DESIGN AND INITIAL TESTS OF A LOW-VOLTAGE STACKED STRIPLINE FAST-WAVELAUNCHER IN THE PHAEDRUS-T TOKAMAK

A new type of antenna for launching waves in the ion cyclotron frequen cy range in toroidal plasma devices has been developed and tested in t he Phaedrus-T tokamak. This antenna, a stacked stripline (SSL), genera tes a radiofrequency (RF) magnetic field similar to that of a conventi onal strap antenna but develops voltages 2 orders of magnitude less, a nd can operate without a Faraday shield. In comparison tests with a co nventional strap antenna at a power level of 60 kW, the RF induced den sity rise and the impurity production (as indicated by soft X ray and loop voltage increases) were reduced by a factor of 3. In addition, it was demonstrated that capacitive loading effects were reduced or elim inated in comparison with those observed on a conventional strap anten na operated without a Faraday shield, and in the operation of a pair o f SSL antennas at 90 degrees phase small current drive effects were ob served.