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A Description of a Shock Wave in Free Particle Hydrodynamics with Internal Magnetic Fields

Description: Abstract: "The structure of an extremely strong magnetohydrodynamic shock is discussed in the limit of no particle collisions. It is tentatively concluded that the shock transition takes place through the mechanism of a strong electric field produced by charge separation. The pressure in the shocked plasma is due primarily to a very high electron temperature. The ions, on the other hand, undergo an irreversible temperature change of only 3."
Date: February 19, 1957
Creator: Colgate, Stirling A.
Partner: UNT Libraries Government Documents Department

Warm wavebreaking of nonlinear plasma waves with arbitrary phase velocities

Description: A warm, relativistic fluid theory of a nonequilibrium, collisionless plasma is developed to analyze nonlinear plasma waves excited by intense drive beams. The maximum amplitude and wavelength are calculated for nonrelativistic plasma temperatures and arbitrary plasma wave phase velocities. The maximum amplitude is shown to increase in the presence of a laser field. These results set a limit to the achievable gradient in plasma-based accelerators.
Date: November 12, 2004
Creator: Schroeder, C.B.; Esarey, E. & Shadwick, B.A.
Partner: UNT Libraries Government Documents Department

Role of plasma edge in the direct launch Ion Bernstein Wave experiment in TFTR

Description: Two types of direct IBW launching, EPW {R_arrow} IBW and CESICW {R_arrow} IBW are investigated using two numerical codes, Full Hot Plasma Ray-Tracing Code and SEMAL Full Wave Slab Code, for the TFTR direct launch IBW experimental parameters. The measured density profiles (by microwave reflectometry) in TFTR appear to be satisfactory for IBW launching while the observed stored energy rise compared to the expected value (ray tracing + TRANSP) indicates only up to 50% of launched power is reaching the plasma core. Possible causes of IBW inefficiency are also discussed.
Date: June 1, 1997
Creator: Ono, M.; Cesario, R. & Bush, C.E.
Partner: UNT Libraries Government Documents Department

Observation of Secondary Plasma Waves in Laser-Plasma Interaction Experiments

Description: An experiment is described where the two products of the Langmuir Decay Instability (LDI) of a primary electron plasma wave have been observed and identified without any ambiguity. Primary Langmuir waves are driven by Stimulated Raman Scattering (SRS) of an incident laser which provides well-defined electron plasma waves. Thomson scattering of a short wavelength probe beam yields measurements of the amplitude of the waves resolved in time, space, wavelength and wavevector, that allow identification of the probed waves.
Date: December 8, 1999
Creator: Depierreux, S.; Labaune, C.; Baldis, H.A.; Fuchs, J. & Michard, A.
Partner: UNT Libraries Government Documents Department

Excitation of large-{kappa}{sub {theta}} ion-Bernstein waves in tokamaks

Description: The mode-converted ion-Bernstein wave excited in tokamaks is shown to exhibit certain very interesting behavior, including the attainment of very small poloidal phase velocities, the reversal of poloidal direction, and up-down asymmetries in propagation and damping. Because of these effects, this wave holds promise for channeling {alpha}-particle power to ions, something that would make a tokamak fusion reactor far more attractive than presently envisioned.
Date: September 1, 1994
Creator: Valeo, E. J. & Fisch, N. J.
Partner: UNT Libraries Government Documents Department

The electrostatic wake of a superthermal test electron in a magnetized plasma

Description: The electrostatic potential is determined for a test electron with {upsilon}{sub {parallel}} {much gt} {upsilon}{sub Te}, in a uniform magnetized plasma ({omega}{sub ce} {much gt} {omega}{sub pe}). In the frame of the test electron, part of the spatially oscillatory potential has spherical symmetry over the hemisphere to the rear of the electron and is zero ahead of the electron. A second part of different character, which makes the potential continuous at the plane containing the electron, is oscillatory in the radial direction but decreases almost monotonically in the axial direction.
Date: July 1, 1992
Creator: Ware, A.A. & Wiley, J.C.
Partner: UNT Libraries Government Documents Department

Investigation of electrostatic waves in the ion cyclotron range of frequencies in L-4 and ACT-1

