FEL2019 - List of Keywords (experiment)

Paper	Title	Other Keywords	Page
MOA02	First Lasing of a Free Electron Laser in the Soft X-Ray Spectral Range with Echo Enabled Harmonic Generation	FEL, laser, electron, free-electron-laser	7
	E. Allaria, A. Abrami, L. Badano, M. Bossi, N. Bruchon, F. Capotondi, D. Castronovo, M. Cautero, P. Cinquegrana, M. Coreno, I. Cudin, M.B. Danailov, G. De Ninno, A.A. Demidovich, S. Di Mitri, B. Diviacco, W.M. Fawley, M. Ferianis, L. Foglia, G. Gaio, F. Giacuzzo, L. Giannessi, S. Grulja, F. Iazzourene, G. Kurdi, M. Lonza, N. Mahne, M. Malvestuto, M. Manfredda, C. Masciovecchio, N.S. Mirian, I. Nikolov, G. Penco, E. Principi, L. Raimondi, P. Rebernik Ribič, R. Sauro, C. Scafuri, P. Sigalotti, S. Spampinati, C. Spezzani, L. Sturari, M. Svandrlik, M. Trovò, M. Veronese, D. Vivoda, M. Zaccaria, D. Zangrando, M. Zangrando Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy H.-H. Braun, E. Ferrari, E. Prat, S. Reiche PSI, Villigen PSI, Switzerland N. Bruchon University of Trieste, Trieste, Italy M. Coreno CNR-ISM, Trieste, Italy M.-E. Couprie, A. Ghaith SOLEIL, Gif-sur-Yvette, France G. De Ninno University of Nova Gorica, Nova Gorica, Slovenia C. Feng SARI-CAS, Pudong, Shanghai, People’s Republic of China F. Frassetto, L.P. Poletto LUXOR, Padova, Italy D. Garzella CEA, Gif-sur-Yvette, France V. Grattoni DESY, Hamburg, Germany E. Hemsing SLAC, Menlo Park, California, USA P. Miotti CNR-IFN, Padova, Italy G. Penn LBNL, Berkeley, California, USA M.A. Pop MAX IV Laboratory, Lund University, Lund, Sweden E. Roussel PhLAM/CERCLA, Villeneuve d’Ascq Cedex, France T. Tanikawa EuXFEL, Schenefeld, Germany D. Xiang Shanghai Jiao Tong University, Shanghai, People’s Republic of China
	We report on the successful operation of a Free Electron Laser (FEL) in the Echo Enabled Harmonic Generation (EEHG) scheme at the FERMI facility at Sincrotrone Trieste. The experiment required a modification of the FEL-2 undulator line which, in normal operation, uses two stages of high-gain harmonic generation separated by a delay line. In addition to a new seed laser, the dispersion in the delay-line was increased, the second stage modulator changed and a new manipulator installed in the delay-line chicane hosting additional diagnostic components. With this modified setup we have demonstrated the first evidence of strong exponential gain in a free electron laser operated in EEHG mode at wavelengths as short as 5 nm.
	Slides MOA02 [5.133 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-MOA02
About •	paper received ※ 21 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019
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TUP001	Extension of the PITZ Facility for a Proof-of-Principle Experiment on THz SASE FEL	radiation, FEL, undulator, electron	38
	P. Boonpornprasert, G.Z. Georgiev, G. Koss, M. Krasilnikov, X. Li, F. Mueller, A. Oppelt, S. Philipp, H. Shaker, F. Stephan, T. Weilbach DESY Zeuthen, Zeuthen, Germany Z.G. Amirkhanyan CANDLE SRI, Yerevan, Armenia
	The Photo Injector Test Facility at DESY in Zeuthen (PITZ) has been proposed as a suitable facility for research and development of an accelerator-based THz source prototype for pump-probe experiments at the European XFEL. A proof-of-principle experiment to generate THz SASE FEL radiation by using an LCLS-I undulator driven by an electron bunch from the PITZ accelerator has been planned and studied. The undulator is foreseen to be installed downstream from the current PITZ accelerator, and an extension of the accelerator tunnel is necessary. Radiation shielding for the extended tunnel was designed, and construction works are finished. Design of the extended beamline is ongoing, not only for this experiment but also for other possible experiments. Components for the extended beamline, including magnets for beam transport, a chicane bunch compressor, electron beam diagnostics devices, and THz radiation diagnostics devices have been studied. An overview of these works will be presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP001
About •	paper received ※ 20 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019
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TUP002	Progress in Preparing a Proof-of-Principle Experiment for THz SASE FEL at PITZ	laser, FEL, undulator, flattop	41
	X. Li, P. Boonpornprasert, Y. Chen, G.Z. Georgiev, J.D. Good, M. Groß, P.W. Huang, I.I. Isaev, C. Koschitzki, M. Krasilnikov, S. Lal, O. Lishilin, G. Loisch, D. Melkumyan, R. Niemczyk, A. Oppelt, H.J. Qian, H. Shaker, G. Shu, F. Stephan, G. Vashchenko DESY Zeuthen, Zeuthen, Germany
	A proof-of-princle experiment for a THz SASE FEL is undergoing preparation at the Photo Injector Test facility at DESY in Zeuthen (PITZ), as a prototype THz source for pump-probe experiments at the European XFEL, which could potentially provide up to mJ/pulse THz radiation while maintaining the identical pulse train structure as the XFEL pulses. In the proof-of-principle experiment, LCLS-I undulators will be installed to generate SASE radiation in the THz range of 3-5 THz from electron bunches of 16-22 MeV/c. One key design is to obtain the peak current of nearly 200 A from the heavily charged bunches of a few nC. In this paper, we report our simulation results on the optimization of the space charge dominated beam in the photo injector and the following transport line with two cathode laser setups. Experimental results based on a short Gaussian laser will also be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP002
About •	paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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TUP003	Design of a Magnetic Bunch Compressor for the THz SASE FEL Proof-of-Principle Experiment at PITZ	FEL, radiation, dipole, undulator	45
	H. Shaker, P. Boonpornprasert, G.Z. Georgiev, G. Koss, M. Krasilnikov, X. Li, A. Lueangaramwong, F. Mueller, A. Oppelt, S. Philipp, F. Stephan, G. Vashchenko, T. Weilbach DESY Zeuthen, Zeuthen, Germany
	For pump-probe experiments at the European XFEL, a THz source is required to produce intense THz pulses at the same repetition rate as the X-ray pulses from XFEL. Therefore, an accelerator-based THz source with identical electron source as European XFEL was suggested and proof-of-principle experiments utilizing an LCLS I undulator will be performed at the Photo Injector Test Facility at DESY in Zeuthen (PITZ). The main idea is to use a 4nC beam for maximum SASE radiation but to allow different radiation regimes a magnetic bunch compressor can be used. This helps e.g. to reduce the saturation length inside the undulator and also to study super-radiant THz radiation. In this paper a design of a chicane type magnetic bunch compressor using HERA corrector magnets is presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP003
About •	paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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TUP004	A Superradiant THz Undulator Source for XFELs	undulator, FEL, electron, radiation	48
	T. Tanikawa, G. Geloni, S. Karabekyan, S. Serkez EuXFEL, Schenefeld, Germany V.B. Asgekar University of Pune, Pune, India S. Casalbuoni KIT, Eggenstein-Leopoldshafen, Germany M. Gensch Technische Universität Berlin, Berlin, Germany M. Gensch DLR, Berlin, Germany S. Kovalev HZDR, Dresden, Germany
	The European XFEL has successfully achieved first lasing in 2017 and meanwhile three SASE FEL beamlines are in operation. An increasing number of users has great interest in a specific type of two-color pump-probe experiments in which high-field THz pulses are employed to drive nonlinear processes and dynamics in matter selectively. Here, we propose to use a 10-period superconducting THz undulator to provide intense, narrowband light pulses tunable in wide range between 3 and 100 THz. The exploitation of superconducting technology allows us to meet the challenge of generating such low photon energy radiation despite the very high electron beam energy at the European XFEL. In this presentation, we will present the latest development concerning THz undulator design and present the expected THz pulse properties for the case of the European XFEL.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP004
About •	paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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TUP007	Experience with the Superradiant THz User Facility Driven by a Quasi-CW SRF Accelerator at ELBE	detector, electron, radiation, SRF	56
	M. Bawatna, B.W. Green HZDR, Dresden, Germany
	Instabilities in beam and bunch parameters, such as bunch charge, beam energy or changes in the phase or amplitude of the accelerating field in the RF cavities can be the source of noise in the various secondary sources driven by the electron beam. Bunch charge fluctuations lead to intensity instabilities in the super-radiant THz sources. The primary electron beam driving the light sources has a maximum energy of 40 MeV and a maximum current of 1.6 mA. Depending on the mode of operation required, there are two available injectors in use at ELBE. The first is the thermionic injector, which is used for regular operating modes and supports repetition rates up to 13 MHz and bunch charges up to 100 pC. The second is the SRF photo-cathode injector, which is used for experiments that may require lower emittance or higher bunch charges of up to 1 nC. It has a maximum repetition rate of 13 MHz, which can be adjusted to lower rates if desired, also including different macro pulse modes of operation. In this contribution, we will present our work in the pulse-resolved intensity measurement that allows for correction of intensity instabilities.
	Poster TUP007 [0.658 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP007
About •	paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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TUP012	Smith-Purcell Radiation Emitted by Pico-second Electron Bunches from a 30 keV Photo-Electron Gun	electron, radiation, laser, gun	66
	M.R. Asakawa, S. Yamaguchi Kansai University, Osaka, Japan
