Seeded FEL
Paper Title Page
TUB01 Echo-Enabled Harmonic Generation Lasing of the FERMI FEL in the Soft X-Ray Spectral Region 33
 
  • P. Rebernik Ribič
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • P. Rebernik Ribič
    University of Nova Gorica, Nova Gorica, Slovenia
 
  The layout of the FERMI FEL-2 undulator line, normally operated in the two-stage high-gain harmonic generation (HGHG) configuration, was temporarily modified to allow running the FEL in the echo-enabled harmonic generation (EEHG) mode. The EEHG setup produced stable, intense and nearly fully coherent pulses at wavelengths as short as 5.9 nm (211 eV). Comparing the performance to the two-stage HGHG showed that EEHG gives significantly better spectra in terms of the central wavelength stability and bandwidth, especially at high harmonics, where electron-beam imperfections start to play a significant role. Observation of stable, narrow-band, coherent emission down to 2.6 nm (474 eV) indicates the possibility to extend the lasing region to even shorter wavelengths.  
slides icon Slides TUB01 [10.360 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUB01  
About • paper received ※ 21 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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TUB02
Reflection Self-Seeding at SACLA  
 
  • I. Inoue, T. Hara
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
 
  XFEL are widely operated based on the self-amplified spontaneous emission (SASE) scheme, where spontaneous radiation originating from density modulations in the electron beam is amplified along periodic magnetic field in undulators. Although the SASE scheme effectively produces intense X-ray beams, the stochastic starting-up processes cause poor temporal coherence and a broad spectrum. To narrow the bandwidth while keeping high intensity, we have recently developed an efficient seeding scheme at SACLA, called reflection self-seeding; the SASE-XFEL beam in the first-half undulators is monochromatized via Bragg reflection of a silicon channel-cut crystal, and the monochromatic seed is amplified in the remaining undulators. By applying this scheme to SACLA, we succeeded in producing nearly Fourier-transform-limited XFEL pulses, corresponding to an increase of spectral brightness by a factor of six with respect to the SASE-XFEL [1]. In this presentation, I will talk about the concept of the reflection self-seeding and technical details. Also, I will report on the current operation status and future perspectives of the reflection self-seeding at SACLA.
[1] I. Inoue et al., Nature Photonics 13, 319 (2019)
 
slides icon Slides TUB02 [49.922 MB]  
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TUB03
Hard X-Ray Self-Seeding at PAL-XFEL  
 
  • C.-K. Min, M.H. Cho, H. Heo, H.-S. Kang, C. Kim, G. Kim, M.J. Kim, J.H. Ko, D.H. Na, I.H. Nam, B.G. Oh, S.Y. Rah, C.H. Shim, Y.J. Suh, H. Yang
    PAL, Pohang, Kyungbuk, Republic of Korea
  • K. Kim, D. Shu, Yu. Shvyd’ko
    ANL, Lemont, Illinois, USA
 
  A hard X-ray self-seeding utilizing time-delayed forward Bragg diffracted photons from thin diamond crystals has been successfully commissioned in a broad spectral range (3.5~14.4 keV), and will be soon provided to user experiments. In the self-seeded mode, the spectral bandwidth is typically 0.2~0.5 eV FWHM in contrast to SASE mode, in which the spectral bandwidth is around 20 eV. This implies that the seeded FEL can be a single longitudinal mode laser since the number of longitudinal mode is 100~200 in the SASE operation. In this case, the photon number of filtered FEL is expected to be fluctuated 100% from the narrow bandwidth filtering out of random and spiky SASE spectra. We found that our energy stability of electron bunches (10-4) do not degrade much the seeding performance and the large variation of the seeded FEL intensity will be from the seeding probability. The advantages of 30 um thin diamond crystal and diagnostic tool for the self-seeding will be also presented.  
slides icon Slides TUB03 [28.431 MB]  
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TUB04
Generation and Measurement of Intense Few-Femtosecond Superradiant Soft X-Ray Free Electron Laser Pulses  
 
