FEL2019 - List of Keywords (operation)

Paper	Title	Other Keywords	Page
TUA01	Parallel Operation of SASE1 and SASE3 at the European XFEL	FEL, background, electron, undulator	25
	S. Liu, F. Brinker, W. Decking, L. Fröhlich, R. Kammering, D. Nölle, F. Obier, E. Schneidmiller, M. Scholz, T. Wilksen, M.V. Yurkov DESY, Hamburg, Germany R. Boll, N. Gerasimova, T. Mazza, M. Meyer, A. Scherz, H. Sinn EuXFEL, Schenefeld, Germany
	At the European XFEL a hard X-Ray SASE FEL (SA-SE1) and a soft X-Ray SASE FEL (SASE3) share in series the same electron beamline. This configuration couples the operation conditions for both undulators and their subsequent user experiments in terms of SASE in-tensity and background. We report on our experience in parallel operation and discuss the solutions that enable the operation of both undulators as independently as possible.
	Slides TUA01 [13.809 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUA01
About •	paper received ※ 26 August 2019 paper accepted ※ 17 October 2019 issue date ※ 05 November 2019
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TUP055	Two-Color Operation of FLASH2 Undulator	undulator, electron, laser, FEL	168
	E. Schneidmiller, M. Braune, B. Faatz, U. Jastrow, M. Kuhlmann, A.A. Sorokin, K.I. Tiedtke, M.V. Yurkov DESY, Hamburg, Germany
	FLASH is the first soft X-ray FEL user facility, routinely providing brilliant photon beams for users since 2005. The second undulator branch of this facility, FLASH2, is gap-tunable which allows to test and use advanced lasing concepts. In particular, we tested recently a two-color mode of operation based on the alternation of tunes of the undulator segments (every other segment is tuned to the second wavelength). This scheme is advantageous in comparison with a subsequent generation of two colors in two different parts of the undulator. First, source positions of two FEL beams are close to each other which makes it easier to handle them. Second, the amplification is more efficient in this configuration since the segments with respectively "wrong" wavelength act as bunchers. We developed methods for online intensity measurements of the two colors simultaneously that require a combination of two detectors. We present some examples of such measurements in the XUV and soft X-ray regimes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP055
About •	paper received ※ 20 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019
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TUP057	Analysis of Parameter Space of Soft X-Ray Free Electron Laser at the European XFEL Driven by High and Low Energy Electron Beam	undulator, FEL, electron, radiation	176
	E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	Three undulator beamlines: SASE1 and SASE2 (hard X-ray), and SASE3 (soft X-ray) are in operation at the European XFEL serving six user instruments. Next stages of the facility development are installation of two undulator beamlines in empty tunnels SASE4 and SASE5 as medium term upgrade, and extension of the facility with the second fan of undulators as long term upgrade. Construction of soft X-ray beamlines is considered in both upgrade scenario. In the case of SASE4/SASE5 electron beam with energies 8.5 GeV - 17.5 GeV will be used in order to provide simultaneous operation of new undulator beamlines with existing SASE1-SASE3. One of the scenarios for a second fan of undulators involves using of low energy (2.5 GeV) electron beam. In this paper we analyze parameter space of soft X-ray SASE FELs driven by high energy and low energy electron beam, compare output characteristics, and discuss potential advantages and disadvantages.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP057
About •	paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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WEB02	Wire-Scanners with Sub-Micrometer Resolution: Developments and Measurements	FEL, experiment, electron, emittance	307
	G.L. Orlandi, S. Borrelli, Ch. David, E. Ferrari, V. Guzenko, B. Hermann, O. Huerzeler, R. Ischebeck, C. Lombosi, C. Ozkan Loch, E. Prat PSI, Villigen PSI, Switzerland N. Cefarin, S. Dal Zilio, M. Lazzarino IOM-CNR, Trieste, Italy M. Ferianis, G. Penco, M. Veronese Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	Monitors of the beam transverse profile with ever more demanding spatial resolution and minimal invasivity are required by the FEL community. In order to improve the spatial resolution towards the sub-micrometer limit as well as to decrease the impact on the lasing process, nano-fabricated wire-scanners have been manufactured independently at PSI and FERMI by means of a lithographic technique [1,2]. Experimental tests carried out at SwissFEL at a low emittance demonstrated the capability of such innovative wire-scanner solutions to resolve beam transverse profiles with a size of 400-500 nm without being affected by any resolution limit. Status and outlook of nano-fabricated wire-scanners will be presented. [1] M. Veronese et al., NIM-A, 891, 32-36, (2018). [2] S. Borrelli et al., Comm. Phys.-Nature, 1, 52 (2018).
	Slides WEB02 [11.196 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEB02
About •	paper received ※ 24 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019
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WEP003	Balanced Optical-Microwave Phase Detector for 800-nm Pulsed Lasers with Sub-Femtosecond Resolution	laser, detector, timing, electron	322
	K. Şafak, A. Berlin, E. Cano Vargas, H.P.H. Cheng, A. Dai, J. Derksen, M. Neuhaus, P. Schiepel Cycle GmbH, Hamburg, Germany F.X. Kärtner Deutsches Elektronen Synchrotron (DESY) and Center for Free Electron Science (CFEL), Hamburg, Germany
