期刊
JOURNAL OF SYNCHROTRON RADIATION
卷 26, 期 -, 页码 1017-1030出版社
INT UNION CRYSTALLOGRAPHY
DOI: 10.1107/S1600577519003564
关键词
X-ray free-electron laser; XFEL; calibration; characterization; beam profile; spatial fluence distribution; charge state distribution; ab initio calculation; first-principles calculation
资金
- Japan Society for the Promotion of Science [JP15K17487]
- Ministry of Education, Culture, Sports, Science and Technology of Japan
- X-ray Free Electron Laser Utilization Research Project
- X-ray Free Electron Laser Priority Strategy Program
- Dynamic Alliance for Open Innovation Bridging Human, Environment and Materials
- US Department of Energy, Chemical Sciences, Geosciences, and Biosciences Division [DE-SC0012376, DE-FG02-86ER13491]
- RIKEN, Proposal Program of SACLA Experimental Instuments
- Tohoku University, Institute of Multidisciplinary Research for Advanced Materials
- U.S. Department of Energy (DOE) [DE-SC0012376] Funding Source: U.S. Department of Energy (DOE)
The xcalib toolkit has been developed to calibrate the beam profile of an X-ray free-electron laser (XFEL) at the focal spot based on the experimental charge state distributions (CSDs) of light atoms. Characterization of the fluence distribution at the focal spot is essential to perform the volume integrations of physical quantities for a quantitative comparison between theoretical and experimental results, especially for fluence-dependent quantities. The use of the CSDs of light atoms is advantageous because CSDs directly reflect experimental conditions at the focal spot, and the properties of light atoms have been well established in both theory and experiment. Theoretical CSDs are obtained using xatom, a toolkit to calculate atomic electronic structure and to simulate ionization dynamics of atoms exposed to intense XFEL pulses, which involves highly excited multiple core-hole states. Employing a simple function with a few parameters, the spatial profile of an XFEL beam is determined by minimizing the difference between theoretical and experimental results. The optimization procedure employing the reinforcement learning technique can automatize and organize calibration procedures which, before, had been performed manually. xcalib has high flexibility, simultaneously combining different optimization methods, sets of charge states, and a wide range of parameter space. Hence, in combination with xatom, xcalib serves as a comprehensive tool to calibrate the fluence profile of a tightly focused XFEL beam in the interaction region.
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