1. Feedback questions / action-items • How do the beam-based feedback systems deal with exceptions? (Difficult problems) • Startup, beam loss, MPS trip, etc – not cost/RDR issue • Detecting and handing bad sensors or actuators (bpms, etc) – need redundancy – cost for RDR. • Need to include RTML simulations in linac simulations. • Interplay between the various feedbacks and feed-forwards? • How does feedback help the rf specs? [LLRF folks! Sergei] • Understand noise spectrum from rf systems • Understand which parameters beam-based feedback can be fixed and by how much. • How many intra-train feedbacks do we have, and how many pulses do they collectively take to converge? BCD doesn’t have a definitive list of intra-train feedbacks. [JC + PB to check • Relative timing of two linacs (could change within train) • What is the beam stability requirement in the damping ring and turn-around? Spec is driven by BDS requirements. Falls on accelerator physics groups. Assume we need orbit feedback and transverse and longitudinal multi-bunch feedback. • Should feedback be a bunch of individual loops or a global system (trajectory control)? • How does the system deal with error propagation? • What level of adaptation is required for transfer matrices (how stable are the optics, energy profile)? • We need bunch by bunch information from the lumi monitor in real time [detector folks]

2. Feedback questions / action-items 2 • What does it take for the feedback systems to work for single-bunch low current, etc to study luminosity effects and feedback performance? • Need to develop cavity bpm systems that provide bunch-by-bunch information with appropriate performance. • 5Hz feedback requirements of control system: • Flexible synchronous networking so that network does not take substantial fraction of the 200ms. • “Everything” (potential sensors, actuators) should be potentially available to 5Hz feedback systems. Has implications on controls interfaces and on design of the devices themselves. Should develop a list of things that we might want to operate at 5Hz, how fast and how much we want them to move in 200ms. [warm correctors in linac??] Issue of dynamic field response of dipole magnets?? Persistent currents… • Be able to plug in feedback loop where-ever, when-ever… • Is the phase stability of the crab-cavities an issue for this group? LLRF – yes! • DR feedback item: circumference feedback (chicane) • Positron feedback item: circumference/path-length control