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Description
This work presents a jitter study of the fast intra-pulse feedback loop for RF power stations in SPARC_LAB. To meet the rigorous RF stability demands of next-generation accelerators, such as the EuPRAXIA facility, the LLRF system in SPARC_LAB has undergone a comprehensive upgrade. The required precision for the phase jitter of RF system in plasma wakefield acceleration is less than 20 fs RMS with respect to the facility reference master oscillator (RMO). A fast feedback loop has been implemented to control this and has been operational at SPARC_LAB since 2008. A reduction in phase jitter from hundreds of femtoseconds down to 50 fs rms had been achieved for S-band klystrons. Recently, further improvements have been made to this feedback loop. The upgrade includes redesigning the loop RF circuit, optimization of error amplification, and modification of remote-control hardware. Some dedicated measurements have been performed to investigate the loop performance. The results show that the jitter can be reduced to less than 15 fs RMS with respect to the RMO. This marks a substantial advancement toward meeting the scientific demands of synchronized RF systems in plasma-based accelerators and provides a path forward for similar systems at higher frequencies.
