Beamline Description

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Kirkpatrick-Baez (KB) focusing mirrors

The K-B optical system has nominal focal lengths of 1750 mm (vertical) and 1200 mm (horizontal) and is designed to focus the FEL beam to a spot size of approximately 5×6 µm2 Full Width Half Maximum (FWHM) for FEL-1 and of 4×5 µm2 FWHM for FEL-2 under the ideal condition of a pure Gaussian illumination (Raimondi et al. 2013). However, due to the relatively large beam divergence of FEL-1 and non-ideal emission from the source of transversal modes, the minimum achieved spot size for FEL-1 is about 10×10 µm2. The active nature of the optical focusing system also allows varying the spot shape and size, in order to meet the user requirements, e.g. for uniform illumination of larger samples.  		Layout of the focusing optics

Focus size and shape

Indentation on PMMA produced by the focused beam Size and shape of the focus can be reconstructed by a wave front sensor and measured making indentations impinging with the FEL beam on a PMMA film. Wave front sensor reconstruction and optical microscope analysis confirmed that the current system provides a spot smaller than 10 x 10 μm2.
Ultima modifica il Mercoledì, 16 Ottobre 2019 12:13