Evidence for High-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>m</mml:mi></mml:math>Secondary Islands Induced by Large Low-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>m</mml:mi></mml:math>Islands in a Tokamak Plasma

Abstract

Small-scale structures with high poloidal mode numbers (m=10-20) have been observed in the TEXTOR tokamak plasma with pulsed radar reflectometry and an electron cyclotron emission diagnostic, in conjunction with large 2/1 and 1/1 islands. The small islands have a peaked density profile, similar to that of the simultaneously observed large-scale 2/1 islands. This together with the observation that high-frequency density and temperature fluctuations are very pronounced near the X points of the large islands hints to a strongly perturbed magnetic topology around the X points.