FEL2015 - List of Keywords (emittance)

Paper	Title	Other Keywords	Page
MOC03	Estimate of Free-Electron Laser Gain Length in the Presence of Electron Beam Collective Effects	FEL, electron, undulator, collective-effects	24
	S. Di Mitri Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy S. Spampinati Cockcroft Institute, Warrington, Cheshire, United Kingdom
	A novel definition for the three-dimensional free electron laser gain length is proposed, which takes into account the increase of electron beam projected emittance as due, for example, to geometric transverse wakefield and coherent synchrotron radiation developing in linear accelerators. The analysis shows that the gain length is affected by an increase of the electron beam projected emittance, even though the slice (local) emittance is preserved, and found to be in agreement with Genesis code simulation results. It is then shown that the minimum gain length and the maximum of output power may notably differ from the ones derived when collective effects are neglected. The proposed model turns out to be handy for a parametric study of electron beam six-dimensional brightness and FEL performance as function, e.g., of bunch length compression factor, accelerator alignment tolerances and optics design. S. Di Mitri, S. Spampinati, Phys. Rev. Special Topics Accel. Beams, 17, 110702 (2014)
	Slides MOC03 [2.528 MB]
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MOP018	Comparison of Astra Simulations With Beam Parameter Measurements at the Kaeri Ultrashort Pulse Facility	electron, laser, simulation, quadrupole	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	cavity, solenoid, cathode, quadrupole	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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MOP025	Electron Beam Properties from a Compact Seeded Terahertz FEL Amplifier at Kyoto University	electron, gun, laser, solenoid	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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MOP034	Beam Optics Measurements at FERMI by using Wire-Scanner	optics, linac, quadrupole, FEL	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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MOP039	First Results of Commissioning of the PITZ Transverse Deflecting Structure	electron, simulation, laser, klystron	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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MOP053	Intra-Beam Scattering in High Brightness Electron Linacs	electron, linac, brightness, quadrupole	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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MOP055	The Effect of Wakefields on the FEL Performance	wakefield, linac, FEL, undulator	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	electron, cavity, optics, synchrotron	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	laser, gun, linac, simulation	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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MOP062	Technology Maturation for the MaRIE 1.0 X-FEL	linac, FEL, simulation, laser	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	quadrupole, electron, space-charge, experiment	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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MOP067	Transverse Emittance-Preserving Transfer Line and Arc Compressor for High Brightness Electron Sources	dipole, optics, electron, FEL	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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MOP076	Free-Electron Laser Driven by a 500 MeV Laser Plasma Accelerator Beam	FEL, undulator, laser, plasma	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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MOP079	On the Importance of Electron Beam Brightness in High Gain Free Electron Lasers	FEL, electron, undulator, brightness	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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MOD01	Review of Experimental Results from High Brightness DC Guns: Highlights in FEL Applications	gun, cathode, FEL, brightness	269
	N. Nishimori JAEA, Ibaraki-ken, Japan
	Funding: This work is partially supported by a JSPS Grant-in-Aid for Scientific Research in Japan (15H03594). Future ERL light sources and high repetition rate X-ray FELs require high-brightness and high-current electron guns. A DC photoemission gun is one of the most promising candidates for such guns, because a record high current of 65 mA and generation of high brightness beam with 90% normalized emittances of 0.3 mm-mrad with bunch charge of 77 pC were recently demonstrated at the Cornell photoinjector with a 350 kV photoemission gun [1,2]. Further increase of the gun high voltage is desirable to reduce space charge induced emittance growth especially for high bunch charge application such as X-ray FEL. Employment of a segmented insulator is a key to reach higher voltage [3]. This technique led to generation of 500 keV beam from the JAEA gun with 160mm acceleration gap [4], conditioning voltage more than 500 kV at the Cornell gun with gap < 50 mm [5], and demonstration of 500 kV holding for 10 hours at the KEK gun with 70 mm gap [6]. In this talk, we present recent experimental results of high brightness DC guns and discuss highlights and limitations in FEL applications. [1] Dunham, APL 102, 034105. [2] Gulliford, PRSTAB 16, 073401. [3] Nagai, RSI 81, 033304. [4] Nishimori, APL 102, 234103. [5] Maxson, RSI 85, 093306. [6] Yamamoto, private communication.
	Slides MOD01 [3.051 MB]
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MOD04	Emittance Measurements of the Electron Beam at PITZ for the Commissioning Phase of the European X-FEL	laser, electron, simulation, gun	285
	G. Vashchenko, P. Boonpornprasert, J.D. Good, M. Groß, H. Huck, I.I. Isaev, D.K. Kalantaryan, G. Kourkafas, M. Krasilnikov, D. Malyutin, D. Melkumyan, A. Oppelt, M. Otevřel, Y. Renier, T. Rublack, F. Stephan DESY Zeuthen, Zeuthen, Germany G. Asova INRNE, Sofia, Bulgaria M. A. Bakr Assiut University, Assiut, Egypt C. Hernandez-Garcia JLab, Newport News, Virginia, USA O. Lishilin, G. Pathak Uni HH, Hamburg, Germany Q.T. Zhao IMP/CAS, Lanzhou, People's Republic of China
