02 Photon Sources and Electron Accelerators
A06 Free Electron Lasers

Paper	Title	Page
MOXBA01	Beam Commissioning of PAL-XFEL	6
	J.H. Han PAL, Pohang, Kyungbuk, Republic of Korea
	The Pohang Accelerator Laboratory X-ray Free electron Laser (PAL-XFEL) project aims at the generation of X-ray FEL radiation for photon users. The machine consists of a 10 GeV normal-conducting S-band linear accelerator (linac) and two undulator beamlines initially. The hard X-ray beamline will provide FEL radiation between 0.6 and 0.1 nm or shorter. The soft X-ray line will provide FEL radiation between 4.5 and 1 nm. The linac and hard X-ray beamline construction was complete by the end of 2015. The installation of the soft X-ray line is ongoing. High power RF conditioning of the linac started in late autumn 2015. Beam commissioning of the linac started in April 2016. We report the beam commissioning status.
	Slides MOXBA01 [4.978 MB]
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MOPMB005	Study of Short Bunches at the Free Electron Laser CLIO	78
	V. Khodnevych, N. Delerue, S. Jenzer LAL, Orsay, France J.P. Berthet, F. Glotin, J.-M. Ortega, R. Prazeres CLIO/ELISE/LCP, Orsay, France V. Khodnevych National Taras Shevchenko University of Kyiv, The Faculty of Physics, Kyiv, Ukraine
	Funding: The authors are grateful for the funding received from the French ANR (contract ANR-12-JS05-0003-01). CLIO is a Free Electron Laser based on a thermionic electron gun. In its normal operating mode it delivers electron 8 pulses but studies are ongoing to shorten the pulses to about 1 ps. We report on simulations showing how the pulse can be shortened and the expected signal yield from several bunch length diagnostics (Coherent Transition Radiation, Coherent Smith Purcell Radiation).
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MOPMW037	FEL Simulation Using Distributed Computing	483
	J. Einstein, S. Biedron, H. Freund, S.V. Milton, P.J.M. van der Slot CSU, Fort Collins, Colorado, USA G. Bernabeu Altayo Fermi National Accelerator Laboratory, Batavia, Illinois, USA S. Biedron University of Ljubljana, Faculty of Electrical Engineering, Ljubljana, Slovenia J. Einstein Fermilab, Batavia, Illinois, USA P.J.M. van der Slot Twente University, Laser Physics and Non-Linear Optics Group, Enschede, The Netherlands
	While simulation tools are available and have been used regularly for simulating light sources, the increasing availability and lower cost of GPU-based processing opens up new opportunities. This poster highlights a method of how accelerating and parallelizing code processing through the use of COTS software interfaces.
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MOPOW003	RF Phase Jitter Consideration in Bunch Compression	704
	T.K. Charles, D.M. Paganin Monash University, Faculty of Science, Clayton, Victoria, Australia M.J. Boland, R.T. Dowd SLSA, Clayton, Australia
	Error propagation of RF phase jitter is analysed for various linac layout configurations and the sensitivity of the compression ratio due to RF phase jitter is analysed. Multiple sources of jitter have the opportunity to destructively interfere, and (perhaps counter intuitively) found to not add in quadrature. Results are compared to Elegant simulations.
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MOPOW004	Electron Trajectory Caustic Formation Resulting in Current Horns present in Bunch Compression	708
	T.K. Charles, D.M. Paganin Monash University, Faculty of Science, Clayton, Victoria, Australia M.J. Boland, R.T. Dowd SLSA, Clayton, Australia
	Current horns are ubiquitous in Free Electron Laser (FEL) bunch compression. In this paper, we analyse the formation of these current spikes and identify the cause as caustic formation in the electron trajectories. We also present a possible solution to avoid or mitigate the current horns from developing through using optical linearization.
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MOPOW005	First Electron Beam Measurements on COXINEL	712
	T. André, I.A. Andriyash, C. Basset, C. Benabderrahmane, P. Berteaud, S. Bonnin, F. Bouvet, F. Briquez, L. Cassinari, L. Chapuis, M.-E. Couprie, D. Dennetière, Y. Dietrich, M. Diop, J.P. Duval, M.E. El Ajjouri, T.K. El Ajjouri, P. Gattoni, C. Herbeaux, N. Hubert, M. Khojoyan, M. Labat, N. Leclercq, A. Lestrade, A. Loulergue, O. Marcouillé, F. Marteau, P. Pierrot, F. Polack, F. Ribeiro, J.P. Ricaud, P. Rommeluère, M. Sebdaoui, K.T. Tavakoli, M.-A. Tordeux, M. Valléau, J. Vétéran, D. Zerbib, C. de Olivera SOLEIL, Gif-sur-Yvette, France S. Bielawski, C. Evain, C. Szwaj PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France J. Gautier, E. Guillaume, G. Lambert, B. Mahieu, V. Malka, A. Rousse, K. Ta Phuoc, C. Thaury LOA, Palaiseau, France E. Roussel Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	The ERC grant COXINEL aims at demonstrating experimentally Free Electron Laser (FEL) amplification with electrons generated by laser plasma acceleration (LPA). Because of the still limited electron beam performance (especially energy spread and divergence) in view of the FEL requirements, the electron beam transfer line has been specifically designed with adequate diagnostics and strong focusing variable strength permanent magnet quadrupoles, an energy de-mixing chicane and second set of quadrupoles for further dedicated focusing in the FEL interaction region, in a U20 in-vacuum undulator, enabling to operate at 200 nm with a 180 MeV electron beam. The first observation and transport of electrons in the COXINEL line is presented here.
