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Author Barnes, C. W. ♦ Fernandez, J. C. ♦ Henins, I. ♦ Hoida, H. W. ♦ Jarboe, T. R. ♦ Knox, S. O. ♦ Marklin, G. J. ♦ McKenna, K. F.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword PLASMA PHYSICS AND FUSION TECHNOLOGY ♦ PLASMA ♦ EQUILIBRIUM ♦ MAGNETIC FLUX ♦ SPHEROMAK DEVICES ♦ PLASMA DIAGNOSTICS ♦ BOUNDARY LAYERS ♦ CONSERVATION LAWS ♦ DIFFUSION ♦ ELECTRIC CONDUCTIVITY ♦ ELECTRODES ♦ ELECTROSTATICS ♦ ENERGY LOSSES ♦ HELICITY ♦ MAGNETIZATION ♦ PLASMA EXPANSION ♦ RELAXATION ♦ CLOSED PLASMA DEVICES ♦ ELECTRICAL PROPERTIES ♦ EXPANSION ♦ LAYERS ♦ LOSSES ♦ PARTICLE PROPERTIES ♦ PHYSICAL PROPERTIES ♦ THERMONUCLEAR DEVICES ♦ TOKAMAK DEVICES ♦ Fusion Energy- Plasma Research- Confinement, Heating, & Production
Abstract The conjecture that magnetic helicity (linked flux) is conserved in magnetized plasmas for time scales that are short compared to the resistive diffusion time is experimentally tested in the CTX spheromak (Phys. Rev. Lett. 45, 1264 (1980); 51, 39 (1983); Nucl. Fusion 24, 267 (1984)). Helicity is created electrostatically by current drawn from electrodes. The magnetized plasma then flows into a conducting flux conserver where the energy per helicity of the plasma is minimized and a spheromak is formed on a relaxation time scale of many Alfven times. The magnetic field strength of the equilibrium is subsequently increased and sustained. The amount of helicity created by the magnetized coaxial plasma source, the helicity content of the spheromak equilibrium, and the resistive loss of the helicity are measured to determine the balance of helicity between source and spheromak with a +- 16% uncertainty. In CTX the amount of energy that must be rapidly dissipated within the conducting boundary while conserving helicity in the process of sustaining the spheromak is experimentally controllable, and has varied from 1.8 times the spheromak magnetic energy to greater than 10 times. The relaxation, or minimization of the energy-to-helicity ratio, determines the gross structure (the normalized spatial profile) of the spheromak, while the conservation of helicity itself determines the magnitude and time dependence of the magnetic fields of the spheromak equilibrium. Helicity balance tests are done by individually varying the sign and magnitude of the source voltage and flux, and by observing sustainment of spheromaks with fields opposing those of the source. A threshold for helicity injection from the source is measured and related to the source and entrance region size. During times short compared to resistive
Educational Use Research
Learning Resource Type Article
Publisher Date 1986-10-01
Publisher Department Los Alamos National Laboratory, Los Alamos, New Mexico 87545
Publisher Place United States
Journal Phys. Fluids
Volume Number 29
Issue Number 10
Organization Los Alamos National Laboratory, Los Alamos, New Mexico 87545


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