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in subjects: "Thermonuclear Devices 700105* -- Fusion Energy-- Plasma Research-- Plasma Kinetics-Theoretical-- -1987"

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Guiding-center Hamiltonian for large gyroexcursion particles in mirror configurations

An explicit expression is derived for the guiding-center Hamiltonian K, valid for particles having gyroexcursion rho comparable to the system size, such as the high-energy ring particles in the Berta experiment at Cornell. The form of K is quite simple. It depends on the magnetic field strength B and its radial derivatives, evaluated at an average radius of the particle from the symmetry axis, and allows for a slow but otherwise arbitrary variation of B along the axis. The adiabatic invariant o… more

Date: October 1, 1979

Creator: Mynick, H.E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Influence of anomalous thermal losses of ignition conditions

In the process of achieving ignition conditions, it is likely that microinstabilities, which lead to anomalous thermal transport of the fusing nuclei, will be present. When such phenomena are taken into account, an appropriate formulation of ignition criteria becomes necessary. In particular, a new type of plasma density limit is identified.

Date: May 1, 1986

Creator: Coppi, B. & Tang, W.M.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Plasma transport near material boundaries

The fluid theory of two-dimensional (2-d) plasma transport in axisymmetric devices is reviewed. The forces which produce flow across the magnetic field in a collisional plasma are described. These flows may lead to up-down asymmetries in the poloidal rotation and radial fluxes. Emphasis is placed on understanding the conditions under which the known 2-d plasma fluid equations provide a valid description of these processes. Attempts to extend the fluid treatment to less collisional, turbulent pl… more

Date: June 1, 1985

Creator: Singer, C.E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Two-dimensional finite element multigroup diffusion theory for neutral atom transport in plasmas

Solution of the energy dependent diffusion equation in two dimensions is formulated by multigroup approximation of the energy variable and general triangular mesh, finite element discretization of the spatial domain. Finite element formulation is done by Galerkin's method. Based on this formulation, a two-dimensional multigroup finite element diffusion theory code, FENAT, has been developed for the transport of neutral atoms in fusion plasmas. FENAT solves the multigroup diffusion equation in X… more

Date: February 1, 1986

Creator: Hasan, M.Z. & Conn, R.W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Stochastic motion of particles in mirror machines

Several applications of stochasticity theory to particle motion in quiescent mirror machines are discussed. We briefly review the problem of magnetic moment jumps in a conventional mirror machine, and point out the role of stochasticity in extending the mirror loss cone. We consider magnetic moment jumps in a flat-bottomed magnetic well, such as the solenoid of a tandem mirror machine, and find that, for suitable choices of field parameters, the magnetic moment change per bounce passes through … more

Date: June 15, 1979

Creator: Cohen, Ronald H.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Features of spherical torus plasmas

The spherical torus is a very small aspect ratio (A < 2) confinement concept obtained by retaining only the indispensable components inboard to the plasma torus. MHD equilibrium calculations show that spherical torus plasmas with safety factor q > 2 are characterized by high toroidal beta (..beta../sub t/ > 0.2), low poloidal beta (..beta../sub p/ < 0.3), naturally large elongation (kappa greater than or equal to 2), large plasma current with I/sub p//(aB/sub t0/) up to about 7 MA/mT, strong pa… more

Date: December 1, 1985

Creator: Peng, Y. K. M. & Strickler, D. J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Theoretical studies in tandem mirror physics

Recent developments in six areas of tandem-mirror theory are explored. Specifically, FLR terms (including electric-field drift) have been added to our 3-D paraxial MHD equilibrium code. Our low-frequency MHD stability analysis with FLR, which previously included only m/sub theta/ = 1 rigid perturbations, has been extended to incorporate moderate m/sub theta/, rotational drive, finite-beta effects on wall stabilization, and the well-digging effect of energetic electrons by using three computatio… more

Date: July 17, 1984

Creator: Cohen, R. H.; Auerbach, S. P.; Baldwin, D. E.; Byers, J. A.; Chen, Y. J.; Cohen, B. I. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

High energy runaway orbits in the presence of m = 2 magnetic islands

A guiding center computer code is used to map out trajectories of collisionless runaway electrons in the presence of m = 2 magnetic islands in a tokamak. Low energy runaway drift surfaces follow closely the perturbed poloidal magnetic flux surfaces, as expected. Higher energy runaway orbits are seen to retain an m = 2 structure even though the drift surfaces are shifted considerably outward from the magnetic flux surfaces. The size of the island structure in the drift surfaces decreases as the … more