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MOPOW006	Planning and Controlling of the Cold Accelerator Sections Installation in XFEL	716
	M. Bousonville, S. Choroba, F. Eints DESY, Hamburg, Germany
	The installation of the main linear accelerator in the 2 km European XFEL (X-Ray Free-Electron Laser) tunnel is currently under way. The accelerator consists of nine so-called cryo-strings. A typical cryo-string comprises 12 accelerator modules, which will be fed by three RF stations. Furthermore, the installation of electronic racks, cables, power and water supply etc. takes place. To enable a most effective installation of the accelerator components, planning and controlling methods, which had first been developed for the RF system work package, were adapted for the entire main linear accelerator. As a first step, a process plan was developed in cooperation with the work package leaders. On the basis of this plan, the installation process is promoted by several measures: The status of the installation is precisely registered by weekly queries which enable monitoring of the progress and feedback to everyone involved. With this information at hand, the installation process can be controlled and plan deviations can be corrected. Furthermore, the experience gained at one cryo-string is used to optimise the plan for the next cryo-string installation.
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MOPOW007	Parts Tracking for Fabrication, Installation and Maintenance at the European XFEL	719
	L. Hagge, J.A. Dammann, A. Frank, J. Kreutzkamp, D. Käfer, B. List, S. Rohwedder DESY, Hamburg, Germany
	DESY has established a powerful configuration management solution for the construction of the European XFEL. It tracks the status and location of accelerator components during fabrication and installation, and it contains workflows for reviews, change control and the handling of non-conformities. It provides extensive progress monitoring and reporting for the production and installation of accelerator components. This way, it collects on-the-fly a comprehensive documentation of the accelerator, which serves as a thorough foundation for asset and maintenance management during the upcoming operation. The poster gives an overview of the application and summarizes its status, benefits and experience.
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MOPOW008	Reverse Undulator Tapering for Polarization Control at XFELs	722
	E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	Baseline design of a typical X-ray FEL undulator assumes a planar configuration which results in a linear polarization of the FEL radiation. However, many experiments at X-ray FEL user facilities would profit from using a circularly polarized radiation. As a cheap upgrade one can consider an installation of a short helical afterburner, but then one should have an efficient method to suppress powerful linearly polarized background from the main undulator. We describe a method for such a suppression: an application of the reverse taper in the main undulator*. In a certain range of the taper strength, the density modulation (bunching) at saturation is practically the same as in the case of non-tapered undulator while the power of linearly polarized radiation is suppressed by orders of magnitude. Then strongly modulated electron beam radiates at full power in the afterburner. The scheme was successfully tested at LCLS** and is routinely used in user experiments. In this contribution we present the theoretical description of the method as well as the results of experiments with reverse taper at FLASH2. * E.A. Schneidmiller and M.V. Yurkov, Phys. Rev. ST-AB 16, 110702 (2013) ** H.-D. Nuhn et al., "Commissioning of the DELTA polarizing undulator at LCLS", Proc. of FEL2015 Conf., Daejeon, Korea
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MOPOW009	Studies of Harmonic Lasing Self-seeded FEL at FLASH2	725
	E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	A concept of the Harmonic Lasing Self-Seeded (HLSS) FEL was proposed in*,**. A gap-tunable undulator is divided into two parts such that the first part is tuned to a sub-harmonic of the second part. Harmonic lasing occurs in the exponential gain regime in the first part of the undulator, also the fundamental stays well below saturation. In the second part of the undulator the fundamental mode is resonant to the wavelength, previously amplified as the harmonic. The amplification process proceeds in the fundamental mode up to saturation. In this case the bandwidth is reduced by a significant factor depending on harmonic number but the saturation power is still as high as in the reference case of lasing at the fundamental in the whole undulator, i.e. the spectral brightness increases. Application of the post-saturation tapering would allow to generate higher peak power than in SASE mode due to an improved longitudinal coherence. We present feasibility study of the application of the HLSS FEL scheme at FLASH2 and show that it allows to achieve a higher power and a smaller bandwidth than in a standard SASE regime. First experimental tests are eventually discussed. * E.A. Schneidmiller and M.V. Yurkov, Phys. Rev. ST-AB 15 (2012) 080702 ** E.A. Schneidmiller and M.V. Yurkov, "Harmonic Lasing Self-Seeded FEL", Proc. of FEL2013 Conf., New York, USA
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MOPOW010	The Superconducting Soft X-ray Free-Electron Laser User Facility FLASH	729
	M. Vogt, J. Feldhaus, K. Honkavaara, J. Rönsch-Schulenburg, S. Schreiber, R. Treusch DESY, Hamburg, Germany
	FLASH, the superconducting free-electron laser at DESY delivers up to several thousand photon pulses per second with wavelengths ranging from 52 nm down to as low as 4.2 nm and with pulse energies of up to 500 uJ to photon users at the FLASH1 beamline. In 2014 and 2015 a second beamline, FLASH2, has been commissioned in parallel to user operation at FLASH1. FLASH produces bunch trains of up to 800 bunches in 0.8 ms with a train repetition rate of 10 Hz. Each train can be split in sub-trains for FLASH1 and FLASH2, such that both beamlines receive bursts of bunches with full 10 Hz. Operational highlights are the latest SASE energy record of 600 uJ at 15 nm in FLASH2, and the first simultaneous SASE lasing of three undulator systems: FLASH1 (13.7 nm), sFLASH (38 nm), and FLASH2 (20 nm). sFLASH is the seeding experiment in the FLASH1 beamline. Moreover we will report on recent technical and operational improvements. A major success is the improved reliability and stability of the whole facility with shorter SASE tuning times.
