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

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Murakami density limit in tokamaks and reversed-field pinches

A theoretical upper limit for the density in an ohmically heated tokamak discharge follows from the requirement that the ohmic heating power deposited in the central current-carrying channel exceed the impurity radiative cooling in this critical region. A compact summary of our results gives this limit n/sub M/ for the central density as n/sub M/ = (Z/sub e//(Z/sub e/-1)/sup 1/2/n/sub eo/ (B/sub T//1T)(1m/R) where n/sub eo/ depends strongly on the impurity species and is remarkably independent … more

Date: March 1, 1984

Creator: Perkins, F.W. & Hulse, R.A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Hot-electron-ring physics

Separate abstracts were prepared for each of the 16 included papers. (MOW)

Date: June 1, 1982

Creator: Uckan, N.A. (ed.)

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Dynamic modeling of transport and positional control of tokamaks

We describe here a numerical model of a free boundary axisymmetric tokamak plasma and its associated control systems. The plasma is modeled with a hybrid method using two-dimensional velocity and flux functions with surface-averaged MHD equations describing the evolution of the adiabatic invariants. Equations are solved for the external circuits and for the effects of eddy currents in nearby conductors. The method is verified by application to several test problems and used to simulate the form… more

Date: October 1, 1985

Creator: Jardin, S. C.; Pomphrey, N. & DeLucia, J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Ion transport in stellarators

Stellarator ion transport in the low-collisionality regime with a radial electric field is calculated by a systematic expansion of the drift-Boltzmann equation. The shape of the helical well is taken into account in this calculation. It is found that the barely trapped ions with three to four times the thermal energy give the dominant contribution to the diffusion. Expressions for the ion particle and energy fluxes are derived.

Date: September 1, 1985

Creator: Ho, D.D.M. & Kulsrud, R.M.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Analysis of x-ray production in TMX upgrade

TMX Upgrade (TMX-U), a tandem mirror experiment at LLNL, will use high power microwaves for electron cyclotron resonant heating (ECRH). As demonstrated on Elmo Bumpy Torus (EBT) and related experiments which use similar heating techniques, high energy electron populations are created. In these devices, which run CW, significant x-ray production occurs and adequate shielding must be provided for personnel protection. TMX-U is a pulsed experiment; however, significant x-ray production is expected… more

Date: February 4, 1982

Creator: Stallard, B. & Stephens, L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Bounce-averaged Fokker-Planck code for stellarator transport

A computer code for solving the bounce-averaged Fokker-Planck equation appropriate to stellarator transport has been developed, and its first applications made. The code is much faster than the bounce-averaged Monte-Carlo codes, which up to now have provided the most efficient numerical means for studying stellarator transport. Moreover, because the connection to analytic kinetic theory of the Fokker-Planck approach is more direct than for the Monte-Carlo approach, a comparison of theory and nu… more

Date: July 1, 1985

Creator: Mynick, H.E. & Hitchon, W.N.G.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Behavior of a plasma in a high-density gas-embedded Z-pinch configuration

The theoretical analysis of a high density Z-pinch (HDZP) begins with an examination of the steady state energy balance between ohmic heating and bremsstrahlung radiation losses for a plasma column in pressure equilibrium. The model is then expanded to include the time-varying internal energy and results in a quasi-equilibrium prescription for the load current through a constant radius plasma channel. This set of current waveforms is useful in the design of experimental systems. The behavior of… more

Date: May 1, 1982

Creator: Shlachter, J.S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Drift Hamiltonian in magnetic coordinates

A Hamiltonian formulation of the guiding-center drift in arbitrary, steady state, magnetic and electric fields is given. The canonical variables of this formulation are simply related to the magnetic coordinates. The modifications required to treat ergodic magnetic fields using magnetic coordinates are explicitly given in the Hamiltonian formulation.