	In this paper, an experiment to generate Smith-Purcell radiation using pico-second electron bunches is reported. The electron bunch was produced by a DC 30 keV photo-electron electron gun driven by a 100 fs Ti:sapphire laser. The charge of the bunch varied from 1 pC to 300 pC by changing the laser power. Smith-Purcell radiation experiment was performed with the central part of the entire electron bunch. Estimation of pulsewidth of the bunch based on the envelope equation showed that the pulsewidth of the bunch at the anode electrode increased from 0.8 ps to 3.2 ps as the bunch charge increase from 0.1 pC to 11 pC. Such electron bunch was traveled along the surface of the metallic grating with a period of 2 mm. The radiation wavelength was estimated to be 4 mm at an obserbation angle of 10 degree. The radiation power was measured by a bolometer and quadraticallly increased with the bunch charge. Numerical simulation of this experiment indicated the enhancement of the harmonic components of the radiation. We are now constructing a THz-TDS system to measure the time-trace of the electric field of the radiation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP012
About •	paper received ※ 14 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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TUP018	Superradiant Emission of Electron Bunches Based on Cherenkov Excitation of Surface Waves in 1D and 2D Periodical Lattices: Theory and Experiments	electron, GUI, radiation, simulation	80
	A. Malkin, N.S. Ginzburg, A. Sergeev, I.V. Zheleznov, I.V. Zotova IAP/RAS, Nizhny Novgorod, Russia M.I. Yalandin RAS/IEP, Ekaterinburg, Russia V.Yu. Zaslavsky UNN, Nizhny Novgorod, Russia
	Funding: The work was supported by RFBR grant no. 17-08-01072 In recent years, significant progress was achieved in generation of high-power ultrashort microwave pulses based on superradiance (SR) of electron bunches extended in the wavelength scale. In this process, coherent emission from the entire volume of the bunch occurs due to the development of microbunching and slippage of the wave with respect to electrons. An obvious method for generation of high-power sub-THz radiation is the implementation of oversized periodical slow-wave structures where evanescent surface waves can be excited. We report of the experiments on Cherenkov generation of 150 ps SR pulses with a central frequency of 0.14 THz, and an extremely high peak power up to 70 MW. In order to generate spatially coherent radiation in shorter wavelength ranges (including THz band) in strongly oversized waveguiding systems, we propose a slow wave structure with double periodic corrugation (2D SWS). Using the quasi-optical theory and PIC simulations, we demonstrate the applicability of such 2D SWS and its advantages against traditional 1D SWS. Proof of principle experiments on observation G-band Cherenkov SR in 2D SWS are currently in progress.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP018
About •	paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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TUP019	Regime of Multi-Stage Non-Resonant Trapping in Free Electron Lasers	electron, FEM, FEL, wiggler	83
	A.V. Savilov, I.V. Bandurkin, Yu.S. Oparina, N.Yu. Peskov IAP/RAS, Nizhny Novgorod, Russia
	Funding: This work is supported by the RFBR (grants #18-02-40009, #18-02-00765) and by the IAP RAS Project 0035-2019-0001. We describe three works united by the idea of the non-resonant regime [1] providing an effective trapping in a beam with a great energy spread. In this regime, the "bucket" corresponding to the resonant electron-wave interaction passes through the electron layer on the energy-phase plane and traps a fraction of electrons. (I) Operability of this regime was demonstrated in the high-efficient 0.8 MeV Ka-band FEM-amplifier [2]. (II) In short-wavelength FELs the multi-stage trapping in several consecutive sections can be organized [3]. In each section a small e-beam fraction is trapped due to a weak electron-wave interaction. However, repetition of this process from section to section involves in the interaction almost the whole e-beam. We describe efficiency enhancement and improving the frequency wave spectrum in multi-stage SASE FELs. (III) The multi-stage amplification of a single-frequency wave signal can provide cooling of the electron bunch. In this regime, tapering of every section is provided such that the "bucket" goes from maximal initial electron energy down to the minimal one and moves down energies of trapped electrons. [1] A.Savilov et al., Nucl. Instr. Meth. A, vol. 507, p.158, 2003 [2] A.Kaminsky et al., Int. Conf. IRMMW-THz 2018, art. 4057938 [3] S.Kuzikov, A.Savilov, Phys. Plasmas, vol. 25, p.113114, 2018
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP019
About •	paper received ※ 14 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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TUP024	Electronic Modulation of the FEL-Oscillator Radiation Power Driven by ERL	FEL, radiation, electron, controls	98
	O.A. Shevchenko, E.V. Bykov, Ya.V. Getmanov, S.S. Serednyakov, S.V. Tararyshkin BINP SB RAS, Novosibirsk, Russia M.V. Fedin, A.R. Melnikov, S.L. Veber International Tomography Center, SB RAS, Novosibirsk, Russia Ya.V. Getmanov, S.S. Serednyakov NSU, Novosibirsk, Russia
	FEL oscillators usually operate in CW mode and produce periodic train of radiation pulses but some user experiments require modulation of radiation power. Conventional way to obtain this modulation is using of mechanical shutters but it cannot provide very short switching time and may lead to decreasing of the radiation beam quality. Another way could be based on the electron beam current modulation but it cannot be used in the ERL. We propose a simple way of fast control of the FEL lasing which is based on periodic phase shift of electron bunches with respect to radiation stored in optical cavity. The phase shift required to suppress lasing is relatively small and it does not change significantly repetition rate. This approach has been realized at NovoFEL facility. It allows to generate radiation macropulses of desirable length down to several microseconds (limited by quality factor of optical cavity and FEL gain) which can be synchronized with external trigger. We present detailed description of electronic power modulation scheme and discuss the results of experiments.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP024
About •	paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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TUP035	Sensitivity of LCLS Self-Seeded Pedestal Emission to Laser Heater Strength	laser, electron, free-electron-laser, bunching	126
	G. Marcus, D.K. Bohler, Y. Ding, W.M. Fawley, Y. Feng, E. Hemsing, Z. Huang, J. Krzywiński, A.A. Lutman, D.F. Ratner SLAC, Menlo Park, California, USA
	Measurements of the soft X-ray, self-seeding spectrum at the LCLS free-electron laser generally display a pedestal-like distribution around the central seeded wavelength that degrades the spectral purity. We have investigated the detailed experimental characteristics of this pedestal and found that it is comprised of two separate components: (1) normal SASE whose total strength is nominally insensitive to energy detuning and laser heater (LH) strength; (2) sideband-like emission whose strength positively correlates with that of the amplified seed and negatively with energy detuning and LH strength. We believe this latter, non-SASE component arises from comparatively long wavelength amplitude and phase modulations of the main seeded radiation line. Its shot-to-shot variability and LH sensitivity suggests an origin connected to growth of the longitudinal microbunching instability on the electron beam. Here, we present experimental results taken over a number of shifts that illustrate the above mentioned characteristics.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP035
About •	paper received ※ 28 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019
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TUP038	Axial Symmetry in Spontaneous Undulator Radiation for XFELO Two-Bunch Experiment	FEL, electron, laser, radiation	134
	Y.S. Li University of Chicago, Chicago, Illinois, USA K. Kim, R.R. Lindberg ANL, Lemont, Illinois, USA
	Funding: U.S. DOE, Office of Science, Office of BES, under Contract No. DE-AC02-06CH11357 and National Science Foundation under Award No. PHY-1549132, the Center for Bright Beams. A well known discrepancy exists between 2D and 3D FEL simulation codes with respect to the radiation field intensity prior to the exponential gain regime [1]. This can be qualitatively explained by the fact that the 3D field representation preserves many more modes than does the axisymmetric field solved for by a 2D code. In this paper, we seek to develop an analytical model that quantifies this difference. We begin by expanding the spontaneous undulator radiation field as a multipole series, whose lowest order mode is axisymmetric. This allows us to calculate the difference in predicted intensity. Next, we confirm these results with numerical calculation and existing FEL codes GINGER and GENESIS. Finally, we discuss the implications of this study with respect to the XFELO two-bunch experiment to be conducted at LCLS-II. [1] Z. Huang and K.-J. Kim, "Review of X-ray free-electron laser theory", Phys. Rev. ST-AB, vol. 10, p. 034801, 2007.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP038
About •	paper received ※ 19 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019
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TUP050	Comparison Between, and Validation Against an Experiment of, a Slowly-varying Envelope Approximation Code and a Particle-in-Cell Simulation Code for Free-Electron Lasers	undulator, FEL, simulation, electron	153