  • S. Spampinati, E. Allaria, L. Badano, C. Callegari, G. De Ninno, M. Di Fraia, S. Di Mitri, L. Giannessi, N. Mahne, M. Manfredda, N.S. Mirian, G. Penco, O. Plekan, K.C. Prince, L. Raimondi, P. Rebernik Ribič, C. Spezzani, M. Trovò, M. Zangrando
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • R. Feifel, R. Squibb
    Uppsala University, Uppsala, Sweden
  • T. Mazza
    EuXFEL, Hamburg, Germany
  • X. Yang
    BNL, Upton, New York, USA
 
  Intense FEL VUV and soft X-ray pulses with a time duration of few fs allows to probe ultrafast, out-of equilibrium dynamics or to pump the sample driving new phase transitions in regimes where uniform heating is not depleted by secondary energy decay channels, such as Auger effect [Principi]. Most of the methods proposed to reduce the FEL pulse duration are based on a manipulation of longitudinal electron beam properties such as emittance, beam current, energy spread, trajectory or optical functions. We present an attractive alternative based on the exploitation of the FEL dynamic process itself, driving the FEL amplifier in saturation and superradiance in a cascade of undulators resonant at higher harmonics of an initial seed. At FERMI we have implemented for the first time a multistage superradiant cascade reaching EUV-soft X-ray wavelengths and producing high-power, stable, FEL pulses with a duration of about 5 fs. We report here the analysis of the configuration used and of the characterization of the radiation produced in this regime.  
slides icon Slides TUB04 [3.300 MB]  
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TUP035 Sensitivity of LCLS Self-Seeded Pedestal Emission to Laser Heater Strength 126
 
  • G. Marcus, D.K. Bohler, Y. Ding, W.M. Fawley, Y. Feng, E. Hemsing, Z. Huang, J. Krzywiński, A.A. Lutman, D.F. Ratner
    SLAC, Menlo Park, California, USA
 
  Measurements of the soft X-ray, self-seeding spectrum at the LCLS free-electron laser generally display a pedestal-like distribution around the central seeded wavelength that degrades the spectral purity. We have investigated the detailed experimental characteristics of this pedestal and found that it is comprised of two separate components: (1) normal SASE whose total strength is nominally insensitive to energy detuning and laser heater (LH) strength; (2) sideband-like emission whose strength positively correlates with that of the amplified seed and negatively with energy detuning and LH strength. We believe this latter, non-SASE component arises from comparatively long wavelength amplitude and phase modulations of the main seeded radiation line. Its shot-to-shot variability and LH sensitivity suggests an origin connected to growth of the longitudinal microbunching instability on the electron beam. Here, we present experimental results taken over a number of shifts that illustrate the above mentioned characteristics.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP035  
About • paper received ※ 28 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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TUP073 High-Repetition-Rate Seeding Schemes Using a Resonator-Amplifier Setup 222
 
  • S. Ackermann, B. Faatz, V. Grattoni, C. Lechner, G. Paraskaki
    DESY, Hamburg, Germany
  • G. Geloni, S. Serkez, T. Tanikawa
    EuXFEL, Schenefeld, Germany
  • W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  The spectral and temporal properties of Free-Electron Lasers (FEL) operating on the basis of self-amplified spontaneous emission (SASE) suffer from the stochastic behavior of the start-up process. Several so-called "seeding"-techniques using external radiation fields to overcome this limitation have been proposed and demonstrated. The external seed is usually generated by demanding, high-power laser systems, which are not available with a sufficient laser pulse energy at the high repetition rates of superconducting FEL facilities. In this contribution we discuss several seeding schemes that lower the requirements for the used laser systems, enabling seeded operation at high repetition rates by the means of a resonator-amplifier setup.  
poster icon Poster TUP073 [0.521 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP073  
About • paper received ※ 06 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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TUP074 FLASH Upgrade for Seeding 226
 
