Trapped ions and beam lifetime in NSLS storage rings

Ion trapping observed in most electron storage rings causes various degree of deleterious effects both on brightness and on beam lifetime. Ion trapping is worst in the initial stages of operation when pressure due to synchrotron desorption is high. Based on these observations, various theories to explain the phenomenon have been developed. Depending on specific machines and on the seriousness of their problem, individualized cures have been adopted to eliminate or to cope with ion trapping. It is fair to say that the present understanding of ion trapping is incomplete partially due to lack of quantitative comparison between theory and experimental investigation and partially due to very different behavior among various machines. In this paper the authors present preliminary results of their continuous studies to understand the ion trapping mechanism in the National Synchrotron Light Source (NSLS) electron storage rings