DiProI beamline at FERMI@Elettra

The lensless Coherent Diffraction Imaging (CDI) technique has been developed significantly and is gaining time resolved potentials thanks to the advent of coherent and ultrashort pulses delivered by the X-ray free electron lasers (FEL). The shot-to-shot temporal and energy stability of the seeded-FEL pulses at Fermi@Elettra has opened extraordinary opportunities for CDI and in particular for Resonant Coherent Diffraction Imaging (R-CDI ),  overcoming some of the limitations imposed by the partial longitudinal coherence of the SASE-FELs.In addition, the multiple (linear and circular) polarization of Fermi-FEL pulses is an added value to explore specific contrast mechanisms, relevant to the spin and orbital sensitive electronic transitions.

Multi-color magnetic imaging

Nanoscale magnetic domain networks in Co/Pt heterostructure are spatially resolved through coherent imaging with Fourier-transform holography. Irradiating the holographic sample at the same time with two harmonics of the FEL seed, at resonance with O and Pt respectively, two element specific images are retrieved at the same time.

Willems et al., Structural Dynamics, 4, 014301 (2017).

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Mini-TIMER: four wave mixing with FEL transient gratings

Extreme ultraviolet four wave mixing have been demonstrated at the DiProI beamline producing a transient grating with 70 fs FEL pulses, split into two halves and recombined on the sample with a known delay, and probing it with a 100 fs ultraviolet pulse to produce a fourth signal beam.

Bencivenga et al., Nature 520, 205 (2015).

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Ultrafast demagnetization dynamics

When an ultrashort optical laser pulse excites a magnetic material, it responds with an almost instantaneous reduction of its magnetization, followed by a slower recovery. This dynamics can be followed by time resolved magnetic holography, taking FEL images of samples excited by IR pulses.

von Korff Schmising et al., Physical Review Letters 112, 217203 (2014).

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Holography with customizable reference

Fourier transform holography retrieves microscopic images encoding in the X-ray scattered wave the interference between a known reference and the sample. The presented algorithm allows reconstruction from customizable references that can be designed in order to optimize signal from each particular sample, overcoming the limitations of standard holography geometries.

Martin et al., Nature Communications 5, 4661 (2014).

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Pump-probe with twin-seeded two-color FEL

The time resolved dynamics of matter under extreme non-equilibrium conditions can be studied by pumping the sample with an intense ultrafast X-ray pulse and probing the system response with a second FEL pulse after a known delay.

Allaria et al., Nature Communications 4, 2476 (2013).

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Sorting CDI movie frames

One of the main goals of CDI is to create single shot images of identical objects, captured at different times during an undergoing transformation. These "frames" must be sorted in the right order to obtain the "movie" of the dynamic process.

Yoon et al., Optics Express 22, 8085 (2014).

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Magnetic resonant holography

Cobalt/palladium multilayers present magnetic domains, with opposite polarizations perpendicular to the surface, that can be prepared in a disordered maze state. The electron density of the system is uniform, but the magnetic structure can be investigated by photon scattering, which depends on light polarization.

Müller et al., Synchrotron Radiation News 26, 27–32 (2013).

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Towards jitter-free time-resolved FEL-IR experiments

Synchronization of FELs and external IR lasers opens the possibility to investigate ultrafast electron dynamics. The seeded scheme of FERMI allows to couple FEL and IR laser pulses with an unprecedented time jitter as low as 6 fs on the sample.

Danailov et al., Optics Express 22, 12869 (2014).

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FEL-induced ultrafast IR reflectivity change

A FEL pulse impinging on a target interacts with its electrons, promoting in a few femtoseconds a large amount of them from their equilibrium states to higher energy bands, before thermalization and recombination bring the system back to equilibrium in a nanosecond time scale.

Casolari et al., Applied Physics Letters 104, 191104 (2014).

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Last Updated on Monday, 18 January 2016 13:19