Date: February 1, 1982

Creator: White, R. B.; Boozer, A. H. & Hay, R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Hamiltonian guiding center drift orbit calculation for toroidal plasmas of arbitrary cross section

A Hamiltonian guiding center drift orbit formalism is developed which permits the efficient calculation of particle trajectories in toroidal devices of arbitrary cross section with arbitrary plasma ..beta... The magnetic field is assumed to be a small perturbation from a zero order toroidal equilibrium field possessing either axial or helical symmetry. The equilibrium field can be modelled analytically or obtained numerically from equilibrium codes. A numerical code based on the formalism is us… more

Date: February 1, 1984

Creator: White, R. B. & Chance, M. S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Computational-physics program of the National MFE Computer Center

The computational physics group is ivolved in several areas of fusion research. One main area is the application of multidimensional Fokker-Planck, transport and combined Fokker-Planck/transport codes to both toroidal and mirror devices. Another major area is the investigation of linear and nonlinear resistive magnetohydrodynamics in two and three dimensions, with applications to all types of fusion devices. The MHD work is often coupled with the task of numerically generating equilibria which … more

Date: February 1, 1982

Creator: Mirin, A. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Computer simulations of anomalous transport

Numerical plasma simulations have been carried out to study: (1) the turbulent spectrum and anomalous plasma transport associated with a steady state electrostatic drift turbulence; and (2) the anomalous energy transport of electrons due to shear-Alfven waves in a finite-..beta.. plasma. For the simulation of the steady state drift turbulence, it is observed that, in the absence of magnetic shear, the turbulence is quenched to a low level when the rotational transform is a rational number, whil… more

Date: July 1, 1980

Creator: Lee, W. W. & Okuda, H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Large aspect ratio tokamak study

The Large Aspect Ratio Tokamak Study (LARTS) investigated the potential for producing a viable long burn tokamak reactor through enhanced volt-second capability of the ohmic heating transformer by employing high aspect ratio designs. The plasma physics, engineering, and economic implications of high aspect ratio tokamaks were accessed in the context of extended burn operation. Plasma startup and burn parameters were addressed using a one-dimensional transport code. The pulsed electrical power r… more

Date: January 1, 1979

Creator: Reid, R. L.; Holmes, J. A.; Houlberg, W. A.; Peng, Y. K. M.; Strickler, D. J.; Brown, T. G. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Influence of stochastic magnetic fields on the confinement of runaway electrons and thermal electron energy in tokamaks

The ratio of the runaway electron confinement to thermal electron energy confinement is derived for tokamaks where both processes are determined by free streaming along stochastic magnetic field lines. The runaway electron confinement is enhanced at high runaway electron energies due to phase averaging over the magnetic perturbations when the runaway electron drift surfaces are dislaced from the magnetic surfaces. Comparison with experimental data from LT-3, ORMAK, PLT, ST, and TM-3 indicates t… more

Date: July 1, 1980

Creator: Mynick, H.E. & Strachan, J.D.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Empirical particle transport model for tokamaks

A simple empirical particle transport model has been constructed with the purpose of gaining insight into the L- to H-mode transition in tokamaks. The aim was to construct the simplest possible model which would reproduce the measured density profiles in the L-regime, and also produce a qualitatively correct transition to the H-regime without having to assume a completely different transport mode for the bulk of the plasma. Rather than using completely ad hoc constructions for the particle diff… more

Date: August 1, 1986

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

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Two-point model for divertor transport

Plasma transport along divertor field lines was investigated using a two-point model. This treatment requires considerably less effort to find solutions to the transport equations than previously used one-dimensional (1-D) models and is useful for studying general trends. It also can be a valuable tool for benchmarking more sophisticated models. The model was used to investigate the possibility of operating in the so-called high density, low temperature regime.

Date: April 1, 1984

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

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Leakage of runaway electrons from tokamaks

Runaway electron orbits are calculated in a tokamak magnetic field. It is shown that these electrons tend to drift towards a larger major radius with a velocity v Vector/sub R/ = qcE/B/sub 0/ R. This effect may be relevant to some recent experimental observations in tokamaks.