	Novel light-matter interaction experiments conducted in free-electron lasers, ultrafast electron diffraction instruments and extreme light infrastructures require synchronous operation of microwave sources with femtosecond pulsed lasers [1]. In particular, Ti:sapphire lasers have become the most common near-infrared light source used in these facilities due to their wide-range tunability and their ability to generate ultrashort pulses at around 800-nm optical wavelength [2]. Therefore, a highly sensitive optical-to-microwave phase detector operating at 800 nm is an indispensable tool to synchronize these ubiquitous lasers to the microwave clocks of these facilities. Electro-optic sampling is one approach that has proven to be the most precise in extracting the relative phase noise between microwaves and optical pulse trains. However, their implementation at 800-nm wavelength has been so far limited [3]. Here, we show a balanced optical-microwave phase detector designed for 800-nm operation based on electro-optic sampling. The detector has a timing resolution of 0.01 fs RMS for offset frequencies above 100 Hz and a total noise floor of less than 10 fs RMS integrated from 1 Hz to 1 MHz. [1] M. Xin, K. Shafak and F. X. Kärtner, Optica, vol. 5, no. 12, pp. 1564-1578, 2018. [2] H. Yang et al., Scientific Reports, vol. 7, no. 39966, 2017. [3] M. Titberidze, DESY-THESIS-2017-040, 2017.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP003
About •	paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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WEP009	Long Term Stability and Slow Feedback Performance at the European XFEL	feedback, FEL, undulator, linac	339
	R. Kammering DESY, Hamburg, Germany
	The European XFEL is now routinely running in user operation since more than two years. Up to 8 longitudinal and 9 transversal slow feedback loops are routinely used to keep the accelerators chosen operation conditions. First tests of comparing the machine ’free-floating’ state versus fully fixing all relevant monitoring signals have been carried out and show interesting results. Here we will review the feedback systems in terms of software architecture and conceptual layout but also in respect to feedback and FEL performance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP009
About •	paper received ※ 20 August 2019 paper accepted ※ 29 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, photon, radiation	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, photon, 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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WEP045	Status of the Klystrons for the European XFEL after Commissioning and First User Operation Phase	FEL, klystron, cathode, linac	420
	V. Vogel (Fogel), M. Bousonville, A. Cherepenko, S. Choroba, H.-J. Eckoldt, T. Grevsmühl, V.V. Katalev, K. Machau, P. Morozov, B. Yildirim DESY, Hamburg, Germany
	At present 26 RF stations for the European XFEL are in operation. Each of the RF stations consists of a HV modulator located on the DESY campus, up to 1600 m long 10 kV HV cables that connect the modulators and the HV pulse transformers located in the underground tunnel, the horizontal multi-beam klystron (MBK), and an air filled waveguide distribution system (WG) between the klystron and the cavities input couplers. The klystrons can produce RF power up to 10 MW, 1.5 ms RF pulse length and 10 Hz repetition rate. Two RF stations of the injector have already achieved about 30,000 hours of operation, RF stations of the XFEL bunch compressor area have operated up to 20,000 hours and the klystrons in the XFEL main linac already have about 18,000 hours of operation. To increase the lifetime of the klystrons we are using a fast protection system (KLM) that is in routine operation since 2018 in addition to the common interlock system. In this article we will give a summary of the present klystrons operation status including the number of HV and RF arcs in the klystrons and in the WG system and operation statistics for the high power RF part of machine.
	Poster WEP045 [0.757 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP045
About •	paper received ※ 20 August 2019 paper accepted ※ 12 September 2019 issue date ※ 05 November 2019
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WEP047	Update on the Photocathode Lifetime at FLASH and European XFEL	cathode, FEL, laser, gun	427
	S. Lederer, F. Brinker, S. Schreiber DESY, Hamburg, Germany L. Monaco, D. Sertore INFN/LASA, Segrate (MI), Italy
	The photoinjectors of FLASH and the European XFEL at DESY (Hamburg, Germany) are operated by laser driven RF-guns. In both facilities Cs2Te photocathodes are successfully used. In this paper we give an update on the lifetime, quantum efficiency (QE) and dark current of the photocathodes used over the last years. At FLASH cathode #73.3 was operated for a record lifetime of 1413 days and was replaced December 2018 by cathode #10⁵.2. At the European XFEL cathode #680.1 is in operation since December 2015, for 1356 days up to now.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP047
About •	paper received ※ 20 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019
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WEP048	FLASH Photoinjector Laser Systems	laser, electron, free-electron-laser, 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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WEP070	Influence of Radiation Exposure on the FEL Performance at FLASH	undulator, FEL, radiation, simulation	488
	B. Faatz, M. Tischer, P. Vagin DESY, Hamburg, Germany
	FLASH has been operated as user facility for about 14 years. In this time, the total charge accelerated and transported through the FLASH1 undulator is around 35 Coulomb. Based on detailed monitoring of the radiation loss and reference measurements on degradation of the magnetic field of the undulator, we have performed simulations to study the change in FEL performance and first comparison of the simulations with the changes we observe during operation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP070
