MOP —  Poster Session   (24-Aug-15   15:00—17:00)

Paper	Title	Page
MOP004	Influence of Horizantal Constant Magnetic Field on Harmonic Undulator Radiations and Gain	34
	H. Jeevakhan, P.K. Purohit NITTTR, Bhopal, India G. Mishra Devi Ahilya University, Indore, India
	Harmonic undulators has been analyzed in the presence of constant magnetic field along the direction perpendicular to the main undulator field. Effect of constant magnetic field magnitude on trajectory of electron beam , intensity of radiation and FEL gain at fundamental and third harmonics has been evaluated. Performance of harmonic undulator in the presence horizontal component of earth's magnetic field is the practical realization of the suggested scheme.
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MOP008	Theoretical Computation of the Polarization Characteristics of an X-Ray Free-Electron Laser with Planar Undulator	38
	G. Geloni XFEL. EU, Hamburg, Germany V. Kocharyan, E. Saldin DESY, Hamburg, Germany
	We show that radiation pulses from an X-ray Free-Electron Laser (XFEL) with a planar undulator, which are mainly polarized in the horizontal direction, exhibit a suppression of the vertical polarization component of the power at least by a factor λw2/(4 pi Lg)2, where λw is the length of the undulator period and Lg is the FEL field gain length. We illustrate this fact by examining the XFEL operation under the steady state assumption. In our calculations we considered only resonance terms: in fact, non resonance terms are suppressed by a factor λw3/(4 pi Lg)3 and can be neglected. While finding a situation for making quantitative comparison between analytical and experimental results may not be straightforward, the qualitative aspects of the suppression of the vertical polarization rate at XFELs should be easy to observe. We remark that our exact results can potentially be useful to developers of new generation FEL codes for cross-checking their results.
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MOP009	Efficient Electron Sources of Coherent Spontaneous Radiation with Combined Helical and Uniform Magnetic Fields	43
	N. Balal, V.L. Bratman, E. Magori Ariel University, Ariel, Israel V.L. Bratman IAP/RAS, Nizhny Novgorod, Russia
	We discuss two methods to mitigate repulsion of particles in dense electron bunches from photo-injectors and to enhance the power of terahertz radiation. First, the repulsion may be reduced with both very short bunches and undulator periods, reducing the length of a radiation section. According to simulations bunches with duration (50-100) fs, charge (50-200) pC, and energy 6 MeV could fairly effectively radiate at frequencies up to (10-20) THz. The undulator for such a source can be formed by means of redistribution of a solenoid field by a non-magnetized iron helix and a permanently magnetized helix. The second source is based on an idea proposed by A.V. Savilov for electron bunching under conditions when the cyclotron electron frequency is larger than the undulator frequency, and an increase of particle energy in the bunch Coulomb field leads to a decrease in longitudinal momentum and attraction of particles (this effect is analogous to the cyclotron negative-mass instability). A large value of the required uniform field can be used to easily obtain the needed undulator field by placing a simple iron helix inside a pulsed solenoid. Simulations confirm that the corresponding particle attraction can provide a powerful and narrowband radiation at the frequencies (1-3) THz.
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MOP010	Linac Design of the IR-FEL Project in CHINA	46
	Z.G. He, Q.K. Jia, L. Wang, W. Xu, S.C. Zhang USTC/NSRL, Hefei, Anhui, People's Republic of China
	We are building an infrared free-electron laser (IR-FEL) facility that will operate from 5 um to 200 um. This FEL source is drived by a linac, which is composed of a triode electron gun, a subharmonic prebuncher, a buncher, two accelerators, and a beam transport line. The linac is required to operate from 15 to 60 MeV at 1 nC charge, while delivering a transverse rms emittance of smaller than 30 mm-mrad in a 5 ps rms length, smaller than 240 keV rms energy spread bunch at the Far-infrared and Mid-infrared undulators. In this article, the preliminary Linac design studies are described.
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MOP011	Status of CLARA, a New FEL Test Facility	49
	J.A. Clarke, D. Angal-Kalinin, A.D. Brynes, R.K. Buckley, S.R. Buckley, L.S. Cowie, D.J. Dunning, B.D. Fell, P. Goudket, A.R. Goulden, P.C. Hornickel, F. Jackson, S.P. Jamison, J.K. Jones, K.B. Marinov, P.A. McIntosh, J.W. McKenzie, K.J. Middleman, B.L. Militsyn, A.J. Moss, B.D. Muratori, M.D. Roper, L.K. Rudge, Y.M. Saveliev, B.J.A. Shepherd, R.J. Smith, S.L. Smith, E.W. Snedden, M. Surman, T.T. Thakker, N. Thompson, R. Valizadeh, A.E. Wheelhouse, P.H. Williams STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom R.B. Appleby, K. Hanahoe, O. Mete Apsimon, H.L. Owen, G.X. Xia UMAN, Manchester, United Kingdom P. Atkinson, N. Bliss, R.J. Cash, N.A. Collomb, G. Cox, G.P. Diakun, S. Dobson, A. Gallagher, S.A. Griffiths, C. Hill, C. Hodgkinson, D.M.P. Holland, T.J. Jones, B.G. Martlew, J. Williams STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom R. Bartolini, I.P.S. Martin DLS, Oxfordshire, United Kingdom S.T. Boogert, E. Yamakawa Royal Holloway, University of London, Surrey, United Kingdom G. Burt, P.N. Ratoff Lancaster University, Lancaster, United Kingdom L.T. Campbell, A.J.T. Colin, J. Henderson, B. Hidding, B.W.J. MᶜNeil USTRAT/SUPA, Glasgow, United Kingdom A.M. Kolano University of Huddersfield, Huddersfield, United Kingdom A. Lyapin JAI, Egham, Surrey, United Kingdom V.V. Paramonov, A.K. Skasyrskaya RAS/INR, Moscow, Russia J.D.A. Smith TXUK, Warrington, United Kingdom S. Spampinati Cockcroft Institute, Warrington, Cheshire, United Kingdom Y. Wei, C.P. Welsch, A. Wolski The University of Liverpool, Liverpool, United Kingdom
	CLARA is a new FEL test facility being developed at STFC Daresbury Laboratory in the UK. The main motivation for CLARA is to test new FEL schemes that can later be implemented on existing and future short wavelength FELs. Particular focus will be on ultra-short pulse generation, pulse stability, and synchronisation with external sources. The project is now underway and the Front End section (photoinjector and first linac) installation will begin later this year. This paper will discuss the progress with the Front End assembly and also highlighting other topics which are currently receiving significant attention.
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MOP012	Present Status of Source Development Station at UVSOR-III	54
	N.S. Mirian, K. Hayashi, M. Katoh, J. Yamazaki UVSOR, Okazaki, Japan M. Hosaka, Y. Takashima Nagoya University, Nagoya, Japan T. Konomi, N. Yamamoto KEK, Ibaraki, Japan H. Zen Kyoto University, Kyoto, Japan
	Construction and development of a source development station are in progress at UVSOR-III, a 750 MeV electron storage ring. It is equipped with an optical klystron type undulator system, a mode lock Ti:Sa Laser system, a dedicated beam-line for visible-VUV radiation and a parasitic beam-line for THz radiation. New light port to extract edge radiation was constructed recently. An optical cavity for a resonator free electron laser is currently being reconstructed. Some experiments such as coherent THz radiation, coherent harmonic radiation, laser Compton Scattering gamma-rays and optical vortices are in progress.
