WorldCat Identities


Works: 70 works in 72 publications in 1 language and 72 library holdings
Classifications: QC718,
Publication Timeline
Comments on the Colliding Beam Fusion Reactor Proposed by Rostoker, Binderbauer and Monkhorst for Use with the p-11B Fusion Reaction( Book )

2 editions published in 1998 in English and held by 1 WorldCat member library worldwide

We examine the various dissipative processes affecting the colliding beam fusion reactor (CBFR) recently proposed by Rostoker, Binderbaner and Monkhorst (RBM) for use with the p-11B fusion reaction. We conclude that the CBFR equilibrium cannot be sustained for long enough to permit net fusion gain, because of the many collisional processes which occur orders of magnitude faster than fusion, and result in particle loss, energy dissipation, and/or detuning of the resonant energy for the p-11B reaction. Fokker Planck analyses of each process are performed. The calculations of RBM are critically reviewed to elucidate the source of disagreements with the present work. We also briefly discuss technology issues, especially the inefficiency of beam trapping in the device, and the unavailability of compact beam sources as assumed by RBM for naval applications
Direct-Drive Laser Target Designs for Sub-MegaJoule Energies( )

1 edition published in 2007 in English and held by 0 WorldCat member libraries worldwide

New direct-drive laser target designs with KrF laser light take advantage of the shorter wavelength to lower the laser energy required for substantial gain (>30x) to sub-MJ level. These low laser-energy pellets are useful in systems that could form an intermediate step towards fusion energy, such as the proposed Fusion Test Facility [S.P. Obenschain, et al, Phys. Plasmas 13, 056320 (2006)]. The short wavelength laser should allow higher intensity (and higher pressure) without increasing the risk of laser-plasma instabilities. The higher pressure in turn allows higher velocities to be achieved while keeping the low aspect ratios required for hydrodynamic stability. The canonical laser energy has been chosen to be 500 kJ. A target design is presented with various laser pulse shapes and both 1D and 2D simulation results are shown. The sensitivity of these targets to both low-mode and high-mode perturbations is examined. The analysis and simulations in this paper indicate that significant gain (G=57) can be achieved for these targets even in the presence of hydrodynamic instabilities
Perturbation Evolution Started by Richtmyer-Meshkov Instability in Planar Laser Targets( )

1 edition published in 2006 in English and held by 0 WorldCat member libraries worldwide

The first observations of the interaction of the Richtmyer-Meshkov (RM) instability with reflected shock and rarefaction waves in laser-driven targets are reported. The RM growth is started by a shock wave incident upon a rippled interface between low-density foam and solid plastic. Subsequent interaction of secondary rarefaction and/or shock waves arriving from the ablation front and the rear surface of the target with the RM-unstable interface stops the perturbation growth and reverses its direction. The ensuing exponential Rayleigh-Taylor growth thus can sometimes proceed with an inverted phase
Reflective Probing of the Electrical Conductivity of Hot Aluminum in the Solid, Liquid and Plasma Phases( )

1 edition published in 1997 in English and held by 0 WorldCat member libraries worldwide

The physics of dense aluminum in transition between metallic and insulating states of the solid, liquid, and plasma phases is probed in thermally equilibrated, inertially confined, laser heated targets. Time resolved laser probes measure the reflectivity of thin aluminum layers embedded inside the target. The electrical conductivity is inferred from the reflectivity with a free-electron Drude conduction model. It is found to be sharply below liquid aluminum values and differs by at least an order of magnitude from current theoretical predictions
Proton Irradiation of InAs/AlSb/GaSb Resonant Interband Tunneling Diodes( )

1 edition published in 2001 in English and held by 0 WorldCat member libraries worldwide

Peak current densities of InAs/AlSb/GaSb/AlSb/InAs resonant interband tunneling diodes (RITD) grown by molecular beam epitaxy have been measured as a function of the growth temperature. The growth procedures were designed to produce nominally identical AlSb tunneling barriers. The variations observed in the peak current for positive bias are consistent with the barrier on the substrate side of the RITD becoming effectively thicker for diodes grown at high temperatures. Plan-view in situ scanning tunneling microscopy (STM) measurements indicate that smoother AlSb barriers are grown at high temperature. The growth temperature dependence of the peak current density and STM results are consistent, because tunneling is highly dependent on barrier thickness. While the high and low temperature growths were designed to have the same barrier thickness, the large current flowing through the thin areas of a rough barrier result in an effectively thinner barrier compared to the smooth one
Propagation of Intense, Short Laser Pulses in the Atmosphere( )

1 edition published in 2002 in English and held by 0 WorldCat member libraries worldwide

