Speaker
Description
Precise beam manipulation and preservation of beam quality along the beamline are essential to produce high-brightness X-ray Free Electron Lasers (XFELs). These tasks can be effectively carried out through accurate beam diagnostics. In addition, a calibrated simulation model enables investigation of the optimal beamline conditions against collective effects such as coherent synchrotron radiation and longitudinal space charge, which cause nonlinear distortions in the beam phase space. At the Pohang Accelerator Laboratory (PAL) XFEL facility, complete six-dimensional phase space reconstruction using neural networks and differentiable simulations has been successfully demonstrated along the first bunch compressor section. In this paper, we present simulation and experimental demonstrations of simulation model calibration using the reconstructed phase space information as input beam parameters. We show how to perform model calibration with multiple wire-scan measurements obtained under various beamline conditions, together with several optimization methods such as evolutionary strategies and Bayesian optimization. In addition, we further discuss model uncertainty and the sensitivity of model elements. Furthermore, we present the optimal beamline settings that preserve beam quality along the undulator section. It is expected that this model calibration can be incorporated into the digital twin frameworks in the future for online, virtual diagnostics and robust optimizations.
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