IPAC2014 - Classification: 02 Synchrotron Light Sources and FELs / A06 Free Electron Lasers

Paper	Title	Page
MOYAA01	Innovative Ideas for Single-pass FELs	12
	T. Hara RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	SASE FELs are a powerful light source in short wavelengths from VUV to X-ray regions to investigate matters and phenomena. SASE was first experimentally obtained in 2000 at DESY TTF with an output wavelength of 10⁹ nm. Subsequently, FLASH, LCLS and SACLA have achieved lasing in VUV, soft X-rays and hard X-rays. Although SASE has already been widely used for many application experiments in broad scientific fields, its spiky spectrum and time structures due to the lack of longitudinal coherence sometimes become problematic. To improve its longitudinal coherence, various ideas have been proposed and some of them are already demonstrated experimentally, such as a self-seeded scheme, high-gain harmonic generation (HGHG) and echo-enabled harmonic generation (EEHG). There is also another direction of developments to enhance the capability and potentiality of SASE, for example short pulse generation and two-color lasing. This talk will review recent innovative ideas of short wavelength FELs together with their experimental results.
	Slides MOYAA01 [10.701 MB]
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TUZA02	THz Facility at ELBE: A Versatile Test Facility for Electron Bunch Diagnostics on Quasi-CW Electron Beams	933
	M. Gensch, B.W. Green, J. Hauser, S. Kovalev, M. Kuntzsch, U. Lehnert, P. Michel, R. Schurig HZDR, Dresden, Germany A. Al-Shemmary, V. B. Asgekar, T. Golz, H. Schlarb, N. Stojanovic, S. Vilcins DESY, Hamburg, Germany A.S. Fisher SLAC, Menlo Park, California, USA G. Geloni XFEL. EU, Hamburg, Germany A.-S. Müller, M. Schwarz KIT, Karlsruhe, Germany N.E. Neumann, D. Plettemeier TU Dresden, Dresden, Germany
	At the Helmholtz-Zentrum Dresden-Rossendorf near Dresden a quasi-cw low-energy electron linear accelerator based on superconducting radiofrequency technology is operated successfully for more than 10 years. The ELBE accelerator is driving several secondary radiation sources including 2 infrared free electron lasers. A new addition will be a THz facility that aims to make use of super-radiant THz radiation. In its final form the THz facility shall consist of one coherent diffraction radiator and one undulator source which provide high-field THz pulses at unprecedented repetition rates. While the medium term goal is to establish a unique user facility for nonlinear THz science, the THz sources are already used as a test facility for novel diagnostic techniques on quasi-cw electron beams. The progress of the developments is reported and an outlook into future challenges and opportunities is given.
	Slides TUZA02 [3.041 MB]
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TUOCA01	The Linac Coherent Light Source-II Project	935
	J.N. Galayda SLAC, Menlo Park, California, USA
	Funding: Work supported by US DOE Contract DE-AC02-766SF00515 The “Linac Coherent Light Source–II” Project, initiated in September 2010, has gone through a radical transformation beginning in August 2013. In its new form, LCLS-II will construct a 4 GeV CW superconducting linac in the first kilometre of the existing linac tunnel. A new undulator, optimized as a soft x-ray (200-1,300 eV) source, will receive electrons from the new SC linac. The existing undulator system will be replaced with a new variable gap device, which will receive electrons from either the new SC linac (providing 1-5 keV photons) or the copper linac presently used by LCLS (providing 1-25 keV x-rays). First light from the new facility is expected in September 2019. galayda@slac.stanford.edu
	Slides TUOCA01 [9.380 MB]
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TUOCA02	Status of the Free Electron Laser User Facility FLASH	938
	M. Vogt, B. Faatz, J. Feldhaus, K. Honkavaara, S. Schreiber, R. Treusch DESY, Hamburg, Germany
	FLASH, the Free Electron Laser User Facility at DESY (Hamburg, Germany), delivers high brilliance XUV and soft X-ray FEL radiation to photon experiments. After a shutdown to connect the second undulator beamline FLASH2 to the FLASH linac, re-commissioning of FLASH started in autumn 2013. The year 2014 is dedicated to FLASH1 user experiments. The commissioning of the FLASH2 beamline takes place in 2014 in parallel to FLASH1 operation.
	Slides TUOCA02 [9.156 MB]
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THPRO003	Progress of the LUNEX5 demonstator Project	2856
	M.-E. Couprie, C. Benabderrahmane, P. Berteaud, C. Bourassin-Bouchet, F. Bouvet, L. Cassinari, L. Chapuis, J. Daillant, M. Diop, M.E. El Ajjouri, C. Evain, C. Herbeaux, N. Hubert, M. Labat, P. Lebasque, A. Lestrade, A. Loulergue, P. Marchand, O. Marcouillé, J.L. Marlats, C. Miron, P. Morin, A. Nadji, F. Polack, F. Ribeiro, J.P. Ricaud, P. Roy, K. Tavakoli, M. Valléau, D. Zerbib SOLEIL, Gif-sur-Yvette, France S. Bielawski, E. Roussel, C. Szwaj PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France B. Carré, D. Garzella CEA/DSM/DRECAM/SPAM, Gif-sur-Yvette, France X. Davoine CEA/DAM/DIF, Arpajon, France N. Delerue LAL, Orsay, France G. Devanz CEA/DSM/IRFU, France A. Dubois, J. Lüning CCPMR, Paris, France G. Lambert, R. Lehé, V. Malka, A. Rousse, C. Thaury LOA, Palaiseau, France C. Madec, A. Mosnier CEA/IRFU, Gif-sur-Yvette, France
	LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation) aims at investigating the production of short, intense, coherent pulses in the 40-4 nm spectral range [1]. It comprises two types of accelerators connected to a single Free Electron Laser (FEL) for advanced seeding configurations (seeding with High order Harmonic in Gas, echo). A 400 MeV superconducting Linear Accelerator, adapted for studies of advanced FEL schemes, will enable future upgrade towards high repetition rate and multi-user operation by splitting part of the macropulse to different FEL lines. A 0.4 - 1 GeV Laser Wake Field Accelerator (LWFA) [2] will also be qualified by the FEL application. After the Conceptual Design Report, R&D has been launched on different sub components. Following transport theoretical studies of longitudinal and transverse manipulation of a LWFA electron beam enabling to provide theoretical amplification, a test experiment is under preparation.
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THPRO004	Study of the CLIO FEL in the Far-infrared in a Partially Guided Mode	2859
	J.-M. Ortega, J.P. Berthet, F. Glotin, R. Prazeres LCP/CLIO, Orsay, Cedex, France
	The infrared free-electron laser offers a large tunability since the FEL gain remains high throughout the infrared spectral range, and the reflectivity of metal mirrors remains also close to unity. The main limitation comes from the diffraction of the optical beam due to the finite size of the vacuum chamber of the undulator. A solution is to use this chamber as a waveguide by adaptating the radius of curvature of the cavity mirrors to this regime. Then, as has been shown before* a minimum appears in the spectrum that can be produced by the FEL. We discuss the physical mechanism of this particular regime and compare it to experiments using vacuum chambers of different tranverse sizes. A good agreement is found with results of simulations and with a simple analytical formula. * Analysis of the periodic power gaps observed in the tuning range of FELs with a partial waveguide, R. Prazeres, F. Glotin, J.-M. Ortega, Phys. Rev. STAB12, 010701 (2009)
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THPRO006	Configuration Management in the Series Production of the XFEL Accelerator Modules	2863
	L. Hagge, S. Barbanotti, S. Eucker, A. Frank, K. Jensch, J. Kreutzkamp, D. Käfer, A. Matheisen DESY, Hamburg, Germany S. Berry, O. Napoly CEA/DSM/IRFU, France C. Cloué, C. Madec, T. Trublet CEA/IRFU, Gif-sur-Yvette, France
	The series production of the superconducting accelerator modules for the European XFEL requires a production rate of one module per week. For this, assembly procedures have to be well-defined and repeatable, and the punctual supply of parts from the contributing institutes has to be assured. Configuration management (CM) has been introduced for clarification of responsibilities and establishing procedures. CM provides unique identification of parts, part status and location tracking, versioning of documentation, and procedures for change control, auditing and handling non-conformities. The configuration database, which is based on DESY’s Engineering Data Management System, contains the entire information which is necessary for assembling the accelerator modules. The content ranges from work instructions how to build a cryomodule up to individual records of all produced parts. Workflow and reports help tracking production progress and establishing production quality. The presentation gives an overview of the CM solution which is in place for the assembly of the XFEL accelerator modules, and reports experience and lessons learned from series production of the first modules.
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THPRO007	Beam-based Alignment in the European XFEL SASE1	2867
	H. Jin, W. Decking, T. Limberg DESY, Hamburg, Germany
	The European X-ray Free Electron Laser (E-XFEL) provides an ultra-short and high-brilliant photon pulses of spatially coherent X-rays with wavelengths down to 0.05 nm by using three undulator systems. Within these undulator systems, the orbit trajectory is required to be straight to a few micron over each gain length, so that the photon beam is capable of overlapping efficiently with the electron beam. However, this requirement is not obtainable with ordinary mechanical alignment methods. For this reason, a beam-based alignment (BBA) method using BPM readings of different beam energies is applied to the E-XFEL SASE1 undulators. In this report, we describe the BBA simulation for SASE1 including alignment errors of quadrupoles and BPMs. After correction, the desired range of the orbit trajectory is attained with high confidence. In addition, to identify the reliability of an aligned orbit trajectory acquired from the BBA simulation, we present here the SASE FEL radiation simulation, in which we observe a slight decrease of radiation energy and power.
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THPRO008	Obtaining High Degree of Circular Polarization at X-ray FELs via a Reverse Undulator Taper	2870