	P. Traczykowski, L.T. Campbell, J. Henderson, B.W.J. MᶜNeil USTRAT/SUPA, Glasgow, United Kingdom L.T. Campbell, J. Henderson, P. Traczykowski STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom H. Freund University of New Mexico, Albuquerque, USA B.W.J. MᶜNeil, P. Traczykowski Cockcroft Institute, Warrington, Cheshire, United Kingdom P.J.M. van der Slot Mesa+, Enschede, The Netherlands
	Free-electron laser simulation codes employ either the Slowly-Varying Envelope Approximation (SVEA) or a Particle-in-Cell (PiC) formulation. Maxwell’s equations are averaged over the fast time scale in the SVEA so that there is no need to resolve the wave period. In contrast, the fast oscillation is retained in PiC codes. As a result, the SVEA codes are much less computationally intensive and are used more frequently than PiC codes. While the orbit dynamics in PiC codes and some SVEA Codes (MEDUSA and MINERVA) use the full unaveraged Lorentz force equations, some SVEA codes use the Kroll-Morton-Rosenbluth (KMR) approximation (GENESIS, GINGER, FAST, and TDA3D). Steady-state simulation comparisons [1] have appeared in the literature between different codes using the averaged and unaveraged particle dynamics. Recently, a comparison between three KMR SVEA codes (GENESIS, GINGER, and FAST) and the PUFFIN PiC code in the time-dependent regime has been reported [2]. In this paper, we present a comparison between the unaveraged PiC code PUFFIN, the unaveraged SVEA code MINERVA for the time-dependent simulation of SASE free-electron lasers with the experimental measurements from SPARC SASE FEL at ENEA Frascati. [1] S.G. Biedron et al., NIMA 445, 110 (2000). [2] B. Garcia et al., paper presented at the 38th International Free Electron Laser Conference, Santa Fe, New Mexico, 20 - 25 August 2017.
	Poster TUP050 [0.908 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP050
About •	paper received ※ 02 August 2019 paper accepted ※ 28 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	photon, FEL, 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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TUP062	Two Colors at the SASE3 Line of the European XFEL: Project Scope and First Measurements	FEL, electron, photon, 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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TUP076	Seeding R&D at sFLASH	electron, laser, FEL, free-electron-laser	230
	C. Lechner, S. Ackermann, R.W. Aßmann, B. Faatz, V. Grattoni, I. Hartl, S.D. Hartwell, R. Ivanov, T. Laarmann, T. Lang, M.M. Mohammad Kazemi, G. Paraskaki, A. Przystawik, J. Zheng DESY, Hamburg, Germany A. Azima, H. Biss, M. Drescher, W. Hillert, V. Miltchev, J. Roßbach University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany S. Khan DELTA, Dortmund, Germany
	Funding: Work supported by Federal Ministry of Education and Research of Germany under contract No. 05K13GU4, 05K13PE3, and 05K16PEA. Free-electron lasers (FELs) based on the self-amplified spontaneous emission (SASE) principle generate photon pulses with typically poor longitudinal coherence. FEL seeding techniques greatly improve longitudinal coherence by initiating FEL amplification in a controlled way using coherent light pulses. The sFLASH experiment installed at the FEL user facility FLASH at DESY in Hamburg is dedicated to the study of external seeding techniques. In this paper, the layout of the sFLASH seeding experiment is presented and an overview of recent developments is given.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP076
About •	paper received ※ 30 September 2019 paper accepted ※ 17 October 2019 issue date ※ 05 November 2019
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TUP092	XFEL Third Harmonic Statistics Measurement at LCLS	FEL, photon, undulator, 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, photon	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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TUD03	Fine and Hyperfine Structure of FEL Emission Spectra	FEL, electron, radiation, laser	276
	V.V. Kubarev, Ya.V. Getmanov, O.A. Shevchenko BINP SB RAS, Novosibirsk, Russia S. Bae, Y.U. Jeong KAERI, Daejon, Republic of Korea
	This paper presents the results of experimental investigations of the fine and hyperfine spectral structures of the Novosibirsk free-electron laser (NovoFEL) and the compact free-electron laser of the Korea Atomic Energy Research Institute (KAERI FEL) by means of the optimal instruments, resonance Fabry-Perot interferometers. The very high coherence of the NovoFEL spectrum was measured in regimes with one pulse circulating inside its optical resonator (the coherence length is 7 km, and the relative width of the hyperfine structure lines is 2E-8) and with total absence of coherence between two circulating pulses, i.e. the fine structure. Sixty pulses circulate simultaneously inside the KAERI FEL optical resonator, and the measured coherence length on average covers ten pulses (the coherence length is 1 m; the relative width of the fine structure lines is 10^-4).
	Slides TUD03 [3.177 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUD03
About •	paper received ※ 16 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019
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WEB01	Identification and Mitigation of Smoke-Ring Effects in Scintillator-Based Electron Beam Images at the European XFEL	FEL, electron, diagnostics, ECR	301
	G. Kube, S. Liu, A.I. Novokshonov, M. Scholz DESY, Hamburg, Germany
	Standard transverse beam profile measurements at the European XFEL are based on scintillating screen monitors using LYSO:Ce. While it is possible to resolve beam sizes down to a few micrometers with this scintillator, the experience during the XFEL commissioning showed that the measured emittance values were significantly larger than the expected ones. In addition, beam profiles measured at bunch charges of a few hundred pC showed a ’smoke ring’ structure. While coherent OTR emission and beam dynamical influence can be excluded, it is assumed that the profile distortions are caused by effects from the scintillator material. Following the experience in high energy physics, a simple model was developed which takes into account quenching effects of excitonic carriers inside a scintillator in a heuristic way. Based on this model, the observed beam profiles can be understood qualitatively. Together with the model description, first comparisons with experimental results will be shown. Possible new scintillator materials suitable for beam profile diagnostics and first test results from beam measurements will be presented.
	Slides WEB01 [5.057 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEB01
About •	paper received ※ 20 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019
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WEB02	Wire-Scanners with Sub-Micrometer Resolution: Developments and Measurements	FEL, electron, operation, 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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WEP016	Precise Laser-to-RF Synchronization of Photocathode Lasers	laser, timing, electron, controls	364
	M. Titberidze, M. Felber, T. Kozak, T. Lamb, J. Müller, H. Schlarb, S. Schulz, C. Sydlo, F. Zummack DESY, Hamburg, Germany
	RF photo-injectors are used in various large, mid and small-scale accelerator facilities such as X-ray Free Electron Lasers (XFELs), external injection-based laser-driven plasma accelerators (LPAs) and ultrafast electron diffraction (UED) sources. Many of these facilities require a high precision synchronization of the photo-injector laser system, either because of beam dynamics reasons or the photo-injector directly impacting pump-probe experiments carried out to study physical processes on femtosecond timescales. It is thus crucial to achieve synchronization in the order of 10 fs rms or below between the photocathode laser and the RF source driving the RF gun. In this paper, we present the laser-to-RF synchronization setup employed to lock a commercial near-infrared (NIR) photocathode laser oscillator to a 2.998 GHz RF source. Together with the first results achieving ~ 10 fs rms timing jitter in the measurement bandwidth from 10 Hz up to 1 MHz, we describe an advanced synchronization setup as a future upgrade, promising even lower timing jitter and most importantly long-term timing drift stability.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP016
About •	paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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WEP024	1.3 GHz Solid State Power Amplifier for the Buncher in CTFEL Facility	electron, FEL, cavity, bunching	371
	T.H. He, C.L. Lao, P. Li, X. Luo, L.J. Shan, K. Zhou CAEP/IAE, Mianyang, Sichuan, People’s Republic of China
	The THz Free Electron Laser facility (CAEP THz FEL, CTFEL) of the China Academy of Engineering Physics uses high quality electron beams to generate high average power terahertz radiations. A 1.3 GHz RF buncher is used in front of the superconducting linear accelerator of the CTFEL facility to improve the electron beams quality. The RF buncher is driven by a solid state power amplifier (SSPA), and the SSPA is feedback controlled by a low level RF (LLRF) control system to ensure the high stability of the amplitude and phase of the bunching field in the buncher cavity. The SSPA operates at 1.3 GHz and outputs 0 to 5 kW of continuous wave power. This paper mainly introduces the principle and composition of the SSPA, and presents some experiments on the RF buncher driven by the SSPA.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP024
About •	paper received ※ 15 August 2019 paper accepted ※ 27 August 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, simulation, electron, photon	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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WEP081	Design and Development of High-Speed Data Acquisition System and Online Data Processing with a Heterogeneous FPGA/GPU Architecture	FPGA, real-time, GPU, data-acquisition	510
	M. Bawatna, J.-C. Deinert, O. Knodel, S. Kovalev HZDR, Dresden, Germany R.G. Spallek Technische Universität Dresden, Dresden, Germany
