All metal support for a central conductor of the ITER ICRF antenna system

One of the major critical points of the ion cyclotron antenna for next-generation Tokamaks is a ceramic support of a central conductor of a coaxial antenna feeder close to the plasma. Enhancement of dielectric loss tangent of ceramics due to neutron irradiation limits power injection capability of the antenna significantly. An all metal antenna support (AMS) employing a ridged waveguide was proposed. The central conductor of the coaxial line connected to the current strap of the antenna is mechanically supported by the AMS. A design of the all metal support was carried out using a calculation for both electrical characteristics and mechanical strength. The electrical characteristics calculation with finite difference time domain (FDTD) method shows that the AMS can be used on the transmission line with quite a small reduction in power transmission capability. It was also confirmed that the mechanical strength is enough against the force caused by eddy current with disruption, with calculation. A real size mock-up of the AMS for low power RF characteristics measurement was fabricated. The RF measurement with the mock-up shows that the power reflection of the all metal support is low enough (<15%) and is close to the FDTD calculation results.