IPAC2017 - List of Keywords (FEL)

Paper	Title	Other Keywords	Page
MOPAB047	Electron Beam Phase Space Tomography at the European XFEL Injector	emittance, electron, quadrupole, optics	196
	M. Scholz, B. Beutner DESY, Hamburg, Germany
	The FEL process is determined by the 6D phase space distribution of relativistic electron bunches. Experimental reconstructions of these distributions are therefore a step foreward to understand the beam dynamics and to optimize FEL operation. The reconstructions of the transverse phase spaces can be acieved with tomographic methods. In the injector of the European XFEL, measurements for the reconstruction of the phase spaces were carried out using phase advance scans with multiple quadrupoles. The beam sizes were kept optimized at the measurement screen. A transversely deflecting cavity (TDS) was used to streak the beam vertically. That allows to do longitudinally slice resolved measurements of the horizontal phase space. The horizontal streak required for the slice measurements in the vertical plane was achieved with a correlated linear energy spread and dispersion. In this paper, we present measurement results showing longitudinal slice resolved reconstructions of the transverse phase spaces taken in the European XFEL injector.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB047
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MOPAB073	Measurement of Electron-Bunch Length Using Coherent Radiation in Infrared Free-Electron Laser Facilities	electron, detector, radiation, laser	288
	N. Sei, H. Ogawa AIST, Tsukuba, Ibaraki, Japan K. Hayakawa, Y. Hayakawa, K. Nogami, T. Sakai, T. Tanaka LEBRA, Funabashi, Japan H. Ohgaki, H. Zen Kyoto University, Kyoto, Japan
	Funding: This study was financially supported by JSPS KAKENHI Grant Number JP16H03912. We have studied techniques evaluating bunch length of micropulses in an electron beam. The bunch length of the electron beam is an important parameter for free-electron laser (FEL) facilities with linear accelerators. In order to obtain high FEL gain at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University and at Kyoto University Free Electron Laser (KU-FEL), the electron-bunch length is compressed to less than 1 ps in their undulator sections. Using the compressed electron beams, intense terahertz lights were generated by coherent radiation. The power of the coherent radiation was more than 50 micro-joule per electron-beam macropulse. We can extract the information of the bunch length of the electron-beam micropulse from the intense coherent radiation by using narrow-band diode detectors. In this presentation, experimental results of the measurements of the root-mean-square electron-bunch length using the coherent radiation at LEBRA* and KU-FEL** will be reported. : N. Sei et al., J. Opt. Soc. Am. B, 31, 2150 (2014). *: N. Sei et al., Nucl. Instrum. Methods Phys. Res., Sect. A, 832, 208 (2016).
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MOPAB082	Design and Simulation of High Order Mode Cavity Bunch Length Monitor for Infrared Free Electron Laser	cavity, simulation, laser, electron	309
	Q. Wang, X.Y. Liu, P. Lu, Q. Luo, B.G. Sun, L.L. Tang, J.H. Wei, F.F. Wu, Y.L. Yang, T.Y. Zhou, Z.R. Zhou USTC/NSRL, Hefei, Anhui, People's Republic of China
	Funding: Supported by The National Key Research and Development Program of China (2016YFA0401900, 2016YFA0401903); NSFC (11375178, 11575181); the Fundamental Research Funds for the Central Universities (WK2310000046) A bunch length monitor using resonant cavity has been designed for the NSRL Infrared Free Electron Laser (IR-FEL) facility. To avoid the restriction of working fre-quency caused by the beam pipe radius, the high order modes of the harmonic cavities are utilized. The position and orientation of coaxial probes are optimized to avoid interference modes which come from the cavity and beam tube according to the analysis formula of electro-magnetic field distribution. Based on the parameters of IR-FEL, a simulation is performed to verify the feasibility of the bunch length monitor. The simulation result shows that the design meets the requirements of IR-FEL, and the resolution can be better than 50 fs.
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MOPAB083	The New Beam Current Transformer for IR-FEL Facility at NSRL *	diagnostics, electron, induction, electronics	312
	J.H. Wei, H. Li, X.Y. Liu, P. Lu, B.G. Sun, J.G. Wang, Q. Wang, F.F. Wu, Y.L. Yang, T.Y. Zhou USTC/NSRL, Hefei, Anhui, People's Republic of China
	Funding: Supported by The National Science Foundation of China (Grant No. 11575181) The beam current transformer (CT) is an important part of the beam diagnostics system as a kind of non-destructive intensity measurement. The beam CT has the strong dependence of the sensitivity and time constant on the time structure of the beam. To measure the macro-pulse beam intensity with 5-10 's length and 238 MHzμpulse repetition rate in the IR-FEL, it is necessary to find a suitable material as the CT core which can meet the measure requirement of the beam current. In this paper, three different magnetic materials were tested to find out that the laminated amorphous core owned the best performance, meanwhile, the mechanical structure was designed. The finished product passed the acceptance test.
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MOPAB095	Development of the Simulation Software Package for the CBPM System	simulation, cavity, network, experiment	349
	J. Chen, L.W. Lai, Y.B. Leng, L.Y. Yu SINAP, Shanghai, People's Republic of China N. Zhang SSRF, Shanghai, People's Republic of China
	In recent years, the development and construction of Free Electron Laser (FEL) facilities are in full swing. For FEL facilities, to generate coherent X-ray, cavity beam position monitor (CBPM) system which consist of cavity BPM, RF front-end and signal processor are employed to measure the transverse position in the undulator section. A generic simulation software package, with the S21 parameters of the real components, for the design of the RF front-end and the optimize of the CBPM system was developed. In this paper, the development of the generic simulation software package, and the experiment results with beam at Shanghai Deep ultraviolet (SDUV) FEL facility to verify the correctness of the simulation soft package will be introduced. The application in the design and optimize of the RF front-end for the Dalian Coherent Source (DCLS) will be addressed as well .
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MOPAB149	Design of LCLS-II ATCA BPM System	linac, network, undulator, controls	477
	A. Young, R. Claus, J.M. D'Ewart, J.C. Frisch, G. Haller, R.T. Herbst, S. L. Hoobler, U. Legat, J.J. Olsen, R. Ruckman, L. Sapozhnikov, S.R. Smith, T. Straumann, J.A. Vásquez, M. Weaver, E. Williams, C. Xu SLAC, Menlo Park, California, USA
	Funding: Work supported by U.S. Department of Energy under Contract Numbers DE-AC02-06CH11357 SLAC's LCLS-II is a next generation X-ray FEL that will use a CW 4 GeV superconducting linac with nominal bunch spacing of 1us will deliver both soft and hard x-ray FEL to users. In order to achieve the required performance, the SLAC Technical Innovation Directorate has developed a common hardware and firmware platform for beam instrumentation based on the ATCA crate format. We have designed a stripline and cavity BPM system based on this platform that is capable of measuring the beam position at full beam rate. The system will have a dynamic range between 1 pC to 300 pC. This paper will discuss the design of the BPM electronics, overall architecture and performance on LCLS-I.
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MOPIK070	Notes on Relations between Slice and Projected Beam Parameters	emittance, betatron	689
	V. Balandin, N. Golubeva DESY, Hamburg, Germany
	We consider some aspects of the relations between slice and projected beam parameters.
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MOPIK078	Narrow-Band, Wide-Range Tuneable THz Source Based on the Slotted-Foil Technique	undulator, electron, radiation, simulation	712
	J. Pfingstner, E. Adli, H. Holmestad University of Oslo, Oslo, Norway S. Bettoni, S. Reiche PSI, Villigen PSI, Switzerland
	The FEL user community has expressed a strong interest in a THz source for the excitation of their samples in pump probe experiments. The demanded THz properties are challenging to achieve, as they include a narrow bandwidth of <5-10%, the possibility of frequency tuning between 1 and 20 THz, a THz pulse energy of about 100 uJ, and a fixed phase relation from shot-to-shot. To fulfil these specifications, an accelerator-based source is proposed in this paper. It utilises the slotted-foil technique to create a pre-bunched electron beam that is injected into a helical undulator. Detailed simulation studies presented in this paper show that the corresponding undulator radiation has the demanded properties.
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MOPVA020	S2E Simulation of an ERL-Based High-Power EUV-FEL Source for Lithography	linac, electron, simulation, injection	894
	N. Nakamura, R. Kato, T. Miyajima, M. Shimada KEK, Ibaraki, Japan R. Hajima QST, Tokai, Japan T. Hotei Sokendai, Ibaraki, Japan
	An energy recovery linac(ERL)-based free electron laser(FEL) is a possible candidate of a high-power EUV source for lithography. The ERL can provide a high-current and high-quality electron beam for the high-power FEL and also greatly reduce the dumped beam power and activation compared to ordinary linacs. An ERL-based EUV-FEL source has been designed using available technologies and resources. For this design, we perform Start-to-End(S2E) simulation from the electron gun to the exit of the decelerating main linac to track the electron beam parameters and to evaluate the FEL performance. The electron bunches from the injector are off-crest accelerated to 800 MeV and compressed in the 1st arc and/or chicane to obtain a high-peak current for high FEL output. After the undulator section for SASE FEL, they are decompressed in the 2nd arc and then decelerated in the main linac to optimize the energy spread or the energy recovery efficiency. This paper will present the S2E simulation for the designed EUV-FEL source. N. Nakamura et al., Proc. of ERL2015, Stony Brook, NY, USA, pp.4-9.
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MOPVA127	Vertical Test Results for the LCLS-II 1.3 GHz First Article Cavities	cavity, cryomodule, SRF, linac	1152
	A. Burrill, D. Gonnella, M.C. Ross SLAC, Menlo Park, California, USA G.K. Davis, A.D. Palczewski, L. Zhao JLab, Newport News, Virginia, USA A. Grassellino, O.S. Melnychuk Fermilab, Batavia, Illinois, USA
	The LCLS-II project requires 35 1.3 GHz cryomodules to be installed in the accelerator in order to deliver a 4 GeV electron beam to the undulators hall. These 35 cryomodules will consist of 8 1.3 GHz TESLA style SRF cavities, a design most recently used for the XFEL project in Hamburg, Germany. The cavity design has remained largely unchanged, but the cavity treatment has been modified to utilize the nitrogen doping process to allow for Quality factors in excess of 3x10¹⁰ at 16 MV/m, the designed operating gradient of the cavities in the CM. Two industrialized vendors are producing most of the SRF cavities for these cryomodules; and the performance of the first article cavities, 16 from each vendor, will be reported on in this paper.
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TUOAA2	A Soft X-Ray Free-Electron Laser Beamline of SACLA	electron, undulator, photon, laser	1209
	K. Togawa, T. Asaka, N. Azumi, T. Hara, T. Hasegawa, N. Hosoda, T. Inagaki, T. Ishikawa, R. Kinjo, C. Kondo, H. Maesaka, S. Matsui, T. Ohshima, Y. Otake, S. Owada, H. Tanaka, T. Tanaka, M. Yabashi RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan T. Bizen, H. Kimura, S. Matsubara, K. Nakajima, T. Sakurai, T. Togashi, K. Tono JASRI/SPring-8, Hyogo, Japan T. Fukui RIKEN SPring-8 Center, Innovative Light Sources Division, Hyogo, Japan
	At the Japanese x-ray free-electron laser (FEL) facility, SACLA, the beamline-1 has been upgraded from a spontaneous radiation to a soft x-ray FEL beamline, which generates FEL lights over a wide wavelength range from the extreme-ultraviolet to the soft x-ray regions. We started operation for users in July 2016. A dedicated accelerator, which is a refinement of the SCSS test accelerator operated in 2005-2013, was installed beside the XFEL beamlines in the SACLA undulator hall. The SCSS concept to make an FEL facility compact was continuously adopted. In the 2016 summer shutdown period, the beam energy was upgraded from 500 MeV to 800 MeV by adding two C-band rf units. The maximum K-value of the undulator magnet is 2.1. The available wavelengths of the FEL lights were extended to the range from 8 to 50 nm with pulse energies between a few to few tensμJ at an operational repetition rate of 60 Hz. In this conference, we will report an overview of the upgraded SACLA-beamline-1 and characteristics of the FEL light pulse.
	Slides TUOAA2 [15.457 MB]
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TUPAB020	AREAL 50 MeV Electron Accelerator Project for THz and Middle IR FEL	radiation, electron, emittance, gun	1355
	G.A. Amatuni, Z.G. Amirkhanyan, V.S. Avagyan, A. Azatyan, V. Danielyan, H. Davtyan, S.G. Dekhtiarov, N. Ghazaryan, B. Grigoryan, L. Hakobyan, M. Ivanyan, V.G. Khachatryan, E.M. Laziev, T. Markosyan, N. Martirosyan, Sh.A. Mehrabyan, T. Melkumyan, T.H. Mkrtchyan, V.H. Petrosyan, V. Sahakyan, A. Sargsyan, A.S. Simonyan, A.V. Tsakanian, V.M. Tsakanov, A. Vardanyan, Ta.S. Vardanyan, T.L. Vardanyan, V. V. Vardanyan, A.S. Yeremyan, G.S. Zanyan CANDLE SRI, Yerevan, Armenia P.S. Manukyan SEUA, Yerevan, Armenia A.V. Tsakanian HZB, Berlin, Germany
	Advanced Research Electron Accelerator Laboratory (AREAL) is an electron accelerator project based on photo cathode RF gun. First phase of the facility is a 5 MeV energy RF photogun, which is currently under operation. The facility development implies energy upgrade to 50 MeV with further delivery of the electron beam to the undulator sections for Free Electron Laser and coherent undulator radiation generation in MIR and THz frequency ranges respectively. In this report the design study of AREAL 50 MeV facility main systems along with the beam dynamics and characteristics of expected radiation are presented.
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TUPAB049	Development of the High Power Terahertz Light Sources at LEBRA Linac in Nihon University	target, electron, radiation, linac	1437
	T. Sakai, K. Hayakawa, Y. Hayakawa, K. Nogami, T. Tanaka LEBRA, Funabashi, Japan H. Ogawa, N. Sei AIST, Tsukuba, Ibaraki, Japan
	Funding: This work was supported by JSPS KAKENHI (Grant-in-Aid for Young Scientists (B)) Grant Number JP16K17539. Development of a THz light source has been underway at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University in collaboration with National Institute of Advanced Industrial Science and Technology (AIST) since 2011. Basic research on coherent transition radiation (CTR) in the THz region has been carried out using the Parametric X-ray Radiation (PXR)-beam line of LEBRA. Since fiscal year 2016, the THz transport line has been constructed on the same axis as the PXR beam line taking the construction cost and simultaneous use of the two beams into account. Basic measurement and intensity upgrading test have been carried out for the THz lights generated on the PXR-generating electron beam line. The average intensity of the THz lights obtained at the output port in the accelerator room has been 5 mW. Construction of the THz transport beam line and the property of the THz lights is discussed in the report.
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TUPAB083	Commissioning Experience and Beam Optimization for DCLS Linac	linac, gun, emittance, cathode	1509
	M. Zhang, D. Gu, Q. Gu, D. Huang, Z. Wang SINAP, Shanghai, People's Republic of China
	Dalian Coherent Light Source (DCLS), which will focus on the Physical Chemistry with time-resolved pump-probe experiments and EUV absorption spectroscopy techniques, is the first high gain FEL user facility in China. The 300MeV linac consists of a laser-driven rf-gun followed by 7 Sband accelerating tubes. A magnetic chicane is adopted to get the desired 300A peak current. After 5 months component installation, first photoelectrons were generated on 17 August 2016. In this paper, we give a summary of the commissioning experience and the beam parameters measurements. In addition, beam jitter sources are studied based on real machine performances.
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TUPAB084	Beam Stability Modeling and Jitter Control for SXFEL Linac	linac, controls, quadrupole, klystron	1513
	M. Zhang, R.B. Deng, D. Gu, Q. Gu, D. Huang, Z. Wang SINAP, Shanghai, People's Republic of China
	FEL operations foresee stringent requirements for the stability of the global linac output parameters and this requirement is particularly stringent for the successful operation of an externally seeded FEL. In order to understand the sensitivity of these parameters to jitters of various error sources along the SXFEL linac, studies have been performed based on analytical methods and tracking code simulations. Using the tolerance budget as guidance, beam jitter control techniques are discussed on the view of the beam dynamics.
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TUPAB086	Design Study of a High-Intensity, Low-Energy Electron Gun	gun, electron, simulation, emittance	1517
	Q. Zhang, K. Fan, T. Hu, K.F. Liu, Z.Y. Mei HUST, Wuhan, People's Republic of China
	An independently-tunable-cells thermionic RF gun (ITC-RF gun) is adopted in a compact FEL-THz facility due to its compactness, low-cost and high intensity. An electron gun is required to generate maximum beam current of 3.2 A at low energy of 15keV for the ITC-RF gun, which creates difficulties for the design of electron gun because of the strong space charge effect. A double-anode gridded gun structure is adopted that controls the beam current easily while maintains the energy dispersion less than 0.5%, with high perveance and high compression ratio. CST code has been used extensively for design optimization, which includes electrode shape, influences of grid, installation errors. A measurement scheme is also proposed for key parameters verification. Beam current, emittance and energy dispersion can be measured.
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TUPAB111	Energy Distribution and Work Function Measurements for Metal Photocathodes with Measured Levels of Surface Roughness	emittance, electron, detector, plasma	1580
	L.B. Jones, T.S. Beaver, B.L. Militsyn, T.C.Q. Noakes, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom S. Mistry STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom S. Mistry Loughborough University, Leicestershre, United Kingdom
	Funding: The work is part of EuCARD-2, partly funded by the European Commission, GA 312453. The minimum achievable emittance in an electron accelerator depends strongly on the intrinsic emittance of the photocathode electron source which is measureable as the mean longitudinal and transverse energy spreads in the photoemitted electrons. Reducing emittance in an accelerator driving a Free Electron Laser (FEL) delivers significant reduction in the saturation length for an x-ray FEL, reducing machine cost and increasing x-ray beam brightness. There are many parameters which affect the intrinsic emittance of a photocathode. Surface roughness is a significant factor, and consequently the development of techniques to manufacture low roughness photocathodes with optimum emission properties is a priority for the electron source community. In this work, we present transverse energy distribution and work function measurements made using our TESS facility* for electrons emitted from copper and molybdenum photocathodes with differing levels of measured surface roughness. * Proc. FEL '06, THPPH013, 583-586 ** Proc. FEL '13, TUPPS033, 290-293
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TUPAB123	Hard X-Ray and Soft X-Ray Undulator Segments for the Linear Coherent Light Source Upgrade (LCLS-II) Project	undulator, linac, photon, electron	1605
	M. Leitner, D. Arbelaez, A.J. Band, D. Bianculli, A.P. Brown, J.N. Corlett, A.J. DeMello, J.R. Dougherty, L. Garcia Fajardo, K. Hanzel, M. Hoyt, D.E. Humphries, D. Jacobs, C. Joiner, J.-Y. Jung, D. Leitner, S. Marks, K.A. McCombs, D.V. Munson, K.L. Ray, D.A. Sadlier, J.J. Savino, D. Schlueter, E.J. Wallén, V. Waring, A. Zikmund LBNL, Berkeley, California, USA C.J. Andrews, D.E. Bruch, A.L. Callen, G. Janša, S. Jansson, K.R. Lauer, Yu.I. Levashov, D.S. Martinez-Galarce, B.D. McKee, H.-D. Nuhn, Â. Oven, M. Rowen, Z.R. Wolf SLAC, Menlo Park, California, USA
	Funding: Work supported by the Director Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Stanford Linear Accelerator Laboratory is currently constructing the Linear Coherent Light Source II (LCLS-II), a free-electron laser (FEL) which will deliver x-rays at an energy range between 0.2 keV and 5 keV at high repetition rate of up to ~1 MHz using a new 4 GeV superconducting RF linac, and at and an energy range between 1 keV and 25 keV when driven by an existing copper linac at up to 120 Hz repetition rate. To cover the full photon energy range, LCLS-II includes two variable-gap, hybrid-permanent-magnet undulator lines: A soft x-ray undulator (SXR) line with 21 undulator segments optimized for a photon energy range from 0.2 keV to 1.3 keV plus a hard x-ray undulator (HXR) line with 32 undulator segments designed for a photon energy range from 1.0 keV to 25.0 keV. Lawrence Berkeley National Laboratory is responsible for fabricating the 53 undulator segments. This paper summarizes the main parameters and design attributes for both LCLS-II undulator segment types.
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TUPAB130	Status of the LCLS-II Superconducting RF Linac	cryomodule, cavity, linac, operation	1630
	A. Burrill SLAC, Menlo Park, California, USA
	The LCLS-II project requires the assembly and installation of 37 cryomodules in order to deliver a 4 GeV electron beam to the undulators to produce both soft and hard x-ray pulses at a repetition rate up to 1 MHz. All of the cryomodules will operate in continuous wave mode, with 35 operating at 1.3 GHz for acceleration and 2 operating at 3.9 GHz to linearize the longitudinal beam profile. The assembly and testing of the 1.3 GHz cryomodules is well underway and the 3.9 GHz cryomodule work is entering into the pre-cryomodule testing and component validation phase. Both of these efforts will be reported on in this paper.
