THE FOLDED WAVE-GUIDE - A HIGH-FREQUENCY RF LAUNCHER

The folded waveguide, an alternative to loop antennas for launching po wer in the ion cyclotron range of frequencies (ICRF) into plasma devic es, operates as a cavity with apertures for coupling RF power to the p lasma. The RF field pattern is similar to that of a loop antenna, but with a lower ratio of electric to magnetic field. Power enters from a coaxial line via a sliding contact, whose position matches impedances between the coaxial line and the folded waveguide. The folded waveguid e has operated at 1 MW and promises high power density. Calculations i ndicate a factor of 4 increase in power handling capability over a com parable loop antenna. The possible use of the folded waveguide on seve ral tokamaks is discussed.