	For the operation of free electron lasers (FELs) like the European X-FEL and FLASH located at DESY, Hamburg Site, high quality electron beams are required already from the source. The Photo Injector Test facility at DESY, Zeuthen Site (PITZ) was established to develop, characterize and optimize electron sources for such FELs. Last year the work at PITZ focused on the optimization of a photo injector operated with the startup parameters of the European X-FEL. This implies photocathode laser pulses with a Gaussian temporal profile of about 11-12 ps FWHM to drive the photo gun operated at a gradient of 53 MV/m. Significant effort was spent on the electron beam characterization and optimization for various bunch charges. Emittance measurements were performed as a function of major accelerator parameters such as main solenoid current, laser spot size on the cathode and the gun launching phase. The requirement on the beam emittance for bunch charge of 500 pC for the European XFEL commissioning phase has been demonstrated. Results of these studies accompanied with the corresponding simulations are presented in this paper.
	Slides MOD04 [1.603 MB]
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TUP007	High Fidelity Start-to-end Numerical Particle Simulations and Performance Studies for LCLS-II	undulator, electron, FEL, simulation	342
	G. Marcus, Y. Ding, P. Emma, Z. Huang, T.O. Raubenheimer, L. Wang SLAC, Menlo Park, California, USA J. Qiang, M. Venturini LBNL, Berkeley, California, USA
	High fidelity numerical particle simulations that leverage a number of accelerator and FEL codes have been used to analyze the LCLS-II FEL performance. Together, the physics models that are included in these codes have been crucial in identifying, understanding, and mitigating a number of potential hazards that can adversely affect the FEL performance, some of which are discussed in papers submitted to this conference[, ]. Here, we present a broad overview of the LCLS-II FEL performance, based on these start-to-end simulations, for both the soft X-ray and hard X-ray undulators including both SASE and self-seeded operational modes. M. Venturini, et al., The microbunching instability and LCLS-II lattice design: lessons learned, FEL'15 ** Z. Zhang, et al., Microbunching-induced sidebands in a seeded free-electron laser, FEL'15
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TUP013	The X-Band FEL Collaboration	FEL, undulator, linac, electron	368
	J. Pfingstner, E. Adli University of Oslo, Oslo, Norway A.A. Aksoy, O. Yavaş Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey D. Angal-Kalinin, J.A. Clarke STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom C.J. Bocchetta, A.I. Wawrzyniak Solaris, Kraków, Poland M.J. Boland, T.K. Charles, R.T. Dowd, G. LeBlanc, Y.E. Tan, K.P. Wootton, D. Zhu SLSA, Clayton, Australia G. Burt Lancaster University, Lancaster, United Kingdom N. Catalán Lasheras, A. Grudiev, A. Latina, D. Schulte, S. Stapnes, I. Syratchev, W. Wuensch CERN, Geneva, Switzerland A. Charitonidis NTUA, Athens, Greece G. D'Auria, S. Di Mitri, C. Serpico Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy T.J.C. Ekelöf, M. Jacewicz, R.J.M.Y. Ruber, V.G. Ziemann Uppsala University, Uppsala, Sweden W. Fang, Q. Gu SINAP, Shanghai, People's Republic of China E.N. Gazis National Technical University of Athens, Athens, Greece X.J.A. Janssen VDL ETG, Eindhoven, The Netherlands Z. Nergiz Nigde University, Nigde, Turkey
	The X-band FEL collaboration is currently designing an X-ray free-electron laser based on X-band acceleration technology. Due to the higher accelerating gradients achievable with X-band technology, a X-band normal conducting linac can be shorter and therefore potentially cost efficient than what is achievable with lower frequency structures. This cost reduction of future FEL facilities addresses the growing demand of the user community for coherent X-rays. The X-band FEL collaboration consists of 12 institutes and universities that jointly work on the preparation of design reports for the specific FEL projects. In this paper, we report on the on-going activities, the basic parameter choice, and the integrated simulation results. We also outline the interest of the X-band FEL collaboration to use the electron linac CALIFES at CERN to test FEL concepts and technologies relevant for the X-band FEL collaboration.
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TUP021	Fundamental Limitations of the SASE FEL Photon Beam Pointing Stability	FEL, radiation, electron, undulator	397
	E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	The radiation from SASE FEL has always limited value of the degree of transverse coherence. Two effects define the spatial coherence of the radiation: the mode competition effect, and the effect of poor longitudinal coherence. For the diffraction limited case we deal mainly with the effect of the poor longitudinal coherence leading to significant degradation of the spatial coherence in the post-saturation regime. When transverse size of the electron beam significantly exceeds diffraction limit, the mode competition effect does not provide the selection of the fundamental FEL mode, and spatial coherence degrades due to contribution of the higher azimuthal modes. Another consequence of this effect are fluctuations of the spot size and pointing stability of the photon beam. These fluctuations are fundamental and originate from the shot noise in the electron beam. The effect of pointing instability becomes more pronouncing for shorter wavelengths. Our study is devoted to the fundamental analysis of the effect and description of possible means for improving the degree of transverse coherence and the pointing stability.
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TUP035	Operation of a Slit Emittance Meter in the MAX IV Gun Test Stand	gun, cathode, laser, background	444
	J. Andersson, F. Curbis, M. Isinger, F. Lindau, S. Werin MAX-lab, Lund, Sweden