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MOPOW011	Operation of Free Electron Laser FLASH Driven by Short Electron Pulses	732
	V. Balandin, G. Brenner, C. Gerth, N. Golubeva, U. Mavrič, H. Schlarb, E. Schneidmiller, S. Schreiber, B. Steffen, M. Yan, M.V. Yurkov DESY, Hamburg, Germany E. Hass, A. Kuhl, T. Plath, M. Rehders, J. Rönsch-Schulenburg, J. Roßbach University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	The program of low charge mode of operation is under development at free electron laser FLASH aiming in single mode radiation pulses. A short pulse photoinjector laser has been installed at FLASH allowing production of ultrashort electron pluses with moderate compression factor of the beam formation system. Here we present pilot results of free electron laser FLASH operating at the wavelength of 13.1 nm and driven by 70 pC electron bunches. Relevant theoretical analysis has been performed showing good agreement with experimental results.
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MOPOW012	Transverse Coherence and Fundamental Limitation on the Pointing Stability of X-ray FELs	735
	E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	The radiation from SASE FEL has always limited value of the degree of transverse coherence*. When transverse size of the electron beam significantly exceeds diffraction limit, the mode competition effect does not provide the selection of the ground mode, and spatial coherence degrades due to contribution of the higher azimuthal modes. An important consequence of this effect are fluctuations of the spot size and pointing stability of the photon beam**. These fluctuations are fundamental and originate from the shot noise in the electron beam. The effect of pointing instability becomes more pronouncing for shorter wavelengths. We analyze in detail the case of optimized SASE FEL* and derive universal dependencies applicable to all operating and planned x-ray FELs. We show that the hard x-ray FELs driven by low energy beams may exhibit poor spatial coherence and bad pointing stability. * E.L. Saldin, E.A. Schneidmiller and M.V. Yurkov, Opt. Commun. 281(2008)1179. ** E.A. Schneidmiller and M.V. Yurkov, Proc. FEL2015 Conference, Daejeon, Korea, 2015, TUP021.
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MOPOW013	Application of Statistical Methods for Measurements of the Coherence Properties of the Radiation from SASE FEL	738
	E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	Radiation of the SASE FEL operating in the linear regime possesses the properties of completely chaotic polarized light which happens due to start up of the amplification properties from the shot noise in the electron beam*. One of the features of this statistical object is that probability distribution of the radiation pulse energy follows gamma distribution. Parameter of this distribution is the number of modes in the radiation pulse which is equal to inverse deviation of the energy fluctuations. Statistical analysis of the radiation energies measured within different spatial apertures allows us to determine the number of longitudinal and transverse modes. In addition, knowledge of the saturation length allows to determine the duration of the lasing part of the electron bunch, photon pulse duration, and coherence time**. Knowledge of the number of transverse modes allows one to determine the degree of transverse coherence. In this report we present theoretical background of the proposed method and experimental results obtained at free electron laser FLASH. * E.L. Saldin, E.A. Schneidmiller and M.V. Yurkov, Opt. Commun. 148 (1998) 383. ** C. Behrens et al., Phys. Rev. ST Accel. Beams 15 (2012) 030707.
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MOPOW015	Fermi Upgrade Plans	744
	A. Fabris, E. Allaria, L. Badano, F. Bencivenga, C. Callegari, F. Capotondi, D. Castronovo, F. Cilento, P. Cinquegrana, M. Coreno, R. Cucini, I. Cudin, G. D'Auria, M.B. Danailov, R. De Monte, G. De Ninno, P. Delgiusto, A.A. Demidovich, S. Di Mitri, B. Diviacco, R. Fabris, W.M. Fawley, M. Ferianis, E. Ferrari, P. Finetti, P. Furlan Radivo, G. Gaio, D. Gauthier, F. Gelmetti, L. Giannessi, F. Iazzourene, M. Kiskinova, S. Krecic, M. Lonza, N. Mahne, M. Malvestuto, C. Masciovecchio, M. Milloch, F. Parmigiani, G. Penco, A. Perucchi, L. Pivetta, O. Plekan, M. Predonzani, E. Principi, L. Raimondi, P. Rebernik Ribič, F. Rossi, E. Roussel, L. Rumiz, C. Scafuri, C. Serpico, P. Sigalotti, M. Svandrlik, C. Svetina, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	FERMI has reached its nominal performance on both FEL lines, FEL-1 (12 eV to 62 eV) and FEL-2 (62 eV to 310 eV). After a brief overview of the activities with users, we will describe plans for LINAC , FEL and beamline upgrades for 2016-2018 and beyond. This includes EEHG schemes for FEL-2.
