Tests of a high‐power folded waveguide coupler for ICRF heating

A full‐scale folded waveguide coupler has been fabricated which will provide information on power handling, impedance matching, and multipactor effects. The coupler dimensions are 30×60×300 cm. The cross section of the coupler is small enough that a phased pair of couplers could be placed in a single Tore Supra or TFTR port. A single coupler could be placed in a CIT‐size port. A movable back plate allows frequency adjustment over the range 78–140 MHz. Impedance matching at the waveguide has been achieved using a movable coaxial transmission line feed. Bench‐top comparisons with loop antennas have been made. The folded waveguide coupler will be mounted on the Radio Frequency Test Facility for high‐power tests up to 1.5 MW.