	The MAX IV facility in Lund, Sweden is currently under commissioning. There are two guns in the current MAX IV injector, one thermionic gun for storage ring injection and one photocathode gun for the Short Pulse Facility. There is a possibility of extending the facility to include a Free Electron Laser. To investigate how the beam from the injector can be improved and how to match it to the future requirements for a FEL, the emittance meter from SPARC has been recommissioned at the MAX IV gun test stand. In this paper we report on the progress of this work and results from the first measurements.
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TUP036	Initial Commissioning Results of the MAX IV Injector	gun, linac, laser, cathode	448
	J. Andersson, F. Curbis, M. Eriksson, D. Kumbaro, F. Lindau, E. Mansten, D.F. Olsson, S. Thorin, S. Werin MAX-lab, Lund, Sweden
	The MAX IV facility in Lund, Sweden is currently under commissioning. In the MAX IV injector there are two guns, one thermionic gun for storage ring injection and one photocathode gun for the Short Pulse Facility. The commissioning of the injector and the LINAC has been ongoing for the last year and ring commissioning is due to start shortly. In this paper we will present the results from beam performance experiments for the injector at the current stage of commissioning.
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TUP040	Simulation and Design of Low Emittance RF Electron Gun	electron, gun, cavity, coupling	455
	C. Saisa-ard, S. Rimjaem Chiang Mai University, Chiang Mai, Thailand
	Funding: This work has been supported by the CMU Junior Research Fellowship Program and the Department of Physics and Materials Science, Faculty of Science, Chiang Mai University. Generation of high-brightness electron beam is one of the most critical issues in development of advanced electron accelerators and light sources. At the Plasma and Beam Physics (PBP) Research Facility, Chiang Mai University, a low emittance RF electron gun is under the development. This RF-gun is planned to be used as an electron source for a future IR/THz FEL facility. An extra resonant cavity is added to the modified design of the existing PBP-CMU RF-gun in order to reduce the transverse sliced emittance. This cell is coupled to the main full-cell via a side-coupling cavity. The electromagnetic field distributions inside the cavities are simulated by using the CST Microwave Studio 2012. Then, beam dynamic simulations utilizing the program PARMELA are performed. Both RF and beam dynamic simulation results are reported and discussed in this contribution. The authors would like to acknowledge the financial support to participate this conference by the Department of Physics and Materials Science and the Graduate School, Chiang Mai University.
	Poster TUP040 [2.140 MB]
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TUP065	Beam Dynamics Simulation for the Upgraded PITZ Photo Injector Applying Various Photocathode Laser Pulses	laser, electron, flattop, cathode	501
	M. A. Bakr, M. Khojoyan, M. Krasilnikov, F. Stephan, G. Vashchenko DESY Zeuthen, Zeuthen, Germany M. A. Bakr Assiut University, Assiut, Egypt
	The Photo Injector Test facility PITZ at DESY, Zeuthen site, characterizes and optimizes high brightness electron sources for linac-based Free Electron Laser (FELs) with a specific focus on the requirements of FLASH and the European XFEL. X-ray FELs require high brightness electron beam in terms of high peak current, small transverse emittance and energy spread. Such high quality beams are mandatory for efficient SASE generation in a single pass through long undulators with narrow gaps. Photocathode laser pulse shaping is a powerful tool to optimize the photo injector performance. Recently, a new photocathode laser system capable of producing 3D quasi-ellipsoidal pulses has been installed at PITZ. It is foreseen to operate this new system in parallel to the nominal one that generates cylindrical pulses with various temporal profiles. A set of numerical simulations was performed to study and compare the beam dynamics of electron beams produced with 3D ellipsoidal laser profile with the typical cylindrically shaped (flat-top) profile. Different bunch charges from 20 pC up to several nC are considered, in order to find an optimum PITZ machine setup which will yield the lowest transverse emittance. we present and discuss the results of this comparison in the submission.
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TUP068	Electron Beam Phase Space Tomographie at the European XFEL Injector	electron, optics, quadrupole, betatron	515
	M. Scholz, B. Beutner DESY, Hamburg, Germany
	Transverse emittances as well as the energy spread and the peak current of the electron bunches are important parameters for high-gain free electron lasers such as the European XFEL. Investigations of the 6D phase space characterisation would give important indications to optimise the beam quality for SASE operation. The injector of the European XFEL includes, inter alia, a laser heater, a transverse deflecting cavity, a spectrometer, a diagnostic section with four OTR screens as well as several quadrupole magnets. In this paper, we will discuss the possibilities to characterise the 6D phase space of the electron beam in the injector of the Eurpean XFEL.
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WEP002	Simulating Single Crystal Copper Photocathode Emittance	simulation, electron, FEL, laser	587
	T. Vecchione SLAC, Menlo Park, California, USA
	Funding: US DOE contract DE-AC02-76SF00515 The performance of free-electron lasers depends on the quality of the electron beam used. In some cases this performance can be improved by optimizing the choice of photocathode with respect to emittance. With this in mind, electronic structure calculations have been included in photoemission simulations and used to predict the emittance from single crystal copper photocathodes. The results from different low-index surfaces are reported. Within the model assumptions the Cu(100) surface was identified as having minimal emittance, particularly when illuminated by 266 nm light and extracted in a 60 MV/m gradient. These findings may guide future experimental work, leading to improved machine performance.
