Experimental study on beam-photoelectron instability in BEPC

A vertical coupled bunch instability explained as the photoelectron instability (PEI) was observed in the Photon Factory at KEK. To further investigate the instability, the experiments on the PEI have been carried out in Beijing Electron Positron Collider (BEPC) with the collaboration between IHEP, China and KEK, Japan. Many interesting phenomena have been observed for different sets of parameters.