Date: July 1, 1978

Creator: Zweben, S. J.; Waddell, B. V.; Swain, D. W. & Fleischman, H. H.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Time Evolution of Mass Flows in a Collisional Tokamak

The time evolution, due to dissipative processes, of an initial pattern of poloidal and toroidal mass flows in a tokamak is considered. The calculation is applicable to a collisional, low ..beta.., axisymmetric tokamak of arbitrary minor cross section. Time rates of change of poloidal flows which are subsonic but larger than the diamagnetic speed are given according to the magnitude of the flow and the collisionality of the plasma. Over most of parameter space for typical tokamaks, the poloidal… more

Date: April 1, 1978

Creator: Hassam, A. B. & Kulsrud, R. M.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Kinetic transport properties of a bumpy torus with finite radial ambipolar field

Bumpy torus neoclassical transport coefficients have been calculted including finite values of the radial ambipolar field. These are obtained by solving a bounce-averaged drift kinetic equation in a local approximation for perturbations in the distribution function (away from a stationary Maxwellian) caused by toroidicity and radial gradients in plasma density, temperature, and potential. Particle and energy fluxes along with the associated transport coefficients are then calculated by taking a… more

Date: April 1, 1978

Creator: Spong, D. A.; Harris, E. G. & Hedrick, C. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Fokker--Planck/transport analyses of fusion plasmas in contemporary beam-driven tokamaks

The properties of deuterium plasmas in experimental tokamaks heated and fueled by intense neutral-beam injection are evaluated with a Fokker-Planck/radial transport code coupled with a Monte Carlo neutrals treatment. Illustrative results are presented for the Poloidal Divertor Experiment at PPPL as a function of beam power and plasma recycling coefficient, R/sub c/. When P/sub beam/ = 8 MW at E/sub b/ = 60 keV, and R/sub c/ = 0.2, then <n/sub hot//n/sub e/> approximately 0.5, (/sup 2///sub 3/ <… more

Date: April 1, 1978

Creator: Mirin, A. A.; McCoy, M. G.; Killeen, J.; Rensink, M. E.; Shumaker, D. E.; Jassby, D. L. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Use of the stellarator expansion to investigate plasma equilibrium in modular stellarators

A numerical code utilizing a large-aspect ratio, small-helical-distortion expansion is developed and used to investigate the effect of plasma currents on stellarator equilibrium. Application to modular stellarator configurations shows that a large rotational transform, and hence large coil deformation, is needed to achieve high-beta equilibria.

Date: November 1, 1982

Creator: Anania, G.; Johnson, J. L. & Weimer, K. E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

ILUCG algorithm which minimizes in the Euclidean norm

An algroithm is presented which solves sparse systems of linear equations of the form Ax = Y, where A is non-symmetric, by the Incomplete LU Decomposition-Conjugate Gradient (ILUCG) method. The algorithm minimizes the error in the Euclidean norm vertical bar x/sub i/ - x vertical bar/sub 2/, where x/sub i/ is the solution vector after the i/sup th/ iteration and x the exact solution vector. The results of a test on one real problem indicate that the algorithm is likely to be competitive with th… more

Date: July 1, 1978

Creator: Petravic, M. & Kuo-Petravic, G.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Numerical determination of axisymmetric toroidal magnetohydrodynamic equilibria

Numerical schemes for the determination of stationary axisymmetric toroidal equilibria appropriate for modeling real experimental devices are given. Iterative schemes are used to solve the elliptic nonlinear partial differential equation for the poloidal flux function psi. The principal emphasis is on solving the free boundary (plasma-vacuum interface) equilibrium problem where external current-carrying toroidal coils support the plasma column, but fixed boundary (e.g., conducting shell) cases … more

Date: July 1, 1978

Creator: Johnson, J. L.; Dalhed, H. E. & Greene, J. M.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Topology of tokamak orbits

The topology of all contained tokamak guiding center orbits is displayed in a three-dimensional constants-of-motion space. The treatment is perfectly general and holds for arbitrary axisymmetric MHD equilibria. We show that significant topological changes occur in the high-anti BETA (approximately > 6%) cases which are associated with a region of absolute minimum B in the plasma.

