First Ultraviolet High-Gain Harmonic-Generation Free-Electron Laser

Yu, Lihua; DiMauro, Louis F.; Doyuran, A.; Graves, W.; Johnson, E.; Heese, R.; Krinsky, S.; Loos, H.; Murphy, J.B.; Rakowsky, G.; Rose, J.; Shaftan, T.; Sheehy, B.; Skaritka, J.; Wang, X. J.

doi:10.1103/physrevlett.91.074801

Cited by 184 publications

(63 citation statements)

References 16 publications

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“…The seed transfers its longitudinal coherence properties to the FEL pulse [8], and schemes based on this principle were proposed to improve the longitudinal coherence of FELs operating in a self amplified spontaneous emission mode [9][10][11], where the temporal pulse structure is dominated by stochastic fluctuations associated with the initial shot noise [12]. The seed amplification, combined with the generation of coherent harmonics, has been demonstrated first in the midinfrared [8,13] and then in the UV-VUV range [14][15][16][17]. User facilities based on the frequency up-conversion of a seed laser in the VUV soft-x-ray region of the spectrum are now in operation and provide radiation with unprecedented properties of longitudinal coherence [18].…”

mentioning

confidence: 99%

High-Order-Harmonic Generation and Superradiance in a Seeded Free-Electron Laser

Giannessi¹,

Artioli²,

Bellaveglia³

et al. 2012

Phys. Rev. Lett.

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Higher order harmonic generation in a free-electron laser amplifier operating in the superradiant regime [R. H. Dicke, Phys. Rev. 93, 99 (1954).] has been observed. Superradiance has been induced by seeding a single-pass amplifier with the second harmonic of a Ti:sapphire laser, generated in a -Barium borate crystal, at seed intensities comparable to the free-electron laser saturation intensity. Pulse energy and spectral distributions of the harmonics up to the 11th order have been measured and compared with simulations. DOI: 10.1103/PhysRevLett.108.164801 PACS numbers: 41.60.Cr, 41.50.+h, 42.55.Vc Nonlinear harmonic generation is widely used to extend the operation of optical lasers to the UV-vacuum ultra violet (UV-VUV) spectral region, where research methods for the investigation of matter [1-4] require ultrashort coherent pulses. Frequency up-conversion to the 10-100 nm range may be accomplished with high harmonics generated in gas (HHG) [5,6], where the active medium is a low density noble gas. The emission of high-energy photons, however, is inherently coupled with ionization, and the use of a nonlinear optical medium poses limitations to the conversion efficiency at the shortest wavelengths. In the spectral region where ionization processes are dominant, harmonic generation may still be obtained in freeelectron lasers (FELs). The mechanism of frequency up-conversion is based on the nonlinear density modulation of an electron beam at a given seed wavelength, seed . The frequency components of the modulated beam enforce the collective emission process at the resonant wavelength r ¼ u ð1 þ K 2 =2Þ=2 2 % seed and its harmonics [ is the Lorentz factor of the electrons, u is the period, and K ¼ eB u u =ð2 m e cÞ is the deflection parameter of the undulator] [7]. The seed transfers its longitudinal coherence properties to the FEL pulse [8], and schemes based on this principle were proposed to improve the longitudinal coherence of FELs operating in a self amplified spontaneous emission mode [9][10][11], where the temporal pulse structure is dominated by stochastic fluctuations associated with the initial shot noise [12]. The seed amplification, combined with the generation of coherent harmonics, has been demonstrated first in the midinfrared [8,13] and then in the UV-VUV range [14][15][16][17]. User facilities based on the frequency up-conversion of a seed laser in the VUV soft-x-ray region of the spectrum are now in operation and provide radiation with unprecedented properties of longitudinal coherence [18]. Coherent harmonics have been observed when seeding a single-pass FEL amplifier, and include the 3rd, 5th [19], and 7th harmonics [20]. The process of harmonic generation is expected to extend to higher orders when the FEL operates in the regime of super-radiance [21], in which a short optical pulse slips over the electron beam and increases its energy while maintaining a self-similar shape [22,23]. In this regime, the radiation pulse has a peak power that increases with the square of the distance z along...

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confidence: 99%

High-Order-Harmonic Generation and Superradiance in a Seeded Free-Electron Laser

Giannessi¹,

Artioli²,

Bellaveglia³

et al. 2012

Phys. Rev. Lett.

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“…The process is similar to that of high-gain harmonic generation (HGHG) demonstrated at the DUV FEL [21,40,41]. One, two, and three-stage harmonic cascade FELs are shown in the return straights in Figure 1.…”

Section: Photon Production and X-ray Beamlinesmentioning

confidence: 66%

LUX: a design study for a linac-/laser-based ultrafast x-ray source

et al. 2004

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We describe the design concepts for a potential future source of femtosecond x-ray pulses based on synchrotron radiation production in a recirculating electron linac. Using harmonic cascade free-electron lasers (FEL's) and spontaneous emission in short-period, narrow-gap insertion devices, a broad range of photon energies are available with tunability from EUV to hard x-ray regimes. Photon pulse durations are controllable and range from 10 fs to 200 fs, with fluxes 10 7 -10 12 photons per pulse. Full spatial and temporal coherence is obtained for EUV and soft X-rays. A fiber laser master oscillator and stabilized timing distribution scheme are proposed to synchronize accelerator rf systems and multiple lasers throughout the facility, allowing timing synchronization between sample excitation and X-ray probe of approximately 20-50 fs.

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“…The FEL pulse duration is typically specified by users in facilities relying on SASE, whilst its lower-limit is set by the duration of the external seed laser, such as in High Gain Harmonic Generation (HGHG) schemes [10,15,16,[33][34][35][36][37]. In both cases, the electron bunch duration at the undulator should be longer than the required FEL pulse duration because of effects such as FEL slippage in SASE FELs, arrival time jitter, and multi-stage cascade in HGHG FELs.…”

Section: Pulse Length-driven Approachmentioning

confidence: 99%

On the Importance of Electron Beam Brightness in High Gain Free Electron Lasers

Mitri

2015

Photonics

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Linear accelerators delivering high brightness electron beams are essential for driving short wavelength, high gain free-electron lasers (FELs). The FEL radiation output efficiency is often parametrized through the power gain length that relates FEL performance to electron beam quality at the undulator. In this review article we illustrate some approaches to the preliminary design of FEL linac-drivers, and analyze the relationship between the output FEL wavelength, exponential gain length and electron beam brightness. We extend the discussion to include FEL three-dimensional effects and electron beam projected emittances. Although mostly concentrating on FELs based upon self-amplified spontaneous emission (SASE), our findings are in some cases highly relevant to externally seeded FELs.

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First Ultraviolet High-Gain Harmonic-Generation Free-Electron Laser

Cited by 184 publications

References 16 publications

High-Order-Harmonic Generation and Superradiance in a Seeded Free-Electron Laser

High-Order-Harmonic Generation and Superradiance in a Seeded Free-Electron Laser

LUX: a design study for a linac-/laser-based ultrafast x-ray source

On the Importance of Electron Beam Brightness in High Gain Free Electron Lasers

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