Observations and Cures of Electron-cloud Effects at the Kekb Low Energy Ring

The single-beam blowup at LER was first observed in March 1999[2] using an interferometer for the synchrotron light[3]. The vertical beam size scaled at the interaction point is typically 2 μm at a low current, and starts to blowup around 350 mA for a long train of bunches with 4-bucket spacing. Here “long train” means a single train to fill the 90% of the ring, devoting the remaining 10% as the gap for the abort kicker. In the case of 4-bucket spacing, which has been used as a standard pattern for a physics run, a train consists of 1150 bunches. One bucket spacing is 2 ns. The vertical size reaches about 6 μm at 600 mA when no cure is made by the permanent or solenoid magnets. The blowup is characterized as: