A sensitive high repetition rate arrival time monitor for X-ray free electron lasers
Michael Diez, Henning Kirchberg, Andreas Galler, Sebastian Schulz, Mykola Biednov, C. Bömer, Tae‐Kyu Choi, Angel Rodríguez-Fernández, Wojciech Gawełda, Dmitry Khakhulin, Katharina Kubiček, Frederico A. Lima, Florian Otte, Peter Zalden, Ryan Coffee, Michael Thorwart, Christian Bressler
Abstract
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.