Measurement of Sudden Beam Loss Events Using Bunch-by-Bunch BPMs at SuperKEKB

Abstract: At SuperKEKB, sudden beam loss (SBL) events pose a significant challenge to stable accelerator operation. To investigate and better understand SBL, we have developed a new Bunch Oscillation Recorder (BOR). Using this newly developed BOR, we successfully observed SBL events and conducted a detailed analysis of the recorded data. By analyzing the patterns of bunch position oscillations and charge loss, we found a strong correlation between SBL events and pressure burst phenomena occurring inside the vacuum chamber. These pressure bursts are known to accompany almost all SBL events, and our analysis shows that the bunch position oscillation patterns vary depending on the location of the pressure burst. Our observations suggest that bunch positions begin oscillation under some influence at the location of the pressure burst. These observations and analyses have significantly advanced our understanding of the causes and mechanisms behind SBL.