Experimental Observation of the Shear Alfvén Resonance in a Tokamak

Abstract

Experiments in Tokapole II demonstrate the shear Alfv\'en resonance in a tokamak by direct probe measurement of the wave magnetic field within the plasma. The resonance is driven by external antennas and is identified as radially localized enhancements of the poloidal wave magnetic field. The radial location agrees with calculations which include toroidicity and noncircularity of the plasma cross section. Other properties such as polarization, radial width, rise time, and wave enhancement also agree with magnetohydrodynamical theory.