The propagation of short, intense laser pulses in the atmosphere may have applications in the areas of active and passive remote sensing, electronic countermeasures, and induced electric discharges. For example, localized ultraviolet radiation generated at a remote distance can provide a source for active fluorescence spectroscopy of biological and chemical agents in the atmosphere. The generated directed pulses of intense white light may find applications in the areas of hyperspectral imaging and differential absorption spectroscopy. The propagation of short, intense laser pulses through the atmosphere is investigated. A 3D, nonlinear propagation equation is derived which includes the effects of dispersion, nonlinear self-focusing due bound electrons, stimulated molecular Raman scattering, multiphoton and tunneling ionization, pulse energy depletion due to ionization, relativistic focusing and ponderomotively excited plasma wakefields. A method for generating a remote spark in the atmosphere is proposed. Examples involving beam focusing, compression, ionization. and white light generation are studied by numerically solving the full set of 3D, nonlinear propagation equations. Coupled equations for the spot size, plasma density and power, allowing for pulse energy depletion due to ionization are derived, demonstrating the absence of extended self-guided propagation
NRL Plasma Formulary by J. D Huba( )

2 editions published between 2002 and 2006 in English and held by 0 WorldCat member libraries worldwide

The NRL Plasma Formulary originated over twenty five years ago and has been revised several times during this period
Advanced Pulsed Power Concept and Component Development for KrF Laser IFE( )

1 edition published in 2002 in English and held by 0 WorldCat member libraries worldwide

The Electra advanced pulsed power development program has the goal of developing and demonstrating pulsed power technology that is applicable for KrF (krypton fluoride) Laser IFE (inertial fusion energy). The application presents efficiency, lifetime and cost challenges that mandate the use of advanced pulse compression topologies. In turn, these advanced topologies require the development of critical components and the establishment of engineering criteria for use in designing them. The component most critical to realizing any of the advanced topologies under study is the primary energy transfer switch. Therefore, the program has been developing an advanced optically-triggered and pumped solid state switch that is expected to meet the efficiency, lifetime and cost requirements of an IFE driver. Liquid dielectric breakdown studies are also underway, with the intent to develop design criteria relevant to the large electrically stressed areas associated with a viable KrF IFE power plant. KrF IFE pulse compression and component concepts will be discussed as well as the most recent results from the solid-state switch development and liquid dielectric test efforts
High-Gain Direct-Drive Target Design for Laser Fusion (Preprint)( )

1 edition published in 2000 in English and held by 0 WorldCat member libraries worldwide

A new laser fusion target concept is presented with a predicted energy gain of 125 using a 1.3 MJ KrF laser. This energy gain is sufficiently high for an economically attractive fusion reactor. X-rays from high- and low-Z materials are used in combination with a low-opacity ablator to spatially tune the isentrope, thereby providing both high fuel compression and a reduction of the ablative Rayleigh-Taylor instability
An Experimental Benchmark for Improved Simulation of Absolute Soft X-Ray Emission from Polystyrene Targets Irradiated With the Nike Laser( )

1 edition published in 2005 in English and held by 0 WorldCat member libraries worldwide

Absolutely calibrated, time-resolved spectral intensity measurements of soft x-ray emission from laser-irradiated polystyrene targets are compared to radiation-hydrodynamic simulations that include our new postprocessor, Virtual Spectro. This new capability allows a unified, detailed treatment of atomic physics and radiative transfer in non-LTE conditions for simple spectra from low-Z materials as well as complex spectra from high-Z materials. The excellent agreement (within a factor approximately 1.5) demonstrates the powerful predictive capability of the codes for the complex conditions in the ablating plasma. The absolute spectral intensity measurements were made in the XUV region (hv approximately 0.1-1.0 keV) with transmission grating spectrometers with good time resolution (t approximately 0.3 ns) and moderate spectral resolution (E/delta E approximately 10). Comparison to data with high spectral resolution (E/delta E approximately 1000) emphasizes the importance of including radiation coupling in the quantitative simulation of emission spectra
Development of Electron Beam Pumped KrF Lasers for Fusion Energy( )

1 edition published in 2008 in English and held by 0 WorldCat member libraries worldwide

