Filters

Results

**1**-**10**of**393** Results

**1**-**10**of**393**. Search took:**0.023**secondsSort by: date | relevance |

Horton, W.

12th EFTC The twelfth European Fusion Theory Conference, 24-27 September 2007, Madrid, Spain

12th EFTC The twelfth European Fusion Theory Conference, 24-27 September 2007, Madrid, Spain

AbstractAbstract

[en] Microtearing modes are driven by combinations of the electron temperature gradient and the current density gradient, and thus may add to the anomalous electron thermal flux in current carrying plasmas. The problem has a long history in fusion research where generally the earlier results such as Connor et al. in PPCF (1990) find that the passing electron response and a stabilizing MHD response from Δ over come the destabilization from the trapped electrons. They conclude that a typical tokamak system is unlikely to have unstable microtearing modes. There is experimental and gyrokinetic simulation evidence suggesting the presence of microtearing modes perhaps coupled to the ETG modes. Without the temperature gradient we benchmark a gyro fluid code with simulations [Horton et al. PoP, 012902 (2007)] showing coherent structures and dramatic magnetic energy releases to the electron pressure from sheared magnetic fields -positive Δ

^{.}We perform a number of simulations looking for conditions when both the temperature gradient and the current density gradient allow sustain electromagnetic turbulence. (Author)Primary Subject

Source

111 p; 2007; p. 19; Editorial CIEMAT; Madrid (Spain); The twelfth European Fusion Theory Conference; Madrid (Spain); 24-27 Sep 2007

Record Type

Book

Literature Type

Conference

Country of publication

CHARGED-PARTICLE TRANSPORT THEORY, CLOSED PLASMA DEVICES, FLUID FLOW, FLUID MECHANICS, HEATING, HYDRODYNAMICS, INSTABILITY, ION SPECTROSCOPY, MECHANICS, MOTION, NUCLEAR REACTIONS, NUCLEOSYNTHESIS, PLASMA INSTABILITY, SPECTROSCOPY, SYNTHESIS, THERMONUCLEAR DEVICES, THERMONUCLEAR REACTORS, TOKAMAK DEVICES, TOKAMAK TYPE REACTORS, TRANSPORT THEORY

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

Horton, W.

Texas Univ., Austin (USA). Inst. for Fusion Studies

Texas Univ., Austin (USA). Inst. for Fusion Studies

AbstractAbstract

[en] A detailed analysis is given for each of the following chapters: (1) anomalous transport due to drift modes at low plasma pressure, (2) drift wave fluctuation spectra, and (3) anomalous transport from electromagnetic fluctuations

Primary Subject

Source

Sep 1981; 150 p; IFSR--35; Available from NTIS., PC A07/MF A01 as DE83000118

Record Type

Report

Report Number

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

Horton, W.

Texas Univ., Austin (USA). Inst. for Fusion Studies

Texas Univ., Austin (USA). Inst. for Fusion Studies

AbstractAbstract

[en] Theory and computer simulations are used to describe the inelastic vortex-vortex and vortex-wave interactions that lead to the quasi-coherent transport of plasma across the magnetic field. Monopole and dipole drift wave vortices with radii r

_{0}large compared with the ion inertial scale length /rho//sub s/ are shown to produce transport at the rate un/sub υ/∫dσ(b) ≤ n/sub υ/υ/sub de/r/sub o/ where n/sub υ/ is the vortex line density and dσ(b) is the inelastic collision cross-section for impact parameter b. The transport during collisions and mergings is evaluated from the evolution of a passively convected scalar concentration of test particles. 24 refs., 4 figsPrimary Subject

Secondary Subject

Source

Apr 1988; 40 p; IFSR--312; Available from NTIS, PC A03/MF A01; 1 as DE88009562

Record Type

Report

Report Number

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

Hamaguchi, S.; Horton, W.