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MOP013	The Fermi Seeded FEL Facility: Operational Experience and Future Perspectives	57
	L. Giannessi, E. Allaria, L. Badano, F. Bencivenga, C. Callegari, F. Capotondi, D. Castronovo, P. Cinquegrana, M. Coreno, R. Cucini, I. Cudin, G. D'Auria, M.B. Danailov, R. De Monte, G. De Ninno, P. Delgiusto, A.A. Demidovich, S. Di Mitri, B. Diviacco, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, E. Ferrari, P. Finetti, P. Furlan Radivo, G. Gaio, D. Gauthier, F. Gelmetti, F. Iazzourene, M. Kiskinova, S. Krecic, M. Lonza, N. Mahne, M. Manfredda, C. Masciovecchio, M. Milloch, F. Parmigiani, E. Pedersoli, G. Penco, L. Pivetta, O. Plekan, M. Predonzani, K.C. Prince, E. Principi, L. Raimondi, P. Rebernik Ribič, F. Rossi, E. Roussel, L. Rumiz, C. Scafuri, C. Serpico, P. Sigalotti, M. Svandrlik, C. Svetina, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	FERMI is the seeded FEL user facility in Trieste, Italy, producing photons from the VUV to the soft X-rays with a high degree of coherence and spectral stability. Both FEL lines, FEL-1 and FEL-2, are available for users, down to the shortest wavelength of 4 nm. We report on the completion of the commissioning of the high energy FEL line, FEL-2, on the most recent progress obtained on FEL-1 and on the operational experience for users, in particular those requiring specific FEL configurations, such as two-colour experiments. We will also give a perspective on the improvements and upgrades which have been triggered based on our experience, aiming to maintain as well as to constantly improve the performance of the facility for our user community.
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MOP014	Status of the Soft X-Ray FEL User Facility FLASH	61
	K. Honkavaara, B. Faatz, J. Feldhaus, S. Schreiber, R. Treusch, M. Vogt DESY, Hamburg, Germany
	Since 10 years FLASH at DESY (Hamburg, Germany) has provided high brilliance FEL radiation at XUV and soft X-ray wavelengths for user experiments. Recently FLASH has been upgraded with a second undulator beamline, FLASH2, whose commissioning takes place in parallel of the user operation on FLASH1. This paper summarizes the performance of the FLASH facility during the last user period from January 2014 to April 2015.
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MOP016	Status of the Fabrication of PAL-XFEL Magnet Power Supplies	66
	S.-H. Jeong, Y.-G. Jung, H.-S. Kang, D.E. Kim, I.S. Ko, H.-G. Lee, S.B. Lee, B.G. Oh, K.-H. Park, H.S. Suh PAL, Pohang, Kyungbuk, Republic of Korea
	PAL-XFEL has been constructing including a 10 GeV linac, hard X-ray and soft X-ray branches. PAL-XFEL required for about six hundreds of magnet power supply (MPS). The eight different prototypes of MPS are developing to confirm the performance, functions, size, heat load and so on. This paper describes the test results of the prototype MPS in major specifications. All MPSs have to be installed the end of September in 2015. The installation progress of the MPS was also described.
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MOP017	Beam Commissioning Plan for the SwissFEL Hard-X-Ray Facility	69
	T. Schietinger PSI, Villigen PSI, Switzerland
	The SwissFEL facility currently being assembled at the Paul Scherrer Institute is designed to provide FEL radiation in the photon wavelength range between 0.1 and 7 nm. The commissioning of the first phase, comprising the electron injector, the main electron linear accelerator and the first undulator line, named Aramis and dedicated to the production of hard X-rays, is planned for the years 2016 and 2017. We present an overview of the beam commissioning plan elaborated in accordance with the installation schedule to bring into operation the various subsystems and establish beam parameters compatible with first pilot user experiments in late 2017.
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MOP018	Comparison of Astra Simulations With Beam Parameter Measurements at the Kaeri Ultrashort Pulse Facility	74
	H.W. Kim, I.H. Baek, M.S. Chae, B.A. Gudkov, B. Han, K.H. Jang, Y.U. Jeong, Y. Kim, K. Lee, S.V. Miginsky, S. H. Park, S. Park, S. Setiniyaz, N. Vinokurov KAERI, Daejon, Republic of Korea K.H. Jang, Y.U. Jeong, H.W. Kim, K. Lee, S.V. Miginsky, S. H. Park, N. Vinokurov University of Science and Technology of Korea (UST), Daejeon, Republic of Korea S.V. Miginsky, N. Vinokurov BINP SB RAS, Novosibirsk, Russia
	An RF-photogun-based linear accelerator for ultra-short electron beam generation is under construction at Korea Atomic Energy Research Institute (KAERI). This facility are mainly composed of an 1.5 cell S-band (2856 MHz) RF gun, a travelling wave type linac 3 m long and 90-degree achromatic bends. The emitted electron beams are accelerated in high RF field to ~ 3 MeV. The electrons can be deflected by a first bending magnet installed right after the RF gun. Each beamline has second bending magnet similar to the first one and three quadrupoles between the bending magnets. Two bending and three quadrupole magnets compose the 90-degree achromatic bend. The deflected electron beams will be used for ultrafast electron diffraction (UED) experiments. We have performed computer simulation using ASTRA code to investigate the electron beam dynamics in the system with the input data of bead tested gun electric field distribution and the magnetic fields of the magnets. We will present the simulated and experimental electron beam parameters.
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MOP021	LCLS-II Injector Beamline Design and RF Coupler Correction	77
	F. Zhou, D. Dowell, R.K. Li, T.O. Raubenheimer, J.F. Schmerge SLAC, Menlo Park, California, USA C.E. Mitchell, C. F. Papadopoulos, F. Sannibale LBNL, Berkeley, California, USA A. Vivoli Fermilab, Batavia, Illinois, USA
	Funding: U.S. DOE contract #DE-AC02-76SF00515. LCLS-II CW injector beamline consists of a 186 MHz normal conducting (NC) RF gun for beam generation and acceleration to 750 keV, two solenoids for the beam focusing, two BPMs, 1.3 GHz NC RF buncher for bunch compression down to 3-4 ps rms, 1.3 GHz superconducting standard 8-cavity cryomodule to boost beam energy to about 98 MeV. The beamline is being optimized to accommodate all essential components and maximize beam quality. The beamline layouts and beam dynamics are presented and compared. The 3D RF field perturbation due to cavity couplers where the beam energy is very low (<1 MeV) causes significant emittance growth especially for a large-size beam. A theory of rotated fields predicted and simulations verified using a weak skew quadrupole located even a significant distance from the perturbation can completely eliminate the emittance growth. A layout for future upgrade is developed. The results are presented and analysed.
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MOP024	Status, Plans and Recent Results from the APEX Project at LBNL	81
	F. Sannibale, K.M. Baptiste, C.W. Cork, S. De Santis, M.R. Dickinson, L.R. Doolittle, J.A. Doyle, J. Feng, D. Filippetto, G.L. Harris, G. Huang, R. Huang, M.J. Johnson, M.S. Jones, T.D. Kramasz, S. Kwiatkowski, D. Leitner, R.E. Lellinger, C.E. Mitchell, V. Moroz, W.E. Norum, H.A. Padmore, G.J. Portmann, H.J. Qian, J.W. Staples, D. L. Syversrud, M. Vinco, S.P. Virostek, R.P. Wells, M.S. Zolotorev LBNL, Berkeley, California, USA R. Huang USTC/NSRL, Hefei, Anhui, People's Republic of China
	Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231 The Advanced Photo-injector EXperiment (APEX) at the Lawrence Berkeley National Laboratory (LBNL) is dedicated to the demonstration of the capability of an electron injector based on the VHF-gun, the new concept RF gun developed at LBNL, of delivering the beam quality required by MHz-class repetition rate X-Ray free electron lasers. Project status, plans, and recent results are presented.
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MOP025	Electron Beam Properties from a Compact Seeded Terahertz FEL Amplifier at Kyoto University	85
	K. Damminsek, S. Rimjaem, S. Suphakul, C. Thongbai Chiang Mai University, Chiang Mai, Thailand H. Ohgaki, H. Zen Kyoto University, Kyoto, Japan
	A compact seeded Terahertz FEL amplifier is started construction at Institute of Advanced Energy, Kyoto University, Japan. The system consists of a 1.6 cell BNL type S-Band photocathode RF-gun, a magnetic bunch compressor in form of a chicane, triplet quadrupole magnets and a short planar undulator. Electron beams from the photocathode RF-gun were measured and compared with the PARMELA simulation results. Numerical and experimental studies on the contribution of the space charge effect were carried out. By using the RF power of 9 MW, the RF phase of 40 degree, the laser pulse energy of 20 μJ, and the solenoid magnet current of 135 A, the electron beam with a bunch charge of 50 pC, a beam energy of around 5 MeV and an RMS emittance of 6-8 mm-mrad was achieved.
