Performance tests of a ferrite-loaded cavity under operation conditions

The ferrite loaded, tunable reentrant-coaxial symmetric (2×λ/4) accelerator cavity for the cooler synchrotron COSY is of the SATURNE type. For h=1, frequencies range from 450 kHz at injection to a maximum of 1.6 MHz, with a maximum rf power level of 50 kW. We have determined the cavity circuit properties both at low signal levels with standard rf test equipment, and at operation conditions, depending on frequency and power level. Moreover, the acceleration system was tested for its suitability to pass through gamma transition. For this end, a sudden phase jump of 180° was imposed at the input of the amplifier chain by means of the digital frequency synthesizer developed for COSY. At higher frequencies, a loss of Q was observed, partly aiding the transition crossing speed. Finally, a simple replacement circuit, incorporating the measured quantities, is used to model the cavity