FEL2019 - List of Keywords (photon)

Paper	Title	Other Keywords	Page
TUB01	Echo-Enabled Harmonic Generation Lasing of the FERMI FEL in the Soft X-Ray Spectral Region	laser, FEL, electron, free-electron-laser	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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TUP053	An Investigation of Possible Non-Standard Photon Statistics in a Free-Electron Laser I: Experiment	FEL, experiment, cavity, radiation	161
	J.-W. Park University of Hawaii, Honolulu,, USA K.-J. Kim, R.R. Lindberg ANL, Lemont, Illinois, USA
	Funding: Work supported by U.S. DOE, Office of Science, Office of BES, under Award No. DE-SC0018428. It was reported that the photon statistics of the seventh coherent spontaneous harmonic radiation of the MARK III FEL was sub-Poissonian [1], which concludes that Fano factor F (the ratio of photon number variance to the average photon number) is less than unity. Whether FEL light exhibits such non-standard behavior is an important issue; if it does, our understanding of the FEL needs to be radically modified. In this paper, we re-examine the analyses of experimental data in Ref. [1]. We find that the observed value of F could be explained within the standard FEL theory if one combines the detector dead time effect with photon clustering arising from the FEL gain. We propose an improved experiment for a more definitive measurement of the FEL photon statistics. [1] T. Chen and J.M. Madey, J. Phys. Rev. Lett. 86, 5906 (2001).
	Poster TUP053 [0.929 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP053
About •	paper received ※ 21 August 2019 paper accepted ※ 12 September 2019 issue date ※ 05 November 2019
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TUP054	An Investigation of Possible Non-Standard Photon Statistics in a Free-Electron Laser II: Theory	electron, FEL, radiation, laser	165
	J.-W. Park University of Hawaii, Honolulu,, USA K.-J. Kim, R.R. Lindberg ANL, Lemont, Illinois, USA K.-J. Kim University of Chicago, Chicago, Illinois, USA
	Funding: Work supported by U.S. DOE, Office of Science, Office of BES, under Award No. DE-SC0018428. In this paper we explore whether we can at present find a theoretical basis for non-standard, sub-Poissonian photon statistics in the coherent spontaneous harmonic radiation of an FEL as was claimed to have been measured with the Mark III FEL [1]. We develop a one dimensional quantum FEL oscillator model of the harmonic radiation in the linear gain regime to calculate the photon statistics. According to our study, it seems unlikely that the photon statistics for an FEL oscillator starting from the noise could be sub-Poissonian. [1] T. Chen and J.M. Madey, J. Phys. Rev. Lett. 86, 5906 (2001).
	Poster TUP054 [0.386 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP054
About •	paper received ※ 21 August 2019 paper accepted ※ 16 September 2019 issue date ※ 05 November 2019
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TUP056	Feasibility Studies of the 100 keV Undulator Line of the European XFEL	undulator, FEL, electron, laser	172
	E. Schneidmiller, V. Balandin, W. Decking, M. Dohlus, N. Golubeva, D. Nölle, M.V. Yurkov, I. Zagorodnov DESY, Hamburg, Germany G. Geloni, Y. Li, S. Molodtsov, J. Pflüger, S. Serkez, H. Sinn, T. Tanikawa, S. Tomin EuXFEL, Schenefeld, Germany
	The European XFEL is a multi-user X-ray FEL facility based on superconducting linear accelerator. Presently, three undulators (SASE1, SASE2, SASE3) deliver high-brightness soft- and hard- X-ray beams for users. There are two empty undulator tunnels that were originally designed to operate with spontaneous radiators. We consider instead a possible installation of two FEL undulators. One of them (SASE4) is proposed for the operation in ultrahard X-ray regime, up to the photon energy of 100 keV. In this contribution we present the results of the first feasibility studies of this option.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP056
About •	paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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TUP058	First Characterization of the Photon Beam at the European XFEL in July, 2017	FEL, radiation, electron, undulator	180
	V. Balandin, B. Beutner, F. Brinker, W. Decking, M. Dohlus, L. Fröhlich, U. Jastrow, R. Kammering, T. Limberg, D. Nölle, M. Scholz, A.A. Sorokin, K.I. Tiedtke, M.V. Yurkov, I. Zagorodnov DESY, Hamburg, Germany U. Boesenberg, W. Freund, J. Grünert, A. Koch, N.G. Kujala, J. Liu, Th. Maltezopoulos, M. Messerschmidt, I. Petrov, L. Samoylova, H. Sinn EuXFEL, Schenefeld, Germany
	North branch of the European XFEL, SASE1, produced first light on May 3rd, 2017, and XFEL operation has been gradually improved then. First characterization of the photon beam has been performed in July / August 2017, just before an official starting date of user experiments (September 1st, 2017). Energy of the electron beam was 14 GeV, bunch charge was 500 pC, photon energy was 9.3 keV. With photon diagnostics available at that time (X-ray gas monitor (XGM) and FEL imager) we measured the gain curve and traced evolution of the FEL radiation mode along the undulator. An important conclusion is that experimental results demonstrate reasonable agreement with baseline parameters. Developed techniques of the photon beam characterization also provided solid base for identification of the problems and means for improving SASE FEL tuning and operation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP058
About •	paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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TUP060	An Advanced Compression Option for the European XFEL	electron, undulator, laser, FEL	187
	I. Zagorodnov, M. Dohlus, E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	An advanced compression scheme which allows to obtain a high peak current while preserving the low slice emittance is considered. The beam is compressed weakly in the bunch compressors and the current is increased by eSASE setup at the entrance of the undulator line. It is shown by numerical studies that such approach allows to reduce harmful collective effects in the bunch compressors and in the transport line. Simulations of FEL physics confirm the possibility to obtain a high level of SASE radiation at the ultra-hard photon energy level of 100 keV.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP060
About •	paper received ※ 19 August 2019 paper accepted ※ 25 August 2019 issue date ※ 05 November 2019
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TUP061	Super-X: Simulations for Extremely Hard X-Ray Generation With Short Period Superconducting Undulators for the European XFEL	FEL, undulator, electron, simulation	191
	S. Serkez, G. Geloni, S. Karabekyan, Y. Li, T. Tanikawa, S. Tomin, F. Wolff-Fabris EuXFEL, Schenefeld, Germany C. Boffo Bilfinger Noell GmbH, Wuerzburg, Germany S. Casalbuoni KIT, Eggenstein-Leopoldshafen, Germany M. Dohlus, E. Schneidmiller, M.V. Yurkov, I. Zagorodnov DESY, Hamburg, Germany A. Trebushinin BINP, Novosibirsk, Russia
	The European XFEL is a high-repetition multi-user facility with nominal photon energy range covering almost 3 orders of magnitude: 250 eV - 25 keV. In this work we explore the possibility to extend the photon energy range of the facility up to 100 keV via combination of superconducting undulator technology, period doubling and harmonic lasing, thus allowing for excellent tunability. To this purpose, we propose a dedicated FEL line, discuss its overall concept and provide analytical and numerical estimations of its expected performance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP061
About •	paper received ※ 20 August 2019 paper accepted ※ 25 August 2019 issue date ※ 05 November 2019
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TUP062	Two Colors at the SASE3 Line of the European XFEL: Project Scope and First Measurements	FEL, electron, experiment, radiation	195
	S. Serkez, G. Geloni, N. Gerasimova, J. Grünert, S. Karabekyan, A. Koch, J. Laksman, Th. Maltezopoulos, T. Mazza, M. Meyer, S. Tomin EuXFEL, Schenefeld, Germany W. Decking, L. Fröhlich, V. Kocharyan, Y.A. Kot, E. Saldin, E. Schneidmiller, M. Scholz, M.V. Yurkov, I. Zagorodnov DESY, Hamburg, Germany M. Huttula University of Oulu, Oulu, Finland E. Kukk University of Turku, Turku, Finland
	The European XFEL is a high-repetition rate facility that generates high-power SASE radiation pulses in three beamlines. A joint upgrade project, with Finnish universities, to equip the SASE3 beamline with a chicane has been recently approved to generate two SASE pulses with different photon energies and temporal separation. In this work we report the status of the project, its expected performance, and recent experimental results. Additionally, we discuss methods to diagnose the properties of the generated radiation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP062
About •	paper received ※ 20 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019
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TUP063	Physical Design and FEL Performance Study for FEL-III Beamline of SHINE	FEL, undulator, wakefield, electron	199
	N. Huang SINAP, Shanghai, People’s Republic of China H.X. Deng, B. Liu, D. Wang SARI-CAS, Pudong, Shanghai, People’s Republic of China