	The superradiant THz sources at TELBE facility is based on the new class of accelerator-driven terahertz (THz) radiation sources that provide high repetition rates up to 13 MHz, and flexibility of tuning the THz pulse form. The THz pulses are used for the excitation of materials of interest, about two orders of magnitude higher than state-of-the-art tabletop sources. Time-resolved experiments can be performed with a time resolution down to 30 femtoseconds (fs) using the novel pulse-resolved Data Acquisition (DAQ) system. However, the increasing demands in improving the flexibility, data throughput, and speed of the DAQ systems motivate the integration of reconfigurable processing units close to the new detectors to accelerate the processing of tens of GigaBytes of data per second. In this paper, we introduce our online ultrafast DAQ system that uses a GPU platform for real-time image processing, and a custom high-performance FPGA board for interfacing the image sensors and provide a continuous data transfer.
	Poster WEP081 [0.830 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP081
About •	paper received ※ 18 August 2019 paper accepted ※ 25 August 2019 issue date ※ 05 November 2019
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THB02	Understanding 1D to 3D Coherent Synchrotron Radiation Effects	simulation, radiation, emittance, electron	578
	A.D. Brynes STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Collective effects such as coherent synchrotron radiation (CSR) can have a strong influence of the properties of an electron bunch with respect to the quality of the FEL light that it produces. In particular, CSR experienced by a bunch on a curved trajectory can increase the transverse emittance of a beam. In this contribution, we present an extension to the well-established 1D theory of CSR by accounting fully for the forces experienced in the entrance and exit transients of a bending magnet. A new module of the General Particle Tracer (GPT) tracking code was developed for this study, showing good agreement with theory. In addition to this analysis, we present experimental measurements of the emittance growth experienced in the FERMI bunch compressor chicane as a function of bunch length. When the bunch undergoes extreme compression, the 1D theory breaks down and is no longer valid. A comparison between the 1D theory, experimental measurements and a number of codes which simulate CSR differently are presented, showing better agreement when the transverse properties of the bunch are taken into account.
	Slides THB02 [3.591 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THB02
About •	paper received ※ 19 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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THP041	Interaction of Powerful Electro-Magnetic Fields With Bragg Reflectors	laser, simulation, FEL, electron	673
	I. Bahns, W. Hillert, P. Rauer, J. Roßbach University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany H. Sinn EuXFEL, Schenefeld, Germany
	Funding: supported by BMBF FKZ 05K16GU4 The interaction of an X-ray free electron laser (XFEL) with a Bragg Reflector can cause a change of the lattice constant, which has a direct influence on the stability of the reflection conditions [1] and can also excite modes of vibration [2]. The dynamical thermoelastic effects of the photon-matter-interaction are simulated with a finite-element-method (FEM) using the assumptions of continuums mechanics. To compare the simulation results with measured signals, a Michelson interferometer with ultrafast photodiodes (risetime <175ps, bandwith >2GHz) has been built up. To test the experimental setup in an in-house environment a pulsed UV laser is used to introduce a temporal displacement field in a silicon crystal created by about 0.26µJ of absorbed energy. The measured signal is in agreement with the FEM simulation and has shown that if averaging over thousands of pulses is applied a resolution <0.5pm is feasible. This makes this experimental setup useful to investigate the X-ray-matter-interaction of Bragg reflectors at modern X-ray facilities. [1] S. Stoupin et al., Physical Review B 86.5 (2012): 054301. [2] B. Yang, S. Wang and J. Wu, J. Synchrotron Rad. (2018) 25, 166-176.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP041
About •	paper received ※ 23 August 2019 paper accepted ※ 31 October 2019 issue date ※ 05 November 2019
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THP069	Observations on Microbunching of Electrons in Laser-Driven Plasma Accelerators and Free-Electron Lasers	FEL, laser, electron, bunching	722
	A.H. Lumpkin Fermilab, Batavia, Illinois, USA M. Downer, M. LaBerge The University of Texas at Austin, Austin, Texas, USA D.W. Rule Private Address, Silver Spring, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. The periodic longitudinal density modulation of relativistic electrons at the resonant wavelength (microbunching) is a fundamental aspect of free-electron lasers (FELs). In one case, microbunching fractions reached 20% at saturation of a self-amplified spontaneous emission (SASE) FEL resulting in gains of 1 million at 530 nm [1]. In that experiment the z-dependent gain of coherent optical transition radiation (COTR) was also measured. In laser-driven plasma accelerators (LPAs), microbunching at visible wavelengths has also been recently reported as evidenced by significant COTR enhancements measured in near-field and far-field images on a single shot for the first time [2]. An analytical model for COTR interferometry (COTRI) addresses both cases. In the FEL, one identified microbunched transverse cores of 25-100 microns while in the LPA the reported transverse sizes at the exit of the LPA were a few microns. In the latter case, signal enhancements of nearly 100, 000 and extensive fringes out to 30 mrad in angle space were recorded. The broadband microbunching observed in the LPA case could act as a seed for a SASE FEL experiment with tunability in principle over the visible regime. [1] A.H. Lumpkin et al., Phys. Rev. Lett. 88, No.23, 234801 (2002). [2] A.H. Lumpkin, M. LaBerge, D.W. Rule et al., Proceedings of AAC18, (IEEE), (2019).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP069
About •	paper received ※ 20 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019
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THP073	Status Update for the High Gain High Efficiency TESSA-266 Experiment	undulator, quadrupole, laser, electron	730
	Y. Park, D.K. Dang, P.E. Denham, P. Musumeci, N.S. Sudar UCLA, Los Angeles, USA R.B. Agustsson, T.J. Campese, I.I. Gadjev, A.Y. Murokh RadiaBeam, Los Angeles, California, USA C.C. Hall, S.D. Webb RadiaSoft LLC, Boulder, Colorado, USA Y. Sun, A. Zholents ANL, Lemont, Illinois, USA
	Funding: DOE grant No. DE-SC0009914 and DE-SC0018559 Tapering Enhanced Stimulated Superradiant Amplification (TESSA) allows to increase the efficiency of Free Electron Laser (FEL) based radiation generation from ~0.1% to 10% by using intense seed laser pulses, strongly tapered undulators and prebunched electron beams [1]. Initial results validating this method have already been obtained at 10 µm wavelength at Brookhaven National Laboratory [2]. We will present the design of an experiment to demonstrate the TESSA scheme at high gain and shorter wavelength (266 nm) using the APS injector linac at Argonne National Labor-atory (ANL) to obtain conversion efficiency of up to 10%. Undulator and focusing lattice design, as well as beam dynamics and diagnostics for this experiment will be discussed. An extension of the experiment to include the possibility of multi-bunch linac operation and an optical cavity around the undulator to operate in the TESSO regime will also be presented [3]. [1] J. Duris et al., New J. Phys. 17 063036 (2015) [2] N Sudar et al., Physical review letters, 117, 174801 (2016) [3] J. Duris et al., Physical Review Accelerators and Beams 21, 080705 (2018)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP073
About •	paper received ※ 20 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019
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THP081	PolFEL — New Facility in Poland	FEL, electron, radiation, photon	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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THP084	Status of the Soft X-Ray Laser (SXL) Project at MAX IV Laboratory	FEL, linac, simulation, undulator	749
	F. Curbis, J. Andersson, L. Isaksson, M. Kotur, F. Lindau, E. Mansten, M.A. Pop, H. Tarawneh, P.F. Tavares, S. Thorin, S. Werin MAX IV Laboratory, Lund University, Lund, Sweden S. Bonetti, A. Nilsson Stockholm University, Stockholm, Sweden V.A. Goryashko Uppsala University, Uppsala, Sweden P. Johnsson, W. Qin Lund University, Lund, Sweden M. Larsson, P.M. Salén FYSIKUM, AlbaNova, Stockholm University, Stockholm, Sweden J.A. Sellberg KTH Physics, Stockholm, Sweden
	Funding: The work is supported by Knut and Alice Wallenberg foundation. A Soft X-ray Laser project (the SXL) aiming to produce FEL radiation in the range of 1 to 5 nm is currently in a conceptual design phase and a report on the design is expected to be delivered by March 2021. The FEL will be driven by the existing 3 GeV linac at MAX IV laboratory, which also serves as injector for the two storage rings. The science case has been pushed by a large group of mainly Swedish users and consists of experiments ranging from AMO physics to condensed matter, chemistry and imaging in life science. In this contribution, we will present the current conceptual design of the accelerator and the FEL operation modes together with a general overview of the beamline and experimental station. In particular design options for the FEL will be discussed in conjunction with the features of the electron beam from the MAX IV linac and the connection with the proposed experiments.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP084
About •	paper received ※ 21 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019
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Paper