Description: Electrostatic waves in the ion cyclotron range of frequencies (ICRF) were studied in the Princeton L-4 and ACT-1 devices for approximately ten years, from 1975 to 1985. The investigation began in the L-4 linear device, looking for the parametric excitation of electrostatic ion cyclotron waves in multi-ion-species plasmas. In addition, this investigation verified multi-ion-species effects on the electrostatic ion cyclotron wave dispersion religion including the ion-ion hybrid resonance. Finite-Larmor-radius modification of the wave dispersion relation was also observed, even for ion temperatures of T{sub i} {approx} 1/40 eV. Taking advantage of the relatively high field and long device length of L-4, the existence of the cold electrostatic ion cyclotron wave (CES ICW) was verified. With the arrival of the ACT-1 toroidal device, finite-Larmor-radius (FLR) waves were studied in a relatively collisionless warm-ion hydrogen plasma. Detailed investigations of ion Bernstein waves (IBW) included the verification of mode-transformation in their launching, their wave propagation characteristics, their absorption, and the resulting ion heating. This basic physics activity played a crucial role in developing a new reactor heating concept termed ion Bernstein wave heating. Experimental research in the lower hybrid frequency range confirmed the existence of FLR effects near the lower hybrid resonance, predicted by Stix in 1965. In a neon plasma with a carefully placed phased wave exciter, the neutralized ion Bernstein wave was observed for the first time. Using a fastwave ICRF antenna, two parasitic excitation processes for IBW -- parametric instability and density-gradient-driven excitation -- were also discovered. In the concluding section of this paper, a possible application of externally launched electrostatic waves is suggested for helium ash removal from fusion reactor plasmas.
Date: May 1, 1993
Creator: Ono, Masayuki
Partner: UNT Libraries Government Documents Department

Effects of Hyperbolic Rotation in Minkowski Space on the Modeling of Plasma Accelerators in a Lorentz Boosted Frame

Description: Laser driven plasma accelerators promise much shorter particle accelerators but their development requires detailed simulations that challenge or exceed current capabilities. We report the first direct simulations of stages up to 1 TeV from simulations using a Lorentz boosted calculation frame resulting in a million times speedup, thanks to a frame boost as high as gamma = 1300. Effects of the hyperbolic rotation in Minkowski space resulting from the frame boost on the laser propagation in the plasma is shown to be key in the mitigation of a numerical instability that was limiting previous attempts.
Date: September 21, 2010
Creator: Vay, J.-L.; Geddes, C. G. R.; Cormier-Michel, E. & Grote, D. P.
Partner: UNT Libraries Government Documents Department

Studies of Flows in Plasmas

Description: Note a pdf document "DOE-flow-final-report' should be attached. If it somehow is not please notify Walter Gekelman (gekelman@physics.ucla.edu) who will e mail it directly
Date: March 7, 2009
Creator: Gekelman, Walter; Morales, George & Maggs, James
Partner: UNT Libraries Government Documents Department

Calculation of Moments from Measurements by the Los Alamos Magnetospheric Plasma Analyzer

Description: The various steps involved in computing the moments (density, velocity, and temperature) of the ion and electron distributions measured with the Los Alamos Magnetospheric Plasma Analyzer (MPA) are described. The assumptions, constants, and algorithms contained in the FORTRAN code are presented, as well as the output parameters produced by the code.
Date: May 1, 1999
Creator: Thomsen, M. F.; Noveroske, E.; Borovsky, J. E. & McComas, D. J.
Partner: UNT Libraries Government Documents Department

Experimental observation of current generation by unidirectional electron plasma waves

Description: A slow wave structure was used to launch electron plasma waves traveling preferentially in one direction. The current generated by the waves was observed. The magnitude of the current can be estimated from momentum conservation in the wave-particle interaction process.
Date: August 1, 1978
Creator: Wong, K.L.
Partner: UNT Libraries Government Documents Department

