An external waveguide launcher is an alternative to an internal loop for launching high-power ion cyclotron radiation into the magnetically confined plasma of a fusion reactor. Water, filling the waveguide, can perform the dual function of dielectric medium and coolant, while remaining highly insensitive to the 14-MeV neutron flux from a fusion reactor. Water-filled waveguides provide two distinctive reactor engineering advantages:

  1. The waveguide dimensions for transmitting waves at the ion cyclotron frequencies can be reduced by almost an order of magnitude.
  2. The problem of removing the heat deposited by neutrons throughout the volume of a solid dielectric-filled waveguide is precluded by the flow of a fluid dielectric through the waveguide ducts.
The results of tests on the power-handling capacity of a water-loaded-dielectric waveguide (WR1150) at frequencies of ∼80 MHz are presented. A tunable radio-frequency cavity, which when filled with water resonates at 80 MHz, was used to achieve electromagnetic stress levels that approach that which ion cyclotron heating launchers would have to withstand in a fusion reactor. The tests show that the water-filled WR1150 waveguide is capable of transmitting ≳500 kW at 80 MHz.