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MOA02

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

FEL, laser, electron, free-electron-laser

7

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

We report on the successful operation of a Free Electron Laser (FEL) in the Echo Enabled Harmonic Generation (EEHG) scheme at the FERMI facility at Sincrotrone Trieste. The experiment required a modification of the FEL-2 undulator line which, in normal operation, uses two stages of high-gain harmonic generation separated by a delay line. In addition to a new seed laser, the dispersion in the delay-line was increased, the second stage modulator changed and a new manipulator installed in the delay-line chicane hosting additional diagnostic components. With this modified setup we have demonstrated the first evidence of strong exponential gain in a free electron laser operated in EEHG mode at wavelengths as short as 5 nm.

Slides MOA02 [5.133 MB]

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

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TUP001

Extension of the PITZ Facility for a Proof-of-Principle Experiment on THz SASE FEL

radiation, FEL, undulator, electron

38

P. Boonpornprasert, G.Z. Georgiev, G. Koss, M. Krasilnikov, X. Li, F. Mueller, A. Oppelt, S. Philipp, H. Shaker, F. Stephan, T. Weilbach
DESY Zeuthen, Zeuthen, Germany
Z.G. Amirkhanyan
CANDLE SRI, Yerevan, Armenia

The Photo Injector Test Facility at DESY in Zeuthen (PITZ) has been proposed as a suitable facility for research and development of an accelerator-based THz source prototype for pump-probe experiments at the European XFEL. A proof-of-principle experiment to generate THz SASE FEL radiation by using an LCLS-I undulator driven by an electron bunch from the PITZ accelerator has been planned and studied. The undulator is foreseen to be installed downstream from the current PITZ accelerator, and an extension of the accelerator tunnel is necessary. Radiation shielding for the extended tunnel was designed, and construction works are finished. Design of the extended beamline is ongoing, not only for this experiment but also for other possible experiments. Components for the extended beamline, including magnets for beam transport, a chicane bunch compressor, electron beam diagnostics devices, and THz radiation diagnostics devices have been studied. An overview of these works will be presented in this paper.

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TUP002

Progress in Preparing a Proof-of-Principle Experiment for THz SASE FEL at PITZ

laser, FEL, undulator, flattop

41

X. Li, P. Boonpornprasert, Y. Chen, G.Z. Georgiev, J.D. Good, M. Groß, P.W. Huang, I.I. Isaev, C. Koschitzki, M. Krasilnikov, S. Lal, O. Lishilin, G. Loisch, D. Melkumyan, R. Niemczyk, A. Oppelt, H.J. Qian, H. Shaker, G. Shu, F. Stephan, G. Vashchenko
DESY Zeuthen, Zeuthen, Germany

A proof-of-princle experiment for a THz SASE FEL is undergoing preparation at the Photo Injector Test facility at DESY in Zeuthen (PITZ), as a prototype THz source for pump-probe experiments at the European XFEL, which could potentially provide up to mJ/pulse THz radiation while maintaining the identical pulse train structure as the XFEL pulses. In the proof-of-principle experiment, LCLS-I undulators will be installed to generate SASE radiation in the THz range of 3-5 THz from electron bunches of 16-22 MeV/c. One key design is to obtain the peak current of nearly 200 A from the heavily charged bunches of a few nC. In this paper, we report our simulation results on the optimization of the space charge dominated beam in the photo injector and the following transport line with two cathode laser setups. Experimental results based on a short Gaussian laser will also be discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP002

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

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TUP003

Design of a Magnetic Bunch Compressor for the THz SASE FEL Proof-of-Principle Experiment at PITZ

FEL, radiation, dipole, undulator

45

H. Shaker, P. Boonpornprasert, G.Z. Georgiev, G. Koss, M. Krasilnikov, X. Li, A. Lueangaramwong, F. Mueller, A. Oppelt, S. Philipp, F. Stephan, G. Vashchenko, T. Weilbach
DESY Zeuthen, Zeuthen, Germany

For pump-probe experiments at the European XFEL, a THz source is required to produce intense THz pulses at the same repetition rate as the X-ray pulses from XFEL. Therefore, an accelerator-based THz source with identical electron source as European XFEL was suggested and proof-of-principle experiments utilizing an LCLS I undulator will be performed at the Photo Injector Test Facility at DESY in Zeuthen (PITZ). The main idea is to use a 4nC beam for maximum SASE radiation but to allow different radiation regimes a magnetic bunch compressor can be used. This helps e.g. to reduce the saturation length inside the undulator and also to study super-radiant THz radiation. In this paper a design of a chicane type magnetic bunch compressor using HERA corrector magnets is presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP003

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

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TUP004

A Superradiant THz Undulator Source for XFELs

undulator, FEL, electron, radiation

48

T. Tanikawa, G. Geloni, S. Karabekyan, S. Serkez
EuXFEL, Schenefeld, Germany
V.B. Asgekar
University of Pune, Pune, India
S. Casalbuoni
KIT, Eggenstein-Leopoldshafen, Germany
M. Gensch
Technische Universität Berlin, Berlin, Germany
M. Gensch
DLR, Berlin, Germany
S. Kovalev
HZDR, Dresden, Germany

The European XFEL has successfully achieved first lasing in 2017 and meanwhile three SASE FEL beamlines are in operation. An increasing number of users has great interest in a specific type of two-color pump-probe experiments in which high-field THz pulses are employed to drive nonlinear processes and dynamics in matter selectively. Here, we propose to use a 10-period superconducting THz undulator to provide intense, narrowband light pulses tunable in wide range between 3 and 100 THz. The exploitation of superconducting technology allows us to meet the challenge of generating such low photon energy radiation despite the very high electron beam energy at the European XFEL. In this presentation, we will present the latest development concerning THz undulator design and present the expected THz pulse properties for the case of the European XFEL.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP004

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

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TUP007

Experience with the Superradiant THz User Facility Driven by a Quasi-CW SRF Accelerator at ELBE

detector, electron, radiation, SRF

56

M. Bawatna, B.W. Green
HZDR, Dresden, Germany

Instabilities in beam and bunch parameters, such as bunch charge, beam energy or changes in the phase or amplitude of the accelerating field in the RF cavities can be the source of noise in the various secondary sources driven by the electron beam. Bunch charge fluctuations lead to intensity instabilities in the super-radiant THz sources. The primary electron beam driving the light sources has a maximum energy of 40 MeV and a maximum current of 1.6 mA. Depending on the mode of operation required, there are two available injectors in use at ELBE. The first is the thermionic injector, which is used for regular operating modes and supports repetition rates up to 13 MHz and bunch charges up to 100 pC. The second is the SRF photo-cathode injector, which is used for experiments that may require lower emittance or higher bunch charges of up to 1 nC. It has a maximum repetition rate of 13 MHz, which can be adjusted to lower rates if desired, also including different macro pulse modes of operation. In this contribution, we will present our work in the pulse-resolved intensity measurement that allows for correction of intensity instabilities.