The generalized accessibility and spectral gap of lower hybrid waves in tokamaks

Description: The generalized accessibility of lower hybrid waves, primarily in the current drive regime of tokamak plasmas, which may include shifting, either upward or downward, of the parallel refractive index (n{sub {parallel}}), is investigated, based upon a cold plasma dispersion relation and various geometrical constraint (G.C.) relations imposed on the behavior of n{sub {parallel}}. It is shown that n{sub {parallel}} upshifting can be bounded and insufficient to bridge a large spectral gap to cause wave damping, depending upon whether the G.C. relation allows the oblique resonance to occur. The traditional n{sub {parallel}} upshifting mechanism caused by the pitch angle of magnetic field lines is shown to lead to contradictions with experimental observations. An upshifting mechanism brought about by the density gradient along field lines is proposed, which is not inconsistent with experimental observations, and provides plausible explanations to some unresolved issues of lower hybrid wave theory, including generation of {open_quote}seed electrons.{close_quote}
Date: March 1, 1994
Creator: Takahashi, Hironori
Partner: UNT Libraries Government Documents Department

Hot-ion Bernstein wave with large k{sub parallel}

Description: The complex roots of the hot plasma dispersion relation in the ion cyclotron range of frequencies have been surveyed. Progressing from low to high values of perpendicular wave number k{perpendicular} we find first the cold plasma fast wave and then the well-known Bernstein wave, which is characterized by large dispersion, or large changes in k{perpendicular} for small changes in frequency or magnetic field. At still higher k{perpendicular} there can be two hot plasma waves with relatively little dispersion. The latter waves exist only for relatively large k{parallel}, the wave number parallel to the magnetic field, and are strongly damped unless the electron temperature is low compared to the ion temperature. Up to three mode conversions appear to be possible, but two mode conversions are seen consistently.
Date: January 1, 1995
Creator: Ignat, D. W. & Ono, M.
Partner: UNT Libraries Government Documents Department

Thermally Excited Proton Spin-Flip Laser Emission in Tokamaks

Description: Based on statistical thermodynamic fluctuation arguments, it is shown here for the first time that thermally excited spin-flip laser emission from the fusion product protons can occur in large tokamak devices that are entering the reactor regime of operation. Existing experimental data from TFTR supports this conjecture, in the sense that these measurements are in complete agreement with the predictions of the quasilinear theory of the spin-flip laser.
Date: July 1993
Creator: Arunasalam, V. & Greene, G. J.
Partner: UNT Libraries Government Documents Department

The dynamics of interacting nonlinearities governing long wavelength driftwave turbulence

Description: Because of the ubiquitous nature of turbulence and the vast array of different systems which have turbulent solutions, the study of turbulence is an area of active research. Much present day understanding of turbulence is rooted in the well established properties of homogeneous Navier-Stokes turbulence, which, due to its relative simplicity, allows for approximate analytic solutions. This work examines a group of turbulent systems with marked differences from Navier-Stokes turbulence, and attempts to quantify some of their properties. This group of systems represents a variety of drift wave fluctuations believed to be of fundamental importance in laboratory fusion devices. From extensive simulation of simple local fluid models of long wavelength drift wave turbulence in tokamaks, a reasonably complete picture of the basic properties of spectral transfer and saturation has emerged. These studies indicate that many conventional notions concerning directions of cascades, locality and isotropy of transfer, frequencies of fluctuations, and stationarity of saturation are not valid for moderate to long wavelengths. In particular, spectral energy transfer at long wavelengths is dominated by the E {times} B nonlinearity, which carries energy to short scale in a manner that is highly nonlocal and anisotropic. In marked contrast to the canonical self-similar cascade dynamics of Kolmogorov, energy is efficiently passed between modes separated by the entire spectrum range in a correlation time. At short wavelengths, transfer is dominated by the polarization drift nonlinearity. While the standard dual cascade applies in this subrange, it is found that finite spectrum size can produce cascades that are reverse directed and are nonconservative in enstrophy and energy similarity ranges. In regions where both nonlinearities are important, cross-coupling between the nolinearities gives rise to large no frequency shifts as well as changes in the spectral dynamics.
Date: September 1, 1993
Creator: Newman, D. E.
Partner: UNT Libraries Government Documents Department

Nonlinear instability and chaos in plasma wave-wave interactions, I., Introduction