	Poster MOP025 [1.837 MB]
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MOP029	PAL XFEL Pulse Modulator System Test Results Using a High Precision CCPS	89
	S.H. Kim, H.-S. Kang, G.H. Kim, I.S. Ko, S.J. Kwon, H.-S. Lee, S.S. Park, Y.J. Park PAL, Pohang, Kyungbuk, Republic of Korea M.-H. Cho POSTECH, Pohang, Kyungbuk, Republic of Korea K.Y. Jang, H.S. Shin POSCO ICT, Gyeonggi-do, Republic of Korea D.S. Kim, S.Y. Lee, M. Seo Dawonsys, Siheung-City, Republic of Korea
	PAL XFEL is supposed to install 51 units of the pulse modulator power supplies for a 10-GeV linear accelerator using S-band (2856 MHz) cavities. The requirements of the modulator stability really become very tight. The stability on beam voltage is required to be less than 50 ppm. In order to obtain the high precision stability from the modulator system, we have newly produced a capacitor charging power supply (CCPS) and obtained the target stability with 10 ppm (STD) accuracy from measuring PFN (Pulse Forming Network). The CCPS generates a maximum output voltage of 50 kV at average current of 2.4 A with 4 units of the CCPS. The modulator peak output capacity is 400 kV, 500 A and 7.5 us at a pulse repetition rate of 60 pps using CCPS, a modified type-E PFN, and a pulse transformer. In this paper, the test results of the modulator system will be described.
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MOP030	Study of Smith-Purcell Free Electron Laser Using Electron Bunch Produced By Micro-Pulse Electron Gun	93
	J. Zhao, X.Y. Lu, W.W. Tan, D.Y. Yang, Y. Yang, Z.Q. Yang PKU, Beijing, People's Republic of China
	A Micro-Pulse electron Gun (MPG) with the frequency of 2856 MHz has been designed, constructed and tested. Some primary experimental studies have been carried out and electron beam with the average current of 6 mA has been detected which holds promise to use as an electron source of Smith-Purcell Free Electron Laser (SP-FEL) to produced Coherent Radiation. It is well known that Smith-Purcell radiation is one of the achievable ways to produce FEL. After many years study in theory and experiment, lots of new mechanisms and appearances have been discovered. Coherent Smith-Purcell Radiation was discovered in 1990s as well. Compared with incoherent Smith-Purcell Radiation, It can generate a more powerful and frequency locked coherent emission due to displaying all three of these enhancements, Ng (the number of grating periods), Ne (the number of electrons in the bunch), Nb (the number of electron bunch). Obviously, MPG is one of ideal electron sources of CSPR for that (1) S-band electron source can increase energy density at these frequencies, (2) picosecond or subpicosecond pulse can generate THz radiation, (3) low emittance makes the interactions between electron beam and granting more stable. All of the above will be displayed in the simulation of this article. The progress of the experiment with beam energy of 80 Kev, the average current of 6 mA is also introduced.
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MOP033	Numerical Simulations of a Sub-THz Coherent Transition Radiation Source at PITZ	97
	P. Boonpornprasert, M. Krasilnikov, F. Stephan DESY Zeuthen, Zeuthen, Germany B. Marchetti DESY, Hamburg, Germany
	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 be considered as a proper machine for the development of an IR/THz source prototype for pump and probe experiments at the European XFEL. For this reason, the radiation generated by high-gain FEL and Coherent Transition Radiation (CTR) produced by the PITZ electron beam has been studied. In this paper, numerical simulations on the generation of CTR based on the PITZ accelerator are presented. The beam dynamics simulations of electron bunches compressed by velocity bunching are performed by using the ASTRA code. The characteristics of CTR are calculated numerically by using the generalized Ginzburg-Frank formula. The details and results of the simulations are described and discussed.
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MOP034	Beam Optics Measurements at FERMI by using Wire-Scanner	101
	G. Penco, A. Abrami, I. Cudin, S. Di Mitri, M. Ferianis, E. Ferrari, G. Gaio, L. Giannessi, S. Grulja, R. Sauro, L. Sturari Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy E. Ferrari Università degli Studi di Trieste, Trieste, Italy L. Giannessi ENEA C.R. Frascati, Frascati (Roma), Italy G.L. Orlandi, C. Ozkan Loch PSI, Villigen PSI, Switzerland
	Measuring and controlling the electron beam optics is an important ingredient to guarantee high performance of a free-electron laser. In the FERMI linac, the Twiss parameters and the transverse emittances are routinely measured by detecting the beam spot size as a function of a scanning quadrupole placed upstream (i.e. quadrupole scan method). The beam spot size is usually measured with an OTR screen that unfortunately suffers from coherent optical transition radiation (C-OTR) that introduces spurious light and corrupts the image. Moreover, the beam size at the end of the FERMI linac is focused to a few tens of microns and this makes it difficult to precisely measure it with the OTR system, which has an estimated resolution of 20um. For this reason, a wire-scanner system has been installed at the end of the linac just in the waist of the optics channel. The wire-scanner is a SwissFEL prototype installed in FERMI in order to study the hardware and beam loss monitor performances at the GeV energy scale. The beam optics measurements performed with the wire-scanner is here presented, and the obtained results are more in agreement with the theoretical expectations. A more reliable beam optics estimation at the end of the linac has allowed to better match it to the nominal lattice and transport it up to the undulator chain, providing important benefits to the FEL performance.
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MOP036	Femtosecond Synchronization of 80-MHz Ti:Sapphire Photocathode Laser Oscillator with S-Band RF Oscillator	105
	H. Yang, C. Jeon, K. Jung, J. Kim KAIST, Daejeon, Republic of Korea H. Chung Korea University Sejong Campus, Sejong, Republic of Korea B. Han, Y.U. Jeong KAERI, Daejon, Republic of Korea
	Precision synchronization between lasers and RF sources in free-electron lasers (FELs) and ultrafast electron diffraction (UED) systems is becoming more important. There have been intense research and development toward femtosecond synchronization of lasers and RF sources in the last decade. Most of the previous approaches at large-scale FELs have used cw lasers or low-jitter mode-locked lasers at telecomm wavelength as the master oscillator and distributed the timing signals via stabilized fiber links. However, for smaller-scale FELs and UED, this approach may be a complex and high-cost method. In this work, we studied the possibility of using the commercial Ti:sapphire photocathode laser as the optical master oscillator as well. For its use in UED and FELs, we synchronized the 80-MHz Ti:sapphire photocathode laser oscillator to a 2.856-GHz RF source (used for RF-photogun) with 50-fs precision. Some interesting findings are following. First, intrinsic rms timing jitter of the used photocathode laser is 2.6 fs [10 kHz-10 MHz], which sets the fundamental limit in synchronization. Second, timing jitter in 100 Hz-1 kHz in photocathode laser is so severe (e.g., ~40 fs even feedback control is applied), so that it will require additional external-cavity control for achieving sub-10-fs precision. By addressing this issue, we are currently working toward 10-fs precision.
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MOP038	Stabilization of Magnetron Frequency for a Microtron-Driven FEL	107
	B.A. Gudkov, S. Bae, K.H. Jang, Y.U. Jeong, H.W. Kim, K. Lee, S.V. Miginsky, J. Mun, S. H. Park, G.I. Shim, N. Vinokurov KAERI, Daejon, Republic of Korea S.V. Miginsky, N. Vinokurov BINP SB RAS, Novosibirsk, Russia
	Under KAERI WCI program we develop a compact pulsed microtron-driven FEL. Electron bunches trains are accelerated in the microtron and transported by the beamline to the undulator. The RF cavity in the microtron is fed by a magnetron. Any accelerator driver for a FEL should provide an electron beam having very stable parameters such as electron energy, current, and especially the bunch repetition rate in a train. All mentioned parameters depend on magnetron current. It means that special attention should be paid for the shape of the current pulse, supplied to the magnetron from the modulator. We developed the modulator project with a computer control that will provide an arbitrary shape of the magnetron current. A simplified prototype was fabricated and tested. The methods of controlling of the pulse shape are considered. Simulation and experimental results are presented.
