Microfocusing of the FERMI@Elettra FEL beam with a K–B active optics system: Spot size predictions by application of the WISE code

Raimondi, Lorenzo; Svetina, Cristian; Mahne, Nicola; Cocco, Daniele; Abrami, A.; Marco, Massimo De; Fava, C.; Gerusina, Simone; Gobessi, R.; Capotondi, Flavio; Pedersoli, Emanuele; Кискинова, М.; Ninno, G. De; Zeitoun, Philippe; Dovillaire, Guillaume; Lambert, Guillaume; Boutu, Willem; Merdji, H.; Gonzalez, A. I.; Gauthier, David; Zangrando, Marco

doi:10.1016/j.nima.2012.11.039

Cited by 53 publications

(42 citation statements)

References 10 publications

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“…of the 'profile error' z e ðxÞ. A similar argument based on physical optics can be used to reach the same conclusion (Raimondi & Spiga, 2015). Clearly, there is no unique mirror z e ðxÞ that returns an assigned PSF; rather, infinite possible profile errors can be associated with a specified PSF form.…”

Section: Introductionmentioning

confidence: 70%

“…In this paper, we re-derive our previous results in the framework of the more general treatment of physical optics (x2), in the frequent case of small values and for Gaussian intensity wavefronts, typical of FELs in the fundamental propagation mode (Raimondi et al, 2013). This not only makes us understand to which approximation the beam-shaping formulae are valid but also offers the opportunity to check the real beam-shaping performances accounting for the coherence of the incident wavefront, which automatically contains all the information regarding the source profile.…”

Section: Introductionmentioning

confidence: 97%

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X-ray beam-shapingviadeformable mirrors: surface profile and point spread function computation for Gaussian beams using physical optics

Spiga

2018

J Synchrotron Radiat

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X-ray mirrors with high focusing performances are commonly used in different sectors of science, such as X-ray astronomy, medical imaging and synchrotron/ free-electron laser beamlines. While deformations of the mirror profile may cause degradation of the focus sharpness, a deliberate deformation of the mirror can be made to endow the focus with a desired size and distribution, via piezo actuators. The resulting profile can be characterized with suitable metrology tools and correlated with the expected optical quality via a wavefront propagation code or, sometimes, predicted using geometric optics. In the latter case and for the special class of profile deformations with monotonically increasing derivative, i.e. concave upwards, the point spread function (PSF) can even be predicted analytically. Moreover, under these assumptions, the relation can also be reversed: from the desired PSF the required profile deformation can be computed analytically, avoiding the use of trial-and-error search codes. However, the computation has been so far limited to geometric optics, which entailed some limitations: for example, mirror diffraction effects and the size of the coherent X-ray source were not considered. In this paper, the beam-shaping formalism in the framework of physical optics is reviewed, in the limit of small light wavelengths and in the case of Gaussian intensity wavefronts. Some examples of shaped profiles are also shown, aiming at turning a Gaussian intensity distribution into a top-hat one, and checks of the shaping performances computing the at-wavelength PSF by means of the WISE code are made.

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Section: Introductionmentioning

confidence: 70%

Section: Introductionmentioning

confidence: 97%

X-ray beam-shapingviadeformable mirrors: surface profile and point spread function computation for Gaussian beams using physical optics

Spiga

2018

J Synchrotron Radiat

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“…5 of Raimondi et al (2013). The K-B configuration (Kirkpatrick & Baez, 1948) decouples the horizontal and vertical focusing.…”

Section: Photon Transport Systemmentioning

confidence: 99%

“…The best profiles, i.e. those closest to the nominal elliptical form, have been achieved (Raimondi et al, 2013); their sagittas (distance from the centre of the arc formed by the mirror to the base of the arc) have been measured to be $ 230 mm for the horizontal focusing mirror and $ 160 mm for the vertical focusing mirror. The presence of residual radii of curvature, slope errors and figure errors may cause a variation of the actual focal distance and intensity distribution of the virtual source seen by the K-B focusing system that is discussed in the next section.…”

Section: Optics Characterizationmentioning

confidence: 99%

The Low Density Matter (LDM) beamline at FERMI: optical layout and first commissioning

Svetina

Grazioli

Mahne

et al. 2015

J Synchrotron Radiat

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“…The 32.5-nm wavelength FEL beam was focused with a Kirkpatrick-Baez (KB) mirror system [41] and entered the chamber through a circular aperture of 5 mm diameter in order to reduce the stray radiation coming from the beamline. The focus of the KB optical system was optimized to a spot size of about 25 μm full width at half maximum using scintillator phosphorus screen and indentations on a Poly(methyl methacrylate) coated silicon wafer placed at the sample plane.…”

Section: Instrumentation and Data Collectionmentioning

confidence: 99%

Direct Phasing of Finite Crystals Illuminated with a Free-Electron Laser

et al. 2015

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It has been suggested that the extended intensity profiles surrounding Bragg reflections that arise when a series of finite crystals of varying size and shape are illuminated by the intense, coherent illumination of an x-ray free-electron laser may enable the crystal's unit-cell electron density to be obtained ab initio via wellestablished iterative phasing algorithms. Such a technique could have a significant impact on the field of biological structure determination since it avoids the need for a priori information from similar known structures, multiple measurements near resonant atomic absorption energies, isomorphic derivative crystals, or atomic-resolution data. Here, we demonstrate this phasing technique on diffraction patterns recorded from artificial two-dimensional microcrystals using the seeded soft x-ray free-electron laser FERMI. We show that the technique is effective when the illuminating wavefront has nonuniform phase and amplitude, and when the diffraction intensities cannot be measured uniformly throughout reciprocal space because of a limited signal-to-noise ratio.

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Microfocusing of the FERMI@Elettra FEL beam with a K–B active optics system: Spot size predictions by application of the WISE code

Cited by 53 publications

References 10 publications

X-ray beam-shapingviadeformable mirrors: surface profile and point spread function computation for Gaussian beams using physical optics

X-ray beam-shapingviadeformable mirrors: surface profile and point spread function computation for Gaussian beams using physical optics

The Low Density Matter (LDM) beamline at FERMI: optical layout and first commissioning

Direct Phasing of Finite Crystals Illuminated with a Free-Electron Laser

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