High CW power, phase and amplitude modulatorrealized with fast ferrite phase-shifters

Superconducting cavity resonators are suffering from detuning effects caused by high internal electromagnetic fields (Lorentz force detuning). For classical resonators working with continuous wave signals, this detuning is static and compensated by the slow mechanical tuning system. However, pulsing of superconducting cavities, an operational mode only recently considered, results in dynamic detuning effects. New ways to handle this effect have to be found and worked out. A way to supply several superconducting cavities in the particle accelerator by one large transmitter while keeping the possibility of controlling the field in each individual cavity is shown. By introducing a fast phase and amplitude modulator into each cavity feeder line, the individual deviations of each cavity with respect to the average can be compensated in order to equalize their behaviour for the main control loop, which will compensate the global detuning of all cavities. Several types of phase and amplitude modulators suitable for high power RF application, as well as different types of the fast variable phase-shifters for use in the modulator are analysed. The results of the work are foreseen to be applied in the field of particle accelerators but are certainly also interesting for other high power RF domains e.g. tuning devices for industrial microwave heating, plasma applications or nuclear fusion reactors.