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TUPAB135	A 1.75 mm Period RF-Driven Undulator	undulator, laser, electron, cavity	1643
	F. Toufexis, S.G. Tantawi SLAC, Menlo Park, California, USA
	Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515, and the National Science Foundation under Contract No. PHY-1415437. To reduce the linac energy, and hence the size required for a Free Electron Laser radiating at a given wavelength, a smaller undulator period with sufficient field strength is needed. Previous work from our group successfully demonstrated a microwave undulator at 11.424 GHz using a corrugated cylindrical waveguide operating in the HE11 mode. Scaling down the undulator period using this technology poses the challenge of confining and coupling* the electromagnetic fields while maintaining over-moded features for power handling capability and electron beam wakefield mitigation. In this work, we present a novel end section of an RF undulator at 91.392 GHz. To confine the fields inside the undulator, a corrugated waveguide is connected through a matching section to a linear taper and a mirror. After the mirror, a Bragg reflector and a matching section are used to reflect back all the fields leaking out of the mirror opening. * F. Toufexis, J. Neilson, and S.G. Tantawi, Coupling and Polarization Control in a mm-wave Undulator, these proceedings.
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TUPAB137	Evaluation of FEL Performance with a Longer Injector Drive Laser Pulse at the LCLS	laser, emittance, electron, simulation	1651
	F. Zhou, Y. Ding, J.P. Duris, S. Gilevich, P. Hering, S. Vetter SLAC, Menlo Park, California, USA
	Funding: US DOE under grant No. DE-AC02-76SF00515. It is known that the X-ray Free Electron Laser (FEL) performance strongly depends on the beam emittance and peak current. Lengthening injector laser pulse can improve the injector emittance but the injector peak current is notably compromised, in comparison to nominal laser pulse. With this longer laser pulse, a stronger bunch compression through downstream bunch compressors is thus required to keep same final peak current as the nominal laser pulse mode. This process may cause stronger micro-bunching effect. At the LCLS, we perform preliminary experiments with doubling injector laser pulse. In this paper, we present the experimental results of the injector emittance, microbunching effects and FEL performance with the longer drive laser pulse.
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TUPIK003	Electron Transport on COXINEL Beam Line	electron, laser, undulator, free-electron-laser	1688
	T. André, I.A. Andriyash, F. Blache, F. Bouvet, F. Briquez, M.-E. Couprie, Y. Dietrich, J.P. Duval, M. El Ajjouri, A.M. Ghaith, C. Herbeaux, N. Hubert, M. Khojoyan, M. Labat, N. Leclercq, A. Lestrade, A. Loulergue, O. Marcouillé, F. Marteau, P. N'gotta, P. Rommeluère, K.T. Tavakoli, M. Valléau SOLEIL, Gif-sur-Yvette, France S. Bielawski, C. Evain, C. Szwaj PhLAM/CERLA, Villeneuve d'Ascq, France S. Corde, J. Gautier, J.-P. Goddet, G. Lambert, B. Mahieu, V. Malka, S. Smartzev, C. Thaury LOA, Palaiseau, France E. Roussel Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	COXINEL experiment aims at demonstrating free electron laser (FEL) amplification with a laser plasma accelerator (LPA). For COXINEL, a dedicated 8 m transport line has been designed and prepared at SOLEIL. We present here LPA beam transport results around 180 MeV through this line. Different electron beam optics were applied.
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TUPIK108	Beam Based Alignment Studies for the CLARA FEL Test Facility	quadrupole, alignment, undulator, cavity	1971
	J.K. Jones, N. Thompson STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	The CLARA (Compact Linear Accelerator for Research and Applications) test facility is designed to experimentally demonstrate innovative FEL schemes for future light source applications. Such schemes can place strict requirements on the accelerator beam properties as well as the relative alignment of the beam in the FEL radiators and modulators. Beam-based alignment (BBA) of the FEL section is therefore an operational requirement for all advanced FEL facilities. In this paper we demonstrate results of CLARA BBA simulations, and also report initial simulation results from the use of non-linear algorithms to optimise the FEL performance directly.
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TUPIK121	Dark Sector Experiments at LCLS-II (DASEL) Accelerator Design	kicker, experiment, laser, septum	2008
	Y.M. Nosochkov, T.G. Beukers, A.R. Fry, C. Hast, T.W. Markiewicz, T.K. Nelson, N. Phinney, T.O. Raubenheimer, P.C. Schuster, N. Toro SLAC, Menlo Park, California, USA
	Funding: Work supported by the US DOE Contract DE-AC02-76SF00515. DASEL (Dark Sector Experiments at LCLS-II) is a new accelerator and detector facility proposed to be built at SLAC. Its primary target is a direct observation of dark matter produced in electron-nuclear fixed-target collisions. DASEL takes advantage of the LCLS-II free electron laser (FEL) under construction at SLAC which will deliver a continuous electron beam from a 4-GeV superconducting linac. DASEL will operate parasitically to the LCLS-II FEL by extracting low intensity unused dark current bunches downstream of the FEL kickers. The DASEL key accelerator components include a 46-MHz gun laser system providing controlled intensity and timing of the dark current, a fast (MHz) kicker with 600-ns flat-top, a new transport line connecting the LCLS-II to the existing A-line and to End Station-A where the experiments will take place, and a spoiler and collimator system in the A-line for final shaping of the DASEL beam. An overview of the DASEL accelerator system is presented.
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TUPVA154	Project-Based Cooperative Learning in Accelerator Science and Technology Education	dipole, feedback, quadrupole, cavity	2458
	G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom R.B. Appleby, G.X. Xia UMAN, Manchester, United Kingdom I.R. Bailey Lancaster University, Lancaster, United Kingdom J.A. Clarke, O.B. Malyshev, N. Marks, B.D. Muratori, M.W. Poole, Y.M. Saveliev, B.J.A. Shepherd STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom C.P. Welsch, A. Wolski The University of Liverpool, Liverpool, United Kingdom
	Funding: The work is funded by STFC via the Cockcroft Institute core grant. The next generation of particle accelerators will require the training of greater numbers of specialist accelerator physicists and engineers . These physicists and engineers should have a broad understanding of accelerator physics as well as the technology used in particle accelerators as well as a specialist in some area of accelerator science and technology . Such specialists can be trained by combining a University based PhD, in collaboration with national laboratory training with a broad taught accelerator lecture program. In order to have a faster start we decided to run an intensive two week school to replace the basic course at the Cockcroft Institute. At the same time we decided to investigate the use of problem based learning to simulate the way accelerator science tends to work in practice. In this exercise he students worked in groups of 5 to design a 3rd generation light source from scratch based on photon light specifications. In comparison to similar design exercises we stipulate that all students must do all parts and students are not allowed to specialise. A comparison with a standard lecture based education programme is discussed in this paper.
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WEOCA3	Status of the Development of Superconducting Undulators at the Advanced Photon Source	undulator, photon, vacuum, storage-ring	2499
	Y. Ivanyushenkov, C.L. Doose, J.F. Fuerst, E. Gluskin, Q.B. Hasse, M. Kasa, Y. Shiroyanagi ANL, Argonne, Illinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357 Superconducting planar undulator (SCU) technology has been developed and is currently in use at the Advanced Photon Source (APS). The experience of building and operating the first short-length, 16-mm period superconducting undulator, SCU0, paved the way for two 1-m long, 18-mm period devices, SCU18-1 and SCU18-2. The first of those undulators has been in operation since May 2015, while the second one replaced SCU0 in September 2016. The possibility of building planar SCUs with a high quality field has been demonstrated at the APS. The measured phase errors of SCU18-2 at the design operational current are only 2 degrees rms, for example. An FEL SCU prototype - a 1.5-m long, 21-mm period undulator - was also built and tested as part of an LCLS SCU R&D program. This undulator successfully achieved all LCLS-II undulator requirements including a phase error of 5 degrees rms. The superconducting undulator technology also allows the fabrication of circular polarizing devices. Currently, a new helical SCU is under construction at the APS. In addition, the concept of a novel Superconducting Arbitrarily Polarizing Emitter, or SCAPE, has been suggested and is now under development.
	Slides WEOCA3 [2.826 MB]
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WEPAB015	Parameter Optimization for Operation of sFLASH With Echo-Enabled Harmonic Generation	laser, electron, operation, bunching	2592
	J. Bödewadt, R.W. Aßmann, C. Lechner DESY, Hamburg, Germany W. Hillert, T. Plath, J. Roßbach University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany S. Khan, N.M. Lockmann DELTA, Dortmund, Germany
	The free-electron laser facility FLASH has a dedicated experimental setup for external FEL seeding applications for the XUV and soft x-ray spectral range. Recently the setup is operated as high-gain harmonic generation FEL. Furthermore, it also allows the operation of echo-enabled harmonic generation (EEHG). A versatile laser injection system allows operation with seed wavelength in the infra-red, visible, and ultra-violet. Here, we present the parameter optimization for operating the seeding setup with EEHG. First experimental tests are planned in the first half of 2017.
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WEPAB016	Experience in Operating sFLASH With High-Gain Harmonic Generation	laser, electron, radiation, photon	2596
	J. Bödewadt, R.W. Aßmann, N. Ekanayake, B. Faatz, I. Hartl, T. Laarmann, C. Lechner, M.M. Mohammad Kazemi, A. Przystawik DESY, Hamburg, Germany Ph. Amstutz, A. Azima, M. Drescher, W. Hillert, L.L. Lazzarino, Th. Maltezopoulos, V. Miltchev, T. Plath, J. Roßbach University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany K.E. Hacker, S. Khan, N.M. Lockmann, R. Molo DELTA, Dortmund, Germany
	sFLASH, the experimental setup for external seeding of free-electron lasers (FEL) at FLASH, has been operated in the high-gain harmonic generation (HGHG) mode. A detailed characterization of the laser-induced energy modulation, as well as the temporal characterization of the seeded FEL pulses is possible by using a transverse deflecting structure and an electron spectrometer. FEL saturation was reached for the 7th harmonic of the 266 nm seed laser. In this contribution, we present the latest experimental results.
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WEPAB017	Generation of Ultra-Short Electron Bunches and FEL Pulses and Characterization of Their Longitudinal Properties at FLASH2	electron, operation, laser, undulator	2600
	F. Christie, J. Rönsch-Schulenburg, S. Schreiber, M. Vogt DESY, Hamburg, Germany
	The free-electron laser in Hamburg (FLASH) is a user facility, delivering soft X-ray radiation, consisting of two beam lines, FLASH1 and FLASH2. The injector and the main linac are shared between both beam lines. Starting in 2014, FLASH2 has been commissioned for user operation. Currently, there is no hardware installed for the direct measurement of the electron bunch length nor the photon pulse duration at FLASH2. Exact knowledge of the pulse duration is essential for time-resolved user experiments performed at FLASH. Therefore, we are designing a modified beam line, containing a new type of X-band deflecting cavity* and a dipole, downstream of the FLASH2 undulator, to map the longitudinal phase space onto a beam screen. Anticipating the feasibility of measuring the longitudinal phase space with high resolution, a study on optimizing the free-electron laser (FEL) performance for shortest bunches is ongoing. *B. Marchetti et al., X-Band TDS project, contribution to these conference proceedings
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WEPAB019	Concept for a Seeded FEL at FLASH2	electron, laser, undulator, free-electron-laser	2607
	C. Lechner, R.W. Aßmann, J. Bödewadt, M. Dohlus, N. Ekanayake, B. Faatz, G. Feng, I. Hartl, T. Laarmann, T. Lang, L. Winkelmann, I. Zagorodnov DESY, Hamburg, Germany A. Azima, M. Drescher, Th. Maltezopoulos, T. Plath, J. Roßbach, W. Wurth University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany S. Khan DELTA, Dortmund, Germany
	The free-electron laser (FEL) FLASH is a user facility delivering photon pulses down to 4 nm wavelength. Recently, the second FEL undulator beamline 'FLASH2' was added to the facility. Operating in self-amplified spontaneous emission (SASE) mode, the exponential amplification process is initiated by shot noise of the electron bunch, resulting in photon pulses of limited temporal coherence. In seeded FELs, the FEL process is initiated by coherent seed radiation, improving the longitudinal coherence of the generated photon pulses. The conceptual design of a possible seeding option for the FLASH2 beamline foresees the installation of the hardware needed for high-gain harmonic generation (HGHG) seeding upstream of the already existing undulator system. In this contribution, we present the beamline design and numerical simulations of the seeded FEL.
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WEPAB021	Experience with Multi-Beam and Multi-Beamline FEL-Operation	laser, undulator, experiment, operation	2615
	J. Rönsch-Schulenburg, B. Faatz, K. Honkavaara, M. Kuhlmann, S. Schreiber, R. Treusch, M. Vogt DESY, Hamburg, Germany
	DESY's free-electron laser FLASH provides soft X-ray pulses for scientific users at wavelengths down to 4 nm simultaneously in two undulator beamlines. They are driven by a common linear superconducting accelerator with a beam energy of up to 1.25 GeV. The superconducting technology allows the acceleration of electron bunch trains of several hundred bunches with a spacing of 1 microsecond or more and a repetition rate of 10 Hz. A fast kicker-septum system directs one part of the bunch train to FLASH1 and the other part to FLASH2 keeping the full 10 Hz repetition rate for both. The unique setup of FLASH allows independent FEL pulse parameters for both beamlines. In April 2016, simultaneous operation of FLASH1 and FLASH2 for external users started. This paper reports on our operating experience with this type of multi-beam, multi-beamline set-up.
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WEPAB022	Background-free Harmonic Production in XFELs via a Reverse Undulator Taper	undulator, background, radiation, electron	2618
	E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	Nonlinear harmonics in X-ray FELs can be parasitically produced as soon as FEL reaches saturation, or can be radiated in dedicated afterburners. In both cases there is a strong background at the fundamental, since it is much stronger than harmonics. One can get around this problem by application of the recently proposed reverse undulator tapering. In this contribution we present numerical simulations of harmonic production in such a configuration as well as recent results from FLASH where the second and the third harmonics were efficiently generated with a low background at the fundamental. We also present the results for a high-contrast operation when the afterburner is tuned to the fundamental.
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WEPAB023	First Operation of a Harmonic Lasing Self-Seeded FEL	undulator, electron, operation, brightness	2621
	E. Schneidmiller, B. Faatz, M. Kuhlmann, J. Rönsch-Schulenburg, S. Schreiber, M. Tischer, M.V. Yurkov DESY, Hamburg, Germany
	Harmonic lasing is a perspective mode of operation of X-ray FEL user facilities that allows to provide brilliant beams of higher energy photons for user experiments. Another useful application of harmonic lasing is so called Harmonic Lasing Self-Seeded Free Electron Laser (HLSS FEL) that allows to improve spectral brightness of these facilities. In the past, harmonic lasing has been demonstrated in the FEL oscillators in infrared and visible wavelength ranges, but not in high-gain FELs and not at short wavelengths. In this paper we report on the first evidence of the harmonic lasing and the first operation of the HLSS FEL at the soft X-ray FEL user facility FLASH in the wavelength range between 4.5 nm and 15 nm. Spectral brightness was improved in comparison with Self-Amplified Spontaneous emission (SASE) FEL by a factor of six in the exponential gain regime. A better performance of HLSS FEL with respect to SASE FEL in the post-saturation regime with a tapered undulator was observed as well. The first demonstration of harmonic lasing in a high-gain FEL and at a short wavelength paves the way for a variety of applications of this new operation mode in X-ray FELs.
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WEPAB024	Commissioning and First Heating with the European XFEL Laser Heater	laser, undulator, electron, cathode	2625
	M. Hamberg Uppsala University, Uppsala, Sweden F. Brinker, M. Scholz DESY, Hamburg, Germany
	Funding: We thank DESY and Swedish research council under Project number DNR-828-2008-1093 for financial support. The Laser Heater of the European XFEL has been installed and commissioning is in progress. We discuss the setup and the results of the first electron beam heating in the injector section.
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WEPAB025	Status of the Soft X-Ray Free Electron Laser FLASH	laser, photon, experiment, operation	2628
	M. Vogt, B. Faatz, K. Honkavaara, M. Kuhlmann, J. Rönsch-Schulenburg, S. Schreiber, R. Treusch DESY, Hamburg, Germany
	The superconducting free-electron laser user facility FLASH at DESY in Hamburg, routinely produces several thousand photon pulses per second. The operational parameters cover a wavelength range from 90 nm down to 4 nm with pulse energies from several uJ up to 1 mJ and with pulse durations of several hundred fs down to a few fs. The FLASH injector and linac drives two undulator beam lines (FLASH1, FLASH2) and therefore FLASH is capable of serving 2 independent experiments with photon pulse (sub-) trains of several 100 bunches at the full train repetition frequency of 10 Hz. We summarize here the highlights of the user operation at FLASH1/2 and the study program (machine development and FEL optimization) of the FLASH facility.
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WEPAB027	Frequency Doubler and Two-color Mode of Operation at Free Electron Laser FLASH2	undulator, radiation, electron, operation	2635
	M. Kuhlmann, E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	We report on the results of the first operation of a frequency doubler at free electron laser FLASH2. The scheme uses the feature of the variable gap undulator. Undulator is divided in two parts. The second part of the undulator is tuned to the double frequency of the first part. Amplification process in the first undulator part is stopped at the onset of the nonlinear regime, such that nonlinear higher harmonic bunching in the electron beam density becomes pronouncing, but the radiation level is still small to disturb the electron beam significantly. Modulated electron beam enters the second part of the undulator and generates radiation at the 2nd harmonic. Frequency doubler allows operation in a two-color mode and operation at shorter wavelengths with respect to standard SASE scheme. Tuning of the electron beam trajectory, phase shifters and compression allows to tune intensities of the first and the second harmonic. The shortest wavelength of 3.1 nm (photon energy 400 eV) has been achieved with frequency doubler scheme, which is significantly below the design value for the standard SASE option.
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WEPAB029	Optimum Undulator Tapering of SASE FEL: From the Theory to Experiment	undulator, electron, radiation, laser	2639
	E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	Optimization of the amplification process in FEL amplifier with diffraction effects taken into account results in a specific law of the undulator tapering []. It is a smooth function with quadratic behavior in the beginning of the tapering section which transforms to a linear behavior for a long undulator. In practice, undulator consists of a sequence of modules of fixed length separated with intersections. Two modes of undulator tapering can be implemented: step tapering, and smooth tapering. Procedure of the step tapering applies step change of the undulator gap from module to module, and smooth tapering assumes additional linear change of the gap along each module. In this report we simulate the performance of the both experimental options and compare with theoretical limit. [] E.A. Schneidmiller and M.V. Yurkov, Optimization of a high efficiency free electron laser amplifier, Phys. Rev. ST Accel. Beams 18 (2015) 030705.
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WEPAB031	OCELOT as a Framework for Beam Dynamics Simulations of X-Ray Sources	simulation, wakefield, space-charge, electron	2642
	S.I. Tomin XFEL. EU, Hamburg, Germany I.V. Agapov, M. Dohlus, I. Zagorodnov DESY, Hamburg, Germany
	We describe the OCELOT open source project focusing on new beam dynamics simulation capabilities of the whole machine in modern electron-based x-ray sources. Numerical approaches for particle tracking and field calculations are discussed. In developing of the full-dimensional numerical modeling we pursue two important competitive aspects: the simulation has to be fast and has to include accurate estimations of collective effects. The simulation results for the European XFEL [1] are presented. The results have been benchmarked agains other codes and some of such benchmarks are shown.
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WEPAB033	Experimental Optimization and Characterization of Electron Beams for Generating IR/THz SASE FEL Radiation with PITZ	emittance, electron, simulation, radiation	2650
	P. Boonpornprasert, Y. Chen, J.D. Good, H. Huck, I.I. Isaev, D.K. Kalantaryan, M. Krasilnikov, X. Li, O. Lishilin, G. Loisch, D. Melkumyan, A. Oppelt, H.J. Qian, Y. Renier, T. Rublack, F. Stephan DESY Zeuthen, Zeuthen, Germany G. Asova INRNE, Sofia, Bulgaria C. Saisa-ard Chiang Mai University, Chiang Mai, Thailand Q.T. Zhao IMP/CAS, Lanzhou, People's Republic of China