  • V. Grattoni, S. Ackermann, B. Faatz, T. Lang, C. Lechner, M.M. Mohammad Kazemi, G. Paraskaki
    DESY, Hamburg, Germany
  • W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  An upgrade for FLASH, the SASE FEL in Hamburg, is planned after 2020 aiming at fulfilling user requirements like fully coherent, variable polarization, and multi-colour pulses. In this proceeding, we focus on the FLASH1 beamline that will be operated in seeded mode at a high repetition rate. In particular, we will present and discuss the proposed seeding schemes for delivering FEL radiation with wavelengths from 60 down to 4 nm  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP074  
About • paper received ※ 19 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP076 Seeding R&D at sFLASH 230
 
  • C. Lechner, S. Ackermann, R.W. Aßmann, B. Faatz, V. Grattoni, I. Hartl, S.D. Hartwell, R. Ivanov, T. Laarmann, T. Lang, M.M. Mohammad Kazemi, G. Paraskaki, A. Przystawik, J. Zheng
    DESY, Hamburg, Germany
  • A. Azima, H. Biss, M. Drescher, W. Hillert, V. Miltchev, J. Roßbach
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • S. Khan
    DELTA, Dortmund, Germany
 
  Funding: Work supported by Federal Ministry of Education and Research of Germany under contract No. 05K13GU4, 05K13PE3, and 05K16PEA.
Free-electron lasers (FELs) based on the self-amplified spontaneous emission (SASE) principle generate photon pulses with typically poor longitudinal coherence. FEL seeding techniques greatly improve longitudinal coherence by initiating FEL amplification in a controlled way using coherent light pulses. The sFLASH experiment installed at the FEL user facility FLASH at DESY in Hamburg is dedicated to the study of external seeding techniques. In this paper, the layout of the sFLASH seeding experiment is presented and an overview of recent developments is given.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP076  
About • paper received ※ 30 September 2019       paper accepted ※ 17 October 2019       issue date ※ 05 November 2019  
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TUP077 Study of a Seeded Oscillator-Amplifier FEL 234
 
  • G. Paraskaki, S. Ackermann, B. Faatz, V. Grattoni, C. Lechner, M. Mehrjoo
    DESY, Hamburg, Germany
  • G. Geloni, S. Serkez, T. Tanikawa
    EuXFEL, Schenefeld, Germany
  • W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  In recent years, there is interest of the Free-Electron Laser (FEL) community in external-seeding techniques such as the Echo-Enabled Harmonic Generation (EEHG) and the High-Gain Harmonic Generation (HGHG). With these techniques, pulses of an improved temporal coherence are generated, but at the same time, they are limited by the repetition rates that seed lasers can currently offer with the required pulse energies. A big challenge is to combine the advantages of seeding schemes with high repetition rates. For this purpose, we study a combination of an oscillator-amplifier. The modulator in the oscillator is used at a long wavelength to modulate the electron beam and an amplifier is operated to extract the FEL radiation of the desired harmonic. This way we can use a seed laser of 10 Hz in a burst mode and a resonator to feedback the radiation at repetition rates of superconducting accelerators instead of using an external seed at these high-repetition rates. In this contribution, we present simulation results of a seeded oscillator-amplifier FEL in an HGHG scheme.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP077  
About • paper received ※ 19 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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TUP078 Impact of Electron Beam Energy Chirp on Seeded FELs 238
 
  • G. Paraskaki, S. Ackermann, B. Faatz, V. Grattoni, C. Lechner, J. Zemella
    DESY, Hamburg, Germany
  • W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  Seeded FELs enable the generation of fully coherent, transform-limited and high brightness FEL pulses, as the start-up process is driven by an external coherent light pulse. During the design process of such FELs, it is important to choose carefully the electron beam parameters to guarantee high performance. One of those parameters is the electron beam energy chirp. In this contribution, we show simulation results and we discuss how the electron beam energy chirp affects the final spectrum.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP078  
About • paper received ※ 16 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP079 Status of the Hard X-Ray Self-Seeding Setup at the European XFEL 242
 