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MOP039	First Results of Commissioning of the PITZ Transverse Deflecting Structure	110
	H. Huck, P. Boonpornprasert, A. Donat, J.D. Good, M. Groß, I.I. Isaev, L. Jachmann, D.K. Kalantaryan, M. Khojoyan, W. Köhler, G. Kourkafas, M. Krasilnikov, D. Malyutin, D. Melkumyan, A. Oppelt, M. Otevřel, M. Pohl, Y. Renier, T. Rublack, J. Schultze, F. Stephan, G. Trowitzsch, G. Vashchenko, R.W. Wenndorff, Q.T. Zhao DESY Zeuthen, Zeuthen, Germany G. Asova INRNE, Sofia, Bulgaria M. A. Bakr Assiut University, Assiut, Egypt D. Churanov, L.V. Kravchuk, V.V. Paramonov, I.V. Rybakov, A.A. Zavadtsev, D.A. Zavadtsev RAS/INR, Moscow, Russia C. Gerth, M. Hoffmann, M. Hüning DESY, Hamburg, Germany C. Hernandez-Garcia JLab, Newport News, Virginia, USA M.V. Lalayan, A.Yu. Smirnov, N.P. Sobenin MEPhI, Moscow, Russia O. Lishilin, G. Pathak Uni HH, Hamburg, Germany
	For successful operation of X-ray Free Electron Lasers, one crucial parameter is the ultrashort electron bunch length yielding a high peak current and a short saturation length. In order to effectively compress the bunches during the acceleration process, a detailed understanding of the full longitudinal phase space distribution already in the injector is required. Transverse deflecting RF structures (TDS) can shear the bunch transversely, mapping the longitudinal coordinate to a transverse axis on an observation screen downstream. In addition to the bunch length, the slice emittance along the bunch as well as the full longitudinal phase space can be obtained. At the Photo Injector Test Facility at DESY, Zeuthen site (PITZ), an S-band traveling wave TDS is under commissioning since 2015. This cavity is a prototype for the TDS in the injector part of the European XFEL and has been designed and manufactured by the Institute for Nuclear Research (INR, Moscow, Russia). In this paper, first commissioning results of the system at PITZ are presented and discussed.
	Poster MOP039 [0.893 MB]
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MOP040	Implementation of MTCA.4-based Controls for the Pulsed Optical Synchronization Systems at DESY	115
	M. Felber, Ł. Butkowski, M.K. Czwalinna, M. Fenner, C. Gerth, M. Heuer, E. Janas, M. Killenberg, T. Lamb, U. Mavrič, J.M. Müller, P. Peier, K.P. Przygoda, S. Ruzin, H. Schlarb, C. Sydlo, M. Titberidze, F. Zummack DESY, Hamburg, Germany T. Kozak, P. Prędki TUL-DMCS, Łódź, Poland
	Funding: This work has partly been funded by the Helmholtz Validation Fund Project MTCA.4 for Industry (HVF-0016) With the current state of the synchronization system at FLASH (Free-electron Laser in Hamburg) the arrival time between electron bunches and optical laser pulses can be synchronized to a level of 30 fs rms, e.g. for pump-probe experiments. In the course of the development of an up-scaled system for the European XFEL and the migration of control hardware to the modern MTCA.4 (Micro Telecommunications Computing Architecture) platform, all involved components of the system will be replaced with new developments. The front-end devices are upgraded. FPGAs (Field Programmable Gate Arrays) are performing the data processing and feedback calculations. In order to facilitate the firmware development, a toolset (Rapid-X) was established which allows application engineers to develop, simulate, and generate their code without help from FPGA experts in a simple and efficient way. A software tool kit (MTCA4U) provides drivers and tools for direct register access e.g. via Matlab or Python and a control system adapter, which allows the server applications to be written control system independent. In this paper, an overview on the synchronization setups and their upgrades as well as an introduction to the new hardware is given. The Rapid-X and MTCA4U tool kits are presented followed by a status report on the implementation of the new developments.
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MOP041	Turbo-ICT Pico-Coulomb Calibration to Percent-level Accuracy	118
	F. Stulle, J.F. Bergoz BERGOZ Instrumentation, Saint Genis Pouilly, France
	We report on the calibration methods implemented for the Turbo-ICT/BCM-RF. They allow to achieve percent-level accuracy for charge and current measurements. Starting from the Turbo-ICT/BCM-RF working principle, we discuss scientific fundaments of calibration and their practical implementation in a test bench. Limits, both principle and practical, are reviewed. Achievable accuracy is estimated.
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MOP042	All-Fiber Approach to Long-Term Stable Timing Distribution System	122
	M. Xin, K. Safak, F.X. Kaernter DESY, Hamburg, Germany P.T. Callahan, M.Y. Peng MIT, Cambridge, Massachusetts, USA
	High precision timing distribution systems are critical for free-electron lasers (FELs). Real facilities such as FLASH and the European XFEL need fiber networks consisting of 20 or more timing links, which require tremendous attention to the alignment and stability of the free-space optics to minimize timing-drifts induced by beam pointing instabilities. This situation also necessitates preamplification of the master laser output to overcome excessive free-space to fiber coupling losses to provide adequate power for all timing links. Recently, we have developed integrated, fiber-coupled balanced optical cross-correlators (FC-BOC) using periodically-poled KTiOPO4 (PPKTP) waveguides. These waveguides exhibit second harmonic conversion efficiencies 20 times higher than the bulk optical devices, which will decrease the power demand from the master laser and consequently support more timing links. Furthermore, the robustness and ease of implementation of these fiber-coupled devices will eliminate alignment-related problems observed in free-space optics. In this paper, we present an all-fiber implementation of a 3.5-km timing distribution system using FC-BOCs, over 200 hours operation without interruption. The remaining drift (<1 Hz) is only 3.3 fs RMS, and the integrated jitter above 1 Hz is kept below 0.7 fs, which is more than sufficient for an efficient FEL synchronization.
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MOP043	Influence of Environment Changes on Libera Sync 3 Long-term Stability	126
	S. Zorzut, M. Cargnelutti I-Tech, Solkan, Slovenia S. Hunziker PSI, Villigen PSI, Switzerland
	Libera Sync 3 can be used as a reference clock transfer system in the latest fourth generation light sources where the long-term stability is in the range of a few tens of femtoseconds of drift per day. The system has been developed in collaboration with the Paul Scherrer Institute (PSI) and first units are already tested in SwissFEL machine. In this article we present the influence of temperature and humidity changes on the long-term phase stability of the system.
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MOP044	A Laser Heater for CLARA	129
	S. Spampinati Cockcroft Institute, Warrington, Cheshire, United Kingdom B.D. Muratori, N. Thompson, P.H. Williams STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	CLARA is a new FEL test facility, being developed at STFC Daresbury Laboratory in UK, based on a high brightness electron linac. The electron beam of CLARA can potentially be affected by the longitudinal microbunching instability leading to a degradation of the beam quality. The inclusion of a laser heater in the linac design can allow control of the microbunching instability, the study of microbunching and deliberate increase of the final energy spread to study energy spread requirements of the FEL schemes tested at CLARA. We present the initial design and layout of the laser heater system for CLARA and its expected performance.