About •	paper received ※ 07 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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WEP092	Spare Undulator Production for PAL-XFEL HX1 Beamline	undulator, FEL, electron, permanent-magnet	524
	J.H. Han, Y.G. Jung, D.E. Kim, S.J. Lee PAL, Pohang, Kyungbuk, Republic of Korea
	In the PAL-XFEL hard X-ray beamline, 20 undulator segments with a 26 mm period and a 5 m length are installed and operated for XFEL user service. One spare undulator was manufactured in December 2018. The magnetic measurements and tuning was carried out recently. We report the measurement and tuning results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP092
About •	paper received ※ 20 August 2019 paper accepted ※ 25 August 2019 issue date ※ 05 November 2019
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WEP095	The Athos Soft X-Ray Beamlines at SwissFEL	FEL, undulator, photon, 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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WEP097	Operational Model of the Athos Undulator Beamline	polarization, undulator, background, MMI	538
	C. Kittel, M. Calvi, X. Liang, T. Schmidt PSI, Villigen PSI, Switzerland N.J. Sammut University of Malta, Information and Communication Technology, Msida, Malta
	Athos, the new Soft X-ray beamline of SwissFEL, operates 16 Apple X undulators and 15 compact chicanes to implement novel lasing schemes. With the data available after the end of the magnetic measurement campaign (middle 2020), a self-consistent set of equations will be used to summarise all the relevant properties of those devices to start their commissioning. The analytical approach planned will be discussed in great detail and tested with the preliminary experimental data available. Finally, the accuracy of this approach will be evaluated and critically compared to the requirements of the new FEL beamline.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP097
About •	paper received ※ 27 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019
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WEP098	Advanced Operational Models of the Apple X Undulator	undulator, polarization, site, photon	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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WED02	Absorbed Radiation Doses on the European XFEL Undulator Systems During Early User Experiments	undulator, FEL, photon, 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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THP008	Design of a Multi-Cell SRF Reduced-Beta Cavity for the Acceleration of Low Energy Electron Beams	cavity, linac, electron, SRF	603
	D.B. Bazyl, H. De Gersem, W.F.O. Müller TEMF, TU Darmstadt, Darmstadt, Germany J. Enders, S. Weih TU Darmstadt, Darmstadt, Germany
	Funding: Work supported by DFG (GRK 2128) Recently, the S-DALINAC has successfully passed the first ERL tests. One of the critical requirements for further operation in the ERL regime is minimising the longitudinal energy spread of the electron beam. One of the major sources for the current energy spread at the S-DALINAC is the low energy accelerating section. In order to overcome this problem an SRF reduced-beta cavity has been designed. The new cavity will replace the existing capture section and will allow to accelerate low energy electron beams with a minimised energy spread growth. In this work we discuss the electromagnetic and mechanical design of the SRF 3 GHz 6-cell reduced-beta cavity of elliptic type. In addition, we present the results of beam dynamics simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP008
About •	paper received ※ 19 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019
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THP085	Status of Athos, the Soft X-Ray FEL Line of SwissFEL	FEL, undulator, MMI, laser	753
	R. Ganter, G. Aeppli, A. Al Haddad, J. Alex, C. Arrell, V.R. Arsov, S. Bettoni, C. Bostedt, H.-H. Braun, M. Calvi, T. Celcer, P. Craievich, R. Follath, F. Frei, N. Gaiffi, Z.G. Geng, C.H. Gough, M. Huppert, R. Ischebeck, H. Jöhri, P.N. Juranič, B. Keil, F. Löhl, F. Marcellini, G. Marinkovic, G.L. Orlandi, C. Ozkan Loch, M. Paraliev, L. Patthey, M. Pedrozzi, C. Pradervand, E. Prat, S. Reiche, T. Schietinger, T. Schmidt, K. Schnorr, C. Svetina, A. Trisorio, C. Vicario, D. Voulot, U.H. Wagner, A.C. Zandonella PSI, Villigen PSI, Switzerland
	The Athos line will cover the photon energy range from 250 to 1900 eV and will operate in parallel to the hard X-ray line Aramis of SwissFEL. The paper will describe the current layout of the Athos FEL line starting from the fast kicker magnet followed by the dogleg transfer line, the small linac and the 16 APPLE undulators. From there the photon beam passes through the photonics front end and the beamline optics before reaching the experimental stations AMO and FURKA. The focus of this contribution will be on the two bunch operation commissioning (two bunches in the same RF macropulse), which started in 2018, and the characterization of the major components like the APPLE X undulator UE38, the CHIC chicane and the dechirper. The Athos installation inside the tunnel is alternating with Aramis FEL user operation and the first lasing is planned for winter 2019 / 2020.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP085
About •	paper received ※ 30 July 2019 paper accepted ※ 28 August 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, photon, 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, photon, 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, photon	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
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Paper