Poster TUP007 [0.658 MB]

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

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TUP012

Smith-Purcell Radiation Emitted by Pico-second Electron Bunches from a 30 keV Photo-Electron Gun

electron, radiation, laser, gun

66

M.R. Asakawa, S. Yamaguchi
Kansai University, Osaka, Japan

In this paper, an experiment to generate Smith-Purcell radiation using pico-second electron bunches is reported. The electron bunch was produced by a DC 30 keV photo-electron electron gun driven by a 100 fs Ti:sapphire laser. The charge of the bunch varied from 1 pC to 300 pC by changing the laser power. Smith-Purcell radiation experiment was performed with the central part of the entire electron bunch. Estimation of pulsewidth of the bunch based on the envelope equation showed that the pulsewidth of the bunch at the anode electrode increased from 0.8 ps to 3.2 ps as the bunch charge increase from 0.1 pC to 11 pC. Such electron bunch was traveled along the surface of the metallic grating with a period of 2 mm. The radiation wavelength was estimated to be 4 mm at an obserbation angle of 10 degree. The radiation power was measured by a bolometer and quadraticallly increased with the bunch charge. Numerical simulation of this experiment indicated the enhancement of the harmonic components of the radiation. We are now constructing a THz-TDS system to measure the time-trace of the electric field of the radiation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP012

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paper received ※ 14 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019

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TUP018

Superradiant Emission of Electron Bunches Based on Cherenkov Excitation of Surface Waves in 1D and 2D Periodical Lattices: Theory and Experiments

electron, GUI, radiation, simulation

80

A. Malkin, N.S. Ginzburg, A. Sergeev, I.V. Zheleznov, I.V. Zotova
IAP/RAS, Nizhny Novgorod, Russia
M.I. Yalandin
RAS/IEP, Ekaterinburg, Russia
V.Yu. Zaslavsky
UNN, Nizhny Novgorod, Russia

Funding: The work was supported by RFBR grant no. 17-08-01072
In recent years, significant progress was achieved in generation of high-power ultrashort microwave pulses based on superradiance (SR) of electron bunches extended in the wavelength scale. In this process, coherent emission from the entire volume of the bunch occurs due to the development of microbunching and slippage of the wave with respect to electrons. An obvious method for generation of high-power sub-THz radiation is the implementation of oversized periodical slow-wave structures where evanescent surface waves can be excited. We report of the experiments on Cherenkov generation of 150 ps SR pulses with a central frequency of 0.14 THz, and an extremely high peak power up to 70 MW. In order to generate spatially coherent radiation in shorter wavelength ranges (including THz band) in strongly oversized waveguiding systems, we propose a slow wave structure with double periodic corrugation (2D SWS). Using the quasi-optical theory and PIC simulations, we demonstrate the applicability of such 2D SWS and its advantages against traditional 1D SWS. Proof of principle experiments on observation G-band Cherenkov SR in 2D SWS are currently in progress.

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TUP019

Regime of Multi-Stage Non-Resonant Trapping in Free Electron Lasers

electron, FEM, FEL, wiggler

83

A.V. Savilov, I.V. Bandurkin, Yu.S. Oparina, N.Yu. Peskov
IAP/RAS, Nizhny Novgorod, Russia

Funding: This work is supported by the RFBR (grants #18-02-40009, #18-02-00765) and by the IAP RAS Project 0035-2019-0001.
We describe three works united by the idea of the non-resonant regime [1] providing an effective trapping in a beam with a great energy spread. In this regime, the "bucket" corresponding to the resonant electron-wave interaction passes through the electron layer on the energy-phase plane and traps a fraction of electrons. (I) Operability of this regime was demonstrated in the high-efficient 0.8 MeV Ka-band FEM-amplifier [2]. (II) In short-wavelength FELs the multi-stage trapping in several consecutive sections can be organized [3]. In each section a small e-beam fraction is trapped due to a weak electron-wave interaction. However, repetition of this process from section to section involves in the interaction almost the whole e-beam. We describe efficiency enhancement and improving the frequency wave spectrum in multi-stage SASE FELs. (III) The multi-stage amplification of a single-frequency wave signal can provide cooling of the electron bunch. In this regime, tapering of every section is provided such that the "bucket" goes from maximal initial electron energy down to the minimal one and moves down energies of trapped electrons.
[1] A.Savilov et al., Nucl. Instr. Meth. A, vol. 507, p.158, 2003
[2] A.Kaminsky et al., Int. Conf. IRMMW-THz 2018, art. 4057938
[3] S.Kuzikov, A.Savilov, Phys. Plasmas, vol. 25, p.113114, 2018

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TUP024

Electronic Modulation of the FEL-Oscillator Radiation Power Driven by ERL

FEL, radiation, electron, controls

98

O.A. Shevchenko, E.V. Bykov, Ya.V. Getmanov, S.S. Serednyakov, S.V. Tararyshkin
BINP SB RAS, Novosibirsk, Russia
M.V. Fedin, A.R. Melnikov, S.L. Veber
International Tomography Center, SB RAS, Novosibirsk, Russia
Ya.V. Getmanov, S.S. Serednyakov
NSU, Novosibirsk, Russia

FEL oscillators usually operate in CW mode and produce periodic train of radiation pulses but some user experiments require modulation of radiation power. Conventional way to obtain this modulation is using of mechanical shutters but it cannot provide very short switching time and may lead to decreasing of the radiation beam quality. Another way could be based on the electron beam current modulation but it cannot be used in the ERL. We propose a simple way of fast control of the FEL lasing which is based on periodic phase shift of electron bunches with respect to radiation stored in optical cavity. The phase shift required to suppress lasing is relatively small and it does not change significantly repetition rate. This approach has been realized at NovoFEL facility. It allows to generate radiation macropulses of desirable length down to several microseconds (limited by quality factor of optical cavity and FEL gain) which can be synchronized with external trigger. We present detailed description of electronic power modulation scheme and discuss the results of experiments.

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

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TUP035

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

laser, electron, free-electron-laser, bunching

126

G. Marcus, D.K. Bohler, Y. Ding, W.M. Fawley, Y. Feng, E. Hemsing, Z. Huang, J. Krzywiński, A.A. Lutman, D.F. Ratner
SLAC, Menlo Park, California, USA

Measurements of the soft X-ray, self-seeding spectrum at the LCLS free-electron laser generally display a pedestal-like distribution around the central seeded wavelength that degrades the spectral purity. We have investigated the detailed experimental characteristics of this pedestal and found that it is comprised of two separate components: (1) normal SASE whose total strength is nominally insensitive to energy detuning and laser heater (LH) strength; (2) sideband-like emission whose strength positively correlates with that of the amplified seed and negatively with energy detuning and LH strength. We believe this latter, non-SASE component arises from comparatively long wavelength amplitude and phase modulations of the main seeded radiation line. Its shot-to-shot variability and LH sensitivity suggests an origin connected to growth of the longitudinal microbunching instability on the electron beam. Here, we present experimental results taken over a number of shifts that illustrate the above mentioned characteristics.

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

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

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TUP038

Axial Symmetry in Spontaneous Undulator Radiation for XFELO Two-Bunch Experiment

FEL, electron, laser, radiation

134

Y.S. Li
University of Chicago, Chicago, Illinois, USA
K. Kim, R.R. Lindberg
ANL, Lemont, Illinois, USA

Funding: U.S. DOE, Office of Science, Office of BES, under Contract No. DE-AC02-06CH11357 and National Science Foundation under Award No. PHY-1549132, the Center for Bright Beams.
A well known discrepancy exists between 2D and 3D FEL simulation codes with respect to the radiation field intensity prior to the exponential gain regime [1]. This can be qualitatively explained by the fact that the 3D field representation preserves many more modes than does the axisymmetric field solved for by a 2D code. In this paper, we seek to develop an analytical model that quantifies this difference. We begin by expanding the spontaneous undulator radiation field as a multipole series, whose lowest order mode is axisymmetric. This allows us to calculate the difference in predicted intensity. Next, we confirm these results with numerical calculation and existing FEL codes GINGER and GENESIS. Finally, we discuss the implications of this study with respect to the XFELO two-bunch experiment to be conducted at LCLS-II.
[1] Z. Huang and K.-J. Kim, "Review of X-ray free-electron laser theory", Phys. Rev. ST-AB, vol. 10, p. 034801, 2007.

