Direct Measurement of a Toroidally Directed Zonal Flow in a Toroidal Plasma

T. Nishizawa, A. F. Almagri, J. K. Anderson, W. Goodman, M. J. Pueschel, M. D. Nornberg, S. Ohshima, J. S. Sarff, P. W. Terry, and Z. R. Williams

Phys. Rev. Lett. 122, 105001 – Published 15 March 2019

Abstract

Zonal flow appears in toroidal, magnetically confined plasmas as part of the self-regulated interaction of turbulence and transport processes. For toroidal plasmas having a strong toroidal magnetic field, the zonal flow is predominately poloidally directed. This Letter reports the first observation of a zonal flow that is toroidally directed. The measurements are made just inside the last closed flux surface of reversed field pinch plasmas that have a dominant poloidal magnetic field. A limit cycle oscillation between the strength of the zonal flow and the amplitude of plasma potential fluctuations is observed, which provides evidence for the self-regulation characteristic of drift-wave-type plasma turbulence. The measurements help advance understanding and gyrokinetic modeling of toroidal plasmas in the pursuit of fusion energy.

Received 25 December 2018
Revised 16 February 2019

DOI:https://doi.org/10.1103/PhysRevLett.122.105001

Physics Subject Headings (PhySH)

Drift waves Plasma transport Plasma turbulence

Plasma Physics

Authors & Affiliations

T. Nishizawa^1,*, A. F. Almagri¹, J. K. Anderson¹, W. Goodman², M. J. Pueschel³, M. D. Nornberg¹, S. Ohshima⁴, J. S. Sarff¹, P. W. Terry¹, and Z. R. Williams¹

¹Department of Physics, University of Wisconsin–Madison, Madison, Wisconsin 53706, USA
²Electrical Engineering Department, University of Wisconsin–Madison, Madison, Wisconsin 53706, USA
³Institute for Fusion Studies, University of Texas at Austin, Austin, Texas 78712, USA
⁴Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011, Japan