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WEP003	Recent Understanding and Improvements of the LCLS Injector	laser, cathode, FEL, electron	592
	F. Zhou, D.K. Bohler, Y. Ding, S. Gilevich, Z. Huang, H. Loos, D.F. Ratner SLAC, Menlo Park, California, USA
	Funding: U.S. DOE contract No. DE-AC02-76SF00515. Ultraviolet drive laser and copper photocathode are the key systems for reliably delivering <0.4 micron of emittance and high brightness free electron laser (FEL) at the linac coherent light source (LCLS). Characterizing, optimizing and controlling laser distributions in both spatial and temporal directions are important for ultra-low emittance generation. Spatial truncated Gaussian laser profile has been demonstrated to produce better emittance than a spatial uniform beam. Sensitivity of the spatial laser distribution for the emittance is measured and analysed. Stacking two 2-ps Gaussian laser beams significantly improves emittance and eventually FEL performance at the LCLS in comparison to a single 2-ps Gaussian laser pulse. In addition, recent observations at the LCLS show that the micro-bunching effect depends strongly on the cathode spot locations. The dependence of the micro-bunching and FEL performance on the cathode spot location is mapped and discussed.
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WEP058	Emittance Measurements at the PAL-XFEL Injector Test Facility	laser, quadrupole, gun, electron	690
	J. Lee POSTECH, Pohang, Kyungbuk, Republic of Korea J.H. Han, J.H. Hong, C.H. Kim, I.S. Ko, S.J. Lee, S.J. Park, H. Yang PAL, Pohang, Kyungbuk, Republic of Korea
	The PAL-XFEL Injector Test Facility (ITF) at PAL has been operating for experimental optimization of electron beam parameters and for beam test of various accelerator components. It consists of a photocathode RF gun, two S-band accelerating structures, a laser heater system, and beam diagnostics such as ICTs, BPMs, screens, beam energy spectrometers and an RF deflector. Projected and slice emittance measurements were carried out by using single quadrupole scan. In this paper, we present the emittance measurements.
	Poster WEP058 [0.646 MB]
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WEP061	Numerical and Experimental Studies on Electron Beam Properties from Asymmetric RF-gun	gun, electron, linac, simulation	698
	S. Rimjaem, N. Chaisueb, J. Saisut, C. Thongbai, W. Thongpakdi Chiang Mai University, Chiang Mai, Thailand N. Kangrang FNRF, Chiang Mai, Thailand E. Kongmon, K. Kosaentor, P. Wichaisirimongkol IST, Chiang Mai, Thailand
	Funding: This work has been supported by the CMU Junior Research Fellowship Program, and the Department of Physics and Materials Science, Faculty of Science, Chiang Mai University. The electron linear accelerator at the Plasma and Beam Physics Research Facility (PBP-CMU Linac), Chiang Mai University, Thailand, is used to produce femtosecond electron bunches for generation of THz radiation. The main components of the PBP-CMU Linac are a thermionic RF electron gun, an alpha magnet, a travelling wave linac structure, quadrupole lens, steering magnets, and various diagnostic components. The RF-gun consists of a 1.6 S-band standing wave structure and a side-coupling cavity. The 2856 MHz RF wave is transmitted from the klystron to the gun through a rectangular waveguide input-port. Both the RF input-port and the side-coupling cavity cause an asymmetric electromagnetic field distribution inside the gun. The electron beam from the RF-gun has asymmetric transverse shape with an emittance value, which is higher than the beam from the symmetric fields. The problems are increased when the beam is transported from the gun through the whole accelerator system. Beam dynamic simulations are performed to investigate the effect of the asymmetric fields on the electron properties by using the codes PARMELA and ELEGANT. An integrated electron beam diagnostic station to measure the beam properties will be installed in the system to investigate these effects. Results from numerical and experimental studies are reported in this contribution.
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WEP069	Minimization of the Emittance Growth Induced by Coherent Synchrotron Radiation in Arc Compressor	dipole, synchrotron-radiation, simulation, synchrotron	711
	X.Y. Huang, X. Cui, Y. Jiao, G. Xu IHEP, Beijing, People's Republic of China
	Funding: Supported by National Natural Science Foundation of China (11475202, 11405187). Coherent synchrotron radiation (CSR) is a critical issue when electron bunches with short bunch length and high peak current transporting through a bending system in high-brightness light sources and linear colliders. For example, a high peak current of electron beam can be achieved by using magnetic bunch compressor, however, CSR induced transverse emittance growth will limit the performance of bunch compressor. In this paper, based on our 'two-dimensional point-kick analysis', an arc compressor with high compression factor is studied. Through analytical and numerical research, an easy optics design technique is introduced that could minimize the emittance dilution within this compressor. It is demonstrated that the strong compression of bunch length and the transverse emittance preservation can be achieved at the same time.
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WEP070	Start-to-End Simulation of the LCLS-II Beam Delivery System with Real Number of Electrons	FEL, linac, electron, simulation	714
	J. Qiang, C.E. Mitchell, C. F. Papadopoulos, M. Venturini LBNL, Berkeley, California, USA Y. Ding, P. Emma, Z. Huang, G. Marcus, Y. Nosochkov, T.O. Raubenheimer, L. Wang, M. Woodley SLAC, Menlo Park, California, USA
	The LCLS-II as a next generation high repetition rate FEL based X-ray light source will enable significant scientific discoveries. In this paper, we report on the progress in the design of the accelerator beam delivery system through start-to-end simulations. We will present simulation results for three cases, 20 pC, 100 pC and 300 pC that are transported through the hard X-ray line and the soft X-ray line for FEL radiation.
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Paper