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MOP047	The BINP HLS to Measure Vertical Changes on PAL-XFEL Buildings and Ground	133
	H. J. Choi, K.H. Gil, H.-S. Kang, S.H. Kim, K.W. Seo PAL, Pohang, Kyungbuk, Republic of Korea
	PAL-XFEL is being installed and will be completed by December of 2015 so that users can be supported beginning in 2016. PAL-XFEL equipment should continuously maintain the bunch beam parameter. To this end, PAL-XFEL equipment has to be kept precisely aligned. As a part of the process for installing PAL-XFEL, a surface geodetic network and the installation of a tunnel measurement network inside buildings is in preparation; additionally, the fiducialization of major equipment is underway. After PAL-XFEL equipment is optimized and aligned, if the ground and buildings go through vertical changes during operation, misalignment of equipments will cause errors in the electron beam trajectory, which will lead to changes to the beam parameter. For continuous and systemic measurement of vertical changes in buildings and to monitor ground subsidence (sinks) and uplift, the BINP Ultrasonic-type Hydrostatic Levelling System (HLS) is to be installed and operated in all sections of PAL-XFEL for linear accelerator, undulator and beam line. This study will introduce the operation principle, design concept and advantages (self-calibration) of BINP ULS Sensor, and will outline its installation plan and operation plan.
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MOP048	The Design of Low Noise Magnet Power Supply	136
	K.-H. Park, S.-H. Jeong, Y.-G. Jung, D.E. Kim, H.-G. Lee, S.B. Lee, B.G. Oh, H.S. Suh PAL, Pohang, Kyungbuk, Republic of Korea W.S. Choi, I.S. Ko POSTECH, Pohang, Kyungbuk, Republic of Korea
	The accelerator needs a high stable magnet power supply(MPS) with low noise output. The stability requirements of the some MPSs in accelerator were in the range of the ~10 ppm. There are many noise sources which affect the stability of MPS. Thus the design of the MPS requests much attention on the noise reduction scheme from the beginning stage. The noise on the MPS divided into some sources such as the ripple voltage coming from rectifier for the DC link, switching noise at the FET or IGBT on the high voltage, noise coming digital logics around DSP and its peripheral circuits, ground matters on the analogue signal process and so on. This paper analyzed the noise sources and described the way how to build the low noise power supply.
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MOP049	Design, Development and Test of the Magnets for PAL-XFEL	139
	H.S. Suh, M.-H. Cho, S.-H. Jeong, Y.-G. Jung, H.-S. Kang, D.E. Kim, I.S. Ko, H.-G. Lee, S.B. Lee, B.G. Oh, K.-H. Park PAL, Pohang, Kyungbuk, Republic of Korea
	PAL-XFEL is now being constructed with the goal of 0.1 nm hard X-ray in Pohang, Korea. As the first phase we will construct 10 GeV linac, one hard X-ray and one soft X-ray beamlines which require 6 different families of 55 dipole magnets, 11 families of 209 quadrupole magnets, and 3 families of 48 corrector magnets. We have designed these magnets with considering the efficient production and the proper power supplies. This paper describes an outline of the design and test results of the magnets until now.
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MOP050	Development of Coherent Terahertz Wave Sources using LEBRA and KU-FEL S-band Linacs	143
	N. Sei, H. Ogawa AIST, Tsukuba, Ibaraki, Japan K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Sakai, T. Tanaka LEBRA, Funabashi, Japan H. Ohgaki, H. Zen Kyoto University, Kyoto, Japan
	Funding: This work is supported by the "ZE Research Program, IAE ZE27B-6". In an infrared free-electron laser (FEL) facility using an S-band linac, a short-bunched electron beam is required to obtain a high FEL gain. Generally, the bunch length of the electron beam is compressed to 1 ps or less before interaction with the photons accumulated in the FEL resonator. This suggests that the electron beam dedicated to the FEL oscillation is suitable for generation of high-peak-power coherent radiation in terahertz (THz) wave region. Using the compressed electron beams, the coherent THz-wave sources have been developed at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University and Kyoto University Free Electron Laser (KU-FEL). The observed powers have been higher than 100 micro-joule per macropulse*. In this presentation, the properties of the high-power coherent THz waves generated at the bending magnets will be reported. * N. Sei et al., J. Opt. Soc. Am. B 31 (2014) 2150.
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MOP052	Linear Vlasov Solver For Microbunching Gain Estimation with Inclusion of CSR, LSC, And Linac Geometric Impedances	147
	C.-Y. Tsai Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA D. Douglas, R. Li, C. Tennant JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. As is known, microbunching instability (MBI) has been one of the most challenging issues in designs of magnetic chicanes for short-wavelength free-electron lasers or linear colliders, as well as those of transport lines for recirculating or energy recovery linac machines. To more accurately quantify MBI in a single-pass system, we further extend and continue to increase the capabilities of our previously developed linear Vlasov solver [1] to incorporate more relevant impedance models into the code, including transient and steady-state free-space and/or shielding CSR impedances, the LSC and linac geometric impedances with extension of the existing formulation to include beam acceleration [2]. Then, we directly solve the linearized Vlasov equation numerically for microbunching gain amplification factor. In this study we apply this code to a beamline lattice of transport arc [3] following an upstream linac section. The resultant gain functions and spectra are presented here, and some results are compared with particle tracking simulation by ELEGANT [4]. We also discuss some underlying physics with inclusion of these collective effects and the limitation of the existing formulation. It is anticipated that this more thorough analysis can further improve the understanding of MBI mechanisms and shed light on how to suppress or compensate MBI effects in lattice designs. [1] C. -Y. Tsai et al., FEL'14 (THP022), IPAC'15 (MOPMA028) and ERL2015 (TUICLH2034) [2] M. Venturini, Phys. Rev. ST Accel. Beams 10, 104401 (2007) [3] D. Douglas et al., arXiv: 1403.2318v1 [physics.acc-ph] [4] M. Borland, APS Light Source Note LS-287 (2000)
	Poster MOP052 [4.934 MB]
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MOP053	Intra-Beam Scattering in High Brightness Electron Linacs	153
	S. Di Mitri Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	Intra-beam scattering (IBS) of a high brightness electron beam in a linac has been studied* analytically, and the expectations found to be in reasonable agreement with particle tracking results from the Elegant code. It comes out that, under standard conditions for a linac driving a free electron laser, IBS plays no significant role in the development of microbunching instability. A partial damping of the instability is envisaged, however, when IBS is enhanced either with dedicated magnetic insertions, or in the presence of an electron beam charge density at least 4 times larger than that produced by present photo-injectors. * S. Di Mitri, Phys. Rev. Special Topics Accel. Beams, 17, 074401 (2014).
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MOP054	Wake Field Potentials of 'Dechirpers'	157
	A. Novokhatski SLAC, Menlo Park, California, USA
	Funding: This work was supported by Department of Energy Contract No. DOE-AC03-76SF00515. A corrugated structure, which is used on 'dechirpers' is usually a pipe or two plates with small corrugations (bumps) on the walls. There is a good single-mode description of the wake potentials excited by a relativistic bunch if the wave length of the mode is much longer than the distance between the bumps in the pipe. However, ultra-short bunches, which are now used in FELs, excite much higher frequency fields and the corresponding wake potentials will be very different from single-mode description. We made analyzes of these wake potentials based on a numerical solution of Maxwell's equations. The behavior of the wake fields of ultra-short bunches in corrugated structures is not much different from the fields excited usually in accelerating structures where the wake potentials are described by the exponential function. As we increase the bunch length, the wake potentials slowly transform to the form of a single mode. For a practical application we present results for a 'dechirper', which will be soon installed at LCLS. We also carried out calculations for a similar device, that was installed and measured at the Pohang Accelerator Laboratory, Korea. We find very good agreement with the experimental results.
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MOP055	The Effect of Wakefields on the FEL Performance	161
	A. Novokhatski, F.-J. Decker, Y. Nosochkov, M.K. Sullivan SLAC, Menlo Park, California, USA
	Funding: This work was supported by Department of Energy Contract No. DOE-AC03-76SF00515. If a beam travels near collimator jaws or other discontinuities of the beam pipe, it gets the energy loss and the transverse kick due to the back reaction of the beam field diffracted on the collimator's jaws. The wake field effect from collimators may not only bring an additional energy jitter and change the trajectory of the beam, but may also lead to degradation of the performance of Free Electron Laser (FEL) It may be possible due to the special character of the wake fields: the response reaction depends on the longitudinal position of the particles in the bunch. We describe a model of the wake field radiation, simulation results and comparison with measurements.
