1. CAN WE BUILD A SINGLE BUNCH FEEDBACK Eric Plouviez ESRF Diagnostic group

2. Single bunch transverse instability signal Very high frequency signals due to  and  rise ~ 1/2  s  several 10.GHz for a 50ps long bunch)

3. Case of an effective feedback if the damping time t is shorter than 1/  s => simpler time pattern => lower frequencies: 2 “samples” / bunch length could do?

4. Bunch motion “sampling’ 1 sample = center of mass detection and correction 2 samples = additional detection and correction of the head to tail differential motion

5. Head to tail motion manipulation Harmonic mixing of the beam signal with a manageable frequency (~1GHz) Horizontal scale:10ps /div

6. Technology BPM: some synchronous detection of pickups signals with the detection oscillator zero crossing at the bunch center Kicker: A stripline fed with a 1GHz signal, modulated by the correction signal =>sampling by the beam of the 1GHz carrier

7. Question Is it that simple? Can modes with higher frequencies signals build up without being sensitive to the feedback

8. Microwave pick ups 10GHz pill box cavities coupled to the beam by a ceramic iris