Title

Other Keywords

Page

TUA01

Parallel Operation of SASE1 and SASE3 at the European XFEL

FEL, background, electron, undulator

25

S. Liu, F. Brinker, W. Decking, L. Fröhlich, R. Kammering, D. Nölle, F. Obier, E. Schneidmiller, M. Scholz, T. Wilksen, M.V. Yurkov
DESY, Hamburg, Germany
R. Boll, N. Gerasimova, T. Mazza, M. Meyer, A. Scherz, H. Sinn
EuXFEL, Schenefeld, Germany

At the European XFEL a hard X-Ray SASE FEL (SA-SE1) and a soft X-Ray SASE FEL (SASE3) share in series the same electron beamline. This configuration couples the operation conditions for both undulators and their subsequent user experiments in terms of SASE in-tensity and background. We report on our experience in parallel operation and discuss the solutions that enable the operation of both undulators as independently as possible.

Slides TUA01 [13.809 MB]

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paper received ※ 26 August 2019 paper accepted ※ 17 October 2019 issue date ※ 05 November 2019

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TUP055

Two-Color Operation of FLASH2 Undulator

undulator, electron, laser, FEL

168

E. Schneidmiller, M. Braune, B. Faatz, U. Jastrow, M. Kuhlmann, A.A. Sorokin, K.I. Tiedtke, M.V. Yurkov
DESY, Hamburg, Germany

FLASH is the first soft X-ray FEL user facility, routinely providing brilliant photon beams for users since 2005. The second undulator branch of this facility, FLASH2, is gap-tunable which allows to test and use advanced lasing concepts. In particular, we tested recently a two-color mode of operation based on the alternation of tunes of the undulator segments (every other segment is tuned to the second wavelength). This scheme is advantageous in comparison with a subsequent generation of two colors in two different parts of the undulator. First, source positions of two FEL beams are close to each other which makes it easier to handle them. Second, the amplification is more efficient in this configuration since the segments with respectively "wrong" wavelength act as bunchers. We developed methods for online intensity measurements of the two colors simultaneously that require a combination of two detectors. We present some examples of such measurements in the XUV and soft X-ray regimes.

