Inward Turbulent Transport Produced by Positively Sheared Radial Electric Field in Stellarators

Inward turbulent particle transport observed in the rf heated plasma of the H-1 toroidal heliac is reproduced in the CHS heliotron/torsatron by generating a region of positive radial electric field shear $(E_r^{\prime }>0\mathrm{})$ using electron cyclotron resonance heating of the plasma edge. Empirical condition of the radial reversal of the turbulent flux derived from two experiments indicates that the shear electric field might be universally responsible for the recorrelation of the density and plasma potential fluctuations leading to the inward transport.