	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 (or cross-planar) afterburner, but then one should have an efficient method to suppress powerful linearly polarized background from the main undulator. In this paper we propose a new method for such a suppression: an application of the reverse taper in the main undulator. We discover that 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. Considering SASE3 undulator of the European XFEL as a practical example, we demonstrate that soft X-ray radiation pulses with peak power in excess of 100 GW and an ultimately high degree of circular polarization can be produced. Phys. Rev. ST-AB 16(2013)110702
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THPRO009	Harmonic Lasing in X-ray FELs	2873
	E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	Contrary to nonlinear harmonic generation, harmonic lasing in a high-gain FEL can provide much more intense, stable, and narrow-band FEL beam which is easier to handle if the fundamental is suppressed. We perform a parametrization of the solution of eigenvalue equation for lasing at odd harmonics, and present explicit expression for FEL gain length, taking into account all essential effects. We propose and discuss methods for suppression of the fundamental. We also suggest a combined use of harmonic lasing and lasing at the retuned fundamental wavelength in order to reduce bandwidth and to increase brilliance of X-ray beam. We discover that in a part of the parameter space, corresponding to the operating range of soft X-ray beamlines of X-ray FEL facilities, harmonics can grow faster than the fundamental. We suggest that harmonic lasing can be widely used in the existing or planned X-ray FEL facilities. LCLS after a minor modification can lase at the 3rd harmonic up to the photon energy of 25-30 keV providing multi-gigawatt power level. At the European XFEL the harmonic lasing would allow to extend operating range up to 100 keV, to reduce bandwidth and increase brilliance.
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THPRO010	Analysis of Operation of Harmonic Lasing Self-seeded FEL	2876
	E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	Harmonic lasing self-seeded FEL holds great potential for significant improvement of the the longitudinal coherence of the radiation. A gap-tunable undulator is divided into two parts by setting two different undulator parameters 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 defined by the harmonic lasing (i.e. it 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 undulator tapering in the deep nonlinear regime would allow to generate higher peak powers approaching TW level. The scheme is illustrated with the parameters of the European XFEL.
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THPRO011	Investigation of the Coherence Properties of the Radiation at FLASH	2879
	E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	We present the results of the studies of coherence properties of the radiation from FLASH for fundamental harmonic and higher odd harmonics. General overview of the parameter space is performed including peak current, emittance, and external focusing. The results of our studies show that present configuration of FLASH free electron laser is not optimal for providing ultimate quality of the output radiation. We find that the physical origin of the problem is mode degeneration. The way for improving quality of the radiation is proposed.
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THPRO012	Wakefield-based Dechirper Structures for ELBE	2882
	F. Reimann, U. van Rienen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany U. Lehnert, P. Michel HZDR, Dresden, Germany
	Funding: Federal Ministry of Education and Research The efficient reduction of the pulse length and the energy width of electron beams plays a crucial role in the generation of short pulses in the range of sub-picoseconds at future light sources. At the radiation source ELBE in Dresden Rossendorf short pulses are required for coherent THz generation and laser-electron beam interaction experiments such as X-ray Thomson scattering. Energy dechirping can be carried out passively by wakefields generated when the electron beam passes through suitable structures, namely corrugated and dielectrically lined cylindrical pipes or dielectrically lined rectangular waveguides (,,*). All structures offer the possibility to tune the resulting wakefield and therefore the resulting energy chirp through a variation of purely geometrical or material parameters. In this paper we present a semi-analytical approach to determine the wakefield in dielectrically lined rectangular waveguide, starting with the expression of the electric field in terms of the structure's eigenmodes. Bane, Stupakov, SLAC-PUB-14925 (2012) Mosnier, Novokhatski, in: Proceedings of PAC97, Vancouver, Canada, 1997 * Antipov et al., in: Proceedings of IPAC2012, New Orleans, USA, 2012
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THPRO013	FERMI Status Report	2885
	M. Svandrlik, E. Allaria, F. Bencivenga, C. Callegari, F. Capotondi, D. Castronovo, 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, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, E. Ferrari, P. Finetti, L. Fröhlich, P. Furlan Radivo, G. Gaio, D. Gauthier, F. Gelmetti, L. Giannessi, M. Kiskinova, S. Krecic, M. Lonza, N. Mahne, C. Masciovecchio, M. Milloch, F. Parmigiani, G. Penco, L. Pivetta, O. Plekan, M. Predonzani, E. Principi, L. Raimondi, P. Rebernik Ribič, F. Rossi, L. Rumiz, C. Scafuri, C. Serpico, P. Sigalotti, C. Spezzani, C. Svetina, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	FERMI, the seeded Free Electron Laser (FEL) located at the Elettra laboratory in Trieste, Italy, consists of two FEL lines. The FEL-1 facility, covering the wavelength range between 20 and 100 nm, was officially opened to external users. The shorter wavelength range, between 20 and 4 nm, is covered by the FEL-2 line, a double stage cascade operating in the “fresh bunch injection” mode, which is still under commissioning. We will report on the different FEL-1 operation modes that can be offered for users and assess the performance of the facility. The progress in the commissioning of FEL-2 will then be addressed, in particular reporting the performance attained at the lower wavelength limit; this aspect is of great interest for the user’s community of the FERMI seeded FEL since it allows to carry out experiments below the carbon K-edge.
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THPRO016	Stable Generation of High Power Self-seeded XFEL at SACLA	2888
	T. Inagaki, N. Adumi, T. Fukui, T. Hara, Y. Inubushi, T. Ishikawa, H. Kimura, R. Kinjo, H. Maesaka, Y. Otake, H. Tanaka, T. Tanaka, K. Togawa, M. Yabashi RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan S. Goto, T.K. Kameshima, T. Ohata, K. Tono JASRI/SPring-8, Hyogo, Japan T. Hasegawa, S. Tanaka SES, Hyogo-pref., Japan A. Miura, H. Ohashi, H. Yamazaki Japan Synchrotron Radiation Research Institute (JASRI/SPring-8), Hyogo, Japan
	A self-seeded XFEL system using a transmitted beam under Bragg diffraction has been developed at the first compact XFEL facility SACLA in order to generate a brilliant single-mode XFEL with high temporal coherence. High stability and unique beam characteristics of SACLA should significantly contribute to achieve reliable, high-quality seeded XFEL operation. In particular, the short-pulse property that has been achieved in routine operation enables us to switch SASE and seeded mode quickly, without changing the electron beam parameters. This is also useful for delivering different modes to multiple beamlines simultaneously. In the test experiments carried out in autumn 2013, spectral narrowing was observed at 10 keV using diamond 400 reflection. Systematic optimization on beam properties is now in progress towards experimental use of seeded XFELs in summer 2014. This talk gives the overview of the plan, achieved results and ongoing R&D.
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THPRO017	Comparison of the Detection Performance of Three Nonlinear Crystals for the Electro-optic Sampling of a FEL-THz Source	2891
SUSPSNE011	use link to see paper's listing under its alternate paper code
	B. Wu, L. Cao, Q. Fu, P. Tan, Y.Q. Xiong HUST, Wuhan, People's Republic of China
	The detector of a FEL-THz source at HUST is now in the physical design stage. The electro-optic (EO) sampling method will be employed for the coherent detection. The performances of three widely used EO crystals will be evaluated and compared numerically in the time domain detection: zinc telluride (ZnTe), gallium arsenide (GaAs) and gallium phosphide (GaP). The phase matching properties are analyzed to find the appropriate probe wavelength. The EO detection response is calculated to select the suitable crystal thickness and to discuss the detection ability of each crystal.
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THPRO018	Electron-Magnetic-Phase Mixing in a Linac-driven FEL to Suppress Microbunching in the Optical Regime and Below	2894
	S. Di Mitri, S. Spampinati Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy H.-S. Kang PAL, Pohang, Kyungbuk, Republic of Korea S. Spampinati Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Control of microbunching instability is a fundamental requirement in modern high brightness electron linacs, in order to prevent malfunction of beam optical diagnostics and contamination in the generation of coherent radiation, such as free electron lasers. We present experimental control and suppression of microbunching instability-induced optical transition radiation by means of particles’ longitudinal phase mixing in a magnetic chicane. In presence of phase mixing, the intensity of the beam-emitted coherent optical transition radiation is reduced by one order of magnitude and brought to the same level provided, alternatively, by beam heating. The experimental results are in agreement with particle tracking and analytical evaluations of the instability gain. A discussion of applications of magnetic phase mixing to the generation of quasi-cold high-brightness ultra-relativistic electron beams is finally given. S. Di Mitri and S. Spampinati, Phys. Rev. Lett. 112, 134802 (2014)
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THPRO019	Current Status of PAL-XFEL Project	2897
	H.-S. Kang, K.W. Kim, I.S. Ko PAL, Pohang, Kyungbuk, Republic of Korea
	The PAL-XFEL, a 0.1-nm hard X-ray FEL facility consisting of a 10-GeV S-band linac, is being constructed in Pohang, South Korea. The installation of linac, undulator, and beam line will be completed by 2015. Its building construction is at its peak moment to be completed by December 2014. The major procurement contract was made in 2013 for the critical components of S-band linac modules and hard X-ray undulators. The commissioning will start in January 2016. We hope the first lasing will be achieved in early 2016.