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TUP057

Analysis of Parameter Space of Soft X-Ray Free Electron Laser at the European XFEL Driven by High and Low Energy Electron Beam

undulator, FEL, electron, radiation

176

E. Schneidmiller, M.V. Yurkov
DESY, Hamburg, Germany

Three undulator beamlines: SASE1 and SASE2 (hard X-ray), and SASE3 (soft X-ray) are in operation at the European XFEL serving six user instruments. Next stages of the facility development are installation of two undulator beamlines in empty tunnels SASE4 and SASE5 as medium term upgrade, and extension of the facility with the second fan of undulators as long term upgrade. Construction of soft X-ray beamlines is considered in both upgrade scenario. In the case of SASE4/SASE5 electron beam with energies 8.5 GeV - 17.5 GeV will be used in order to provide simultaneous operation of new undulator beamlines with existing SASE1-SASE3. One of the scenarios for a second fan of undulators involves using of low energy (2.5 GeV) electron beam. In this paper we analyze parameter space of soft X-ray SASE FELs driven by high energy and low energy electron beam, compare output characteristics, and discuss potential advantages and disadvantages.

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WEB02

Wire-Scanners with Sub-Micrometer Resolution: Developments and Measurements

FEL, experiment, electron, emittance

307

G.L. Orlandi, S. Borrelli, Ch. David, E. Ferrari, V. Guzenko, B. Hermann, O. Huerzeler, R. Ischebeck, C. Lombosi, C. Ozkan Loch, E. Prat
PSI, Villigen PSI, Switzerland
N. Cefarin, S. Dal Zilio, M. Lazzarino
IOM-CNR, Trieste, Italy
M. Ferianis, G. Penco, M. Veronese
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

Monitors of the beam transverse profile with ever more demanding spatial resolution and minimal invasivity are required by the FEL community. In order to improve the spatial resolution towards the sub-micrometer limit as well as to decrease the impact on the lasing process, nano-fabricated wire-scanners have been manufactured independently at PSI and FERMI by means of a lithographic technique [1,2]. Experimental tests carried out at SwissFEL at a low emittance demonstrated the capability of such innovative wire-scanner solutions to resolve beam transverse profiles with a size of 400-500 nm without being affected by any resolution limit. Status and outlook of nano-fabricated wire-scanners will be presented.
[1] M. Veronese et al., NIM-A, 891, 32-36, (2018).
[2] S. Borrelli et al., Comm. Phys.-Nature, 1, 52 (2018).

Slides WEB02 [11.196 MB]

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WEP003

Balanced Optical-Microwave Phase Detector for 800-nm Pulsed Lasers with Sub-Femtosecond Resolution

laser, detector, timing, electron

322

K. Şafak, A. Berlin, E. Cano Vargas, H.P.H. Cheng, A. Dai, J. Derksen, M. Neuhaus, P. Schiepel
Cycle GmbH, Hamburg, Germany
F.X. Kärtner
Deutsches Elektronen Synchrotron (DESY) and Center for Free Electron Science (CFEL), Hamburg, Germany

Novel light-matter interaction experiments conducted in free-electron lasers, ultrafast electron diffraction instruments and extreme light infrastructures require synchronous operation of microwave sources with femtosecond pulsed lasers [1]. In particular, Ti:sapphire lasers have become the most common near-infrared light source used in these facilities due to their wide-range tunability and their ability to generate ultrashort pulses at around 800-nm optical wavelength [2]. Therefore, a highly sensitive optical-to-microwave phase detector operating at 800 nm is an indispensable tool to synchronize these ubiquitous lasers to the microwave clocks of these facilities. Electro-optic sampling is one approach that has proven to be the most precise in extracting the relative phase noise between microwaves and optical pulse trains. However, their implementation at 800-nm wavelength has been so far limited [3]. Here, we show a balanced optical-microwave phase detector designed for 800-nm operation based on electro-optic sampling. The detector has a timing resolution of 0.01 fs RMS for offset frequencies above 100 Hz and a total noise floor of less than 10 fs RMS integrated from 1 Hz to 1 MHz.
[1] M. Xin, K. Shafak and F. X. Kärtner, Optica, vol. 5, no. 12, pp. 1564-1578, 2018.
[2] H. Yang et al., Scientific Reports, vol. 7, no. 39966, 2017.
[3] M. Titberidze, DESY-THESIS-2017-040, 2017.

