To achieve high-precision, bunch-by-bunch beam cur-rent and lifetime measurements at the Hefei Light Source (HLS), we developed a beam diagnostics system based on interleaved sampling technology, achieving an equivalent sampling rate of 6.5 GHz. In single-bunch mode, amplitude extraction via cross-correlation with a single response function yieds a turn-by-turn current relative resolution of 0.12%. By averaging over 200 turns, the resolution is improved to 0.04% at a 23 kHz data refresh rate, enabling fast and accurate lifetime calculations. However, in multi-bunch high-current mode, large longitudinal oscillations degrade the accura-cy of amplitude extraction when using a fixed-response function. We propose an integration method to mitigate the effects of bunch length and phase oscillations on beam current measurements. The method and experi-mental results provide a practical solution for machines exhibiting large longitudinal oscillations, such as HLS.

Free electron lasers (FEL), which can generate ultra-high brightness rediation are working horses for radiation science research over the world. For FEL, the higher the repetition frequency of the beam in the device, the higher the user's experimental efficiency, and more experimental stations can conduct experiments simultaneously. Therefore, there is a trend to increase the repetition frequency in its development process. Therefore, it is necessary to develop relevant technologies for high repetition frequency FEL. Beam energy is one of the most fundamental and critical parameters in FEL. This paper developed a fusion algorithm based on beam position monitor (BPM) in the dispersion structure of a FEL, which extracts the transverse position of the beam using both the arrival time and amplitude information of the beam, to achieve high-precision and noninterceptive measurement of beam energy. Provide powerful diagnostic, operational, and maintenance tools for high-frequency free electron laser devices.