SELF EXCITED OPERATION FOR A 1.3 GHz 5-CELL SUPERCONDUCTING CAVITY

Self-excited operation of a resonant system does not require any external frequency tracking as the frequency is determined by the phase lag of the self-excited loop, it is therefore particularly useful for testing high Q RF cavities that do not have an automatic tuning mechanism. Self-excited operation has long been shown to work with single-cell cavities. We have recently demonstrated that it is also possible for multi-cell cavities, where multiple resonant modes are present. The Cornell 1.3 GHz 5-cell superconducting cavities were operated using self-excited operation and we were able to lock onto the accelerating π mode, despite the presence of neighbouring modes that were less than 10 MHz away. By means of the loops phase advance, we were able to select which mode was excited.