Date: February 1, 1982

Creator: Wong, K. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Preliminary semiempirical transport models

A class of semiempirical transport models is proposed for testing against confinement data from tokamaks and for use in operations planning and machine design. A reference model is proposed to be compatible with published confinement data. Theoretical considerations are used to express the anomalous transport coefficients in terms of appropriate dimensionless parameters.

Date: November 1, 1983

Creator: Singer, C.E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Creating an anisotropic plasma resistivity with waves

An anisotropic plasma resistivity may be created by preferential heating of electrons traveling in one direction. This can result in a steady-state toroidal current in a tokamak even in the absence of net wave momentum. In fact, at high wave phase velocities, the current associated with the change in resistivity is greater than that associated with net momentum input. An immediate implication is that other waves, such as electron cyclotron waves, may be competitive with lower-hybrid waves as a … more

Date: May 1, 1980

Creator: Fisch, N. J. & Boozer, A. H.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Three-dimensional free boundary calculations using a spectral Green's function method

The plasma energy W/sub p/ = integral ..cap omega../sub p/(1/2B/sup 2/ + p)dV is minimized over a toroidal domain ..cap omega../sub p/ using an inverse representation for the cylindrical coordinates R = ..sigma..R/sub mn/(s)cos(mtheta - n zeta) and Z = ..sigma..Z/sub mn/(s)sin(mtheta - n zeta), where (s,theta,zeta) are radial, poloidal, and toroidal flux coordinates, respectively. The radial resolution of the MHD equations is significantly improved by separating R and Z into contributions from … more

Date: January 1, 1986

Creator: Hirshman, S.P.; van Rij, W.I. & Merkel, P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Hydrogen recycle modeling in transport codes

The hydrogen recycling models now used in Tokamak transport codes are reviewed and the method by which realistic recycling models are being added is discussed. Present models use arbitrary recycle coefficients and therefore do not model the actual recycling processes at the wall. A model for the hydrogen concentration in the wall serves two purposes: (1) it allows a better understanding of the density behavior in present gas puff, pellet, and neutral beam heating experiments; and (2) it allows … more

Date: January 1, 1979

Creator: Howe, H.C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Numerical model for radial transport in the ELMO Bumpy Torus

Neutral and charged particle densities and temperatures are calculated as functions of radius for the toroidal plasma in the ELMO Bumpy Torus (EBT) experiment. Energy dependent ionization and charge-exchange rates, ambipolar diffusion, and self-consistent radial electric field profiles are included. Variation in magnetic field due to finite plasma pressure, effects of energetic electron rings, and transport due to drift waves and magnetic field errors are neglected. Diffusion is assumed to be n… more

Date: November 1, 1977

Creator: Jaeger, E. F. & Hedrick, C. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Enhanced transport in tokamaks due to toroidal ripple

A method for evaluating transport in non-symmetric systems is developed and applied to a previously unstudied ripple collisionality regime of tokamaks. This collisionality regime, the ripple plateau, is the regime of primary importance both for present day and reactor scale tokamaks. The results can be directly applied to related systems like the toroidal Z pinch.

Date: January 1, 1980

Creator: Boozer, A. H.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Transport analysis of a small stellarator

A Monte Carlo method of evaluating typical particle and energy transport coefficients is given for the case in which the particle drift orbits are a significant fraction of the plasma radius. The method is applied to a preliminary design for a helical axis (heliac) stellarator experiment.

Date: September 1, 1983

Creator: Kuo-Petravic, G. & Boozer, A. H.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Basic principle of constant q/sub a/ current build-up in tokamaks

An analytic expression is derived such that the current profile shape is kept constant during the current build-up phase in tokamaks. The required conductivity profile is parametrized by two externally controllable parameters, I/sub p/ and a/sub p/ in the case of the Gaussian current profile. It is shown that a Gaussian current profile can be maintained for a realistically broad conductivity profile by using the constant q/sub a/ current build-up method even under the condition of a high I/sub … more

Date: May 1, 1985

Creator: Kikuchi, M.

Item Type: Report

Partner: UNT Libraries Government Documents Department