@article {EnricoAllaria2014,
	title = {Control of the Polarization of a Vacuum-Ultraviolet, High-Gain, Free-Electron Laser},
	journal = {Physical review. X},
	volume = {4},
	year = {2014},
	pages = {041040},
	publisher = {American Physical Society},
	address = {College Park, Md.},
	abstract = {The two single-pass, externally seeded free-electron lasers (FELs) of the FERMI user facility are designed around Apple-II-type undulators that can operate at arbitrary polarization in the vacuum ultraviolet-to-soft x-ray spectral range. Furthermore, within each FEL tuning range, any output wavelength and polarization can be set in less than a minute of routine operations. We report the first demonstration of the full output polarization capabilities of FERMI FEL-1 in a campaign of experiments where the wavelength and nominal polarization are set to a series of representative values, and the polarization of the emitted intense pulses is thoroughly characterized by three independent instruments and methods, expressly developed for the task. The measured radiation polarization is consistently >90% and is not significantly spoiled by the transport optics; differing, relative transport losses for horizontal and vertical polarization become more prominent at longer wavelengths and lead to a non-negligible ellipticity for an originally circularly polarized state. The results from the different polarimeter setups validate each other, allow a cross-calibration of the instruments, and constitute a benchmark for user experiments.},
	issn = {2160-3308},
	doi = {10.1103/PhysRevX.4.041040},
	author = {Allaria, Enrico and Diviacco, Bruno and Callegari, Carlo and Finetti, Paola and Mahieu, Benoit and Viefhaus, Jens and Zangrando, Marco and De Ninno, Giovanni and Lambert, Guillaume and Ferrari, Eugenio and Buck, Jens and Ilchen, Markus and Vodungbo, Boris and Mahne, Nicola and Svetina, Cristian and Spezzani, Carlo and Di Mitri, Simone and Penco, Giuseppe and Trovò, Mauro and Fawley, William M. and Rebernik, Primoz R. and Gauthier, David and Grazioli, Cesare and Coreno, Marcello and Ressel, Barbara and Kivimaki, Antti and Mazza, Tommaso and Glaser, Leif and Scholz, Frank and Seltmann, Joern and Gessler, Patrick and Grunert, Jan and De Fanis, Alberto and Meyer, Michael and Knie, Andrè and Moeller, Stefan P. and Raimondi, Lorenzo and Capotondi, Flavio and Pedersoli, Emanuele and Plekan, Oksana and Danailov, Miltcho B. and Demidovich, Alexander and Nikolov, Ivaylo and Abrami, Alessandro and Gautier, Julien and Luning, Jan and Zeitoun, Philippe and Giannessi, Luca}
}
