General automation of LLRF control for superconducting accelerators

Future and present superconducting linear accelerator projects based on superconducting resonators have tight requirements on field stability that vary with their application. The vacuum ultra violet free electron laser (VUV-FEL) that is currently commissioned at DESY, Hamburg, requires a stability of 10−3 in amplitude and 0.1° in phase. The upcoming X-ray free electron laser (XFEL) is even more demanding by one order of magnitude. Additionally, these machines need to provide a high reliability and availability, since light sources serve as user facilities. Facing the large number of RF stations as for the case of an international linear collider, this is even more challenging. Therefore, a high degree of automation is mandatory for the low level RF (LLRF) control in order to accomplish for these demands. At the VUV-FEL, an automation framework based on the techniques of finite state machines has been developed and tested. It provides already a number of automated procedures that improve the operation of the VUV-FEL. It is a design goal to develop a framework that is general enough to be applied to future accelerator projects.