	The Photo Injector Test facility at DESY, Zeuthen site (PITZ), develops high brightness electron sources for modern linac-based Free Electron Lasers (FELs). The PITZ accelerator can also be considered as a suitable machine for the development of an IR/THz source prototype for pump-probe experiments at the European XFEL. One of the interesting options for the IR/THz generation with PITZ is to generate the radiation by means of a SASE FEL using an uncompressed electron beam with bunch length of a few 10 ps and a peak current of ~200 A. In this paper, results of experimental optimizations and characterizations, including transverse phase space, slice transverse emittance and longitudinal phase space, of electron beams with bunch charges of 4 nC are presented and discussed. The measurements were done with beam momenta of 15 MeV/c and 22 MeV/c. Results of IR/THz SASE FEL calculations by using the GENESIS1.3 code based on the measured beam parameters are also presented and discussed.
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WEPAB034	Control of Seeded FEL Pulse Duration Using Laser Heater Pulse Shaping	laser, electron, simulation, experiment	2654
	V. Grattoni Università degli Studi di Trieste, Trieste, Italy E. Allaria, L. Badano, M.B. Danailov, A.A. Demidovich, S. Di Mitri, L. Giannessi, G. Penco, E. Roussel, P. Sigalotti, S. Spampinati, M. Trovò, M. Veronese Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy E. Ferrari PSI, Villigen PSI, Switzerland
	New Free-Electron Laser facilities deliver VUV and X-ray radiation with pulse length in the range of hundreds and tens of fs. A further reduction of the FEL pulse length is desired by those experiments aiming at probing ultrafast phenomena. Unlike SASE FEL, where the pulse duration is mainly driven by the electron bunch duration, in a seeded FEL the pulse duration can be determined by the seed laser properties. The use of techniques able to locally deteriorate the electron beam properties such as emittance or energy spread have been used in SASE FELs to reduce the region of the electron beam that is able to produce FEL radiation and hence reduce the FEL pulse length. The temporal shaping of the laser heater can be used to create an electron beam characterized by a very large energy spread all along the bunch except for a small region. We report measurements of the effect of the laser heater shaping on the electron beam phase-space performed at FERMI. Impact on the final FEL pulse properties are predicted with a series of numerical simulations.
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WEPAB037	Two-Bunch Operation at the FERMI FEL Facility	linac, wakefield, laser, electron	2663
	G. Penco, E. Allaria, S. Bassanese, P. Cinquegrana, S. Cleva, M.B. Danailov, A.A. Demidovich, S. Di Mitri, M. Ferianis, G. Gaio, D. Gauthier, L. Giannessi, M. Predonzani, F. Rossi, E. Roussel, S. Spampinati, M. Trovò Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy L. Giannessi ENEA C.R. Frascati, Frascati (Roma), Italy E. Roussel PhLAM/CERLA, Villeneuve d'Ascq, France
	FERMI is a linac-driven free electron laser (FEL) based upon the High Gain Harmonic Generation (HGHG) scheme. In standard conditions a bunch of 700 pC of charge with sub mm-mrad emittances is accelerated to 1.2-1.5GeV in a normal conducting S-band linac and drives FEL-1 or FEL-2 undula-tor line, which lase respectively in the range 100-20nm or 20-4nm. A number of two-color schemes have been implemented at FERMI for pump/probe experiments, all consisting in making two portions of the same electron bunch lase at two different wavelengths, with a time-separation from 0 to few hundreds of fs. In order to increase the time separation to ns and tens of ns we have explored the acceleration of two inde-pendent electron bunches separated by multiple of the linac main radio-frequency period, i.e. 333ps. Measure-ments and characterization of this two-bunch mode oper-ation are presented, including trajectory control, impact of longitudinal and transverse wakefields on the trailing bunch and manipulation of the longitudinal phase space.
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WEPAB039	Development Perspectives at FERMI	laser, linac, electron, experiment	2666
	M. Svandrlik, E. Allaria, L. Badano, F. Bencivenga, C. Callegari, F. Capotondi, F. Cilento, P. Cinquegrana, M. Coreno, I. Cudin, G. D'Auria, M.B. Danailov, R. De Monte, G. De Ninno, P. Delgiusto, A.A. Demidovich, M. Di Fraia, S. Di Mitri, B. Diviacco, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, P. Furlan Radivo, G. Gaio, D. Gauthier, F. Gelmetti, L. Giannessi, F. Iazzourene, 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. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	FERMI is the seeded Free Electron Laser (FEL) user facility at the Elettra laboratory in Trieste, operating in the ultraviolet to soft X-rays spectral range; the radiation produced by the seeded FEL is characterized by a number of desirable properties, such as wavelength stability, low temporal jitter and longitudinal coherence. In this paper, after an overview of the FEL performances, we will present the development plans under consideration for the next 3 to 5 years. These include an upgrade of the linac and of the existing FEL lines, the possibility to perform multipulse experiments in different configurations and an Echo Enabled Harmonic Generation (EEHG) experiment on FEL-2, the FEL line extending to 4 nm (310 eV).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB039
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WEPAB058	Commissioning Status of the Dalian Cohernet Light Source	laser, electron, undulator, linac	2709
	G.L. Wang DICP, Dalian, People's Republic of China
	The Dalian Coherent Light Source (DCLS) is a seeded FEL user facility working at 50-150 nm, now under commissioning in Dalian, China. The facility consists of a 300 MeV normal-conducting S-band linear accelerator (LINAC) and two undulator beamlines. The first beam-line (FEL-1) will provide picosecond FEL radiation with the pulse energy up to several hundreds micro-joule, the second beam-line (FEL-2) will be a femtosecond and polarization FEL. The LINAC and FEL-1 beam-line construction was complete by the summer of 2016, the installation of FEL-2 is in preparation. High power RF conditioning of the LINAC started in August 2016 and the beam commissioning initiated 3 months later. This article describes the commissioning status of DCLS, reports on the goals achieved so far.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB058
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WEPAB065	Proposal for the Generation of Terawatt, Attosecond X-Ray Pulses in Free Electron Lasers	undulator, radiation, laser, electron	2723
	Z. Wang, C. Feng, Z.T. Zhao SINAP, Shanghai, People's Republic of China
	A feasible novel method is proposed to generate attosecond terawatt X-ray radiation pulse in free electron lasers, which could find its application on multiple science fields. In our scheme, a chirped laser is employed to generate a chirped periodic current enhancement and a series of spatiotemporal shifters are applied between the undulator sections to generate ultra-short radiation pulse. Three-dimensional start-to-end simulations are carried out and the calculation results show that a 0.15nm X-ray pulse with the peak power of about 1TW and the pulse length of 0.1fs could be achieved in our scheme.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB065
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WEPAB066	POP Experiment for the HB-HGHG Scheme at SXFEL	electron, laser, radiation, free-electron-laser	2727
	K.S. Zhou, H.X. Deng, C. Feng, D. Wang SINAP, Shanghai, People's Republic of China
	Abstract High brightness, fully coherent and ultra-short free electron lasers (FEL) operating in the soft x-ray region are opening up new frontiers in many scientific fields. In this paper, we perform the design studies for the proof-of-principle experiment of the recently proposed HB-HGHG scheme at SXFEL test facility with a two-stage setup. The first stage of SXFEL is used for the generation of the coherent signal at 30th harmonic of the seed through the coherent harmonic generation process. Then this coherent signal is shifted ahead by the 'fresh bunch' chicane of SXFEL and initiates the strong coherent radiation in the radiator of the second stage of SXFEL. The output properties have been compared with the conventional EEHG and the two-stage cascaded HGHG with the same harmonic up-conversion number.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB066
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WEPAB070	Study of ESASE Scheme with Microbunching Instability for Generating Attosecond-Terawatt X-Ray Pulse in XFELs	laser, electron, simulation, free-electron-laser	2741
	C.H. Shim, D.E. Kim, I.S. Ko POSTECH, Pohang, Kyungbuk, Republic of Korea Y.W. Parc PAL, Pohang, Kyungbuk, Republic of Korea
	Recent studies show that the attosecond-terawatt X-ray pulse in XFELs can be generated by using ESASE (enhanced self-amplified spontaneous emission) scheme to obtain a sub-femtosecond spike in the electron peak current. However, ESASE scheme is not working properly when the microbunching instability is taken into account. The instability can be suppressed when the laser heater system which increases the uncorrelated energy spread of the electron beam is used in the injector. The effect of the microbunching instability on the performance of ESASE scheme will be discussed. In addition, the optimized results with the laser heater system for generating attosecond-terawatt X-ray pulse in XFELs is also presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB070
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WEPAB074	On the Coherence Properties of FEL	laser, undulator, simulation, experiment	2753
	M.A. Pop, F. Curbis, S. Werin MAX IV Laboratory, Lund University, Lund, Sweden
	Free Electron Lasers (FEL) are one of the most brilliant light sources in the world and their unique properties are driving worldwide research in understanding and improving them. Numerous papers have already been published describing the output of the FEL in terms of coherence and bandwidth. In this contribution, however, we focus on how the coherence evolves along the FEL undulator and on what factors influence it the most. Using Genesis⁻¹.3* we have been able to follow and record the light field as it is being produced in the undulator. Our analysis method takes advantage of the extensively studied double pinhole experiment and uses the principles behind it to create a tool for extracting coherence information from the radiation field. We will present the scope, limitations and advantages of these virtual experiments as well as an application on an example FEL, to showcase what kind of information can be extracted using this method. * Numerical simulation code used for particle and field distribution tracking along the undulator developed by Sven Reiche
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB074
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WEPAB077	The Soft X-Ray Laser Project at MAX IV	laser, undulator, electron, linac	2760
	S. Werin, J. Andersen, F. Curbis, L. Isaksson, M. Kotur, F. Lindau, E. Mansten, D. Olsson, H. Tarawneh, P.F. Tavares, S. Thorin MAX IV Laboratory, Lund University, Lund, Sweden S. Bonetti, A. Nilsson Stockholm University, Stockholm, Sweden V.A. Goryashko Uppsala University, Uppsala, Sweden P. Johnsson Lund University, Lund, Sweden M. Larsson, P. Salén FYSIKUM, AlbaNova, Stockholm University, Stockholm, Sweden O. Tjernberg KTH Physics, Stockholm, Sweden
	A soft x-ray laser beamline utilising FEL technology is being designed for the Short Pulse Facility (SPF) at the MAX IV Laboratory. A conceptual design study has been started following on the scientific case already prepared in collaboration between several Swedish Universities and driven by a strong (Swedish) user demand []. The baseline goal of the SXL beamline is to generate intense and short pulses in the range 1-5 nm (1-0.2 keV). The system is building on the MAX IV linac system, already today providing 3 GeV and pulses compressed to 100 fs for other applications within the SPF. As a special feature we foresee a variety of pump-probe capabilities. We here describe design issues and solutions for the accelerator and FEL system. http://frielektronlaser.se/onewebmedia/SXL_science_case₁61102.pdf
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB077
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WEPAB083	Development of Linac-Based MIR/THz FEL Facility and Photocathode RF-gun in Thailand	electron, undulator, laser, gun	2763
	K. Buakor, N. Chaisueb, K. Damminsek, S. Rimjaem, J. Saisut, C. Thongbai, W. Thongpakdi Chiang Mai University, Chiang Mai, Thailand
	A linac-based MIR/THz free-electron laser facility is under the development at the Plasma and Beam Physics Research Facility, Chiang Mai University. The ultimate goal of the project is to generate the infrared radiation covering the wavelengths from 13 to 125 μm. The main applications of the radiation involved MIR/THz imaging and spectroscopy. The future FEL facility will consists of an injector system, an experimental station for coherent transition radiation, two magnetic bunch compressors and two undulator magnets equipped with optical cavities for MIR and THz beamlines. An expected electron beam energy is between 10 to 20 MeV with an energy spread of about or less than 1 %. Two undulator magnets with maximum undulator parameters of 1 and 0.95 will be used for generation of the THz-FEL and MIR-FEL, respectively. In this paper, we present the status of the design and construction of this future FEL facility.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB083
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WEPAB084	Development of Injector System for MIR/THz Free-Electron Laser Facility in Thailand	electron, gun, undulator, simulation	2767
	W. Thongpakdi, S. Rimjaem Chiang Mai University, Chiang Mai, Thailand
	Development of a linac-based MIR/THz FEL light source is ongoing at the Plasma and Beam Physics Research Facility, Chiang Mai University. The future facility will consist of an S-band thermionic cathode RF electron gun, a pre-magnetic bunch compressor in a form of alpha magnet, an S-band travelling-wave linac structure, a 180-degree achromat system and two undulator magnets equipped with optical cavities. This research focuses on start-to-end beam dynamics simulations of the injector system. The aim of the study is to produce high quality electron beam at the entrance of the THz undulator magnet. The simulation was conducted by using programs PARMELA and ELEGANT. The program PARMELA was utilized to study the electron beam dynamics inside the RF-gun. Then, the program ELEGANT was used to optimize the injector system parameters. Optimization of physical specifications for the achromat system was performed to obtain short electron bunches with small energy spread at the undulator entrance. In this paper, results of beam dynamics simulations with suitable condition for the THz-FEL beamline are presented and discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB084
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WEPAB087	TARLA: The First Facility of Turkish Accelerator Center (TAC)	electron, cavity, laser, linac	2776
	A.A. Aksoy, A.A. Aydin, C. Kaya Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey B. Ketenoğlu, O. Yavaş Ankara University, Faculty of Engineering, Tandogan, Ankara, Turkey
	Funding: Work supported by Ministry of Development of Turkey Turkish Accelerator and Radiation Laboratory in Ankara (TARLA) is proposed as first accelerator based infrastructure in Turkey as a first step Turkish Accelerator Center (TAC). The facility under construction at Institute of Accelerator Technologies of Ankara University since 2012. Based superconducting technology, TARLA accelerator will offer a multi-experiment facility providing various accelerator-based radiation sources for the users coming from different fields like physics, chemistry, biology, material sciences, medicine and nanotechnology. Two of the planed free-electron laser (FEL) beamlines of TARLA will provide Continuous Wave (CW) tunable radiation of high brightness in the mid- and far-infrared regime. In addition a Bremmstrahlung radiation station is proposed within current scope of TARLA. In this paper current status of facility is presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB087
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WEPAB089	Design Study for the Generation of Few-Cycle FEL Pulses Using Mode-Locked Afterburner Scheme at Clara	bunching, laser, simulation, radiation	2783
	C.L. Shurvinton, D.J. Dunning, N. Thompson STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Ultrashort pulse operation in FELs is a highly desirable capability for imaging matter on ultrafast timescales. This paper presents a design study for a proof-Âof-Âprinciple demonstration of the mode-locked afterburner (ML-AB) scheme on the FEL test facility CLARA. A start-to-end simulation has been constructed using the time-Âdependent three-Âdimensional FEL code GENESIS 1.3 to evaluate the performance of the scheme. The ability to produce pulses of several femtoseconds in duration with peak powers of the order of 100 MW at 100 nm wavelength is predicted.Â Such pulses have duration of 2 fs (6 optical cycles), a factor of ~5 shorter than the FEL cooperation length. Potential routes for further optimisation and alternative operating modes are explored.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB089
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WEPAB090	Developments in the CLARA FEL Test Facility Accelerator Design and Simulations	laser, undulator, simulation, optics	2787
	P.H. Williams, D.J. Dunning, N. Thompson STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, 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. The requirement to co-propagate the beam with laser seeds of very different wavelengths has led to a redesign of the section preceding the undulators, with a dogleg being replaced by a chicane. Additional refinements of the facility design include the inter-undulator sections. With this finalised design we show start to FEL simulations for all beam modes envisaged.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB090
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WEPAB097	Modelling Two-Colour FEL with Wide Wavelength Separation and Individual Polarisation Tuning	polarization, undulator, simulation, electron	2808
	D. Bultrini, N. Thompson Cockcroft Institute, Warrington, Cheshire, United Kingdom R.J. Allan The Hartree Centre, Science and Technology Facilities Council (STFC/DL), Warrington, United Kingdom L.T. Campbell, B.W.J. MᶜNeil USTRAT/SUPA, Glasgow, United Kingdom D.J. Dunning, N. Thompson STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom J.D.A. Smith TXUK, Warrington, United Kingdom
	Free electron lasers (FELs) are currently enabling cutting edge research in chemistry, biology and physics. We use simulations to assess a new FEL capability that would add to the impressive repertoire of experiments made possible by the technology: a two-colour independent polarization mode, which allows for light pulses with variable temporal separation, individually tuneable polarisation, and widely separated wavelength. Simulations are carried out using the broad bandwidth FEL code Puffin, the results of which are used to discuss the radiation properties of the output. This scheme is applicable to existing and proposed facilities which feature undulators with variable ellipticity and gap.
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WEPAB108	Angular Trajectory Kicks in a High-Gain Free-Electron Laser	electron, radiation, laser, free-electron-laser	2830
	P. Baxevanis, Z. Huang, G. Stupakov SLAC, Menlo Park, California, USA
	In a free-electron laser (FEL), transverse momentum offsets (or kicks) are introduced either inadvertently (through wakefields or mis-steering of the electron beam) or as part of dedicated schemes that require off-axis radiation propagation. Studying the influence of this effect on the performance of machines such as LCLS-I/II is critical both from a tolerance point of view and for its practical applications. A theoretical analysis of a high-gain FEL driven by such a kicked beam will be presented, with a critical evaluation of previous studies.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB108
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WEPAB109	Multipole Field Effects in a Transverse Gradient Undulator	undulator, multipole, electron, simulation	2833
	P. Baxevanis, Z. Huang SLAC, Menlo Park, California, USA
	Using a transverse gradient undulator (TGU) is one of the methods proposed in order to enable the utilization of electron beams with large energy spread (such as those from plasma-based accelerators) in a free-electron laser (FEL). Most of the analytical treatments of this scheme assume a linear variation of the undulator field with one of the transverse coordinates. While this assumption leads to a simplified and more tractable model, including higher-order multipoles allows us to offer a more complete and rigorous description of the system. In this paper, we investigate the magnetic field components of a TGU using both theory and simulation and explore the impact of higher-order multipoles on the FEL performance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB109
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WEPAB116	LCLS Injector Laser Shaping and Applications	laser, electron, cathode, emittance	2844
	S. Li, S.C. Alverson, D.K. Bohler, A.B. Egger, A.R. Fry, S. Gilevich, Z. Huang, A. Miahnahri, D.F. Ratner, J. Robinson, F. Zhou SLAC, Menlo Park, California, USA
	In the Linear Coherent Light Source (LCLS) at SLAC, the injector laser plays an important role as the source of the electron beam for the Free Electron Laser (FEL). The beam emittance and FEL performance are highly related to the transverse shape of the injector laser. When the injector laser has hot spots and non-uniformities that can carry over to the electron beam and degrade electron emittance and FEL performance, it requires long hours of manual adjustment by laser engineers and strenuous machine tuneup. The injector laser shaping project at LCLS aims to have precise control of the driver laser transverse profile in order to produce arbitrary electron beam profiles, which will enable us to study effects of laser shape on beam emittance and FEL performances. We use a digital micromirror device (DMD) to manipulate the drive laser profile. In this paper, we briefly discuss the implementations of laser shaping at LCLS. We demonstrate two applications of laser shaping. We present results of using laser shaping to control the X-ray laser output via an online optimizer. We also show the photocathode quantum efficiency measurements across cathode surface using the DMD.