	The first hard X-ray free electron laser (XFEL) facility in China, the Shanghai High-Repetition-Rate XFEL and Extreme Light Facility (SHINE), is under construction, which allows for generating X-ray pulses in the photon energy range from 3 keV to 25 keV. To produce X-ray pulses with photon energy up to 25 keV, FEL-III undulator line of SHINE employs superconducting undulators. However, the smaller gap of the superconducting undulator poses serious wakefield effect reducing the FEL power, compared to the normal planar undulator. For a setup design optimization, the design and performance of the FEL-III undulator line are presented using start-to-end beam simulations at self-amplified spontaneous emission (SASE) and self-seeding mode. The wakefield impact on FEL performance is then investigated. A linear undulator tapering technique is adopted for recovering the FEL power to the non-wakefield level.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP063
About •	paper received ※ 19 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	laser, FEL, electron, bunching	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	FEL, undulator, simulation, electron	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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TUP092	XFEL Third Harmonic Statistics Measurement at LCLS	FEL, undulator, experiment, radiation	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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TUD02	Application of Infrared FEL Oscillators for Producing Isolated Attosecond X-Ray Pulses via High-Harmonic Generation in Rare Gases	FEL, cavity, laser, experiment	272
	R. Hajima, K. Kawase, R. Nagai QST, Tokai, Japan Y. Hayakawa, T. Sakai, Y. Sumitomo LEBRA, Funabashi, Japan T. Miyajima, M. Shimada KEK, Ibaraki, Japan H. Ohgaki, H. Zen Kyoto University, Kyoto, Japan
	Funding: Quantum Leap Flagship Program (MEXT Q-LEAP) High harmonic generation (HHG) in rare gases is now becoming a common technology to produce attosecond pulses in VUV wavelengths. So far HHG sources have been realized by femtosecond solid-state lasers, not FELs. We propose a FEL-driven HHG source to explore attosecond pulses at photon energies above 1 keV with a MHz-repetition, which is difficult with solid-state lasers [1]. A research program has been launched to establish technologies for the FEL-HHG, which covers generation and characterization of few-cycle IR pulses in a FEL oscillator, stacking of FEL pulses in an external cavity, and a seed laser for stabilization of carrier-envelope phase in a FEL oscillator. In this talk, we present the scheme of FEL-HHG and the status of the research program. [1] R. Hajima and R. Nagai, Phys. Rev. Lett. 119, 204802 (2017)
	Slides TUD02 [8.995 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUD02
About •	paper received ※ 23 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019
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WEP006	A PolariX TDS for the FLASH2 Beamline	emittance, electron, FEL, optics	328
	F. Christie, J. Rönsch-Schulenburg, M. Vogt DESY, Hamburg, Germany
	Transverse Deflecting RF-Structures (TDS) are successfully used for longitudinal diagnostic purposes at many Free-Electron Lasers (FEL) (LCLS, FLASH, EU-XFEL, FERMI). Moreover, by installing a TDS downstream of the FEL undulators and placing the measurement screen in a dispersive section, the temporal photon pulse structure can be estimated, as was demonstrated at LCLS and sFLASH. Here we describe the installation of a variable polarization X-band structure (PolariX TDS [1]) downstream of the FLASH2 undulators. The installation of such a TDS enables longitudinal phase space measurements and photon pulse reconstructions, as well as slice emittance measurements in both planes using the same cavity due to the unique variable polarization of the PolariX TDS. [1] P. Craievich et al., "Status of the PolariX-TDS Project", in Proc. IPAC’18, Vancouver, Canada (2018)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP006
About •	paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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WEP015	Electro-Optical Bunch Length Detection at the European XFEL	laser, electron, FEL, detector	360
	B. Steffen, M.K. Czwalinna, C. Gerth DESY, Hamburg, Germany S. Bielawski, C. Evain, E. Roussel, C. Szwaj PhLAM/CERCLA, Villeneuve d’Ascq Cedex, France
	The electro-optical bunch length detection system based on electro-optic spectral decoding has been installed and is being commissioned at the European XFEL. The system is capable of recording individual longitudinal bunch profiles with sub-picosecond resolution at a bunch repetition rate of 1.13MHz . Bunch lengths and arrival times of entire bunch trains with single-bunch resolution have been measured as well as jitter and drifts for consecutive bunch trains. In addition, we are testing a second electro-optical detection strategy, the so-called photonic time-stretching, which consists of imprinting the electric field of the bunch onto a chirped laser pulse, and then "stretching" the output pulse by optical means. As a result, we obtain is a slowed down "optical replica" of the bunch shape, which can be recorded using a photodiode and GHz-range acquisition. These tests are performed in parallel with the existing spectral decoding technique based on a spectrometer in order to allow a comparative study. In this paper, we present first results for both detection strategies from electron bunches after the second bunch compressor of the European XFEL.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP015
About •	paper received ※ 24 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019
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WEP030	All-Fiber Photonic, Ultralow-Noise, Robust Optical and Microwave Signal Generators for FELs and UED	laser, timing, radiation, operation	382
	J. Kim, I.J. Jeon, D. Kim, D. Kwon KAIST, Daejeon, Republic of Korea
	Funding: National Research Foundation of Korea (2018R1A2B3001793) and Korea Atomic Energy Research Institute Optical timing and synchronization is becoming a more important and essential element for ultrafast X-ray and electron science. As a result, compact, ultralow-noise, mechanically robust and long-term stable optical and microwave signal generators are highly desirable for future XFELs and UEDs. Here we show that the combination of mode-locked fiber laser and fiber delay-based stabilization method enables the generation of ultralow-noise optical and microwave signals. We show that all-PM fiber lasers can provide excellent mechanical robustness: stable laser operation over >1 hour is maintained even in continuous 1.5 g vibrations [1]. Using a compactly packaged fiber delay as the timing reference, we could stabilize the repetition-rate phase noise of mode-locked lasers down to -100 dBc/Hz and -160 dBc/Hz at 1 Hz and 10 kHz offset frequency, respectively, at 1 GHz carrier, which corresponds to only 1.4 fs rms absolute timing jitter [1 Hz - 100 kHz] [2]. With DDS-based electronics, low-noise and agile microwave frequency synthesizer was also realized [3]. This new class of photonic signal generator will be suitable for master oscillators in various accelerator-based light sources. [1] D. Kim et al., Opt. Lett. 44, 1068 (2019) [2] D. Kwon et al., Opt. Lett. 42, 5186 (2017) [3] J. Wei et al., Photon. Res. 6, 12 (2018)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP030
About •	paper received ※ 05 September 2019 paper accepted ※ 22 October 2019 issue date ※ 05 November 2019
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WEP038	Commissioning and Stability Studies of the SwissFEL Bunch-Separation System	FEL, electron, operation, kicker	404
	M. Paraliev, S. Dordevic, R. Ganter, C.H. Gough, N. Hiller, R.A. Krempaská, D. Voulot PSI, Villigen PSI, Switzerland
	SwissFEL is a linear electron accelerator based, X-ray Free Electron Laser at the Paul Scherrer Institute, Switzerland. It is a user oriented facility capable of producing short, high brightness X-ray pulses covering the spectral range from 1 to 50 Å. SwissFEL is designed to run in two electron bunch mode in order to serve simultaneously two experimental beamline stations (hard and soft X-ray one) at its full repetition rate. Two closely spaced (28 ns) electron bunches are accelerated in one RF macro pulse up to 3 GeV. A high stability resonant kicker system and a Lambertson septum magnet are used to separate the bunches and to send them to their respective beamlines. With the advancement of the construction of the second beamline (Athos) the bunch-separation system was successfully commissioned. In order to confirm that the beam separation process is fully transparent a stability study of the electron beam and the free electron laser in the main beamline (Aramis) was done.
	Poster WEP038 [0.945 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP038
About •	paper received ※ 19 August 2019 paper accepted ※ 25 August 2019 issue date ※ 05 November 2019
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WEP076	A Superconducting Undulator With Variable Polarization Direction for the European FEL	undulator, FEL, polarization, radiation	499
	Y. Li EuXFEL, Hamburg, Germany R. Rossmanith DESY, Hamburg, Germany
	In the SASE3 beam line at the European XFEL a planar undulator produces linearly polarized radiation. In order to obtain a circularly polarized radiation an afterburner will be installed to produce coherent radiation with variable polarization. Recently Argonne National Lab developed a super conductive undulator (called SCAPE) for a storage ring which allows to change polarization direction and field strength without moving mechanically the undulator parts. In this paper it is investigated if a similar device could be useful for an FEL. Such device is also a possible choice for the future undulator beam lines where circular and variable polarization are required.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP076
