FEL2019 - List of Keywords (free-electron-laser)

Paper	Title	Other Keywords	Page
MOA01	Riding the FEL Instability (Dedicated to Alberto Renieri)	electron, laser, storage-ring, radiation	1
	G. Dattoli ENEA C.R. Frascati, Frascati (Roma), Italy M.-E. Couprie SOLEIL, Gif-sur-Yvette, France C. Pellegrini SLAC, Menlo Park, California, USA
	The Free Electron Laser (FEL) operation, like that of any Free Electron source of coherent radiation, is associated with the onset of an instability. The interplay between the FEL and other instabilities, affecting the beam, is one of the interesting aspects of the associated dynamics. It involves issues of practical interest (Renieri Limit in Storage Ring FELs, suppression of instabilities like saw-tooth and synchrotron…). The paper reviews these problems and offers an overview of the scientific contribution of Alberto Renieri to the FEL from this perspective.
	Slides MOA01 [5.143 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-MOA01
About •	paper received ※ 26 August 2019 paper accepted ※ 09 September 2019 issue date ※ 05 November 2019
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MOA02	First Lasing of a Free Electron Laser in the Soft X-Ray Spectral Range with Echo Enabled Harmonic Generation	FEL, laser, electron, experiment	7
	E. Allaria, A. Abrami, L. Badano, M. Bossi, N. Bruchon, F. Capotondi, D. Castronovo, M. Cautero, P. Cinquegrana, M. Coreno, I. Cudin, M.B. Danailov, G. De Ninno, A.A. Demidovich, S. Di Mitri, B. Diviacco, W.M. Fawley, M. Ferianis, L. Foglia, G. Gaio, F. Giacuzzo, L. Giannessi, S. Grulja, F. Iazzourene, G. Kurdi, M. Lonza, N. Mahne, M. Malvestuto, M. Manfredda, C. Masciovecchio, N.S. Mirian, I. Nikolov, G. Penco, E. Principi, L. Raimondi, P. Rebernik Ribič, R. Sauro, C. Scafuri, P. Sigalotti, S. Spampinati, C. Spezzani, L. Sturari, M. Svandrlik, M. Trovò, M. Veronese, D. Vivoda, M. Zaccaria, D. Zangrando, M. Zangrando Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy H.-H. Braun, E. Ferrari, E. Prat, S. Reiche PSI, Villigen PSI, Switzerland N. Bruchon University of Trieste, Trieste, Italy M. Coreno CNR-ISM, Trieste, Italy M.-E. Couprie, A. Ghaith SOLEIL, Gif-sur-Yvette, France G. De Ninno University of Nova Gorica, Nova Gorica, Slovenia C. Feng SARI-CAS, Pudong, Shanghai, People’s Republic of China F. Frassetto, L.P. Poletto LUXOR, Padova, Italy D. Garzella CEA, Gif-sur-Yvette, France V. Grattoni DESY, Hamburg, Germany E. Hemsing SLAC, Menlo Park, California, USA P. Miotti CNR-IFN, Padova, Italy G. Penn LBNL, Berkeley, California, USA M.A. Pop MAX IV Laboratory, Lund University, Lund, Sweden E. Roussel PhLAM/CERCLA, Villeneuve d’Ascq Cedex, France T. Tanikawa EuXFEL, Schenefeld, Germany D. Xiang Shanghai Jiao Tong University, Shanghai, People’s Republic of China
	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.
	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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MOA03	First Lasing at the CAEP THz FEL Facility	FEL, electron, laser, high-voltage	11
	P. Li, T.H. He, M. Li, J. Liu, X. Luo, Q. Pan, L.J. Shan, X. Shen, H. Wang, J. Wang, D. Wu, D.X. Xiao, Y. Xu, L.G. Yan, P. Zhang, K. Zhou CAEP/IAE, Mianyang, Sichuan, People’s Republic of China Y. Liu CAEP/IFP, Mainyang, Sichuan, People’s Republic of China
	China Academy of Engineering Physics terahertz free electron laser (CAEP THz FEL, CTFEL) is the first THz FEL user facility in China, which was an oscillator type FEL. This THz FEL facility consists of a GaAs photocathode high-voltage DC gun, a superconducting RF linac, a planar undulator and a quasi-concentric optical resonator. The terahertz laser’s frequency is continuous adjustable from 0.7 THz to 4.2 THz. The average power is more than 10 W and the micro-pulse power is more than 0.3 MW. In this paper, the specific parameters and operation status of CTFEL are presented. Finally, some user experiments are introduced briefly.
	Slides MOA03 [3.771 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-MOA03
About •	paper received ※ 20 August 2019 paper accepted ※ 18 September 2019 issue date ※ 05 November 2019
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TUA04	Harmonic Lasing Experiment at the European XFEL	FEL, undulator, electron, laser	29
	E. Schneidmiller, F. Brinker, W. Decking, M.W. Guetg, S. Liu, D. Nölle, M. Scholz, M.V. Yurkov, I. Zagorodnov DESY, Hamburg, Germany G. Geloni, N. Gerasimova, J. Grünert, S. Karabekyan, N.G. Kujala, J. Laksman, Y. Li, J. Liu, Th. Maltezopoulos, I. Petrov, L. Samoylova, S. Serkez, H. Sinn, F. Wolff-Fabris EuXFEL, Schenefeld, Germany
	Harmonic lasing is an opportunity to extend the photon energy range of existing and planned X-ray FEL user facilities. Contrary to nonlinear harmonic generation, harmonic lasing can provide a much more intense, stable, and narrow-band FEL beam. Another interesting application is Harmonic Lasing Self-Seeding (HLSS) that allows to improve the longitudinal coherence and spectral power of a Self-Amplified Spontaneous Emission (SASE) FEL. This concept was successfully tested at FLASH in the range of 4.5 - 15 nm and at PAL XFEL at 1 nm. In this contribution we present recent results from the European XFEL where we successfully demonstrated operation of HLSS FEL at 5.9 Angstrom and 2.8 Angstrom, in the latter case obtaining both 3rd and 5th harmonic lasing.
	Slides TUA04 [1.174 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUA04
About •	paper received ※ 20 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019
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TUB01	Echo-Enabled Harmonic Generation Lasing of the FERMI FEL in the Soft X-Ray Spectral Region	laser, FEL, electron, photon	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 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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TUP033	Q-Switching of X-Ray Optical Cavities by Using Boron Doped Buried Layer Under a Surface of a Diamond Crystal	laser, FEL, cavity, electron	122
