Focusing properties of linear undulators

Quattromini, M.; Artioli, M.; Palma, E. Di; Petralia, A.; Giannessi, L.

doi:10.1103/physrevstab.15.080704

Cited by 31 publications

(27 citation statements)

References 12 publications

(17 reference statements)

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“…Subsequently, the electron beam was injected into the undulator system, consisting of six sections of 75 periods, with u ¼ 2:8 cm [40]. The optimum matching condition of the electron beam to the undulator was found by using the average values of energy and projected Twiss parameters.…”

Section: H Y S I C a L R E V I E W L E T T E R S Week Ending 13 Septementioning

confidence: 99%

Observation of Time-Domain Modulation of Free-Electron-Laser Pulses by Multipeaked Electron-Energy Spectrum

et al. 2013

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We present the experimental demonstration of a new scheme for the generation of ultrashort pulse trains based on free-electron-laser (FEL) emission from a multipeaked electron energy distribution. Two electron beamlets with energy difference larger than the FEL parameter have been generated by illuminating the cathode with two ps-spaced laser pulses, followed by a rotation of the longitudinal phase space by velocity bunching in the linac. The resulting self-amplified spontaneous emission FEL radiation, measured through frequency-resolved optical gating diagnostics, reveals a double-peaked spectrum and a temporally modulated pulse structure. DOI: 10.1103/PhysRevLett.111.114802 PACS numbers: 41.60.Cr, 42.55.Àf, 42.65.Ky Radiation pulses with attosecond to femtosecond time scales represent a real possibility for a breakthrough in science and technology, permitting unprecedented insights into the ultrafast electron and nuclear dynamics [1][2][3]. The time-resolved study of electron rearrangements could lead to significant advances in the understanding of intermolecular processes, chemical bond breaking and formation, and the interaction of photoactivated molecules with their environment.Trains of ultrashort radiation pulses enable stroboscopic electron imaging [4] and the investigation of the response accompanying collective electron motion in nanomaterials [5]. They also find further applications in other technical fields, such as the enhancement of transmission or reflectivity in materials, resonant inelastic x-ray scattering, or the ab initio phasing of nanocrystals [6].Sequences of spikes have been synthesized by means of the high harmonic generation driven by lasers in gases [7] and regularly used in experiments [4,8], but are severely limited in efficiency approaching the keV range.Free-electron lasers (FELs) are capable of producing high brightness pulses in the x-ray spectral region [9][10][11][12]. The FEL, in the self-amplified spontaneous emission (SASE) mode of operation [13], generates radiation with limited temporal coherence [14], time duration of the order of the electron bunch length and structured in a chaotic succession of random peaks. The typical time scale of these radiation spikes is set by the FEL Pierce parameter [13]. Several techniques have been explored to increase longitudinal coherence, stability, and/or to shorten the FEL pulse time scale towards the attosecond domain. The amplification of one single SASE spike has been demonstrated by compressing the electron beam close or below the FEL coherence length [15,16], by using a chirped bunch energy combined with a matched undulator taper [17][18][19], or by spoiling the whole electron beam except a limited fraction [20,21], a technique that has also been implemented to produce double pulse two-color radiation for pump and probe experiments [22]. Short single or multiple pulses have also been produced in seeded or cascaded FELs [23][24][25][26][27], with increased coherence and shot to shot stability. More sophisticated seeding concept...

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Section: H Y S I C a L R E V I E W L E T T E R S Week Ending 13 Septementioning

confidence: 99%

Observation of Time-Domain Modulation of Free-Electron-Laser Pulses by Multipeaked Electron-Energy Spectrum

et al. 2013

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“…MeV (corresponding to an electron Lorentz factor γ≈335 and then matched to the undulator system (6 sections, with movable gaps, of 75 periods λ = 2.8 cm) [30]. The undulator was tuned at the resonant wavelength Table 1.…”

Section: Experimental Set Upmentioning

confidence: 99%

Mapping the transverse coherence of the self amplified spontaneous emission of a free-electron laser with the heterodyne speckle method