  • G. Geloni, S. Karabekyan, D. La Civita, L. Samoylova, S. Serkez, R. Shayduk, H. Sinn, V. Sleziona, M. Vannoni, M. Yakopov
    EuXFEL, Schenefeld, Germany
  • J.W.J. Anton, S.P. Kearney, D. Shu
    ANL, Lemont, Illinois, USA
  • V.D. Blank, S. Terentiev
    TISNCM, Troitsk, Russia
  • W. Decking, V. Kocharyan, S. Liu, E. Negodin, E. Saldin, T. Wohlenberg
    DESY, Hamburg, Germany
  • X. Dong
    European X-Ray Free-Electron Laser Facility GmbH, Schelefeld, Germany
 
  A Hard X-Ray Self-Seeding (HXRSS) setup will be soon commissioned at the European XFEL. It relies on a two-chicanes scheme to deal, in particular, with the high pulse repetition rate of the facility. In this contribution we review the physics choices made at the design stage and the expected performance of the setup. We will also focus on the description of the hardware installations made at the SASE2 line of the European XFEL.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP079  
About • paper received ※ 27 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP080 Harmonic Off-Axis Seeding at the DELTA Short-Pulse Source 246
 
  • A. Meyer auf der Heide, B. Büsing, S. Khan, D. Krieg, C. Mai
    DELTA, Dortmund, Germany
 
  Funding: Work supported by the BMBF (05K16PEA, 05K16PEB), MERCUR (Pr-2014-0047), DFG (INST 212/236-1 FUGG) and the state of NRW
At the 1.5-GeV synchrotron light source DELTA operated by the TU Dortmund University, a short-pulse source employs the coherent harmonic generation (CHG) scheme. Here, a laser pulse interacts with a stored electron bunch forming a microbunching structure to generate ultrashort synchrotron light pulses at harmonics of the laser wavelength. As an upgrade of the short-pulse facility, the echo-enabled harmonic generation (EEHG) scheme will be implemented, which requires a second laser-electron interaction to yield much higher harmonics compared to CHG. In a study towards twofold laser seeding, the possibility of seeding at undulator harmonics with a crossing angle between laser and electron beam was investigated.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP080  
About • paper received ※ 20 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP083 Energy Spread Impact on HGHG and EEHG FEL Pulse Energy 250
 
  • S. Spampinati, E. Allaria, L. Giannessi, P. Rebernik Ribič
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • L. Giannessi
    ENEA C.R. Frascati, Frascati (Roma), Italy
  • P. Rebernik Ribič
    University of Nova Gorica, Nova Gorica, Slovenia
 
  VUV and X-ray free electron lasers (FELs) require a very bright electron beam. Seeded FEL harmonic generation is particularly sensible to energy spread and slice energy spread can limit the highest harmonic conversion factor at which coherent radiation can be produced. Different cas-cade schemes can have different sensibility to the slice energy spread. At FERMI we have evaluated the impact of the slice energy spread on the performance of high gain harmonic generation (HGHG) and of echo enable harmonic generation (EEHG) by measuring the FEL pulse energy as function of the electron beam slice energy spread. The measurements were done at different harmon-ics. The slice energy spread was varied trough the laser heater located in the linac that drives FERMI.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP083  
About • paper received ※ 20 August 2019       paper accepted ※ 17 September 2019       issue date ※ 05 November 2019  
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TUP087 Start-to-end Simulations of the Reflection Hard X-Ray Self-Seeding at the SHINE Project 254
 