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THPRO020	Linac Lattice Optimization for PAL-XFEL Hard X-ray FEL Line	2900
	H. Yang, J.H. Han, H.-S. Kang, I.S. Ko PAL, Pohang, Kyungbuk, Republic of Korea
	Funding: This work is supported by MSIP, Korea. PAL-XFEL is designed to generate 1 – 0.06-nm FEL in hard x-ray FEL line. The linac for hard x-ray generates 10-GeV, 200-pC, and 3-kA electron beam. It consists of accelerating columns, three bunch compressors, an X-band linearizer, and dog-leg line. We conduct ELEGANT simulations to obtain the optimized lattice for hard x-ray line. The candidates of the optimized lattice are obtained by Multi-Objective Genetic Algorithm (MOGA) whose objectives are the FEL saturation power and length. These are evaluated with their error tolerances. Error tolerances are obtained by two methods of error simulations. First, the linear interpolation method is conducted in order to determine the machine tolerance. Also, we find out the dominant machine parameters to increase the beam jitter by this method. Second, the error simulations with random errors of machine parameters are conducted to verify the results of the linear interpolation method and calculate beam jittering levels. In this paper, we present the details of the optimized linac lattice for hard x-ray FEL. Also, we present the procedure of the linac lattice optimization.
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THPRO022	JINR Powerful Laser Driver Applied for FEL Photoinjector	2906
	E. Syresin, N. Balalykin, M.A. Nozdrin, G. Shirkov, G.V. Trubnikov JINR, Dubna, Moscow Region, Russia E. Gacheva, E. Khazanov, G. Luchinin, S. Mironov, A. Poteomkin, V. Zelenogorsky IAP/RAS, Nizhny Novgorod, Russia
	Funding: The work is funded by the German Federal Ministry of education and Research, project 05K10CHE. The JINR develops a project of superconducting linear accelerator complex, based on a superconducting linear accelerator, for applications in nanoindustry, mainly for extreme ultraviolet lithography at a wavelength of 13.5 nm using kW-scale Free Electron Laser (FEL) light source. The application of kW-scale FEL source permits realizing EUV lithography with 22 nm, 16 nm resolutions and beyond. JINR-IAP collaboration constructed powerful laser driver applied for photoinjector of FEL linear accelerator which can be used for EUV lithography. To provide FEL kW-scale EUV radiation the photoinjector laser driver should provide a high macropulse repetition rate of 10 Hz, a long macropulse time duration of 0.8 ms and 8000 pulses per macropulse. The laser driver operates at wavelength of 260-266 nm on forth harmonic in the mode locking on base of Nd ions or Yb ions The laser driver micropulse energy of 1.6 uJ should provide formation of electron beam in FEL photoinjector with the bunch charge about 1 nC.
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THPRO023	Methods for the Optimization of a Tapered Free-Electron Laser	2909
SUSPSNE009	use link to see paper's listing under its alternate paper code
	A.W.L. Mak, F. Curbis, S. Werin MAX-lab, Lund, Sweden
	In a free-electron laser (FEL), the technique of wiggler tapering enables the sustained growth of radiation power beyond the initial saturation. With the goal to develop an X-ray FEL in the terawatt power regime, it is important to utilize this technique and optimize the taper profile, giving the wiggler parameter as a function of the distance along the wiggler line. This work examines two methods of optimization, which are based on the theoretical analysis by Kroll, Morton and Rosenbluth (KMR). Using the numerical simulation code GENESIS, the methods are applied to a case for the possible future FEL at the MAX IV Laboratory in Lund, Sweden, as well as a case for the LCLS-II.
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THPRO024	Progress of the EU-XFEL Laser Heater	2912
	M. Hamberg, V.G. Ziemann Uppsala University, Uppsala, Sweden
	Funding: Swedish research council under Project number DNR-828-2008-1093 for financial support. We describe the technical layout and report the status of the installation of the undulator, optical and vacuum systems of the laser heater for the EUXFEL. The laser heater is a device to increase the overall X-ray brightness stability. This is achieved by an optical laser system which induce an additional momentum spread in the electron bunches to reduce micro-bunching instabilities.
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THPRO025	Conceptual Design of a X-FEL Facility using CLIC X-band Accelerating Structure	2914
	A.A. Aksoy, Ö. Yavaş Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey D. Angal-Kalinin, J.A. Clarke Cockcroft Institute, Warrington, Cheshire, United Kingdom M.J. Boland SLSA, Clayton, Australia G. D'Auria, S. Di Mitri, C. Serpico Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy M. Doğan Dogus University, Istanbul, Turkey T.J.C. Ekelöf, R.J.M.Y. Ruber, V.G. Ziemann Uppsala University, Uppsala, Sweden W. Fang, Q. Gu SINAP, Shanghai, People's Republic of China A. Latina, D. Schulte, S. Stapnes, I. Syratchev, W. Wuensch CERN, Geneva, Switzerland Z. Nergiz Nigde University, Nigde University Science & Art Faculty, Nigde, Turkey
	Within last decade a linear accelerating structure with an average loaded gradient of 100 MV/m at 12 GHz has been demonstrated in the CLIC study. Recently, it has been proposed to use the CLIC structure to drive an FEL linac. In contrast to CLIC the linac would be powered by klystrons not by a drive beam. The main advantage of this proposal is achieving the required energies in a very short distance, thus the facility would be rather compact. In this study, we present the conceptual design parameters of a facility which could generate laser photon pulses covering the range of 1-75 Angstrom. Shorter wavelengths could also be reached with slightly increasing the energy.
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THPRO026	Design Parameters and Current Status of the TARLA Project	2918
	A.A. Aksoy, Ö. Karslı, Ç. Kaya, E. Kazancı, Ö. Yavaş Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey P. Arıkan Gazi University, Faculty of Arts and Sciences, Teknikokullar, Ankara, Turkey S. Özkorucuklu Istanbul University, Istanbul, Turkey
	Funding: Work is supported by Ministry of Development of Turkey with Grand No: DPT2006K-120470 The Turkish Accelerator and Radiation Laboratory in Ankara (TARLA) will operate two InfraRed Free Electron Lasers (IR-FEL) covering the range of 3-250 microns. The facility will consist of an injector fed by a thermionic triode gun with two-stage RF bunch compression, two superconducting accelerating ELBE modules operating at continuous wave (CW) mode and two independent optical resonator systems with different undulator period lengths. The electron beam will also be used to generate Bremsstrahlung radiation. In this paper, we discuss design goals of the project and present status and road map of the project. On behalf of TARLA Team
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THPRO027	Turkish Accelerator Center: The Status and Roadmap	2921
	A.A. Aksoy, Ö. Yavaş, H.D. Duran Yıldız Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey B. Akkus, S. Özkorucuklu, L.S. Yalcin Istanbul University, Istanbul, Turkey H. Aksakal, Z. Nergiz Nigde University, Nigde University Science & Art Faculty, Nigde, Turkey E. Algin Eskisehir Osmangazi University, Eskisehir, Turkey O. Cakir Ankara University, Faculty of Sciences, Ankara, Turkey
	Funding: Ankara University Turkish Accelerator Center (TAC) Project has started with support of the Ministry of Development (MD) of Turkey under the coordination of Ankara University. TAC is an inter-university collaboration with 12 Turkish Universities. An IR FEL facility (TARLA) based on Sc linac with 15-40 MeV energy under construction in Ankara as the first facility of TAC. It is expected that the TARLA facility will be commissioning in 2017. In addition to the TARLA, it is planned that Turkish Accelerator Center will include a third generation synchrotron radiation facility based on 1-3 GeV electron synchrotron (TAC SR), a fourth generation SASE FEL facility based on up to 5 GeV electron linac (TAC SASE FEL), a multi-purpose proton accelerator facility with 3 MeV-2 GeV beam energy (TAC PAF) and an electron-positron collider as a super charm factory (TAC PF). Construction phase of the proposed GeV scale accelerator facilities will cover next decade. In this presentation, main goals and road map of Turkish Accelerator Center will be explained. (http://thm.ankara.edu.tr) *On behalf of TAC collaboration
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THPRO029	A Front End for the CLARA FEL Test Facility at Daresbury Laboratory	2927
	P.H. Williams, D. Angal-Kalinin, J.A. Clarke, B.D. Fell, J.K. Jones, J.W. McKenzie, B.L. Militsyn STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	The next step towards the full CLARA facility is installation of the CLARA front end to comprise a 2m S-band linac section after the photoinjector gun. This will be suitable for both the velocity bunching and standard booster modes of CLARA. An S-bend will also be installed to deflect the beam into the current VELA line, enabling delivery of higher energy beams to two existing user areas. The current photoinjector beam diagnostics section can then be used to test a High Repetition Rate electron gun currently under development. We describe the proposed CLARA front end design. We define two beam dynamics working points for CLARA, one working point for sending beam from the CLARA Front End to VELA, and one working point to feed an interim user station prior to CLARA full construction in the straight-on position.
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THPRO030	Developments in CLARA Accelerator Design and Simulations	2930
	S. Spampinati Cockcroft Institute, Warrington, Cheshire, United Kingdom D. Angal-Kalinin, A.D. Brynes, D.J. Dunning, J.K. Jones, K.B. Marinov, J.W. McKenzie, B.L. Militsyn, N. Thompson, P.H. Williams STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom I.P.S. Martin DLS, Oxfordshire, 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. Updates on the electron beam simulations and code comparisons including wakefields are described. Simulations of the effects of geometric wakefields in the small-aperture FEL undulator are shown, as well as further simulations on potential FEL experiments using chirped beams. We also present the results of simulations on post-FEL diagnostics.
