| 1. |
- Allaria, E., et al.
(författare)
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Highly coherent and stable pulses from the FERMI seeded free-electron laser in the extreme ultraviolet
- 2012
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Ingår i: Nature Photonics. - 1749-4885. ; 6:10, s. 699-704
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Tidskriftsartikel (refereegranskat)abstract
- Free-electron lasers (FELs) are promising devices for generating light with laser-like properties in the extreme ultraviolet and X-ray spectral regions. Recently, FELs based on the self-amplified spontaneous emission (SASE) mechanism have allowed major breakthroughs in diffraction and spectroscopy applications, despite the relatively large shot-to-shot intensity and photon-energy fluctuations and the limited longitudinal coherence inherent in the SASE mechanism. Here, we report results on the initial performance of the FERMI seeded FEL, based on the high-gain harmonic generation configuration, in which an external laser is used to initiate the emission process. Emission from the FERMI FEL-1 source occurs in the form of pulses carrying energy of several tens of microjoules per pulse and tunable throughout the 65 to 20 nm wavelength range, with unprecedented shot-to-shot wavelength stability, low-intensity fluctuations, close to transform-limited bandwidth, transverse and longitudinal coherence and full control of polarization.
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| 2. |
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| 3. |
- Mirian, N. S., et al.
(författare)
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Generation and measurement of intense few-femtosecond superradiant extreme-ultraviolet free-electron laser pulses
- 2021
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Ingår i: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 15, s. 523-529
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Tidskriftsartikel (refereegranskat)abstract
- Free-electron lasers producing ultrashort pulses with high peak power promise to extend ultrafast non-linear spectroscopic techniques into the extreme-ultraviolet-X-ray regime. Key aspects are the synchronization between pump and probe, and the control of the pulse properties (duration, intensity and coherence). Externally seeded free-electron lasers produce coherent pulses that can be synchronized with femtosecond accuracy. An important goal is to shorten the pulse duration, but the simple approach of shortening the seed is not sufficient because of the finite-gain bandwidth of the conversion process. An alternative is the amplification of a soliton in a multistage, superradiant cascade: here, we demonstrate the generation of few-femtosecond extreme-ultraviolet pulses, whose duration we measure by autocorrelation. We achieve pulses four times shorter, and with a higher peak power, than in the standard high-gain harmonic generation mode and we prove that the pulse duration matches the Fourier transform limit of the spectral intensity distribution. By amplifying a soliton in a multistage cascade, few-femtosecond extreme-ultraviolet free-electron laser pulses are achieved.
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| 4. |
- Walker, R.P., et al.
(författare)
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The European UV/VUV storage ring FEL at ELETTRA : First operation and future prospects
- 2001
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - 0168-9002. ; 467-468, s. 34-37
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Tidskriftsartikel (refereegranskat)abstract
- A European project to develop the first storage ring free-electron laser on a third-generation synchrotron radiation facility is presented, including a description of the main features, initial performance at 350 and 220 nm and future prospects.
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| 5. |
- Pop, Mihai, et al.
(författare)
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Single-shot transverse coherence in seeded and unseeded free-electron lasers: A comparison
- 2022
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Ingår i: Physical Review Accelerators and Beams. - 2469-9888. ; 25:040701
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Tidskriftsartikel (refereegranskat)abstract
- The advent of x-ray free-electron lasers (FELs) drastically enhanced the capabilities of several analytical techniques, for which the degree of transverse (spatial) coherence of the source is essential. FELs can be operated in self-amplified spontaneous emission (SASE) or seeded configurations, which rely on a qualitatively different initialization of the amplification process leading to light emission. The degree of transverse coherence of SASE and seeded FELs has been characterized in the past, both experimentally and theoretically. However, a direct experimental comparison between the two regimes in similar operating conditions is missing, as well as an accurate study of the sensitivity of transverse coherence to key working parameters. In this paper, we carry out such a comparison, focusing in particular on the evolution of coherence during the light amplification process.
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| 6. |
- Lorusso, A., et al.
(författare)
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Pulsed laser deposition of yttrium photocathode suitable for use in radio-frequency guns
- 2017
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Ingår i: Applied Physics A. - : SPRINGER. - 0947-8396 .- 1432-0630. ; 123:12
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Tidskriftsartikel (refereegranskat)abstract
- Yttrium (Y) thin film was grown by pulsed laser deposition (PLD) on a copper (Cu) polycrystalline substrate. Ex situ morphological and structural characterisations of the circular Y film of 1.2 mu m thickness and 3 mm diameter have shown a very low droplet density on the film surface and a crystalline feature with a preferred orientation along the Y (100) plane. Moreover, Y thin film resulted in being very adherent to the Cu substrate and more scratch resistant than Cu bulk. A twin thin film was deposited also on a Cu backflange of a radio-frequency (RF) gun to test the suitability of the metallic thin film as photocathode. It was observed that the Y-coated photocathode was characterised by a quantum efficiency (QE) higher than that of the Cu bulk photocathode even if the presence of space charge effects didnt allow deriving the absolute maximum value of QE of Y photocathode.
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