Description: Conventional linear stability analyses may fail for fluid systems with an indefinite free energy functional. When such a system is linearly stable, it is said to possess negative energy modes. Instability may then occur either via dissipation of the negative energy modes, or nonlinearly via resonant wave-wave coupling, leading to explosive growth. In the dissipationless case, it is conjectured that intrinsic chaotic behavior may allow initially nonresonant systems to reach resonance by diffusion in phase space. In this and a companion paper [submitted to Physics of Plasmas], this phenomenon is demonstrated for a simple equilibrium involving cold counterstreaming ions. The system is described in the fluid approximation by a Hamiltonian functional and associated noncanonical Poisson bracket. By Fourier decomposition and appropriate coordinate transformations, the Hamiltonian for the perturbed energy is expressed in action-angle form. The normal modes correspond to Doppler-shifted ion-acoustic waves of positive and negative energy. Nonlinear coupling leads to decay instability via two-wave interactions, and to either decay or explosive instability via three-wave interactions. These instabilities are described for various (integrable) systems of waves interacting via single nonlinear terms. This discussion provides the foundation for the treatment of nonintegrable systems in the companion paper.
Date: November 1, 1994
Creator: Kueny, C. S. & Morrison, P. J.
Partner: UNT Libraries Government Documents Department

Fast ion-driven Bernstein instabilities

Description: We investigate a new mechanism, the two-energy-stream cyclotron instability, for fast ions (e.g., fusion products) to drive electrostatic waves and to slow down. The instability comes from a relativistic effect, which dominates conventional phase overtaking as the axial phase velocity exceeds the speed of light. Both a single particle model and a dispersion relation are developed in order to illuminate the physics insights and scaling laws. We present numerical results and discuss nonlinear processes. The mechanism is essential for the dynamics of the fast ions in both D-D and D-T devices.
Date: July 20, 1992
Creator: Chen, K. R.
Partner: UNT Libraries Government Documents Department

The electrostatic wake of a superthermal test electron in a magnetized plasma

Description: The electrostatic potential is determined for a test electron with {upsilon}{sub {parallel}} {much_gt} {upsilon}{sub Te}, in a uniform magnetized plasma ({omega}{sub ce} {much_gt} {omega}{sub pe}). In the frame of the test electron, part of the spatially oscillatory potential has spherical symmetry over the hemisphere to the rear of the electron and is zero ahead of the electron. A second part of different character, which makes the potential continuous at the plane containing the electron, is oscillatory in the radial direction but decreases almost monotonically in the axial direction.
Date: July 1, 1992
Creator: Ware, A. A. & Wiley, J. C.
Partner: UNT Libraries Government Documents Department

Structure and damping of toroidal drift waves (and their implications for anomalous transport)

Description: The conventional theory of high-n toroidal drift waves, based on the ballooning representation, indicates that shear-damping is generally reduced in a torus compared to its plane-slab value. It therefore describes the most unstable class of toroidal drift waves. However, modes of this type occur only i f the diamagnetic frequency {omega}*(r) has a maximum in r, and they affect only a small fraction, {Omicron}(1/n{sup l/2}), of the plasma radius around this maximum. Consequently they may produce little anomalous transport. In the present work we show that, within the ballooning description, there is another class of toroidal drift waves with very different properties to the conventional ones. The new modes have greater shear-damping (closer to that in a plane-slab) than the conventional ones and so have a higher instability threshold. However, they occur for any plasma profile and at all radii, and they have larger radial extent. Consequently they may produce much greater anomalous transport than the possibly benign conventional modes. This suggests a picture of anomalous transport in which the plasma profile is determined by marginal stability, but marginal to the new class of modes not to the conventional ones. This might explain why marginally stable profiles calculated for drift waves with plane-slab damping sometimes agree well with the profiles in toroidal experiments. It is also consistent with the fact that experimental profiles may exceed conventional toroidal instability thresholds. The new modes may also be related to the tong radial structures which appear in some plasma simulations and in experiments.
Date: May 1, 1993
Creator: Taylor, J. B.; Connor, J. & Wilson, H. R.
Partner: UNT Libraries Government Documents Department