Magnetic fluctuation induced transport in MST (abstract)a)

Abstract

We made local measurements of the magnetic fluctuation induced transport of particles and energy in the outer region (r/a≳0.75) of the MST reversed field pinch plasma. These measurements allow comparison with the Rochester–Rosenbluth stochastic diffusion coefficients. An electrostatic electron energy analyzer and fast pyrobolometer were employed in combination with magnetic pickup coils to directly measure the correlated products 〈J̃θB̃r〉 and 〈q̃∥B̃r〉, respectively. Magnetic fluctuation induced transport of both particles and energy is negligible at the extreme edge of MST (r/a≳0.9), but increases to a level consistent with estimates of the entire particle and energy flux as the core is approached (5×1021 m−2 s−1 and 105 W m−2). Stochastic particle transport is limited by an apparent ambipolar electric field to the ion stochastic diffusion rate (D=50 m2 s−1), the electron transport being dominated by the energetic component of the distribution (E≳50 eV). The measured heat transport is consistent with the convective energy transport carried by the fast electron component (Teffective=100 eV).