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

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TUP050

Comparison Between, and Validation Against an Experiment of, a Slowly-varying Envelope Approximation Code and a Particle-in-Cell Simulation Code for Free-Electron Lasers

undulator, FEL, simulation, electron

153

P. Traczykowski, L.T. Campbell, J. Henderson, B.W.J. MᶜNeil
USTRAT/SUPA, Glasgow, United Kingdom
L.T. Campbell, J. Henderson, P. Traczykowski
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
H. Freund
University of New Mexico, Albuquerque, USA
B.W.J. MᶜNeil, P. Traczykowski
Cockcroft Institute, Warrington, Cheshire, United Kingdom
P.J.M. van der Slot
Mesa+, Enschede, The Netherlands

Free-electron laser simulation codes employ either the Slowly-Varying Envelope Approximation (SVEA) or a Particle-in-Cell (PiC) formulation. Maxwell’s equations are averaged over the fast time scale in the SVEA so that there is no need to resolve the wave period. In contrast, the fast oscillation is retained in PiC codes. As a result, the SVEA codes are much less computationally intensive and are used more frequently than PiC codes. While the orbit dynamics in PiC codes and some SVEA Codes (MEDUSA and MINERVA) use the full unaveraged Lorentz force equations, some SVEA codes use the Kroll-Morton-Rosenbluth (KMR) approximation (GENESIS, GINGER, FAST, and TDA3D). Steady-state simulation comparisons [1] have appeared in the literature between different codes using the averaged and unaveraged particle dynamics. Recently, a comparison between three KMR SVEA codes (GENESIS, GINGER, and FAST) and the PUFFIN PiC code in the time-dependent regime has been reported [2]. In this paper, we present a comparison between the unaveraged PiC code PUFFIN, the unaveraged SVEA code MINERVA for the time-dependent simulation of SASE free-electron lasers with the experimental measurements from SPARC SASE FEL at ENEA Frascati.
[1] S.G. Biedron et al., NIMA 445, 110 (2000).
[2] B. Garcia et al., paper presented at the 38th International Free Electron Laser Conference, Santa Fe, New Mexico, 20 - 25 August 2017.

Poster TUP050 [0.908 MB]

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paper received ※ 02 August 2019 paper accepted ※ 28 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

photon, FEL, 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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paper received ※ 21 August 2019 paper accepted ※ 12 September 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, photon, 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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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP062

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

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TUP076

Seeding R&D at sFLASH

electron, laser, FEL, free-electron-laser

230

C. Lechner, S. Ackermann, R.W. Aßmann, B. Faatz, V. Grattoni, I. Hartl, S.D. Hartwell, R. Ivanov, T. Laarmann, T. Lang, M.M. Mohammad Kazemi, G. Paraskaki, A. Przystawik, J. Zheng
DESY, Hamburg, Germany
A. Azima, H. Biss, M. Drescher, W. Hillert, V. Miltchev, J. Roßbach
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
S. Khan
DELTA, Dortmund, Germany

Funding: Work supported by Federal Ministry of Education and Research of Germany under contract No. 05K13GU4, 05K13PE3, and 05K16PEA.
Free-electron lasers (FELs) based on the self-amplified spontaneous emission (SASE) principle generate photon pulses with typically poor longitudinal coherence. FEL seeding techniques greatly improve longitudinal coherence by initiating FEL amplification in a controlled way using coherent light pulses. The sFLASH experiment installed at the FEL user facility FLASH at DESY in Hamburg is dedicated to the study of external seeding techniques. In this paper, the layout of the sFLASH seeding experiment is presented and an overview of recent developments is given.

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paper received ※ 30 September 2019 paper accepted ※ 17 October 2019 issue date ※ 05 November 2019

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TUP092

XFEL Third Harmonic Statistics Measurement at LCLS

FEL, photon, undulator, 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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TUD02

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

FEL, cavity, laser, photon

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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TUD03

Fine and Hyperfine Structure of FEL Emission Spectra

FEL, electron, radiation, laser

276

V.V. Kubarev, Ya.V. Getmanov, O.A. Shevchenko
BINP SB RAS, Novosibirsk, Russia
S. Bae, Y.U. Jeong
KAERI, Daejon, Republic of Korea

This paper presents the results of experimental investigations of the fine and hyperfine spectral structures of the Novosibirsk free-electron laser (NovoFEL) and the compact free-electron laser of the Korea Atomic Energy Research Institute (KAERI FEL) by means of the optimal instruments, resonance Fabry-Perot interferometers. The very high coherence of the NovoFEL spectrum was measured in regimes with one pulse circulating inside its optical resonator (the coherence length is 7 km, and the relative width of the hyperfine structure lines is 2E-8) and with total absence of coherence between two circulating pulses, i.e. the fine structure. Sixty pulses circulate simultaneously inside the KAERI FEL optical resonator, and the measured coherence length on average covers ten pulses (the coherence length is 1 m; the relative width of the fine structure lines is 10^-4).

Slides TUD03 [3.177 MB]

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WEB01

Identification and Mitigation of Smoke-Ring Effects in Scintillator-Based Electron Beam Images at the European XFEL

FEL, electron, diagnostics, ECR

301

G. Kube, S. Liu, A.I. Novokshonov, M. Scholz
DESY, Hamburg, Germany

Standard transverse beam profile measurements at the European XFEL are based on scintillating screen monitors using LYSO:Ce. While it is possible to resolve beam sizes down to a few micrometers with this scintillator, the experience during the XFEL commissioning showed that the measured emittance values were significantly larger than the expected ones. In addition, beam profiles measured at bunch charges of a few hundred pC showed a ’smoke ring’ structure. While coherent OTR emission and beam dynamical influence can be excluded, it is assumed that the profile distortions are caused by effects from the scintillator material. Following the experience in high energy physics, a simple model was developed which takes into account quenching effects of excitonic carriers inside a scintillator in a heuristic way. Based on this model, the observed beam profiles can be understood qualitatively. Together with the model description, first comparisons with experimental results will be shown. Possible new scintillator materials suitable for beam profile diagnostics and first test results from beam measurements will be presented.

Slides WEB01 [5.057 MB]

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WEB02

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

FEL, electron, operation, 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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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEB02

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

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WEP016

Precise Laser-to-RF Synchronization of Photocathode Lasers

laser, timing, electron, controls

364

M. Titberidze, M. Felber, T. Kozak, T. Lamb, J. Müller, H. Schlarb, S. Schulz, C. Sydlo, F. Zummack
DESY, Hamburg, Germany

RF photo-injectors are used in various large, mid and small-scale accelerator facilities such as X-ray Free Electron Lasers (XFELs), external injection-based laser-driven plasma accelerators (LPAs) and ultrafast electron diffraction (UED) sources. Many of these facilities require a high precision synchronization of the photo-injector laser system, either because of beam dynamics reasons or the photo-injector directly impacting pump-probe experiments carried out to study physical processes on femtosecond timescales. It is thus crucial to achieve synchronization in the order of 10 fs rms or below between the photocathode laser and the RF source driving the RF gun. In this paper, we present the laser-to-RF synchronization setup employed to lock a commercial near-infrared (NIR) photocathode laser oscillator to a 2.998 GHz RF source. Together with the first results achieving ~ 10 fs rms timing jitter in the measurement bandwidth from 10 Hz up to 1 MHz, we describe an advanced synchronization setup as a future upgrade, promising even lower timing jitter and most importantly long-term timing drift stability.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP016

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

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WEP024

1.3 GHz Solid State Power Amplifier for the Buncher in CTFEL Facility

electron, FEL, cavity, bunching

371

T.H. He, C.L. Lao, P. Li, X. Luo, L.J. Shan, K. Zhou
CAEP/IAE, Mianyang, Sichuan, People’s Republic of China

The THz Free Electron Laser facility (CAEP THz FEL, CTFEL) of the China Academy of Engineering Physics uses high quality electron beams to generate high average power terahertz radiations. A 1.3 GHz RF buncher is used in front of the superconducting linear accelerator of the CTFEL facility to improve the electron beams quality. The RF buncher is driven by a solid state power amplifier (SSPA), and the SSPA is feedback controlled by a low level RF (LLRF) control system to ensure the high stability of the amplitude and phase of the bunching field in the buncher cavity. The SSPA operates at 1.3 GHz and outputs 0 to 5 kW of continuous wave power. This paper mainly introduces the principle and composition of the SSPA, and presents some experiments on the RF buncher driven by the SSPA.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP024

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paper received ※ 15 August 2019 paper accepted ※ 27 August 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, simulation, electron, photon

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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WEP081

Design and Development of High-Speed Data Acquisition System and Online Data Processing with a Heterogeneous FPGA/GPU Architecture

FPGA, real-time, GPU, data-acquisition

510

M. Bawatna, J.-C. Deinert, O. Knodel, S. Kovalev
HZDR, Dresden, Germany
R.G. Spallek
Technische Universität Dresden, Dresden, Germany

The superradiant THz sources at TELBE facility is based on the new class of accelerator-driven terahertz (THz) radiation sources that provide high repetition rates up to 13 MHz, and flexibility of tuning the THz pulse form. The THz pulses are used for the excitation of materials of interest, about two orders of magnitude higher than state-of-the-art tabletop sources. Time-resolved experiments can be performed with a time resolution down to 30 femtoseconds (fs) using the novel pulse-resolved Data Acquisition (DAQ) system. However, the increasing demands in improving the flexibility, data throughput, and speed of the DAQ systems motivate the integration of reconfigurable processing units close to the new detectors to accelerate the processing of tens of GigaBytes of data per second. In this paper, we introduce our online ultrafast DAQ system that uses a GPU platform for real-time image processing, and a custom high-performance FPGA board for interfacing the image sensors and provide a continuous data transfer.

