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T. W. Phillips

Bio: T. W. Phillips is an academic researcher from Lawrence Livermore National Laboratory. The author has contributed to research in topics: Inertial confinement fusion & Laser. The author has an hindex of 30, co-authored 75 publications receiving 4688 citations.


Papers
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Journal ArticleDOI
TL;DR: An intense collimated beam of high-energy protons is emitted normal to the rear surface of thin solid targets irradiated at 1 PW power and peak intensity 3x10(20) W cm(-2).
Abstract: An intense collimated beam of high-energy protons is emitted normal to the rear surface of thin solid targets irradiated at 1 PW power and peak intensity 3x10(20) W cm(-2). Up to 48 J ( 12%) of the laser energy is transferred to 2x10(13) protons of energy >10 MeV. The energy spectrum exhibits a sharp high-energy cutoff as high as 58 MeV on the axis of the beam which decreases in energy with increasing off axis angle. Proton induced nuclear processes have been observed and used to characterize the beam.

1,496 citations

Journal ArticleDOI
TL;DR: In this paper, the energy content, spectra, and angular patterns of the photon, electron, and ion radiations have all been diagnosed in a number of ways, including several novel (to laser physics) nuclear activation techniques.
Abstract: In recent Petawatt laser experiments at Lawrence Livermore National Laboratory, several hundred joules of 1 μm laser light in 0.5–5.0-ps pulses with intensities up to 3×1020 W cm−2 were incident on solid targets and produced a strongly relativistic interaction. The energy content, spectra, and angular patterns of the photon, electron, and ion radiations have all been diagnosed in a number of ways, including several novel (to laser physics) nuclear activation techniques. About 40%–50% of the laser energy is converted to broadly beamed hot electrons. Their beam centroid direction varies from shot to shot, but the resulting bremsstrahlung beam has a consistent width. Extraordinarily luminous ion beams (primarily protons) almost precisely normal to the rear of various targets are seen—up to 3×1013 protons with kTion∼several MeV representing ∼6% of the laser energy. Ion energies up to at least 55 MeV are observed. The ions appear to originate from the rear target surfaces. The edge of the ion beam is very shar...

868 citations

Journal ArticleDOI
TL;DR: Boehly et al. as mentioned in this paper used CR-39 nuclear track detectors in conjunction with magnets and/or special ranging filters for high-resolution spectrometry of charged particles from inertial confinement-fusion (ICF) experiments.
Abstract: High-resolution spectrometry of charged particles from inertial-confinement-fusion (ICF) experiments has become an important method of studying plasma conditions in laser-compressed capsules. In experiments at the 60-beam OMEGA laser facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)], utilizing capsules with D2, D3He, DT, or DTH fuel in a shell of plastic, glass, or D2 ice, we now routinely make spectral measurements of primary fusion products (p, D, T, 3He, α), secondary fusion products (p), “knock-on” particles (p, D, T) elastically scattered by primary neutrons, and ions from the shell. Use is made of several types of spectrometers that rely on detection and identification of particles with CR-39 nuclear track detectors in conjunction with magnets and/or special ranging filters. CR-39 is especially useful because of its insensitivity to electromagnetic noise and its ability to distinguish the types and energies of individual particles, as illustrated here by detailed calibrations of its response to 0.1–13.8 MeV protons from a Van de Graaff accelerator and to p, D, T, and α from ICF experiments at OMEGA. A description of the spectrometers is accompanied by illustrations of their operating principles using data from OMEGA. Sample results and discussions illustrate the relationship of secondary-proton and knock-on spectra to capsule fuel and shell areal densities and radial compression ratios; the relationship of different primary fusion products to each other and to ion temperatures; the relationship of deviations from spherical symmetry in particle yields and energies to capsule structure; the acceleration of fusion products and the spectra of ions from the shell due to external fields; and other important physical characteristics of the laser-compressed capsules.

213 citations

Journal ArticleDOI
TL;DR: A quantitative comparison of the high energy electrons and the bremsstrahlung spectrum, as measured by photonuclear reaction yields, including the photoinduced fission of 238U is reported.
Abstract: A new regime of laser-matter interactions in which the quiver motion of plasma electrons is fully relativistic, with energies extending well above the threshold for nuclear processes, is studied using a petawatt laser system. In solid target experiments with focused intensities exceeding 10(20) W/cm(2), high energy electron generation, hard bremsstrahlung, and nuclear phenomena have been observed. We report here a quantitative comparison of the high energy electrons and the bremsstrahlung spectrum, as measured by photonuclear reaction yields, including the photoinduced fission of 238U.

195 citations

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TL;DR: In this paper, grid deflectometry techniques have been applied to proton radiography to obtain precise measurements of proton beam angles caused by electromagnetic fields in laser produced plasmas.
Abstract: Laser driven proton beams have been used to diagnose transient fields and density perturbations in laser produced plasmas. Grid deflectometry techniques have been applied to proton radiography to obtain precise measurements of proton beam angles caused by electromagnetic fields in laser produced plasmas. Application of proton radiography to laser driven implosions has demonstrated that density conditions in compressed media can be diagnosed with million electron volt protons. This data has shown that proton radiography can provide unique insight into transient electromagnetic fields in super critical density plasmas and provide a density perturbation diagnostics in compressed matter.

165 citations


Cited by
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Journal ArticleDOI
TL;DR: 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 as mentioned in this paper.
Abstract: 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...

1,601 citations

Journal ArticleDOI
TL;DR: In this paper, an attempt is made to explain the physical process present that will explain the presence of these energetic protons, as well as explain the number, energy, and angular spread of the protons observed in experiment.
Abstract: An explanation for the energetic ions observed in the PetaWatt experiments is presented. In solid target experiments with focused intensities exceeding 1020 W/cm2, high-energy electron generation, hard bremsstrahlung, and energetic protons have been observed on the backside of the target. In this report, an attempt is made to explain the physical process present that will explain the presence of these energetic protons, as well as explain the number, energy, and angular spread of the protons observed in experiment. In particular, we hypothesize that hot electrons produced on the front of the target are sent through to the back off the target, where they ionize the hydrogen layer there. These ions are then accelerated by the hot electron cloud, to tens of MeV energies in distances of order tens of μm, whereupon they end up being detected in the radiographic and spectrographic detectors.

1,485 citations

Journal ArticleDOI
TL;DR: In this paper, a number of consequences of relativistic-strength optical fields are surveyed, including wakefield generation, a relativistically version of optical rectification, in which longitudinal field effects could be as large as the transverse ones.
Abstract: 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.

1,459 citations

Journal ArticleDOI
TL;DR: An overview of the state of the art of ion acceleration by laser pulses as well as an outlook on its future development and perspectives are given in this article. But the main features observed in the experiments, the observed scaling with laser and plasma parameters, and the main models used both to interpret experimental data and to suggest new research directions are described.
Abstract: Ion acceleration driven by superintense laser pulses is attracting an impressive and steadily increasing effort. Motivations can be found in the applicative potential and in the perspective to investigate novel regimes as available laser intensities will be increasing. Experiments have demonstrated, over a wide range of laser and target parameters, the generation of multi-MeV proton and ion beams with unique properties such as ultrashort duration, high brilliance, and low emittance. An overview is given of the state of the art of ion acceleration by laser pulses as well as an outlook on its future development and perspectives. The main features observed in the experiments, the observed scaling with laser and plasma parameters, and the main models used both to interpret experimental data and to suggest new research directions are described.

1,221 citations