	J. Krzywiński, Y. Feng, A. Halavanau, Z. Huang, A.M. Kiss, J.P. MacArthur, G. Marcus, T. Sato, D. Zhu SLAC, Menlo Park, California, USA
	Improvement of the longitudinal coherence of X-ray Free Electron Lasers has been the subject of many recent investigations. The XFEL oscillator (XFELO) and Regenerative Amplifier Free-Electron Laser (RAFEL) schemes offer a pathway to fully coherent, high brightness X-ray radiation. The XFELO and RAFEL consist of a high repetition rate electron beam, an undulator and an X-ray crystal cavity to provide optical feedback. The X-ray cavity will be based on diamond crystals in order to manage a high thermal load. We are investigating a ’Q switching’ mechanism that involves the use of a ’Bragg switch’ to dump the X-ray pulse energy built-up inside an X-ray cavity. In particular, one can use an optical laser to manipulate the diamond crystal lattice constant to control the crystal reflectivity and transmission. It has been shown that a 9 MeV focused boron beam can create a buried layer, approximately 5 microns below surface, with a boron concentration up to 10²¹ atoms/cm³. Here, we present simulations showing that absorbing laser pulses by a buried layer under the crystal surface would allow creating a transient temperature profile which would be well suited for the ’Q switching’ scheme.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP033
About •	paper received ※ 21 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019
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TUP035	Sensitivity of LCLS Self-Seeded Pedestal Emission to Laser Heater Strength	laser, electron, experiment, bunching	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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TUP076	Seeding R&D at sFLASH	electron, laser, FEL, experiment	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	laser, electron, FEL, simulation	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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TUP088	Numerical Simulations for Generating Fully Coherent Soft X-Ray Free Electron Lasers With Ultra-Short Wavelength	electron, laser, radiation, FEL	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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WEP019	Concept of a Novel High-Bandwidth Arrival Time Monitor for Very Low Charges as a Part of the All-Optical Synchronization Systems at XFEL and FLASH	pick-up, laser, electron, FEL	368
	A. Penirschke THM, Friedberg, Germany W. Ackermann TEMF, TU Darmstadt, Darmstadt, Germany M.K. Czwalinna, H. Schlarb DESY, Hamburg, Germany
	Funding: This work is supported by the German Federal Ministry of Education and Research (BMBF) under contract no. 05K19RO1. Numerous advanced applications of X-ray free-electron lasers require pulse durations and time resolutions in the order of only a few femtoseconds or better. The generation of these pulses to be used in time-resolved experiments require synchronization techniques that can simultaneously lock all necessary components to a precision in the range of 1 fs only. To improve the experimental conditions at existing facilities and enable future development of seeded FELs, a new all-optical synchronization system at FLASH and XFEL was implemented, which is based on pulsed optical signals rather than electronic RF signals. In collaboration with DESY, Hamburg the all-optical synchronization system is used to ensure a timing stability on the 10 fs scale at XFEL. For a future ultra-low charge operation mode down to 1 pC at XFEL an overall synchronization of (5+1)fs r.m.s. or better is necessary. This contribution presents a new concept for a ultra-wideband pick-up structure for beampipe diameters down to 10 mm for frequencies up to 100 GHz or higher and at the same time providing sufficient output signal for the attached EOMs.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP019
About •	paper received ※ 23 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019
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WEP027	A Fast and Accurate Method to Shim Undulator Using Multi-Objective GA	undulator, electron, MMI, laser	378
	L.G. Yan, L.J. Chen, D.R. Deng, P. Li CAEP/IAE, Mianyang, Sichuan, People’s Republic of China
	Funding: National Natural Science Foundation of China under grant of 11505174, 11505173 and 11605190 GA (Genetic Algorithm) is one of the most excellent methods to search the optimal solution for a problem, which has been applied to solve various problems. It is hard to estimate shim applied on raw undulator precisely. There are many methods have been developed to solve the problem. In this proceeding, we proposed a fast and accurate method to conclude the shim using multi-objective GA. A multi-objective objective function was set, and multi-objective optimization was also implemented. The evolution time is reduced by setting optimal evolution parameters. To demonstrate the method, we also finished some test on a prototype undulator U38. As a result, it can be achieved only by shimming three times that all the parameters of trajectory center deviation, peak-to-peak error and phase error satisfied the requirements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP027
About •	paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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WEP034	Characterization of FEL Spectra Using Specific Figures of Merit	FEL, background, real-time, software	388
	M.A. Pop, F. Curbis MAX IV Laboratory, Lund University, Lund, Sweden E. Allaria Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy F. Curbis SLF, Lund, Sweden
	By analyzing the spectral content of FEL electron radiation, we can gain new information about the properties of the electron bunch and on the FEL process itself. In this work, we present a peak detection algorithm and its capabilities in characterizing the spectra of seeded FEL. This work is done in collaboration with FERMI Elettra-Sincrotrone Trieste, Area Science Park, Trieste, Italy