About •	paper received ※ 19 August 2019 paper accepted ※ 17 September 2019 issue date ※ 05 November 2019
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WEP079	Effect of Heat Load on Cryo-Cooled Monochromators at the European X-Ray Free-Electron Laser: Simulations and First Experimental Observations	FEL, experiment, simulation, electron	502
	I. Petrov, U. Boesenberg, M. Dommach, J. Eidam, J. Hallmann, K. Kazarian, C. Kim, W. Lu, A. Madsen, J. Möller, M. Reiser, L. Samoylova, R. Shayduk, H. Sinn, V. Sleziona, A. Zozulya EuXFEL, Schenefeld, Germany J.W.J. Anton, S.P. Kearney, D. Shu ANL, Lemont, Illinois, USA X. Dong SINAP, Shanghai, People’s Republic of China X. Dong SARI-CAS, Pudong, Shanghai, People’s Republic of China
	European XFEL (EuXFEL) generates high-intensity ultra-short pulses at MHz repetition rate. At hard X-ray instruments, cryo-cooled silicon monochromators are used to reduce pulse bandwidth. Here, first experimental observations during commissioning of a cryo-cooled monochromator at Materials Imaging and Dynamics (MID) instrument are presented and compared with heat flow simulations. A thermal relaxation time is estimated and compared with arrival time interval between pulses. This provides the repetition rate tolerable for stable operation of monochromator.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP079
About •	paper received ※ 19 August 2019 paper accepted ※ 25 August 2019 issue date ※ 05 November 2019
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WEP089	Pulse Energy Measurement at the SXFEL	FEL, undulator, electron, radiation	521
	Z.P. Liu, H.X. Deng, C. Feng, B. Liu, D. Wang, L.Y. Yu SINAP, Shanghai, People’s Republic of China
	The test facility is going to generate 8.8 nm FEL radiation using an 840 MeV electron linac passing through the two-stage cascaded HGHG-HGHG or EEHG-HGHG (high-gain harmonic generation, echo-enabled harmonic generation) scheme. Several methods have been developed to measure the power of pulse. The responsivity of silicon photodiode having no loss in the entrance window. Silicon photodiode reach saturates at the SXFEL. In this work, we simulated the attenuator transmittance for different thicknesses. We also show the preparations of the experiment results at the SXFEL .
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP089
About •	paper received ※ 20 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019
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WEP095	The Athos Soft X-Ray Beamlines at SwissFEL	FEL, undulator, operation, electron	535
	R. Follath, U. Flechsig, L. Patthey, U.H. Wagner PSI, Villigen PSI, Switzerland
	After the successful start of the hard X-ray FEL at SwissFEL in 2016, the soft X-ray FEL ATHOS at SwissFEL is expected to deliver the first beam by end of 2019. This contribution describes the beamlines attached to the FEL and reports on the status and plans for this soft X-ray facility. The ATHOS facility will operate three end stations. Two stations are already defined and are currently in the design and construction phase whereas the third station will be defined in the future. The first station (AMO) is dedicated to Atomic and Molecular physics as well as nonlinear spectroscopy. It is expected to get light in mid 2020. The second station (Furka) is for condensed matter physics. The beamline consists of a grating monochromator and distributes the beam downstream of the grating chamber by means of horizontal deflecting mirrors. Pink and monochromatic beam operation is foreseen at all branches. The monochromator uses variable line-spacing gratings on spherical substrates with a variable included angle and operates without an entrance slit. Its mechanics is based on the SX-700 design, but with the grating facing up and the mirror facing down. The installation of the beamline will start in August 2019.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP095
About •	paper received ※ 19 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019
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WEP098	Advanced Operational Models of the Apple X Undulator	undulator, operation, polarization, site	541
	X. Liang, M. Calvi, C. Kittel, T. Schmidt PSI, Villigen PSI, Switzerland N.J. Sammut University of Malta, Information and Communication Technology, Msida, Malta
	Athos is a new soft X-ray beamline at SwissFEL, where the Apple X type undulators will be equipped. These devices are flexible to produce light in different polarization modes. An adequate magnetic field model is required for the operation of undulator. The undulator deflection parameter K and its gradient are calculated starting from the Fourier series of the magnetic field. In the classical parallel and anti-parallel operational modes - respectively elliptical and linear modes, the variation of the magnetic field as well as its parameters are evaluated by computer modeling. The results are compared to the magnetic measurements of the first Apple X prototype.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP098
About •	paper received ※ 27 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019
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WED01	Experience with Short-Period, Small Gap Undulators at the SwissFEL Aramis Beamline	undulator, alignment, FEL, electron	564
	T. Schmidt, M. Aiba, A.D. Alarcon, C. Arrell, S. Bettoni, M. Calvi, A. Cassar, E. Ferrari, R. Follath, R. Ganter, N. Hiller, P.N. Juranič, C. Kittel, F. Löhl, E. Prat, S. Reiche, T. Schietinger, D. Voulot, U.H. Wagner PSI, Villigen PSI, Switzerland N.J. Sammut University of Malta, Faculty of Engineering, Msida, Malta
	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.
	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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WED02	Absorbed Radiation Doses on the European XFEL Undulator Systems During Early User Experiments	undulator, operation, FEL, radiation	569
	F. Wolff-Fabris, J. Pflüger, H. Sinn EuXFEL, Schenefeld, Germany W. Decking, D. Nölle, F. Schmidt-Föhre DESY, Hamburg, Germany A. Hedqvist, F. Hellberg Stockholm University, Stockholm, Sweden
	The EuXFEL is a FEL user facility based on a superconducting accelerator with high duty cycle. Three gap movable SASE Undulator Systems using hybrid NdFeB permanent magnet segments are operated. Radiation damage on undulators can impact the quality of the SASE process and ultimately threaten user operation. We observed [1] in the commissioning phase doses up to 4 kGy and 3% demagnetization effect in a diagnostic undulator. Currently all SASE systems are used for user photon delivery and in this work we present characteristics of the absorbed radiation doses on undulators under stable conditions. Doses on the upstream segments are found to be originated in the event of occasional high energy electron losses. In contrast, towards the downstream end of a SASE system, individual segments show persistent absorbed doses which are proportional to the transmitted charge and are dominated by low energy radiation. This energy-dependence depiction shall result in distinct radiation damage thresholds for individual segments. Portable magnetic flux measurement systems allow in-situ tunnel assessment of undulator properties in order to estimate radiation dose limits for future user operation. [1] F. Wolff-Fabris et al., J. of Phys. - Conf. Series 1067, 032025 (2018)
	Slides WED02 [7.344 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WED02
About •	paper received ※ 19 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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THP012	Compact FEL-Driven Inverse Compton Scattering Gamma-Ray Source	electron, FEL, undulator, radiation	617
	M. Placidi, G. Penn LBNL, Berkeley, California, USA S. Di Mitri Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy C. Pellegrini UCLA, Los Angeles, California, USA C. Pellegrini SLAC, Menlo Park, California, USA
	We explore the feasibility of a compact source of quasi-monochromatic, multi-MeV gamma-rays based on Inverse Compton Scattering (ICS) from a high intensity ultra-violet (UV) beam generated in a free-electron laser by the electron beam itself.[1] This scheme introduces a stronger relationship between the energy of the scattered photons and that of the electron beam, resulting in a device much more compact than a classic ICS for a given scattered energy. The same electron beam is used to produce gamma-rays in the 10-20 MeV range and UV radiation in the 10-15 eV range, in a ~4x22 m2 footprint system. [1] M. Placidi et al., NIM A 855 (2017) 55-60.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP012
About •	paper received ※ 19 August 2019 paper accepted ※ 25 August 2019 issue date ※ 05 November 2019
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THP047	Laser-Driven Compact Free Electron Laser Development at ELI-Beamlines	laser, electron, FEL, undulator	680
	A.Y. Molodozhentsev Czech Republic Academy of Sciences, Institute of Physics, Prague, Czech Republic J.T. Green, J. Hawke, M. Kaur, D. Kocon, G. Korn, K.O. Kruchinin ELI-BEAMS, Prague, Czech Republic A.R. Maier University of Hamburg, Hamburg, Germany
