Diffractive fluence mapping

The FEL fluence spatial distribution on the target can be mapped by drilling customized diffraction gratings on the sample membrane, providing real space imaging of the beam spot at the sample plane. This can be used to properly align the sample on the beam focus and to recover the single shot intensity profile of the pulse used in the experiment.

Schneider et al., Nature Communications, Vol. 9 - 1, pp. 214 (2018).

Fluence mapping of pulse spot by diffraction gratings

XUV magnetic diffraction signals from solid samples are acquired in tandem with the corresponding single-shot spatial fluence distribution. Our in situ characterization scheme enables direct monitoring of the target illumination, providing a basis to optimize and quantitatively understand FEL experiments.

Diffraction images of the spot have been acquired at different positions along the beam propagation axis, allowing a fast and easy characterization of the beam waste and the proper positioning of the target in the interaction region. Comparison with wave front sensor reconstructions and atomic force microscopy images of single shot damage craters in the sample substrate, demonstrate very good agreement.

This approach allows for a simultaneous, non-invasive mapping of the fluence distribution on the sample together with a scattering experimental signal, providing an instantaneous online focus imaging without need of further computation. In the study of fluence-dependent phenomena, it provides crucial information for the correct interpretation of the data.

Retrieve article

In situ single-shot diffractive fluence mapping for X-ray free-electron laser pulses.

M. Schneider, C.M. G√ľnther, B. Pfau, F. Capotondi, M. Manfredda, M. Zangrando, N. Mahne, L. Raimondi, E. Pedersoli, D. Naumenko, S. Eisebitt.

Nature Communications, Vol. 9 - 1, pp. 214 (2018).

DOI: 10.1038/s41467-017-02567-0

Last Updated on Friday, 22 May 2020 12:14