Abstract
The role of self-generated zonal flows (ZF) in transport regulation in magnetic confinement devices via its shear is a potent concept and a physics issue. However, as the experimental evidence of its existence in tokamaks is meagre, a basic physics experimental study of ZF associated with ion temperature gradient (ITG) drift modes has been performed in the Columbia Linear Machine. The difficult problem of detection of ZF has been solved via a novel diagnostic using the paradigm of frequency modulation (FM) in radio transmission. Using this and discrete short time Fourier transform, we find a power spectrum peak at ITG (‘carrier’) frequency of ∼120 kHz and FM sidebands at frequency of ∼2 kHz, which is identified as a ZF. It has all the signatures of a ZF: a potential at near zero frequency and poloidal symmetry (m = 0), toroidal symmetry (k‖ = 0) and radial variations only. The results roughly agree with theoretical estimates given here.
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