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WEP009

Long Term Stability and Slow Feedback Performance at the European XFEL

feedback, FEL, undulator, linac

339

R. Kammering
DESY, Hamburg, Germany

The European XFEL is now routinely running in user operation since more than two years. Up to 8 longitudinal and 9 transversal slow feedback loops are routinely used to keep the accelerators chosen operation conditions. First tests of comparing the machine ’free-floating’ state versus fully fixing all relevant monitoring signals have been carried out and show interesting results. Here we will review the feedback systems in terms of software architecture and conceptual layout but also in respect to feedback and FEL performance.

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WEP030

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

laser, timing, photon, radiation

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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WEP038

Commissioning and Stability Studies of the SwissFEL Bunch-Separation System

FEL, electron, photon, 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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paper received ※ 19 August 2019 paper accepted ※ 25 August 2019 issue date ※ 05 November 2019

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WEP045

Status of the Klystrons for the European XFEL after Commissioning and First User Operation Phase

FEL, klystron, cathode, linac

420

V. Vogel (Fogel), M. Bousonville, A. Cherepenko, S. Choroba, H.-J. Eckoldt, T. Grevsmühl, V.V. Katalev, K. Machau, P. Morozov, B. Yildirim
DESY, Hamburg, Germany

At present 26 RF stations for the European XFEL are in operation. Each of the RF stations consists of a HV modulator located on the DESY campus, up to 1600 m long 10 kV HV cables that connect the modulators and the HV pulse transformers located in the underground tunnel, the horizontal multi-beam klystron (MBK), and an air filled waveguide distribution system (WG) between the klystron and the cavities input couplers. The klystrons can produce RF power up to 10 MW, 1.5 ms RF pulse length and 10 Hz repetition rate. Two RF stations of the injector have already achieved about 30,000 hours of operation, RF stations of the XFEL bunch compressor area have operated up to 20,000 hours and the klystrons in the XFEL main linac already have about 18,000 hours of operation. To increase the lifetime of the klystrons we are using a fast protection system (KLM) that is in routine operation since 2018 in addition to the common interlock system. In this article we will give a summary of the present klystrons operation status including the number of HV and RF arcs in the klystrons and in the WG system and operation statistics for the high power RF part of machine.

Poster WEP045 [0.757 MB]

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WEP047

Update on the Photocathode Lifetime at FLASH and European XFEL

cathode, FEL, laser, gun

427

S. Lederer, F. Brinker, S. Schreiber
DESY, Hamburg, Germany
L. Monaco, D. Sertore
INFN/LASA, Segrate (MI), Italy

The photoinjectors of FLASH and the European XFEL at DESY (Hamburg, Germany) are operated by laser driven RF-guns. In both facilities Cs2Te photocathodes are successfully used. In this paper we give an update on the lifetime, quantum efficiency (QE) and dark current of the photocathodes used over the last years. At FLASH cathode #73.3 was operated for a record lifetime of 1413 days and was replaced December 2018 by cathode #10⁵.2. At the European XFEL cathode #680.1 is in operation since December 2015, for 1356 days up to now.

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

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WEP048

FLASH Photoinjector Laser Systems

laser, electron, free-electron-laser, 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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WEP070

Influence of Radiation Exposure on the FEL Performance at FLASH

undulator, FEL, radiation, simulation

488

B. Faatz, M. Tischer, P. Vagin
DESY, Hamburg, Germany

FLASH has been operated as user facility for about 14 years. In this time, the total charge accelerated and transported through the FLASH1 undulator is around 35 Coulomb. Based on detailed monitoring of the radiation loss and reference measurements on degradation of the magnetic field of the undulator, we have performed simulations to study the change in FEL performance and first comparison of the simulations with the changes we observe during operation.