	Funding: Advanced research using high-intensity laser produced photons and particles (CZ.02.1.01/0.0/0.0/16₀19/0000789) from the European Regional Development Fund. The ELI-Beamlines Centre, located near Prague (Czech Republic) is an international user facility for fundamental and applied research. Using the optical parametric chirped-pulse amplification (OPCPA) technique, the ELI-Beamlines laser system will provide the laser pulse energy up to 10 Joules with the repetition rate up to 25 Hz. Combination of new laser development with constant improvement of the LWFA electron beam parameters has great potential in future development of the compact high repetition rate Free Electron Laser. The LWFA-driven FEL project, called "LUIS", is currently under preparation at ELI-Beamlines in collaboration with the University of Hamburg. The goal of the project is the improvement of the electron beam parameters in order to demonstrate the amplification and saturation of the SASE-FEL photon power in a single unit of the FEL undulator. A successful realization of the LUIS project will open a way to a next generation of laser-driven X-FELs. An overview of the LUIS project including design features and a description of all instrumentations used to characterize the laser, plasma, electron beam, photon generation will be presented in frame of this report.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP047
About •	paper received ※ 15 August 2019 paper accepted ※ 16 September 2019 issue date ※ 05 November 2019
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THP066	XARA: X-Band Accelerator for Research and Applications	FEL, electron, undulator, linac	715
	D.J. Dunning, L.S. Cowie, J.K. Jones STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom L.S. Cowie, J.K. Jones Cockcroft Institute, Warrington, Cheshire, United Kingdom L.S. Cowie Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
	XARA (X-band Accelerator for Research and Applications) is a proposal for a compact ~1 GeV/c accelerator to produce attosecond light pulses in the EUV to soft X-ray region. It is under consideration as a potential future upgrade to the CLARA facility at Daresbury Laboratory, utilising high-performance X-band RF technology to increase the electron beam momentum from 250 MeV/c. Emerging techniques for generating single-cycle undulator light [1] would give access to attosecond timescales, enabling studies of ultra-fast dynamics, while also being very compact. XARA would also enhance the existing capabilities for accelerator science R&D by incorporating X-band development and increasing the electron beam momentum for novel acceleration studies. [1] Alan Mak et al., Rep. Prog. Phys. 82 025901 (2019)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP066
About •	paper received ※ 20 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019
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THP071	Progress in High Power High Brightness Double Bunch Self-Seeding at LCLS-II	FEL, kicker, undulator, electron	726
	A. Halavanau, F.-J. Decker, Y. Ding, C. Emma, Z. Huang, A.K. Krasnykh, J. Krzywiński, A.A. Lutman, G. Marcus, A. Marinelli, A. Ratti, D. Zhu SLAC, Menlo Park, California, USA C. Pellegrini UCLA, Los Angeles, California, USA
	Funding: Work supported by the U.S. Department of Energy Contract No. DE-AC02-76SF00515. We have previosuly shown that we can generate near TW, 15 fs duration, near transform limited X-ray pulses in the 4 to 8 keV photon energy range using the LCLS-II copper linac, two electron bunches, a 4-crystal monochromator/delay line and a fast transverse bunch kicker. The first bunch generates a strong seeding X-ray signal, and the second bunch, initially propagating off-axis, interacts with the seed in a tapered amplifier undulator, where it propagates on axis. In this paper, we investigate the design of the 4-crystal monochromator, acting also as an X-ray delay system, and of the fast kicker, in preparation of the implementation of the system in LCLS-II.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP071
About •	paper received ※ 20 August 2019 paper accepted ※ 26 August 2019 issue date ※ 05 November 2019
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THP081	PolFEL — New Facility in Poland	FEL, electron, radiation, experiment	746
	K. Szamota-Leandersson, P.J. Czuma, P. Krawczyk, J. Krzywiński, R. Nietubyć, M. Staszczak, J. Szewiński NCBJ, Świerk/Otwock, Poland W. Bal, J. Poznański IBB, Warsaw, Poland A. Bartnik, H. Fiedorowicz, K. Janulewicz, N. Palka MUT, Warsaw, Poland J.K. Sekutowicz DESY, Hamburg, Germany
	Funding: European Regional Development Fund ¿ Smart Growth In 2018 funds for the free electron laser PolFEL project was received. PolFEL will be driven by cw operating superconducting linac with SRF electron source. PolFEL will generate THz, IR and VIS-VUV radiation in two beamlines, respectively. In the first one, with electron beam below 80 MeV, the THz/IR radiation source will be generated in permanent magnet supper-radiant undulator, delivering THz radiation in 0.5 to 6 THz range. In the second beam line with up to 180 MeV electrons, the VIS/VUV radiation will be generated in the SASE undulator delivering coherent radiation down to 55 nm wavelength in the third harmonic, with sub-100 fs pulse duration. At the moment, four end-stations are planned. Experiments will be equipped with dedicated Pump-Probe spectrometer system as well. In the project, also, the Inverse Compton Scattering experiment is planned. In this contribution we will describe PolFEL facility in more details.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP081
About •	paper received ※ 29 August 2019 paper accepted ※ 18 September 2019 issue date ※ 05 November 2019
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THD03	FEL Optimization: From Model-Free to Model-Dependent Approaches and ML Prospects	FEL, controls, operation, undulator	762
	S. Tomin, G. Geloni EuXFEL, Schenefeld, Germany M. Scholz DESY, Hamburg, Germany
	Users beam-time at modern FEL sources is an extremely valuable commodity. Moreover, maximization of FEL up-time must always be performed accounting for stringent requirements on the photon pulse characteristics. These may vary widely depending on the users requests, which poses issues to parallel operation of high-repetition rate facilities like the European XFEL. Therefore, both model-free or model-dependent optimization schemes, where the model might be given, or provided by machine-learning approaches, are of high importance for the overall efficiency of FEL facilities. In this contribution, we review our previous activities and we report on current efforts and progress in FEL optimization schemes at the European XFEL. Finally, we provide an outlook on future developments.
	Slides THD03 [13.636 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THD03
About •	paper received ※ 21 August 2019 paper accepted ※ 12 September 2019 issue date ※ 05 November 2019
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FRA01	FEL Operation at the European XFEL Facility	FEL, operation, kicker, electron	766
	D. Nölle DESY, Hamburg, Germany
	The European XFEL is a SASE FEL based user facility in the metropole region of Hamburg providing hard and soft X-ray photons with extremely high brilliance. The three FEL lines are operated simultaneously and are powered by a superconducting LINAC based on TESLA technology. Average power levels of up to several W have been demonstrated as well for soft and hard X-rays and can be requested by user experiments on day by day basis. The contribution will report on the results of the commissioning within the last two years as well as on the transition to user operation. Typical operation conditions for parallel operation of 3 SASE lines will be discussed. The perspective for the operation with an extended photon energy range, as well as for full power operation with up to 27000 pulses per second will be presented.
	Slides FRA01 [27.196 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-FRA01
About •	paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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FRA02	LCLS-II - Status and Upgrades	linac, undulator, electron, operation	772
	A. Brachmann, M. Dunham, J.F. Schmerge SLAC, Menlo Park, California, USA
	Funding: This work is supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-76SF00515. The LCLS-II FEL is under construction at the SLAC National Accelerator Laboratory. This facility is based on a superconducting accelerator, providing a cw e^- beam of 4 GeV at ~1 MHz. This beam drives two variable gap undulator (VGU) beam lines to generate photons in the soft and hard X-ray regime. High repetition rate photon beams will be available up to ~5 keV. The normal conducting accelerator will remain in operation, delivering milli-joule pulses up to ~20 keV for LCLS science. We anticipate to start the LCLS user program in the spring of 2020 using the new undulator systems. Superconducting accelerator operation will start in 2021 and will achieve full design-performance over the course of several years. Approximately a quarter of the superconducting accelerator is installed now and the associated cryoplant construction is near completion. The VGU systems will be installed and ready for beam delivery in early 2020. We will report on the project status, commissioning and ramp-up plans to achieve design performance and discuss plans to take advantage of the new facilities potential including our longer term strategy to extend the capability of SLAC’s LCLS FEL facility.
	Slides FRA02 [24.207 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-FRA02
About •	paper received ※ 04 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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Paper

