121 research outputs found
Knot undulator to generate linearly polarized photons with low on-axis power density
Heat load on beamline optics is a serious problem to generate pure linearly
polarized photons in the third generation synchrotron radiation facilities. For
permanent magnet undulators, this problem can be overcome by a figure-8
operating mode. But there is still no good method to tackle this problem for
electromagnetic elliptical undulators. Here, a novel operating mode is
suggested, which can generate pure linearly polarized photons with very low
on-axis heat load. Also the available minimum photon energy of linearly
polarized photons can be extended much by this method
Bridging the gap of storage ring light sources and linac-driven free-electron lasers
High-gain free-electron lasers (FELs) are driven by short, high-charge density electron beams as only produced at dedicated single pass or recirculating linear accelerators. We describe new conceptual, technical, and modeling solutions to produce subpicosecond, up to 100 \u3bcJ energy extreme ultra-violet and soft x-ray FEL pulses at high- and tunable repetition rates, from diffraction-limited storage ring light source. In contrast to previously proposed schemes, we show that lasing can be simultaneous to the standard multibunch radiation emission from short insertion devices, and that it can be obtained with limited impact on the storage ring infrastructure. By virtue of the high-average power but moderate pulse energy, the storage ring-driven high-gain FEL would open the door to unprecedented accuracy in time-resolved spectroscopic analysis of matter in the linear response regime, in addition to inelastic scattering experiments
VUV and X-ray coherent light with tunable polarization from single-pass free-electron lasers
Tunable polarization over a wide spectral range is a required feature of
light sources employed to investigate the properties of local symmetry in both
condensed and low-density matter. Among new-generation sources, free-electron
lasers possess a unique combination of very attractive features, as they allow
to generate powerful and coherent ultra-short optical pulses in the VUV and
X-ray spectral range. However, the question remains open about the possibility
to freely vary the light polarization of a free-electron laser, when the latter
is operated in the so-called nonlinear harmonic-generation regime. In such
configuration, one collects the harmonics of the free-electron laser
fundamental emission, gaining access to the shortest possible wavelengths the
device can generate. In this letter we provide the first experimental
characterization of the polarization of the harmonic light produced by a
free-electron laser and we demonstrate a method to obtain tunable polarization
in the VUV and X-ray spectral range. Experimental results are successfully
compared to those obtained using a theoretical model based on the paraxial
solution of Maxwell's equations. Our findings can be expected to have a deep
impact on the design and realization of experiments requiring full control of
light polarization to explore the symmetry properties of matter samples
OPENMODS 2.0 âInstrument Jamming Meetingâ report
Major achievements
The feedback provided by potential users on their needs was very much appreciated. They
underlined the importance of having:
â an easy to deploy instrument (i.e.: from small fishing boats);
â multi-parameter sensors in ONE device;
â less maintenance effort
and prioritized the variables to measure.
Although, there are technical limitations and different solutions and there is no one tool that
can do everything, which is low cost, has high resolution and low maintenance, the
outcomes of the platforms/sensors/communications working group meet the main
requirements that emerged.
Priority was given to:
â a platform that will operate in drifter mode which is extremely easy to deploy and
perfect for studies associated with search and rescue operations (another need that
has emerged). It also constantly guarantees the knowledge of the instrument position.
The platform can be easily converted into the moored mode.
â temperature and pressure sensors. The sensors will be low -cost with the idea to
replace them rather than calibrate them;
â LoRaWAN communications preferably with Bluetooth integration for the in-situ
download of the data
Tunability experiments at the FERMI@Elettra free-electron laser
FERMI@Elettra is a free electron-laser (FEL)-based user facility that, after two years of commissioning, started preliminary users' dedicated runs in 2011. At variance with other FEL user facilities, FERMI@Elettra has been designed to deliver improved spectral stability and longitudinal coherence. The adopted scheme, which uses an external laser to initiate the FEL process, has been demonstrated to be capable of generating FEL pulses close to the Fourier transform limit. We report on the first instance of FEL wavelength tuning, both in a narrow and in a large spectral range (fine- and coarse-tuning). We also report on two different experiments that have been performed exploiting such FEL tuning. We used fine-tuning to scan across the 1sâ4p resonance in He atoms, at â23.74 eV (52.2 nm), detecting both UVâvisible fluorescence (4pâ2s, 400 nm) and EUV fluorescence (4pâ1s, 52.2 nm). We used coarse-tuning to scan the M4,5 absorption edge of Ge (âŒ29.5 eV) in the wavelength region 30â60 nm, measured in transmission geometry with a thermopile positioned on the rear side of a Ge thin foil
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