Direct drive with krypton fluoride (KrF) lasers is an attractive approach to inertial fusion energy (IFE): KrF lasers have outstanding beam spatial uniformity, which reduces the seed for hydrodynamic instabilities; they have short wavelength (248 nm) that increases the rocket efficiency and raises the threshold for deleterious laser-plasma instabilities; they have the capability for zooming, i.e. decreasing the spot size to follow an imploding pellet and thereby increase efficiency; and they have a modular architecture, which reduces development costs. Numerical 1-D simulations have shown that a target driven by a KrF laser can have a gain above 125 [1,2], which is ample for a fusion system. Simulations of the pellet burn in 2-D and 3-D are underway. In addition to these laser-target advantages, the Sombrero Power Plant study showed a KrF based system could lead to an economically attractive power plant [3]. In view of these advances, several world-wide programs are underway to develop KrF lasers for fusion energy. These include programs in Japan [4, 5], China [6], Russia [7], and The United Kingdom [8]. There was also a large program in the United States [9]. The paper here concentrates on current research in the US with two lasers at the Naval Research Laboratory: The Electra laser [10] is a 400-700 J repetitively pulsed system that is being used to develop the technologies that meet the fusion requirements for rep-rate, durability, efficiency and cost. The Nike laser [11] is a 3-5 kJ single shot device that is used to study KrF issues with full-scale electron beam diodes
Broadband Plasma Impedance Measurements and Determination of Plasma Parameters( )

1 edition published in 2004 in English and held by 0 WorldCat member libraries worldwide

A small spherical probe is used in conjunction with a network analyzer to determine the impedance of the probe-plasma system over a wide frequency range. Impedance curves are in good agreement with accepted circuit modes with plasma-sheath and electron plasma frequency resonances easily identifiable. Phase measurements show clear transitions between capacitive and inductive modes as predicted by the model. Sheath thickness and absolute electron density are determined from the location of these transitions. In addition, much larger power absorption is observed at the sheath plasma resonance than is predicted by collisional absorption
Observation of Rayleigh-Taylor Growth to Short Wavelengths on Nike( )

1 edition published in 1999 in English and held by 0 WorldCat member libraries worldwide

The uniform and smooth focal profile of the Nike KrF laser [S. Obenschain, et. al., Phys. Plasmas 3, 1996 (2098)] was used to ablatively accelerate 40 micrometer thick polystyrene planar targets with pulse shaping to minimize shock heating of the compressed material. The foils had imposed small amplitude sinusoidal wave perturbations of 60, 30, 20, and 12.5 micrometer wavelength. The shortest wavelength is near the ablative stabilization cutoff for Rayleigh-Taylor growth. Modification of saturated wave structure due to random laser imprint was observed. Excellent agreement was found between the two dimensional simulations and experimental data for most cases where laser imprint was not dominant
The Precision Expandable Radar Calibration Sphere (PERCS) With Applications for Laser Imaging and Ranging( )

1 edition published in 2008 in English and held by 0 WorldCat member libraries worldwide

The Naval Research Laboratory will provide an orbiting calibration sphere to be used with ground-based laser imaging telescopes and HF radio systems. The Precision Expandable Radar Calibration Sphere (PERCS) is a practical, reliable, high-performance HF calibration sphere and laser imaging target to orbit at about 600 km altitude. The sphere will be made of a spherical wire frame with aspect independent radar cross section in the 3 to 35 MHz frequency range. The necessary launch vehicle to place the PERCS in orbit will be provided by the Department of Defense Space Test Program. The expandable calibration target has a stowed diameter of 1 meter and a fully deployed diameter of 10.2 meters. A separate deployment mechanism is provided for the sphere. After deployment the Precision Expandable Radar Calibration Sphere (PERCS) with 180 vertices will be in a high inclination orbit to scatter radio pulses from a number of ground systems, including (1) over-the-horizon (OTH) radars operated by the United States and Australia; (2) high power HF facilities such as HAARP in Alaska, EISCAT in Norway, and Arecibo in Puerto Rico; (3) the chain of high latitude SuperDARN radars used for auroral region mapping; and (4) HF direction finding for Navy ships. With the PERCS satellite, the accuracy of HF radars can be periodically checked for range, elevation, and azimuth errors. In addition, each of the 360 vertices on the PERCS sphere will support an optical retro-reflector for operations with ground laser facilities used to track satellites. The ground laser systems will be used to measure the precise location of the sphere within one cm accuracy and will provide the spatial orientation of the sphere as well as the rotation rate. The Department of Defense facilities that can use the corner-cube reflectors on the PERCS include (1) the Air Force Maui Optical Site (AMOS), (2) the
On Plasma Sheath Resonant Energy Absorption in Collisionless Plasmas( )

1 edition published in 2004 in English and held by 0 WorldCat member libraries worldwide

