The effect of a weak rotating magnetic field on an ECR discharge plasma inargon has been investigated. The field was produced by an arrangement of barssurrounding the discharge vessel and carrying harmonic currents appropriatelyshifted in phase. Optical probes, Thomson scattering, Li beam diagnostics anda fast CCD camera were used for the investigations. A significant modulationof the electron density and temperature at the plasma edge was observed. Thiscan be assigned to an increase of the transport of electrons to the dischargevessel walls where the lines of the total B field cross them. Alteration ofthe transport conditions results in perturbations, which diffuse radiallyinwards at a velocity corresponding to that of the Bohm diffusion. A patternof light emission develops, which rotates synchronously with the rotatingfield. Correlation between the total light emission from different plasmavolumes was determined based on measurements made with optical probes. Thisshows fluctuations propagating azimuthally, anticlockwise with respect to thedirection of the main B field, with a wavelength of about (7-10) ×10-2 m. These fluctuations exist independently of the presence of therotating magnetic field. Further investigations are still needed to answer twokey questions: does the plasma rotate as a whole or is the observed effect arotation of the plasma state only, and how does the rotating field affectfluctuations at the plasma edge?
Active probe experiments at the Wendelstein 7-AS stellarator