The 1990 National Academy of Science final report of its review of the Inertial Confinement Fusion Program recommended completion of a series of target physics objectives on the 10-beam Nova laser at the Lawrence Livermore National Laboratory as the highest-priority prerequisite for proceeding with construction of an ignition-scale laser facility, now called the National Ignition Facility (NIF). These objectives were chosen to demonstrate that there was sufficient understanding of the physics of ignition targets that the laser requirements for laboratory ignition could be accurately specified. This research on Nova, as well as additional research on the Omega laser at the University of Rochester, is the subject of this review. The objectives of the U.S. indirect-drive target physics program have been to experimentally demonstrate and predictively model hohlraum characteristics, as well as capsule performance in targets that have been scaled in key physics variables from NIF targets. To address the hohlrau...

The physics basis for ignition using indirect-drive targets on the National Ignition Facility

Astrophysical magnetic fields and nonlinear dynamo theory

The advent of ultraintense laser pulses generated by the technique of chirped pulse amplification (CPA) along with the development of high-fluence laser materials has opened up an entirely new field of optics. The electromagnetic field intensities produced by these techniques, in excess of ${10}^{18}\phantom{\rule{0.3em}{0ex}}\mathrm{W}∕{\mathrm{cm}}^{2}$, lead to relativistic electron motion in the laser field. The CPA method is reviewed and the future growth of laser technique is discussed, including the prospect of generating the ultimate power of a zettawatt. A number of consequences of relativistic-strength optical fields are surveyed. In contrast to the nonrelativistic regime, these laser fields are capable of moving matter more effectively, including motion in the direction of laser propagation. One of the consequences of this is wakefield generation, a relativistic version of optical rectification, in which longitudinal field effects could be as large as the transverse ones. In addition to this, other effects may occur, including relativistic focusing, relativistic transparency, nonlinear modulation and multiple harmonic generation, and strong coupling to matter and other fields (such as high-frequency radiation). A proper utilization of these phenomena and effects leads to the new technology of relativistic engineering, in which light-matter interactions in the relativistic regime drives the development of laser-driven accelerator science. A number of significant applications are reviewed, including the fast ignition of an inertially confined fusion target by short-pulsed laser energy and potential sources of energetic particles (electrons, protons, other ions, positrons, pions, etc.). The coupling of an intense laser field to matter also has implications for the study of the highest energies in astrophysics, such as ultrahigh-energy cosmic rays, with energies in excess of ${10}^{20}\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. The laser fields can be so intense as to make the accelerating field large enough for general relativistic effects (via the equivalence principle) to be examined in the laboratory. It will also enable one to access the nonlinear regime of quantum electrodynamics, where the effects of radiative damping are no longer negligible. Furthermore, when the fields are close to the Schwinger value, the vacuum can behave like a nonlinear medium in much the same way as ordinary dielectric matter expanded to laser radiation in the early days of laser research.

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Optics in the relativistic regime

http://absimage.aps.org/image/DAMOP12/MWS_DAMOP12-2012-000066.pdf

Optics in the Relativistic Regime

An overview is given of the physics issues relevant to the plasma wakefield accelerator, the plasma beat-wave accelerator, the laser wakefield accelerator, including the self-modulated regime, and wakefield accelerators driven by multiple electron or laser pulses. Basic properties of linear and nonlinear plasma waves are discussed, as well as the trapping and acceleration of electrons in the plasma wave. Formulas are presented for the accelerating field and the energy gain in the various accelerator configurations. The propagation of the drive electron or laser beams is discussed, including limitations imposed by key instabilities and methods for optically guiding laser pulses. Recent experimental results are summarized.

Overview of plasma-based accelerator concepts

The Korteweg‐de Vries equation is modified to include energy dissipation. In the cases treated the dissipative term is the Fourier transform of the linear damping. The effect of a small amount of such dissipation on the time evolution of a solitary wave is obtained.

Damping of Solitary Waves

The following macroscopic equation is shown to govern the time development of a nonlinear ion acoustic wave: ∂n∂τ + α2n ∂n∂ξ + α3 ∂3n∂ξ3 + α1(8π)1/2 P  ∫ −∞+∞ ∂n∂ξ′ dξ′ξ − ξ′ = 0, where n, ξ, and τ are normalized wave amplitude, space, and time coordinates, and α1, α2, α3 are parameters which depend on the relative strengths of Landau damping, nonlinearity, and dispersion. The first three terms constitute the Korteweg‐deVries equation, and the last term represents the effect of Landau damping. The equation conserves the number of particles but the wave energy can be shown to decay always. It is demonstrated that an initial waveform may either steepen or not depending on the relative size of the nonlinearity as compared to Landau damping. It is also shown that the Landau damping term causes the amplitude of a solitary wave to decay with time as (τ+τ0)−2.

Nonlinear Theory of Ion Acoustic Waves with Landau Damping

We analyze the propagation of a short intense laser pulse in underdense cold plasma. When no electron cavitation is present, a global invariant [ital H] is obtained, and its relation with self-focusing is studied. For relativistic self-focusing, [ital H][lt]0 is a sufficient and necessary condition. For relativistic and ponderomotive self-focusing, [ital H][lt]0 is sufficient but not necessary. Numerical simulations are performed to confirm the above points.

Necessary and sufficient conditions for self-focusing of short ultraintense laser pulse in underdense plasma.

A simple model for a new instability resulting from particles trapped in a large-amplitude electrostatic wave is invoked to explain the generation of satellite frequencies in a recently reported experiment by Wharton, Malmberg, and O'Neil. The model predicts satellites on the large-amplitude wave at a frequency separation proportional to $\sqrt{E}$, where $E$ is the amplitude of the large wave. The predicted growth rates reasonably account for the observed growth of these satellites.

Trapped-Particle Instability

The physical mechanism for the generation of very high ``dc'' magnetic fields in the interaction of ultraintense short laser pulse with an overdense plasma target originates in the spatial gradients and nonstationary character of the ponderomotive force. A set of model equations to determine the evolution of the ``dc'' fields is derived and it is shown that the ``dc'' magnetic field is of the same order of magnitude as the high frequency laser magnetic field.

R. N. Sudan

Papers

Damping of Solitary Waves

Nonlinear Theory of Ion Acoustic Waves with Landau Damping

Necessary and sufficient conditions for self-focusing of short ultraintense laser pulse in underdense plasma.

Trapped-Particle Instability

Mechanism for the generation of 10(9) G magnetic fields in the interaction of ultraintense short laser pulse with an overdense plasma target.