Date: January 1, 1978

Creator: Rome, J. A. & Peng, Y. K. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

One and one-half dimensional model of the EBT reactor

A one-dimensional, time-dependent model is described for plasma particle and energy transport and alpha particle transport coupled with magnetic field evolution in a geometry appropriate to EBT. The transport equations used are derived from exact moments of the Boltzmann equation, and the magnetic field is calculated from Faraday's and Ampere's laws. The set of transport equations is closed by incorporating into them transport coefficiencents derived from the appropriate kinetic equation. Also … more

Date: October 22, 1979

Creator: Klein, H. H. & Bathke, C. G.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Coupled transport and heating in EBT and EBS

In ELMO Bumpy Torus (EBT) and EBT-like devices, hot electron rings form at the edge of the warm core plasma. As early as 1975 it was recognized that microwave heating, which plays such a significant role in electron dynamics, should be incorporated into transport models. Recent theoretical microwave heating and transport studies suggest that this is critical for explaining EBT experiments. In particular, descriptions of the electron distribution as a sum of only two distributions (i.e., one for… more

Date: January 1, 1984

Creator: Hedrick, C. L.; Batchelor, D. B.; Chen, G. L.; Goldfinger, R. C.; Hastings, D. E.; Jaeger, E. F. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

User's guide for SLWDN9, a code for calculating flux-surfaced-averaging of alpha densities, currents, and heating in non-circular tokamaks

The code calculates flux-surfaced-averaged values of alpha density, current, and electron/ion heating profiles in realistic, non-circular tokamak plasmas. The code is written in FORTRAN and execute on the CRAY-1 machine at the Magnetic Fusion Energy Computer Center.

Date: March 1, 1980

Creator: Hively, L.M. & Miley, G.M.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Boundary layer studies related to fusion theory. Final report

The described work studied the boundary between closed and open field lines in EBT geometry, with emphasis on the microstability properties. These properties were established primarily for drift waves in the lower hybrid range of frequencies. The transport due to these modes was evaluated by a self-consistent treatment, using quasilinear models in a plasma diffusion code. The model was benchmarked against the EDT experimental results from ORNL and the sensitivity to transport model established.… more

Date: September 29, 1981

Item Type: Report

Partner: UNT Libraries Government Documents Department

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MFTF-B performance calculations

In this report we document the operating scenario models and calculations as they exist and comment on those aspects of the models where performance is sensitive to the assumptions that are made. We also focus on areas where improvements need to be made in the mathematical descriptions of phenomena, work which is in progress. To illustrate the process of calculating performance, and to be very specific in our documentation, part 2 of this report contains the complete equations and sequence of c… more

Date: December 6, 1982

Creator: Thomassen, K.I. & Jong, R.A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Two-dimensional transport of tokamak plasmas. [Neoclassical transport theory]

A reduced set of two-fluid transport equations is obtained from the conservation equations describing the time evolution of the differential particle number, entropy, and magnetic fluxes in an axisymmetric toroidal plasma with nested magnetic surfaces. Expanding in the small ratio of perpendicular to parallel mobilities and thermal conductivities yields as solubility constraints one-dimensional equations for the surface-averaged thermodynamic variables and magnetic fluxes. Since Ohm's law E + U… more

Date: October 1, 1978

Creator: Hirshman, S. P. & Jardin, S. C.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Tensor pressure tokamak equilibrium and stability

We investigate the equilibrium and magnetohydrodynamic (MHD) stability of tokamaks with tensor pressure and examine, in particular, the effects of anisotropies induced by neutral beam injection. Perpendicular and parallel beam pressure components are evaluated by taking moments of a distribution function obtained from the solution of a Fokker-Planck equation that models the injection of high-energy neutral beams into a tokamak. We numerically generate D-shaped beam-induced tensor pressure equil… more

Date: March 1, 1981

Creator: Cooper, W. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Physics issues in mirror and tandem mirror systems

Over the years the study of the confinement of high temperature plasma in magnetic mirror systems has presented researchers with many unusual physics problems. Many of these issues are by now understood theoretically and documented experimentally. With the advent of the tandem mirror idea, some new issues have emerged and are now under intensive study. These include: (1) the generation and control of ambipolar confining potentials and their effect on axial confinement and, (2) the combined infl… more

Date: June 15, 1984

Creator: Post, Richard F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Barrier-potential model

A useful model for calculating the variation in the electron density, ion density, and ambipolar potential along magnetic field lines in the thermal barrier cell of a tandem mirror is presented.

Date: August 4, 1981

Creator: Pearlstein, L. D. & Nevins, W. M.

Item Type: Report

Partner: UNT Libraries Government Documents Department