Alaimo¹,

Anania²,

Artioli³

et al. 2014

Opt. Express

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Abstract:The two-dimensional single shot transverse coherence of the Self-Amplified Spontaneous Emission of the SPARC_LAB Free-Electron Laser was measured through the statistical analysis of a speckle field produced by heterodyning the radiation beam with a huge number of reference waves, scattered by a suspension of particles. In this paper we report the measurements and the evaluation of the transverse coherence along the SPARC_LAB undulator modules. The measure method was demonstrated to be precise and robust, it does not require any a priori assumptions and can be implemented over a wide range of wavelengths, from the optical radiation to the x-rays. Science 316(5830), 1444-1448 (2007). 11. R. Bonifacio, C. Pellegrini, and L. M. Narducci, "Collective instabilities and high-gain regime in a free electron laser," Opt. Commun. 50(6), 373-378 (1984). 12. E. L. Saldin, E. A. Schneidmiller, and M. V. Yurkov, "Statistical properties of radiation from VUV and X-ray free electron laser," Opt. Commun. 148(4-6), 383-403 (1998 33. E. L. Saldin, E. A. Schneidmiller, and M. V. Yurkov, "Output power and degree of transverse coherence of Xray free electron lasers," Opt.

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“…The electron beam was then injected in the undulator system, consisting of six modules of 75 periods each, with λ u ¼ 2.8 cm [21], tuned at the resonant wavelength…”

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confidence: 99%

Two-Color Radiation Generated in a Seeded Free-Electron Laser with Two Electron Beams

et al. 2015

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We present the experimental evidence of the generation of coherent and statistically stable two-color free-electron laser radiation obtained by seeding an electron beam double peaked in energy with a laser pulse single spiked in frequency. The radiation presents two neat spectral lines, with time delay, frequency separation, and relative intensity that can be accurately controlled. The analysis of the emitted radiation shows a temporal coherence and a shot-to-shot regularity in frequency significantly enhanced with respect to the self-amplified spontaneous emission. DOI: 10.1103/PhysRevLett.115.014801 PACS numbers: 41.60.Cr, 41.50.+h, 42.55.Vc Two-color radiation enables a wide number of new experiments, ranging from time-resolved analysis of the atomic, surface, and plasma dynamics to the imaging of biomedical samples and molecules. Studies on dual frequency production on free-electron lasers (FELs) have been recently carried on with different methods [1][2][3][4][5] in various frequency regimes, while, at the same time, several promising theoretical proposals have been investigated, aimed at generating two-color FEL emission in the x-ray wavelength range [6][7][8][9]. A particularly powerful method for producing two-color radiation is the double electron bunch operation that has been implemented and demonstrated in the visible [2,10,11] and in the x-ray [5] domains, in this latter case with applications on experiments with external users. This scheme is based on two closely spaced electron beamlets generated at the cathode and accelerated off crest along the linac to two different energies. The bunch train, driven in the undulator, radiates two distinct self-amplified spontaneous emission (SASE) pulses, whose relative time delay and wavelength difference can be tuned independently by changing the extraction conditions from the linac. The particular advantage of this approach is the large spectral separation, up to 1-2% [10], that can be achieved and the possibility of using the entire undulator length on both colors, thus allowing applications requiring high-intensity radiation or exploiting the activation of self-seeding processes. In all these previous experiments, the emission starts from noise and, whereas the two colors can be single spiked, the radiation is affected by random shot-to-shot fluctuations both in the time and frequency domains and presents, therefore, poor longitudinal coherence. The degree of coherence can be improved by seeding the radiation with a temporally coherent external field. This technique covers directly all the radiation frequencies where coherent sources are available. In particular, atomic lasers can be used to seed radiation in their range of operation. The use of the laser harmonics extends this method to ultraviolet [12], while the combination of high-gain harmonics generation (HGHG) with multistage cascade schemes permits to reach, at the status of the art, the water window [13].In this Letter, we present an experimental demonstration of the operation with a seed, sing...

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Focusing properties of linear undulators

Cited by 31 publications

References 12 publications

Observation of Time-Domain Modulation of Free-Electron-Laser Pulses by Multipeaked Electron-Energy Spectrum

Observation of Time-Domain Modulation of Free-Electron-Laser Pulses by Multipeaked Electron-Energy Spectrum

Mapping the transverse coherence of the self amplified spontaneous emission of a free-electron laser with the heterodyne speckle method

Two-Color Radiation Generated in a Seeded Free-Electron Laser with Two Electron Beams

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