Texas Univ., Austin, TX (USA). Inst. for Fusion Studies

Texas Univ., Austin, TX (USA). Inst. for Fusion Studies

AbstractAbstract

[en] With the use of consistent orderings in var-epsilon = ρ

_{s}/a and δ = k_{perpendicular}ρ_{s}model equations are derived for the drift instabilities from the electrostatic two-fluid equations. The electrical resistivity η included in the system allows the dynamics of both the collisional drift wave instability (η ≠ 0) and the collisionless ion temperature gradient driven instability (η = 0). The model equations used extensively in earlier nonlinear studies are obtained as appropriate limits of the model equations derived in the present work. The effects of sheared velocity flows in the equilibrium plasma and electron temperature fluctuations are also discussed. 14 refsPrimary Subject

Secondary Subject

Source

Oct 1990; 43 p; IFSR--462; CONTRACT FG05-80ET53088; NTIS, PC A03/MF A01 as DE91004301; OSTI; INIS; US Govt. Printing Office Dep

Record Type

Report

Report Number

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

Padhye, N.; Horton, W.

Univ. of Texas, Inst. for Fusion Studies, TX (United States). Funding organisation: USDOE Office of Energy Research, Washington, DC (United States)

Univ. of Texas, Inst. for Fusion Studies, TX (United States). Funding organisation: USDOE Office of Energy Research, Washington, DC (United States)

AbstractAbstract

[en] A low-dimensional Hamiltonian model is derived for the acceleration of ions in finite amplitude Alfven waves in a finite pressure plasma sheet. The reduced low-dimensional wave-particle Hamiltonian is useful for describing the reaction of the accelerated ions on the wave amplitudes and phases through the self-consistent fields within the envelope approximation. As an example, the authors show for a single Alfven wave in the central plasma sheet of the Earth's geotail, modeled by the linear pinch geometry called the Harris sheet, the time variation of the wave amplitude during the acceleration of fast protons

Primary Subject

Source

9 Oct 1998; 17 p; CONTRACT FG03-96ER54346; ALSO AVAILABLE FROM OSTI AS DE99000299; NTIS; US GOVT. PRINTING OFFICE DEP

Record Type

Report

Report Number

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

Liu, J.; Horton, W.

Texas Univ., Austin (USA). Inst. for Fusion Studies

Texas Univ., Austin (USA). Inst. for Fusion Studies

AbstractAbstract

[en] The nonlinear equations describing drift-Alfven solitary vortices in a low β, rotating plasma are derived. Two types of solitary vortex solutions along with their corresponding nonlinear dispersion relations are obtained. Both solutions have the localized coherent dilopar structure. The first type of solution belongs to the family of the usual Rossby or drift wave vortex, while the second type of solution is intrinsic to the electromagnetic perturbation in a magnetized plasma and is a complicated structure. While the first type of vortex is a solution to a second order differential equation the second one is the solution of a fourth order differential equation intrinsic to the electromagnetic problem. The fourth order vortex solution has two intrinsic space scales in contrast to the single space scale of the previous drift vortex solution. With the second short scale length the parallel current density at the vortex interface becomes continuous. As special cases the rotational electron drift vortex and the rotational ballooning vortex also are given. 10 refs

Primary Subject

Source

Dec 1985; 36 p; IFSR--214; Available from NTIS, PC A03/MF A01 as DE86005400

Record Type

Report

Report Number

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

Sugama, H.; Horton, W.

National Inst. for Fusion Science, Nagoya (Japan)

National Inst. for Fusion Science, Nagoya (Japan)

AbstractAbstract

[en] Neoclassical and anomalous transport fluxes are determined for axisymmetric toroidal plasmas with weak electrostatic fluctuations. The neoclassical and anomalous fluxes are defined based on the ensemble-averaged kinetic equation with the statistically averaged nonlinear term. The anomalous forces derived from that quasilinear term induce the anomalous particle and heat fluxes. The neoclassical banana-plateau particle and heat fluxes and the bootstrap current are also affected by the fluctuations through the parallel anomalous forces and the modified parallel viscosities. The quasilinear term, the anomalous forces, and the anomalous particle and heat fluxes are evaluated from the fluctuating part of the drift kinetic equation. The averaged drift kinetic equation with the quasilinear term is solved for the plateau regime to derive the parallel viscosities modified by the fluctuations. The entropy production rate due to the anomalous transport processes is formulated and used to identify conjugate pairs of the anomalous fluxes and forces, which are connected by the matrix with the Onsager symmetry. (author)

Primary Subject

Source

May 1995; 56 p

Record Type

Report

Report Number

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

Sugama, H.; Horton, W.