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Other Keywords

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MOC03

Estimate of Free-Electron Laser Gain Length in the Presence of Electron Beam Collective Effects

FEL, electron, undulator, collective-effects

24

S. Di Mitri
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
S. Spampinati
Cockcroft Institute, Warrington, Cheshire, United Kingdom

A novel definition for the three-dimensional free electron laser gain length is proposed*, which takes into account the increase of electron beam projected emittance as due, for example, to geometric transverse wakefield and coherent synchrotron radiation developing in linear accelerators. The analysis shows that the gain length is affected by an increase of the electron beam projected emittance, even though the slice (local) emittance is preserved, and found to be in agreement with Genesis code simulation results. It is then shown that the minimum gain length and the maximum of output power may notably differ from the ones derived when collective effects are neglected. The proposed model turns out to be handy for a parametric study of electron beam six-dimensional brightness and FEL performance as function, e.g., of bunch length compression factor, accelerator alignment tolerances and optics design.
* S. Di Mitri, S. Spampinati, Phys. Rev. Special Topics Accel. Beams, 17, 110702 (2014)

Slides MOC03 [2.528 MB]

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MOP018

Comparison of Astra Simulations With Beam Parameter Measurements at the Kaeri Ultrashort Pulse Facility

electron, laser, simulation, quadrupole

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

cavity, solenoid, cathode, quadrupole

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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MOP025

Electron Beam Properties from a Compact Seeded Terahertz FEL Amplifier at Kyoto University

electron, gun, laser, solenoid

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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MOP034

Beam Optics Measurements at FERMI by using Wire-Scanner

optics, linac, quadrupole, FEL

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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MOP039

First Results of Commissioning of the PITZ Transverse Deflecting Structure

electron, simulation, laser, klystron

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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MOP053

Intra-Beam Scattering in High Brightness Electron Linacs

electron, linac, brightness, quadrupole

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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MOP055

The Effect of Wakefields on the FEL Performance

wakefield, linac, FEL, undulator

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

electron, cavity, optics, synchrotron

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

laser, gun, linac, simulation

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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MOP062

Technology Maturation for the MaRIE 1.0 X-FEL

linac, FEL, simulation, laser

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

quadrupole, electron, space-charge, experiment

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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MOP067

Transverse Emittance-Preserving Transfer Line and Arc Compressor for High Brightness Electron Sources

dipole, optics, electron, FEL

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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MOP076

Free-Electron Laser Driven by a 500 MeV Laser Plasma Accelerator Beam

FEL, undulator, laser, plasma

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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MOP079

On the Importance of Electron Beam Brightness in High Gain Free Electron Lasers

FEL, electron, undulator, brightness

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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MOD01

Review of Experimental Results from High Brightness DC Guns: Highlights in FEL Applications

gun, cathode, FEL, brightness

269

N. Nishimori
JAEA, Ibaraki-ken, Japan

Funding: This work is partially supported by a JSPS Grant-in-Aid for Scientific Research in Japan (15H03594).
Future ERL light sources and high repetition rate X-ray FELs require high-brightness and high-current electron guns. A DC photoemission gun is one of the most promising candidates for such guns, because a record high current of 65 mA and generation of high brightness beam with 90% normalized emittances of 0.3 mm-mrad with bunch charge of 77 pC were recently demonstrated at the Cornell photoinjector with a 350 kV photoemission gun [1,2]. Further increase of the gun high voltage is desirable to reduce space charge induced emittance growth especially for high bunch charge application such as X-ray FEL. Employment of a segmented insulator is a key to reach higher voltage [3]. This technique led to generation of 500 keV beam from the JAEA gun with 160mm acceleration gap [4], conditioning voltage more than 500 kV at the Cornell gun with gap < 50 mm [5], and demonstration of 500 kV holding for 10 hours at the KEK gun with 70 mm gap [6]. In this talk, we present recent experimental results of high brightness DC guns and discuss highlights and limitations in FEL applications.
[1] Dunham, APL 102, 034105.
[2] Gulliford, PRSTAB 16, 073401.
[3] Nagai, RSI 81, 033304.
[4] Nishimori, APL 102, 234103.
[5] Maxson, RSI 85, 093306.
[6] Yamamoto, private communication.

Slides MOD01 [3.051 MB]

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MOD04

Emittance Measurements of the Electron Beam at PITZ for the Commissioning Phase of the European X-FEL

laser, electron, simulation, gun

285

G. Vashchenko, P. Boonpornprasert, J.D. Good, M. Groß, H. Huck, I.I. Isaev, D.K. Kalantaryan, G. Kourkafas, M. Krasilnikov, D. Malyutin, D. Melkumyan, A. Oppelt, M. Otevřel, Y. Renier, T. Rublack, F. Stephan
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
M. A. Bakr
Assiut University, Assiut, Egypt
C. Hernandez-Garcia
JLab, Newport News, Virginia, USA
O. Lishilin, G. Pathak
Uni HH, Hamburg, Germany
Q.T. Zhao
IMP/CAS, Lanzhou, People's Republic of China

For the operation of free electron lasers (FELs) like the European X-FEL and FLASH located at DESY, Hamburg Site, high quality electron beams are required already from the source. The Photo Injector Test facility at DESY, Zeuthen Site (PITZ) was established to develop, characterize and optimize electron sources for such FELs. Last year the work at PITZ focused on the optimization of a photo injector operated with the startup parameters of the European X-FEL. This implies photocathode laser pulses with a Gaussian temporal profile of about 11-12 ps FWHM to drive the photo gun operated at a gradient of 53 MV/m. Significant effort was spent on the electron beam characterization and optimization for various bunch charges. Emittance measurements were performed as a function of major accelerator parameters such as main solenoid current, laser spot size on the cathode and the gun launching phase. The requirement on the beam emittance for bunch charge of 500 pC for the European XFEL commissioning phase has been demonstrated. Results of these studies accompanied with the corresponding simulations are presented in this paper.