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WEPIK100	The Applicability of NEG Coated Undulator Vessels for the CLARA FEL Test Facility	vacuum, wakefield, undulator, impedance	3181
	O.B. Malyshev, K.B. Marinov, K.J. Middleman, N. Thompson, R. Valizadeh, P.H. Williams STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom O.B. Malyshev, K.J. Middleman, N. Thompson, R. Valizadeh, P.H. Williams Cockcroft Institute, Warrington, Cheshire, United Kingdom
	CLARA is a FEL test facility at Daresbury Laboratory (DL), UK. The undulator vacuum chamber is 20 m long with inner diameter 6 mm and its vacuum performance can benefit from a NEG coating. The thickness of the coating layer must be carefully optimised. A layer ~ 1 um would help the vacuum but a thinner layer would be partially transparent for the EM field reducing the resistive wall wakefields due to the NEG. A very thin layer, however, may not yield the necessary vacuum performance. Two types of NEG coatings produced at DL - dense and columnar - were considered. Their bulk conductivities were measured in a separate study. The resistive wall wakefield impedance was calculated following the standard approach for multilayer vessels. A 250 fs rms electron bunch was generated in ASTRA and its wakefield was obtained from the vessel impedance. The FEL performance was then studied through GENESIS simulations and the result compared to the case with no wakefields. It was found that NEG layers thicker than 100 nm give an unacceptable reduction of the FEL power and the vacuum performance of such thin coatings is unknown. Possible solutions to this problem are discussed.
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WEPIK113	Entrance and Exit CSR Impedance for Non-Ultrarelativistic Beam	impedance, wakefield, dipole, bunching	3214
	R. Li JLab, Newport News, Virginia, USA C.-Y. Tsai Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
	Funding: Work supported by the Department of Energy, Laboratory Directed Research and Development Funding, under Contract No. DE-AC05-06OR23177 For a high-brightness electron beam being transported through beamlines involving bending systems, the coherent synchrotron radiation (CSR) and longitudinal space charge (LSC) interaction could often cause microbunching instability. The semi-analytical Vlasov solver for microbunching gain* depends on the impedances for the relevant collective effects. The existing results for CSR impedances are usually obtained for the ultrarelativistic limit. To extend the microbunching analysis to cases of low energies, such as the case of an ERL merger, or to density modulations at extremely small wavelength, it is necessary to extend the impedance analysis to the non-ultrarelativistic regime. In this study, we present the impedance analysis for the transient CSR interaction in the non-ultrarelativistic regime, for transients including both entrance to and exit from a magnetic dipole. These impedance results will be compared to their ultra-relativistic counterparts, and the corresponding wakefield obtained from the impedance for low-energy beams will be compared with the existing results of transient CSR wakefield for general beam energies. C.-Y. Tsai et al., Proc. of IPAC'15, 596 (2015). C. Mitchell et al ., Proc. of IPAC'13, 1832 (2014). * E. L. Saldin et al ., Nucl. Instrum. Meth. A 398, 373 (1997).
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WEPVA021	Phase Space Manipulation of Sub-Picosecond Electron Bunches Using Dielectric Wakefield Structures	emittance, wakefield, simulation, electron	3302
	T.H. Pacey, G.X. Xia UMAN, Manchester, United Kingdom D.J. Dunning, Y.M. Saveliev STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Dielectric lined waveguides have drawn interest due to their application as high gradient accelerating structures, in both externally driven and wakefield schemes. We present simulation studies of sub-picosecond electron bunches interacting with dielectric structures in the self-wake regime. The parameter space for a tunable, sub-millimeter aperture, terahertz frequency structure is investigated. The potential application as a longitudinal phase space dechirper is demonstrated, with specific application to CLARA at Daresbury Laboratory. The impact of transverse effects is considered and minimised. The resulting FEL output is simulated.
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WEPVA052	The Infrastructure for the Elettra Sincrotrone Trieste	storage-ring, linac, operation, laser	3375
	D. Zangrando, D. Baron, A. Buonanno, A. Galimberti, A. Martinolli, M. Miculin, D. Morelli Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	Elettra - Sincrotrone Trieste S.C.p.A. is a multidisciplinary international laboratory, specialized in generating high quality synchrotron and free-electron laser light and applying it in materials science. The main assets of the research centre are two advanced light sources, the electron storage ring Elettra and the free-electron laser (FEL) FERMI, continuously (H24) operated supplying light of the selected colour and quality to more than 30 experimental stations. In this paper, we are giving an overview on the status of the infrastructure plants devoted to ensuring the operation of Elettra and FERMI machines. We will also analyse the systems that mostly have impacted on the performance of both accelerators and their downtime.
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THYA1	New Scenarios of Microbunching Instability Control in Electron Linacs and Free Electron Lasers	electron, laser, linac, controls	3642
	E. Roussel, E. Allaria, M.B. Danailov, S. Di Mitri, E. Ferrari, D. Gauthier, L. Giannessi, G. Penco, M. Veronese Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	Laser-heater systems are essential tools to control and optimize high-gain free-electron lasers (FELs) working in the x-ray wavelength range. Indeed, these systems induce a controllable increase of the energy spread of the electron bunch. The heating suppresses longitudinal microbunching instability which otherwise would limit the FEL performance. We demonstrate that, through the action of the microbunching instability, a long-wavelength modulation of the electron beam induced by the laser heater at low energy can persist until the beam entrance into the undulators. This coherent longitudinal modulation is exploited to control the FEL spectral properties, in particular, multicolor extreme-ultraviolet FEL pulses can be generated through a frequency mixing of the modulations produced by the laser heater and the seed laser in the electron beam. We present an experimental demonstration of this novel configuration carried out at the FERMI FEL. *E. Roussel et al., Phys. Rev. Lett. 115, 214801 (2015)
	Slides THYA1 [14.837 MB]
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THPAB014	An Adaptive Mesh-Based Method for the Efficient Simulation of LSC-Driven Microbunching Gain in FEL Applications	electron, bunching, acceleration, simulation	3720
	Ph. Amstutz University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany M. Vogt DESY, Hamburg, Germany
	Electron beams with high peak current as they are required for the operation of free-electron lasers (FELs) are often generated by means of a series of magnetic bunch compressors. In conjunction with a collective coherent force, e.g. longitudinal space-charge (LSC), bunch compressors can possibly cause a wavelength dependent amplification of initial density inhomogeneities, potentially to an extent detrimental to the operation of the FEL. A common model, consisting of LSC, acceleration (kicks), and magnetic chicanes (drift-type maps), is governed by a time-discrete Vlasov-Poisson system. Such systems have been successfully simulated using mesh based representations of the phase space density (PSD) and the method of characteristics for the update step. However, for the irregular and exotic PSDs, prevalent in FEL applications, a homogeneous high resolution discretization on a naive rectangular mesh can be prohibitively wasteful. Here we present an approach based on adaptive tree refinement that addresses the complexity of the PSDs and allows for the efficient simulation of LSC-driven micro-bunching in FELs.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB014
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THPAB036	An Experimental Study of Beam Dynamics in the ERL-Based Novosibirsk Free Electron Laser	radiation, diagnostics, electron, synchrotron	3781
	V.M. Borin, L.M. Schegolev, O.A. Shevchenko, N.A. Vinokurov BINP SB RAS, Novosibirsk, Russia V.L. Dorokhov, O.I. Meshkov BINP, Novosibirsk, Russia
	Transverse and longitudinal dynamics of the electron beam of the Novosibirsk infrared Free Electron Laser is studied. The Novosibirsk FEL is based on the multi-turn energy recovery linac (ERL). The ERL operate in CW mode with an average current about 10 mA. Therefore non-destructive beam diagnostics is preferable. The beam energy at the last track of the ERL is 42 MeV. As a result, significant part of synchrotron radiation from bending magnets is in the visible range. The transverse beam dimensions were measured with the optical diagnostics before and after the undulator applied for generation of middle-infrared coherent radiation. The obtained data is used to calculate the beam energy spread and emittance. The longitudinal beam dynamics was studied with electro-optical dissector.
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THPAB053	Laser Heater Deisgn for the CLARA FEL Test Facility	laser, undulator, electron, dipole	3833
	A.D. Brynes, S.P. Jamison, B.D. Muratori, N. Thompson, P.H. Williams STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom S.P. Jamison, B.D. Muratori, N. Thompson, P.H. Williams Cockcroft Institute, Warrington, Cheshire, United Kingdom
	We present considerations of microbunching studies in the CLARA (Compact Linear Accelerator for Research and Applications), the proposed UK FEL test facility under construction at Daresbury Laboratory. CLARA, a high-brightness electron linac, presents an opportunity to study the microbunching instability. A number of theoretical models have been proposed concerning the causes of this instability, and it has also been observed at various FEL facilities. We have applied these models to the CLARA FEL, and propose a suitable laser heater design which will provide flexibility in terms of the range of modes of operation for CLARA. We also propose a method for inducing and controlling the microbunching instability via pulse stacking of the photoinjector laser.
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THPAB078	Beam Dynamics Studies of the Transverse Gradient Undulator and Its Application to Suppression of Microbunching Instability	electron, undulator, focusing, laser	3895
	T. Liu, Y. Ding, Z. Huang, W. Qin SLAC, Menlo Park, California, USA T. Liu University of Chinese Academy of Sciences, Beijing, People's Republic of China T. Liu, D. Wang SINAP, Shanghai, People's Republic of China
	A transverse gradient undulator (TGU) which was initially proposed for high gain free electron lasers (FELs) driven by electron beams with relatively large energy spread, can be extended to the application of beam dynamics, such as phase-merging enhanced harmonic generation FEL and suppression of microbunching instability. In this contribution we present beam dynamics studies of the TGU, analyze the resulting focusing and dispersion, and discuss the effects of an additional corrector on the TGU. As an application to beam dynamics, we show a feasible transport system based on the TGU as a reversible electron beam heater to suppress the microbunching instability of the electron beam.
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THPAB105	Design and Operation of the Integrated 1.3 GHz Optical Reference Module with Femtosecond Precision	laser, detector, controls, operation	3963
	T. Lamb, L. Butkowski, E.P. Felber, M. Felber, M. Fenner, S. Jabłoński, T. Kozak, J.M. Müller, P. Prędki, H. Schlarb, C. Sydlo, M. Titberidze, F. Zummack DESY, Hamburg, Germany
	In modern Free-Electron Lasers like FLASH or the European XFEL, the short and long-term stability of RF reference signals gains in importance. The requirements are driven by the demand for short FEL pulses and low-jitter FEL operation. In previous publications, a novel, integrated Mach-Zehnder Interferometer based scheme for a phase detector between the optical and the electrical domain was presented and evaluated. This Laser-to-RF phase detector is the key component of the integrated 1.3 GHz Optical Reference Module (REFM-OPT) for FLASH and the European XFEL. The REFM-OPT will phase-stabilize 1.3 GHz RF reference signals to the pulsed optical synchronization systems in these accelerators. Design choices in the final hardware configuration are presented together with measurement results and a performance evaluation from the first operation period in the European XFEL.
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THPAB108	Femtosecond Optical Synchronization System for the European XFEL	laser, timing, free-electron-laser, electron	3969
	C. Sydlo, M. Felber, C. Gerth, T. Kozak, T. Lamb, J.M. Müller, H. Schlarb, F. Zummack DESY, Hamburg, Germany
	Accurate timing synchronization on the femtosecond timescale is an essential installation for time-resolved experiments at free-electron lasers (FELs) such as FLASH and the upcoming European XFEL. Conventional RF timing systems suffer from RF attenuation for such long distances and have reached to date a limit for synchronization precision of around 100 femtoseconds. An optical synchronization system is used at FLASH and is based on the distribution of femtosecond laser pulses over actively stabilized optical fibers. The upcoming European XFEL has raised the demands due to its large number of stabilized optical fibers and a length of 3400 m. The increased lengths for the stabilized optical fibers necessitated major advancement in precision to achieve the requirement of less than 10 femtosecond precision. This paper reports on the status of the laser-based synchronization system at the European XFEL.
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THPAB110	Custom Optomechanics for the Optical Synchronization System at the European XFEL	laser, timing, alignment, coupling	3976
	F. Zummack, M. Felber, C. Gerth, T. Lamb, J.M. Müller, M. Schäfer, H. Schlarb, C. Sydlo DESY, Hamburg, Germany
	Free-electron-lasers like the upcoming European XFEL demand highly reliable optical synchronization in range of few femtoseconds. The well known optical synchronization system at FLASH had to be re-engineered to meet XFEL requirements comprising demands like ten times larger lengths and raised numbers of optically synchronized instruments. These requirements directly convert to optomechanical precision and have yielded in a specialized design accounting for economical manufacturing technologies. These efforts resulted in reduced spatial dimensions, improved optical repeatability, maintainability and even reduced production costs. To account for thermal influences the heart of the optical synchronization system is based on an optical table made out of SuperInvar. To fully exploit its excellent thermal expansion coefficient, mechanical details need to be taken into account. This work presents the design and its realization of the re-engineered optomechanical parts of the optical synchronization system, comprising mounting techniques, link stabilization units and optical delay lines for high drift suppression.
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THPAB123	Low Level RF Control System Architecture OF IR-FEL	controls, LLRF, electron, klystron	4014
	B. Du, G. Huang, L. Lin, W. Liu, Z.R. Zhou USTC/NSRL, Hefei, Anhui, People's Republic of China
	Infrared free electron laser (IR-FEL) is one type of laser driven by accelerator and generated by undulator. It is built by National Synchrotron Radiation Laboratory (NSRL). Compared to synchrotron radiation light source, it have much higher demand of beam quality. Low level RF control system (LLRF) need to reach higher controlled accuracy corresponded to the demand. Accelerating structure which contains one pre-buncher, one buncher and two accelerating tube can accelerate beam to 60MeV. Frequency distribution system use direct digital synthesizer technology to generate 5 signal of different frequency. LLRF system detect 8 channels signal, one for control loop, and the others for monitor and interlock. The hardware contain MTCA.4 architecture which is advanced in global; RF board for downconverter and IQ modulation output; DSP board for sampling, controller and transmission.
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THPAB124	DSP Frame and Algorithm of LLRF of IR-FEL	feedback, LLRF, controls, target	4017
	B. Du, G. Huang, L. Lin, W. Liu, Z.R. Zhou USTC/NSRL, Hefei, Anhui, People's Republic of China
	Infrared Free Electron Laser (IR-FEL) use linear accelerator to accelerate electron to relative speed and then generate simulated radiation of infrared wavelength by periodic magnetic field of undulator. The amplitude and phase of microwave field need to be controlled precisely by low level RF control system (LLRF) to meet the high quality demand of electron from undulator. This paper mainly introduce the digital signal processing frame and feedback algorithm. Four times frequency sampling can realize IQ demodulation precisely and reduce DC offset, amplitude sampling error is less than 0.075% and phase sampling error is less than 0.1°. Pipeline CORDIC can calculate amplitude and phase by parallel processing and shift operation. Phase calculating accuracy reach 0.0005° when iteration count is 18. FIR filter is used to improve frequency selected performance. Feedback loop use digital PI controller to adjust system output.
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THPAB128	Beam Arrival Time Analisis Based on CBPM at DCLS	simulation, cavity, experiment, undulator	4023
	S.S. Cao, J. Chen, L.W. Lai, Y.B. Leng SINAP, Shanghai, People's Republic of China N. Zhang SSRF, Shanghai, People's Republic of China
	Dalian Coherent Light Source is the first high gain free electron lasers (FEL) user facility in China, which is dedicated at extreme ultraviolet (EUV) spectral regime of 150-50nm for various scientific fields. In its undulator section, the beam-line was equipped with ten pair of high-precision cavity beam position monitor (CBPM), which can be used for beam position and beam arrival time (BAT) measurement. Based on this, we have done some preliminary research about the beam fight time with the reference cavities of CBPMs for the future research on BAT. In this paper, we presented the scheme of the beam fight time (BFT) research, analyzed the results, and evaluated the consistency and stability of BFT.
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THPIK038	Design of a 100 kW Solid-State RF Pulse Amplifier with a TE011 Mode RF Combiner at 476 MHz	cavity, electron, klystron, laser	4180
	Y. Otake, T. Asaka, T. Inagaki RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	Solid-state RF amplifiers, which have long lifetimes and small failures, are the recent current of high-power RF sources for particle accelerators. Hence, we designed a 100 kW solid-state amplifier with a TE011 mode cavity (Q0=100, 000) power combiner with extreme low-loss operated at 476 MHz and a 6 us pulse width. Developing this amplifier is for replacement of a high-power amplifier using an induction output tube, IOT, in the X-ray free-electron laser, SACLA. In SACLA, highly RF phase and amplitude stabilities of less than 0.01 deg. and 10^-4 in rms are necessary to stable lasing within a 10 % intensity fluctuation. The amplifier comprises a drive amplifier, a reentrant cavity RF power divider, 100 final amplifier modules with a 1 kW output each and a TE011 mode cavity combiner. Water-cooling within 10 mK and a DC power supply with a noise of less than -100 dBV at 10 Hz for the amplifier is necessary to realize the previously mentioned stabilities. Based on the experimental results of a test amplifier module and test combiner cavities, possibility to realize the above-mentioned specifications is large. We report the detail and a part of the performance of the 100 kW amplifier.
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FRXBB1	Novosibirsk Four-Orbit ERL With Three FELs	electron, radiation, undulator, gun	4836
	N.A. Vinokurov, V.S. Arbuzov, K.N. Chernov, I.V. Davidyuk, O.I. Deichuli, E.N. Dementyev, B.A. Dovzhenko, Ya.V. Getmanov, Ya.I. Gorbachev, B.A. Knyazev, E.I. Kolobanov, A.A. Kondakov, V.R. Kozak, E.V. Kozyrev, S.A. Krutikhin, V.V. Kubarev, G.N. Kulipanov, E.A. Kuper, I.V. Kuptsov, G.Y. Kurkin, L.E. Medvedev, S.V. Motygin, V.N. Osipov, V.K. Ovchar, V.M. Petrov, A.M. Pilan, V.M. Popik, V.V. Repkov, T.V. Salikova, M.A. Scheglov, I.K. Sedlyarov, S.S. Serednyakov, O.A. Shevchenko, A.N. Skrinsky, S.V. Tararyshkin, V.G. Tcheskidov, A.G. Tribendis, P. Vobly, V. Volkov BINP SB RAS, Novosibirsk, Russia I.V. Davidyuk, Ya.V. Getmanov, B.A. Knyazev, E.V. Kozyrev, S.S. Serednyakov, N.A. Vinokurov NSU, Novosibirsk, Russia A.G. Tribendis NSTU, Novosibirsk, Russia
	The Novosibirsk FEL facility has three FELs, installed on the first, second and fourth orbits of the ERL. The first FEL covers the wavelength range of 90 - 240 mkm at an average radiation power of up to 0.5 kW with a pulse repetition rate of 5.6 or 11.2 MHz and a peak power of up to 1 MW. The second FEL operates in the range of 40 - 80 mkm at an average radiation power of up to 0.5 kW with a pulse repetition rate of 7.5 MHz and a peak power of about 1 MW. These two FELs are the world's most powerful (in terms of average power) sources of coherent narrow-band (less than 1%) radiation in their wavelength ranges. The third FEL was commissioned in 2015 to cover the wavelength range of 5 - 20 mkm. The Novosibirsk ERL is the first and the only multiturn ERL in the world. Its peculiar features include the normal-conductive 180 MHz accelerating system, the DC electron gun with the grid thermionic cathode, three operation modes of the magnetic system, and a rather compact (6×40 m2) design. The facility has been operating for users of terahertz radiation since 2004.
	Slides FRXBB1 [51.485 MB]
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MOPAB047

