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Definition of total bootstrap current in tokamaks

Description: Alternative definitions of the total bootstrap current are compared. An analogous comparison is given for the ohmic and auxiliary currents. It is argued that different definitions than those usually employed lead to simpler analyses of tokamak operating scenarios.
Date: June 16, 1995
Creator: Ross, D.W.
Partner: UNT Libraries Government Documents Department

Plasma confinement theory and transport simulation. Final report, October 1, 1988--October 31, 1994

Description: The objectives of the Fusion Research Center Theory Program are: (1) to advance the transport studies of tokamaks, including development and maintenance of the Magnetic Fusion Energy Database, and (2) to provide theoretical interpretation, modeling and equilibrium and stability studies for the TEXT-Upgrade tokamak. Publications and reports and conference presentations for the grant period are listed. Work is described in five basic categories: (A) magnetic fusion energy database; (B) computational support and numerical modeling; (C) support for TEXT-upgrade and diagnostics; (D) transport studies; and (E) Alfven waves.
Date: October 1, 1994
Creator: Ross, D.W.
Partner: UNT Libraries Government Documents Department

Compact tokamak reactors. Part 1 (analytic results)

Description: We discuss the possible use of tokamaks for thermonuclear power plants, in particular tokamaks with low aspect ratio and copper toroidal field coils. Three approaches are presented. First we review and summarize the existing literature. Second, using simple analytic estimates, the size of the smallest tokamak to produce an ignited plasma is derived. This steady state energy balance analysis is then extended to determine the smallest tokamak power plant, by including the power required to drive the toroidal field, and considering two extremes of plasma current drive efficiency. The analytic results will be augmented by a numerical calculation which permits arbitrary plasma current drive efficiency; the results of which will be presented in Part II. Third, a scaling from any given reference reactor design to a copper toroidal field coil device is discussed. Throughout the paper the importance of various restrictions is emphasized, in particular plasma current drive efficiency, plasma confinement, plasma safety factor, plasma elongation, plasma beta, neutron wall loading, blanket availability and recirculating electric power. We conclude that the latest published reactor studies, which show little advantage in using low aspect ratio unless remarkably high efficiency plasma current drive and low safety factor are combined, can be reproduced with the analytic model.
Date: September 13, 1996
Creator: Wootton, A. J.; Wiley, J. C.; Edmonds, P. H. & Ross, D. W.
Partner: UNT Libraries Government Documents Department

Compact tokamak reactors part 2 (numerical results)

Description: The authors describe a numerical optimization scheme for fusion reactors. The particular application described is to find the smallest copper coil spherical tokamak, although the numerical scheme is sufficiently general to allow many other problems to be solved. The solution to the steady state energy balance is found by first selecting the fixed variables. The range of all remaining variables is then selected, except for the temperature. Within the specified ranges, the temperature which satisfies the power balance is then found. Tests are applied to determine that remaining constraints are satisfied, and the acceptable results then stored. Results are presented for a range of auxiliary current drive efficiencies and different scaling relationships; for the range of variables chosen the machine encompassing volume increases or remains approximately unchanged as the aspect ratio is reduced.
Date: October 21, 1996
Creator: Wiley, J.C.; Wootton, A.J. & Ross, D.W.
Partner: UNT Libraries Government Documents Department

MDI: Mathematica database interface for the MFEDB

Description: We describe a new interface for the Magnetic Fusion Energy Database, MFEDB, which uses Mathematica{reg sign} as a front end. MDI is a Mathematica package that defines a basic set of MFEDB access functions. The package will also accept standard SQL queries. Each function returns Mathematica-style lists, which can then be manipulated with any of the Mathematica functions. MDI also provides some utility functions for plotting and analyzing the data. The MDI package essentially makes the MFEDB an extension of Mathematica. The user may use any of the many Mathematica front-ends including telnet, X-Windows, or a notebook. The mdi.m package may be obtained by anonymous FTP from the MFEDB site or by use of netmfe, and E-mail database interface. MDI is a example of distributed computing. Behind the user interface, MDI calls an RPC client program that communicates with an RPC server on the MFEDB computer. It relies on the network communication capabilities of Mathematica to connect the user to a workstation running the Mathematica kernel. The Mathematica kernel is then connected to the MFEDB host workstation by a client/server pair of RPC processes. If the Mathematica kernel is to be run on the users' machine, the RPC client program must also be obtained and installed. The MDI RPC server is also available for users who would like to provide their own client software. The server returns ASCII tables from standards queries and may be accessed and processed by any program on the internet that has access to RPC services.
Date: April 1, 1992
Creator: Wiley, J.C.; Miner, W.H. Jr. & Ross, D.W.
Partner: UNT Libraries Government Documents Department

The Physics of Confinement Improvement with Impurity Seeding in DIII-D

Description: Clear increases in confinement (from H{sub 89P} {approx} 1 to H{sub 89P} {<=} 2) and simultaneous reductions of long-wavelength turbulence have been observed in L-mode discharges in DIII-D, which are directly correlated with external impurity injection [1]. These observations provide an opportunity to understand the mechanism for confinement improvement with impurity seeding observed in a number of tokamaks [2], and to make quantitative tests of theory-based turbulence and transport models with experimental measurements. Impurity seeding can be used not only to produce a radiative mantle to reduce heat fluxes to the first wall material [3], but also as a tool to control profiles in Advanced Tokamak (AT) plasmas. Significant confinement improvements are observed with injection of noble gases (Ne, Ar, and Kr) into L-mode edge, negative central shear (sawtooth-free) discharges in DIII-D. Compared to similar reference discharges without impurity injection, confinement enhancement factor and neutron emission in neon-injected discharges are nearly doubled [Fig. 1(a,b)]. The ion and electron temperature with neon injection exhibit increased central values and profile broadening while the electron density profile becomes more peaked.
Date: August 1, 2000
Creator: Murakami, M.; McKee, G.R.; Jackson, G.L.; Staebler, G.M.; Baker, D.R.; Boedo, J.A. et al.
Partner: UNT Libraries Government Documents Department