Slides MOD04 [1.603 MB]

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TUP007

High Fidelity Start-to-end Numerical Particle Simulations and Performance Studies for LCLS-II

undulator, electron, FEL, simulation

342

G. Marcus, Y. Ding, P. Emma, Z. Huang, T.O. Raubenheimer, L. Wang
SLAC, Menlo Park, California, USA
J. Qiang, M. Venturini
LBNL, Berkeley, California, USA

High fidelity numerical particle simulations that leverage a number of accelerator and FEL codes have been used to analyze the LCLS-II FEL performance. Together, the physics models that are included in these codes have been crucial in identifying, understanding, and mitigating a number of potential hazards that can adversely affect the FEL performance, some of which are discussed in papers submitted to this conference[*, **]. Here, we present a broad overview of the LCLS-II FEL performance, based on these start-to-end simulations, for both the soft X-ray and hard X-ray undulators including both SASE and self-seeded operational modes.
* M. Venturini, et al., The microbunching instability and LCLS-II lattice design: lessons learned, FEL'15
** Z. Zhang, et al., Microbunching-induced sidebands in a seeded free-electron laser, FEL'15

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TUP013

The X-Band FEL Collaboration

FEL, undulator, linac, electron

368

J. Pfingstner, E. Adli
University of Oslo, Oslo, Norway
A.A. Aksoy, O. Yavaş
Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey
D. Angal-Kalinin, J.A. Clarke
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
C.J. Bocchetta, A.I. Wawrzyniak
Solaris, Kraków, Poland
M.J. Boland, T.K. Charles, R.T. Dowd, G. LeBlanc, Y.E. Tan, K.P. Wootton, D. Zhu
SLSA, Clayton, Australia
G. Burt
Lancaster University, Lancaster, United Kingdom
N. Catalán Lasheras, A. Grudiev, A. Latina, D. Schulte, S. Stapnes, I. Syratchev, W. Wuensch
CERN, Geneva, Switzerland
A. Charitonidis
NTUA, Athens, Greece
G. D'Auria, S. Di Mitri, C. Serpico
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
T.J.C. Ekelöf, M. Jacewicz, R.J.M.Y. Ruber, V.G. Ziemann
Uppsala University, Uppsala, Sweden
W. Fang, Q. Gu
SINAP, Shanghai, People's Republic of China
E.N. Gazis
National Technical University of Athens, Athens, Greece
X.J.A. Janssen
VDL ETG, Eindhoven, The Netherlands
Z. Nergiz
Nigde University, Nigde, Turkey

The X-band FEL collaboration is currently designing an X-ray free-electron laser based on X-band acceleration technology. Due to the higher accelerating gradients achievable with X-band technology, a X-band normal conducting linac can be shorter and therefore potentially cost efficient than what is achievable with lower frequency structures. This cost reduction of future FEL facilities addresses the growing demand of the user community for coherent X-rays. The X-band FEL collaboration consists of 12 institutes and universities that jointly work on the preparation of design reports for the specific FEL projects. In this paper, we report on the on-going activities, the basic parameter choice, and the integrated simulation results. We also outline the interest of the X-band FEL collaboration to use the electron linac CALIFES at CERN to test FEL concepts and technologies relevant for the X-band FEL collaboration.

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TUP021

Fundamental Limitations of the SASE FEL Photon Beam Pointing Stability

FEL, radiation, electron, undulator

397

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

The radiation from SASE FEL has always limited value of the degree of transverse coherence. Two effects define the spatial coherence of the radiation: the mode competition effect, and the effect of poor longitudinal coherence. For the diffraction limited case we deal mainly with the effect of the poor longitudinal coherence leading to significant degradation of the spatial coherence in the post-saturation regime. When transverse size of the electron beam significantly exceeds diffraction limit, the mode competition effect does not provide the selection of the fundamental FEL mode, and spatial coherence degrades due to contribution of the higher azimuthal modes. Another consequence of this effect are fluctuations of the spot size and pointing stability of the photon beam. These fluctuations are fundamental and originate from the shot noise in the electron beam. The effect of pointing instability becomes more pronouncing for shorter wavelengths. Our study is devoted to the fundamental analysis of the effect and description of possible means for improving the degree of transverse coherence and the pointing stability.

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TUP035

Operation of a Slit Emittance Meter in the MAX IV Gun Test Stand

gun, cathode, laser, background

444

J. Andersson, F. Curbis, M. Isinger, F. Lindau, S. Werin
MAX-lab, Lund, Sweden

The MAX IV facility in Lund, Sweden is currently under commissioning. There are two guns in the current MAX IV injector, one thermionic gun for storage ring injection and one photocathode gun for the Short Pulse Facility. There is a possibility of extending the facility to include a Free Electron Laser. To investigate how the beam from the injector can be improved and how to match it to the future requirements for a FEL, the emittance meter from SPARC has been recommissioned at the MAX IV gun test stand. In this paper we report on the progress of this work and results from the first measurements.

