Development of an high gradient, S-band, accelerating structure for the FERMI linac

The FERMI seeded free-electron laser (FEL), located at the Elettra laboratory in Trieste, is driven by a 200 meter long, S-band linac routinely operated at nearly 1.5 GeV and 10 Hz repetition rate [1]. The high energy part of the Linac is equipped with seven, 6 meter long Backward Traveling Wave (BTW) structures: those structures have small iris radius and a nose cone geometry which allows for high gradient operation [2]. Nonetheless a possible development of high-gradient, S-band accelerating struc-tures for the replacement of the actual BTW structures is under consideration. This paper investigates a possible solution for RF couplers that could be suitable for linac driven FEL where reduced wakefields effects, high operating gradient and very high reliability are required

Design of Front End and a 3-Pole-Wiggler as a Photon Source for BEATS Beamline at SESAME

International audienceBEATS is an international collaboration funded by EU in order to design and implement an XR tomography beam line in SESAME Jordanian synchrotron. ALBA contribution consists in the design of the photon source and the Front End elements. In this paper we present the conceptual designs of both the 3-pole wiggler uses as photon source as well as the Front End elements designed for the beamline

Design and Ray-Tracing of the BEATS Beamline of SESAME

International audienceThe BEAmline for Tomography at SESAME (BEATS) will operate an X-rayμtomography station providing service to scientists from archaeology, cultural heritage, medicine, biology, material science and engineering, geology and environmental sciences*. BEATS will have a length of 45 m with a 3-pole-wiggler source (3 T peak magnetic field at 11 mm gap). Filtered white and monochromatic beam (8 keV to 50 keV, dE/E: 2% to 3% using a double-multilayer-monochromator) modalities will be available. In this work we present the beamline optical design, verified with simulation tools included in OASYS**. The calculated flux through 1 mm² at the sample position will be as high as 8.5×10⁹ Ph/s/mm² in 0.1% of the source bandwidth, for a maximum usable beam size of 70×15 mm². Beam transverse coherence will be limited to below 1 µm by the horizontal size of the X-ray source (~2 mm FWHM). For phase contrast applications requiring enhanced coherence, front end slits can be closed to 0.5 mm horizontally, with a reduction of the available beam size and photon flux. The BEATS beamline will fulfill the needs of the tomography community of SESAME

Chirped pulse amplification in an extreme-ultraviolet free-electron laser

International audienceChirped pulse amplification in optical lasers is a revolutionary technique, which allows the generation of extremely powerful femtosecond pulses in the infrared and visible spectral ranges. Such pulses are nowadays an indispensable tool for a myriad of applications, both in fundamental and applied research. In recent years, a strong need emerged for light sources producing ultra-short and intense laser-like X-ray pulses, to be used for experiments in a variety of disciplines, ranging from physics and chemistry to biology and material sciences. This demand was satisfied by the advent of short-wavelength free-electron lasers. However, for any given free-electron laser setup, a limit presently exists in the generation of ultra-short pulses carrying substantial energy. Here we present the experimental implementation of chirped pulse amplification on a seeded free-electron laser in the extreme-ultraviolet, paving the way to the generation of fully coherent sub-femtosecond gigawatt pulses in the water window (2.3-4.4 nm)

The FERMI seeded-FEL facility: Status and perspectives

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Coherent soft X-ray pulses from an echo-enabled harmonic generation free-electron laser

International audienceX-ray free-electron lasers (FELs), which amplify light emitted by a relativistic electron beam, are extending nonlinear optical techniques to shorter wavelengths, adding element specificity by exciting and probing electronic transitions from core levels. These techniques would benefit tremendously from having a stable FEL source, generating spectrally pure and wavelength-tunable pulses. We show that such requirements can be met by operating the FEL in the so-called echo-enabled harmonic generation (EEHG) configuration. Here, two external conventional lasers are used to precisely tailor the longitudinal phase space of the electron beam before emission of X-rays. We demonstrate high-gain EEHG lasing producing stable, intense, nearly fully coherent pulses at wavelengths as short as 5.9 nm (~211 eV) at the FERMI FEL user facility. Low sensitivity to electron-beam imperfections and observation of stable, narrow-band, coherent emission down to 2.6 nm (~474 eV) make the technique a prime candidate for generating laser-like pulses in the X-ray spectral region, opening the door to multidimensional coherent spectroscopies at short wavelengths

First Lasing of a Free Electron Laser in the Soft X-Ray Spectral Range with Echo Enabled Harmonic Generation

International audienceWe report on the successful operation of a Free Electron Laser (FEL) in the Echo Enabled Harmonic Generation (EEHG) scheme at the FERMI facility at Sincrotrone Trieste. The experiment required a modification of the FEL-2 undulator line which, in normal operation, uses two stages of high-gain harmonic generation separated by a delay line. In addition to a new seed laser, the dispersion in the delay-line was increased, the second stage modulator changed and a new manipulator installed in the delay-line chicane hosting additional diagnostic components. With this modified setup we have demonstrated the first evidence of strong exponential gain in a free electron laser operated in EEHG mode at wavelengths as short as 5 nm