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MOPOW016	Status of Design and Development of Delhi Light Source at IUAC, Delhi	748
	S. Ghosh, R.K. Bhandari, G.K. Chaudhari, V.J. Joshi, D. Kabiraj, D. Kanjilal, B. Karmakar, J. Karmakar, N. Kumar, P. Patra, B.K. Sahu, A.S. Sharma, A.S. Sthuthikkatt Reghu IUAC, New Delhi, India A. Aryshev, M.K. Fukuda, S. Fukuda, N. Terunuma, J. Urakawa, J. Urakawa KEK, Ibaraki, Japan A. Deshpande SAMEER, Mumbai, India V. Naik, A. Roy VECC, Kolkata, India T. Rao BNL, Upton, Long Island, New York, USA
	Funding: The project is supported jointly by Board of Research in Nuclear Sciences (BRNS) and IUAC The demand for the photon beams for basic research is growing in India. To address the requirements, a project to develop a compact Light Source based on the principle of Free Electron Laser has been initiated at the Inter University Accelerator Centre (IUAC). In the first phase of the project, a normal conducting RF gun will be used to produce electron beam of energy ~ 8 MeV by using copper photocathode and subsequently by Cs2Te photocathode. A high power fiber laser with short pulse length is planned to be used to produce the pre-bunched electron beam by splitting the single laser pulse in to 16 pulses ("comb beam"). The electron beam will be injected in to a compact, variable gap undulator magnet to produce the THz radiation whose frequency can be tuned by varying the undulator field strength and the time separation of the comb beam. In the second and third phases of the project, superconducting RF gun and superconducting accelerating structure will be used to increase the energy of the electron beam up to ~ 40 MeV which will be used to produce IR radiation by using long undulator magnets and to produce X-rays by colliding the electron beam with another high power laser beam.
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MOPOW017	Generation of GeV Photons from X-ray Free Electron Laser Oscillators	751
	R. Hajima JAEA, Ibaraki-ken, Japan M. Fujiwara RCNP, Osaka, Japan
	We propose generation of narrow-bandwidth GeV photons, gamma-rays, via Compton scattering of hard X-ray photons in X-ray free-electron laser oscillators. The gamma-rays have a narrow-bandwidth spectrum with a sharp peak, ~0.1% (FWHM), due to the nature of Compton scattering in relativistic regime. Such gamma-rays will be a unique probe for studying hadron physics. We discuss features of the gamma-ray source, flux, spectrum, polarization, tunability and energy resolution.
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MOPOW018	Feasibility Study of Photocathode Opearation of Thermionic RF Gun at KU-FEL	754
	H. Zen, T. Kii, K. Masuda, K. Morita, T. Murata, T. Nogi, H. Ohgaki, S. Suphakul, K. Torgasin Kyoto University, Kyoto, Japan R. Kuroda AIST, Tsukuba, Ibaraki, Japan
	Kyoto University Free Electron Laser (KU-FEL) is a mid-infrared FEL driven by a compact linac utilizinig a thermionic RF gun as its electron source*. Recently we succeeded in operating KU-FEL with photocathode operation of the RF gun by using the thermionic cathode (LaB6) as a photocathode. The performance of KU-FEL under the thermionic cathode and photocathode operation will be reported. In addition, some recent application experiment results will also be presented in this presentation. *H. Zen, et al., Infrared Phys. Techn. 51 (2008) 382.
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MOPOW019	Commissioning Status of the Extreme-Ultraviolet FEL Facility at SACLA	757
	T. Sakurai, T. Asaka, N. Azumi, T. Hara, T. Hasegawa, T. Inagaki, T. Ishikawa, R. Kinjo, C. Kondo, H. Maesaka, T. Ohshima, Y. Otake, H. Tanaka, T. Tanaka, K. Togawa RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan T. Bizen, N. Hosoda, H. Kimura, S. Matsubara, S. Matsui JASRI/SPring-8, Hyogo, Japan
	To equip SACLA with wide ability to provide a laser beams in EUV and soft X-ray regions to experimental users, we have constructed a new free electron laser facility for SACLA beamline-1. Injector components, such as a thermionic electron gun, two buncher cavities, a S-band standing wave accelerator, S-band travelling wave accelerator and their RF sources, were relocated from the SCSS test accelerator, which was a prototype machine of SACLA. At the downstream of a bunch compressor chicane, three C-band 40 MV/m acceleration units were newly installed to effectively boost a beam energy up to 470 MeV. Two in-vacuum undulators were remodeled by changing the period of magnet array from 15 mm to 18 mm to increase SASE intensity by a larger K-value of 2.1. Beam commissioning was started in autumn 2015. So far SASE radiation at a 33 nm wavelength driven by a 470 MeV electron beam was observed. We will install the third undulator in this winter to obtain SASE saturation and additional C-band accelerator units in the next summer to raise the maximum beam energy to 750 MeV. In this presentation, the overview of the facility and the commissioning status will be reported.
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MOPOW020	Power Improvement of Free-Electron Laser Using Transverse-Gradient Undulator with External Focusing	760
	G. Zhou, Y. Jiao, G. Xu IHEP, Beijing, People's Republic of China J. Wu SLAC, Menlo Park, California, USA T. Zhang SINAP, Shanghai, People's Republic of China
	Funding: Supported by National Natural Science Foundation of China (11475202, 11405187) and Youth Innovation Promotion Association of Chinese Academy of Sciences (No. 2015009) Resent study [Z. Huang et al., Phys. Rev. Lett. 109, 204801 (2012)] shows that the transverse-gradient undu-lator (TGU) together with electron beams with constant dispersion can reduce the sensitivity to energy spread for FEL. In this study, we numerically study FEL using TGU with external focusing. In spite of the dispersion varia-tion, through parameter optimization, FEL using TGU with TGU achieves similar radiation to that without ex-ternal focusing. To achieve a high energy exaction effi-ciency, the initial dispersion should be set with a shift from that corresponding to the resonant condition, and a variation of the transverse gradient in different undulator section is preferred. Other approaches, such as tapering and detuning frequency control, are also discussed to further improve the radiation power and are demonstrated with global parametric optimizations base on simulation.
