HZB, Berlin, Germany
At the light source BESSY II numerous experiments as well as machine development studies benefit from a very flexible and stable fill pattern: standard operation mode comprises a multibunch train for the average users, a purity controlled high current camshaft bunch in a variable length ion clearing gap for pump/probe experiments and a mechanical pulse picking chopper, three high current bunches for femto second slicing opposite to the gap and a specific bunch close to the end of the ion clearing gap for resonant excitation pulse picking. The fill pattern generator and control software is based on a state machine. It controls the full chain from gun timing, linac pulse trains, injection and extraction elements as well as next shot predictions allowing triggering the next DAQ cycle. Architecture and interplay of the software components as well as implemented functionality with respect to hardware control, performance surveillance and reasoning of next actions, radiation protection requirements are described.
HZB, Berlin, Germany
Full stability potential of orbit and bunch-by-bunch-feedback controlled top-up operation becomes available to the experimental users only if the remaining slow drifts of essential operational parameters are properly compensated. At the light source BESSY II these are the transversal tunes as well as the path length and energy. These compensations are realized using feedback control loops together with supervising state machines. Key to the tune control is a multi-source tune determination algorithm. For the path length correction empirical findings are utilized. All involved software systems and data-paths are sketched.