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP034
About •	paper received ※ 20 August 2019 paper accepted ※ 25 August 2019 issue date ※ 05 November 2019
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WEP035	NIR Spectrometer for Bunch-Resolved, Non-Destructive Studies of Microbunching at European XFEL	FEL, electron, laser, bunching	392
	S. Fahlström, M. Hamberg Uppsala University, Uppsala, Sweden C. Gerth, N.M. Lockmann, B. Steffen DESY, Hamburg, Germany
	At the European X-ray Free Electron Laser high brilliance femtosecond FEL radiation pulses are generated for user experiments. For this to be achieved electron bunches must be reliably produced within very tight tolerances. In order to investigate the presence of micro-bunching, i.e. charge density variation along the electron bunch with features in the micron range, a prism-based NIR spectrometer with an InGaAs sensor, sensitive in the wavelength range 900 nm to 1700 nm was installed. The spectrometer utilizes diffraction radiation (DR) generated at electron beam energies of up to 17.5 GeV. The MHz repetition rate needed for bunch resolved measurements is made possible by the KALYPSO line detector system, providing a read-out rate of up to 2.7 MHz. We present the first findings from commissioning of the NIR spectrometer, and measurements on the impact of the laser heater system for various bunch compression settings, in terms of amplitude and bunch-to-bunch variance of the NIR spectra as well as FEL pulse energy.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP035
About •	paper received ※ 20 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019
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WEP048	FLASH Photoinjector Laser Systems	laser, electron, operation, cathode	430
	S. Schreiber, C. Grün, K. Klose, J. Rönsch-Schulenburg, B. Steffen DESY, Hamburg, Germany
	The free-electron laser facility FLASH at DESY (Hamburg, Germany) operates two undulator beamlines simultaneously for FEL operation and a third for plasma acceleration experiments (FLASHForward). The L-band superconducting technology allows accelerating fields of up to 0.8 ms in length at a repetition rate of 10 Hz (burst mode). A fast kicker-septum system picks one part of the 1 MHz electron bunch train and kicks it to the second beamline such that two beamlines are operated simultaneously with the full repetition rate of 10 Hz. The photoinjector operates three laser systems. They have different pulse durations and transverse shapes and are chosen to serve best for the given user experiment in terms of electron bunch charge, bunch compression, and bunch pattern. It is also possible to operate the laser systems on the same beamline to provide specific double pulses for certain type of experiments.
	Poster WEP048 [2.642 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP048
About •	paper received ※ 26 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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WEP080	ROSA: Reconstruction of Spectrogram Autocorrelation for Self-Amplified Spontaneous Emission Free-Electron Lasers	radiation, FEL, electron, laser	506
	S. Serkez, G. Geloni, N. Gerasimova EuXFEL, Schenefeld, Germany O. Gorobtsov Cornell University, Ithaca, New York, USA B. Sobko LNU, Lviv, Ukraine
	X-ray Free Electron Lasers (FELs) have opened new avenues in photon science, providing coherent X-ray radiation pulses orders of magnitude brighter and shorter than previously possible. The emerging concept of "beam by design" in FEL accelerator physics aims for accurate manipulation of the electron beam to tailor spectral and temporal properties of radiation for specific experimental purposes, such as X-ray pump/X-ray probe and multiple wavelength experiments. A cost-efficient method to extract information on longitudinal Wigner distribution function of emitted FEL pulses is proposed. It requires only an ensemble of measured FEL spectra.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP080
About •	paper received ※ 20 August 2019 paper accepted ※ 26 August 2019 issue date ※ 05 November 2019
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THP018	Transverse Deflecting Structure Dynamics for Time-Resolved Machine Studies of Shine	electron, FEL, cavity, laser	632
	J.W. Yan, H.X. Deng, B. Liu, D. Wang SINAP, Shanghai, People’s Republic of China H.X. Deng, B. Liu, D. Wang SARI-CAS, Pudong, Shanghai, People’s Republic of China
	Funding: National Natural Science Foundation of China (11775293), the National Key Research and Development Program of China (2016YFA0401900) and Ten Thousand Talent Program. The transverse deflecting structure (TDS) has been widely used in modern free electron laser facilities for the longitudinal phase space diagnostics of electron beams. As the first hard x-ray free electron laser in China, the SHINE is designed to deliver photons with a repetition rate up to 1 MHz. In this paper, we present the beam dynamics study of the X-band TDS behind the undulator of SHINE. In order to prevent the screen from being damaged by electron bunches with a high repetition rate, the phase of the transverse deflecting cavity is designed to deviate from zero, and only those electron bunches that are kicked by the transverse deflecting cavity are sent to the screen. In addition, the evolutionary algorithm is introduced to optimize the lattice of the TDS line to reach the highest possible resolution.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP018
About •	paper received ※ 19 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019
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THP022	A General Optimization Method for High Harmonic Generation Beamline	laser, electron, radiation, coupling	638
	Y. Zhang, X.J. Deng, W.-H. Huang, Z. Pan, C.-X. Tang TUB, Beijing, People’s Republic of China
