A5073640913- Laser-induced spectroscopy and plasma
- Laser-Plasma Interactions and Diagnostics
- Ionosphere and magnetosphere dynamics
- Magnetic confinement fusion research
- Solar and Space Plasma Dynamics
- Laser-Matter Interactions and Applications
- Fluid Dynamics and Turbulent Flows
- Spectroscopy Techniques in Biomedical and Chemical Research
- Cinema and Media Studies
- Meteorological Phenomena and Simulations
- Laser Design and Applications
- Advanced Fiber Laser Technologies
- Dust and Plasma Wave Phenomena
- Plasma Diagnostics and Applications
- Atomic and Molecular Physics
- Quantum optics and atomic interactions
- Media Studies and Communication
- Nonlinear Photonic Systems
- Shakespeare, Adaptation, and Literary Criticism
- Plasma Applications and Diagnostics
- Aerosol Filtration and Electrostatic Precipitation
- Logic, Reasoning, and Knowledge
- Data Management and Algorithms
- Rough Sets and Fuzzy Logic
- Spectroscopy and Quantum Chemical Studies
University of Rhode Island
2024
Los Alamos National Laboratory
1999-2022
Rhode Island College
2015-2021
Clark University
2021
Lodestar Research Corporation (United States)
2012-2015
Energetics (United States)
2012-2013
University of California, San Diego
2012-2013
University of Rochester
2012-2013
Université Toulouse III - Paul Sabatier
1989-2008
Centre National de la Recherche Scientifique
1982-2008
L.A. Zadeh's (1975) possibility theory is used as a general framework for modeling temporal knowledge pervaded with imprecision or uncertainty. Ill-known dates, time intervals fuzzy boundaries, durations, and uncertain precedence relations between events can be dealt in this approach. An explicit representation (in terms of distributions) the available information, which may neither precise nor certain, maintained. Deductive patterns reasoning involving and/or are established, combination...
Scattering of laser light by stimulated Brillouin scattering (SBS) and Raman (SRS) is a concern for indirect drive inertial confinement fusion (ICF). The hohlraum designs the National Ignition Facility (NIF) raise particular concerns due to large scale homogeneity plasmas within them. Experiments at Nova have studied laser–plasma interactions length that mimic many characteristics NIF plasmas. Filamentation SBS SRS been investigated as function beam smoothing plasma conditions. Narrowly...
Results are presented for an extensive study of strong Langmuir turbulence (SLT) in plasmas excited near the critical density by intense coherent radiation beams. The nominal parameters HF heating experiments imply that ionospheric plasma is such a state. A large body experimental data exists, particularly from incoherent scatter radar (ISR) measurements HF‐enhanced fluctuation levels. Long‐time simulations Zakharov's model SLT and related theoretical arguments have led to new conclusions...
Plasmon wave packets are shown to be nucleated in narrow density holes which the remnants of previous generations ``burnt out'' cavitons. The proximity nucleation length scales those dissipation precludes possibility a self-similar inertial range for wide parameters. mechanism may also arise other contexts.
This paper is mainly devoted to the comparison between calculation and experimental results of primary secondary streamer development in a point-to-plane positive corona discharge dry air at atmospheric pressure. The qualitative agreement based on hydrodynamics approximation shows that O radical produced which good with recent literature measurements using TALIF diagnostics. However, production yield (in terms radicals per energy injected) more efficient than one. main characteristics are...
Convective instabilities in the strongly damped regime are shown to exhibit essential nonlinear behavior due laser hot spots when average intensity 〈I〉 approaches a critical threshold value ${\mathit{I}}_{\mathit{c}}$. The onset of this is formally signaled by divergence convective amplification 〈A〉as 〈I〉\ensuremath{\rightarrow}${\mathit{I}}_{\mathit{c}}$. An independent spot model random phase plate optics predicts that 〈A〉\ensuremath{\sim}1/(${\mathit{I}}_{\mathit{c}}$-〈I〉${)}^{2}$. A...
A quantitative theory of laser hot spots, which control plasma instabilities in real laser–plasma interactions, is presented the case random phase plate (RPP) optics. It shown that probability density intense spots with intensity I, Phot(I), given by Phot(I)∼(I/I02)exp(−I/I0) where I0 average intensity, and detailed amplitude variation field vicinity an spot uniquely specified optics deterministic. These may be source below threshold stimulated Raman scattering (SRS) its to super...
Kinetic simulations of backward stimulated Raman scattering (BSRS), where the Langmuir wave coherence time is greater than bounce for trapped electrons, yield transient reflectivity levels far above those predicted by fluidlike models. Electron trapping reduces damping and lowers frequency, leads to a secular phase shift between BSRS beat ponderomotive force. This detunes saturates similar effect, due ion trapping, saturation mechanism Brillouin scattering. Competition with forward SRS discussed.
Simulations of the long-time behavior Zakharov model Langmuir turbulence in two spatial dimensions reveal regimes where nucleation localized electrostatic fields previously burnt out density cavities is mechanism which sustains turbulence. Power spectrum diagnostics show that for moderate ion wave damping energy carried by states.
Thomson scattering is used to measure Langmuir waves (LW) driven by stimulated Raman (SRS) in a diffraction limited laser focal spot. For SRS at wave numbers klambda(D) less similar 0.29, where k the LW number and lambda(D) Debye length, multiple are detected attributed decay instability (LDI) primary LW. At greater single wave, frequency-broadened spectrum observed. The transition from fluid kinetic regime qualitatively consistent with particle-in-cell simulations crossing of LDI amplitude...