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MOP056	Reversible Electron Beam Heater without Transverse Deflecting Cavities	166
	G. Stupakov, P. Emma SLAC, Menlo Park, California, USA
	Funding: This work was supported by Department of Energy contract DE-AC03-76SF00515. Suppression of microbunching instability in modern FELs is an important issue that often limits the performance of the machine. A technique to suppress the instability with the help of a reversible electron beam heater was proposed by C. Behrens, Z. Huang, and D. Xiang [*]. It employs transverse deflecting cavities synchronized in a way that one of the cavities, located before a bunch compressor, generates a slice energy spread, while the other one removes it after the beam passes through the bunch compressor. Being an attractive approach, this concept unfortunately imposes extremely tight tolerances on the synchronization of the cavities. In this paper we demonstrate that a reversible heater equivalent to that of Behrens et al. can be designed using much simpler elements: bend magnets and quadrupoles in combination with the energy chirp of the beam. * C. Behrens, Z. Huang, and D. Xiang, PRST-AB 15, 022802 (2012).
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MOP057	Front End Simulations and Design for the CLARA FEL Test Facility	171
	J.W. McKenzie, A.D. Brynes, B.L. Militsyn STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	We present the design and simulations of the Front End for CLARA (Compact Linear Accelerator for Research and Applications), the proposed UK FEL test facility at Daresbury Laboratory. This is based around an S-band RF photocathode gun. Initially this will be the 2.5 cell gun, currently used on VELA facility at Daresbury, which is limited to 10 Hz repetition rate. Later, this will be up-graded to a 1.5 cell gun, currently under development, which will allow repetition rates of up to 400 Hz to be reached. The beam will be accelerated up to 50 MeV with a booster linac which will be operated in both bunching and boosting modes for different operating regimes of CLARA. Simulations are presented for a currently achieved performance of the RF system and drive laser with optimisation of the laser pulse lengths for various operational modes of CLARA.
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MOP060	RFTweak 5 - An Efficient Longitudinal Beam Dynamics Code	176
	B. Beutner, H. Dinter, M. Dohlus DESY, Hamburg, Germany
	The shaping of the longitudinal phase space in bunch compression systems is essential for efficient FEL operation. RF systems and self-field interactions contribute to the overall phase space structure. The design of the various facilities relies on extensive beam dynamics simulations to define the longitudinal dynamics. However, in everyday control room applications such techniques are often not fast enough for efficient operation, e.g. for SASE tuning. Therefore efficient longitudinal beam dynamics codes are required while still maintaining reasonable accuracy. Our approach is to pre-calculate most of the required data for self-field interactions and store them on disc to reduce required online calculation time to a minimum. In this paper we present the fast longitudinal tracking code RFTweak 5, which includes wakes, space charge, and CSR interactions. With this code the full European XFEL with a 1M particles bunch is calculated on the order of minutes on a standard laptop. Neglecting CSR effects this time reduces to seconds.
	Poster MOP060 [0.799 MB]
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MOP062	Technology Maturation for the MaRIE 1.0 X-FEL	181
	J.W. Lewellen, K. Bishofberger, B.E. Carlsten, L.D. Duffy, F.L. Krawczyk, Q.R. Marksteiner, D.C. Nguyen, S.J. Russell, R.L. Sheffield, N.A. Yampolsky LANL, Los Alamos, New Mexico, USA
	Funding: This research was funded by the Matter-Radiation Interactions in Extremes program at Los Alamos National Laboratory, under contract DE-AC52-06NA25396. Los Alamos National Laboratory is proposing a high-energy XFEL, named MaRIE*, to meet its mission needs. MaRIE will be required to generate coherent 42+ keV photons, and, due to space constraints at the LANSCE accelerator complex at Los Alamos, MaRIE's design electron beam energy is 12 GeV. This combination places significant restrictions upon the MaRIE electron beam parameters, in particular the transverse emittance and energy spread at the undulator entrance. We are developing approaches to meet these requirements, but these often require solutions extending beyond the current state-of-the-art in X-FEL design. To reduce overall project risk, therefore, we have identified a number of key experimental and modeling / simulation efforts intended to address both the areas of greatest uncertainty in the preliminary MaRIE design, and the areas of largest known risk. This paper describes the general requirements for the MaRIE X-FEL, our current areas of greatest concern with the preliminary design concept, and our corresponding Technology Maturation Plan (TMP). * MaRIE website: http://www.lanl.gov/science-innovation/science-facilities/marie/index.php
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MOP063	Transverse Emittance Measurement of KAERI Linac with Thick Lens Quadrupole Scan	185
	S. Setiniyaz, I.H. Baek, M.S. Chae, B.A. Gudkov, B. Han, K.H. Jang, Y.U. Jeong, H.W. Kim, S.V. Miginsky, J.H. Nam, S. Park, N. Vinokurov KAERI, Daejon, Republic of Korea S.V. Miginsky, N. Vinokurov BINP SB RAS, Novosibirsk, Russia
	The UED (Ultrafast Electron Diffraction) beamline of KAERI (Korea Atomic Energy Research Institute) WCI (World Class Institute) Center has been completed and successfully commissioned. Transverse emittance of the electron beam was measured at the entrance of the UED chamber with the quadrupole scan technique. In this technique, larger drift distance between the quad and screen is preferred because it gives better thin lens approximation. A space charge dominated beam however, will undergo emittance growth in the long drift caused by the space charge force. We suggest mitigating this growth by introducing quadrupole scan with short drift and without thin lens approximation. We shall discuss the measurement process and results.
	Poster MOP063 [1.287 MB]
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MOP066	Electron Bunch Length Measurement using an RF Deflecting Cavity	188
	S. Park, E.-S. Kim Kyungpook National University, Daegu, Republic of Korea S. Bae, K.H. Jang, Y.U. Jeong, H.W. Kim, J. Mun, N. Vinokurov KAERI, Daejon, Republic of Korea
	Recently, the RF photogun based-ultrafast electron diffraction (UED) system has been developed in KAERI. In the system, the emitted electron bunches are experimentally confirmed to be accelerated up to 3 MeV at 5MW of RF power. And the time duration of the each bunch is initially designed to be less than 50 fs at the sample position. To analyses the performance of the system and to measure exactly the length of the electron bunches, we developed a rectangular type of S-band deflecting cavity working on TM120 mode. The principle of electron deflecting in the cavity, design & mechanical fabrication process and test results will be present in the conference.
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MOP067	Transverse Emittance-Preserving Transfer Line and Arc Compressor for High Brightness Electron Sources	191
	S. Di Mitri, M. Cornacchia, S. Spampinati Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy S. Spampinati Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Minimizing transverse emittance is essential in single- or few-passes accelerators designed to deliver high brightness electron beams. Emission of coherent synchrotron radiation (CSR) is an important factor of emittance degradation. We have demonstrated, with analytical and experimental results, that this perturbation may be cancelled by imposing certain conditions on the electron optics when the bunch length is constant along the line*. This scheme of CSR suppression is then enlarged, analytically and numerically, to cover the case of varying bunch length in a periodic arc compressor**. The proposed solution hold the promise of cost-saving of compact transfer lines with large bending angles, and new schemes for beam longitudinal gymnastics both in recirculating and in single-pass accelerators driving free electron lasers. * S. Di Mitri, M. Cornacchia, S. Spampinati, Phys. Rev. Letters, 110, 014801 (2013) ** S. Di Mitri, M. Cornacchia, Europhys. Letters, 109, 62002 (2015)
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MOP068	First Simulation Results on Free Electron Laser Radiation in Displaced Phase-combined Undulators	196
	N.S. Mirian UVSOR, Okazaki, Japan E. Salehi AUT, Tehran, Iran
	This report deals with self amplified spontaneous emission free electron laser (FEL) amplifier where the FEL emission is obtained from displaced phase combined undulators. Magnetic field of this adjustment methods in three dimensions is presented. The electron dynamics is investigated. The simulation method and results are explained. The radiation properties of the fundamental resonance and third harmonic through the phase combined undulators are compared with the normal undulator with the same undulator deflection parameter
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MOP070	Harmonic Generation in Two Orthogonal Undulators	200
	N.S. Mirian UVSOR, Okazaki, Japan
	In this report, the harmonic generation in two orthogonal undulators is under discussion. There is a possibility of generation of the even and odd harmonics as well as no-integer harmonics in two orthogonal undulators. By considering the first order of electron velocity, the total energy radiated per unit solid angle per unit frequency interval for a single electron traveling along the undulators is derived. Also a numerical simulation of one-dimensional non-averaged equations is conducted to present the self amplified spontaneous emission of harmonic generation in two orthogonal undulators.
