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.

Plasmoids/flux ropes have been observed both at Earth's magnetopause as well in the magnetotail. Magnetic field measurements of such structures often reveal that rather than a minimum strength their centers expected from simple O‐type neutral line picture, they exhibit strong core field. To address this issue, two‐dimensional (2‐D) and 3‐D hybrid simulations are used to investigate magnetic structure reconnection layer general formation within plasmoids particular. The magnetotail is found...

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...

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...

Magnetic reconnection in a plane current sheet is investigated both two and three dimensions, using different types of simulation codes, Hall MHD, hybrid (electron fluid, kinetic ions), new code called Hall‐less hybrid. The latter code, which similar to the but has term removed, enables us clarify differences between ion MHD approaches. major findings this research are (1) Sweet‐Parker regime cannot be maintained does not reach steady state plasma for physically interesting parameter...

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 power transfer between crossed laser beams made possible by an ion-acoustic wave is studied. A simple formula derived for the steady-state transfer, which depends on two dimensionless parameters: ratio of incident beam intensities and normalized beamwidth. Numerical simulations show that transient larger than usually oscillates in time. convective depletion higher-frequency saturates more quickly damping wave.

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 rapid onset, with increasing laser intensity, of levels backward stimulated Raman scattering (BSRS) exceeding linear convective predictions, from single hot spots was predicted by simulations [Vu et al., Phys. Plasmas 9, 1745 (2002)], and has been observed [Montgomery 2311 (2002)] in nonlinear regimes dominated electron trapping. A theory for this inflation threshold is given here. the result competition between velocity diffusion trapping, exceeded when convectively amplified SRS...

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...

The ion acoustic dispersion relation for a plasma containing two distinct species is investigated over wide range of conditions. An approximate general analytic solution to the has been found, and shown, by comparison accurate numerical solutions individual modes, be remarkably precise. This provides first time systematic account totality modes two-ion system. It found that consist types modes: (a) at least one, and, most, weakly damped which ‖ωI/ωR‖≪1, (b) an infinity critically ωI/ωR≂−1....

Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation H. X. Vu, D. F. DuBois, A. Russell, J. Myatt; The reduced-description particle-in-cell model for the two plasmon decay instability. Physics of Plasmas 1 July 2010; 17 (7): 072701. https://doi.org/10.1063/1.3457927 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote...

The fully kinetic reduced-description particle-in-cell (RPIC) method has been applied to simulations of two-plasmon–decay (TPD) instability, driven by crossed laser beams, in an inhomogeneous plasma for parameters consistent with recent direct-drive experiments related laser-driven inertial fusion. nonlinear saturated state is characterized very spiky electric fields, Langmuir cavitation occurring preferentially inside density channels produced the ponderomotive beating beams and primary TPD...

The parametric coupling involving backward stimulated scattering of a laser and electron beam acoustic modes (BAM) is described as observed in particle-in-cell (PIC) simulations. BAM evolve from Langmuir waves (LW) the velocity distribution nonlinearly modified to be non-Maxwellian by Raman (BSRS). With marginal damping rate, can easily excited allow an extended chirping frequency occur later SRS pulses encounter distributions. Coincident with emergence this rapid increase BSRS...

Two-plasmon-decay (TPD) instability is identified as a potential source of target preheat in direct-drive-implosion experiments on OMEGA. A physical model electron heating developed that relies extended Zakharov simulations to predict the nonlinearly saturated Langmuir wave spectrum. Hot generation estimated via test-particle approach. It noted because relatively low areal density targets during time TPD instability, hot-electron recirculation and reheating are potentially important effects....

The kinetic reduced-description particle-in-cell simulation technique has been applied to study the nonlinear stage of two-plasmon–decay (TPD) instability in an inhomogeneous plasma driven by crossed laser beams. TPD is found be a prolific generator “cavitating” Langmuir turbulence. “cavitons”—localized longitudinal electric fields, oscillating near local electron frequency, trapped ponderomotive density depressions—collapse dimensions few Debye lengths, where field energy collisionlessly...

Numerical simulation results of stimulated Brillouin scattering (SBS) using HERCULES [H. X. Vu, J. Comput. Phys. 124, 417 (1996)], an adiabatic fluid-electron particle-in-cell (PIC) code, are presented. The these PIC simulations compared against fluid simulations, and good agreement is obtained for sufficiently weak laser intensities. When the intensity strong ion trapping to be significant, differ substantially. time nonlinear frequency shift in with analytical predictions. SBS reflectivity...

The potential for laser-plasma instability is a serious concern indirect-drive inertial confinement fusion (ICF), where laser beams illuminate the interior of cavity (called hohlraum) to produce x-rays imploding capsule symmetrically. speckled nature used in ICF an important factor processes. For example, models which calculate spatial growth convective by properly accounting speckles successfully predict observed onsets backscattering due stimulated Brillouin and Raman scattering...

Recent experiments have shown that low density foam layers can significantly mitigate the perturbing effects of beam nonuniformities affecting acceleration thin shells. This problem is studied parametrically with two-dimensional LASNEX [G. B. Zimmerman and W. L. Kruer, Comments Plasma Phys. Controlled Fusion 2, 51 (1975)]. Foam-buffered targets are employed, consisting typically 250 Å gold, 50 μm mg/cm3 C10H8O4 attached to a 10 foil. In simulation these were characteristically exposed 1.2...

We introduce two new and complementary simulation models, which have domains of quantitative agreement, for the self-consistent evolution electron distribution, Langmuir decay cascades, collapse. In our reduced-description particle-in-cell (RPIC) simulations, cascades cycles collapse are seen first time in particle simulation. The velocity distribution Zakharov model is evolved using quasilinear diffusion plus Cerenkov emission loss agrees expected with RPIC results. These techniques promise...

The power transfer between crossed laser beams made possible by an ion-acoustic wave is studied. with Gaussian intensity profiles shifts the beam centroids, and alters directions focal lengths. hot spots in their depends sensitively on whether associated filaments intersect.

Most recent experiments on the excitation of two plasmon-decay (TPD) instability involve a three-dimensional (3D) array overlapping laser beams. Our dimensional (2D) simulations suggested that Langmuir cavitation and collapse are important nonlinear saturation mechanisms for TPD. There quantitative differences in process 2D 3D. To address these other issues, we have developed 3D Zakharov code. It has been applied to study evolution TPD from absolute instabilities (arising geometries) state...