Simple and accurate method of diamagnetic flux measurement in Versatile Experimental Spherical Torus (VEST)

Diamagnetic flux is measured accurately in the Versatile Experiment Spherical Torus by simply measuring the change in the toroidal field (TF) coil current without additional poloidal loops. Stray couplings mainly with the plasma current (since poloidal field coils are aligned well to the TF coils) a...

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Bibliographic Details
Published in:Review of scientific instruments 2018-10, Vol.89 (10), p.103508-103508
Main Authors: Yang, J., Kim, Y., Jeong, W. I., Hwang, Y. S.
Format: Article
Language:English
Subjects:
Coiling
Coils
Couplings
Diamagnetism
Energy measurement
Field coils
Flux
Internal energy
Low aspect ratio
Plasma currents
Scientific apparatus & instruments
Sensitivity
Toruses
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Summary:Diamagnetic flux is measured accurately in the Versatile Experiment Spherical Torus by simply measuring the change in the toroidal field (TF) coil current without additional poloidal loops. Stray couplings mainly with the plasma current (since poloidal field coils are aligned well to the TF coils) are compensated for, resulting in the minimum measurable flux of ±0.2 mWb determined mainly by the finite sensitivity of the TF coil current sensor, implying that the accuracy of this simple method can be improved by measuring the TF coil current change with a higher sensitivity. The poloidal beta is derived from the measured diamagnetic flux with the consideration of the low aspect ratio geometry. The poloidal beta and the plasma stored energy derived from the measurement are in good agreement with those from the equilibrium reconstruction, and the energy confinement time derived from the measurement is consistent with the L mode scaling.
ISSN:0034-6748
1089-7623
DOI:10.1063/1.5041517