	Shorter bunches produce a more coherent radiation and contain higher harmonic components. Here, based on transverse and longitudinal phase space coupling, a general method for analyzing the production of very short beam and searching for compression beamline is presented. With this method, several beamlines are found and optimized. The electron beam can be compressed to tens of nanometers, generating coherent high harmonic radiation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP022
About •	paper received ※ 20 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019
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THP051	Generating Trains of Attosecond Pulses with a Free-Electron Laser	FEL, electron, laser, radiation	692
	S. Serkez, G. Geloni EuXFEL, Schenefeld, Germany M.H. Cho, H.-S. Kang, G. Kim, J.H. Ko, C.-K. Min, I.H. Nam, C.H. Shim PAL, Pohang, Republic of Korea F.-J. Decker SLAC, Menlo Park, California, USA J.H. Ko, C.H. Shim POSTECH, Pohang, Kyungbuk, Republic of Korea Yu. Shvyd’ko ANL, Lemont, Illinois, USA
	Recently, a Hard X-ray Self-Seeding setup was commissioned at PAL XFEL. Its main purpose is to increase the temporal coherence of FEL radiation in an active way. We report another application of this setup to generate trains of short sub-femtosecond pulses with linked phases. We discuss preliminary results of both experiment and corresponding simulations as well as indirect diagnostics of the radiation properties.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP051
About •	paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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THP074	FLASH: The Pioneering XUV and Soft X-Ray FEL User Facility	FEL, electron, laser, undulator	734
	K. Honkavaara, S. Schreiber DESY, Hamburg, Germany
	FLASH, the free-electron laser (FEL) at DESY (Hamburg) started user operation in summer 2005. It delivers high peak and average brilliance XUV and soft X-ray FEL radiation to photon experiments. Nowadays, FLASH has a 1.25 GeV superconducting linac, and two undulator beamlines, which are operated simultaneously. This paper provides an overview of its evolution from a test facility for superconducting accelerator technology to a full-scale FEL user facility.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP074
About •	paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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THP079	Status and Perspectives of the FERMI FEL Facility (2019)	FEL, laser, electron, linac	742
	L. Giannessi, E. Allaria, L. Badano, S. Bassanese, F. Bencivenga, C. Callegari, F. Capotondi, D. Castronovo, F. Cilento, P. Cinquegrana, M. Coreno, I. Cudin, G. D’Auria, M.B. Danailov, R. De Monte, G. De Ninno, P. Delgiusto, A.A. Demidovich, M. Di Fraia, S. Di Mitri, B. Diviacco, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, L. Foglia, P. Furlan Radivo, G. Gaio, F. Gelmetti, F. Iazzourene, S. Krecic, G. Kurdi, M. Lonza, N. Mahne, M. Malvestuto, M. Manfredda, C. Masciovecchio, M. Milloch, R. Mincigrucci, N.S. Mirian, I. Nikolov, F.H. O’Shea, G. Penco, A. Perucchi, O. Plekan, M. Predonzani, K.C. Prince, E. Principi, L. Raimondi, P. Rebernik Ribič, F. Rossi, L. Rumiz, C. Scafuri, C. Serpico, N. Shafqat, P. Sigalotti, A. Simoncig, S. Spampinati, C. Spezzani, M. Svandrlik, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	FERMI is the seeded Free Electron Laser (FEL) user facility at the Elettra laboratory in Trieste, operating in the VUV to EUV and soft X-rays spectral range; the radiation produced by the seeded FEL is characterized by wavelength stability, low temporal jitter and longitudinal coherence in the range 100-4 nm. During 2018 a dedicated experiment has shown the potential of the Echo Enabled Harmonic Generation (EEHG) scheme [1] to cover most of this spectral range with a single stage cascade [2]. Such a scheme, combined to an increment of the beam energy and of the accelerator performances, could extend the FERMI operating range toward the oxygen k-edge. With this perspective, we present the development plans under consideration for the next 3 to 5 years. These include an upgrade of the linac and of the existing FEL lines, consisting in the conversion of FEL-1 first, and FEL-2 successively, into EEHG seeded FELs. [1] G. Stupakov, Phys. Rev. Lett. 102, 74801 (2009) [2] P. Rebernik et al., Nature Photonics https://doi.org/10.1038/s41566-019-0427-1
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP079
About •	paper received ※ 28 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019
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THP086	Operation Modes of the SwissFEL Soft X-Ray Beamline Athos	electron, undulator, laser, FEL	757
	S. Reiche, E. Ferrari, E. Prat, T. Schietinger PSI, Villigen PSI, Switzerland
	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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FRA03	FLASH - Status and Upgrades	laser, electron, FEL, undulator	776
	J. Rönsch-Schulenburg, K. Honkavaara, S. Schreiber, R. Treusch, M. Vogt DESY, Hamburg, Germany
	FLASH, the Free-Electron Laser at DESY in Hamburg was the first FEL user facility in the XUV and soft X-ray range. The superconducting RF technology allows to produce several thousand SASE pulses per second with a high peak and average brilliance. It developed to a user facility with a 1.25 GeV linear accelerator, two undulator beamlines running in parallel, and a third electron beamline containing the FLASHForward plasma wakefield experiment. Actual user operation and FEL research are discussed. New concepts and a redesign of the facility are developed to ensure that also in future FLASH will allow cutting-edge research. Upgrade plans are discussed in the contribution.
	Slides FRA03 [10.554 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-FRA03
About •	paper received ※ 20 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019
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MOA01