Title

Other Keywords

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TUB01

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

laser, FEL, electron, free-electron-laser

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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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUB01

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TUP053

An Investigation of Possible Non-Standard Photon Statistics in a Free-Electron Laser I: Experiment

FEL, experiment, cavity, radiation

161

J.-W. Park
University of Hawaii, Honolulu,, USA
K.-J. Kim, R.R. Lindberg
ANL, Lemont, Illinois, USA

Funding: Work supported by U.S. DOE, Office of Science, Office of BES, under Award No. DE-SC0018428.
It was reported that the photon statistics of the seventh coherent spontaneous harmonic radiation of the MARK III FEL was sub-Poissonian [1], which concludes that Fano factor F (the ratio of photon number variance to the average photon number) is less than unity. Whether FEL light exhibits such non-standard behavior is an important issue; if it does, our understanding of the FEL needs to be radically modified. In this paper, we re-examine the analyses of experimental data in Ref. [1]. We find that the observed value of F could be explained within the standard FEL theory if one combines the detector dead time effect with photon clustering arising from the FEL gain. We propose an improved experiment for a more definitive measurement of the FEL photon statistics.
[1] T. Chen and J.M. Madey, J. Phys. Rev. Lett. 86, 5906 (2001).

Poster TUP053 [0.929 MB]

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TUP054

An Investigation of Possible Non-Standard Photon Statistics in a Free-Electron Laser II: Theory

electron, FEL, radiation, laser

165

J.-W. Park
University of Hawaii, Honolulu,, USA
K.-J. Kim, R.R. Lindberg
ANL, Lemont, Illinois, USA
K.-J. Kim
University of Chicago, Chicago, Illinois, USA

Funding: Work supported by U.S. DOE, Office of Science, Office of BES, under Award No. DE-SC0018428.
In this paper we explore whether we can at present find a theoretical basis for non-standard, sub-Poissonian photon statistics in the coherent spontaneous harmonic radiation of an FEL as was claimed to have been measured with the Mark III FEL [1]. We develop a one dimensional quantum FEL oscillator model of the harmonic radiation in the linear gain regime to calculate the photon statistics. According to our study, it seems unlikely that the photon statistics for an FEL oscillator starting from the noise could be sub-Poissonian.
[1] T. Chen and J.M. Madey, J. Phys. Rev. Lett. 86, 5906 (2001).

Poster TUP054 [0.386 MB]

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paper received ※ 21 August 2019 paper accepted ※ 16 September 2019 issue date ※ 05 November 2019

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TUP056

Feasibility Studies of the 100 keV Undulator Line of the European XFEL

undulator, FEL, electron, laser

172

E. Schneidmiller, V. Balandin, W. Decking, M. Dohlus, N. Golubeva, D. Nölle, M.V. Yurkov, I. Zagorodnov
DESY, Hamburg, Germany
G. Geloni, Y. Li, S. Molodtsov, J. Pflüger, S. Serkez, H. Sinn, T. Tanikawa, S. Tomin
EuXFEL, Schenefeld, Germany

The European XFEL is a multi-user X-ray FEL facility based on superconducting linear accelerator. Presently, three undulators (SASE1, SASE2, SASE3) deliver high-brightness soft- and hard- X-ray beams for users. There are two empty undulator tunnels that were originally designed to operate with spontaneous radiators. We consider instead a possible installation of two FEL undulators. One of them (SASE4) is proposed for the operation in ultrahard X-ray regime, up to the photon energy of 100 keV. In this contribution we present the results of the first feasibility studies of this option.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP056

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

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TUP058

First Characterization of the Photon Beam at the European XFEL in July, 2017

FEL, radiation, electron, undulator

180

V. Balandin, B. Beutner, F. Brinker, W. Decking, M. Dohlus, L. Fröhlich, U. Jastrow, R. Kammering, T. Limberg, D. Nölle, M. Scholz, A.A. Sorokin, K.I. Tiedtke, M.V. Yurkov, I. Zagorodnov
DESY, Hamburg, Germany
U. Boesenberg, W. Freund, J. Grünert, A. Koch, N.G. Kujala, J. Liu, Th. Maltezopoulos, M. Messerschmidt, I. Petrov, L. Samoylova, H. Sinn
EuXFEL, Schenefeld, Germany

North branch of the European XFEL, SASE1, produced first light on May 3rd, 2017, and XFEL operation has been gradually improved then. First characterization of the photon beam has been performed in July / August 2017, just before an official starting date of user experiments (September 1st, 2017). Energy of the electron beam was 14 GeV, bunch charge was 500 pC, photon energy was 9.3 keV. With photon diagnostics available at that time (X-ray gas monitor (XGM) and FEL imager) we measured the gain curve and traced evolution of the FEL radiation mode along the undulator. An important conclusion is that experimental results demonstrate reasonable agreement with baseline parameters. Developed techniques of the photon beam characterization also provided solid base for identification of the problems and means for improving SASE FEL tuning and operation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP058

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

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TUP060

An Advanced Compression Option for the European XFEL

electron, undulator, laser, FEL

187

I. Zagorodnov, M. Dohlus, E. Schneidmiller, M.V. Yurkov
DESY, Hamburg, Germany

An advanced compression scheme which allows to obtain a high peak current while preserving the low slice emittance is considered. The beam is compressed weakly in the bunch compressors and the current is increased by eSASE setup at the entrance of the undulator line. It is shown by numerical studies that such approach allows to reduce harmful collective effects in the bunch compressors and in the transport line. Simulations of FEL physics confirm the possibility to obtain a high level of SASE radiation at the ultra-hard photon energy level of 100 keV.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP060

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paper received ※ 19 August 2019 paper accepted ※ 25 August 2019 issue date ※ 05 November 2019

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TUP061

Super-X: Simulations for Extremely Hard X-Ray Generation With Short Period Superconducting Undulators for the European XFEL

FEL, undulator, electron, simulation

191

S. Serkez, G. Geloni, S. Karabekyan, Y. Li, T. Tanikawa, S. Tomin, F. Wolff-Fabris
EuXFEL, Schenefeld, Germany
C. Boffo
Bilfinger Noell GmbH, Wuerzburg, Germany
S. Casalbuoni
KIT, Eggenstein-Leopoldshafen, Germany
M. Dohlus, E. Schneidmiller, M.V. Yurkov, I. Zagorodnov
DESY, Hamburg, Germany
A. Trebushinin
BINP, Novosibirsk, Russia

The European XFEL is a high-repetition multi-user facility with nominal photon energy range covering almost 3 orders of magnitude: 250 eV - 25 keV. In this work we explore the possibility to extend the photon energy range of the facility up to 100 keV via combination of superconducting undulator technology, period doubling and harmonic lasing, thus allowing for excellent tunability. To this purpose, we propose a dedicated FEL line, discuss its overall concept and provide analytical and numerical estimations of its expected performance.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP061

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

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TUP062

Two Colors at the SASE3 Line of the European XFEL: Project Scope and First Measurements

FEL, electron, experiment, radiation

195

S. Serkez, G. Geloni, N. Gerasimova, J. Grünert, S. Karabekyan, A. Koch, J. Laksman, Th. Maltezopoulos, T. Mazza, M. Meyer, S. Tomin
EuXFEL, Schenefeld, Germany
W. Decking, L. Fröhlich, V. Kocharyan, Y.A. Kot, E. Saldin, E. Schneidmiller, M. Scholz, M.V. Yurkov, I. Zagorodnov
DESY, Hamburg, Germany
M. Huttula
University of Oulu, Oulu, Finland
E. Kukk
University of Turku, Turku, Finland

The European XFEL is a high-repetition rate facility that generates high-power SASE radiation pulses in three beamlines. A joint upgrade project, with Finnish universities, to equip the SASE3 beamline with a chicane has been recently approved to generate two SASE pulses with different photon energies and temporal separation. In this work we report the status of the project, its expected performance, and recent experimental results. Additionally, we discuss methods to diagnose the properties of the generated radiation.

