Paper | Title | Page |
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MOA02 | First Lasing of a Free Electron Laser in the Soft X-Ray Spectral Range with Echo Enabled Harmonic Generation | 7 |
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We 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. | ||
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Slides MOA02 [5.133 MB] | |
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-MOA02 | |
About • | paper received ※ 21 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019 | |
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MOC02 |
Microbunching Instability and Laser Heater Usage in Seeded Free-Electron Lasers | |
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Seeded FELs are tremendous coherent sources in the EUV and soft X-rays domain. They are driven by high-quality electron beams produced in linear accelerators. However, spatio-temporal instabilities can develop in the magnetic compressor chicanes degrading the beam quality. The so-called microbunching instability is a major limitation for the generation of coherent pulses in the X-ray domain. Laser-heater systems are nowadays routinely used to control the electron beam energy spread in order to dump this instability. In the last years, there have proven to be also a powerful device to influence the FEL amplification process. We present here several LH usages in FELs with specific examples achieved on seeded FELs such as improving the harmonic up-conversion process in HGHG seeded FEL, generating short FEL pulses or also producing multi-color FEL pulses. We also report on microbunching instability issues and its effect on FEL spectral quality with strategies to benefit from that. Direct observation of the microbunching level in the electron beam remains also an open challenge. Innovative strategies to measure the electron beam and potentially its microbunching will be presented. | ||
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Slides MOC02 [8.713 MB] | |
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MOC03 |
Laser Heater Impact on the Performances of Seeded High Gain FELs | |
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Laser-heater systems have been demonstrated to be an important component for the accelerators that drive high gain free electron laser (FEL) facilities, dramatically improving the performance of such lightsources. They are nowadays routinely used in most of the operating FEL facilities around the world. The improvement is achieved by suppressing the longitudinal microbunching instability via a controllable increase in the slice energy spread. The system has also been extensively used to manipulate the properties of the electron beam e.g., to produce short pulses of radiation, or for multicolor FEL generation. In this contribution we focus on the usage and impact of such system on a seeded FEL facility, with particular focus on the possibility of efficient generation of short wavelength radiation with unexpected power levels. | ||
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TUA03 |
Generation of Sub-Femtosecond X-Ray Pulses at SwissFEL | |
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We report on the first generation of sub-femtosecond hard X-ray FEL pulses at SwissFEL. A few microjoule pulses with a single spike in the frequency domain have been predicted by simulations and then experimentally demonstrated. Ultra-short X-ray pulses are produced by the electron bunch with a specially-tailored current profile and longitudinal phase space. This configuration is achieved by means of an optimized nonlinear compression. Two- and three-stage nonlinear compression schemes are compared in terms of FEL performance and stability. We also discuss different FEL lasing regimes that can be realized depending on the particular configuration of the electron beam and undulator settings. | ||
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Slides TUA03 [1.809 MB] | |
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WEB02 | Wire-Scanners with Sub-Micrometer Resolution: Developments and Measurements | 307 |
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Monitors of the beam transverse profile with ever more demanding spatial resolution and minimal invasivity are required by the FEL community. In order to improve the spatial resolution towards the sub-micrometer limit as well as to decrease the impact on the lasing process, nano-fabricated wire-scanners have been manufactured independently at PSI and FERMI by means of a lithographic technique [1,2]. Experimental tests carried out at SwissFEL at a low emittance demonstrated the capability of such innovative wire-scanner solutions to resolve beam transverse profiles with a size of 400-500 nm without being affected by any resolution limit. Status and outlook of nano-fabricated wire-scanners will be presented.
[1] M. Veronese et al., NIM-A, 891, 32-36, (2018). [2] S. Borrelli et al., Comm. Phys.-Nature, 1, 52 (2018). |
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Slides WEB02 [11.196 MB] | |
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEB02 | |
About • | paper received ※ 24 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019 | |
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WED01 | Experience with Short-Period, Small Gap Undulators at the SwissFEL Aramis Beamline | 564 |
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The SwissFEL Aramis beamline provides hard X-ray FEL radiation down to 1 Angström with 5.8 GeV and short period, 15 mm, in-vacuum undulators (U15). To reach the maximum designed K-value of 1.8 the U15s have to be operated with vacuum gaps down to 3.0 mm. The thirteen-undulator modules are 4 m long and each of them is equipped with a pair of permanent magnet quadrupoles at the two ends, aligned magnetically to the undulator axis. Optical systems and dedicated photon diagnostics are used to check the alignment and improve the K-value calibration. In this talk the main steps of the undulator commissioning will be recalled and a systematic comparison between the magnetic results and the electron and photon based measurements will be reported to highlight achievements and open issues. | ||
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Slides WED01 [13.825 MB] | |
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WED01 | |
About • | paper received ※ 28 August 2019 paper accepted ※ 06 November 2019 issue date ※ 05 November 2019 | |
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THB03 |
Emittance Measurements and Minimization at SwissFEL | |
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The transverse emittance of the electron beam is a fundamental parameter that determines the performance of free-electron-lasers (FELs). In this contribution, we present emittance measurements carried out at SwissFEL, the X-ray FEL facility that recently started to operate at PSI in Switzerland, including a description of our measurement methods and optimization procedures. We obtained slice emittance values at the undulator entrance down to ~200 nm for an electron beam with a charge of 200 pC and an r.m.s. duration of ~30 fs. Furthermore, we achieved slice emittances as low as ~100 nm for 10 pC beams with few femtosecond duration. | ||
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Slides THB03 [6.285 MB] | |
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THP086 | Operation Modes of the SwissFEL Soft X-Ray Beamline Athos | 757 |
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SwissFEL drives the two FEL beamlines Aramis and Athos, a hard and soft X-ray FEL, respectively. The layout of Athos extends from a simple SASE FEL beamline with the addition of delaying chicanes, external seeding and beam manipulation with wakefield sources (dechirper). It reserves also the space for a possible upgrade to self-seeding. This presentation gives an overview on the detailed layout enabling the unique operation modes of the Athos facility. | ||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP086 | |
About • | paper received ※ 23 August 2019 paper accepted ※ 16 September 2019 issue date ※ 05 November 2019 | |
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