Design of the P2001 ECH launcher for DIII-D

ECH launchers typically use a moveable mirror to steer a gyrotron beam. Increased power handling capability in an ECH launcher requires adding mass or active cooling to the mirrors. The additional forces on the moveable mirror resulting from either approach typically require a compromise between the power handling capability and the steering capability. The P2001 launcher, designed by PPPL for DIII-D, will launch two 800kW beams for 10 seconds every 10 minutes. Fully independent poloidal and toroidal steering during and between pulses, and a fast poloidal scan capability, will be provided. These design requirements are satisfied by the use of an innovative steering mechanism, which covers the entire scanning range about two axes and is strong enough to withstand the electromagnetic forces on the mirror. An innovative mirror design uses high thermal conductivity materials arranged in a manner that limits the eddy currents during a disruption. In this paper, the design of the P2001 launcher is presented, along with performance calculations. Design features relevant to advanced fusion experiments are highlighted and discussed.