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THPRO031	Short Pulses THz FEL for the Oxford Accelerator Science Laboratory	2934
	T. Chanwattana, R. Bartolini, A. Seryi JAI, Oxford, United Kingdom R. Bartolini DLS, Oxfordshire, United Kingdom E. Tsesmelis CERN, Geneva, Switzerland
	The Accelerator Science Laboratory (ASL) is under development at the John Adams Institute in Oxford with the aim of fostering advanced accelerator concepts and applications. The option to install a short pulse THz FEL based on a conventional RF accelerator driven by a RF photocathode gun is being investigated. This report presents the concept of the facility, the accelerator physics and FEL studies and engineering integration in the University physics department.
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THPRO032	Studies on LPWA-based Light Sources driven by a Transverse Gradient Undulator	2937
SUSPSNE008	use link to see paper's listing under its alternate paper code
	T. Chanwattana, R. Bartolini, A. Seryi JAI, Oxford, United Kingdom R. Bartolini DLS, Oxfordshire, United Kingdom
	The Accelerator Science Laboratory (ASL) is under development at the John Adams Institute in Oxford with the aim of fostering advanced accelerator concepts and applications. The option to install a LPWA based light source driven by a transverse gradient undulator is being investigated. This report presents the accelerator physics, FEL studies and the performance expected from such a facility.
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THPRO033	Electron-bunch Shaping for Coherent Compton Scattering	4107
SUSPSNE010	use link to see paper's listing under its alternate paper code
	J.E. Thorne, P. Piot, I. Viti Northern Illinois University, DeKalb, Illinois, USA P. Piot Fermilab, Batavia, Illinois, USA
	Producing high-quality x rays could have important applications to high-precision medical imaging and national security. Inverse Compton scattering involving the head-on collision of a relativistic electron bunch with a high-power laser offers a viable path toward the realization of a compact x-ray source. A method consisting in reflecting a short-pulse laser onto a “relativistic mirror” (a moving thin sheet of electrons) has been proposed and recently demonstrated as a way to enhance the back-scattered photon flux by operating in the coherent regime. In this contribution we present particle-in-cell numerical simulations of the inverse Compton scattering process and especially investigate the impact of the laser-pulse and electron-beam distributions that could substantially improve the x-ray production via coherent emission.
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THPRO034	Design of the LCLS-II Electron Optics	2940
	Y. Nosochkov, P. Emma, T.O. Raubenheimer, M. Woodley SLAC, Menlo Park, California, USA
	Funding: Work supported by the US Department of Energy Contract DE-AC02-76SF00515. The LCLS-II project is a high repetition rate, high average brightness free-electron laser based on the existing facilities at the SLAC National Accelerator Laboratory. The LCLS-II will be driven by a new CW superconducting RF (SCRF) 4-GeV linac replacing the existing Cu-linac in the 1st km of the linac tunnel. The SCRF linac will include chicanes for providing full compression of the electron bunch length. After the linac, the electron beam will be directed into the existing 2-km bypass line connecting to the Beam Switch Yard (BSY), where a new spreader system will allow a high rate bunch-by-bunch deflection into the hard X-ray (HXR) or soft X-ray (SXR) transport lines, or towards the BSY high power dump. The HXR line will include a new variable gap undulator replacing the existing LCLS-I undulator and will reuse the existing LCLS-I linac-to-undulator and dump transport lines. The SXR will require a new transport line sharing the same tunnel with the HXR and will include a new variable gap undulator. Overview of the electron beam transport and the optics design are presented.
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THPRO035	Improving and Maintaining FEL Beam Stability of the LCLS	2943
	F.-J. Decker, A.L. Benwell, W.S. Colocho, Z. Huang, A. Krasnykh, J.R. Lewandowski, T.J. Maxwell, J. Sheppard, J.L. Turner SLAC, Menlo Park, California, USA
	Funding: *Work supported by U.S. Department of Energy, Contract DE-AC02-76SF00515. The beam stability of the Linac Coherent Light Source (LCLS) has seen many improvements over the years and has matured to a state where progress is slow and maintaining the best stability is becoming the main challenge. Single sources which are identified by various means contribute to only about 10 to 20% of the whole jitter power, meaning that their elimination gives only a small improvement of 5 to 10%. New sources need to be identified fast. Especially slow variations of a few seconds to minutes time scale are often hidden and partially corrected by feedback systems. A few episodes of increased jitter have shown the limitations of some of the feedback systems. Stability for all dimensions, transverse, longitudinal, and intensity are presented.
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THPRO038	Energy-Silenced HGHG	2946
	E. Hemsing, G. Marcus, A. Marinelli SLAC, Menlo Park, California, USA D. Xiang Shanghai Jiao Tong University, Shanghai, People's Republic of China
	We study the effect of longitudinal space charge on the correlated energy spread of a relativistic beam that has been microbunched for the emission of high harmonic radiation. We show that, in the case of microbunching induced by a laser modulator followed by a dispersive chicane, longitudinal space charge forces can act to significantly reduce the induced energy spread of the beam without a reduction in the harmonic bunching content. This effect may significantly relax constraints on the harmonic number achievable in HGHG FELs, which are otherwise limited by the induced energy spread from the laser.
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THPRO039	Model-independent Description of Shot-noise, Amplification and Saturation	2949
	Y.C. Jing, V. Litvinenko, G. Wang BNL, Upton, Long Island, New York, USA V. Litvinenko Stony Brook University, Stony Brook, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. High-gain FEL is one of many electron-beam instabilities, which have a number of common features linking the shot noise, the amplification and the saturation. In this paper we present a new, model-independent description of the interplay between these effects and derivation of a simple formula determining the saturation and maximum attainable gain in such instabilities. Application of this model-independent formula to FEL is compared with FEL theory and simulations. We describe limitations resulting from these finding for FEL amplifiers used for seeded FELs and for Coherent electron Cooling.
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THPRO050	Study of a THz/VUV Free Electron Laser Facility in Taiwan	2980
	N.Y. Huang, M.C. Chou, C.-S. Hwang, W.K. Lau, A.P. Lee NSRRC, Hsinchu, Taiwan A. Chao, J. Wu SLAC, Menlo Park, California, USA C.H. Chen, Y.-C. Huang NTHU, Hsinchu, Taiwan X.M. Yang DICP, Dalian, People's Republic of China
	A free electron laser (FEL) facility aimed for VUV and THz radiation is being studied at National Synchrotron Radiation Research Center (NSRRC) in Taiwan. Strong consideration has been given to minimize the cost by making maximum use of existing hardware at NSRRC. One unique consideration is to use an existing undulator for the dual functions of the THz radiator and the modulator of a HGHG section. Design emphasizes versatility of operation and beam quality control and compensation of nonlinearities, with a vision that it will allow as much as possible future upgrades as well as later R&D of FEL physics. The polarization control of the THz radiation provides novel application for the users. The facility is to be housed in the existing 38-m by 5-m tunnel of the TPS Linac Test Laboratory.
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THPME081	Plans for an Australian XFEL Using a CLIC X-band Linac	3424
	M.J. Boland, T.K. Charles, R.T. Dowd, G. LeBlanc, Y.E. Tan, K.P. Wootton, D. Zhu SLSA, Clayton, Australia R. Corsini, A. Grudiev, A. Latina, D. Schulte, S. Stapnes, I. Syratchev, W. Wuensch CERN, Geneva, Switzerland
	Preliminary plans are presented for a sub-Angstrom wavelength XFEL at the Australian Synchrotron light source site. The design is based around a 6 GeV x-band linac from the CLIC Project. One of the motivations for the design is to have an XFEL co-located on the site with existing storage ring based synchrotron light source. The desire and ability of the Australian photon science community to win beamtime on existing XFELs has lead to this design study to plan for a future machine in Australia. The technology choice is also driven by the Australian participation in the CLIC Collaboration and the local HEP community.
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THPRI074	Colorado State University (CSU) Accelerator and FEL Facility	3937
	S. Biedron, C. Carrico, A. D'Audney, J.P. Edelen, J. Einstein, C.C. Hall, J.R. Harris, K. Horovitz, J. Martinez, S.V. Milton, A.L. Morin, N. Sipahi, T. Sipahi, J.E. Williams, P.J.M. van der Slot CSU, Fort Collins, Colorado, USA P.J.M. van der Slot Mesa+, Enschede, The Netherlands P.J.M. van der Slot Twente University, Laser Physics and Non-Linear Optics Group, Enschede, The Netherlands
	The Colorado State University (CSU) Accelerator Facility will include a 6-MeV L-Band electron linear accelerator (linac) with a free-electron laser (FEL) system capable of producing Terahertz (THz) radiation, a laser laboratory, a microwave test stand, and a magnetic test stand. The photocathode drive linac will be used in conjunction with a hybrid undulator capable of producing THz radiation. Details of the systems used in CSU Accelerator Facility are discussed.
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THPRI101	Coupler Kick and Cavity Tilt Effects on Emittance Preservation in Linear Accelerators	4013
	A.V. Tsakanian, G.A. Amatuni, B. Grigoryan, I.N. Margaryan, V.M. Tsakanov CANDLE SRI, Yerevan, Armenia
	The effects of the coupler kick and the cavity tilts on the beam dynamics in long linear accelerator are studied. The dispersive and wakefield caused beam emittance dilution are evaluated analytically using two particle model of the beam. The numerical simulations for the European XFEL project are presented.
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Paper