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TUP036

Initial Commissioning Results of the MAX IV Injector

gun, linac, laser, cathode

448

J. Andersson, F. Curbis, M. Eriksson, D. Kumbaro, F. Lindau, E. Mansten, D.F. Olsson, S. Thorin, S. Werin
MAX-lab, Lund, Sweden

The MAX IV facility in Lund, Sweden is currently under commissioning. In the MAX IV injector there are two guns, one thermionic gun for storage ring injection and one photocathode gun for the Short Pulse Facility. The commissioning of the injector and the LINAC has been ongoing for the last year and ring commissioning is due to start shortly. In this paper we will present the results from beam performance experiments for the injector at the current stage of commissioning.

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TUP040

Simulation and Design of Low Emittance RF Electron Gun

electron, gun, cavity, coupling

455

C. Saisa-ard, S. Rimjaem
Chiang Mai University, Chiang Mai, Thailand

Funding: This work has been supported by the CMU Junior Research Fellowship Program and the Department of Physics and Materials Science, Faculty of Science, Chiang Mai University.
Generation of high-brightness electron beam is one of the most critical issues in development of advanced electron accelerators and light sources. At the Plasma and Beam Physics (PBP) Research Facility, Chiang Mai University, a low emittance RF electron gun is under the development. This RF-gun is planned to be used as an electron source for a future IR/THz FEL facility. An extra resonant cavity is added to the modified design of the existing PBP-CMU RF-gun in order to reduce the transverse sliced emittance. This cell is coupled to the main full-cell via a side-coupling cavity. The electromagnetic field distributions inside the cavities are simulated by using the CST Microwave Studio 2012. Then, beam dynamic simulations utilizing the program PARMELA are performed. Both RF and beam dynamic simulation results are reported and discussed in this contribution.
The authors would like to acknowledge the financial support to participate this conference by the Department of Physics and Materials Science and the Graduate School, Chiang Mai University.

Poster TUP040 [2.140 MB]

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TUP065

Beam Dynamics Simulation for the Upgraded PITZ Photo Injector Applying Various Photocathode Laser Pulses

laser, electron, flattop, cathode

501

M. A. Bakr, M. Khojoyan, M. Krasilnikov, F. Stephan, G. Vashchenko
DESY Zeuthen, Zeuthen, Germany
M. A. Bakr
Assiut University, Assiut, Egypt

The Photo Injector Test facility PITZ at DESY, Zeuthen site, characterizes and optimizes high brightness electron sources for linac-based Free Electron Laser (FELs) with a specific focus on the requirements of FLASH and the European XFEL. X-ray FELs require high brightness electron beam in terms of high peak current, small transverse emittance and energy spread. Such high quality beams are mandatory for efficient SASE generation in a single pass through long undulators with narrow gaps. Photocathode laser pulse shaping is a powerful tool to optimize the photo injector performance. Recently, a new photocathode laser system capable of producing 3D quasi-ellipsoidal pulses has been installed at PITZ. It is foreseen to operate this new system in parallel to the nominal one that generates cylindrical pulses with various temporal profiles. A set of numerical simulations was performed to study and compare the beam dynamics of electron beams produced with 3D ellipsoidal laser profile with the typical cylindrically shaped (flat-top) profile. Different bunch charges from 20 pC up to several nC are considered, in order to find an optimum PITZ machine setup which will yield the lowest transverse emittance. we present and discuss the results of this comparison in the submission.

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TUP068

Electron Beam Phase Space Tomographie at the European XFEL Injector

electron, optics, quadrupole, betatron

515

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

Transverse emittances as well as the energy spread and the peak current of the electron bunches are important parameters for high-gain free electron lasers such as the European XFEL. Investigations of the 6D phase space characterisation would give important indications to optimise the beam quality for SASE operation. The injector of the European XFEL includes, inter alia, a laser heater, a transverse deflecting cavity, a spectrometer, a diagnostic section with four OTR screens as well as several quadrupole magnets. In this paper, we will discuss the possibilities to characterise the 6D phase space of the electron beam in the injector of the Eurpean XFEL.

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WEP002

Simulating Single Crystal Copper Photocathode Emittance

simulation, electron, FEL, laser

587

T. Vecchione
SLAC, Menlo Park, California, USA

Funding: US DOE contract DE-AC02-76SF00515
The performance of free-electron lasers depends on the quality of the electron beam used. In some cases this performance can be improved by optimizing the choice of photocathode with respect to emittance. With this in mind, electronic structure calculations have been included in photoemission simulations and used to predict the emittance from single crystal copper photocathodes. The results from different low-index surfaces are reported. Within the model assumptions the Cu(100) surface was identified as having minimal emittance, particularly when illuminated by 266 nm light and extracted in a 60 MV/m gradient. These findings may guide future experimental work, leading to improved machine performance.