Electron Beam Phase Space Tomography at the European XFEL Injector

emittance, electron, quadrupole, optics

196

M. Scholz, B. Beutner
DESY, Hamburg, Germany

The FEL process is determined by the 6D phase space distribution of relativistic electron bunches. Experimental reconstructions of these distributions are therefore a step foreward to understand the beam dynamics and to optimize FEL operation. The reconstructions of the transverse phase spaces can be acieved with tomographic methods. In the injector of the European XFEL, measurements for the reconstruction of the phase spaces were carried out using phase advance scans with multiple quadrupoles. The beam sizes were kept optimized at the measurement screen. A transversely deflecting cavity (TDS) was used to streak the beam vertically. That allows to do longitudinally slice resolved measurements of the horizontal phase space. The horizontal streak required for the slice measurements in the vertical plane was achieved with a correlated linear energy spread and dispersion. In this paper, we present measurement results showing longitudinal slice resolved reconstructions of the transverse phase spaces taken in the European XFEL injector.

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MOPAB073

Measurement of Electron-Bunch Length Using Coherent Radiation in Infrared Free-Electron Laser Facilities

electron, detector, radiation, laser

288

N. Sei, H. Ogawa
AIST, Tsukuba, Ibaraki, Japan
K. Hayakawa, Y. Hayakawa, K. Nogami, T. Sakai, T. Tanaka
LEBRA, Funabashi, Japan
H. Ohgaki, H. Zen
Kyoto University, Kyoto, Japan

Funding: This study was financially supported by JSPS KAKENHI Grant Number JP16H03912.
We have studied techniques evaluating bunch length of micropulses in an electron beam. The bunch length of the electron beam is an important parameter for free-electron laser (FEL) facilities with linear accelerators. In order to obtain high FEL gain at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University and at Kyoto University Free Electron Laser (KU-FEL), the electron-bunch length is compressed to less than 1 ps in their undulator sections. Using the compressed electron beams, intense terahertz lights were generated by coherent radiation. The power of the coherent radiation was more than 50 micro-joule per electron-beam macropulse. We can extract the information of the bunch length of the electron-beam micropulse from the intense coherent radiation by using narrow-band diode detectors. In this presentation, experimental results of the measurements of the root-mean-square electron-bunch length using the coherent radiation at LEBRA* and KU-FEL** will be reported.
*: N. Sei et al., J. Opt. Soc. Am. B, 31, 2150 (2014).
**: N. Sei et al., Nucl. Instrum. Methods Phys. Res., Sect. A, 832, 208 (2016).

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MOPAB082

Design and Simulation of High Order Mode Cavity Bunch Length Monitor for Infrared Free Electron Laser

cavity, simulation, laser, electron

309

Q. Wang, X.Y. Liu, P. Lu, Q. Luo, B.G. Sun, L.L. Tang, J.H. Wei, F.F. Wu, Y.L. Yang, T.Y. Zhou, Z.R. Zhou
USTC/NSRL, Hefei, Anhui, People's Republic of China

Funding: Supported by The National Key Research and Development Program of China (2016YFA0401900, 2016YFA0401903); NSFC (11375178, 11575181); the Fundamental Research Funds for the Central Universities (WK2310000046)
A bunch length monitor using resonant cavity has been designed for the NSRL Infrared Free Electron Laser (IR-FEL) facility. To avoid the restriction of working fre-quency caused by the beam pipe radius, the high order modes of the harmonic cavities are utilized. The position and orientation of coaxial probes are optimized to avoid interference modes which come from the cavity and beam tube according to the analysis formula of electro-magnetic field distribution. Based on the parameters of IR-FEL, a simulation is performed to verify the feasibility of the bunch length monitor. The simulation result shows that the design meets the requirements of IR-FEL, and the resolution can be better than 50 fs.

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MOPAB083

The New Beam Current Transformer for IR-FEL Facility at NSRL *

diagnostics, electron, induction, electronics

312

J.H. Wei, H. Li, X.Y. Liu, P. Lu, B.G. Sun, J.G. Wang, Q. Wang, F.F. Wu, Y.L. Yang, T.Y. Zhou
USTC/NSRL, Hefei, Anhui, People's Republic of China

Funding: Supported by The National Science Foundation of China (Grant No. 11575181)
The beam current transformer (CT) is an important part of the beam diagnostics system as a kind of non-destructive intensity measurement. The beam CT has the strong dependence of the sensitivity and time constant on the time structure of the beam. To measure the macro-pulse beam intensity with 5-10 's length and 238 MHzμpulse repetition rate in the IR-FEL, it is necessary to find a suitable material as the CT core which can meet the measure requirement of the beam current. In this paper, three different magnetic materials were tested to find out that the laminated amorphous core owned the best performance, meanwhile, the mechanical structure was designed. The finished product passed the acceptance test.

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MOPAB095

Development of the Simulation Software Package for the CBPM System

simulation, cavity, network, experiment

349

J. Chen, L.W. Lai, Y.B. Leng, L.Y. Yu
SINAP, Shanghai, People's Republic of China
N. Zhang
SSRF, Shanghai, People's Republic of China

In recent years, the development and construction of Free Electron Laser (FEL) facilities are in full swing. For FEL facilities, to generate coherent X-ray, cavity beam position monitor (CBPM) system which consist of cavity BPM, RF front-end and signal processor are employed to measure the transverse position in the undulator section. A generic simulation software package, with the S21 parameters of the real components, for the design of the RF front-end and the optimize of the CBPM system was developed. In this paper, the development of the generic simulation software package, and the experiment results with beam at Shanghai Deep ultraviolet (SDUV) FEL facility to verify the correctness of the simulation soft package will be introduced. The application in the design and optimize of the RF front-end for the Dalian Coherent Source (DCLS) will be addressed as well .

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MOPAB149

Design of LCLS-II ATCA BPM System

linac, network, undulator, controls

477

A. Young, R. Claus, J.M. D'Ewart, J.C. Frisch, G. Haller, R.T. Herbst, S. L. Hoobler, U. Legat, J.J. Olsen, R. Ruckman, L. Sapozhnikov, S.R. Smith, T. Straumann, J.A. Vásquez, M. Weaver, E. Williams, C. Xu
SLAC, Menlo Park, California, USA

Funding: Work supported by U.S. Department of Energy under Contract Numbers DE-AC02-06CH11357
SLAC's LCLS-II is a next generation X-ray FEL that will use a CW 4 GeV superconducting linac with nominal bunch spacing of 1us will deliver both soft and hard x-ray FEL to users. In order to achieve the required performance, the SLAC Technical Innovation Directorate has developed a common hardware and firmware platform for beam instrumentation based on the ATCA crate format. We have designed a stripline and cavity BPM system based on this platform that is capable of measuring the beam position at full beam rate. The system will have a dynamic range between 1 pC to 300 pC. This paper will discuss the design of the BPM electronics, overall architecture and performance on LCLS-I.

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MOPIK070

Notes on Relations between Slice and Projected Beam Parameters

emittance, betatron

689

V. Balandin, N. Golubeva
DESY, Hamburg, Germany

We consider some aspects of the relations between slice and projected beam parameters.

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MOPIK078

Narrow-Band, Wide-Range Tuneable THz Source Based on the Slotted-Foil Technique

undulator, electron, radiation, simulation

712

J. Pfingstner, E. Adli, H. Holmestad
University of Oslo, Oslo, Norway
S. Bettoni, S. Reiche
PSI, Villigen PSI, Switzerland

The FEL user community has expressed a strong interest in a THz source for the excitation of their samples in pump probe experiments. The demanded THz properties are challenging to achieve, as they include a narrow bandwidth of <5-10%, the possibility of frequency tuning between 1 and 20 THz, a THz pulse energy of about 100 uJ, and a fixed phase relation from shot-to-shot. To fulfil these specifications, an accelerator-based source is proposed in this paper. It utilises the slotted-foil technique to create a pre-bunched electron beam that is injected into a helical undulator. Detailed simulation studies presented in this paper show that the corresponding undulator radiation has the demanded properties.

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MOPVA020

S2E Simulation of an ERL-Based High-Power EUV-FEL Source for Lithography

linac, electron, simulation, injection

894

N. Nakamura, R. Kato, T. Miyajima, M. Shimada
KEK, Ibaraki, Japan
R. Hajima
QST, Tokai, Japan
T. Hotei
Sokendai, Ibaraki, Japan

An energy recovery linac(ERL)-based free electron laser(FEL) is a possible candidate of a high-power EUV source for lithography. The ERL can provide a high-current and high-quality electron beam for the high-power FEL and also greatly reduce the dumped beam power and activation compared to ordinary linacs. An ERL-based EUV-FEL source has been designed using available technologies and resources*. For this design, we perform Start-to-End(S2E) simulation from the electron gun to the exit of the decelerating main linac to track the electron beam parameters and to evaluate the FEL performance. The electron bunches from the injector are off-crest accelerated to 800 MeV and compressed in the 1st arc and/or chicane to obtain a high-peak current for high FEL output. After the undulator section for SASE FEL, they are decompressed in the 2nd arc and then decelerated in the main linac to optimize the energy spread or the energy recovery efficiency. This paper will present the S2E simulation for the designed EUV-FEL source.
* N. Nakamura et al., Proc. of ERL2015, Stony Brook, NY, USA, pp.4-9.

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MOPVA127

Vertical Test Results for the LCLS-II 1.3 GHz First Article Cavities

cavity, cryomodule, SRF, linac

1152

A. Burrill, D. Gonnella, M.C. Ross
SLAC, Menlo Park, California, USA
G.K. Davis, A.D. Palczewski, L. Zhao
JLab, Newport News, Virginia, USA
A. Grassellino, O.S. Melnychuk
Fermilab, Batavia, Illinois, USA

The LCLS-II project requires 35 1.3 GHz cryomodules to be installed in the accelerator in order to deliver a 4 GeV electron beam to the undulators hall. These 35 cryomodules will consist of 8 1.3 GHz TESLA style SRF cavities, a design most recently used for the XFEL project in Hamburg, Germany. The cavity design has remained largely unchanged, but the cavity treatment has been modified to utilize the nitrogen doping process to allow for Quality factors in excess of 3x10¹⁰ at 16 MV/m, the designed operating gradient of the cavities in the CM. Two industrialized vendors are producing most of the SRF cavities for these cryomodules; and the performance of the first article cavities, 16 from each vendor, will be reported on in this paper.

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TUOAA2

A Soft X-Ray Free-Electron Laser Beamline of SACLA

electron, undulator, photon, laser

1209

K. Togawa, T. Asaka, N. Azumi, T. Hara, T. Hasegawa, N. Hosoda, T. Inagaki, T. Ishikawa, R. Kinjo, C. Kondo, H. Maesaka, S. Matsui, T. Ohshima, Y. Otake, S. Owada, H. Tanaka, T. Tanaka, M. Yabashi
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
T. Bizen, H. Kimura, S. Matsubara, K. Nakajima, T. Sakurai, T. Togashi, K. Tono
JASRI/SPring-8, Hyogo, Japan
T. Fukui
RIKEN SPring-8 Center, Innovative Light Sources Division, Hyogo, Japan

At the Japanese x-ray free-electron laser (FEL) facility, SACLA, the beamline-1 has been upgraded from a spontaneous radiation to a soft x-ray FEL beamline, which generates FEL lights over a wide wavelength range from the extreme-ultraviolet to the soft x-ray regions. We started operation for users in July 2016. A dedicated accelerator, which is a refinement of the SCSS test accelerator operated in 2005-2013, was installed beside the XFEL beamlines in the SACLA undulator hall. The SCSS concept to make an FEL facility compact was continuously adopted. In the 2016 summer shutdown period, the beam energy was upgraded from 500 MeV to 800 MeV by adding two C-band rf units. The maximum K-value of the undulator magnet is 2.1. The available wavelengths of the FEL lights were extended to the range from 8 to 50 nm with pulse energies between a few to few tensμJ at an operational repetition rate of 60 Hz. In this conference, we will report an overview of the upgraded SACLA-beamline-1 and characteristics of the FEL light pulse.

Slides TUOAA2 [15.457 MB]

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TUPAB020

AREAL 50 MeV Electron Accelerator Project for THz and Middle IR FEL

radiation, electron, emittance, gun

1355

G.A. Amatuni, Z.G. Amirkhanyan, V.S. Avagyan, A. Azatyan, V. Danielyan, H. Davtyan, S.G. Dekhtiarov, N. Ghazaryan, B. Grigoryan, L. Hakobyan, M. Ivanyan, V.G. Khachatryan, E.M. Laziev, T. Markosyan, N. Martirosyan, Sh.A. Mehrabyan, T. Melkumyan, T.H. Mkrtchyan, V.H. Petrosyan, V. Sahakyan, A. Sargsyan, A.S. Simonyan, A.V. Tsakanian, V.M. Tsakanov, A. Vardanyan, Ta.S. Vardanyan, T.L. Vardanyan, V. V. Vardanyan, A.S. Yeremyan, G.S. Zanyan
CANDLE SRI, Yerevan, Armenia
P.S. Manukyan
SEUA, Yerevan, Armenia
A.V. Tsakanian
HZB, Berlin, Germany

Advanced Research Electron Accelerator Laboratory (AREAL) is an electron accelerator project based on photo cathode RF gun. First phase of the facility is a 5 MeV energy RF photogun, which is currently under operation. The facility development implies energy upgrade to 50 MeV with further delivery of the electron beam to the undulator sections for Free Electron Laser and coherent undulator radiation generation in MIR and THz frequency ranges respectively. In this report the design study of AREAL 50 MeV facility main systems along with the beam dynamics and characteristics of expected radiation are presented.

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TUPAB049

Development of the High Power Terahertz Light Sources at LEBRA Linac in Nihon University

target, electron, radiation, linac

1437

T. Sakai, K. Hayakawa, Y. Hayakawa, K. Nogami, T. Tanaka
LEBRA, Funabashi, Japan
H. Ogawa, N. Sei
AIST, Tsukuba, Ibaraki, Japan

Funding: This work was supported by JSPS KAKENHI (Grant-in-Aid for Young Scientists (B)) Grant Number JP16K17539.
Development of a THz light source has been underway at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University in collaboration with National Institute of Advanced Industrial Science and Technology (AIST) since 2011. Basic research on coherent transition radiation (CTR) in the THz region has been carried out using the Parametric X-ray Radiation (PXR)-beam line of LEBRA. Since fiscal year 2016, the THz transport line has been constructed on the same axis as the PXR beam line taking the construction cost and simultaneous use of the two beams into account. Basic measurement and intensity upgrading test have been carried out for the THz lights generated on the PXR-generating electron beam line. The average intensity of the THz lights obtained at the output port in the accelerator room has been 5 mW. Construction of the THz transport beam line and the property of the THz lights is discussed in the report.

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TUPAB083

Commissioning Experience and Beam Optimization for DCLS Linac

linac, gun, emittance, cathode

1509

M. Zhang, D. Gu, Q. Gu, D. Huang, Z. Wang
SINAP, Shanghai, People's Republic of China

Dalian Coherent Light Source (DCLS), which will focus on the Physical Chemistry with time-resolved pump-probe experiments and EUV absorption spectroscopy techniques, is the first high gain FEL user facility in China. The 300MeV linac consists of a laser-driven rf-gun followed by 7 Sband accelerating tubes. A magnetic chicane is adopted to get the desired 300A peak current. After 5 months component installation, first photoelectrons were generated on 17 August 2016. In this paper, we give a summary of the commissioning experience and the beam parameters measurements. In addition, beam jitter sources are studied based on real machine performances.

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TUPAB084

Beam Stability Modeling and Jitter Control for SXFEL Linac

linac, controls, quadrupole, klystron

1513

M. Zhang, R.B. Deng, D. Gu, Q. Gu, D. Huang, Z. Wang
SINAP, Shanghai, People's Republic of China

FEL operations foresee stringent requirements for the stability of the global linac output parameters and this requirement is particularly stringent for the successful operation of an externally seeded FEL. In order to understand the sensitivity of these parameters to jitters of various error sources along the SXFEL linac, studies have been performed based on analytical methods and tracking code simulations. Using the tolerance budget as guidance, beam jitter control techniques are discussed on the view of the beam dynamics.

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TUPAB086

Design Study of a High-Intensity, Low-Energy Electron Gun

gun, electron, simulation, emittance

1517

Q. Zhang, K. Fan, T. Hu, K.F. Liu, Z.Y. Mei
HUST, Wuhan, People's Republic of China

An independently-tunable-cells thermionic RF gun (ITC-RF gun) is adopted in a compact FEL-THz facility due to its compactness, low-cost and high intensity. An electron gun is required to generate maximum beam current of 3.2 A at low energy of 15keV for the ITC-RF gun, which creates difficulties for the design of electron gun because of the strong space charge effect. A double-anode gridded gun structure is adopted that controls the beam current easily while maintains the energy dispersion less than 0.5%, with high perveance and high compression ratio. CST code has been used extensively for design optimization, which includes electrode shape, influences of grid, installation errors. A measurement scheme is also proposed for key parameters verification. Beam current, emittance and energy dispersion can be measured.

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TUPAB111

Energy Distribution and Work Function Measurements for Metal Photocathodes with Measured Levels of Surface Roughness

emittance, electron, detector, plasma

1580

L.B. Jones, T.S. Beaver, B.L. Militsyn, T.C.Q. Noakes, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
S. Mistry
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
S. Mistry
Loughborough University, Leicestershre, United Kingdom

Funding: The work is part of EuCARD-2, partly funded by the European Commission, GA 312453.
The minimum achievable emittance in an electron accelerator depends strongly on the intrinsic emittance of the photocathode electron source which is measureable as the mean longitudinal and transverse energy spreads in the photoemitted electrons. Reducing emittance in an accelerator driving a Free Electron Laser (FEL) delivers significant reduction in the saturation length for an x-ray FEL, reducing machine cost and increasing x-ray beam brightness. There are many parameters which affect the intrinsic emittance of a photocathode. Surface roughness is a significant factor*, and consequently the development of techniques to manufacture low roughness photocathodes with optimum emission properties is a priority for the electron source community. In this work, we present transverse energy distribution and work function measurements made using our TESS facility** for electrons emitted from copper and molybdenum photocathodes with differing levels of measured surface roughness.
* Proc. FEL '06, THPPH013, 583-586
** Proc. FEL '13, TUPPS033, 290-293

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TUPAB123

Hard X-Ray and Soft X-Ray Undulator Segments for the Linear Coherent Light Source Upgrade (LCLS-II) Project

undulator, linac, photon, electron

1605

M. Leitner, D. Arbelaez, A.J. Band, D. Bianculli, A.P. Brown, J.N. Corlett, A.J. DeMello, J.R. Dougherty, L. Garcia Fajardo, K. Hanzel, M. Hoyt, D.E. Humphries, D. Jacobs, C. Joiner, J.-Y. Jung, D. Leitner, S. Marks, K.A. McCombs, D.V. Munson, K.L. Ray, D.A. Sadlier, J.J. Savino, D. Schlueter, E.J. Wallén, V. Waring, A. Zikmund
LBNL, Berkeley, California, USA
C.J. Andrews, D.E. Bruch, A.L. Callen, G. Janša, S. Jansson, K.R. Lauer, Yu.I. Levashov, D.S. Martinez-Galarce, B.D. McKee, H.-D. Nuhn, Â. Oven, M. Rowen, Z.R. Wolf
SLAC, Menlo Park, California, USA

Funding: Work supported by the Director Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Stanford Linear Accelerator Laboratory is currently constructing the Linear Coherent Light Source II (LCLS-II), a free-electron laser (FEL) which will deliver x-rays at an energy range between 0.2 keV and 5 keV at high repetition rate of up to ~1 MHz using a new 4 GeV superconducting RF linac, and at and an energy range between 1 keV and 25 keV when driven by an existing copper linac at up to 120 Hz repetition rate. To cover the full photon energy range, LCLS-II includes two variable-gap, hybrid-permanent-magnet undulator lines: A soft x-ray undulator (SXR) line with 21 undulator segments optimized for a photon energy range from 0.2 keV to 1.3 keV plus a hard x-ray undulator (HXR) line with 32 undulator segments designed for a photon energy range from 1.0 keV to 25.0 keV. Lawrence Berkeley National Laboratory is responsible for fabricating the 53 undulator segments. This paper summarizes the main parameters and design attributes for both LCLS-II undulator segment types.