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MOPOW022	Model-based Algorithm to Tune the LCLS Optics	763
	Z. Zhang TUB, Beijing, People's Republic of China Y. Ding, X. Huang SLAC, Menlo Park, California, USA
	Transverse phase space matching of electron beam to the undulator optics is important for achieving good performance in free-electron lasers. Usually there are dedicated matching quadrupoles distributed in the beamline, by measuring the beam phase space the matching quadrupoles are calculated and adjusted to match to the designed Twiss parameters. Further adjustment of the quadrupoles to overcome collective effects or realistic beamline errors is typically required for performance improvement. In this paper, we studied a method to decompose the Twiss parameters for an independent control of the phase space. Mathematical analysis and numerical simulations are both presented to show that through combining the quadrupoles into some multi-knobs, we can control the Twiss parameters independently. We also show some experimental results at the LCLS.
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MOPOW023	Proposal of an X-band Linearizer for Dalian Coherent Light Source	766
	G.L. Wang, X.M. Yang, W.Q. Zhang DICP, Dalian, People's Republic of China H.X. Deng, C. Feng SINAP, Shanghai, People's Republic of China
	Dalian coherent Light Source (DCLS) is a FEL user facility working at 50-150 nm, now under commissioning in Dalian, China. The facility based on HGHG mode, requires high brightness electron beam with small energy spread and low emittance. To linearise the longitudinal phase space before the bunch compression, an X-band linearizer is considered before the bunch compressor. In this paper, we study the performance improvement of DCLS FEL radiation by using such a harmonic cavity, including the jitter of central wavelength induced by arriving time and a larger bunch compression ratio for femtosecond FEL application.
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MOPOW024	Harmonic Lasing Options for Dalian Coherent Light Source	770
	G.L. Wang, X.M. Yang, W.Q. Zhang DICP, Dalian, People's Republic of China H.X. Deng, C. Feng SINAP, Shanghai, People's Republic of China
	Harmonic lasing of the Free Electron Laser can be achieved by disrupting the electron interaction with the usually dominant fundamental while allowing the increasing of a harmonic interaction. It's a cheap and relatively efficient way to extend the photon energy range of a particular FEL. In this paper, we discussed the possibility of harmonic lasing concept at Dalian Coherent Light Source by using the combination of tapered undulators and phase shifters. Our calculation shows that it's feasible with the present layout to provide intense, stable, and narrow-band harmonic radiation, the FEL wavelength could be down to 20 nm and the corresponding pulse energy is about 10 μJ.
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MOPOW026	Status of FELiCHEM, a New IR-FEL in China	774
	H.T. Li, Z.G. He, Q.K. Jia, Q. Luo, L. Wang, S.C. Zhang USTC/NSRL, Hefei, Anhui, People's Republic of China
	FELiChEM is a new experimental facility under construction at University of Science and Technology of China (USTC), whose core device is a FEL oscillator generating middle-infrared and far-infrared laser and covering the spectral range of 2.5-200 μm. It will be a dedicated light source aiming at energy chemistry research, with the photo excitation, photo dissociation and photo detection experimental stations. We present the brief physical and technical design that delivers the required performance for this device and summarize the status of fabrication. Final assembly is scheduled for early in the next year with first light targeted for July 2017.
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MOPOW027	Generation of Coherent Mode-locked Radiation in a Seeded Free Electron Laser	777
	Z. Wang, Z.T. Zhao SINAP, Shanghai, People's Republic of China D. Xiang Shanghai Jiao Tong University, Shanghai, People's Republic of China
	We present the promise of generating mode-locked multichromatic radiations in a seeded free electron laser based on high gain harmonic generation (HGHG). 3D start-to-end simulations have been carried out and analysis & comparisons have been made to have a research on the properties of each system. In these schemes, either the electron beam density or the seed laser intensity is modulated to produce a coherent radiation pulse train that yields multiple spectral lines in FEL output. Stable peak power at gigawatt level can be generated in the undulator finally.
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MOPOW028	Research on Pulse Energy Fluctuation of a Cascaded High Gain Harmonic Generation Free Electron Laser	781
	Z. Wang, C. Feng, Q. Gu, Z.T. Zhao SINAP, Shanghai, People's Republic of China
	Shot to shot pulse energy fluctuation is one of the most critical issues for two-stage cascaded high gain harmonic generation (HGHG) free electron lasers (FELs). In this paper, we study the effects of various electron parameters jitters on the output pulse energy fluctuations based on Shanghai Soft X-ray free electron laser facility (SXFEL). The results show that the relative timing jitter between the electron beam and the seed laser is proved to be the most sensitive factor. The energy jitter and charge jitter make some contributions and are non-ignorable as well. Some comparisons between our facility and FERMI have been made and we hope the conclusions draw from this study would be a reference for the optimization of future seeded FEL facilities based on cascading stages of HGHG.
