Abstract
This paper reports an experimental observation of spontaneous transition of the core radial electric field to a large positive value (Er ∼ 5 kV m-1), with a strong electric-field shear (∼700 kV m -2) in a low temperature (Te ∼ 10 eV) radio frequency generated argon plasma in the H-1NF heliac stellarator. The transition, which seems to be driven by a spontaneous excitation of m = 2 magnetic islands near the core, is associated with a localized increase in the plasma density and excitation of coherent low frequency (∼3 kHz) oscillations possibly due to unstable Er shear driven modes. Evidence suggests development of the core electron-root scenario, which previously has been observed only at high temperature electron cyclotron heated plasmas.
Original language | English |
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Article number | 083003 |
Journal | Nuclear Fusion |
Volume | 51 |
Issue number | 8 |
DOIs | |
State | Published - Aug 2011 |