Speaker
Description
We present our pulse-multiplexing studies – one of the mid-term strategies at the European X-ray Free Electron Laser (European XFEL). The activity is motivated by hallmark XFEL properties—ultra-high intensity and a high degree of spatial coherence [1-2]—as well as a “MHz repetition rate” that can deliver approximately 400 pulses per each undulator-branch, at 220 ns intervals within a 10 Hz pulse-train format [1-2]. Since the launching of operation in 2018, a growing understanding is such that for various research fields, rarely the all three characteristics (high repetition rate, ultra-high intensity, coherence) are required, and typically the intensity or the repetition rates are excessive for the intended experiments; this then resulted to a significant number of XFEL pulses (or intensities) being discarded, whilst general accessibility to XFEL beam being extremely limited at the same time.
In this work, we address on practices that envision multiplexing mode at the SASE2 (hard X-ray) beamlines of the EuXFEL. Realisation of such scheme not only relaxes setup-time pressure significantly, but envisaged to enhance efficiency and experimental productivity at the same time. Methods that provide versatility and adaptability to changing operation modes are considered; via “redirection” of photon path with existing components; or via “multiplication” by introducing beamsplitting optics; and via manipulation of electron beam operation modes. Naturally, the aim also encompasses the requirement to preserve pulse integrities —such as the wavefront, intensity, and lateral coherence. Particular attention is given to optics which should withstand the extreme radiation and repetition rates. To this end, a preliminary analysis on the MHz repetition pulse wave front modulation is presented, where contributions originating from direct mechanical perturbations — such as low-frequency vibrations of X-ray distribution mirrors [4,6] — could be differentiated from indirect forces acting on electron bunches within the accelerator and undulator systems.
References
[1] Tschentscher, T et al., Appl. Sci. 7, 592. (2017)
[2] Decking, W. et al., Nat. Photon. 14, 391. (2020)
[3] Vagovic, P et al., Optica. 6, 1106 – 1109. (2019)
[4] Schmidtchen, S et al., Proc. SPIE 12694, doi: 10.1117/12.2677287
[5] Seaberg, M et al., J. Synch. Rad. 26, 1115 (2019)
[6] Guest, T.W. et al., J. Synch. Rad. 29, 939 (2022)