Title

Page

Innovative Ideas for Single-pass FELs

12

T. Hara
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

SASE FELs are a powerful light source in short wavelengths from VUV to X-ray regions to investigate matters and phenomena. SASE was first experimentally obtained in 2000 at DESY TTF with an output wavelength of 10⁹ nm. Subsequently, FLASH, LCLS and SACLA have achieved lasing in VUV, soft X-rays and hard X-rays. Although SASE has already been widely used for many application experiments in broad scientific fields, its spiky spectrum and time structures due to the lack of longitudinal coherence sometimes become problematic. To improve its longitudinal coherence, various ideas have been proposed and some of them are already demonstrated experimentally, such as a self-seeded scheme, high-gain harmonic generation (HGHG) and echo-enabled harmonic generation (EEHG). There is also another direction of developments to enhance the capability and potentiality of SASE, for example short pulse generation and two-color lasing. This talk will review recent innovative ideas of short wavelength FELs together with their experimental results.

Slides MOYAA01 [10.701 MB]

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TUZA02

THz Facility at ELBE: A Versatile Test Facility for Electron Bunch Diagnostics on Quasi-CW Electron Beams

933

M. Gensch, B.W. Green, J. Hauser, S. Kovalev, M. Kuntzsch, U. Lehnert, P. Michel, R. Schurig
HZDR, Dresden, Germany
A. Al-Shemmary, V. B. Asgekar, T. Golz, H. Schlarb, N. Stojanovic, S. Vilcins
DESY, Hamburg, Germany
A.S. Fisher
SLAC, Menlo Park, California, USA
G. Geloni
XFEL. EU, Hamburg, Germany
A.-S. Müller, M. Schwarz
KIT, Karlsruhe, Germany
N.E. Neumann, D. Plettemeier
TU Dresden, Dresden, Germany

At the Helmholtz-Zentrum Dresden-Rossendorf near Dresden a quasi-cw low-energy electron linear accelerator based on superconducting radiofrequency technology is operated successfully for more than 10 years. The ELBE accelerator is driving several secondary radiation sources including 2 infrared free electron lasers. A new addition will be a THz facility that aims to make use of super-radiant THz radiation. In its final form the THz facility shall consist of one coherent diffraction radiator and one undulator source which provide high-field THz pulses at unprecedented repetition rates. While the medium term goal is to establish a unique user facility for nonlinear THz science, the THz sources are already used as a test facility for novel diagnostic techniques on quasi-cw electron beams. The progress of the developments is reported and an outlook into future challenges and opportunities is given.

Slides TUZA02 [3.041 MB]

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TUOCA01

The Linac Coherent Light Source-II Project

935

J.N. Galayda
SLAC, Menlo Park, California, USA

Funding: Work supported by US DOE Contract DE-AC02-766SF00515
The “Linac Coherent Light Source–II” Project, initiated in September 2010, has gone through a radical transformation beginning in August 2013. In its new form, LCLS-II will construct a 4 GeV CW superconducting linac in the first kilometre of the existing linac tunnel. A new undulator, optimized as a soft x-ray (200-1,300 eV) source, will receive electrons from the new SC linac. The existing undulator system will be replaced with a new variable gap device, which will receive electrons from either the new SC linac (providing 1-5 keV photons) or the copper linac presently used by LCLS (providing 1-25 keV x-rays). First light from the new facility is expected in September 2019.
galayda@slac.stanford.edu

Slides TUOCA01 [9.380 MB]

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TUOCA02

Status of the Free Electron Laser User Facility FLASH

938

M. Vogt, B. Faatz, J. Feldhaus, K. Honkavaara, S. Schreiber, R. Treusch
DESY, Hamburg, Germany

FLASH, the Free Electron Laser User Facility at DESY (Hamburg, Germany), delivers high brilliance XUV and soft X-ray FEL radiation to photon experiments. After a shutdown to connect the second undulator beamline FLASH2 to the FLASH linac, re-commissioning of FLASH started in autumn 2013. The year 2014 is dedicated to FLASH1 user experiments. The commissioning of the FLASH2 beamline takes place in 2014 in parallel to FLASH1 operation.

Slides TUOCA02 [9.156 MB]

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THPRO003

Progress of the LUNEX5 demonstator Project

2856

M.-E. Couprie, C. Benabderrahmane, P. Berteaud, C. Bourassin-Bouchet, F. Bouvet, L. Cassinari, L. Chapuis, J. Daillant, M. Diop, M.E. El Ajjouri, C. Evain, C. Herbeaux, N. Hubert, M. Labat, P. Lebasque, A. Lestrade, A. Loulergue, P. Marchand, O. Marcouillé, J.L. Marlats, C. Miron, P. Morin, A. Nadji, F. Polack, F. Ribeiro, J.P. Ricaud, P. Roy, K. Tavakoli, M. Valléau, D. Zerbib
SOLEIL, Gif-sur-Yvette, France
S. Bielawski, E. Roussel, C. Szwaj
PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
B. Carré, D. Garzella
CEA/DSM/DRECAM/SPAM, Gif-sur-Yvette, France
X. Davoine
CEA/DAM/DIF, Arpajon, France
N. Delerue
LAL, Orsay, France
G. Devanz
CEA/DSM/IRFU, France
A. Dubois, J. Lüning
CCPMR, Paris, France
G. Lambert, R. Lehé, V. Malka, A. Rousse, C. Thaury
LOA, Palaiseau, France
C. Madec, A. Mosnier
CEA/IRFU, Gif-sur-Yvette, France

LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation) aims at investigating the production of short, intense, coherent pulses in the 40-4 nm spectral range [1]. It comprises two types of accelerators connected to a single Free Electron Laser (FEL) for advanced seeding configurations (seeding with High order Harmonic in Gas, echo). A 400 MeV superconducting Linear Accelerator, adapted for studies of advanced FEL schemes, will enable future upgrade towards high repetition rate and multi-user operation by splitting part of the macropulse to different FEL lines. A 0.4 - 1 GeV Laser Wake Field Accelerator (LWFA) [2] will also be qualified by the FEL application. After the Conceptual Design Report, R&D has been launched on different sub components. Following transport theoretical studies of longitudinal and transverse manipulation of a LWFA electron beam enabling to provide theoretical amplification, a test experiment is under preparation.

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THPRO004

Study of the CLIO FEL in the Far-infrared in a Partially Guided Mode

2859

J.-M. Ortega, J.P. Berthet, F. Glotin, R. Prazeres
LCP/CLIO, Orsay, Cedex, France

The infrared free-electron laser offers a large tunability since the FEL gain remains high throughout the infrared spectral range, and the reflectivity of metal mirrors remains also close to unity. The main limitation comes from the diffraction of the optical beam due to the finite size of the vacuum chamber of the undulator. A solution is to use this chamber as a waveguide by adaptating the radius of curvature of the cavity mirrors to this regime. Then, as has been shown before* a minimum appears in the spectrum that can be produced by the FEL. We discuss the physical mechanism of this particular regime and compare it to experiments using vacuum chambers of different tranverse sizes. A good agreement is found with results of simulations and with a simple analytical formula.
* Analysis of the periodic power gaps observed in the tuning range of FELs with a partial waveguide, R. Prazeres, F. Glotin, J.-M. Ortega, Phys. Rev. STAB12, 010701 (2009)

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THPRO006

Configuration Management in the Series Production of the XFEL Accelerator Modules

2863

L. Hagge, S. Barbanotti, S. Eucker, A. Frank, K. Jensch, J. Kreutzkamp, D. Käfer, A. Matheisen
DESY, Hamburg, Germany
S. Berry, O. Napoly
CEA/DSM/IRFU, France
C. Cloué, C. Madec, T. Trublet
CEA/IRFU, Gif-sur-Yvette, France

The series production of the superconducting accelerator modules for the European XFEL requires a production rate of one module per week. For this, assembly procedures have to be well-defined and repeatable, and the punctual supply of parts from the contributing institutes has to be assured. Configuration management (CM) has been introduced for clarification of responsibilities and establishing procedures. CM provides unique identification of parts, part status and location tracking, versioning of documentation, and procedures for change control, auditing and handling non-conformities. The configuration database, which is based on DESY’s Engineering Data Management System, contains the entire information which is necessary for assembling the accelerator modules. The content ranges from work instructions how to build a cryomodule up to individual records of all produced parts. Workflow and reports help tracking production progress and establishing production quality. The presentation gives an overview of the CM solution which is in place for the assembly of the XFEL accelerator modules, and reports experience and lessons learned from series production of the first modules.

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THPRO007

Beam-based Alignment in the European XFEL SASE1

2867

H. Jin, W. Decking, T. Limberg
DESY, Hamburg, Germany

The European X-ray Free Electron Laser (E-XFEL) provides an ultra-short and high-brilliant photon pulses of spatially coherent X-rays with wavelengths down to 0.05 nm by using three undulator systems. Within these undulator systems, the orbit trajectory is required to be straight to a few micron over each gain length, so that the photon beam is capable of overlapping efficiently with the electron beam. However, this requirement is not obtainable with ordinary mechanical alignment methods. For this reason, a beam-based alignment (BBA) method using BPM readings of different beam energies is applied to the E-XFEL SASE1 undulators. In this report, we describe the BBA simulation for SASE1 including alignment errors of quadrupoles and BPMs. After correction, the desired range of the orbit trajectory is attained with high confidence. In addition, to identify the reliability of an aligned orbit trajectory acquired from the BBA simulation, we present here the SASE FEL radiation simulation, in which we observe a slight decrease of radiation energy and power.