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MOP071	Carrier-Envelope-Phase Stable Linearly and Circularly Polarized Attosecond Pulse Sources	205
	Z. Tibai, G. Almási, Zs. Csiha-Nagy, J.A. Fülöp, J. Hebling University of Pecs, Pécs, Hungary J.A. Fülöp, Gy. Tóth MTA-PTE High-Field Terahertz Research Group, Pecs, Hungary
	Recently, we proposed a robust method for producing waveform-controlled attosecond pulses in the EUV spectral range.* In our scheme the relativistic electron beam, provided by a LINAC, is sent through a modulator undulator where a TW-power laser beam is superimposed on it in order to generate nanobunches. The nanobunched electron beam passes through a single- or few-period radiator undulator (RU). The waveform of the generated attosecond pulses closely resembles the longitudinal distribution of the magnetic field. According to our calculations, at 20 nm (60 nm) wavelength carrier-envelope-phase (CEP) stable pulses with 23 nJ (80 nJ) energy, 80 as (240 as) duration, and 31 mrad (13 mrad) CEP fluctuation (standard deviation) can be achieved at K=0.5. More than 500 nJ energy is predicted at longer wavelengths and larger K. The energy fluctuation of the EUV pulse is 2.5 times higher than that of the laser. By using a helical RU, even circularly polarized attosecond pulses with 30/300 nJ energy can be generated, depending on the wavelength. To the best of our knowledge, no other presently available technique enables the generation of arbitrary-waveform, CEP-controlled attosecond pulses. The predicted pulse energies are sufficiently high to be used as pump pulses in attosecond pump-probe measurements. * Z. Tibai et al., Phys. Rev. Lett. 113, 104801 (2014).
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MOP074	Efficiency Enhancement of a Harmonic Lasing Free-Electron Laser	209
	N.S. Mirian UVSOR, Okazaki, Japan B. Maraghechi, E. Salehi AUT, Tehran, Iran
	The harmonic lasing free-electron laser amplifier, in which two wigglers is employed in order for the fundamental resonance of the second wiggler to coincide with the third harmonic of the first wiggler to generate ultraviolet radiation, is studied. A set of coupled nonlinear first-order differential equations describing the nonlinear evolution of the system, for a long electron bunch, is solved numerically by CYRUS code. Thermal effects in the form of longitudinal velocity spread are also investigated. The second wiggler field decreases linearly and nonlinearly at the point where the radiation of the third harmonic saturates to enhance the efficiency. The optimum starting point and the slope of the tapering of the amplitude of the wiggler are found by a successive run of the code. It is found that tapering can increase the saturated power of the third harmonic considerably.
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MOP075	Three-dimensional Simulation of a Harmonic Lasing Free-Electron Laser Amplifier	213
	E. Salehi, B. Maraghechi AUT, Tehran, Iran N.S. Mirian UVSOR, Okazaki, Japan
	Three-dimensional simulation of harmonic lasing Free-electron laser is represented in the steady-state regime. Here, the third harmonic of the first wiggler is adjusted at the fundamental resonance of the second wiggler by reducing the magnetic field strength of the second wiggler. The hyperbolic wave equations can be transformed into parabolic diffusion equations by using the slowly varying envelope approximation. A set of coupled nonlinear first-order differential equations describing the nonlinear evolution of the system is solved numerically by CYRUS3D code. This set of equations describes self-consistently the longitudinal spatial dependence of the radiation waists, curvatures, and amplitudes together with the evaluation of the electron beam. Thermal effects in the form of longitudinal velocity spread are also investigated. In order to reduce the length of the wiggler, the prebunched electron beam is considered.
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MOP076	Free-Electron Laser Driven by a 500 MeV Laser Plasma Accelerator Beam	217
	W. Qin, J.E. Chen, S. Huang, K.X. Liu, X.Q. Yan, L. Zeng PKU, Beijing, People's Republic of China Y. Ding, Z. Huang SLAC, Menlo Park, California, USA
	A laser plasma accelerator is under construction at Peking University and several hundred MeV electron beams are expected. In this paper we discuss applying a 500 MeV beam with 1% relative energy spread to FEL. Bunch decompression method is considered to deal with the large energy spread of the beam. Emittance growth induced by large divergence and energy spread in electron beam transport has been treated with the chromatic matching manipulation. Simulation shows that 100 MW level, 6.3 fs , 0.008 bandwidth output can be obtained for 30 nm FEL. TGU method with assumed matched beam is also discussed as a comparison.
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MOP078	Sub-Radiance and Enhanced-Radiance of Undulator Radiation from a Correlated Electron Beam	221
	R. Ianconescu Shenkar College of Engineering and Design, Ramat Gan, Israel A. Gover University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel E. Hemsing, A. Marinelli SLAC, Menlo Park, California, USA A. Nause UCLA, Los Angeles, USA
	Funding: We acknowledge the United States - Israel Binational Science Foundation (BSF) The radiant intensity of Synchrotron Undulator Radiation (UR) depends on the current noise spectrum of the electron beam injected into the wiggler. The current noise spectrum and intensity can be controlled (suppressed or enhanced relative to the shot-noise level) by the effect of collective longitudinal space charge interaction in a drift and dispersion sections[1]. This new control lever is of significant interest for possible control of SASE in FEL, since UR is the incoherent seed of SASE. Thus, control of spontaneous UR is a way to enhance the coherence of seeded FEL [2], or alternatively, obtain enhanced radiation from a cascade noise-amplified electron beam [3]. The dependence of UR emission on the current noise is primarily a result of the longitudinal correlation of the e-beam distribution due to the longitudinal space charge effect. However, at short wavelengths, 3-D effects of transverse correlation and effects of emittance disrupts the proportionality relation between the UR intensity and e-beam current noise. We present analysis and simulation of UR subradiance/superradiance under various ranges of beam parameters, and compare to recent experimental observations [1]. [1] D. Ratner et al., PRST - ACCELERATORS AND BEAMS 18, 050703 (2015) [2] E. Allaria et al., Nat. Photonics 7, 913 (2013) [3] A. Marinelli et al., Phys. Rev. Lett. 110, 264802 (27 June 2013)
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MOP079	On the Importance of Electron Beam Brightness in High Gain Free Electron Lasers	227
	S. Di Mitri Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	Linear accelerators delivering high brightness electron beams are essential for driving short wavelength, high gain free-electron lasers (FELs). The FEL radiation output efficiency is often parametrized through the power gain length that relates FEL performance to the electron beam quality at the undulator. Experimental data and simulation results of existing and planned FEL facilities are used to explicit the relationship between the FEL output wavelength and the electron beam six-dimensional brightness*. Practical formulas are provided that show the dependence of the exponential gain length on the beam brightness**. * S. Di Mitri, M. Cornacchia, Phys. Reports, 539 (2014) 1~48. ** S. Di Mitri, Photonics, 2 (2015) 317~341
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MOP081	Generating a Single-Spike SASE Pulse in the Soft X-Ray Regime by Velocity Bunching	233
	J. Lee, B.H. Oh, M. Yoon POSTECH, Pohang, Kyungbuk, Republic of Korea
	A bright ultrashort X-ray pulse emerges as a valuable tool for many fields of research nowadays. The single-spike operation of X-ray FEL is one way of making a bright ultrashort X-ray pulse. It requires extreme bunching and a magnetic chicane is a conventional compressor. In a low charge range, a magnetic chicane can be replaced by the velocity bunching technique. In this paper, we present the result of particle tracking simulation generating a single-spike soft X-ray SASE pulse without a magnetic chicane. We also investigate the error effects and show that this scheme is feasible under current technology.