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WEP003

Recent Understanding and Improvements of the LCLS Injector

laser, cathode, FEL, electron

592

F. Zhou, D.K. Bohler, Y. Ding, S. Gilevich, Z. Huang, H. Loos, D.F. Ratner
SLAC, Menlo Park, California, USA

Funding: U.S. DOE contract No. DE-AC02-76SF00515.
Ultraviolet drive laser and copper photocathode are the key systems for reliably delivering <0.4 micron of emittance and high brightness free electron laser (FEL) at the linac coherent light source (LCLS). Characterizing, optimizing and controlling laser distributions in both spatial and temporal directions are important for ultra-low emittance generation. Spatial truncated Gaussian laser profile has been demonstrated to produce better emittance than a spatial uniform beam. Sensitivity of the spatial laser distribution for the emittance is measured and analysed. Stacking two 2-ps Gaussian laser beams significantly improves emittance and eventually FEL performance at the LCLS in comparison to a single 2-ps Gaussian laser pulse. In addition, recent observations at the LCLS show that the micro-bunching effect depends strongly on the cathode spot locations. The dependence of the micro-bunching and FEL performance on the cathode spot location is mapped and discussed.

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WEP058

Emittance Measurements at the PAL-XFEL Injector Test Facility

laser, quadrupole, gun, electron

690

J. Lee
POSTECH, Pohang, Kyungbuk, Republic of Korea
J.H. Han, J.H. Hong, C.H. Kim, I.S. Ko, S.J. Lee, S.J. Park, H. Yang
PAL, Pohang, Kyungbuk, Republic of Korea

The PAL-XFEL Injector Test Facility (ITF) at PAL has been operating for experimental optimization of electron beam parameters and for beam test of various accelerator components. It consists of a photocathode RF gun, two S-band accelerating structures, a laser heater system, and beam diagnostics such as ICTs, BPMs, screens, beam energy spectrometers and an RF deflector. Projected and slice emittance measurements were carried out by using single quadrupole scan. In this paper, we present the emittance measurements.

Poster WEP058 [0.646 MB]

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WEP061

Numerical and Experimental Studies on Electron Beam Properties from Asymmetric RF-gun

gun, electron, linac, simulation

698

S. Rimjaem, N. Chaisueb, J. Saisut, C. Thongbai, W. Thongpakdi
Chiang Mai University, Chiang Mai, Thailand
N. Kangrang
FNRF, Chiang Mai, Thailand
E. Kongmon, K. Kosaentor, P. Wichaisirimongkol
IST, Chiang Mai, Thailand

Funding: This work has been supported by the CMU Junior Research Fellowship Program, and the Department of Physics and Materials Science, Faculty of Science, Chiang Mai University.
The electron linear accelerator at the Plasma and Beam Physics Research Facility (PBP-CMU Linac), Chiang Mai University, Thailand, is used to produce femtosecond electron bunches for generation of THz radiation. The main components of the PBP-CMU Linac are a thermionic RF electron gun, an alpha magnet, a travelling wave linac structure, quadrupole lens, steering magnets, and various diagnostic components. The RF-gun consists of a 1.6 S-band standing wave structure and a side-coupling cavity. The 2856 MHz RF wave is transmitted from the klystron to the gun through a rectangular waveguide input-port. Both the RF input-port and the side-coupling cavity cause an asymmetric electromagnetic field distribution inside the gun. The electron beam from the RF-gun has asymmetric transverse shape with an emittance value, which is higher than the beam from the symmetric fields. The problems are increased when the beam is transported from the gun through the whole accelerator system. Beam dynamic simulations are performed to investigate the effect of the asymmetric fields on the electron properties by using the codes PARMELA and ELEGANT. An integrated electron beam diagnostic station to measure the beam properties will be installed in the system to investigate these effects. Results from numerical and experimental studies are reported in this contribution.

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WEP069

Minimization of the Emittance Growth Induced by Coherent Synchrotron Radiation in Arc Compressor

dipole, synchrotron-radiation, simulation, synchrotron

711

X.Y. Huang, X. Cui, Y. Jiao, G. Xu
IHEP, Beijing, People's Republic of China

Funding: Supported by National Natural Science Foundation of China (11475202, 11405187).
Coherent synchrotron radiation (CSR) is a critical issue when electron bunches with short bunch length and high peak current transporting through a bending system in high-brightness light sources and linear colliders. For example, a high peak current of electron beam can be achieved by using magnetic bunch compressor, however, CSR induced transverse emittance growth will limit the performance of bunch compressor. In this paper, based on our 'two-dimensional point-kick analysis', an arc compressor with high compression factor is studied. Through analytical and numerical research, an easy optics design technique is introduced that could minimize the emittance dilution within this compressor. It is demonstrated that the strong compression of bunch length and the transverse emittance preservation can be achieved at the same time.

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WEP070

Start-to-End Simulation of the LCLS-II Beam Delivery System with Real Number of Electrons

FEL, linac, electron, simulation

714

J. Qiang, C.E. Mitchell, C. F. Papadopoulos, M. Venturini
LBNL, Berkeley, California, USA
Y. Ding, P. Emma, Z. Huang, G. Marcus, Y. Nosochkov, T.O. Raubenheimer, L. Wang, M. Woodley
SLAC, Menlo Park, California, USA

The LCLS-II as a next generation high repetition rate FEL based X-ray light source will enable significant scientific discoveries. In this paper, we report on the progress in the design of the accelerator beam delivery system through start-to-end simulations. We will present simulation results for three cases, 20 pC, 100 pC and 300 pC that are transported through the hard X-ray line and the soft X-ray line for FEL radiation.

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