Scaling of density fluctuations in PDX

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Abstract
The scaling of turbulent density fluctuations with drift-wave characteristics has been examined in the PDX tokamak using scattering of 2 mm microwaves. The authors have measured how the frequency spectra, the k⊥ spectra and the magnitude of the fluctuations vary with toroidal field, neutral beam heating power, plasma current, position and confinement regime in PDX. Since turbulence is a possible cause of anomalous heat loss in PDX and other tokamaks, the scaling of the turbulence is compared with energy confinement scalings. In many cases, an increased fluctuation level is correlated with decreased energy confinement. In one case, the fluctuation level does not change as the confinement properties of the plasma change. The scaling of the experimental fluctuation levels is compared with various drift-wave parameters. It is found that the fluctuation level scales as the mixing-length limit, ñ/n ~ l/k⊥Ln, in some sets of data, but not in other sets.
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