Riding the FEL Instability (Dedicated to Alberto Renieri)

electron, laser, storage-ring, radiation

1

G. Dattoli
ENEA C.R. Frascati, Frascati (Roma), Italy
M.-E. Couprie
SOLEIL, Gif-sur-Yvette, France
C. Pellegrini
SLAC, Menlo Park, California, USA

The Free Electron Laser (FEL) operation, like that of any Free Electron source of coherent radiation, is associated with the onset of an instability. The interplay between the FEL and other instabilities, affecting the beam, is one of the interesting aspects of the associated dynamics. It involves issues of practical interest (Renieri Limit in Storage Ring FELs, suppression of instabilities like saw-tooth and synchrotron…). The paper reviews these problems and offers an overview of the scientific contribution of Alberto Renieri to the FEL from this perspective.

Slides MOA01 [5.143 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-MOA01

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paper received ※ 26 August 2019 paper accepted ※ 09 September 2019 issue date ※ 05 November 2019

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MOA02

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

FEL, laser, electron, experiment

7

E. Allaria, A. Abrami, L. Badano, M. Bossi, N. Bruchon, F. Capotondi, D. Castronovo, M. Cautero, P. Cinquegrana, M. Coreno, I. Cudin, M.B. Danailov, G. De Ninno, A.A. Demidovich, S. Di Mitri, B. Diviacco, W.M. Fawley, M. Ferianis, L. Foglia, G. Gaio, F. Giacuzzo, L. Giannessi, S. Grulja, F. Iazzourene, G. Kurdi, M. Lonza, N. Mahne, M. Malvestuto, M. Manfredda, C. Masciovecchio, N.S. Mirian, I. Nikolov, G. Penco, E. Principi, L. Raimondi, P. Rebernik Ribič, R. Sauro, C. Scafuri, P. Sigalotti, S. Spampinati, C. Spezzani, L. Sturari, M. Svandrlik, M. Trovò, M. Veronese, D. Vivoda, M. Zaccaria, D. Zangrando, M. Zangrando
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
H.-H. Braun, E. Ferrari, E. Prat, S. Reiche
PSI, Villigen PSI, Switzerland
N. Bruchon
University of Trieste, Trieste, Italy
M. Coreno
CNR-ISM, Trieste, Italy
M.-E. Couprie, A. Ghaith
SOLEIL, Gif-sur-Yvette, France
G. De Ninno
University of Nova Gorica, Nova Gorica, Slovenia
C. Feng
SARI-CAS, Pudong, Shanghai, People’s Republic of China
F. Frassetto, L.P. Poletto
LUXOR, Padova, Italy
D. Garzella
CEA, Gif-sur-Yvette, France
V. Grattoni
DESY, Hamburg, Germany
E. Hemsing
SLAC, Menlo Park, California, USA
P. Miotti
CNR-IFN, Padova, Italy
G. Penn
LBNL, Berkeley, California, USA
M.A. Pop
MAX IV Laboratory, Lund University, Lund, Sweden
E. Roussel
PhLAM/CERCLA, Villeneuve d’Ascq Cedex, France
T. Tanikawa
EuXFEL, Schenefeld, Germany
D. Xiang
Shanghai Jiao Tong University, Shanghai, People’s Republic of China

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.

Slides MOA02 [5.133 MB]

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paper received ※ 21 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019

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MOA03

First Lasing at the CAEP THz FEL Facility

FEL, electron, laser, high-voltage

11

P. Li, T.H. He, M. Li, J. Liu, X. Luo, Q. Pan, L.J. Shan, X. Shen, H. Wang, J. Wang, D. Wu, D.X. Xiao, Y. Xu, L.G. Yan, P. Zhang, K. Zhou
CAEP/IAE, Mianyang, Sichuan, People’s Republic of China
Y. Liu
CAEP/IFP, Mainyang, Sichuan, People’s Republic of China

China Academy of Engineering Physics terahertz free electron laser (CAEP THz FEL, CTFEL) is the first THz FEL user facility in China, which was an oscillator type FEL. This THz FEL facility consists of a GaAs photocathode high-voltage DC gun, a superconducting RF linac, a planar undulator and a quasi-concentric optical resonator. The terahertz laser’s frequency is continuous adjustable from 0.7 THz to 4.2 THz. The average power is more than 10 W and the micro-pulse power is more than 0.3 MW. In this paper, the specific parameters and operation status of CTFEL are presented. Finally, some user experiments are introduced briefly.

Slides MOA03 [3.771 MB]

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paper received ※ 20 August 2019 paper accepted ※ 18 September 2019 issue date ※ 05 November 2019

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TUA04

Harmonic Lasing Experiment at the European XFEL

FEL, undulator, electron, laser

29

E. Schneidmiller, F. Brinker, W. Decking, M.W. Guetg, S. Liu, D. Nölle, M. Scholz, M.V. Yurkov, I. Zagorodnov
DESY, Hamburg, Germany
G. Geloni, N. Gerasimova, J. Grünert, S. Karabekyan, N.G. Kujala, J. Laksman, Y. Li, J. Liu, Th. Maltezopoulos, I. Petrov, L. Samoylova, S. Serkez, H. Sinn, F. Wolff-Fabris
EuXFEL, Schenefeld, Germany

Harmonic lasing is an opportunity to extend the photon energy range of existing and planned X-ray FEL user facilities. Contrary to nonlinear harmonic generation, harmonic lasing can provide a much more intense, stable, and narrow-band FEL beam. Another interesting application is Harmonic Lasing Self-Seeding (HLSS) that allows to improve the longitudinal coherence and spectral power of a Self-Amplified Spontaneous Emission (SASE) FEL. This concept was successfully tested at FLASH in the range of 4.5 - 15 nm and at PAL XFEL at 1 nm. In this contribution we present recent results from the European XFEL where we successfully demonstrated operation of HLSS FEL at 5.9 Angstrom and 2.8 Angstrom, in the latter case obtaining both 3rd and 5th harmonic lasing.