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THPRO008

Obtaining High Degree of Circular Polarization at X-ray FELs via a Reverse Undulator Taper

2870

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 (or cross-planar) afterburner, but then one should have an efficient method to suppress powerful linearly polarized background from the main undulator. In this paper we propose a new method for such a suppression: an application of the reverse taper in the main undulator. We discover that 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. Considering SASE3 undulator of the European XFEL as a practical example, we demonstrate that soft X-ray radiation pulses with peak power in excess of 100 GW and an ultimately high degree of circular polarization can be produced.
Phys. Rev. ST-AB 16(2013)110702

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THPRO009

Harmonic Lasing in X-ray FELs

2873

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

Contrary to nonlinear harmonic generation, harmonic lasing in a high-gain FEL can provide much more intense, stable, and narrow-band FEL beam which is easier to handle if the fundamental is suppressed. We perform a parametrization of the solution of eigenvalue equation for lasing at odd harmonics, and present explicit expression for FEL gain length, taking into account all essential effects. We propose and discuss methods for suppression of the fundamental. We also suggest a combined use of harmonic lasing and lasing at the retuned fundamental wavelength in order to reduce bandwidth and to increase brilliance of X-ray beam. We discover that in a part of the parameter space, corresponding to the operating range of soft X-ray beamlines of X-ray FEL facilities, harmonics can grow faster than the fundamental. We suggest that harmonic lasing can be widely used in the existing or planned X-ray FEL facilities. LCLS after a minor modification can lase at the 3rd harmonic up to the photon energy of 25-30 keV providing multi-gigawatt power level. At the European XFEL the harmonic lasing would allow to extend operating range up to 100 keV, to reduce bandwidth and increase brilliance.

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THPRO010

Analysis of Operation of Harmonic Lasing Self-seeded FEL

2876

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

Harmonic lasing self-seeded FEL holds great potential for significant improvement of the the longitudinal coherence of the radiation. A gap-tunable undulator is divided into two parts by setting two different undulator parameters 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 defined by the harmonic lasing (i.e. it 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 undulator tapering in the deep nonlinear regime would allow to generate higher peak powers approaching TW level. The scheme is illustrated with the parameters of the European XFEL.

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THPRO011

Investigation of the Coherence Properties of the Radiation at FLASH

2879

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

We present the results of the studies of coherence properties of the radiation from FLASH for fundamental harmonic and higher odd harmonics. General overview of the parameter space is performed including peak current, emittance, and external focusing. The results of our studies show that present configuration of FLASH free electron laser is not optimal for providing ultimate quality of the output radiation. We find that the physical origin of the problem is mode degeneration. The way for improving quality of the radiation is proposed.

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THPRO012

Wakefield-based Dechirper Structures for ELBE

2882

F. Reimann, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
U. Lehnert, P. Michel
HZDR, Dresden, Germany

Funding: Federal Ministry of Education and Research
The efficient reduction of the pulse length and the energy width of electron beams plays a crucial role in the generation of short pulses in the range of sub-picoseconds at future light sources. At the radiation source ELBE in Dresden Rossendorf short pulses are required for coherent THz generation and laser-electron beam interaction experiments such as X-ray Thomson scattering. Energy dechirping can be carried out passively by wakefields generated when the electron beam passes through suitable structures, namely corrugated and dielectrically lined cylindrical pipes or dielectrically lined rectangular waveguides (*,**,***). All structures offer the possibility to tune the resulting wakefield and therefore the resulting energy chirp through a variation of purely geometrical or material parameters. In this paper we present a semi-analytical approach to determine the wakefield in dielectrically lined rectangular waveguide, starting with the expression of the electric field in terms of the structure's eigenmodes.
* Bane, Stupakov, SLAC-PUB-14925 (2012)
** Mosnier, Novokhatski, in: Proceedings of PAC97, Vancouver, Canada, 1997
*** Antipov et al., in: Proceedings of IPAC2012, New Orleans, USA, 2012

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THPRO013

FERMI Status Report

2885

M. Svandrlik, E. Allaria, F. Bencivenga, C. Callegari, F. Capotondi, D. Castronovo, 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, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, E. Ferrari, P. Finetti, L. Fröhlich, P. Furlan Radivo, G. Gaio, D. Gauthier, F. Gelmetti, L. Giannessi, M. Kiskinova, S. Krecic, M. Lonza, N. Mahne, C. Masciovecchio, M. Milloch, F. Parmigiani, G. Penco, L. Pivetta, O. Plekan, M. Predonzani, E. Principi, L. Raimondi, P. Rebernik Ribič, F. Rossi, L. Rumiz, C. Scafuri, C. Serpico, P. Sigalotti, C. Spezzani, C. Svetina, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

FERMI, the seeded Free Electron Laser (FEL) located at the Elettra laboratory in Trieste, Italy, consists of two FEL lines. The FEL-1 facility, covering the wavelength range between 20 and 100 nm, was officially opened to external users. The shorter wavelength range, between 20 and 4 nm, is covered by the FEL-2 line, a double stage cascade operating in the “fresh bunch injection” mode, which is still under commissioning. We will report on the different FEL-1 operation modes that can be offered for users and assess the performance of the facility. The progress in the commissioning of FEL-2 will then be addressed, in particular reporting the performance attained at the lower wavelength limit; this aspect is of great interest for the user’s community of the FERMI seeded FEL since it allows to carry out experiments below the carbon K-edge.

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THPRO016

Stable Generation of High Power Self-seeded XFEL at SACLA

2888

T. Inagaki, N. Adumi, T. Fukui, T. Hara, Y. Inubushi, T. Ishikawa, H. Kimura, R. Kinjo, H. Maesaka, Y. Otake, H. Tanaka, T. Tanaka, K. Togawa, M. Yabashi
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
S. Goto, T.K. Kameshima, T. Ohata, K. Tono
JASRI/SPring-8, Hyogo, Japan
T. Hasegawa, S. Tanaka
SES, Hyogo-pref., Japan
A. Miura, H. Ohashi, H. Yamazaki
Japan Synchrotron Radiation Research Institute (JASRI/SPring-8), Hyogo, Japan

A self-seeded XFEL system using a transmitted beam under Bragg diffraction has been developed at the first compact XFEL facility SACLA in order to generate a brilliant single-mode XFEL with high temporal coherence. High stability and unique beam characteristics of SACLA should significantly contribute to achieve reliable, high-quality seeded XFEL operation. In particular, the short-pulse property that has been achieved in routine operation enables us to switch SASE and seeded mode quickly, without changing the electron beam parameters. This is also useful for delivering different modes to multiple beamlines simultaneously. In the test experiments carried out in autumn 2013, spectral narrowing was observed at 10 keV using diamond 400 reflection. Systematic optimization on beam properties is now in progress towards experimental use of seeded XFELs in summer 2014. This talk gives the overview of the plan, achieved results and ongoing R&D.

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THPRO017

Comparison of the Detection Performance of Three Nonlinear Crystals for the Electro-optic Sampling of a FEL-THz Source

2891

SUSPSNE011

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B. Wu, L. Cao, Q. Fu, P. Tan, Y.Q. Xiong
HUST, Wuhan, People's Republic of China

The detector of a FEL-THz source at HUST is now in the physical design stage. The electro-optic (EO) sampling method will be employed for the coherent detection. The performances of three widely used EO crystals will be evaluated and compared numerically in the time domain detection: zinc telluride (ZnTe), gallium arsenide (GaAs) and gallium phosphide (GaP). The phase matching properties are analyzed to find the appropriate probe wavelength. The EO detection response is calculated to select the suitable crystal thickness and to discuss the detection ability of each crystal.

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THPRO018

Electron-Magnetic-Phase Mixing in a Linac-driven FEL to Suppress Microbunching in the Optical Regime and Below

2894

S. Di Mitri, S. Spampinati
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
H.-S. Kang
PAL, Pohang, Kyungbuk, Republic of Korea
S. Spampinati
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Control of microbunching instability is a fundamental requirement in modern high brightness electron linacs, in order to prevent malfunction of beam optical diagnostics and contamination in the generation of coherent radiation, such as free electron lasers. We present experimental control and suppression of microbunching instability-induced optical transition radiation by means of particles’ longitudinal phase mixing in a magnetic chicane*. In presence of phase mixing, the intensity of the beam-emitted coherent optical transition radiation is reduced by one order of magnitude and brought to the same level provided, alternatively, by beam heating. The experimental results are in agreement with particle tracking and analytical evaluations of the instability gain. A discussion of applications of magnetic phase mixing to the generation of quasi-cold high-brightness ultra-relativistic electron beams is finally given.
* S. Di Mitri and S. Spampinati, Phys. Rev. Lett. 112, 134802 (2014)

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THPRO019

Current Status of PAL-XFEL Project

2897

H.-S. Kang, K.W. Kim, I.S. Ko
PAL, Pohang, Kyungbuk, Republic of Korea

The PAL-XFEL, a 0.1-nm hard X-ray FEL facility consisting of a 10-GeV S-band linac, is being constructed in Pohang, South Korea. The installation of linac, undulator, and beam line will be completed by 2015. Its building construction is at its peak moment to be completed by December 2014. The major procurement contract was made in 2013 for the critical components of S-band linac modules and hard X-ray undulators. The commissioning will start in January 2016. We hope the first lasing will be achieved in early 2016.

