TY - JOUR
T1 - Xcalib
T2 - a focal spot calibrator for intense X-ray free-electron laser pulses based on the charge state distributions of light atoms
AU - Toyota, Koudai
AU - Jurek, Zoltan
AU - Son, Sang Kil
AU - Fukuzawa, Hironobu
AU - Ueda, Kiyoshi
AU - Berrah, Nora
AU - Rudek, Benedikt
AU - Rolles, Daniel
AU - Rudenko, Artem
AU - Santra, Robin
N1 - Funding Information:
RIKEN, Proposal Program of SACLA Experimental Instuments (award to HF, KU); Japan Society for the Promotion of Science (grant No. JP15K17487 to HF); Ministry of Education, Culture, Sports, Science and Technology of Japan, the X-ray Free Electron Laser Utilization Research Project and the X-ray Free Electron Laser Priority Strategy Program (award to HF, KU); Ministry of Education, Culture, Sports, Science and Technology of Japan, Dynamic Alliance for Open Innovation Bridging Human, Environment and Materials (award to HF, KU); Tohoku University, Institute of Multidisciplinary Research for Advanced Materials (award to HF, KU); US Department of Energy, Chemical Sciences, Geosciences, and Biosciences Division (grant No. DE-SC0012376 to NB; grant No. DE-FG02-86ER13491 to DR, AR).
Publisher Copyright:
© 2019 International Union of Crystallography.
PY - 2019/7/1
Y1 - 2019/7/1
N2 - 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.
AB - 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.
KW - Ab initio calculation
KW - Beam profile
KW - Calibration
KW - Characterization
KW - Charge state distribution
KW - First-principles calculation
KW - Spatial fluence distribution
KW - X-ray free-electron laser
KW - XFEL
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U2 - 10.1107/S1600577519003564
DO - 10.1107/S1600577519003564
M3 - Article
C2 - 31274423
AN - SCOPUS:85066839727
VL - 26
SP - 1017
EP - 1030
JO - Journal of Synchrotron Radiation
JF - Journal of Synchrotron Radiation
SN - 0909-0495
ER -