HIGH-CURRENT EFFECTS IN THE PEP-II STORAGE RINGS

High beam currents in PEP-II have been a challenge for vacuum system and ring components. For the 1c m long bunches peak currents exceed 100 A and modest impedance can give rise to voltage spikes and discharges. During the last two runs, difficulties arose from rf seals at the "flex flanges" in the HER. High temperatures were seen and the seals turned out to be severely damaged by discharges. In the LER, the horizontal stripline kickers of the bunch-by-bunchfeedback system experiences break- down at high bunch current—Macor pins installed for me- chanical stability turned out to be a weak spot causing dis- charges. Finally, in the HER an experiment to shorten the ion-clearing gap in the beam revealed signs of ion-induced instabilityindicating that the HER has been operating quite close to the stability limit. The effects shown here are relevant to future high- intensity electron and positron rings like SuperB(1) and PEP-X(2).