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THPRO020

Linac Lattice Optimization for PAL-XFEL Hard X-ray FEL Line

2900

H. Yang, J.H. Han, H.-S. Kang, I.S. Ko
PAL, Pohang, Kyungbuk, Republic of Korea

Funding: This work is supported by MSIP, Korea.
PAL-XFEL is designed to generate 1 – 0.06-nm FEL in hard x-ray FEL line. The linac for hard x-ray generates 10-GeV, 200-pC, and 3-kA electron beam. It consists of accelerating columns, three bunch compressors, an X-band linearizer, and dog-leg line. We conduct ELEGANT simulations to obtain the optimized lattice for hard x-ray line. The candidates of the optimized lattice are obtained by Multi-Objective Genetic Algorithm (MOGA) whose objectives are the FEL saturation power and length. These are evaluated with their error tolerances. Error tolerances are obtained by two methods of error simulations. First, the linear interpolation method is conducted in order to determine the machine tolerance. Also, we find out the dominant machine parameters to increase the beam jitter by this method. Second, the error simulations with random errors of machine parameters are conducted to verify the results of the linear interpolation method and calculate beam jittering levels. In this paper, we present the details of the optimized linac lattice for hard x-ray FEL. Also, we present the procedure of the linac lattice optimization.

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THPRO022

JINR Powerful Laser Driver Applied for FEL Photoinjector

2906

E. Syresin, N. Balalykin, M.A. Nozdrin, G. Shirkov, G.V. Trubnikov
JINR, Dubna, Moscow Region, Russia
E. Gacheva, E. Khazanov, G. Luchinin, S. Mironov, A. Poteomkin, V. Zelenogorsky
IAP/RAS, Nizhny Novgorod, Russia

Funding: The work is funded by the German Federal Ministry of education and Research, project 05K10CHE.
The JINR develops a project of superconducting linear accelerator complex, based on a superconducting linear accelerator, for applications in nanoindustry, mainly for extreme ultraviolet lithography at a wavelength of 13.5 nm using kW-scale Free Electron Laser (FEL) light source. The application of kW-scale FEL source permits realizing EUV lithography with 22 nm, 16 nm resolutions and beyond. JINR-IAP collaboration constructed powerful laser driver applied for photoinjector of FEL linear accelerator which can be used for EUV lithography. To provide FEL kW-scale EUV radiation the photoinjector laser driver should provide a high macropulse repetition rate of 10 Hz, a long macropulse time duration of 0.8 ms and 8000 pulses per macropulse. The laser driver operates at wavelength of 260-266 nm on forth harmonic in the mode locking on base of Nd ions or Yb ions The laser driver micropulse energy of 1.6 uJ should provide formation of electron beam in FEL photoinjector with the bunch charge about 1 nC.

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THPRO023

Methods for the Optimization of a Tapered Free-Electron Laser

2909

SUSPSNE009

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A.W.L. Mak, F. Curbis, S. Werin
MAX-lab, Lund, Sweden

In a free-electron laser (FEL), the technique of wiggler tapering enables the sustained growth of radiation power beyond the initial saturation. With the goal to develop an X-ray FEL in the terawatt power regime, it is important to utilize this technique and optimize the taper profile, giving the wiggler parameter as a function of the distance along the wiggler line. This work examines two methods of optimization, which are based on the theoretical analysis by Kroll, Morton and Rosenbluth (KMR). Using the numerical simulation code GENESIS, the methods are applied to a case for the possible future FEL at the MAX IV Laboratory in Lund, Sweden, as well as a case for the LCLS-II.

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THPRO024

Progress of the EU-XFEL Laser Heater

2912

M. Hamberg, V.G. Ziemann
Uppsala University, Uppsala, Sweden

Funding: Swedish research council under Project number DNR-828-2008-1093 for financial support.
We describe the technical layout and report the status of the installation of the undulator, optical and vacuum systems of the laser heater for the EUXFEL. The laser heater is a device to increase the overall X-ray brightness stability. This is achieved by an optical laser system which induce an additional momentum spread in the electron bunches to reduce micro-bunching instabilities.

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THPRO025

Conceptual Design of a X-FEL Facility using CLIC X-band Accelerating Structure

2914

A.A. Aksoy, Ö. Yavaş
Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey
D. Angal-Kalinin, J.A. Clarke
Cockcroft Institute, Warrington, Cheshire, United Kingdom
M.J. Boland
SLSA, Clayton, Australia
G. D'Auria, S. Di Mitri, C. Serpico
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
M. Doğan
Dogus University, Istanbul, Turkey
T.J.C. Ekelöf, R.J.M.Y. Ruber, V.G. Ziemann
Uppsala University, Uppsala, Sweden
W. Fang, Q. Gu
SINAP, Shanghai, People's Republic of China
A. Latina, D. Schulte, S. Stapnes, I. Syratchev, W. Wuensch
CERN, Geneva, Switzerland
Z. Nergiz
Nigde University, Nigde University Science & Art Faculty, Nigde, Turkey

Within last decade a linear accelerating structure with an average loaded gradient of 100 MV/m at 12 GHz has been demonstrated in the CLIC study. Recently, it has been proposed to use the CLIC structure to drive an FEL linac. In contrast to CLIC the linac would be powered by klystrons not by a drive beam. The main advantage of this proposal is achieving the required energies in a very short distance, thus the facility would be rather compact. In this study, we present the conceptual design parameters of a facility which could generate laser photon pulses covering the range of 1-75 Angstrom. Shorter wavelengths could also be reached with slightly increasing the energy.

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THPRO026

Design Parameters and Current Status of the TARLA Project

2918

A.A. Aksoy, Ö. Karslı, Ç. Kaya, E. Kazancı, Ö. Yavaş
Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey
P. Arıkan
Gazi University, Faculty of Arts and Sciences, Teknikokullar, Ankara, Turkey
S. Özkorucuklu
Istanbul University, Istanbul, Turkey

Funding: Work is supported by Ministry of Development of Turkey with Grand No: DPT2006K-120470
The Turkish Accelerator and Radiation Laboratory in Ankara (TARLA) will operate two InfraRed Free Electron Lasers (IR-FEL) covering the range of 3-250 microns. The facility will consist of an injector fed by a thermionic triode gun with two-stage RF bunch compression, two superconducting accelerating ELBE modules operating at continuous wave (CW) mode and two independent optical resonator systems with different undulator period lengths. The electron beam will also be used to generate Bremsstrahlung radiation. In this paper, we discuss design goals of the project and present status and road map of the project.
On behalf of TARLA Team

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THPRO027

Turkish Accelerator Center: The Status and Roadmap

2921

A.A. Aksoy, Ö. Yavaş, H.D. Duran Yıldız
Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey
B. Akkus, S. Özkorucuklu, L.S. Yalcin
Istanbul University, Istanbul, Turkey
H. Aksakal, Z. Nergiz
Nigde University, Nigde University Science & Art Faculty, Nigde, Turkey
E. Algin
Eskisehir Osmangazi University, Eskisehir, Turkey
O. Cakir
Ankara University, Faculty of Sciences, Ankara, Turkey

Funding: Ankara University
Turkish Accelerator Center (TAC) Project has started with support of the Ministry of Development (MD) of Turkey under the coordination of Ankara University. TAC is an inter-university collaboration with 12 Turkish Universities. An IR FEL facility (TARLA) based on Sc linac with 15-40 MeV energy under construction in Ankara as the first facility of TAC. It is expected that the TARLA facility will be commissioning in 2017. In addition to the TARLA, it is planned that Turkish Accelerator Center will include a third generation synchrotron radiation facility based on 1-3 GeV electron synchrotron (TAC SR), a fourth generation SASE FEL facility based on up to 5 GeV electron linac (TAC SASE FEL), a multi-purpose proton accelerator facility with 3 MeV-2 GeV beam energy (TAC PAF) and an electron-positron collider as a super charm factory (TAC PF). Construction phase of the proposed GeV scale accelerator facilities will cover next decade. In this presentation, main goals and road map of Turkish Accelerator Center will be explained. (http://thm.ankara.edu.tr)
*On behalf of TAC collaboration

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THPRO029

A Front End for the CLARA FEL Test Facility at Daresbury Laboratory

2927

P.H. Williams, D. Angal-Kalinin, J.A. Clarke, B.D. Fell, J.K. Jones, J.W. McKenzie, B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

The next step towards the full CLARA facility is installation of the CLARA front end to comprise a 2m S-band linac section after the photoinjector gun. This will be suitable for both the velocity bunching and standard booster modes of CLARA. An S-bend will also be installed to deflect the beam into the current VELA line, enabling delivery of higher energy beams to two existing user areas. The current photoinjector beam diagnostics section can then be used to test a High Repetition Rate electron gun currently under development. We describe the proposed CLARA front end design. We define two beam dynamics working points for CLARA, one working point for sending beam from the CLARA Front End to VELA, and one working point to feed an interim user station prior to CLARA full construction in the straight-on position.

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THPRO030

Developments in CLARA Accelerator Design and Simulations

2930

S. Spampinati
Cockcroft Institute, Warrington, Cheshire, United Kingdom
D. Angal-Kalinin, A.D. Brynes, D.J. Dunning, J.K. Jones, K.B. Marinov, J.W. McKenzie, B.L. Militsyn, N. Thompson, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
I.P.S. Martin
DLS, Oxfordshire, 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. Updates on the electron beam simulations and code comparisons including wakefields are described. Simulations of the effects of geometric wakefields in the small-aperture FEL undulator are shown, as well as further simulations on potential FEL experiments using chirped beams. We also present the results of simulations on post-FEL diagnostics.

