Unipole Multipactoring Discharge in the LHRF Launcher

The unipole multipactoring discharge in an evacuated waveguide launcher for the lower hybrid range of frequencies (LHRF) heating is studied theoretically and experimentally. When the RF power at 2 GHz is transmitted into a copper-plated waveguide on which the static magnetic field is superimposed, the discharge is accompanied by a large absorption of RF power in the waveguide and a large increase in the temperature of the E-plane wall of the waveguide. A temperature increase of about 100° C/0.1 s at an incident power of 200 kW is observed. The theoretical result of the unipole multipactoring effect shows good agreement with the experimental results.