Control of toroidal-like asymmetries in a heliac

Journal Article · Sat May 01 04:00:00 EDT 1993 · Physics of Fluids B; (United States)

DOI:https://doi.org/10.1063/1.860896· OSTI ID:5564245

Spanjers, G G; Nelson, B A; Ribe, F L; Jarboe, T R ^[1]; Barnes, D C ^[2]

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1. 120 AERL FL-10, University of Washington, Seattle, Washington 98195 (United States)
2. Science Applications International Corporation, San Diego, California 92121 (United States)

A simple modification to the heliac coil configuration [A. H. Boozer [ital et] [ital al]., [ital Plasma] [ital Physics] [ital and] [ital Controlled] [ital Nuclear] [ital Fusion] (International Atomic Energy Agency, Vienna, 1966), Vol. 1, p. 103] is described that reduces the toroidal perturbation to the magnetic field structure and significantly restores the helical symmetry. This is accomplished by shifting the internal current-carrying conductor (hardcore) of the heliac radially inward from its normal position at the geometric center of the external [ital l]=1 coils. It is shown by computations that a large-aspect-ratio toroidal heliac is similar to a helically symmetric linear heliac in which the hardcore has been shifted. This similarity is seen in the analytic form of the magnetic potential, the flux surface shape, and in the harmonic spectra of the field lines. It is then shown that the toroidicity perturbations can be reduced in a toroidal heliac by combining these effects---using a radially inward hardcore shift in the toroidal configuration. In the experiments reported here the toroidal-like effects are created in the linear High Beta Q Machine (HBQM) heliac [C. M. Greenfield [ital et] [ital al]., Phys. Fluids B [bold 2], 133 (1990)] by shifting the hardcore off the geometric center of the [ital l]=1 coils. The induced toroidal-like effects are seen from an asymmetry in the axial excluded flux; however, no decrease in global beta is seen as compared to the unshifted symmetric case (G. G. Spanjers, Ph.D. dissertation, University of Washington, 1992) indicating the absence of large-scale magnetohydrodynamic instabilities at high beta.

• OSTI ID: 5564245
• Journal Information: Physics of Fluids B; (United States), Journal Name: Physics of Fluids B; (United States) Vol. 5:5; ISSN PFBPEI; ISSN 0899-8221
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700310 -- Plasma Confinement-- (1992-)
700412* -- Magnetic Confinement Devices-- (1992-)
ANNULAR SPACE
ASPECT RATIO
ASYMMETRY
CLOSED CONFIGURATIONS
CLOSED PLASMA DEVICES
CONFIGURATION
HELIAC STELLARATORS
MAGNETIC FIELD CONFIGURATIONS
MAGNETIC FLUX
OPEN PLASMA DEVICES
Q DEVICES
SPACE
STELLARATORS
THERMONUCLEAR DEVICES
TOROIDAL CONFIGURATION