Slides TUA04 [1.174 MB]

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TUB01

Echo-Enabled Harmonic Generation Lasing of the FERMI FEL in the Soft X-Ray Spectral Region

laser, FEL, electron, photon

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 TUB01 [10.360 MB]

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paper received ※ 21 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019

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TUP033

Q-Switching of X-Ray Optical Cavities by Using Boron Doped Buried Layer Under a Surface of a Diamond Crystal

laser, FEL, cavity, electron

122

J. Krzywiński, Y. Feng, A. Halavanau, Z. Huang, A.M. Kiss, J.P. MacArthur, G. Marcus, T. Sato, D. Zhu
SLAC, Menlo Park, California, USA

Improvement of the longitudinal coherence of X-ray Free Electron Lasers has been the subject of many recent investigations. The XFEL oscillator (XFELO) and Regenerative Amplifier Free-Electron Laser (RAFEL) schemes offer a pathway to fully coherent, high brightness X-ray radiation. The XFELO and RAFEL consist of a high repetition rate electron beam, an undulator and an X-ray crystal cavity to provide optical feedback. The X-ray cavity will be based on diamond crystals in order to manage a high thermal load. We are investigating a ’Q switching’ mechanism that involves the use of a ’Bragg switch’ to dump the X-ray pulse energy built-up inside an X-ray cavity. In particular, one can use an optical laser to manipulate the diamond crystal lattice constant to control the crystal reflectivity and transmission. It has been shown that a 9 MeV focused boron beam can create a buried layer, approximately 5 microns below surface, with a boron concentration up to 10²¹ atoms/cm³. Here, we present simulations showing that absorbing laser pulses by a buried layer under the crystal surface would allow creating a transient temperature profile which would be well suited for the ’Q switching’ scheme.

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paper received ※ 21 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019

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TUP035

Sensitivity of LCLS Self-Seeded Pedestal Emission to Laser Heater Strength

laser, electron, experiment, bunching

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.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP035

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paper received ※ 28 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019

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TUP076

Seeding R&D at sFLASH

electron, laser, FEL, experiment

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.

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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

laser, electron, FEL, simulation

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.

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paper received ※ 19 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

electron, laser, radiation, FEL

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.

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paper received ※ 20 August 2019 paper accepted ※ 22 October 2019 issue date ※ 05 November 2019

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WEP019

Concept of a Novel High-Bandwidth Arrival Time Monitor for Very Low Charges as a Part of the All-Optical Synchronization Systems at XFEL and FLASH

pick-up, laser, electron, FEL

368

A. Penirschke
THM, Friedberg, Germany
W. Ackermann
TEMF, TU Darmstadt, Darmstadt, Germany
M.K. Czwalinna, H. Schlarb
DESY, Hamburg, Germany

Funding: This work is supported by the German Federal Ministry of Education and Research (BMBF) under contract no. 05K19RO1.
Numerous advanced applications of X-ray free-electron lasers require pulse durations and time resolutions in the order of only a few femtoseconds or better. The generation of these pulses to be used in time-resolved experiments require synchronization techniques that can simultaneously lock all necessary components to a precision in the range of 1 fs only. To improve the experimental conditions at existing facilities and enable future development of seeded FELs, a new all-optical synchronization system at FLASH and XFEL was implemented, which is based on pulsed optical signals rather than electronic RF signals. In collaboration with DESY, Hamburg the all-optical synchronization system is used to ensure a timing stability on the 10 fs scale at XFEL. For a future ultra-low charge operation mode down to 1 pC at XFEL an overall synchronization of (5+1)fs r.m.s. or better is necessary. This contribution presents a new concept for a ultra-wideband pick-up structure for beampipe diameters down to 10 mm for frequencies up to 100 GHz or higher and at the same time providing sufficient output signal for the attached EOMs.

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paper received ※ 23 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019

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WEP027

A Fast and Accurate Method to Shim Undulator Using Multi-Objective GA

undulator, electron, MMI, laser

378

L.G. Yan, L.J. Chen, D.R. Deng, P. Li
CAEP/IAE, Mianyang, Sichuan, People’s Republic of China

Funding: National Natural Science Foundation of China under grant of 11505174, 11505173 and 11605190
GA (Genetic Algorithm) is one of the most excellent methods to search the optimal solution for a problem, which has been applied to solve various problems. It is hard to estimate shim applied on raw undulator precisely. There are many methods have been developed to solve the problem. In this proceeding, we proposed a fast and accurate method to conclude the shim using multi-objective GA. A multi-objective objective function was set, and multi-objective optimization was also implemented. The evolution time is reduced by setting optimal evolution parameters. To demonstrate the method, we also finished some test on a prototype undulator U38. As a result, it can be achieved only by shimming three times that all the parameters of trajectory center deviation, peak-to-peak error and phase error satisfied the requirements.