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TUPAB130

Status of the LCLS-II Superconducting RF Linac

cryomodule, cavity, linac, operation

1630

A. Burrill
SLAC, Menlo Park, California, USA

The LCLS-II project requires the assembly and installation of 37 cryomodules in order to deliver a 4 GeV electron beam to the undulators to produce both soft and hard x-ray pulses at a repetition rate up to 1 MHz. All of the cryomodules will operate in continuous wave mode, with 35 operating at 1.3 GHz for acceleration and 2 operating at 3.9 GHz to linearize the longitudinal beam profile. The assembly and testing of the 1.3 GHz cryomodules is well underway and the 3.9 GHz cryomodule work is entering into the pre-cryomodule testing and component validation phase. Both of these efforts will be reported on in this paper.

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TUPAB135

A 1.75 mm Period RF-Driven Undulator

undulator, laser, electron, cavity

1643

F. Toufexis, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515, and the National Science Foundation under Contract No. PHY-1415437.
To reduce the linac energy, and hence the size required for a Free Electron Laser radiating at a given wavelength, a smaller undulator period with sufficient field strength is needed. Previous work from our group successfully demonstrated a microwave undulator at 11.424 GHz using a corrugated cylindrical waveguide operating in the HE11 mode. Scaling down the undulator period using this technology poses the challenge of confining and coupling* the electromagnetic fields while maintaining over-moded features for power handling capability and electron beam wakefield mitigation. In this work, we present a novel end section of an RF undulator at 91.392 GHz. To confine the fields inside the undulator, a corrugated waveguide is connected through a matching section to a linear taper and a mirror. After the mirror, a Bragg reflector and a matching section are used to reflect back all the fields leaking out of the mirror opening.
* F. Toufexis, J. Neilson, and S.G. Tantawi, Coupling and Polarization Control in a mm-wave Undulator, these proceedings.

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TUPAB137

Evaluation of FEL Performance with a Longer Injector Drive Laser Pulse at the LCLS

laser, emittance, electron, simulation

1651

F. Zhou, Y. Ding, J.P. Duris, S. Gilevich, P. Hering, S. Vetter
SLAC, Menlo Park, California, USA

Funding: US DOE under grant No. DE-AC02-76SF00515.
It is known that the X-ray Free Electron Laser (FEL) performance strongly depends on the beam emittance and peak current. Lengthening injector laser pulse can improve the injector emittance but the injector peak current is notably compromised, in comparison to nominal laser pulse. With this longer laser pulse, a stronger bunch compression through downstream bunch compressors is thus required to keep same final peak current as the nominal laser pulse mode. This process may cause stronger micro-bunching effect. At the LCLS, we perform preliminary experiments with doubling injector laser pulse. In this paper, we present the experimental results of the injector emittance, microbunching effects and FEL performance with the longer drive laser pulse.

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TUPIK003

Electron Transport on COXINEL Beam Line

electron, laser, undulator, free-electron-laser

1688

T. André, I.A. Andriyash, F. Blache, F. Bouvet, F. Briquez, M.-E. Couprie, Y. Dietrich, J.P. Duval, M. El Ajjouri, A.M. Ghaith, C. Herbeaux, N. Hubert, M. Khojoyan, M. Labat, N. Leclercq, A. Lestrade, A. Loulergue, O. Marcouillé, F. Marteau, P. N'gotta, P. Rommeluère, K.T. Tavakoli, M. Valléau
SOLEIL, Gif-sur-Yvette, France
S. Bielawski, C. Evain, C. Szwaj
PhLAM/CERLA, Villeneuve d'Ascq, France
S. Corde, J. Gautier, J.-P. Goddet, G. Lambert, B. Mahieu, V. Malka, S. Smartzev, C. Thaury
LOA, Palaiseau, France
E. Roussel
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

COXINEL experiment aims at demonstrating free electron laser (FEL) amplification with a laser plasma accelerator (LPA). For COXINEL, a dedicated 8 m transport line has been designed and prepared at SOLEIL. We present here LPA beam transport results around 180 MeV through this line. Different electron beam optics were applied.

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TUPIK108

Beam Based Alignment Studies for the CLARA FEL Test Facility

quadrupole, alignment, undulator, cavity

1971

J.K. Jones, N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

The CLARA (Compact Linear Accelerator for Research and Applications) test facility is designed to experimentally demonstrate innovative FEL schemes for future light source applications. Such schemes can place strict requirements on the accelerator beam properties as well as the relative alignment of the beam in the FEL radiators and modulators. Beam-based alignment (BBA) of the FEL section is therefore an operational requirement for all advanced FEL facilities. In this paper we demonstrate results of CLARA BBA simulations, and also report initial simulation results from the use of non-linear algorithms to optimise the FEL performance directly.

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TUPIK121

Dark Sector Experiments at LCLS-II (DASEL) Accelerator Design

kicker, experiment, laser, septum

2008

Y.M. Nosochkov, T.G. Beukers, A.R. Fry, C. Hast, T.W. Markiewicz, T.K. Nelson, N. Phinney, T.O. Raubenheimer, P.C. Schuster, N. Toro
SLAC, Menlo Park, California, USA

Funding: Work supported by the US DOE Contract DE-AC02-76SF00515.
DASEL (Dark Sector Experiments at LCLS-II) is a new accelerator and detector facility proposed to be built at SLAC. Its primary target is a direct observation of dark matter produced in electron-nuclear fixed-target collisions. DASEL takes advantage of the LCLS-II free electron laser (FEL) under construction at SLAC which will deliver a continuous electron beam from a 4-GeV superconducting linac. DASEL will operate parasitically to the LCLS-II FEL by extracting low intensity unused dark current bunches downstream of the FEL kickers. The DASEL key accelerator components include a 46-MHz gun laser system providing controlled intensity and timing of the dark current, a fast (MHz) kicker with 600-ns flat-top, a new transport line connecting the LCLS-II to the existing A-line and to End Station-A where the experiments will take place, and a spoiler and collimator system in the A-line for final shaping of the DASEL beam. An overview of the DASEL accelerator system is presented.

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TUPVA154

Project-Based Cooperative Learning in Accelerator Science and Technology Education

dipole, feedback, quadrupole, cavity

2458

G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
R.B. Appleby, G.X. Xia
UMAN, Manchester, United Kingdom
I.R. Bailey
Lancaster University, Lancaster, United Kingdom
J.A. Clarke, O.B. Malyshev, N. Marks, B.D. Muratori, M.W. Poole, Y.M. Saveliev, B.J.A. Shepherd
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
C.P. Welsch, A. Wolski
The University of Liverpool, Liverpool, United Kingdom

Funding: The work is funded by STFC via the Cockcroft Institute core grant.
The next generation of particle accelerators will require the training of greater numbers of specialist accelerator physicists and engineers . These physicists and engineers should have a broad understanding of accelerator physics as well as the technology used in particle accelerators as well as a specialist in some area of accelerator science and technology . Such specialists can be trained by combining a University based PhD, in collaboration with national laboratory training with a broad taught accelerator lecture program. In order to have a faster start we decided to run an intensive two week school to replace the basic course at the Cockcroft Institute. At the same time we decided to investigate the use of problem based learning to simulate the way accelerator science tends to work in practice. In this exercise he students worked in groups of 5 to design a 3rd generation light source from scratch based on photon light specifications. In comparison to similar design exercises we stipulate that all students must do all parts and students are not allowed to specialise. A comparison with a standard lecture based education programme is discussed in this paper.

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WEOCA3

Status of the Development of Superconducting Undulators at the Advanced Photon Source

undulator, photon, vacuum, storage-ring

2499

Y. Ivanyushenkov, C.L. Doose, J.F. Fuerst, E. Gluskin, Q.B. Hasse, M. Kasa, Y. Shiroyanagi
ANL, Argonne, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357
Superconducting planar undulator (SCU) technology has been developed and is currently in use at the Advanced Photon Source (APS). The experience of building and operating the first short-length, 16-mm period superconducting undulator, SCU0, paved the way for two 1-m long, 18-mm period devices, SCU18-1 and SCU18-2. The first of those undulators has been in operation since May 2015, while the second one replaced SCU0 in September 2016. The possibility of building planar SCUs with a high quality field has been demonstrated at the APS. The measured phase errors of SCU18-2 at the design operational current are only 2 degrees rms, for example. An FEL SCU prototype - a 1.5-m long, 21-mm period undulator - was also built and tested as part of an LCLS SCU R&D program. This undulator successfully achieved all LCLS-II undulator requirements including a phase error of 5 degrees rms. The superconducting undulator technology also allows the fabrication of circular polarizing devices. Currently, a new helical SCU is under construction at the APS. In addition, the concept of a novel Superconducting Arbitrarily Polarizing Emitter, or SCAPE, has been suggested and is now under development.

Slides WEOCA3 [2.826 MB]

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WEPAB015

Parameter Optimization for Operation of sFLASH With Echo-Enabled Harmonic Generation

laser, electron, operation, bunching

2592

J. Bödewadt, R.W. Aßmann, C. Lechner
DESY, Hamburg, Germany
W. Hillert, T. Plath, J. Roßbach
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
S. Khan, N.M. Lockmann
DELTA, Dortmund, Germany

The free-electron laser facility FLASH has a dedicated experimental setup for external FEL seeding applications for the XUV and soft x-ray spectral range. Recently the setup is operated as high-gain harmonic generation FEL. Furthermore, it also allows the operation of echo-enabled harmonic generation (EEHG). A versatile laser injection system allows operation with seed wavelength in the infra-red, visible, and ultra-violet. Here, we present the parameter optimization for operating the seeding setup with EEHG. First experimental tests are planned in the first half of 2017.

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WEPAB016

Experience in Operating sFLASH With High-Gain Harmonic Generation

laser, electron, radiation, photon

2596

J. Bödewadt, R.W. Aßmann, N. Ekanayake, B. Faatz, I. Hartl, T. Laarmann, C. Lechner, M.M. Mohammad Kazemi, A. Przystawik
DESY, Hamburg, Germany
Ph. Amstutz, A. Azima, M. Drescher, W. Hillert, L.L. Lazzarino, Th. Maltezopoulos, V. Miltchev, T. Plath, J. Roßbach
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
K.E. Hacker, S. Khan, N.M. Lockmann, R. Molo
DELTA, Dortmund, Germany

sFLASH, the experimental setup for external seeding of free-electron lasers (FEL) at FLASH, has been operated in the high-gain harmonic generation (HGHG) mode. A detailed characterization of the laser-induced energy modulation, as well as the temporal characterization of the seeded FEL pulses is possible by using a transverse deflecting structure and an electron spectrometer. FEL saturation was reached for the 7th harmonic of the 266 nm seed laser. In this contribution, we present the latest experimental results.

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WEPAB017

Generation of Ultra-Short Electron Bunches and FEL Pulses and Characterization of Their Longitudinal Properties at FLASH2

electron, operation, laser, undulator

2600

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

The free-electron laser in Hamburg (FLASH) is a user facility, delivering soft X-ray radiation, consisting of two beam lines, FLASH1 and FLASH2. The injector and the main linac are shared between both beam lines. Starting in 2014, FLASH2 has been commissioned for user operation. Currently, there is no hardware installed for the direct measurement of the electron bunch length nor the photon pulse duration at FLASH2. Exact knowledge of the pulse duration is essential for time-resolved user experiments performed at FLASH. Therefore, we are designing a modified beam line, containing a new type of X-band deflecting cavity* and a dipole, downstream of the FLASH2 undulator, to map the longitudinal phase space onto a beam screen. Anticipating the feasibility of measuring the longitudinal phase space with high resolution, a study on optimizing the free-electron laser (FEL) performance for shortest bunches is ongoing.
*B. Marchetti et al., X-Band TDS project, contribution to these conference proceedings

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WEPAB019

Concept for a Seeded FEL at FLASH2

electron, laser, undulator, free-electron-laser

2607

C. Lechner, R.W. Aßmann, J. Bödewadt, M. Dohlus, N. Ekanayake, B. Faatz, G. Feng, I. Hartl, T. Laarmann, T. Lang, L. Winkelmann, I. Zagorodnov
DESY, Hamburg, Germany
A. Azima, M. Drescher, Th. Maltezopoulos, T. Plath, J. Roßbach, W. Wurth
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
S. Khan
DELTA, Dortmund, Germany

The free-electron laser (FEL) FLASH is a user facility delivering photon pulses down to 4 nm wavelength. Recently, the second FEL undulator beamline 'FLASH2' was added to the facility. Operating in self-amplified spontaneous emission (SASE) mode, the exponential amplification process is initiated by shot noise of the electron bunch, resulting in photon pulses of limited temporal coherence. In seeded FELs, the FEL process is initiated by coherent seed radiation, improving the longitudinal coherence of the generated photon pulses. The conceptual design of a possible seeding option for the FLASH2 beamline foresees the installation of the hardware needed for high-gain harmonic generation (HGHG) seeding upstream of the already existing undulator system. In this contribution, we present the beamline design and numerical simulations of the seeded FEL.

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WEPAB021

Experience with Multi-Beam and Multi-Beamline FEL-Operation

laser, undulator, experiment, operation

2615

J. Rönsch-Schulenburg, B. Faatz, K. Honkavaara, M. Kuhlmann, S. Schreiber, R. Treusch, M. Vogt
DESY, Hamburg, Germany

DESY's free-electron laser FLASH provides soft X-ray pulses for scientific users at wavelengths down to 4 nm simultaneously in two undulator beamlines. They are driven by a common linear superconducting accelerator with a beam energy of up to 1.25 GeV. The superconducting technology allows the acceleration of electron bunch trains of several hundred bunches with a spacing of 1 microsecond or more and a repetition rate of 10 Hz. A fast kicker-septum system directs one part of the bunch train to FLASH1 and the other part to FLASH2 keeping the full 10 Hz repetition rate for both. The unique setup of FLASH allows independent FEL pulse parameters for both beamlines. In April 2016, simultaneous operation of FLASH1 and FLASH2 for external users started. This paper reports on our operating experience with this type of multi-beam, multi-beamline set-up.

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WEPAB022

Background-free Harmonic Production in XFELs via a Reverse Undulator Taper

undulator, background, radiation, electron

2618

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

Nonlinear harmonics in X-ray FELs can be parasitically produced as soon as FEL reaches saturation, or can be radiated in dedicated afterburners. In both cases there is a strong background at the fundamental, since it is much stronger than harmonics. One can get around this problem by application of the recently proposed reverse undulator tapering. In this contribution we present numerical simulations of harmonic production in such a configuration as well as recent results from FLASH where the second and the third harmonics were efficiently generated with a low background at the fundamental. We also present the results for a high-contrast operation when the afterburner is tuned to the fundamental.

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WEPAB023

First Operation of a Harmonic Lasing Self-Seeded FEL

undulator, electron, operation, brightness

2621

E. Schneidmiller, B. Faatz, M. Kuhlmann, J. Rönsch-Schulenburg, S. Schreiber, M. Tischer, M.V. Yurkov
DESY, Hamburg, Germany

Harmonic lasing is a perspective mode of operation of X-ray FEL user facilities that allows to provide brilliant beams of higher energy photons for user experiments. Another useful application of harmonic lasing is so called Harmonic Lasing Self-Seeded Free Electron Laser (HLSS FEL) that allows to improve spectral brightness of these facilities. In the past, harmonic lasing has been demonstrated in the FEL oscillators in infrared and visible wavelength ranges, but not in high-gain FELs and not at short wavelengths. In this paper we report on the first evidence of the harmonic lasing and the first operation of the HLSS FEL at the soft X-ray FEL user facility FLASH in the wavelength range between 4.5 nm and 15 nm. Spectral brightness was improved in comparison with Self-Amplified Spontaneous emission (SASE) FEL by a factor of six in the exponential gain regime. A better performance of HLSS FEL with respect to SASE FEL in the post-saturation regime with a tapered undulator was observed as well. The first demonstration of harmonic lasing in a high-gain FEL and at a short wavelength paves the way for a variety of applications of this new operation mode in X-ray FELs.

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WEPAB024

Commissioning and First Heating with the European XFEL Laser Heater

laser, undulator, electron, cathode

2625

M. Hamberg
Uppsala University, Uppsala, Sweden
F. Brinker, M. Scholz
DESY, Hamburg, Germany

Funding: We thank DESY and Swedish research council under Project number DNR-828-2008-1093 for financial support.
The Laser Heater of the European XFEL has been installed and commissioning is in progress. We discuss the setup and the results of the first electron beam heating in the injector section.

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WEPAB025

Status of the Soft X-Ray Free Electron Laser FLASH

laser, photon, experiment, operation

2628

M. Vogt, B. Faatz, K. Honkavaara, M. Kuhlmann, J. Rönsch-Schulenburg, S. Schreiber, R. Treusch
DESY, Hamburg, Germany

The superconducting free-electron laser user facility FLASH at DESY in Hamburg, routinely produces several thousand photon pulses per second. The operational parameters cover a wavelength range from 90 nm down to 4 nm with pulse energies from several uJ up to 1 mJ and with pulse durations of several hundred fs down to a few fs. The FLASH injector and linac drives two undulator beam lines (FLASH1, FLASH2) and therefore FLASH is capable of serving 2 independent experiments with photon pulse (sub-) trains of several 100 bunches at the full train repetition frequency of 10 Hz. We summarize here the highlights of the user operation at FLASH1/2 and the study program (machine development and FEL optimization) of the FLASH facility.

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WEPAB027

Frequency Doubler and Two-color Mode of Operation at Free Electron Laser FLASH2

undulator, radiation, electron, operation

2635

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

We report on the results of the first operation of a frequency doubler at free electron laser FLASH2. The scheme uses the feature of the variable gap undulator. Undulator is divided in two parts. The second part of the undulator is tuned to the double frequency of the first part. Amplification process in the first undulator part is stopped at the onset of the nonlinear regime, such that nonlinear higher harmonic bunching in the electron beam density becomes pronouncing, but the radiation level is still small to disturb the electron beam significantly. Modulated electron beam enters the second part of the undulator and generates radiation at the 2nd harmonic. Frequency doubler allows operation in a two-color mode and operation at shorter wavelengths with respect to standard SASE scheme. Tuning of the electron beam trajectory, phase shifters and compression allows to tune intensities of the first and the second harmonic. The shortest wavelength of 3.1 nm (photon energy 400 eV) has been achieved with frequency doubler scheme, which is significantly below the design value for the standard SASE option.

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WEPAB029

Optimum Undulator Tapering of SASE FEL: From the Theory to Experiment

undulator, electron, radiation, laser

2639

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

Optimization of the amplification process in FEL amplifier with diffraction effects taken into account results in a specific law of the undulator tapering [*]. It is a smooth function with quadratic behavior in the beginning of the tapering section which transforms to a linear behavior for a long undulator. In practice, undulator consists of a sequence of modules of fixed length separated with intersections. Two modes of undulator tapering can be implemented: step tapering, and smooth tapering. Procedure of the step tapering applies step change of the undulator gap from module to module, and smooth tapering assumes additional linear change of the gap along each module. In this report we simulate the performance of the both experimental options and compare with theoretical limit.
[*] E.A. Schneidmiller and M.V. Yurkov, Optimization of a high efficiency free electron laser amplifier, Phys. Rev. ST Accel. Beams 18 (2015) 030705.