We have performed experiments designed to investigate the radiation characteristics of a spherical capacitive probe in a plasma environment in the large Space Physics Simulation Chamber at the Naval Research Laboratory. In the process we are able to approximate plasma density and electron neutral collision frequency in simulated space plasma environments consistent with earlier experimental efforts using plasma impedance probes. By using only the S(sub 11)-parameter outputs of a network analyzer, or the reflection coefficients, we are able to unfold both these quantities with measured data sets. In addition, we observe significant energy absorption at frequencies much less than the plasma frequency which we associate with a sheath-plasma resonance. This report is an exposition of this method along with data results and a comparison to theory
Measurements of Low-Level Prepulse on Nike KrF Laser (Preprint)( )

1 edition published in 2005 in English and held by 0 WorldCat member libraries worldwide

The krypton fluoride (KrF) laser is a leading candidate driver for inertial fusion energy. Some of the current fusion target designs call for targets with thin metallic coatings. These targets could be particularly susceptible to preheat by a low-level laser prepulse. Knowledge of the prepulse can be important in understanding and modeling the behavior of such targets. This paper presents measurements of low-level prepulse on target with the Nike KrF laser. Sources of prepulse are discussed and measurements are performed under several specific laser conditions in order to evaluate the relative contribution of these sources to the overall prepulse. Prepulse is found to be approx. 2 x 10( -7) from peak intensity for approximately 120 ns prior to the main laser pulse. Prepulse energy density on target is approx. 2 J/cm(2). The first laser amplifier in the time- and angle-multiplexed section of the laser is found to be the dominant source of prepulse
Maximal Sensitive Dependence and the Optimal Path to Epidemic Extinction( )

1 edition published in 2010 in English and held by 0 WorldCat member libraries worldwide

Extinction of an epidemic or a species is a rare event that occurs due to a large, rare stochastic fluctuation. Although the extinction process is dynamically unstable, it follows an optimal path that maximizes the probability of extinction. We show that the optimal path is also directly related to the finite-time Lyapunov exponents of the underlying dynamical system in that the optimal path displays maximum sensitivity to initial conditions. We consider several stochastic epidemic models, and examine the extinction process in a dynamical systems framework. Using the dynamics of the finite-time Lyapunov exponents as a constructive tool, we demonstrate that the dynamical systems viewpoint of extinction evolves naturally toward the optimal path
Quasi-Analytic Models for Density Bubbles and Plasma Clouds in the Equatorial Ionosphere( )

1 edition published in 2006 in English and held by 0 WorldCat member libraries worldwide

The equatorial ionosphere contains imbedded bubbles that rise though a horizontally stratified plasma. The motion of the bubbles are affect by gravity, neutral winds or external electric fields which produce electric fields in the F-Region density perturbations of the bubbles. Exact solutions for the electric potentials are derived assuming linear or circular symmetry to the density structures imbedded in the background plasma. A wide variety of analytic solutions for electric potentials are found for both density cavities and density enhancements. An analytic description of a rising bubble can be constructed by attaching a tail to the top half of a circular hole to from the electron density solution. The potential for this plume structure is a weighted sum of the analytic solutions for each separate piece. Using this electric potential, quasi-analytic solutions for the transport of the bubbles are derived using the continuity equation for the plasma with production and loss terms neglected. The analytic models of the electric fields provide incompressible motion that transports the locations of plasma cells but does not change the density of the plasma in each cell. This Lagrangean approach employs a time dependent coordinate mapping of the undisturbed layer grid. Using internal electric potentials of the bubbles and external polarizations of the F-layer as a whole, a transport model yields tilted plasma plumes that move through the F-Region. This time-dependent computer model provides useful plasma densities in a fraction of the time for fully numerical simulations
Optimization and Stability Control of Relativistic and Ponderomotive Self-Channeling of Ultra-Powerful Pulses in Underdense Plasma( )

1 edition published in 2004 in English and held by 0 WorldCat member libraries worldwide

Stable formation of multi-PW relativistic channels in underdense plasma, with the power exceeding 10,000 critical powers and the peak channel intensity in the 1O to the 23rd power W/cm2 range, can be established using an appropriate gradient of electron density at the first stage of the self-channeling, which initiates the process of stable multi-stage relativistic and ponderomotive self-channeling
Preliminary Composite Channel Model for the Mobile User Objective System Including Ionospheric Scintillation and Terrestrial Multipath Effects( )

1 edition published in 2004 in English and held by 0 WorldCat member libraries worldwide

A composite channel model, which combines ionospheric scintillation fading and terrestrial multipath effects, has been developed for the new satellite communications system, the Mobile User Objective System (MUOS). We numerically solve the composite model and compute an effective decorrelation time and coherence bandwidth for the composite channel. We find that, under typical conditions, the effective channel decorrelation time and coherence bandwidth can be different from the ionospheric or terrestrial channel parameters
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English (22)