Status of the new low level RF control system for the DALINAC

The high quality factor of the superconducting 3 GHz cavities of the S-DALINAC in combination with microphonic disturbances leads to permanent fluctuations in amplitude and phase of the accelerating field. These fluctuations increase the energy spread of the beam which has to be compensated by a low level RF control system. To meet the required stability the existing analog control system has to be replaced by a digital one. The existing analog control system converts the 3 GHz signals down to the base band. This concept has also been followed by the new digital system. The digital signal processing is done in a FPGA which allows for a maximum of flexibility in the control algorithms. Superconducting cavities are operated in a self-excited loop whereas a generator driven resonator is used for normal-conducting cavities. This talk covers the implementation of the different control algorithms and reports on results obtained with a prototype.