National Inst. for Fusion Science, Nagoya (Japan)

National Inst. for Fusion Science, Nagoya (Japan)

AbstractAbstract

[en] Transport processes and resultant entropy production in magnetically confined plasmas are studied in detail for toroidally rotating systems with electrostatic turbulence. A new gyrokinetic equation is derived for rotating plasmas with large flow velocities on the order of the ion thermal speed. Neoclassical and anomalous transport of particles, energy, and toroidal momentum are systematically formulated from the ensemble-averaged kinetic equation with the gyrokinetic equation. As a conjugate pair of the thermodynamic force and the transport flux, the shear of the toroidal flow, which is caused by the radial electric field shear, and the toroidal viscosity enter both the neoclassical and anomalous entropy production. The interaction between the fluctuations and the sheared toroidal flow is self-consistently described by the gyrokinetic equation containing the flow shear as the thermodynamic force and by the toroidal momentum balance equation including the anomalous viscosity. Effects of the toroidal flow shear on the toroidal ion temperature gradient driven modes are investigated. Linear and quasilinear analyses of the modes show that the toroidal flow shear decreases the growth rates and reduces the anomalous toroidal viscosity. (author)

Primary Subject

Source

Aug 1996; 42 p

Record Type

Report

Report Number

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

Jovanovic, D.; Horton, W.

Texas Univ., Austin, TX (United States). Inst. for Fusion Studies. Funding organisation: USDOE, Washington, DC (United States)

Texas Univ., Austin, TX (United States). Inst. for Fusion Studies. Funding organisation: USDOE, Washington, DC (United States)

AbstractAbstract

[en] Linear stability of shear-Alfven vortices is studied analytically using the Lyapunov method. Instability is demonstrated for vortices belonging to the drift mode, which is a generalization of the standard Hasegawa-Mima vortex to the case of large parallel phase velocities. In the case of the convective-cell mode, short perpendicular-wavelength perturbations are stable for a broad class of vortices. Eventually, instability of convective-cell vortices may occur on the perpendicular scale comparable with the vortex size, but it is followed by a simultaneous excitation of coherent structures with better localization than the original vortex

Primary Subject

Source

Aug 1993; 23 p; IFSR--618; CONTRACT FG05-80ET53088; Available from OSTI as DE93040912; NTIS; INIS; US Govt. Printing Office Dep

Record Type

Report

Report Number

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

AbstractAbstract

[en] The properties of the internal transport barriers are developed using theory and radial transport simulations that evolve local turbulent energy density with the temperature profiles. Standard ion temperature gradient models for the nonlinear radial fluxes driven by drift wave turbulence and stabilized by flow shear are implemented in a new high resolution multiple space--time transport code. A dimensionless parameterization of the input power is introduced and shown to characterize the bifurcation to an internal transport barrier. Examples of the interaction and feedback loops of the turbulence with the transport profiles are given for transport barriers as in the Tokamak Fusion Test Reactor [D. J. Grove Nucl. Fusion 25, 1167 (1985)] and the Japan Atomic Energy Research Institute Tokamak-60 Upgrade (JT-60U) [Ninomiya , Phys. Fluids B 4, 2070 (1992)]. For the JT-60U the high performance discharge E 27969, which reached an equivalent Q

_{DT}of unity, is modeled with an appropriate set of turbulent thermal, angular momentum and particle diffusivities. The bifurcation analysis suggests a scaling law for the critical power for the onset of internal transport barriersPrimary Subject

Source

Othernumber: PHPAEN000007000011004534000001; 004011PHP; The American Physical Society

Record Type

Journal Article

Journal

Physics of Plasmas; ISSN 1070-664X; ; v. 7(11); p. 4534-4546

Country of publication

Publication YearPublication Year

Reference NumberReference Number

INIS VolumeINIS Volume

INIS IssueINIS Issue

External URLExternal URL

1 | 2 | 3 | Next |