Tune Feed-forward for Pep-ii*

The PEP-II B-Factory achieved design performances in 2000. The tune shifts of the rings are already about twice the design numbers of 0.03. This requires constant adjustments from the operators during fills and top-offs. A tune feedback was envisioned first, but the wide, multi-peaked tune signals make it tricky even for a human to adjust the tunes correctly. Since tunes are strongly correlated with the currents in the high and low energy rings (HER and LER), a tune feed-forward system was implemented. Each ring uses the measured dependences on its own current of about + or -0.018 per Ampere for the xor y-tune. There is also a provision to adapt to the other beam's current. This parameter is usually a factor of ten lower. How these parameters change for different scenarios like optimizing the visual tune profile, the luminosity, or the measured single beam tune peak is discussed. Presented at IEEE Particle Accelerator Conference (PAC 2001) Chicago, Illinois, 18-22 Jun 2001 * Work supported by Department of Energy contract DE–AC03–76SF00515.