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WEPAB031

OCELOT as a Framework for Beam Dynamics Simulations of X-Ray Sources

simulation, wakefield, space-charge, electron

2642

S.I. Tomin
XFEL. EU, Hamburg, Germany
I.V. Agapov, M. Dohlus, I. Zagorodnov
DESY, Hamburg, Germany

We describe the OCELOT open source project focusing on new beam dynamics simulation capabilities of the whole machine in modern electron-based x-ray sources. Numerical approaches for particle tracking and field calculations are discussed. In developing of the full-dimensional numerical modeling we pursue two important competitive aspects: the simulation has to be fast and has to include accurate estimations of collective effects. The simulation results for the European XFEL [1] are presented. The results have been benchmarked agains other codes and some of such benchmarks are shown.

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WEPAB033

Experimental Optimization and Characterization of Electron Beams for Generating IR/THz SASE FEL Radiation with PITZ

emittance, electron, simulation, radiation

2650

P. Boonpornprasert, Y. Chen, J.D. Good, H. Huck, I.I. Isaev, D.K. Kalantaryan, M. Krasilnikov, X. Li, O. Lishilin, G. Loisch, D. Melkumyan, A. Oppelt, H.J. Qian, Y. Renier, T. Rublack, F. Stephan
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
C. Saisa-ard
Chiang Mai University, Chiang Mai, Thailand
Q.T. Zhao
IMP/CAS, Lanzhou, People's Republic of China

The Photo Injector Test facility at DESY, Zeuthen site (PITZ), develops high brightness electron sources for modern linac-based Free Electron Lasers (FELs). The PITZ accelerator can also be considered as a suitable machine for the development of an IR/THz source prototype for pump-probe experiments at the European XFEL. One of the interesting options for the IR/THz generation with PITZ is to generate the radiation by means of a SASE FEL using an uncompressed electron beam with bunch length of a few 10 ps and a peak current of ~200 A. In this paper, results of experimental optimizations and characterizations, including transverse phase space, slice transverse emittance and longitudinal phase space, of electron beams with bunch charges of 4 nC are presented and discussed. The measurements were done with beam momenta of 15 MeV/c and 22 MeV/c. Results of IR/THz SASE FEL calculations by using the GENESIS1.3 code based on the measured beam parameters are also presented and discussed.

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WEPAB034

Control of Seeded FEL Pulse Duration Using Laser Heater Pulse Shaping

laser, electron, simulation, experiment

2654

V. Grattoni
Università degli Studi di Trieste, Trieste, Italy
E. Allaria, L. Badano, M.B. Danailov, A.A. Demidovich, S. Di Mitri, L. Giannessi, G. Penco, E. Roussel, P. Sigalotti, S. Spampinati, M. Trovò, M. Veronese
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
E. Ferrari
PSI, Villigen PSI, Switzerland

New Free-Electron Laser facilities deliver VUV and X-ray radiation with pulse length in the range of hundreds and tens of fs. A further reduction of the FEL pulse length is desired by those experiments aiming at probing ultrafast phenomena. Unlike SASE FEL, where the pulse duration is mainly driven by the electron bunch duration, in a seeded FEL the pulse duration can be determined by the seed laser properties. The use of techniques able to locally deteriorate the electron beam properties such as emittance or energy spread have been used in SASE FELs to reduce the region of the electron beam that is able to produce FEL radiation and hence reduce the FEL pulse length. The temporal shaping of the laser heater can be used to create an electron beam characterized by a very large energy spread all along the bunch except for a small region. We report measurements of the effect of the laser heater shaping on the electron beam phase-space performed at FERMI. Impact on the final FEL pulse properties are predicted with a series of numerical simulations.

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WEPAB037

Two-Bunch Operation at the FERMI FEL Facility

linac, wakefield, laser, electron

2663

G. Penco, E. Allaria, S. Bassanese, P. Cinquegrana, S. Cleva, M.B. Danailov, A.A. Demidovich, S. Di Mitri, M. Ferianis, G. Gaio, D. Gauthier, L. Giannessi, M. Predonzani, F. Rossi, E. Roussel, S. Spampinati, M. Trovò
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
L. Giannessi
ENEA C.R. Frascati, Frascati (Roma), Italy
E. Roussel
PhLAM/CERLA, Villeneuve d'Ascq, France

FERMI is a linac-driven free electron laser (FEL) based upon the High Gain Harmonic Generation (HGHG) scheme. In standard conditions a bunch of 700 pC of charge with sub mm-mrad emittances is accelerated to 1.2-1.5GeV in a normal conducting S-band linac and drives FEL-1 or FEL-2 undula-tor line, which lase respectively in the range 100-20nm or 20-4nm. A number of two-color schemes have been implemented at FERMI for pump/probe experiments, all consisting in making two portions of the same electron bunch lase at two different wavelengths, with a time-separation from 0 to few hundreds of fs. In order to increase the time separation to ns and tens of ns we have explored the acceleration of two inde-pendent electron bunches separated by multiple of the linac main radio-frequency period, i.e. 333ps. Measure-ments and characterization of this two-bunch mode oper-ation are presented, including trajectory control, impact of longitudinal and transverse wakefields on the trailing bunch and manipulation of the longitudinal phase space.

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WEPAB039

Development Perspectives at FERMI

laser, linac, electron, experiment

2666

M. Svandrlik, E. Allaria, L. Badano, F. Bencivenga, C. Callegari, F. Capotondi, F. Cilento, P. Cinquegrana, M. Coreno, I. Cudin, G. D'Auria, M.B. Danailov, R. De Monte, G. De Ninno, P. Delgiusto, A.A. Demidovich, M. Di Fraia, S. Di Mitri, B. Diviacco, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, P. Furlan Radivo, G. Gaio, D. Gauthier, F. Gelmetti, L. Giannessi, F. Iazzourene, 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. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

FERMI is the seeded Free Electron Laser (FEL) user facility at the Elettra laboratory in Trieste, operating in the ultraviolet to soft X-rays spectral range; the radiation produced by the seeded FEL is characterized by a number of desirable properties, such as wavelength stability, low temporal jitter and longitudinal coherence. In this paper, after an overview of the FEL performances, we will present the development plans under consideration for the next 3 to 5 years. These include an upgrade of the linac and of the existing FEL lines, the possibility to perform multipulse experiments in different configurations and an Echo Enabled Harmonic Generation (EEHG) experiment on FEL-2, the FEL line extending to 4 nm (310 eV).

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WEPAB058

Commissioning Status of the Dalian Cohernet Light Source

laser, electron, undulator, linac

2709

G.L. Wang
DICP, Dalian, People's Republic of China

The Dalian Coherent Light Source (DCLS) is a seeded FEL user facility working at 50-150 nm, now under commissioning in Dalian, China. The facility consists of a 300 MeV normal-conducting S-band linear accelerator (LINAC) and two undulator beamlines. The first beam-line (FEL-1) will provide picosecond FEL radiation with the pulse energy up to several hundreds micro-joule, the second beam-line (FEL-2) will be a femtosecond and polarization FEL. The LINAC and FEL-1 beam-line construction was complete by the summer of 2016, the installation of FEL-2 is in preparation. High power RF conditioning of the LINAC started in August 2016 and the beam commissioning initiated 3 months later. This article describes the commissioning status of DCLS, reports on the goals achieved so far.

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WEPAB065

Proposal for the Generation of Terawatt, Attosecond X-Ray Pulses in Free Electron Lasers

undulator, radiation, laser, electron

2723

Z. Wang, C. Feng, Z.T. Zhao
SINAP, Shanghai, People's Republic of China

A feasible novel method is proposed to generate attosecond terawatt X-ray radiation pulse in free electron lasers, which could find its application on multiple science fields. In our scheme, a chirped laser is employed to generate a chirped periodic current enhancement and a series of spatiotemporal shifters are applied between the undulator sections to generate ultra-short radiation pulse. Three-dimensional start-to-end simulations are carried out and the calculation results show that a 0.15nm X-ray pulse with the peak power of about 1TW and the pulse length of 0.1fs could be achieved in our scheme.

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WEPAB066

POP Experiment for the HB-HGHG Scheme at SXFEL

electron, laser, radiation, free-electron-laser

2727

K.S. Zhou, H.X. Deng, C. Feng, D. Wang
SINAP, Shanghai, People's Republic of China

Abstract High brightness, fully coherent and ultra-short free electron lasers (FEL) operating in the soft x-ray region are opening up new frontiers in many scientific fields. In this paper, we perform the design studies for the proof-of-principle experiment of the recently proposed HB-HGHG scheme at SXFEL test facility with a two-stage setup. The first stage of SXFEL is used for the generation of the coherent signal at 30th harmonic of the seed through the coherent harmonic generation process. Then this coherent signal is shifted ahead by the 'fresh bunch' chicane of SXFEL and initiates the strong coherent radiation in the radiator of the second stage of SXFEL. The output properties have been compared with the conventional EEHG and the two-stage cascaded HGHG with the same harmonic up-conversion number.

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WEPAB070

Study of ESASE Scheme with Microbunching Instability for Generating Attosecond-Terawatt X-Ray Pulse in XFELs

laser, electron, simulation, free-electron-laser

2741

C.H. Shim, D.E. Kim, I.S. Ko
POSTECH, Pohang, Kyungbuk, Republic of Korea
Y.W. Parc
PAL, Pohang, Kyungbuk, Republic of Korea

Recent studies show that the attosecond-terawatt X-ray pulse in XFELs can be generated by using ESASE (enhanced self-amplified spontaneous emission) scheme to obtain a sub-femtosecond spike in the electron peak current. However, ESASE scheme is not working properly when the microbunching instability is taken into account. The instability can be suppressed when the laser heater system which increases the uncorrelated energy spread of the electron beam is used in the injector. The effect of the microbunching instability on the performance of ESASE scheme will be discussed. In addition, the optimized results with the laser heater system for generating attosecond-terawatt X-ray pulse in XFELs is also presented.

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WEPAB074

On the Coherence Properties of FEL

laser, undulator, simulation, experiment

2753

M.A. Pop, F. Curbis, S. Werin
MAX IV Laboratory, Lund University, Lund, Sweden

Free Electron Lasers (FEL) are one of the most brilliant light sources in the world and their unique properties are driving worldwide research in understanding and improving them. Numerous papers have already been published describing the output of the FEL in terms of coherence and bandwidth. In this contribution, however, we focus on how the coherence evolves along the FEL undulator and on what factors influence it the most. Using Genesis⁻¹.3* we have been able to follow and record the light field as it is being produced in the undulator. Our analysis method takes advantage of the extensively studied double pinhole experiment and uses the principles behind it to create a tool for extracting coherence information from the radiation field. We will present the scope, limitations and advantages of these virtual experiments as well as an application on an example FEL, to showcase what kind of information can be extracted using this method.
* Numerical simulation code used for particle and field distribution tracking along the undulator developed by Sven Reiche

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WEPAB077

The Soft X-Ray Laser Project at MAX IV

laser, undulator, electron, linac

2760

S. Werin, J. Andersen, F. Curbis, L. Isaksson, M. Kotur, F. Lindau, E. Mansten, D. Olsson, H. Tarawneh, P.F. Tavares, S. Thorin
MAX IV Laboratory, Lund University, Lund, Sweden
S. Bonetti, A. Nilsson
Stockholm University, Stockholm, Sweden
V.A. Goryashko
Uppsala University, Uppsala, Sweden
P. Johnsson
Lund University, Lund, Sweden
M. Larsson, P. Salén
FYSIKUM, AlbaNova, Stockholm University, Stockholm, Sweden
O. Tjernberg
KTH Physics, Stockholm, Sweden

A soft x-ray laser beamline utilising FEL technology is being designed for the Short Pulse Facility (SPF) at the MAX IV Laboratory. A conceptual design study has been started following on the scientific case already prepared in collaboration between several Swedish Universities and driven by a strong (Swedish) user demand [*]. The baseline goal of the SXL beamline is to generate intense and short pulses in the range 1-5 nm (1-0.2 keV). The system is building on the MAX IV linac system, already today providing 3 GeV and pulses compressed to 100 fs for other applications within the SPF. As a special feature we foresee a variety of pump-probe capabilities. We here describe design issues and solutions for the accelerator and FEL system.
* http://frielektronlaser.se/onewebmedia/SXL_science_case₁61102.pdf

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WEPAB083

Development of Linac-Based MIR/THz FEL Facility and Photocathode RF-gun in Thailand

electron, undulator, laser, gun

2763

K. Buakor, N. Chaisueb, K. Damminsek, S. Rimjaem, J. Saisut, C. Thongbai, W. Thongpakdi
Chiang Mai University, Chiang Mai, Thailand

A linac-based MIR/THz free-electron laser facility is under the development at the Plasma and Beam Physics Research Facility, Chiang Mai University. The ultimate goal of the project is to generate the infrared radiation covering the wavelengths from 13 to 125 μm. The main applications of the radiation involved MIR/THz imaging and spectroscopy. The future FEL facility will consists of an injector system, an experimental station for coherent transition radiation, two magnetic bunch compressors and two undulator magnets equipped with optical cavities for MIR and THz beamlines. An expected electron beam energy is between 10 to 20 MeV with an energy spread of about or less than 1 %. Two undulator magnets with maximum undulator parameters of 1 and 0.95 will be used for generation of the THz-FEL and MIR-FEL, respectively. In this paper, we present the status of the design and construction of this future FEL facility.

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WEPAB084

Development of Injector System for MIR/THz Free-Electron Laser Facility in Thailand

electron, gun, undulator, simulation

2767

W. Thongpakdi, S. Rimjaem
Chiang Mai University, Chiang Mai, Thailand

Development of a linac-based MIR/THz FEL light source is ongoing at the Plasma and Beam Physics Research Facility, Chiang Mai University. The future facility will consist of an S-band thermionic cathode RF electron gun, a pre-magnetic bunch compressor in a form of alpha magnet, an S-band travelling-wave linac structure, a 180-degree achromat system and two undulator magnets equipped with optical cavities. This research focuses on start-to-end beam dynamics simulations of the injector system. The aim of the study is to produce high quality electron beam at the entrance of the THz undulator magnet. The simulation was conducted by using programs PARMELA and ELEGANT. The program PARMELA was utilized to study the electron beam dynamics inside the RF-gun. Then, the program ELEGANT was used to optimize the injector system parameters. Optimization of physical specifications for the achromat system was performed to obtain short electron bunches with small energy spread at the undulator entrance. In this paper, results of beam dynamics simulations with suitable condition for the THz-FEL beamline are presented and discussed.

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WEPAB087

TARLA: The First Facility of Turkish Accelerator Center (TAC)

electron, cavity, laser, linac

2776

A.A. Aksoy, A.A. Aydin, C. Kaya
Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey
B. Ketenoğlu, O. Yavaş
Ankara University, Faculty of Engineering, Tandogan, Ankara, Turkey

Funding: Work supported by Ministry of Development of Turkey
Turkish Accelerator and Radiation Laboratory in Ankara (TARLA) is proposed as first accelerator based infrastructure in Turkey as a first step Turkish Accelerator Center (TAC). The facility under construction at Institute of Accelerator Technologies of Ankara University since 2012. Based superconducting technology, TARLA accelerator will offer a multi-experiment facility providing various accelerator-based radiation sources for the users coming from different fields like physics, chemistry, biology, material sciences, medicine and nanotechnology. Two of the planed free-electron laser (FEL) beamlines of TARLA will provide Continuous Wave (CW) tunable radiation of high brightness in the mid- and far-infrared regime. In addition a Bremmstrahlung radiation station is proposed within current scope of TARLA. In this paper current status of facility is presented.

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WEPAB089

Design Study for the Generation of Few-Cycle FEL Pulses Using Mode-Locked Afterburner Scheme at Clara

bunching, laser, simulation, radiation

2783

C.L. Shurvinton, D.J. Dunning, N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Ultrashort pulse operation in FELs is a highly desirable capability for imaging matter on ultrafast timescales. This paper presents a design study for a proof-Âof-Âprinciple demonstration of the mode-locked afterburner (ML-AB) scheme on the FEL test facility CLARA. A start-to-end simulation has been constructed using the time-Âdependent three-Âdimensional FEL code GENESIS 1.3 to evaluate the performance of the scheme. The ability to produce pulses of several femtoseconds in duration with peak powers of the order of 100 MW at 100 nm wavelength is predicted.Â Such pulses have duration of 2 fs (6 optical cycles), a factor of ~5 shorter than the FEL cooperation length. Potential routes for further optimisation and alternative operating modes are explored.

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WEPAB090

Developments in the CLARA FEL Test Facility Accelerator Design and Simulations

laser, undulator, simulation, optics

2787

P.H. Williams, D.J. Dunning, N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, 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. The requirement to co-propagate the beam with laser seeds of very different wavelengths has led to a redesign of the section preceding the undulators, with a dogleg being replaced by a chicane. Additional refinements of the facility design include the inter-undulator sections. With this finalised design we show start to FEL simulations for all beam modes envisaged.

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WEPAB097

Modelling Two-Colour FEL with Wide Wavelength Separation and Individual Polarisation Tuning

polarization, undulator, simulation, electron

2808

D. Bultrini, N. Thompson
Cockcroft Institute, Warrington, Cheshire, United Kingdom
R.J. Allan
The Hartree Centre, Science and Technology Facilities Council (STFC/DL), Warrington, United Kingdom
L.T. Campbell, B.W.J. MᶜNeil
USTRAT/SUPA, Glasgow, United Kingdom
D.J. Dunning, N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
J.D.A. Smith
TXUK, Warrington, United Kingdom

Free electron lasers (FELs) are currently enabling cutting edge research in chemistry, biology and physics. We use simulations to assess a new FEL capability that would add to the impressive repertoire of experiments made possible by the technology: a two-colour independent polarization mode, which allows for light pulses with variable temporal separation, individually tuneable polarisation, and widely separated wavelength. Simulations are carried out using the broad bandwidth FEL code Puffin, the results of which are used to discuss the radiation properties of the output. This scheme is applicable to existing and proposed facilities which feature undulators with variable ellipticity and gap.

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WEPAB108

Angular Trajectory Kicks in a High-Gain Free-Electron Laser

electron, radiation, laser, free-electron-laser

2830

P. Baxevanis, Z. Huang, G. Stupakov
SLAC, Menlo Park, California, USA

In a free-electron laser (FEL), transverse momentum offsets (or kicks) are introduced either inadvertently (through wakefields or mis-steering of the electron beam) or as part of dedicated schemes that require off-axis radiation propagation. Studying the influence of this effect on the performance of machines such as LCLS-I/II is critical both from a tolerance point of view and for its practical applications. A theoretical analysis of a high-gain FEL driven by such a kicked beam will be presented, with a critical evaluation of previous studies.

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WEPAB109

Multipole Field Effects in a Transverse Gradient Undulator

undulator, multipole, electron, simulation

2833

P. Baxevanis, Z. Huang
SLAC, Menlo Park, California, USA

Using a transverse gradient undulator (TGU) is one of the methods proposed in order to enable the utilization of electron beams with large energy spread (such as those from plasma-based accelerators) in a free-electron laser (FEL). Most of the analytical treatments of this scheme assume a linear variation of the undulator field with one of the transverse coordinates. While this assumption leads to a simplified and more tractable model, including higher-order multipoles allows us to offer a more complete and rigorous description of the system. In this paper, we investigate the magnetic field components of a TGU using both theory and simulation and explore the impact of higher-order multipoles on the FEL performance.

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WEPAB116

LCLS Injector Laser Shaping and Applications

laser, electron, cathode, emittance

2844

S. Li, S.C. Alverson, D.K. Bohler, A.B. Egger, A.R. Fry, S. Gilevich, Z. Huang, A. Miahnahri, D.F. Ratner, J. Robinson, F. Zhou
SLAC, Menlo Park, California, USA

In the Linear Coherent Light Source (LCLS) at SLAC, the injector laser plays an important role as the source of the electron beam for the Free Electron Laser (FEL). The beam emittance and FEL performance are highly related to the transverse shape of the injector laser. When the injector laser has hot spots and non-uniformities that can carry over to the electron beam and degrade electron emittance and FEL performance, it requires long hours of manual adjustment by laser engineers and strenuous machine tuneup. The injector laser shaping project at LCLS aims to have precise control of the driver laser transverse profile in order to produce arbitrary electron beam profiles, which will enable us to study effects of laser shape on beam emittance and FEL performances. We use a digital micromirror device (DMD) to manipulate the drive laser profile. In this paper, we briefly discuss the implementations of laser shaping at LCLS. We demonstrate two applications of laser shaping. We present results of using laser shaping to control the X-ray laser output via an online optimizer. We also show the photocathode quantum efficiency measurements across cathode surface using the DMD.