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TUP063

Physical Design and FEL Performance Study for FEL-III Beamline of SHINE

FEL, undulator, wakefield, electron

199

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

The first hard X-ray free electron laser (XFEL) facility in China, the Shanghai High-Repetition-Rate XFEL and Extreme Light Facility (SHINE), is under construction, which allows for generating X-ray pulses in the photon energy range from 3 keV to 25 keV. To produce X-ray pulses with photon energy up to 25 keV, FEL-III undulator line of SHINE employs superconducting undulators. However, the smaller gap of the superconducting undulator poses serious wakefield effect reducing the FEL power, compared to the normal planar undulator. For a setup design optimization, the design and performance of the FEL-III undulator line are presented using start-to-end beam simulations at self-amplified spontaneous emission (SASE) and self-seeding mode. The wakefield impact on FEL performance is then investigated. A linear undulator tapering technique is adopted for recovering the FEL power to the non-wakefield level.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP063

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paper received ※ 19 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

laser, FEL, electron, bunching

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.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP083

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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

FEL, undulator, simulation, electron

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.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP087

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

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TUP092

XFEL Third Harmonic Statistics Measurement at LCLS

FEL, undulator, experiment, radiation

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.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP092

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

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TUD02

Application of Infrared FEL Oscillators for Producing Isolated Attosecond X-Ray Pulses via High-Harmonic Generation in Rare Gases

FEL, cavity, laser, experiment

272

R. Hajima, K. Kawase, R. Nagai
QST, Tokai, Japan
Y. Hayakawa, T. Sakai, Y. Sumitomo
LEBRA, Funabashi, Japan
T. Miyajima, M. Shimada
KEK, Ibaraki, Japan
H. Ohgaki, H. Zen
Kyoto University, Kyoto, Japan

Funding: Quantum Leap Flagship Program (MEXT Q-LEAP)
High harmonic generation (HHG) in rare gases is now becoming a common technology to produce attosecond pulses in VUV wavelengths. So far HHG sources have been realized by femtosecond solid-state lasers, not FELs. We propose a FEL-driven HHG source to explore attosecond pulses at photon energies above 1 keV with a MHz-repetition, which is difficult with solid-state lasers [1]. A research program has been launched to establish technologies for the FEL-HHG, which covers generation and characterization of few-cycle IR pulses in a FEL oscillator, stacking of FEL pulses in an external cavity, and a seed laser for stabilization of carrier-envelope phase in a FEL oscillator. In this talk, we present the scheme of FEL-HHG and the status of the research program.
[1] R. Hajima and R. Nagai, Phys. Rev. Lett. 119, 204802 (2017)

Slides TUD02 [8.995 MB]

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paper received ※ 23 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019

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WEP006

A PolariX TDS for the FLASH2 Beamline

emittance, electron, FEL, optics

328

F. Christie, J. Rönsch-Schulenburg, M. Vogt
DESY, Hamburg, Germany

Transverse Deflecting RF-Structures (TDS) are successfully used for longitudinal diagnostic purposes at many Free-Electron Lasers (FEL) (LCLS, FLASH, EU-XFEL, FERMI). Moreover, by installing a TDS downstream of the FEL undulators and placing the measurement screen in a dispersive section, the temporal photon pulse structure can be estimated, as was demonstrated at LCLS and sFLASH. Here we describe the installation of a variable polarization X-band structure (PolariX TDS [1]) downstream of the FLASH2 undulators. The installation of such a TDS enables longitudinal phase space measurements and photon pulse reconstructions, as well as slice emittance measurements in both planes using the same cavity due to the unique variable polarization of the PolariX TDS.
[1] P. Craievich et al., "Status of the PolariX-TDS Project", in Proc. IPAC’18, Vancouver, Canada (2018)

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

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WEP015

Electro-Optical Bunch Length Detection at the European XFEL

laser, electron, FEL, detector

360

B. Steffen, M.K. Czwalinna, C. Gerth
DESY, Hamburg, Germany
S. Bielawski, C. Evain, E. Roussel, C. Szwaj
PhLAM/CERCLA, Villeneuve d’Ascq Cedex, France

The electro-optical bunch length detection system based on electro-optic spectral decoding has been installed and is being commissioned at the European XFEL. The system is capable of recording individual longitudinal bunch profiles with sub-picosecond resolution at a bunch repetition rate of 1.13MHz . Bunch lengths and arrival times of entire bunch trains with single-bunch resolution have been measured as well as jitter and drifts for consecutive bunch trains. In addition, we are testing a second electro-optical detection strategy, the so-called photonic time-stretching, which consists of imprinting the electric field of the bunch onto a chirped laser pulse, and then "stretching" the output pulse by optical means. As a result, we obtain is a slowed down "optical replica" of the bunch shape, which can be recorded using a photodiode and GHz-range acquisition. These tests are performed in parallel with the existing spectral decoding technique based on a spectrometer in order to allow a comparative study. In this paper, we present first results for both detection strategies from electron bunches after the second bunch compressor of the European XFEL.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP015

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paper received ※ 24 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019

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WEP030

All-Fiber Photonic, Ultralow-Noise, Robust Optical and Microwave Signal Generators for FELs and UED

laser, timing, radiation, operation

382

J. Kim, I.J. Jeon, D. Kim, D. Kwon
KAIST, Daejeon, Republic of Korea

Funding: National Research Foundation of Korea (2018R1A2B3001793) and Korea Atomic Energy Research Institute
Optical timing and synchronization is becoming a more important and essential element for ultrafast X-ray and electron science. As a result, compact, ultralow-noise, mechanically robust and long-term stable optical and microwave signal generators are highly desirable for future XFELs and UEDs. Here we show that the combination of mode-locked fiber laser and fiber delay-based stabilization method enables the generation of ultralow-noise optical and microwave signals. We show that all-PM fiber lasers can provide excellent mechanical robustness: stable laser operation over >1 hour is maintained even in continuous 1.5 g vibrations [1]. Using a compactly packaged fiber delay as the timing reference, we could stabilize the repetition-rate phase noise of mode-locked lasers down to -100 dBc/Hz and -160 dBc/Hz at 1 Hz and 10 kHz offset frequency, respectively, at 1 GHz carrier, which corresponds to only 1.4 fs rms absolute timing jitter [1 Hz - 100 kHz] [2]. With DDS-based electronics, low-noise and agile microwave frequency synthesizer was also realized [3]. This new class of photonic signal generator will be suitable for master oscillators in various accelerator-based light sources.
[1] D. Kim et al., Opt. Lett. 44, 1068 (2019)
[2] D. Kwon et al., Opt. Lett. 42, 5186 (2017)
[3] J. Wei et al., Photon. Res. 6, 12 (2018)

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP030

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paper received ※ 05 September 2019 paper accepted ※ 22 October 2019 issue date ※ 05 November 2019

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WEP038

Commissioning and Stability Studies of the SwissFEL Bunch-Separation System

FEL, electron, operation, kicker

404

M. Paraliev, S. Dordevic, R. Ganter, C.H. Gough, N. Hiller, R.A. Krempaská, D. Voulot
PSI, Villigen PSI, Switzerland

SwissFEL is a linear electron accelerator based, X-ray Free Electron Laser at the Paul Scherrer Institute, Switzerland. It is a user oriented facility capable of producing short, high brightness X-ray pulses covering the spectral range from 1 to 50 Å. SwissFEL is designed to run in two electron bunch mode in order to serve simultaneously two experimental beamline stations (hard and soft X-ray one) at its full repetition rate. Two closely spaced (28 ns) electron bunches are accelerated in one RF macro pulse up to 3 GeV. A high stability resonant kicker system and a Lambertson septum magnet are used to separate the bunches and to send them to their respective beamlines. With the advancement of the construction of the second beamline (Athos) the bunch-separation system was successfully commissioned. In order to confirm that the beam separation process is fully transparent a stability study of the electron beam and the free electron laser in the main beamline (Aramis) was done.

