High-time-resolution beam loss monitoring technology for Hefei Light Source II

<bold>Background</bold>Beam loss monitoring is critical for ensuring the stable operation and performance optimization of synchrotron radiation facilities.<bold>Purpose</bold>This study aims to develop and implement a high-time-resolution monitoring system for analyzing bunch-by-bunch beam loss characteristics during the operation of the Hefei Light Source II (HLS-II).<bold>Methods</bold>Firstly, a synchronized monitoring system was developed using an EJ-200 scintillator detector (pulse rise time: 0.9 ns, decay time: 2.1 ns), a strip-electrode beam position monitor (BPM), and a high-speed oscilloscope with 16×10⁹ s^-1 sampling rate. Then, the system's accuracy was validated through simulation and experimental measurements, with correlation coefficient of <italic>R</italic>=0.978 between simulated and measured pulse waveforms. Subsequently, an asymmetric Gaussian fitting algorithm was developed to extract beam loss pulse parameters and resolve overlapping signals during high-loss-rate scenarios. Finally, the HOTCAP (High-speed Oscilloscope-based Three-dimensional bunch-by-bunch Charge And Position measurement) software package was employed to extract bunch-by-bunch charge and position information from BPM signals, and data synchronization was achieved by aligning bunch indices based on the unique 34+1 filling pattern of the HLS-II storage ring.<bold>Results</bold>Experimental results show that the bunch-by-bunch beam loss distribution exhibits significant correlation with the charge distribution during steady-state operation with 35 bunches at 300 mA average current, consistent with the theoretical predictions of random beam loss mechanisms. During transient injection processes, a previously unreported beam loss phenomenon is observed: significant beam loss occurs simultaneously in both the injected bunch and the 14th stored bunch following it, with loss rates significantly higher than other stored bunches. The system demonstrates bunch-by-bunch beam loss discrimination capability under steady-state conditions with bunch spacing of 4.9 ns.<bold>Conclusions</bold>The developed system successfully achieves synchronized acquisition of bunch-by-bunch charge, transverse position, longitudinal position, and beam loss data with nanosecond-level time resolution. Simulation analysis indicates that the system can resolve bunch-by-bunch beam loss in storage rings with bunch spacing greater than 9.7 ns (for amplitude ratios between 0.3 and 3). The discovery of correlated beam loss between the injected bunch and the 14th stored bunch provides new insights into injection dynamics and beam instability mechanisms, offering valuable technical support for optimizing injection efficiency and reducing beam loss in synchrotron radiation facilities.