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paper received ※ 07 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019

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WEP092

Spare Undulator Production for PAL-XFEL HX1 Beamline

undulator, FEL, electron, permanent-magnet

524

J.H. Han, Y.G. Jung, D.E. Kim, S.J. Lee
PAL, Pohang, Kyungbuk, Republic of Korea

In the PAL-XFEL hard X-ray beamline, 20 undulator segments with a 26 mm period and a 5 m length are installed and operated for XFEL user service. One spare undulator was manufactured in December 2018. The magnetic measurements and tuning was carried out recently. We report the measurement and tuning results.

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WEP095

The Athos Soft X-Ray Beamlines at SwissFEL

FEL, undulator, photon, 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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paper received ※ 19 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019

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WEP097

Operational Model of the Athos Undulator Beamline

polarization, undulator, background, MMI

538

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

Athos, the new Soft X-ray beamline of SwissFEL, operates 16 Apple X undulators and 15 compact chicanes to implement novel lasing schemes. With the data available after the end of the magnetic measurement campaign (middle 2020), a self-consistent set of equations will be used to summarise all the relevant properties of those devices to start their commissioning. The analytical approach planned will be discussed in great detail and tested with the preliminary experimental data available. Finally, the accuracy of this approach will be evaluated and critically compared to the requirements of the new FEL beamline.

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WEP098

Advanced Operational Models of the Apple X Undulator

undulator, polarization, site, photon

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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WED02

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

undulator, FEL, photon, 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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THP008

Design of a Multi-Cell SRF Reduced-Beta Cavity for the Acceleration of Low Energy Electron Beams

cavity, linac, electron, SRF

603

D.B. Bazyl, H. De Gersem, W.F.O. Müller
TEMF, TU Darmstadt, Darmstadt, Germany
J. Enders, S. Weih
TU Darmstadt, Darmstadt, Germany

Funding: Work supported by DFG (GRK 2128)
Recently, the S-DALINAC has successfully passed the first ERL tests. One of the critical requirements for further operation in the ERL regime is minimising the longitudinal energy spread of the electron beam. One of the major sources for the current energy spread at the S-DALINAC is the low energy accelerating section. In order to overcome this problem an SRF reduced-beta cavity has been designed. The new cavity will replace the existing capture section and will allow to accelerate low energy electron beams with a minimised energy spread growth. In this work we discuss the electromagnetic and mechanical design of the SRF 3 GHz 6-cell reduced-beta cavity of elliptic type. In addition, we present the results of beam dynamics simulations.

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THP085

Status of Athos, the Soft X-Ray FEL Line of SwissFEL

FEL, undulator, MMI, laser

753

R. Ganter, G. Aeppli, A. Al Haddad, J. Alex, C. Arrell, V.R. Arsov, S. Bettoni, C. Bostedt, H.-H. Braun, M. Calvi, T. Celcer, P. Craievich, R. Follath, F. Frei, N. Gaiffi, Z.G. Geng, C.H. Gough, M. Huppert, R. Ischebeck, H. Jöhri, P.N. Juranič, B. Keil, F. Löhl, F. Marcellini, G. Marinkovic, G.L. Orlandi, C. Ozkan Loch, M. Paraliev, L. Patthey, M. Pedrozzi, C. Pradervand, E. Prat, S. Reiche, T. Schietinger, T. Schmidt, K. Schnorr, C. Svetina, A. Trisorio, C. Vicario, D. Voulot, U.H. Wagner, A.C. Zandonella
PSI, Villigen PSI, Switzerland

The Athos line will cover the photon energy range from 250 to 1900 eV and will operate in parallel to the hard X-ray line Aramis of SwissFEL. The paper will describe the current layout of the Athos FEL line starting from the fast kicker magnet followed by the dogleg transfer line, the small linac and the 16 APPLE undulators. From there the photon beam passes through the photonics front end and the beamline optics before reaching the experimental stations AMO and FURKA. The focus of this contribution will be on the two bunch operation commissioning (two bunches in the same RF macropulse), which started in 2018, and the characterization of the major components like the APPLE X undulator UE38, the CHIC chicane and the dechirper. The Athos installation inside the tunnel is alternating with Aramis FEL user operation and the first lasing is planned for winter 2019 / 2020.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP085

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paper received ※ 30 July 2019 paper accepted ※ 28 August 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, photon, 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, photon, 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, photon

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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