A sensitive high repetition rate arrival time monitor for X-ray free electron lasers

• Published in: Nature communications Vol. 14; no. 1; p. 2495
• Main Authors: Diez, Michael, Kirchberg, Henning, Galler, Andreas, Schulz, Sebastian, Biednov, Mykola, Bömer, Christina, Choi, Tae-Kyu, Rodriguez-Fernandez, Angel, Gawelda, Wojciech, Khakhulin, Dmitry, Kubicek, Katharina, Lima, Frederico, Otte, Florian, Zalden, Peter, Coffee, Ryan, Thorwart, Michael, Bressler, Christian
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 29.04.2023; Nature Publishing Group; Nature Portfolio
• Subjects: 639/624/1107; 639/766/400/1106; 639/766/930/12; characterization and analytical techniques; Diamonds; Effective medium theory; Experiments; Free electron lasers; Humanities and Social Sciences; Interferometers; Laboratories; Lasers; multidisciplinary; optical techniques; OTHER INSTRUMENTATION; Pulse repetition rate; Refractivity; Repetition; Science; Science (multidisciplinary); Silicon nitride; Temporal resolution; Thermal stability; Time lag; Time measurement; Timing jitter; x-rays
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-38143-y

X-ray free-electron laser sources enable time-resolved X-ray studies with unmatched temporal resolution. To fully exploit ultrashort X-ray pulses, timing tools are essential. However, new high repetition rate X-ray facilities present challenges for currently used timing tool schemes. Here we address this issue by demonstrating a sensitive timing tool scheme to enhance experimental time resolution in pump-probe experiments at very high pulse repetition rates. Our method employs a self-referenced detection scheme using a time-sheared chirped optical pulse traversing an X-ray stimulated diamond plate. By formulating an effective medium theory, we confirm subtle refractive index changes, induced by sub-milli-Joule intense X-ray pulses, that are measured in our experiment. The system utilizes a Common-Path-Interferometer to detect X-ray-induced phase shifts of the optical probe pulse transmitted through the diamond sample. Owing to the thermal stability of diamond, our approach is well-suited for MHz pulse repetition rates in superconducting linear accelerator-based free-electron lasers. In time-resolved measurements it is crucial to know the time delay between the exciting and probing light pulses. Here the authors demonstrate a self-referencing common-path interferometer method measuring the arrival time between the X-ray free electron laser and the optical pulse to the target and thus their inherent timing jitter.