RF GENERATED VOLTAGE ON THE FARADAY SCREEN OF AN ICRF ANTENNA AND ITSEFFECT ON THE PHAEDRUS-T EDGE PLASMA

Work done on the Phaedrus-T tokamak is summarized regarding RF voltage s induced on the sides of slotted side Faraday screens (FSs). Direct i n-air measurements show voltages induced on slotted side FSs, while th eory and computer simulations suggest that these voltages are induced by radial currents on antenna feeds. Triple probe measurements In the edge region of the Phaedrus-T tokamak suggest that the induced voltage s modify edge plasma parameters and increase sheath potentials, which increase sputtering of the FS material and result in an increase of th e impurity content of the plasma. These effects of the induced voltage s can be eliminated by using insulating plates as FS side limiters.