Tuning the Linac with Superconducting Resonator Used as a Phase Detector

The ANU Heavy Ion Facility is comprised of a 15 MV electrostatic accelerator and superconducting linac booster. The beam is double terminal stripped to provide high charge states at the entrance to the linac, which consists of twelve È• Split Loop Resonators (SLR). Each SLR needs to be individually tuned in phase and amplitude for optimum acceleration efficiency. The amplitude and phase of the superbuncher and time energy lens also have to be correctly set. The linac set up procedure developed at ANU utilises a beam profile monitor in the middle of a 180 degree achromat and a new technique based on a superconducting resonator operating in a beam bunch detection mode. Both techniques are used to derive a full set of phase distributions for quick and efficient setting up of the entire linac. Verification of the superconducting phase detector is accomplished during routine linac operations and is complemented by longitudinal phase space simulations. The new technique allows better resolution for setting the resonator acceleration phase and better sensitivity to accelerating current. In addition, it is faster to perform, independent of energy and atomic number of the incident beam and less sensitive to beam steering and de-focusing introduced by accelerating resonators.