We report experimental demonstration of capturing single-shot X-ray Free-electron Laser (FEL) beam profiles using gas fluorescence. The measurement was carried out at the Linac Coherent Light Source using 7 keV hard X-rays propagating through ambient air. The nitrogen fluorescence emitted upon the passage of the X-ray FEL beam were imaged using a highly sensitive optical setup, and there was sufficient optical yield that single-shot measurements were feasible. By taking two orthogonal and simultaneous images, the beam trajectory could be determined in a nearly non-invasive manner, and is best suited for photon energies in the soft X-ray regime, where such a diagnostic capability has been largely unavailable previously. The integrated intensity of the images could also serve as a non-invasive intensity monitor, complementary to current implementations of gas- and solidbased monitors. High repetition-rate Free-electron Lasers can greatly benefit from such a new diagnostic tool for eliminating potential thermal damages.
Yiping Feng, Diling Zhu, Clemens Weninger, Roberto Alonso-Mori, Matthieu Chollet, Daniel S. Damiani, James M. Glownia, Jerome B. Hastings, Silke Nelson, Sanghoon Song, and Aymeric Robert, "Single-shot beam profile diagnostics for x-ray FEL's using gas fluorescence," Proc. SPIE 10237, Advances in X-ray Free-Electron Lasers Instrumentation IV, 102370M (Presented at SPIE Optics + Optoelectronics: April 27, 2017; Published: 14 June 2017); https://doi.org/10.1117/12.2268862.
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