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THPRO031

Short Pulses THz FEL for the Oxford Accelerator Science Laboratory

2934

T. Chanwattana, R. Bartolini, A. Seryi
JAI, Oxford, United Kingdom
R. Bartolini
DLS, Oxfordshire, United Kingdom
E. Tsesmelis
CERN, Geneva, Switzerland

The Accelerator Science Laboratory (ASL) is under development at the John Adams Institute in Oxford with the aim of fostering advanced accelerator concepts and applications. The option to install a short pulse THz FEL based on a conventional RF accelerator driven by a RF photocathode gun is being investigated. This report presents the concept of the facility, the accelerator physics and FEL studies and engineering integration in the University physics department.

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THPRO032

Studies on LPWA-based Light Sources driven by a Transverse Gradient Undulator

2937

SUSPSNE008

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T. Chanwattana, R. Bartolini, A. Seryi
JAI, Oxford, United Kingdom
R. Bartolini
DLS, Oxfordshire, United Kingdom

The Accelerator Science Laboratory (ASL) is under development at the John Adams Institute in Oxford with the aim of fostering advanced accelerator concepts and applications. The option to install a LPWA based light source driven by a transverse gradient undulator is being investigated. This report presents the accelerator physics, FEL studies and the performance expected from such a facility.

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THPRO033

Electron-bunch Shaping for Coherent Compton Scattering

4107

SUSPSNE010

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J.E. Thorne, P. Piot, I. Viti
Northern Illinois University, DeKalb, Illinois, USA
P. Piot
Fermilab, Batavia, Illinois, USA

Producing high-quality x rays could have important applications to high-precision medical imaging and national security. Inverse Compton scattering involving the head-on collision of a relativistic electron bunch with a high-power laser offers a viable path toward the realization of a compact x-ray source. A method consisting in reflecting a short-pulse laser onto a “relativistic mirror” (a moving thin sheet of electrons) has been proposed and recently demonstrated as a way to enhance the back-scattered photon flux by operating in the coherent regime. In this contribution we present particle-in-cell numerical simulations of the inverse Compton scattering process and especially investigate the impact of the laser-pulse and electron-beam distributions that could substantially improve the x-ray production via coherent emission.

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THPRO034

Design of the LCLS-II Electron Optics

2940

Y. Nosochkov, P. Emma, T.O. Raubenheimer, M. Woodley
SLAC, Menlo Park, California, USA

Funding: Work supported by the US Department of Energy Contract DE-AC02-76SF00515.
The LCLS-II project is a high repetition rate, high average brightness free-electron laser based on the existing facilities at the SLAC National Accelerator Laboratory. The LCLS-II will be driven by a new CW superconducting RF (SCRF) 4-GeV linac replacing the existing Cu-linac in the 1st km of the linac tunnel. The SCRF linac will include chicanes for providing full compression of the electron bunch length. After the linac, the electron beam will be directed into the existing 2-km bypass line connecting to the Beam Switch Yard (BSY), where a new spreader system will allow a high rate bunch-by-bunch deflection into the hard X-ray (HXR) or soft X-ray (SXR) transport lines, or towards the BSY high power dump. The HXR line will include a new variable gap undulator replacing the existing LCLS-I undulator and will reuse the existing LCLS-I linac-to-undulator and dump transport lines. The SXR will require a new transport line sharing the same tunnel with the HXR and will include a new variable gap undulator. Overview of the electron beam transport and the optics design are presented.

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THPRO035

Improving and Maintaining FEL Beam Stability of the LCLS

2943

F.-J. Decker, A.L. Benwell, W.S. Colocho, Z. Huang, A. Krasnykh, J.R. Lewandowski, T.J. Maxwell, J. Sheppard, J.L. Turner
SLAC, Menlo Park, California, USA

Funding: *Work supported by U.S. Department of Energy, Contract DE-AC02-76SF00515.
The beam stability of the Linac Coherent Light Source (LCLS) has seen many improvements over the years and has matured to a state where progress is slow and maintaining the best stability is becoming the main challenge. Single sources which are identified by various means contribute to only about 10 to 20% of the whole jitter power, meaning that their elimination gives only a small improvement of 5 to 10%. New sources need to be identified fast. Especially slow variations of a few seconds to minutes time scale are often hidden and partially corrected by feedback systems. A few episodes of increased jitter have shown the limitations of some of the feedback systems. Stability for all dimensions, transverse, longitudinal, and intensity are presented.

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THPRO038

Energy-Silenced HGHG

2946

E. Hemsing, G. Marcus, A. Marinelli
SLAC, Menlo Park, California, USA
D. Xiang
Shanghai Jiao Tong University, Shanghai, People's Republic of China

We study the effect of longitudinal space charge on the correlated energy spread of a relativistic beam that has been microbunched for the emission of high harmonic radiation. We show that, in the case of microbunching induced by a laser modulator followed by a dispersive chicane, longitudinal space charge forces can act to significantly reduce the induced energy spread of the beam without a reduction in the harmonic bunching content. This effect may significantly relax constraints on the harmonic number achievable in HGHG FELs, which are otherwise limited by the induced energy spread from the laser.

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THPRO039

Model-independent Description of Shot-noise, Amplification and Saturation

2949

Y.C. Jing, V. Litvinenko, G. Wang
BNL, Upton, Long Island, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
High-gain FEL is one of many electron-beam instabilities, which have a number of common features linking the shot noise, the amplification and the saturation. In this paper we present a new, model-independent description of the interplay between these effects and derivation of a simple formula determining the saturation and maximum attainable gain in such instabilities. Application of this model-independent formula to FEL is compared with FEL theory and simulations. We describe limitations resulting from these finding for FEL amplifiers used for seeded FELs and for Coherent electron Cooling.

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THPRO050

Study of a THz/VUV Free Electron Laser Facility in Taiwan

2980

N.Y. Huang, M.C. Chou, C.-S. Hwang, W.K. Lau, A.P. Lee
NSRRC, Hsinchu, Taiwan
A. Chao, J. Wu
SLAC, Menlo Park, California, USA
C.H. Chen, Y.-C. Huang
NTHU, Hsinchu, Taiwan
X.M. Yang
DICP, Dalian, People's Republic of China

A free electron laser (FEL) facility aimed for VUV and THz radiation is being studied at National Synchrotron Radiation Research Center (NSRRC) in Taiwan. Strong consideration has been given to minimize the cost by making maximum use of existing hardware at NSRRC. One unique consideration is to use an existing undulator for the dual functions of the THz radiator and the modulator of a HGHG section. Design emphasizes versatility of operation and beam quality control and compensation of nonlinearities, with a vision that it will allow as much as possible future upgrades as well as later R&D of FEL physics. The polarization control of the THz radiation provides novel application for the users. The facility is to be housed in the existing 38-m by 5-m tunnel of the TPS Linac Test Laboratory.

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THPME081

Plans for an Australian XFEL Using a CLIC X-band Linac

3424

M.J. Boland, T.K. Charles, R.T. Dowd, G. LeBlanc, Y.E. Tan, K.P. Wootton, D. Zhu
SLSA, Clayton, Australia
R. Corsini, A. Grudiev, A. Latina, D. Schulte, S. Stapnes, I. Syratchev, W. Wuensch
CERN, Geneva, Switzerland

Preliminary plans are presented for a sub-Angstrom wavelength XFEL at the Australian Synchrotron light source site. The design is based around a 6 GeV x-band linac from the CLIC Project. One of the motivations for the design is to have an XFEL co-located on the site with existing storage ring based synchrotron light source. The desire and ability of the Australian photon science community to win beamtime on existing XFELs has lead to this design study to plan for a future machine in Australia. The technology choice is also driven by the Australian participation in the CLIC Collaboration and the local HEP community.

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THPRI074

Colorado State University (CSU) Accelerator and FEL Facility

3937

S. Biedron, C. Carrico, A. D'Audney, J.P. Edelen, J. Einstein, C.C. Hall, J.R. Harris, K. Horovitz, J. Martinez, S.V. Milton, A.L. Morin, N. Sipahi, T. Sipahi, J.E. Williams, P.J.M. van der Slot
CSU, Fort Collins, Colorado, USA
P.J.M. van der Slot
Mesa+, Enschede, The Netherlands
P.J.M. van der Slot
Twente University, Laser Physics and Non-Linear Optics Group, Enschede, The Netherlands

The Colorado State University (CSU) Accelerator Facility will include a 6-MeV L-Band electron linear accelerator (linac) with a free-electron laser (FEL) system capable of producing Terahertz (THz) radiation, a laser laboratory, a microwave test stand, and a magnetic test stand. The photocathode drive linac will be used in conjunction with a hybrid undulator capable of producing THz radiation. Details of the systems used in CSU Accelerator Facility are discussed.

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THPRI101

Coupler Kick and Cavity Tilt Effects on Emittance Preservation in Linear Accelerators

4013

A.V. Tsakanian, G.A. Amatuni, B. Grigoryan, I.N. Margaryan, V.M. Tsakanov
CANDLE SRI, Yerevan, Armenia

The effects of the coupler kick and the cavity tilts on the beam dynamics in long linear accelerator are studied. The dispersive and wakefield caused beam emittance dilution are evaluated analytically using two particle model of the beam. The numerical simulations for the European XFEL project are presented.

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