RF modeling and design of a folded waveguide launcher for the Alcator C-Mod tokamak

The folded waveguide (FWG) launcher is being investigated as an improved antenna configuration for plasma heating in the ion cyclotron range of frequencies (ICRF). A development FWG launcher was successfully tested at Oak Ridge National Laboratory (ORNL) with a low-density plasma load and found to have significantly greater power density capability than current strap-type antennas operating in similar plasmas. To further test the concept on a high density tokamak plasma, a collaboration has been set up between ORNL and Massachusetts Institute of Technology (MIT) to develop and test an 80-MHz, 2-MW FWG on the Alcator C-Mod tokamak at MIT. The radiofrequency (RF) electromagnetic modeling techniques and laboratory measurements used in the design of this antenna are described in this paper, A companion paper describes the mechanical design of the FWG.