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MOPOW029	The Soft X-ray Self-seeding System Design for SXFEL User Facility	785
SUPSS013	use link to see paper's listing under its alternate paper code
	K.Q. Zhang, T. Liu, D. Wang SINAP, Shanghai, People's Republic of China Y. Feng SLAC, Menlo Park, California, USA
	X-ray free electron laser driven by SASE probes the evolution of the new generation light source in high brightness, transverse coherence. However, since SASE achieves lasing from random shotnoise, Poor longitudinal coherence and relative wide bandwidth of SASE FEL limit the operation of many type experiments. Self-seeding as a promising scheme produces longitudinal coherence and even narrower bandwidth radiation by a monochromatic seeding instead of external seeding. The self-seeding system design based on the grating monochromator is carried out for SXFEL user facility across the photon energy from 800-1200 eV. The grating monochromator with a resolution power of 〖10〗-4 can provide a monochromatic seeding pulse to the seeding undulator. The layout design and simulations of the scheme are presented. It is showing that the self-seeding system for SXFEL user facility is able to improve SASE FEL longitudinal coherence significantly.
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MOPOW035	A Compact, Wavelength Tunable MW-THz FEL Amplifier	789
	C.H. Chen, A.P. Lee NSRRC, Hsinchu, Taiwan F.H. Chao, Y.C. Chiu, Y.-C. Huang, M.H. Wu NTHU, Hsinchu, Taiwan G. Zhao PKU, Beijing, People's Republic of China
	We propose a compact scheme of THz free electron laser (FEL) amplifier within a 3.5 m long beam line. The amplification of a tunable THz seed laser in an FEL amplifier is driven by an rf photoinjector*. The THz seed laser is an optical parametric amplifier** pumped by a 1064-nm microchip laser and an external-cavity tunable diode laser. By varying the beam energy and undulator parameter, the radiation frequency of the THz FEL amplifier can be tunable in a broad spectral range between 1.5 and 3.0 THz. Moreover, to extract more radiation power from the electron beam within a short undulator, we employ a linearly tapered undulator in our design. The influence of the seed power on the electron-laser interaction in the undulator is studied in some detail for the FEL amplification. Our simulation results show that the radiation power of the THz FEL amplifier can achieve few MW with a 10-W seed power. * D.T. Palmer et al., in Proceedings of Particle Acceleration Conference, Vancouver, 1997, p. 2687, (1997). ** S. Hayashi et al., SCIENTIFIC REPORTS, 4, 5045-1-6, (2014).
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MOPOW036	Design Optimization of an X-band based FEL	793
	A.A. Aksoy Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey A. Latina, J. Pfingstner, D. Schulte CERN, Geneva, Switzerland Z. Nergiz Nigde University, Nigde, Turkey
	A design effort for a new generation of compact, cost-effective, power-efficient FEL facilities, based on X-band technology, has been launched. High-frequency X-band acceleration implies strong wakefields, tight alignment and mechanical tolerances, and challenging stability issues. In this paper a design is proposed for the injector and the linacs, including the two bunch compressors. RF gun and injector simulations have been performed, successfully meeting the stringent requirements in terms of minimum projected emittance, sliced emittance and minimum bunch length. In the design of the linac and bunch compressors wakefield effects and misalignment have been taken into account. Start-to-end tracking simulations through the optimized lattice are presented and discussed.
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MOPOW037	Developments in the CLARA FEL Test Facility Accelerator Design and Simulations	797
	P.H. Williams, D. Angal-Kalinin, A.D. Brynes, J.A. Clarke, F. Jackson, J.K. Jones, J.W. McKenzie, B.L. Militsyn, N. Thompson STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom R.B. Appleby UMAN, Manchester, United Kingdom B. Kyle University of Manchester, Manchester, United Kingdom
	We present recent developments in the accelerator design of CLARA (Compact Linear Accelerator for Research and Applications), the proposed UK FEL test facility at Daresbury Laboratory. In order to prioritise FEL schemes requiring the shortest electron bunches, the layout has changed significantly to enable compression at higher energy. Four proposed modes of operation are defined and tracked from cathode to FEL using ASTRA. Supplementing these baseline mode definitions with CSR-enabled codes (such as CSRTRACK) where appropriate is in progress. The FEL layout is re-optimised to include shorter undulators with delay chicanes between each radiator.
