A folded waveguide ICRF antenna for PBX-M and TFTR

Abstract

The folded waveguide (FWG) antenna is an advanced ICRF launcher under development at ORNL that offers many significant advantages over current‐strap type antennas. These features are particularly beneficial for reactor‐relevant applications such as ITER and TPX. Previous tests of a development folded waveguide with a low density plasma load have shown a factor of 5 increase in power capability over loop antennas into similar plasma conditions. The performance and reliability of a FWG with an actual tokamak plasma load must now be verified for further acceptance of this concept. A 58 MHz, 4 MW folded waveguide is being designed and built for the PBX‐M and TFTR tokamaks at Princeton Plasma Physics Laboratory. This design has a square cross‐section that can be installed as either a fast wave (FW) or ion‐Bernstein wave (IBW) launcher by 90° rotation. Two new features of the design are: a shorter quarter‐wavelength resonator configuration and a rear‐feed input power coupling loop. Loading calculations with a standard shorting plate indicate that a launched power level of 4 MW is possible on either machine. Mechanical and disruption force analysis indicates that bolted construction will withstand the disruption loads. An experimental program is planned to characterize the plasma loading, heating effectiveness, power capability, impurity generation and other factors for both FW and IBW cases. High power tests of the new configuration are being performed with a development FWG unit on RFTF at ORNL.