Poster WEP038 [0.945 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP038

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paper received ※ 19 August 2019 paper accepted ※ 25 August 2019 issue date ※ 05 November 2019

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WEP076

A Superconducting Undulator With Variable Polarization Direction for the European FEL

undulator, FEL, polarization, radiation

499

Y. Li
EuXFEL, Hamburg, Germany
R. Rossmanith
DESY, Hamburg, Germany

In the SASE3 beam line at the European XFEL a planar undulator produces linearly polarized radiation. In order to obtain a circularly polarized radiation an afterburner will be installed to produce coherent radiation with variable polarization. Recently Argonne National Lab developed a super conductive undulator (called SCAPE) for a storage ring which allows to change polarization direction and field strength without moving mechanically the undulator parts. In this paper it is investigated if a similar device could be useful for an FEL. Such device is also a possible choice for the future undulator beam lines where circular and variable polarization are required.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP076

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paper received ※ 19 August 2019 paper accepted ※ 17 September 2019 issue date ※ 05 November 2019

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WEP079

Effect of Heat Load on Cryo-Cooled Monochromators at the European X-Ray Free-Electron Laser: Simulations and First Experimental Observations

FEL, experiment, simulation, electron

502

I. Petrov, U. Boesenberg, M. Dommach, J. Eidam, J. Hallmann, K. Kazarian, C. Kim, W. Lu, A. Madsen, J. Möller, M. Reiser, L. Samoylova, R. Shayduk, H. Sinn, V. Sleziona, A. Zozulya
EuXFEL, Schenefeld, Germany
J.W.J. Anton, S.P. Kearney, D. Shu
ANL, Lemont, Illinois, USA
X. Dong
SINAP, Shanghai, People’s Republic of China
X. Dong
SARI-CAS, Pudong, Shanghai, People’s Republic of China

European XFEL (EuXFEL) generates high-intensity ultra-short pulses at MHz repetition rate. At hard X-ray instruments, cryo-cooled silicon monochromators are used to reduce pulse bandwidth. Here, first experimental observations during commissioning of a cryo-cooled monochromator at Materials Imaging and Dynamics (MID) instrument are presented and compared with heat flow simulations. A thermal relaxation time is estimated and compared with arrival time interval between pulses. This provides the repetition rate tolerable for stable operation of monochromator.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP079

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paper received ※ 19 August 2019 paper accepted ※ 25 August 2019 issue date ※ 05 November 2019

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WEP089

Pulse Energy Measurement at the SXFEL

FEL, undulator, electron, radiation

521

Z.P. Liu, H.X. Deng, C. Feng, B. Liu, D. Wang, L.Y. Yu
SINAP, Shanghai, People’s Republic of China

The test facility is going to generate 8.8 nm FEL radiation using an 840 MeV electron linac passing through the two-stage cascaded HGHG-HGHG or EEHG-HGHG (high-gain harmonic generation, echo-enabled harmonic generation) scheme. Several methods have been developed to measure the power of pulse. The responsivity of silicon photodiode having no loss in the entrance window. Silicon photodiode reach saturates at the SXFEL. In this work, we simulated the attenuator transmittance for different thicknesses. We also show the preparations of the experiment results at the SXFEL .

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP089

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

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WEP095

The Athos Soft X-Ray Beamlines at SwissFEL

FEL, undulator, operation, electron

535

R. Follath, U. Flechsig, L. Patthey, U.H. Wagner
PSI, Villigen PSI, Switzerland

After the successful start of the hard X-ray FEL at SwissFEL in 2016, the soft X-ray FEL ATHOS at SwissFEL is expected to deliver the first beam by end of 2019. This contribution describes the beamlines attached to the FEL and reports on the status and plans for this soft X-ray facility. The ATHOS facility will operate three end stations. Two stations are already defined and are currently in the design and construction phase whereas the third station will be defined in the future. The first station (AMO) is dedicated to Atomic and Molecular physics as well as nonlinear spectroscopy. It is expected to get light in mid 2020. The second station (Furka) is for condensed matter physics. The beamline consists of a grating monochromator and distributes the beam downstream of the grating chamber by means of horizontal deflecting mirrors. Pink and monochromatic beam operation is foreseen at all branches. The monochromator uses variable line-spacing gratings on spherical substrates with a variable included angle and operates without an entrance slit. Its mechanics is based on the SX-700 design, but with the grating facing up and the mirror facing down. The installation of the beamline will start in August 2019.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP095

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paper received ※ 19 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019

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WEP098

Advanced Operational Models of the Apple X Undulator

undulator, operation, polarization, site

541

X. Liang, M. Calvi, C. Kittel, T. Schmidt
PSI, Villigen PSI, Switzerland
N.J. Sammut
University of Malta, Information and Communication Technology, Msida, Malta

Athos is a new soft X-ray beamline at SwissFEL, where the Apple X type undulators will be equipped. These devices are flexible to produce light in different polarization modes. An adequate magnetic field model is required for the operation of undulator. The undulator deflection parameter K and its gradient are calculated starting from the Fourier series of the magnetic field. In the classical parallel and anti-parallel operational modes - respectively elliptical and linear modes, the variation of the magnetic field as well as its parameters are evaluated by computer modeling. The results are compared to the magnetic measurements of the first Apple X prototype.

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paper received ※ 27 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019

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WED01

Experience with Short-Period, Small Gap Undulators at the SwissFEL Aramis Beamline

undulator, alignment, FEL, electron

564

T. Schmidt, M. Aiba, A.D. Alarcon, C. Arrell, S. Bettoni, M. Calvi, A. Cassar, E. Ferrari, R. Follath, R. Ganter, N. Hiller, P.N. Juranič, C. Kittel, F. Löhl, E. Prat, S. Reiche, T. Schietinger, D. Voulot, U.H. Wagner
PSI, Villigen PSI, Switzerland
N.J. Sammut
University of Malta, Faculty of Engineering, Msida, Malta

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.

Slides WED01 [13.825 MB]

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paper received ※ 28 August 2019 paper accepted ※ 06 November 2019 issue date ※ 05 November 2019

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WED02

Absorbed Radiation Doses on the European XFEL Undulator Systems During Early User Experiments

undulator, operation, FEL, radiation

569

F. Wolff-Fabris, J. Pflüger, H. Sinn
EuXFEL, Schenefeld, Germany
W. Decking, D. Nölle, F. Schmidt-Föhre
DESY, Hamburg, Germany
A. Hedqvist, F. Hellberg
Stockholm University, Stockholm, Sweden

The EuXFEL is a FEL user facility based on a superconducting accelerator with high duty cycle. Three gap movable SASE Undulator Systems using hybrid NdFeB permanent magnet segments are operated. Radiation damage on undulators can impact the quality of the SASE process and ultimately threaten user operation. We observed [1] in the commissioning phase doses up to 4 kGy and 3% demagnetization effect in a diagnostic undulator. Currently all SASE systems are used for user photon delivery and in this work we present characteristics of the absorbed radiation doses on undulators under stable conditions. Doses on the upstream segments are found to be originated in the event of occasional high energy electron losses. In contrast, towards the downstream end of a SASE system, individual segments show persistent absorbed doses which are proportional to the transmitted charge and are dominated by low energy radiation. This energy-dependence depiction shall result in distinct radiation damage thresholds for individual segments. Portable magnetic flux measurement systems allow in-situ tunnel assessment of undulator properties in order to estimate radiation dose limits for future user operation.
[1] F. Wolff-Fabris et al., J. of Phys. - Conf. Series 1067, 032025 (2018)

Slides WED02 [7.344 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WED02

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paper received ※ 19 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019

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THP012

Compact FEL-Driven Inverse Compton Scattering Gamma-Ray Source

electron, FEL, undulator, radiation

617

M. Placidi, G. Penn
LBNL, Berkeley, California, USA
S. Di Mitri
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
C. Pellegrini
UCLA, Los Angeles, California, USA
C. Pellegrini
SLAC, Menlo Park, California, USA

We explore the feasibility of a compact source of quasi-monochromatic, multi-MeV gamma-rays based on Inverse Compton Scattering (ICS) from a high intensity ultra-violet (UV) beam generated in a free-electron laser by the electron beam itself.[1] This scheme introduces a stronger relationship between the energy of the scattered photons and that of the electron beam, resulting in a device much more compact than a classic ICS for a given scattered energy. The same electron beam is used to produce gamma-rays in the 10-20 MeV range and UV radiation in the 10-15 eV range, in a ~4x22 m2 footprint system.
[1] M. Placidi et al., NIM A 855 (2017) 55-60.

