (10 keV -- 10 MeV), it can also be used to probe matter with atomic-scale spatial and temporal resolution---simultaneously. [Preview Abstract] |
Tuesday, June 5, 2012 11:00AM - 11:30AM |
B4.00002: Combined Ion and Laser Field Effects in Intense Laser Ionization of Atoms and Molecules Invited Speaker: Robert Jones The simpleman's approximation and it's extension to the 3-step model have been extremely successful in guiding our understanding of strong field processes in atoms and molecules and the development of applications from molecular imaging through electron rescattering and HHG, to the attosecond streak camera. Even so, the principal approximations, adiabatic tunneling ionization followed by laser driven electron dynamics in a flat ionization continuum are not always applicable. We have been investigating two such problems. The first is near threshold ionization in the presence of a low frequency field. In this case, the field of the parent ion can dramatically influence the momentum and energy transfer to the continuum electron. The second is multi-electron dissociative ionization (MEDI) of small molecules (e.g. N$_{2}$, O$_{2}$, CO, NO) in asymmetric fields. It has long been recognized that non-adiabatic electron localization during the dissociation of a molecule in the presence of an intense laser can lead to the production of higher charge states. The use of asymmetric laser fields allows us to test the directionality of the dissociation predicted by the enhanced ionization model and the time-scales over which electron localization may occur. [Preview Abstract] |
Tuesday, June 5, 2012 11:30AM - 12:00PM |
B4.00003: Optics in the Relativistic Regime Invited Speaker: Toshiki Tajima Optics has extended the frontier of low energy physics. Here we present the progress in the opposite direction of relativistic intensity regime of optics. With intense and large energy laser, particles may be accelerated to high energies via laser wakefield acceleration (Tajima and Dawson, 1979) over a compact distance orders of magnitude shorter than the RF approach. We should be able to accelerate electrons (over 30m) and ions (over cm) toward TeV with an existing kJ laser. We can check Lorentz invariance in the ultrarelativistic regime. Further, laser allows us to explore the presence of weakly coupling fields such as Dark Matter and Dark Energy with an unprecedented sensitivity. We call this emerging capability as the Laser Particle Physics Paradigm (LP$^{3})$. [Preview Abstract] |
Tuesday, June 5, 2012 12:00PM - 12:30PM |
B4.00004: Probing Ultrafast Processes in Intense Laser--Matter Interactions Invited Speaker: S.X. Hu This talk reports on computational studies of using sub-femtosecond/attosecond extreme ultraviolet and soft-x-ray pulses to probe ultrafast processes in intense laser interactions with atoms, molecules, and plasmas. By developing and optimizing the finite-element discrete-variable-representation (FEDVR) combined with the real-space product (RSP) algorithm, a powerful computational method is generated, enabling one to explore transient processes in quantum, few-body systems non-perturbatively driven by strong electromagnetic fields. These studies include attosecond photoelectron microscopy of molecular structures, ultrafast probing ion--atom collisions, as well as exploring electron correlations in single-/double-ionization of helium in intense laser fields. Detailed discussions on what has been learned and what can be done in experiments will be presented. This work was partially supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302, the University of Rochester, and the New York State Energy Research and Development Authority. The support of DOE does not constitute an endorsement by DOE of the views expressed in this article. Computations have been conducted utilizing the Kraken Supercomputer of the National Institute of Computational Sciences (NICS) at Oak Ridge National Laboratory. [Preview Abstract] |
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