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MOPOW039	An Oscillator Configuration for Full Realization of Hard X-ray Free Electron Laser	801
	K.-J. Kim, T. Kolodziej, R.R. Lindberg, D. Shu, Yu. Shvyd'ko, S. Stoupin ANL, Argonne, Ilinois, USA V.D. Blank, S. Terentiev TISNCM, Troitsk, Russia Y. Ding, W.M. Fawley, J.B. Hastings, Z. Huang, J. Krzywinski, G. Marcus, T.J. Maxwell SLAC, Menlo Park, California, USA N.A. Medvedev CFEL, Hamburg, Germany W. Qin PKU, Beijing, People's Republic of China J. Zemella DESY, Hamburg, Germany
	Funding: Work at ANL supported under US Department of Energy contract DE-AC02-76SF00515 and at SLAC by the U.S. Department of Energy, Office of Science, under Contract No. DE-ACO2-O6CH11357 An X-ray free electron laser can be built in an oscillator (XFELO) configuration by employing an X-ray cavity with Bragg mirrors such as diamond*. An XFELO at the 5th harmonic frequency may be implemented at the LCLS II using its 4 GeV superconducting linac. The XFELO will provide stable, coherent, high-spectral-purity hard x-rays. In addition, portions of its output may be enhanced by the LCLS amplifier for stable pulses of ultrashort duration determined by the electron bunch length. Much progress has been made recently on the feasibility of an XFELO: Analytical and numerical methods have been developed to compute the performance of a harmonic XFELO. The energy spread requirement over a sufficient length of the bunch can be met by temporal shaping of the photo-cathode drive laser**. Experiments at the APS have shown that Be-compound refractive lenses are suitable for a low-loss focusing and that the synthetic diamond crystals can withstand the intense x-ray exposure, in accord with estimates based on molecular dynamics considerations***. A strain-free mounting of thin diamond crystal (< 100 microns) can be realized by shaping a thick diamond into a blind alley****. * R. R. Lindberg et al., PRSTAB 1010701 (2011) ** W. Qin et al., this conference *** N. Medvedev et al., Phys. Rev. B 88, 224304 (2013) **** S. Terentyev, private communication
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MOPOW040	High Efficiency, High Brightness X-ray Free Electron Lasers via Fresh Bunch Self-Seeding	805
	C. Emma, C. Pellegrini UCLA, Los Angeles, USA M.W. Guetg, A.A. Lutman, A. Marinelli, C. Pellegrini, J. Wu SLAC, Menlo Park, California, USA
	High efficiency, terawatt peak power X-ray Free Electron Lasers are a promising tool for enabling single molecule imaging and nonlinear science using X-rays. Increasing the efficiency of XFELs while achieving good longitudinal coherence can be achieved via self-seeding and undulator tapering. The efficiency of self-seeded XFELs is limited by two factors: the ratio of seed power to beam energy spread and the ratio of seed power to shot noise power. We present a method to overcome these limitations by producing a strong X-ray seed and amplifying it with a small energy spread beam. This is achieved by selectively suppressing lasing for part of the bunch in the SASE section. In this manner we can saturate with the seeding electrons and amplify the strong seed with 'fresh' electrons downstream of the monochromator. Simulations of this scenario are presented for two systems, an optimal superconducting undulator design and the LCLS. In the case of the LCLS we examine how betatron oscillations leading to selective suppression are induced by using the transverse wakefield of a parallel plate dechirper. We also discuss extending the selective suppression scheme to chirped electron bunches.
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MOPOW044	Commissioning of the RadiaBeam / SLAC Dechirper	809
	M.W. Guetg, K.L.F. Bane, A. Brachmann, A.S. Fisher, Z. Huang, R.H. Iverson, P. Krejcik, A.A. Lutman, T.J. Maxwell, A. Novokhatski, G. Stupakov, J. Zemella, Z. Zhang SLAC, Menlo Park, California, USA M.A. Harrison, M. Ruelas RadiaBeam Systems, Santa Monica, California, USA J. Zemella DESY, Hamburg, Germany Z. Zhang TUB, Beijing, People's Republic of China
	We present results on the commissioning of the two-module RadiaBeam / SLAC dechirper system at LCLS. This is the first installation and measurement of a corrugated dechirper at high energy (4.4 - 13.3 GeV), short pulses (< 200 fs) and while observing its effect on an operational FEL. Both the transverse and longitudinal wakefields allow more flexible electron beam tailoring. We verify that, for a single module at a given gap, the strength of the longitudinal wake on axis and the dipole near the axis agree well with the theoretical values. Using direct longitudinal phase space mapping and X-ray FEL spectrum measurements we demonstrate the energy chirp control capabilities.
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MOPOW045	Measurement of Advanced Dispersion-based Beam-tilt Correction	813
	M.W. Guetg, F.-J. Decker, Y. Ding, P. Emma, Z. Huang, T.J. Maxwell SLAC, Menlo Park, California, USA
	Funding: DOE contract \#DE-AC02-76SF00515 Free electron lasers in the X-ray regime require a good slice alignment along the electron bunch to achieve their best performance. A transverse beam slice shift reduces this alignment and spoils projected emittance and optics matching. Coherent synchrotron radiation, specifically for over-compression going through full compression, and transverse wakefields are major contributors to this. In the case of the large-bandwidth operation, with a strong energy chirp on the bunch, this misalignments furthermore reduce the spectral bandwidth of the FEL pulse. Well-defined manipulation of dispersion allows to compensate for this slice centroid shifts, therefore enhancing lasing power and in case of the large bandwidth mode, spectral bandwidth. This work shows the first application of this correction on an X-ray FEL resulting in increase in beam-power and bandwidth.
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MOPOW048	Development of the LCLS-II Optics Design	820
	Y. Nosochkov, P. Emma, T.O. Raubenheimer, M. Woodley SLAC, Menlo Park, California, USA
	Funding: Work supported by the Department of Energy Contract DE-AC02-76SF00515. The LCLS-II is a high repetition rate, high average brightness free-electron laser (FEL) under construction at the SLAC National Accelerator Laboratory. The LCLS-II will include new major components: a high repetition-rate injector, a superconducting, CW (continuous wave), 4-GeV linac with a bunch compressor system, a 3-way beam spreader, with independent hard X-ray (HXR) and soft X-ray (SXR) FEL undulators. The design is based on the existing SLAC facilities, including the LCLS linac and beam transport lines. The new SXR line will utilize a variable-gap undulator sharing the same tunnel with the new HXR horizontal-gap vertically polarizing undulator that will replace the existing LCLS undulator. We describe the current state of the electron optics design and the latest developments.
