Pressure and potential measurements in IMS during electron cyclotron heating

Two-dimensional measurements of the plasma pressure have been made in the Interchangeable Module Stellarator (IMS) at two separate toroidal locations. The results indicate that the profile is hollow during Electron Cyclotron Heating (ECH) and that there is a significant variation of the plasma pressure on the magnetic surfaces towards the plasma edge. Also, two emissive probes are aligned along a magnetic field line in vacuum by using one probe to detect the emitted electrons from the other. The locus of detected peaks in the current agree well with the numerical calculation of the magnetic surface. Measurements of the space potential on a flux surface indicate a maximum on the outboard side of the torus and a possible m=1 structure. (author)