Algorithms and implementations of APT resonant control system

A digital signal processor is implemented to control the resonant frequency of the RFQ prototype in APT/LEDA. Two schemes are implemented to calculate the resonant frequency of the RFQ. One uses the measurement of the forward and reflected fields. The other uses the measurement of the forward and transmitted fields. The former is sensitive and accurate when the operation frequency is relatively far from the resonant frequency. The latter gives accurate results when the operation frequency is close to the resonant frequency. Linearized algorithms are derived to calculate the resonant frequency of the RFQ efficiently using a fixed-point DSP. The control frequency range is about 100 kHz for 350 MHz operation frequency. A frequency agile scheme is employed using a dual direct digital synthesizer to drive the klystron at the cavity´s resonant frequency (not necessarily the required beam resonant frequency) in power-up mode to quickly bring the cavity to the desired resonant beam frequency. This paper will address the algorithm implementation and error analysis, as well as related hardware design issues