Poster WEP081 [0.830 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP081

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paper received ※ 18 August 2019 paper accepted ※ 25 August 2019 issue date ※ 05 November 2019

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THB02

Understanding 1D to 3D Coherent Synchrotron Radiation Effects

simulation, radiation, emittance, electron

578

A.D. Brynes
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Collective effects such as coherent synchrotron radiation (CSR) can have a strong influence of the properties of an electron bunch with respect to the quality of the FEL light that it produces. In particular, CSR experienced by a bunch on a curved trajectory can increase the transverse emittance of a beam. In this contribution, we present an extension to the well-established 1D theory of CSR by accounting fully for the forces experienced in the entrance and exit transients of a bending magnet. A new module of the General Particle Tracer (GPT) tracking code was developed for this study, showing good agreement with theory. In addition to this analysis, we present experimental measurements of the emittance growth experienced in the FERMI bunch compressor chicane as a function of bunch length. When the bunch undergoes extreme compression, the 1D theory breaks down and is no longer valid. A comparison between the 1D theory, experimental measurements and a number of codes which simulate CSR differently are presented, showing better agreement when the transverse properties of the bunch are taken into account.

Slides THB02 [3.591 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THB02

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

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THP041

Interaction of Powerful Electro-Magnetic Fields With Bragg Reflectors

laser, simulation, FEL, electron

673

I. Bahns, W. Hillert, P. Rauer, J. Roßbach
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
H. Sinn
EuXFEL, Schenefeld, Germany

Funding: supported by BMBF FKZ 05K16GU4
The interaction of an X-ray free electron laser (XFEL) with a Bragg Reflector can cause a change of the lattice constant, which has a direct influence on the stability of the reflection conditions [1] and can also excite modes of vibration [2]. The dynamical thermoelastic effects of the photon-matter-interaction are simulated with a finite-element-method (FEM) using the assumptions of continuums mechanics. To compare the simulation results with measured signals, a Michelson interferometer with ultrafast photodiodes (risetime <175ps, bandwith >2GHz) has been built up. To test the experimental setup in an in-house environment a pulsed UV laser is used to introduce a temporal displacement field in a silicon crystal created by about 0.26µJ of absorbed energy. The measured signal is in agreement with the FEM simulation and has shown that if averaging over thousands of pulses is applied a resolution <0.5pm is feasible. This makes this experimental setup useful to investigate the X-ray-matter-interaction of Bragg reflectors at modern X-ray facilities.
[1] S. Stoupin et al., Physical Review B 86.5 (2012): 054301.
[2] B. Yang, S. Wang and J. Wu, J. Synchrotron Rad. (2018) 25, 166-176.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP041

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paper received ※ 23 August 2019 paper accepted ※ 31 October 2019 issue date ※ 05 November 2019

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THP069

Observations on Microbunching of Electrons in Laser-Driven Plasma Accelerators and Free-Electron Lasers

FEL, laser, electron, bunching

722

A.H. Lumpkin
Fermilab, Batavia, Illinois, USA
M. Downer, M. LaBerge
The University of Texas at Austin, Austin, Texas, USA
D.W. Rule
Private Address, Silver Spring, USA

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The periodic longitudinal density modulation of relativistic electrons at the resonant wavelength (microbunching) is a fundamental aspect of free-electron lasers (FELs). In one case, microbunching fractions reached 20% at saturation of a self-amplified spontaneous emission (SASE) FEL resulting in gains of 1 million at 530 nm [1]. In that experiment the z-dependent gain of coherent optical transition radiation (COTR) was also measured. In laser-driven plasma accelerators (LPAs), microbunching at visible wavelengths has also been recently reported as evidenced by significant COTR enhancements measured in near-field and far-field images on a single shot for the first time [2]. An analytical model for COTR interferometry (COTRI) addresses both cases. In the FEL, one identified microbunched transverse cores of 25-100 microns while in the LPA the reported transverse sizes at the exit of the LPA were a few microns. In the latter case, signal enhancements of nearly 100, 000 and extensive fringes out to 30 mrad in angle space were recorded. The broadband microbunching observed in the LPA case could act as a seed for a SASE FEL experiment with tunability in principle over the visible regime.
[1] A.H. Lumpkin et al., Phys. Rev. Lett. 88, No.23, 234801 (2002).
[2] A.H. Lumpkin, M. LaBerge, D.W. Rule et al., Proceedings of AAC18, (IEEE), (2019).

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP069

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

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THP073

Status Update for the High Gain High Efficiency TESSA-266 Experiment

undulator, quadrupole, laser, electron

730

Y. Park, D.K. Dang, P.E. Denham, P. Musumeci, N.S. Sudar
UCLA, Los Angeles, USA
R.B. Agustsson, T.J. Campese, I.I. Gadjev, A.Y. Murokh
RadiaBeam, Los Angeles, California, USA
C.C. Hall, S.D. Webb
RadiaSoft LLC, Boulder, Colorado, USA
Y. Sun, A. Zholents
ANL, Lemont, Illinois, USA

Funding: DOE grant No. DE-SC0009914 and DE-SC0018559
Tapering Enhanced Stimulated Superradiant Amplification (TESSA) allows to increase the efficiency of Free Electron Laser (FEL) based radiation generation from ~0.1% to 10% by using intense seed laser pulses, strongly tapered undulators and prebunched electron beams [1]. Initial results validating this method have already been obtained at 10 µm wavelength at Brookhaven National Laboratory [2]. We will present the design of an experiment to demonstrate the TESSA scheme at high gain and shorter wavelength (266 nm) using the APS injector linac at Argonne National Labor-atory (ANL) to obtain conversion efficiency of up to 10%. Undulator and focusing lattice design, as well as beam dynamics and diagnostics for this experiment will be discussed. An extension of the experiment to include the possibility of multi-bunch linac operation and an optical cavity around the undulator to operate in the TESSO regime will also be presented [3].
[1] J. Duris et al., New J. Phys. 17 063036 (2015)
[2] N Sudar et al., Physical review letters, 117, 174801 (2016)
[3] J. Duris et al., Physical Review Accelerators and Beams 21, 080705 (2018)

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP073

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

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THP081

PolFEL — New Facility in Poland

FEL, electron, radiation, photon

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.

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

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THP084

Status of the Soft X-Ray Laser (SXL) Project at MAX IV Laboratory

FEL, linac, simulation, undulator

749

F. Curbis, J. Andersson, L. Isaksson, M. Kotur, F. Lindau, E. Mansten, M.A. Pop, H. Tarawneh, P.F. Tavares, S. Thorin, S. Werin
MAX IV Laboratory, Lund University, Lund, Sweden
S. Bonetti, A. Nilsson
Stockholm University, Stockholm, Sweden
V.A. Goryashko
Uppsala University, Uppsala, Sweden
P. Johnsson, W. Qin
Lund University, Lund, Sweden
M. Larsson, P.M. Salén
FYSIKUM, AlbaNova, Stockholm University, Stockholm, Sweden
J.A. Sellberg
KTH Physics, Stockholm, Sweden

Funding: The work is supported by Knut and Alice Wallenberg foundation.
A Soft X-ray Laser project (the SXL) aiming to produce FEL radiation in the range of 1 to 5 nm is currently in a conceptual design phase and a report on the design is expected to be delivered by March 2021. The FEL will be driven by the existing 3 GeV linac at MAX IV laboratory, which also serves as injector for the two storage rings. The science case has been pushed by a large group of mainly Swedish users and consists of experiments ranging from AMO physics to condensed matter, chemistry and imaging in life science. In this contribution, we will present the current conceptual design of the accelerator and the FEL operation modes together with a general overview of the beamline and experimental station. In particular design options for the FEL will be discussed in conjunction with the features of the electron beam from the MAX IV linac and the connection with the proposed experiments.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP084

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

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