Digital base-band rf control system for the superconducting Darmstadt electron linear accelerator

Institut fu¨r Kernphysik, Technische Universita¨t Darmstadt, D-64289 Darmstadt, Germany(Received 31 January 2012; published 17 May 2012)The accelerating field in superconducting cavities has to be stabilized in amplitude and phase by aradio-frequency (rf) control system. Because of their high loaded quality factor superconducting cavitiesare very susceptible for microphonics. To meet the increased requirements with respect to accuracy,availability, and diagnostics, the previous analog rf control system of the superconducting Darmstadtelectron linear accelerator S-DALINAC has been replaced by a digital rf control system. The newhardware consists of two components: An rf module that converts the signal from the cavity down to thebase-band and a field-programmable gate array board including a soft CPU that carries out the signalprocessing steps of the control algorithm. Different algorithms are used for normal-conducting andsuperconducting cavities. To improve the availability of the control system, techniques for automaticfirmware and software deployment have been implemented. Extensive diagnostic features provide theoperator with additional information. The architecture of the rf control system as well as the functionalityof its components will be presented along with measurements that characterize the performance of thesystem,yielding, e.g.,anamplitudestabilization down to ð A=AÞ