Detailed agreement with the experiments of Walsh, Villeneuve, and Baldis is obtained from a theory coupling stimulated Raman scattering Brillouin which incorporates nonlinear physics Zakharov model.
The general first-order parametric-instability equations for an inhomogeneous finite-size plasma are solved both analytically and numerically. It is shown that the wave-number mismatch introduced by gradients does not necessarily convert absolute instability into convective instability, even large systems. Absolute can also occur when length of system determined a smooth spatial dependence growth rate.
A wave spectrum peaked in angle and broadened number is found from a non-linear saturation theory for the decay-type parametric instability case of nearly equal electron ion temperatures. The dominant mechanism nonlinear damping Langmuir waves by induced scattering ions. resistivity transverse waves, including pump, obtained related conversion into longitudinal due to interaction with
Two-dimensional simulation studies are reported of the nonlinear development stimulated Raman scattering (SRS) from a compact laser hot spot using reduced model, which includes saturation by pump depletion, Langmuir wave decay cascades, collapse, and ponderomotive density profile modification. The needle-like intensity distribution in speckle arising random phase plate processed beam promotes backscatter SRS. dependence saturated reflectivity (the comparable magnitude) absorptivity, on ion...
Kinetic simulations and analysis show that backward stimulated Raman scattering (BSRS), in regimes of large linear Landau damping the primary Langmuir wave, attains levels greatly exceeding predictions models based on fixed damping. These are encountered plasma conditions expected for target designs to be fielded at National Ignition Facility [J. D. Lindl, Inertial Confinement Fusion (Springer-Verlag, New York, 1998)]. Trapped electrons wave have dual effect reducing its damping, thereby...
The power spectral densities of turbulent fluctuations computed from Zakharov's model are shown to have unexpected structure which results the coherent temporal evolution cavitons. These spectra features in common with measured during ionospheric heating.
Results of short-pulse, low--duty-cycle hf-heating experiments are shown to agree with predictions a model correlated, localized cavitons which undergo cycles nucleation, collapse, and burnout. Predicted ``free-mode'' spectral features associated the radiation Langmuir waves from collapsing observed. Single radar pulse data provide evidence that temporal correlations between caviton events present at early times following onset heating.
A statistical theory of strong Langmuir turbulence based on self-similarly collapsing cavitons is tested in one spatial dimension by study the solutions a set nonlinear equations which includes, as special case, Zakharov equations. Single-caviton exhibiting predicted self-similar collapse are verified numerically for initial conditions. Multiple-caviton systems studied over many generations collapse. Long-time--averaged spectra do not contain power-law inertial regime because nucleation at...
The extended Zakharov model of the two-plasmon decay instability in an inhomogeneous plasma [D. F. DuBois et al., Phys. Rev. Lett. 74, 3983 (1995); D. A. Russell and DuBois, 86, 428 (2001)] is further generalized to include evolution electron distribution function quasi-linear approximation [cf., e.g., K. Y. Sanbonmatsu al. Plasmas 7, 2824 (2000); paper presented at Workshop on SRS/SBS Saturation, Wente Vineyards, Livermore, CA, 2–5 April 2002]. This makes it possible investigate anomalous...
The reflectivity levels of stimulated Brillouin scattering (SBS) in recent large scale length laser plasma experiments is much lower than expected for conditions where the convective gain exponent to be [J. C. Fernández et al., Phys. Plasmas 4, 1849 (1997)]. Long-wavelength velocity fluctuations caused during formation process, or by parametric instabilities themselves, have been proposed as a mechanism detune SBS these and reduce its [W. L. Kruer 3, 382 (1996); H. A. Rose, 437 Evidence...
As Langmuir waves (LWs) are driven to large amplitude in plasma, they affected by nonlinear mechanisms. A global understanding, based on simulations and experiments, has emerged that identifies various regimes depending the dimensionless parameter kλD, where k is wave number λD electron Debye length. The phenomena arise due wave-wave wave-particle coupling mechanisms, this basic separation between fluid-like nonlinearities kinetic depends degree which ion Landau damping, as well trapping,...
The linear stability of multiple coherent laser beams with respect to two-plasmon-decay instability in an inhomogeneous plasma three dimensions has been determined. Cooperation between leads absolute long-wavelength decays, while shorter-wavelength shared waves are shown saturate convectively. multibeam, its absolutely unstable form, the lowest threshold for most cases considered. Nonlinear calculations using a three-dimensional extended Zakharov model show that Langmuir turbulence created...
Local intensity peaks, hot spots, in laser beams may initiate self-focusing, lieu of linear instabilities. If the spot power, P, contains several times critical Pc, and if plasma density, n, is small compared to nc, then on a time scale less than an acoustic transit across radius, τia, collapses, capturing order unity initial power. The collapse determined as universal function P/Pc τia. focal region moves towards with initially supersonic speed, decelerates it propagates. power this back...
Numerical studies of a model stimulated Raman scattering (SRS) coupled to Langmuir turbulence show that once the collisional threshold is exceeded for parametric decay SRS daughter wave noncollisional dissipation resulting from collapse can strongly saturate and reflectivity. The provides information on total rate hot electron generation. Scaling laws reflectivity as function laser plasma parameters are found.