Study on a tuning-free network for the rf accelerating cavity

Applying a bridged-T type all-pass network to a resonator described as a parallel circuit, the output voltage of the resonator shows a band-pass feature over a certain frequency range, while the input impedance is always constant against frequency. This feature is considered to realize the ferrite-loaded tuning-free rf accelerating cavity. It has several merits such as a simple cavity structure without bias windings, an easy operation without feedback control of the bias current, applying new ferrite with favorable rf characteristics and so on. The accelerating system is applicable to a proton-synchrotron for radio therapy or a cooler-synchrotron for nuclear physics studies in a multi-GeV region. This paper presents a theory of the system, the characteristics of the new ferrite, which is currently developed, and design studies of the network based on preliminary measurements of an equivalent lumped circuit.