Abstract
The scaling of magnetic fluctuations with the Lundquist number (S) isstudied in the RFX reversed field pinch (RFP) device for different operationalregimes. For the first time in a RFP experiment a complete set of diagnosticsto measure all the quantities needed to estimate S is available. Due to thehigh plasma currents (up to 1.1 MA) obtained in RFX, a broad range of Svalues is available for scaling. The results are compared with numericalMHD simulations (SPECYL code) providing a reasonable agreement(αexp = -0.18±0.02, αSPECYL = -0.22). Themodification to the expected scaling law due to viscous effects is alsodiscussed.We also perform a comparison of the amplitude of magnetic fluctuationsin discharges with different characteristics: standard, pulsedpoloidal current drive (PPCD), quasi single helicity and rotating lockedmode induced by an external rotating toroidal field modulation. Areduced level of fluctuations is obtained during PPCD operations, althoughthe dependence on S is the same. Concerning confinement time, at fixedI/N≈3×1014 A m, a favourable scaling with S is found. Itsinterpretation in terms of the simple Rechester-Rosenbluth model is brieflydiscussed.
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