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MOPOW049	Implementation of a Corrugated-Plate Dechirping System for GeV Electron Beam at LCLS	824
	M.A. Harrison, P. Frigola, J.D. McNevin, A.Y. Murokh, M. Ruelas RadiaBeam Systems, Santa Monica, California, USA A.M. Babbitt, M. Carrasco, A. Cedillos, R.H. Iverson, P. Krejcik, T.J. Maxwell, '. Oven SLAC, Menlo Park, California, USA
	Funding: This work is supported by US DOE Grant No. DE-SC0009550. A new corrugated-plate Dechirper was recently installed in the LCLS and underwent commissioning tests to gauge its efficacy in shaping the longitudinal phase space of bunches entering the FEL. Here, we describe in detail the completed four-meter LCLS Dechirper system along with a narrative of its construction. We detail the various challenges and lessons learned in the manufacturing and assembly of this first-of-its-kind device. An outlook on future designs is presented.
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TUZA01	Soft X-ray Free Electron Laser at SINAP	1028
	D. Wang SINAP, Shanghai, People's Republic of China
	Shanghai X-ray FEL (SXFEL) is a test facility at Shanghai Institute of Applied Physics, Chinese Academy of Sciences originally designed for studying XFEL principle and technologies. It is composed of a warm linac to provide up to 840 MeV electron beam, an undulator line with cascaded EEHG-HGHG setup and a short diagnostic beamline. The project started the construction by the end of 2014. Recently a proposal to upgrade it to an user facility at the soft x-ray regime got approved. The talk will give an overview of the test facility construction and upgrade plan.
	Slides TUZA01 [9.344 MB]
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TUZA02	Twin-bunch Two-colour FEL at LCLS	1032
	A. Marinelli, R.N. Coffee, F.-J. Decker, Y. Ding, R.C. Field, S. Gilevich, Z. Huang, D. Kharakh, H. Loos, A.A. Lutman, T.J. Maxwell, J.L. Turner, S. Vetter SLAC, Menlo Park, California, USA
	Twin electron bunches have been the subject of much investigation at the Linac Coherent Light Source, due to their many applications to X-ray free-electron lasers (X-FEL). Twin bunches are trains of two electron bunches that are accelerated and compressed within the same accelerating RF period. At LCLS, these bunches are used in the downstream FEL undulator to generate two X-ray pulses of different energies for pump/probe applications or de novo phase determination of protein crystals. The spectral and temporal shaping of the two bunches requires exquisite control of the compression system to vary the main parameters of the system in a controlled way (peak current, temporal delay and energy separation). I will discuss recent experimental and theoretical results on this subject. In particular I will focus on the demonstration of mJ-level two-color X-ray pulses using twin bunches, as well as the temporal and spectral control of this new mode of operation. Finally, I will discuss our experience with user experiments as well as our future directions of investigation.
	Slides TUZA02 [5.738 MB]
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TUOCA03	Commissioning of the European XFEL Injector	1044
	F. Brinker DESY, Hamburg, Germany
	The European XFEL Injector consists of an L-Band RF photoinjector, a TESLA type 1.3 GHz module, a 3rd harmonic RF section, a laser heater and an extensive diagnostic section to determine projected and slice properties of the beam. The commissioning of the complete system has been started in December 2015 after several years of construction. We will report on commissioning results and persepctives for the later XFEL operation.
	Slides TUOCA03 [5.182 MB]
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TUPOR018	Design Optimization of Compensation Chicanes in the LCLS-II Transport Lines	1695
	J. Qiang, C.E. Mitchell, M. Venturini LBNL, Berkeley, California, USA Y. Ding, P. Emma, Z. Huang, G. Marcus, Y. Nosochkov, T.O. Raubenheimer, L. Wang, M. Woodley SLAC, Menlo Park, California, USA
	LCLS-II is a 4th-generation high-repetition rate Free Electron Laser (FEL) based x-ray light source to be built at the SLAC National Accelerator Laboratory. To mitigate the microbunching instability, the transport lines from the exit of the Linac to the undulators will include a number of weak compensation chicanes with the purpose of cancelling the momentum compaction generated by the main bend magnets of the transport lines. In this paper, we will report on our design optimization study of these compensation chicanes in the presence of both longitudinal and transverse space-charge effects.
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TUPOR019	RF Injector Beam Dynamics Optimization and Injected Beam Energy Constraints for LCLS-II	1699
	C.E. Mitchell, H.J. Qian, J. Qiang, F. Sannibale, M. Venturini LBNL, Berkeley, California, USA P. Emma, T.O. Raubenheimer, J.F. Schmerge, F. Zhou SLAC, Menlo Park, California, USA
	Funding: Work supported by the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231. LCLS-II is a proposed high-repetition rate (>1 MHz) Free Electron Laser (FEL) X-ray light source, based on a CW, superconducting linac, to be built at SLAC National Accelerator Laboratory. The injector technology is based on a high-repetition rate RF photoinjector gun developed as part of the Advanced Photoinjector Experiment (APEX) at Lawrence Berkeley National Laboratory. Exploration of the injector design settings is performed using a multiobjective genetic optimizer to optimize the beam quality at the injector exit (~100 MeV). In this paper, we describe the current status of LCLS-II injector design optimization, with a focus on the sensitivity of the optimized solutions to the beam energy at the injector exit, which is constrained by the requirements of the downstream laser heater system.
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