Arrival time fluctuation of the SwissFEL photocathode laser: characterization by a single color balanced cross correlator

• Main Authors: Cavalieri, A.L (Author), Dax, A. (Author), Divall, E. (Author), Hauri, C.P (Author), Huppert, M. (Author), Resan, B. (Author), Schaedler, M. (Author), Sydlo, C. (Author), Trisorio, A. (Author), Vicario, C. (Author)
• Format: Article
• Language: English
• Published: NLM (Medline) 2022
• Online Access: View Fulltext in Publisher

 The arrival time jitter and drift of the photocathode drive laser has an important impact on the performance of a Free-Electron-Laser (FEL). It adversely affects the beam energy jitter, bunch length jitter and bunch arrival time jitter, which becomes especially important for pump-probe experiments with femtosecond time resolution. To measure both parameters background free and stabilize the drift of the Yb:CaF2 based laser we use a well designed balanced optical cross correlator. In this paper we present our results using this device and focus particularly on the performance of the amplifier. We achieve a laser drift of less than 200 fs during 60 h, a 4.5 fs rms jitter of the amplifier relative to its seeding oscillator and 11 fs rms for the whole laser relative to a reference clock integrated from 2 mHz to 100 Hz.