  • T. Liu, X. Dong, C. Feng
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
 
  The Shanghai high repetition rate XFEL and extreme light Facility (SHINE) project is designed to produce fully coherent X-ray photons covering the photon energy from 3 keV to 25 keV. We have reported our FEL proposal and schemes in the hard X-ray regime which is self-seeding based on the crystal monochromator previously. Comparing to the transmission self-seeding scheme, the reflection one has several advantages and might be the base proposal. Start-to-end (S2E) simulations from the beam generation by Astra, the linac accelerating by Elegant to the FEL simulation by Genesis are performed. In this manuscript, the FEL simulations based on the S2E beam will be presented mainly. The results demonstrate the feasibility of the reflection hard X-ray self-seeding at the SHINE project.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP087  
About • paper received ※ 20 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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TUP088 Numerical Simulations for Generating Fully Coherent Soft X-Ray Free Electron Lasers With Ultra-Short Wavelength 258
 
  • K.S. Zhou, H.X. Deng, B. Liu, D. Wang
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
 
  For the fully coherent, ultra-short and high power soft X-rays are becoming key instruments in many different research fields, such as biology, chemistry or physics. However, it’s hard to generate this kind of advanced light source by the conventional lasers, especially for the soft X-rays with ultra-short wavelength because of no suitable reflectors. The external seeded free electron laser (FEL) is considered as one feasible method. Here, we give an example to generate highly temporal coherent soft X-rays with the wavelength 1 nm by the two-stage cascaded schemes. EEHG scheme is used as the first-stage while the HGHG scheme is used as the second-stage.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP088  
About • paper received ※ 20 August 2019       paper accepted ※ 22 October 2019       issue date ※ 05 November 2019  
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TUP090 Considerations on Implementing EEHG with a Strong Linear Chirp 262
 
  • M.A. Pop, F. Curbis, W. Qin, S. Werin
    MAX IV Laboratory, Lund University, Lund, Sweden
  • F. Curbis, S. Werin
    SLF, Lund, Sweden
  • W. Qin
    Lund University, Lund, Sweden
 
  Funding: The work is supported by Knut and Alice Wallenberg foundation.
The Soft X-ray Laser (SXL) currently being studied at MAX IV Laboratory is envisioned to produce coherent radiation in the 1-5 nm wavelength range. In this contribution, we present the results of simulations aimed at adding to the SXL an Echo Enabled Harmonic Generation scheme, which has been shown to increase the coherence of FELs in the Soft X-ray regime. Our work puts special emphasis on accommodating the positive energy chirp of the electron bunch coming out of the MAX IV Linac and on generating sufficient bunching at the high harmonics necessary for covering the full wavelength range.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP090  
About • paper received ※ 20 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP091 Start-to-End Simulation of the NSRRC Seeded VUV FEL 266
 
  • S.Y. Teng
    NTHU, Hsinchu, Taiwan
  • C.H. Chen, W.K. Lau, A.P. Lee
    NSRRC, Hsinchu, Taiwan
 
  A free electron laser (FEL) driven by a high brightness electron linac system has been proposed to generate ultrashort intense coherent radiation in the vacuum ultraviolet region. It is a third harmonic high-gain high harmonic generation (HGHG) FEL for generation of VUV radiation with wavelength at 66.7 nm from a 20-mm period length helical undulator. A 200-nm seed laser is used for beam energy modulation in a 10-periods helical undulator of 24-mm period length. A small chicane is placed between the two undulators to optimize power growth in the radiator. In this study, we perform start-to-end simulation to foresee the operational performance of the test facility and preliminary results are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP091  
About • paper received ※ 20 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP092 XFEL Third Harmonic Statistics Measurement at LCLS 269
 
  • A. Halavanau, C. Emma, E. Hemsing, A.A. Lutman, G. Marcus, C. Pellegrini
    SLAC, Menlo Park, California, USA
 
  We investigate the statistical properties of the 6 keV third harmonic XFEL radiation at 2 keV fundamental photon energy at LCLS. We performed third harmonic self-seeding in the hard X-ray self-seeding chicane and characterized the attained non-linear third harmonic spectrum. We compare theoretical predictions with experimental results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP092  
About • paper received ※ 20 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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