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WEPIK100

The Applicability of NEG Coated Undulator Vessels for the CLARA FEL Test Facility

vacuum, wakefield, undulator, impedance

3181

O.B. Malyshev, K.B. Marinov, K.J. Middleman, N. Thompson, R. Valizadeh, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
O.B. Malyshev, K.J. Middleman, N. Thompson, R. Valizadeh, P.H. Williams
Cockcroft Institute, Warrington, Cheshire, United Kingdom

CLARA is a FEL test facility at Daresbury Laboratory (DL), UK. The undulator vacuum chamber is 20 m long with inner diameter 6 mm and its vacuum performance can benefit from a NEG coating. The thickness of the coating layer must be carefully optimised. A layer ~ 1 um would help the vacuum but a thinner layer would be partially transparent for the EM field reducing the resistive wall wakefields due to the NEG. A very thin layer, however, may not yield the necessary vacuum performance. Two types of NEG coatings produced at DL - dense and columnar - were considered. Their bulk conductivities were measured in a separate study. The resistive wall wakefield impedance was calculated following the standard approach for multilayer vessels. A 250 fs rms electron bunch was generated in ASTRA and its wakefield was obtained from the vessel impedance. The FEL performance was then studied through GENESIS simulations and the result compared to the case with no wakefields. It was found that NEG layers thicker than 100 nm give an unacceptable reduction of the FEL power and the vacuum performance of such thin coatings is unknown. Possible solutions to this problem are discussed.

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WEPIK113

Entrance and Exit CSR Impedance for Non-Ultrarelativistic Beam

impedance, wakefield, dipole, bunching

3214

R. Li
JLab, Newport News, Virginia, USA
C.-Y. Tsai
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA

Funding: Work supported by the Department of Energy, Laboratory Directed Research and Development Funding, under Contract No. DE-AC05-06OR23177
For a high-brightness electron beam being transported through beamlines involving bending systems, the coherent synchrotron radiation (CSR) and longitudinal space charge (LSC) interaction could often cause microbunching instability. The semi-analytical Vlasov solver for microbunching gain* depends on the impedances for the relevant collective effects. The existing results for CSR impedances are usually obtained for the ultrarelativistic limit. To extend the microbunching analysis to cases of low energies, such as the case of an ERL merger, or to density modulations at extremely small wavelength, it is necessary to extend the impedance analysis to the non-ultrarelativistic regime. In this study, we present the impedance analysis for the transient CSR interaction in the non-ultrarelativistic regime, for transients including both entrance to and exit from a magnetic dipole. These impedance results will be compared to their ultra-relativistic counterparts**, and the corresponding wakefield obtained from the impedance for low-energy beams will be compared with the existing results of transient CSR wakefield for general beam energies***.
* C.-Y. Tsai et al., Proc. of IPAC'15, 596 (2015).
** C. Mitchell et al ., Proc. of IPAC'13, 1832 (2014).
*** E. L. Saldin et al ., Nucl. Instrum. Meth. A 398, 373 (1997).

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WEPVA021

Phase Space Manipulation of Sub-Picosecond Electron Bunches Using Dielectric Wakefield Structures

emittance, wakefield, simulation, electron

3302

T.H. Pacey, G.X. Xia
UMAN, Manchester, United Kingdom
D.J. Dunning, Y.M. Saveliev
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Dielectric lined waveguides have drawn interest due to their application as high gradient accelerating structures, in both externally driven and wakefield schemes. We present simulation studies of sub-picosecond electron bunches interacting with dielectric structures in the self-wake regime. The parameter space for a tunable, sub-millimeter aperture, terahertz frequency structure is investigated. The potential application as a longitudinal phase space dechirper is demonstrated, with specific application to CLARA at Daresbury Laboratory. The impact of transverse effects is considered and minimised. The resulting FEL output is simulated.

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WEPVA052

The Infrastructure for the Elettra Sincrotrone Trieste

storage-ring, linac, operation, laser

3375

D. Zangrando, D. Baron, A. Buonanno, A. Galimberti, A. Martinolli, M. Miculin, D. Morelli
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

Elettra - Sincrotrone Trieste S.C.p.A. is a multidisciplinary international laboratory, specialized in generating high quality synchrotron and free-electron laser light and applying it in materials science. The main assets of the research centre are two advanced light sources, the electron storage ring Elettra and the free-electron laser (FEL) FERMI, continuously (H24) operated supplying light of the selected colour and quality to more than 30 experimental stations. In this paper, we are giving an overview on the status of the infrastructure plants devoted to ensuring the operation of Elettra and FERMI machines. We will also analyse the systems that mostly have impacted on the performance of both accelerators and their downtime.

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THYA1

New Scenarios of Microbunching Instability Control in Electron Linacs and Free Electron Lasers

electron, laser, linac, controls

3642

E. Roussel, E. Allaria, M.B. Danailov, S. Di Mitri, E. Ferrari, D. Gauthier, L. Giannessi, G. Penco, M. Veronese
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

Laser-heater systems are essential tools to control and optimize high-gain free-electron lasers (FELs) working in the x-ray wavelength range. Indeed, these systems induce a controllable increase of the energy spread of the electron bunch. The heating suppresses longitudinal microbunching instability which otherwise would limit the FEL performance. We demonstrate that, through the action of the microbunching instability, a long-wavelength modulation of the electron beam induced by the laser heater at low energy can persist until the beam entrance into the undulators. This coherent longitudinal modulation is exploited to control the FEL spectral properties, in particular, multicolor extreme-ultraviolet FEL pulses can be generated through a frequency mixing of the modulations produced by the laser heater and the seed laser in the electron beam. We present an experimental demonstration of this novel configuration carried out at the FERMI FEL.
*E. Roussel et al., Phys. Rev. Lett. 115, 214801 (2015)

Slides THYA1 [14.837 MB]

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THPAB014

An Adaptive Mesh-Based Method for the Efficient Simulation of LSC-Driven Microbunching Gain in FEL Applications

electron, bunching, acceleration, simulation

3720

Ph. Amstutz
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
M. Vogt
DESY, Hamburg, Germany

Electron beams with high peak current as they are required for the operation of free-electron lasers (FELs) are often generated by means of a series of magnetic bunch compressors. In conjunction with a collective coherent force, e.g. longitudinal space-charge (LSC), bunch compressors can possibly cause a wavelength dependent amplification of initial density inhomogeneities, potentially to an extent detrimental to the operation of the FEL. A common model, consisting of LSC, acceleration (kicks), and magnetic chicanes (drift-type maps), is governed by a time-discrete Vlasov-Poisson system. Such systems have been successfully simulated using mesh based representations of the phase space density (PSD) and the method of characteristics for the update step. However, for the irregular and exotic PSDs, prevalent in FEL applications, a homogeneous high resolution discretization on a naive rectangular mesh can be prohibitively wasteful. Here we present an approach based on adaptive tree refinement that addresses the complexity of the PSDs and allows for the efficient simulation of LSC-driven micro-bunching in FELs.

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THPAB036

An Experimental Study of Beam Dynamics in the ERL-Based Novosibirsk Free Electron Laser

radiation, diagnostics, electron, synchrotron

3781

V.M. Borin, L.M. Schegolev, O.A. Shevchenko, N.A. Vinokurov
BINP SB RAS, Novosibirsk, Russia
V.L. Dorokhov, O.I. Meshkov
BINP, Novosibirsk, Russia

Transverse and longitudinal dynamics of the electron beam of the Novosibirsk infrared Free Electron Laser is studied. The Novosibirsk FEL is based on the multi-turn energy recovery linac (ERL). The ERL operate in CW mode with an average current about 10 mA. Therefore non-destructive beam diagnostics is preferable. The beam energy at the last track of the ERL is 42 MeV. As a result, significant part of synchrotron radiation from bending magnets is in the visible range. The transverse beam dimensions were measured with the optical diagnostics before and after the undulator applied for generation of middle-infrared coherent radiation. The obtained data is used to calculate the beam energy spread and emittance. The longitudinal beam dynamics was studied with electro-optical dissector.

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THPAB053

Laser Heater Deisgn for the CLARA FEL Test Facility

laser, undulator, electron, dipole

3833

A.D. Brynes, S.P. Jamison, B.D. Muratori, N. Thompson, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
S.P. Jamison, B.D. Muratori, N. Thompson, P.H. Williams
Cockcroft Institute, Warrington, Cheshire, United Kingdom

We present considerations of microbunching studies in the CLARA (Compact Linear Accelerator for Research and Applications), the proposed UK FEL test facility under construction at Daresbury Laboratory. CLARA, a high-brightness electron linac, presents an opportunity to study the microbunching instability. A number of theoretical models have been proposed concerning the causes of this instability, and it has also been observed at various FEL facilities. We have applied these models to the CLARA FEL, and propose a suitable laser heater design which will provide flexibility in terms of the range of modes of operation for CLARA. We also propose a method for inducing and controlling the microbunching instability via pulse stacking of the photoinjector laser.

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THPAB078

Beam Dynamics Studies of the Transverse Gradient Undulator and Its Application to Suppression of Microbunching Instability

electron, undulator, focusing, laser

3895

T. Liu, Y. Ding, Z. Huang, W. Qin
SLAC, Menlo Park, California, USA
T. Liu
University of Chinese Academy of Sciences, Beijing, People's Republic of China
T. Liu, D. Wang
SINAP, Shanghai, People's Republic of China

A transverse gradient undulator (TGU) which was initially proposed for high gain free electron lasers (FELs) driven by electron beams with relatively large energy spread, can be extended to the application of beam dynamics, such as phase-merging enhanced harmonic generation FEL and suppression of microbunching instability. In this contribution we present beam dynamics studies of the TGU, analyze the resulting focusing and dispersion, and discuss the effects of an additional corrector on the TGU. As an application to beam dynamics, we show a feasible transport system based on the TGU as a reversible electron beam heater to suppress the microbunching instability of the electron beam.

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THPAB105

Design and Operation of the Integrated 1.3 GHz Optical Reference Module with Femtosecond Precision

laser, detector, controls, operation

3963

T. Lamb, L. Butkowski, E.P. Felber, M. Felber, M. Fenner, S. Jabłoński, T. Kozak, J.M. Müller, P. Prędki, H. Schlarb, C. Sydlo, M. Titberidze, F. Zummack
DESY, Hamburg, Germany

In modern Free-Electron Lasers like FLASH or the European XFEL, the short and long-term stability of RF reference signals gains in importance. The requirements are driven by the demand for short FEL pulses and low-jitter FEL operation. In previous publications, a novel, integrated Mach-Zehnder Interferometer based scheme for a phase detector between the optical and the electrical domain was presented and evaluated. This Laser-to-RF phase detector is the key component of the integrated 1.3 GHz Optical Reference Module (REFM-OPT) for FLASH and the European XFEL. The REFM-OPT will phase-stabilize 1.3 GHz RF reference signals to the pulsed optical synchronization systems in these accelerators. Design choices in the final hardware configuration are presented together with measurement results and a performance evaluation from the first operation period in the European XFEL.

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THPAB108

Femtosecond Optical Synchronization System for the European XFEL

laser, timing, free-electron-laser, electron

3969

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

Accurate timing synchronization on the femtosecond timescale is an essential installation for time-resolved experiments at free-electron lasers (FELs) such as FLASH and the upcoming European XFEL. Conventional RF timing systems suffer from RF attenuation for such long distances and have reached to date a limit for synchronization precision of around 100 femtoseconds. An optical synchronization system is used at FLASH and is based on the distribution of femtosecond laser pulses over actively stabilized optical fibers. The upcoming European XFEL has raised the demands due to its large number of stabilized optical fibers and a length of 3400 m. The increased lengths for the stabilized optical fibers necessitated major advancement in precision to achieve the requirement of less than 10 femtosecond precision. This paper reports on the status of the laser-based synchronization system at the European XFEL.

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THPAB110

Custom Optomechanics for the Optical Synchronization System at the European XFEL

laser, timing, alignment, coupling

3976

F. Zummack, M. Felber, C. Gerth, T. Lamb, J.M. Müller, M. Schäfer, H. Schlarb, C. Sydlo
DESY, Hamburg, Germany

Free-electron-lasers like the upcoming European XFEL demand highly reliable optical synchronization in range of few femtoseconds. The well known optical synchronization system at FLASH had to be re-engineered to meet XFEL requirements comprising demands like ten times larger lengths and raised numbers of optically synchronized instruments. These requirements directly convert to optomechanical precision and have yielded in a specialized design accounting for economical manufacturing technologies. These efforts resulted in reduced spatial dimensions, improved optical repeatability, maintainability and even reduced production costs. To account for thermal influences the heart of the optical synchronization system is based on an optical table made out of SuperInvar. To fully exploit its excellent thermal expansion coefficient, mechanical details need to be taken into account. This work presents the design and its realization of the re-engineered optomechanical parts of the optical synchronization system, comprising mounting techniques, link stabilization units and optical delay lines for high drift suppression.

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THPAB123

Low Level RF Control System Architecture OF IR-FEL

controls, LLRF, electron, klystron

4014

B. Du, G. Huang, L. Lin, W. Liu, Z.R. Zhou
USTC/NSRL, Hefei, Anhui, People's Republic of China

Infrared free electron laser (IR-FEL) is one type of laser driven by accelerator and generated by undulator. It is built by National Synchrotron Radiation Laboratory (NSRL). Compared to synchrotron radiation light source, it have much higher demand of beam quality. Low level RF control system (LLRF) need to reach higher controlled accuracy corresponded to the demand. Accelerating structure which contains one pre-buncher, one buncher and two accelerating tube can accelerate beam to 60MeV. Frequency distribution system use direct digital synthesizer technology to generate 5 signal of different frequency. LLRF system detect 8 channels signal, one for control loop, and the others for monitor and interlock. The hardware contain MTCA.4 architecture which is advanced in global; RF board for downconverter and IQ modulation output; DSP board for sampling, controller and transmission.

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THPAB124

DSP Frame and Algorithm of LLRF of IR-FEL

feedback, LLRF, controls, target

4017

B. Du, G. Huang, L. Lin, W. Liu, Z.R. Zhou
USTC/NSRL, Hefei, Anhui, People's Republic of China

Infrared Free Electron Laser (IR-FEL) use linear accelerator to accelerate electron to relative speed and then generate simulated radiation of infrared wavelength by periodic magnetic field of undulator. The amplitude and phase of microwave field need to be controlled precisely by low level RF control system (LLRF) to meet the high quality demand of electron from undulator. This paper mainly introduce the digital signal processing frame and feedback algorithm. Four times frequency sampling can realize IQ demodulation precisely and reduce DC offset, amplitude sampling error is less than 0.075% and phase sampling error is less than 0.1°. Pipeline CORDIC can calculate amplitude and phase by parallel processing and shift operation. Phase calculating accuracy reach 0.0005° when iteration count is 18. FIR filter is used to improve frequency selected performance. Feedback loop use digital PI controller to adjust system output.

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THPAB128

Beam Arrival Time Analisis Based on CBPM at DCLS

simulation, cavity, experiment, undulator

4023

S.S. Cao, J. Chen, L.W. Lai, Y.B. Leng
SINAP, Shanghai, People's Republic of China
N. Zhang
SSRF, Shanghai, People's Republic of China

Dalian Coherent Light Source is the first high gain free electron lasers (FEL) user facility in China, which is dedicated at extreme ultraviolet (EUV) spectral regime of 150-50nm for various scientific fields. In its undulator section, the beam-line was equipped with ten pair of high-precision cavity beam position monitor (CBPM), which can be used for beam position and beam arrival time (BAT) measurement. Based on this, we have done some preliminary research about the beam fight time with the reference cavities of CBPMs for the future research on BAT. In this paper, we presented the scheme of the beam fight time (BFT) research, analyzed the results, and evaluated the consistency and stability of BFT.

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THPIK038

Design of a 100 kW Solid-State RF Pulse Amplifier with a TE011 Mode RF Combiner at 476 MHz

cavity, electron, klystron, laser

4180

Y. Otake, T. Asaka, T. Inagaki
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

Solid-state RF amplifiers, which have long lifetimes and small failures, are the recent current of high-power RF sources for particle accelerators. Hence, we designed a 100 kW solid-state amplifier with a TE011 mode cavity (Q0=100, 000) power combiner with extreme low-loss operated at 476 MHz and a 6 us pulse width. Developing this amplifier is for replacement of a high-power amplifier using an induction output tube, IOT, in the X-ray free-electron laser, SACLA. In SACLA, highly RF phase and amplitude stabilities of less than 0.01 deg. and 10^-4 in rms are necessary to stable lasing within a 10 % intensity fluctuation. The amplifier comprises a drive amplifier, a reentrant cavity RF power divider, 100 final amplifier modules with a 1 kW output each and a TE011 mode cavity combiner. Water-cooling within 10 mK and a DC power supply with a noise of less than -100 dBV at 10 Hz for the amplifier is necessary to realize the previously mentioned stabilities. Based on the experimental results of a test amplifier module and test combiner cavities, possibility to realize the above-mentioned specifications is large. We report the detail and a part of the performance of the 100 kW amplifier.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK038

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FRXBB1

Novosibirsk Four-Orbit ERL With Three FELs

electron, radiation, undulator, gun

4836

N.A. Vinokurov, V.S. Arbuzov, K.N. Chernov, I.V. Davidyuk, O.I. Deichuli, E.N. Dementyev, B.A. Dovzhenko, Ya.V. Getmanov, Ya.I. Gorbachev, B.A. Knyazev, E.I. Kolobanov, A.A. Kondakov, V.R. Kozak, E.V. Kozyrev, S.A. Krutikhin, V.V. Kubarev, G.N. Kulipanov, E.A. Kuper, I.V. Kuptsov, G.Y. Kurkin, L.E. Medvedev, S.V. Motygin, V.N. Osipov, V.K. Ovchar, V.M. Petrov, A.M. Pilan, V.M. Popik, V.V. Repkov, T.V. Salikova, M.A. Scheglov, I.K. Sedlyarov, S.S. Serednyakov, O.A. Shevchenko, A.N. Skrinsky, S.V. Tararyshkin, V.G. Tcheskidov, A.G. Tribendis, P. Vobly, V. Volkov
BINP SB RAS, Novosibirsk, Russia
I.V. Davidyuk, Ya.V. Getmanov, B.A. Knyazev, E.V. Kozyrev, S.S. Serednyakov, N.A. Vinokurov
NSU, Novosibirsk, Russia
A.G. Tribendis
NSTU, Novosibirsk, Russia

The Novosibirsk FEL facility has three FELs, installed on the first, second and fourth orbits of the ERL. The first FEL covers the wavelength range of 90 - 240 mkm at an average radiation power of up to 0.5 kW with a pulse repetition rate of 5.6 or 11.2 MHz and a peak power of up to 1 MW. The second FEL operates in the range of 40 - 80 mkm at an average radiation power of up to 0.5 kW with a pulse repetition rate of 7.5 MHz and a peak power of about 1 MW. These two FELs are the world's most powerful (in terms of average power) sources of coherent narrow-band (less than 1%) radiation in their wavelength ranges. The third FEL was commissioned in 2015 to cover the wavelength range of 5 - 20 mkm. The Novosibirsk ERL is the first and the only multiturn ERL in the world. Its peculiar features include the normal-conductive 180 MHz accelerating system, the DC electron gun with the grid thermionic cathode, three operation modes of the magnetic system, and a rather compact (6×40 m2) design. The facility has been operating for users of terahertz radiation since 2004.

Slides FRXBB1 [51.485 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-FRXBB1

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