Solving the problem of heating of RF contacts in cavity tuners

The accelerating cavity of the ASTRID Electron Synchrotron was studied. The cavity is a capacity loaded TEM cavity resonating at 104.95 MHz. Two plungers driven in parallel keep the cavity in tune, yielding a tuning range of about 0.8 MHz to compensate the beam loading. The RF spring contact liners placed on the entrance of the plunger housing are used to isolate the plunger housing from the RF field. The surface current flowing through the contacts limits the power in the cavity to less than 5 kW due to heating. We analyse the electrodynamics of the tuner and investigate two options of a new tuner geometry, one with contacts and one without contacts. The new design should remove the power limitation due to contact problems.