Experimental investigation of beam instabilities in BEPCII

With the high current physical operations of the upgraded Beijing Electron–Positron Collider (BEPCII), thresholds on collision luminosity and beam current have been presented due to various factors such as collision background, noise, equipment stability under high power operation, and so on. One of the most serious influences on beam dynamics was beam instability which has been clearly exhibited. The comprehensive experimental investigation of beam instabilities in BEPCII is an indispensable part of beam physics research and can provide references for the upgrade project of BEPCII. Over the past two years, the experimental investigation of beam instabilities in BEPCII has been carried on with the single and multiple bunch filling in the storage ring. Various impedances, the sources of beam instabilities, including broadband and narrowband impedances in longitudinal and transverse planes are studied. The measured impedance values are compared with the initial design of BEPCII.