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paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019

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WEP034

Characterization of FEL Spectra Using Specific Figures of Merit

FEL, background, real-time, software

388

M.A. Pop, F. Curbis
MAX IV Laboratory, Lund University, Lund, Sweden
E. Allaria
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
F. Curbis
SLF, Lund, Sweden

By analyzing the spectral content of FEL electron radiation, we can gain new information about the properties of the electron bunch and on the FEL process itself. In this work, we present a peak detection algorithm and its capabilities in characterizing the spectra of seeded FEL.
This work is done in collaboration with FERMI Elettra-Sincrotrone Trieste, Area Science Park, Trieste, Italy

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paper received ※ 20 August 2019 paper accepted ※ 25 August 2019 issue date ※ 05 November 2019

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WEP035

NIR Spectrometer for Bunch-Resolved, Non-Destructive Studies of Microbunching at European XFEL

FEL, electron, laser, bunching

392

S. Fahlström, M. Hamberg
Uppsala University, Uppsala, Sweden
C. Gerth, N.M. Lockmann, B. Steffen
DESY, Hamburg, Germany

At the European X-ray Free Electron Laser high brilliance femtosecond FEL radiation pulses are generated for user experiments. For this to be achieved electron bunches must be reliably produced within very tight tolerances. In order to investigate the presence of micro-bunching, i.e. charge density variation along the electron bunch with features in the micron range, a prism-based NIR spectrometer with an InGaAs sensor, sensitive in the wavelength range 900 nm to 1700 nm was installed. The spectrometer utilizes diffraction radiation (DR) generated at electron beam energies of up to 17.5 GeV. The MHz repetition rate needed for bunch resolved measurements is made possible by the KALYPSO line detector system, providing a read-out rate of up to 2.7 MHz. We present the first findings from commissioning of the NIR spectrometer, and measurements on the impact of the laser heater system for various bunch compression settings, in terms of amplitude and bunch-to-bunch variance of the NIR spectra as well as FEL pulse energy.

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WEP048

FLASH Photoinjector Laser Systems

laser, electron, operation, cathode

430

S. Schreiber, C. Grün, K. Klose, J. Rönsch-Schulenburg, B. Steffen
DESY, Hamburg, Germany

The free-electron laser facility FLASH at DESY (Hamburg, Germany) operates two undulator beamlines simultaneously for FEL operation and a third for plasma acceleration experiments (FLASHForward). The L-band superconducting technology allows accelerating fields of up to 0.8 ms in length at a repetition rate of 10 Hz (burst mode). A fast kicker-septum system picks one part of the 1 MHz electron bunch train and kicks it to the second beamline such that two beamlines are operated simultaneously with the full repetition rate of 10 Hz. The photoinjector operates three laser systems. They have different pulse durations and transverse shapes and are chosen to serve best for the given user experiment in terms of electron bunch charge, bunch compression, and bunch pattern. It is also possible to operate the laser systems on the same beamline to provide specific double pulses for certain type of experiments.

Poster WEP048 [2.642 MB]

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paper received ※ 26 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019

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WEP080

ROSA: Reconstruction of Spectrogram Autocorrelation for Self-Amplified Spontaneous Emission Free-Electron Lasers

radiation, FEL, electron, laser

506

S. Serkez, G. Geloni, N. Gerasimova
EuXFEL, Schenefeld, Germany
O. Gorobtsov
Cornell University, Ithaca, New York, USA
B. Sobko
LNU, Lviv, Ukraine

X-ray Free Electron Lasers (FELs) have opened new avenues in photon science, providing coherent X-ray radiation pulses orders of magnitude brighter and shorter than previously possible. The emerging concept of "beam by design" in FEL accelerator physics aims for accurate manipulation of the electron beam to tailor spectral and temporal properties of radiation for specific experimental purposes, such as X-ray pump/X-ray probe and multiple wavelength experiments. A cost-efficient method to extract information on longitudinal Wigner distribution function of emitted FEL pulses is proposed. It requires only an ensemble of measured FEL spectra.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP080

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paper received ※ 20 August 2019 paper accepted ※ 26 August 2019 issue date ※ 05 November 2019

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THP018

Transverse Deflecting Structure Dynamics for Time-Resolved Machine Studies of Shine

electron, FEL, cavity, laser

632

J.W. Yan, H.X. Deng, B. Liu, D. Wang
SINAP, Shanghai, People’s Republic of China
H.X. Deng, B. Liu, D. Wang
SARI-CAS, Pudong, Shanghai, People’s Republic of China

Funding: National Natural Science Foundation of China (11775293), the National Key Research and Development Program of China (2016YFA0401900) and Ten Thousand Talent Program.
The transverse deflecting structure (TDS) has been widely used in modern free electron laser facilities for the longitudinal phase space diagnostics of electron beams. As the first hard x-ray free electron laser in China, the SHINE is designed to deliver photons with a repetition rate up to 1 MHz. In this paper, we present the beam dynamics study of the X-band TDS behind the undulator of SHINE. In order to prevent the screen from being damaged by electron bunches with a high repetition rate, the phase of the transverse deflecting cavity is designed to deviate from zero, and only those electron bunches that are kicked by the transverse deflecting cavity are sent to the screen. In addition, the evolutionary algorithm is introduced to optimize the lattice of the TDS line to reach the highest possible resolution.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP018

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paper received ※ 19 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019

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THP022

A General Optimization Method for High Harmonic Generation Beamline

laser, electron, radiation, coupling

638

Y. Zhang, X.J. Deng, W.-H. Huang, Z. Pan, C.-X. Tang
TUB, Beijing, People’s Republic of China

Shorter bunches produce a more coherent radiation and contain higher harmonic components. Here, based on transverse and longitudinal phase space coupling, a general method for analyzing the production of very short beam and searching for compression beamline is presented. With this method, several beamlines are found and optimized. The electron beam can be compressed to tens of nanometers, generating coherent high harmonic radiation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP022