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MOP082	New Soft X-Ray Undulator Line Using 10 GeV Electron Beam in PAL-XFEL	237
	C.H. Shim, I.S. Ko POSTECH, Pohang, Kyungbuk, Republic of Korea Y.W. Parc PAL, Pohang, Kyungbuk, Republic of Korea
	PAL-XFEL is designed to have five undulator lines and only two undulator lines, the HXR undulator line with 10 GeV electron beam and the SXR undulator line with 3.15 GeV electron beam, will be installed during phase I. A photon beam energy from 0.28 to 1.24 keV will be provided at the SXR undulator line and different range from 2 to 20 keV will be supplied at the HXR undulator line. According to existing schedule, however, photon beam energy from 1.24 to 2 keV won't be provided in PAL-XFEL. In this research, new soft X-ray undulator line for PAL-XFEL using 10 GeV electron beam in main linac is proposed to cover the vacant photon energy. Four candidates are evaluated by estimating and comparing FEL performances using Ming Xie's formula.
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MOP083	FEL Operation Modes of the MAX IV Short Pulse Facility	241
	A. Mak, F. Curbis, S. Werin MAX-lab, Lund, Sweden
	The Short Pulse Facility (SPF) of the MAX IV Laboratory in Lund, Sweden features the production of ultrashort, incoherent x-ray pulses. It is driven by a 3-GeV linac and comprises two 5-metre undulator modules. While the SPF is designed for spontaneous radiation, we explore alternative operation modes in which the SPF functions as a simple free-electron laser (FEL). In this article, we characterize two of them in time-dependent numerical simulations. We perform a sensitivity study on the electron beam parameters and examine the technique of single-step tapering.
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MOP084	Seeded FEL Study for the Cascaded HGHG option for FLASH2	246
	G. Feng, W. Decking, M. Dohlus, T. Limberg, I. Zagorodnov DESY, Hamburg, Germany K.E. Hacker DELTA, Dortmund, Germany T. Plath Uni HH, Hamburg, Germany
	The free electron laser (FEL) facility at DESY in Hamburg (FLASH) is the world's first FEL user facility which can produce extreme ultraviolet (XUV) and soft X-ray photons. In order to increase beam time delivered to users, a major upgrade named FLASH II is in progress. As a possibility, a seeding undulator section can be installed between the extraction arc section and the SASE undulator of FLASH2. In this paper, a possible seeding scheme for the cascaded HGHG option for FLASH2 is given. The SASE undulator can be used as the second radiator of the cascaded HGHG. Parameters optimization for the accelerating modules and the bunch compressors has been done to meet the requirement of the electron bunches. In the beam dynamics simulation, collective effects were taken into account. Particle distribution generated from the beam dynamics simulation was used for the seeded FEL study. Space charge and CSR impacts on the microbunches were taken into account during the seeded FEL simulation. The simulation results show that FEL radiation with the wavelength of a few nms and with high monochromaticity can be seeded at FLASH2.
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MOP085	Scheme to Increase the Output Average Spectral Flux of the European XFEL at 14.4 keV	251
	V. Kocharyan, E. Saldin DESY, Hamburg, Germany G. Geloni XFEL. EU, Hamburg, Germany
	Inelastic X-ray scattering and nuclear resonance scattering are limited by the photon flux available at SR sources, up to 1010 ph/s/meV at 14.4 keV. A thousand-fold increase may be obtained by exploiting high repetition rate self-seeded pulses at the European XFEL. We report on a feasibility study for an optimized configuration of the SASE2 beamline combining self-seeding and undulator tapering at 14.4 keV. One should perform monochromatization at 7.2 keV by self-seeding, and amplify the seed in the first part of the output undulator. Before saturation, the electron beam is considerably bunched at the 2nd harmonic. A second part of the output undulator tuned to 14.4 keV can thus be used to obtain saturation at this energy. One can further prolong the exchange of energy between the photon and the electron beam by tapering the last part of the output undulator. Start-to-end simulations demonstrate that self-seeding, combined with undulator tapering, allows one to achieve more than a hundred-fold increase in average spectral flux compared with the nominal SASE regime at saturation, resulting in a spectral flux of order 1013 ph/s/meV. A more detailed description of this study can be found in*. * G. Geloni, V. Kocharyan and E.~Saldin, "Scheme to increase the output average spectral flux of the European XFEL at 14.4 keV", DESY 15-141 (2015).
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MOP086	Novel Opportunities for Sub-meV Inelastic X-Ray Scattering Experiments at High-Repetition Rate Self-seeded XFELs	257
	O.V. Chubar BNL, Upton, Long Island, New York, USA G. Geloni, A. Madsen XFEL. EU, Hamburg, Germany V. Kocharyan, E. Saldin, S. Serkez DESY, Hamburg, Germany Yu. Shvyd'ko ANL, Argonne, Ilinois, USA J. Sutter DLS, Oxfordshire, United Kingdom
	Inelastic x-ray scattering (IXS) is an important tool for studies of equilibrium dynamics in condensed matter. A new spectrometer recently proposed for ultra-high-resolution IXS (UHRIX) has achieved 0.6 meV and 0.25/nm spectral and momentum Transfer resolutions, respectively*. However, further improvements down to 0.1 meV and 0.02/nm are required to close the gap in energy-momentum space between high and low frequency probes. We Show that this goal can be achieved by further improvements in x-ray optics and by increasing the spectral flux of the incident x-ray pulses. UHRIX performs best at energies from 5 to 10 keV, where a combination of self-seeding and undulator tapering at the SASE2 beamline of the European XFEL promises up to a hundred-fold increase in average spectral flux compared to nominal SASE pulses at saturation, or three orders of magnitude more than possible with storage-ring based radiation sources. Wave-optics propagation shows that about 7·1012 ph/s in a 90-microeV bandwidth can be achieved on the sample. This will provide unique new possibilities for IXS. Extended information about our work can be found in**. * Y. Shvyd'ko et al., Nature Communications 5:4219 (2014). ** O. Chubar et al., ‘Novel opportunities for sub-meV inelastic X-ray scattering at high-repetition rate self-seeded X-ray free-electron lasers', http://arxiv.org/abs/1508.02632, DESY 15-140, (2015).
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MOP087	Multistage CSR Microbunching Gain Development in Transport or Recirculation Arcs	263
	C.-Y. Tsai Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA D. Douglas, R. Li, C. Tennant JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Coherent synchrotron radiation (CSR) induced microbunching instability has been one of the most challenging issues in the design of modern accelerators. A linear Vlasov solver has been developed [1] and applied to investigate the physical processes of microbunching gain amplification for several example lattices [2]. In this paper, by further extending the concept of stage gain as proposed by Huang and Kim [3], we develop a method to characterize the microbunching development in terms of stage orders that allow the quantitative comparison of optics impacts on microbunching gain for different lattices. We find that the microbunching instability in our demonstrated arcs has a distinguishing feature of multistage amplification (e.g, up to 6th stage amplification for our example transport arcs, in contrast to two-stage amplification for a typical 4-dipole bunch compressor chicane). We also try to connect lattice optics pattern with the obtained stage gain functions by a physical interpretation. This Vlasov analysis is validated by ELEGANT [4] tracking results with excellent agreement. [1] C. -Y. Tsai et al., MOP052, these proceedings [2] See, for example, C. -Y. Tsai et al., ERL2015 (TUICLH2034) [3] Z. Huang and K. -J. Kim, Phys. Rev. ST Accel. Beams 5, 074401 (2002) [4] M. Borland, APS Light Source Note LS-287 (2000)
	Poster MOP087 [1.962 MB]
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