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paper received ※ 19 August 2019 paper accepted ※ 25 August 2019 issue date ※ 05 November 2019

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THP047

Laser-Driven Compact Free Electron Laser Development at ELI-Beamlines

laser, electron, FEL, undulator

680

A.Y. Molodozhentsev
Czech Republic Academy of Sciences, Institute of Physics, Prague, Czech Republic
J.T. Green, J. Hawke, M. Kaur, D. Kocon, G. Korn, K.O. Kruchinin
ELI-BEAMS, Prague, Czech Republic
A.R. Maier
University of Hamburg, Hamburg, Germany

Funding: Advanced research using high-intensity laser produced photons and particles (CZ.02.1.01/0.0/0.0/16₀19/0000789) from the European Regional Development Fund.
The ELI-Beamlines Centre, located near Prague (Czech Republic) is an international user facility for fundamental and applied research. Using the optical parametric chirped-pulse amplification (OPCPA) technique, the ELI-Beamlines laser system will provide the laser pulse energy up to 10 Joules with the repetition rate up to 25 Hz. Combination of new laser development with constant improvement of the LWFA electron beam parameters has great potential in future development of the compact high repetition rate Free Electron Laser. The LWFA-driven FEL project, called "LUIS", is currently under preparation at ELI-Beamlines in collaboration with the University of Hamburg. The goal of the project is the improvement of the electron beam parameters in order to demonstrate the amplification and saturation of the SASE-FEL photon power in a single unit of the FEL undulator. A successful realization of the LUIS project will open a way to a next generation of laser-driven X-FELs. An overview of the LUIS project including design features and a description of all instrumentations used to characterize the laser, plasma, electron beam, photon generation will be presented in frame of this report.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP047

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paper received ※ 15 August 2019 paper accepted ※ 16 September 2019 issue date ※ 05 November 2019

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THP066

XARA: X-Band Accelerator for Research and Applications

FEL, electron, undulator, linac

715

D.J. Dunning, L.S. Cowie, J.K. Jones
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
L.S. Cowie, J.K. Jones
Cockcroft Institute, Warrington, Cheshire, United Kingdom
L.S. Cowie
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom

XARA (X-band Accelerator for Research and Applications) is a proposal for a compact ~1 GeV/c accelerator to produce attosecond light pulses in the EUV to soft X-ray region. It is under consideration as a potential future upgrade to the CLARA facility at Daresbury Laboratory, utilising high-performance X-band RF technology to increase the electron beam momentum from 250 MeV/c. Emerging techniques for generating single-cycle undulator light [1] would give access to attosecond timescales, enabling studies of ultra-fast dynamics, while also being very compact. XARA would also enhance the existing capabilities for accelerator science R&D by incorporating X-band development and increasing the electron beam momentum for novel acceleration studies.
[1] Alan Mak et al., Rep. Prog. Phys. 82 025901 (2019)

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

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THP071

Progress in High Power High Brightness Double Bunch Self-Seeding at LCLS-II

FEL, kicker, undulator, electron

726

A. Halavanau, F.-J. Decker, Y. Ding, C. Emma, Z. Huang, A.K. Krasnykh, J. Krzywiński, A.A. Lutman, G. Marcus, A. Marinelli, A. Ratti, D. Zhu
SLAC, Menlo Park, California, USA
C. Pellegrini
UCLA, Los Angeles, California, USA

Funding: Work supported by the U.S. Department of Energy Contract No. DE-AC02-76SF00515.
We have previosuly shown that we can generate near TW, 15 fs duration, near transform limited X-ray pulses in the 4 to 8 keV photon energy range using the LCLS-II copper linac, two electron bunches, a 4-crystal monochromator/delay line and a fast transverse bunch kicker. The first bunch generates a strong seeding X-ray signal, and the second bunch, initially propagating off-axis, interacts with the seed in a tapered amplifier undulator, where it propagates on axis. In this paper, we investigate the design of the 4-crystal monochromator, acting also as an X-ray delay system, and of the fast kicker, in preparation of the implementation of the system in LCLS-II.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP071

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

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THP081

PolFEL — New Facility in Poland

FEL, electron, radiation, experiment

746

K. Szamota-Leandersson, P.J. Czuma, P. Krawczyk, J. Krzywiński, R. Nietubyć, M. Staszczak, J. Szewiński
NCBJ, Świerk/Otwock, Poland
W. Bal, J. Poznański
IBB, Warsaw, Poland
A. Bartnik, H. Fiedorowicz, K. Janulewicz, N. Palka
MUT, Warsaw, Poland
J.K. Sekutowicz
DESY, Hamburg, Germany

Funding: European Regional Development Fund ¿ Smart Growth
In 2018 funds for the free electron laser PolFEL project was received. PolFEL will be driven by cw operating superconducting linac with SRF electron source. PolFEL will generate THz, IR and VIS-VUV radiation in two beamlines, respectively. In the first one, with electron beam below 80 MeV, the THz/IR radiation source will be generated in permanent magnet supper-radiant undulator, delivering THz radiation in 0.5 to 6 THz range. In the second beam line with up to 180 MeV electrons, the VIS/VUV radiation will be generated in the SASE undulator delivering coherent radiation down to 55 nm wavelength in the third harmonic, with sub-100 fs pulse duration. At the moment, four end-stations are planned. Experiments will be equipped with dedicated Pump-Probe spectrometer system as well. In the project, also, the Inverse Compton Scattering experiment is planned. In this contribution we will describe PolFEL facility in more details.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP081

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paper received ※ 29 August 2019 paper accepted ※ 18 September 2019 issue date ※ 05 November 2019

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THD03

FEL Optimization: From Model-Free to Model-Dependent Approaches and ML Prospects

FEL, controls, operation, undulator

762

S. Tomin, G. Geloni
EuXFEL, Schenefeld, Germany
M. Scholz
DESY, Hamburg, Germany

Users beam-time at modern FEL sources is an extremely valuable commodity. Moreover, maximization of FEL up-time must always be performed accounting for stringent requirements on the photon pulse characteristics. These may vary widely depending on the users requests, which poses issues to parallel operation of high-repetition rate facilities like the European XFEL. Therefore, both model-free or model-dependent optimization schemes, where the model might be given, or provided by machine-learning approaches, are of high importance for the overall efficiency of FEL facilities. In this contribution, we review our previous activities and we report on current efforts and progress in FEL optimization schemes at the European XFEL. Finally, we provide an outlook on future developments.

Slides THD03 [13.636 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THD03

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paper received ※ 21 August 2019 paper accepted ※ 12 September 2019 issue date ※ 05 November 2019

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FRA01

FEL Operation at the European XFEL Facility

FEL, operation, kicker, electron

766

D. Nölle
DESY, Hamburg, Germany

The European XFEL is a SASE FEL based user facility in the metropole region of Hamburg providing hard and soft X-ray photons with extremely high brilliance. The three FEL lines are operated simultaneously and are powered by a superconducting LINAC based on TESLA technology. Average power levels of up to several W have been demonstrated as well for soft and hard X-rays and can be requested by user experiments on day by day basis. The contribution will report on the results of the commissioning within the last two years as well as on the transition to user operation. Typical operation conditions for parallel operation of 3 SASE lines will be discussed. The perspective for the operation with an extended photon energy range, as well as for full power operation with up to 27000 pulses per second will be presented.

Slides FRA01 [27.196 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-FRA01

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

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FRA02

LCLS-II - Status and Upgrades

linac, undulator, electron, operation

772

A. Brachmann, M. Dunham, J.F. Schmerge
SLAC, Menlo Park, California, USA

Funding: This work is supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-76SF00515.
The LCLS-II FEL is under construction at the SLAC National Accelerator Laboratory. This facility is based on a superconducting accelerator, providing a cw e^- beam of 4 GeV at ~1 MHz. This beam drives two variable gap undulator (VGU) beam lines to generate photons in the soft and hard X-ray regime. High repetition rate photon beams will be available up to ~5 keV. The normal conducting accelerator will remain in operation, delivering milli-joule pulses up to ~20 keV for LCLS science. We anticipate to start the LCLS user program in the spring of 2020 using the new undulator systems. Superconducting accelerator operation will start in 2021 and will achieve full design-performance over the course of several years. Approximately a quarter of the superconducting accelerator is installed now and the associated cryoplant construction is near completion. The VGU systems will be installed and ready for beam delivery in early 2020. We will report on the project status, commissioning and ramp-up plans to achieve design performance and discuss plans to take advantage of the new facilities potential including our longer term strategy to extend the capability of SLAC’s LCLS FEL facility.

Slides FRA02 [24.207 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-FRA02

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paper received ※ 04 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019

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