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- Pop, Mihai, et al.
(author)
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Mitigation of CSR induced spectral broadening in EEHG FEL
- 2023
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In: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 1048
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Journal article (peer-reviewed)abstract
- Externally seeded schemes have offered a major leap in improving the longitudinal coherence of FELs in the EUV and soft X-ray range. The Echo Enabled Harmonic Generation (EEHG) technique creates bunching at wavelengths of a few nanometers in two stages of longitudinal phase space manipulation, each consisting of an energy modulator and a chicane. Compared to other seeding techniques, EEHG is less sensitive to electron beam phase space distortions occurring during acceleration and compression. However the strong chicane needed in the first stage makes the system vulnerable to Coherent Synchrotron Radiation (CSR), which imprints a long-wavelength energy modulation on the electron bunch after the EEHG process has been initiated. Coupled with the second dispersive section, this modulation creates a position dependent change in the final bunching wavelength. In this work we show that tailoring the second seed laser wavelength can successfully compensate for the varying energy profile induced by CSR.
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- Pop, Mihai, et al.
(author)
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Single-shot transverse coherence in seeded and unseeded free-electron lasers: A comparison
- 2022
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In: Physical Review Accelerators and Beams. - 2469-9888. ; 25:040701
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Journal article (peer-reviewed)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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- Qin, Weilun, et al.
(author)
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The FEL in the SXL project at MAX IV
- 2021
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In: Journal of Synchrotron Radiation. - : International Union Of Crystallography. - 1600-5775 .- 0909-0495. ; 28, s. 707-717
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Journal article (peer-reviewed)abstract
- In this paper the design of the free-electron laser (FEL) in the SXL (Soft X-ray Laser) project at the MAX IV Laboratory is presented. The target performance parameters originate in a science case put forward by Swedish users and the SXL FEL is foreseen to be driven by the existing MAX IV 3 GeV linac. The SXL project is planned to be realized in different stages and in this paper the focus is on Phase 1, where the basic operation mode for the FEL will be SASE (self-amplified spontaneous emission), with an emphasis on short pulses. Simulation results for two linac bunches (high and low charge) with different pulse duration are illustrated, as well as the performance for two-color/two-pulses mode and power enhancement through tapering. Besides standard SASE and optical klystron configurations, the FEL setup is also tailored to allow for advanced seeding schemes operations. Finally possible upgrades that will be implemented in a second phase of the project are discussed.
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