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paper received ※ 20 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019

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THP051

Generating Trains of Attosecond Pulses with a Free-Electron Laser

FEL, electron, laser, radiation

692

S. Serkez, G. Geloni
EuXFEL, Schenefeld, Germany
M.H. Cho, H.-S. Kang, G. Kim, J.H. Ko, C.-K. Min, I.H. Nam, C.H. Shim
PAL, Pohang, Republic of Korea
F.-J. Decker
SLAC, Menlo Park, California, USA
J.H. Ko, C.H. Shim
POSTECH, Pohang, Kyungbuk, Republic of Korea
Yu. Shvyd’ko
ANL, Lemont, Illinois, USA

Recently, a Hard X-ray Self-Seeding setup was commissioned at PAL XFEL. Its main purpose is to increase the temporal coherence of FEL radiation in an active way. We report another application of this setup to generate trains of short sub-femtosecond pulses with linked phases. We discuss preliminary results of both experiment and corresponding simulations as well as indirect diagnostics of the radiation properties.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP051

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paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019

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THP074

FLASH: The Pioneering XUV and Soft X-Ray FEL User Facility

FEL, electron, laser, undulator

734

K. Honkavaara, S. Schreiber
DESY, Hamburg, Germany

FLASH, the free-electron laser (FEL) at DESY (Hamburg) started user operation in summer 2005. It delivers high peak and average brilliance XUV and soft X-ray FEL radiation to photon experiments. Nowadays, FLASH has a 1.25 GeV superconducting linac, and two undulator beamlines, which are operated simultaneously. This paper provides an overview of its evolution from a test facility for superconducting accelerator technology to a full-scale FEL user facility.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP074

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paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019

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THP079

Status and Perspectives of the FERMI FEL Facility (2019)

FEL, laser, electron, linac

742

L. Giannessi, E. Allaria, L. Badano, S. Bassanese, F. Bencivenga, C. Callegari, F. Capotondi, D. Castronovo, F. Cilento, P. Cinquegrana, M. Coreno, I. Cudin, G. D’Auria, M.B. Danailov, R. De Monte, G. De Ninno, P. Delgiusto, A.A. Demidovich, M. Di Fraia, S. Di Mitri, B. Diviacco, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, L. Foglia, P. Furlan Radivo, G. Gaio, F. Gelmetti, F. Iazzourene, S. Krecic, G. Kurdi, M. Lonza, N. Mahne, M. Malvestuto, M. Manfredda, C. Masciovecchio, M. Milloch, R. Mincigrucci, N.S. Mirian, I. Nikolov, F.H. O’Shea, G. Penco, A. Perucchi, O. Plekan, M. Predonzani, K.C. Prince, E. Principi, L. Raimondi, P. Rebernik Ribič, F. Rossi, L. Rumiz, C. Scafuri, C. Serpico, N. Shafqat, P. Sigalotti, A. Simoncig, S. Spampinati, C. Spezzani, M. Svandrlik, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

FERMI is the seeded Free Electron Laser (FEL) user facility at the Elettra laboratory in Trieste, operating in the VUV to EUV and soft X-rays spectral range; the radiation produced by the seeded FEL is characterized by wavelength stability, low temporal jitter and longitudinal coherence in the range 100-4 nm. During 2018 a dedicated experiment has shown the potential of the Echo Enabled Harmonic Generation (EEHG) scheme [1] to cover most of this spectral range with a single stage cascade [2]. Such a scheme, combined to an increment of the beam energy and of the accelerator performances, could extend the FERMI operating range toward the oxygen k-edge. With this perspective, we present the development plans under consideration for the next 3 to 5 years. These include an upgrade of the linac and of the existing FEL lines, consisting in the conversion of FEL-1 first, and FEL-2 successively, into EEHG seeded FELs.
[1] G. Stupakov, Phys. Rev. Lett. 102, 74801 (2009)
[2] P. Rebernik et al., Nature Photonics https://doi.org/10.1038/s41566-019-0427-1

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP079

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paper received ※ 28 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019

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THP086

Operation Modes of the SwissFEL Soft X-Ray Beamline Athos

electron, undulator, laser, FEL

757

S. Reiche, E. Ferrari, E. Prat, T. Schietinger
PSI, Villigen PSI, Switzerland

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.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP086

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paper received ※ 23 August 2019 paper accepted ※ 16 September 2019 issue date ※ 05 November 2019

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FRA03

FLASH - Status and Upgrades

laser, electron, FEL, undulator

776

J. Rönsch-Schulenburg, K. Honkavaara, S. Schreiber, R. Treusch, M. Vogt
DESY, Hamburg, Germany

FLASH, the Free-Electron Laser at DESY in Hamburg was the first FEL user facility in the XUV and soft X-ray range. The superconducting RF technology allows to produce several thousand SASE pulses per second with a high peak and average brilliance. It developed to a user facility with a 1.25 GeV linear accelerator, two undulator beamlines running in parallel, and a third electron beamline containing the FLASHForward plasma wakefield experiment. Actual user operation and FEL research are discussed. New concepts and a redesign of the facility are developed to ensure that also in future FLASH will allow cutting-edge research. Upgrade plans are discussed in the contribution.

Slides FRA03 [10.554 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-FRA03

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paper received ※ 20 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019

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