FLUID VELOCITY AND ELECTROMAGNETIC FORCES MEASURED BY A ROTATING LANGMUIR PROBE IN THE SCRAPE-OFF LAYER OF JFT-2M

Measurements obtained by the novel technique of an assembly of planar Langmuir probes rotating in the scrape-off layer of JFT-2M are describ ed. The probes scan the radial direction and rotate 360 degrees so mea suring the direction of the magnetic field and the density of current in the magnetic surfaces. Experiments carried out with and without div ertor biasing lead to the following main results: (1) The direction of the ion flow has been measured. (b) It has been found that j x B not equal 0 with the resulting force always directed towards the magnetic axis. (c) By applying a negative divertor bias a narrow layer appears where the current flows in a direction opposite to the main plasma cur rent.