The ablation imprints method is a well-established approach to thoroughly characterising fluence distributions [J/cm2] of focused short-wavelength free-electron laser beams. For visible and near-infrared laser beams, fluence distribution of the focused beam can also be measured by other means, for example, by projecting a magnified image of the focal spot onto a camera. We studied the viability of the ablation imprints method in the visible and near-infrared spectral range and compared it to the above-mentioned conventional approach. Furthermore, we compared the effects of the X-ray, visible, and near-infrared radiation on the ablation damage. We characterised an X-ray astigmatic focused beam at the Small Quantum Systems instrument of the EuXFEL. At the Prague Asterix Laser System, we successfully characterised the focal spot at 438 nm. At 1315 nm, the ablation imprints method produced partially satisfactory results, and we compared these results with conventional methods. We conclude that the ablation imprints method can characterise focused laser beams in the visible and near-infrared spectral range.
P. Finetti, E. Allaria, B. Diviacco, C. Callegari, B. Mahieu, J. Viefhaus, M. Zangrando, G. De Ninno, G. Lambert, E. Ferrari, J. Buck, M. Ilchen, B. Vodungbo, N. Mahne, C. Svetina, C. Spezzani, S. Di Mitri, G. Penco, M. Trovò, W. Fawley, P. Rebernik, D. Gauthier, C. Grazioli, M. Coreno, B. Ressel, A. Kivimäki, T. Mazza, L. Glaser, F. Scholz, J. Seltmann, P. Gessler, J. Grünert, A. De Fanis, M. Meyer, A. Knie, S. Moeller, L. Raimondi, F. Capotondi, E. Pedersoli, O. Plekan, M. Danailov, A. Demidovich, I. Nikolov, A. Abrami, J. Gautier, J. Lüning, P. Zeitoun, L. Giannessi
FERMI, based at Elettra (Trieste, Italy) is the first free electron laser (FEL) facility operated for user experiments in
seeded mode. Another unique property of FERMI, among other FEL sources, is to allow control of the polarization state
of the radiation. Polarization dependence in the study of the interaction of coherent, high field, short-pulse ionizing
radiation with matter, is a new frontier with potential in a wide range of research areas. The first measurement of the
polarization-state of VUV light from a single-pass FEL was performed at FERMI FEL-1 operated in the 52 nm-26 nm
range. Three different experimental techniques were used. The experiments were carried out at the end-station of two
different beamlines to assess the impact of transport optics and provide polarization data for the end user. In this paper
we summarize the results obtained from different setups. The results are consistent with each other and allow a general
discussion about the viability of permanent diagnostics aimed at monitoring the polarization of FEL pulses.
The SQS scientific instrument at the European XFEL is dedicated to investigations in the soft X-rays regime,
in particular to studies of non-linear and ultrafast processes in atoms, molecules and clusters using a variety of
spectroscopic techniques. It will be equipped with a Kirkpatrick-Baez (KB) adaptive mirror system enabling
submicron focusing and access to variable focal distances. In this paper we describe the conceptual design of the
beam transport and focusing layout based on the KB system. The design includes a study of feasibility based
on the comparison between the required source and image positions and the theoretical limits for the accessible
mirror profiles.
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