Turbulence spreading and its effects on the edge flows and turbulence during sawtooth cycles in the J-TEXT tokamak plasmas

Abstract

Turbulence spreading and its effects on the edge flows and turbulence during sawtooth cycles in the J-TEXT tokamak plasmas are presented. These experiments were performed by Langmuir probe array and electron cyclotron emission. This study aims to understand the rapid transport phenomenon and the role of turbulence in driving flows. Beyond the mixing radius, the turbulence pulse moves faster than the sawtooth heat pulses. The results confirm the existence of turbulence spreading during sawtooth cycles. As the turbulence and heat pulses propagate to the edge, the edge turbulence, radial electric fields, pressures, and geodesic acoustic modes are all enhanced. Hysteresis relationships between the intensities of the turbulence and the radial electric fields are observed. The radial electric field lags behind the turbulence, and its intensity increases/decreases almost linearly with the increase/decrease in the turbulence intensity. The observation suggests that the edge flows are driven dominantly by turbulence during sawtooth cycles. The weakening/enhancement of the edge flows accompanies the increase/decrease in the ion collision rates during sawtooth cycles.