FEL2014 - List of Keywords (experiment)

Paper	Title	Other Keywords	Page
MOA01	Remembering Samuel Krinsky	FEL, electron, laser, free-electron-laser	1
	L.-H. Yu BNL, Upton, Long Island, New York, USA
	The presentation recalls the person, life, and achievements of Samuel Krinsky, who passed away this year.
	Slides MOA01 [5.784 MB]

MOB02	Small-scale Accelerator-based Radiation Sources and Their Applications	FEL, electron, target, free-electron-laser	14
	Y.U. Jeong KAERI, Daejon, Republic of Korea
	Small-scale accelerator-based radiation sources can be used more widely for developing advanced technologies and exploring new science with high convenience and low cost. Sometimes they are competitive comparing with giant facilities like X-ray free-electron lasers (X-FELs). We have developed a table-top terahertz (THz) FEL for substituting X-ray or millimeter-wave-based security imaging technologies (body scanners) and a laboratory-scale ultrashort electron accelerator for investigating femtosecond dynamics of atoms or molecules with pump-probe experiments. I will present on the status of the development of the small-scale radiation sources and plans for the pump-probe experiments. Additionally recent research results on biological study with the operating KAERI (Korea Atomic Energy Research Institute) THz FEL will be given.
	Slides MOB02 [32.237 MB]

MOP023	Development of a Magnetic System to Cancel the Attractive Force toward Structural Reform of Undulators	undulator, multipole, vacuum, synchrotron	75
	R. Kinjo, T. Tanaka RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan A. Kagamihata, T. Seike JASRI/SPring-8, Sayo-gun, Japan S. Yamamoto KEK, Tsukuba, Japan
	As part of a development on a compact and lightweight structure toward structural reform of undulators, cancellation of magnetic attractive force is being studied. Undulators usually require rigid mechanical components and frames to control the magnet gap precisely against the large attractive force in between. If the attractive force is canceled out near the point of load, the requirement for the undulator structure is relaxed and the cost and lead time of construction and installation are saved largely. For that purpose, we have proposed to add periodically-magnetized monolithic magnets beside the main magnets, which are expected to generate a repulsive force having the same gap-dependency as the attractive force in a cost-effective way. In the conference, the present status of the development of the force cancellation system will be presented, with a focus on the result of preliminary experiments using the periodically-magnetized magnets. Also introduced will be a development plan for the compact and lightweight undulator based on the cancellation system.

MOP046	Undulator Radiation Damage Experience at LCLS	undulator, radiation, electron, operation	127
	H.-D. Nuhn, R.C. Field, Yu.I. Levashov, X.S. Mao, M. Santana-Leitner, J.J. Welch, Z.R. Wolf SLAC, Menlo Park, California, USA
	Funding: Work supported by U.S. Department of Energy contract DE-AC02-76SF00515 The SLAC National Accelerator Laboratory has been running the Linac Coherent Light Source (LCLS), the first x-ray Free Electron Laser since 2009. Undulator magnet damage from radiation, produced by the electron beam traveling through the 133-m long straight vacuum tube, has been and is a concern. A damage measurement experiment has been performed in 2007 in order to obtain dose versus damage calibrations. Radiation reduction and detection devices have been integrated into the LCLS undulator system. The accumulated radiation dose rate was continuously monitored and recorded. In addition, undulator segments have been routinely removed from the beamline to be checked for magnetic (50 ppm, rms) and mechanic (about 0.25 μm, rms) changes. A reduction in strength of the undulator segments is being observed, at a level, which is now clearly above the noise. Recently, potential sources for the observed integrated radiation levels have been investigated. The paper discusses the results of these investigation as well as comparison between observed damage and measured dose accumulations and discusses, briefly, strategies for the new LCLS-II upgrade, which will be operating at more than 300 times larger beam rate.

MOP070	Design Study for the PEHG Experiment at SDUV-FEL	electron, FEL, bunching, simulation	219
	C. Feng, H.X. Deng, B. Liu, D. Wang, X.T. Wang, M. Zhang, T. Zhang, W. Zhang, Z.T. Zhao SINAP, Shanghai, People's Republic of China
	Funding: This work was partially supported by National Natural Science Foundation of China (11475250, 11175240 and 11205234) In this paper, design studies for the proof-of-principle experiment of the recently proposed phase-merging enhanced harmonic generation (PEHG) mechanism are presented. A dogleg and a new designed transverse gradient undulator should be added in the undulator system of SDUV-FEL to perform the phase-merging effect. With the help of 3D simulation codes, we show the possible performance of PEHG with the realistic parameters of SDUV-FEL. * H. Deng, C. Feng, Phys. Rev. Lett. 111, 084801. C. Feng, H. Deng, D. Wang, Z. Zhao, New J. Phys.,16, 043021. * C. Feng, T. Zhang, H. Deng, Z. Zhao, Phys. Rev. ST Accel. Beams 17, 070701.

MOP077	Measurements of the FEL-bandwidth Scaling with Harmonic Number in a HGHG FEL	FEL, laser, electron, operation	227
	E. Allaria, M.B. Danailov, W.M. Fawley, E. Ferrari, L. Giannessi 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
	In this work we report recent measurements done at FERMI showing the dependence of the FEL bandwidth with respect to the seed laser harmonic at which the FEL is operated. Comparison of FEL spectra for different Fourier-limit seed and chirp pulses is also reported.

MOP078	Measurements of FEL Polarization at FERMI	polarization, FEL, radiation, electron	231
	E. Allaria Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	We report detailed quantitative characterization of different polarization states of a single-pass, externally-seeded FEL operating with variable polarization undulators in the VUV spectral range. The experiment has been performed at FERMI FEL-1 operated in the 52–26 nm wavelength range. Three different, independent polarimeter setups, installed at the end of ex- perimental beamlines, have been used to characterize the four “pure” polarization states: horizontal, vertical, right-circular and left-circular. The impact of downstream transport optics upon the radia- tion polarization has been assessed; at longer wavelengths, dichroism effects lead to a non-negligible ellipticity for an originally circularly polarized state. The results from the different polarimeter setups validate each other and allow a cross-calibration of the instruments. On behalf of the team organized for polarization measurements at FERMI.

MOP094	Indirect Measurements of NIR and UV Ultrashort Seed Laser Pulses using a Transverse Deflecting RF-Structure	laser, electron, undulator, interaction-region	272
	N. Ekanayake, S. Ackermann DESY, Hamburg, Germany S. Ackermann, C. Lechner, Th. Maltezopoulos, T. Plath Uni HH, Hamburg, Germany K.E. Hacker DELTA, Dortmund, Germany
	Seeding of free-electron lasers (FELs) using external coherent optical pulses recently became an area of interest as users demand spectrally and temporally coherent FEL radiation which is not achievable in traditional self-amplified spontaneous emission operation mode. Since temporal and spectral properties of the seed laser pulses are directly imprinted on the electron bunch, a proper characterization of these seed pulses is needed. However, the lack of any measurement technique capable of characterizing ultrashort seed laser pulses at the laser-electron interaction region is a primary drawback. In this paper we report indirect measurements of seed laser pulses in an undulator section using a transverse deflecting RF-structure (TDS-LOLA) at the free-electron laser FLASH at DESY. Temporally chirped and unchirped seed pulse length measurements will be compared with second-harmonic generation frequency-resolved optical gating measurements and theoretical simulations. Using this technique we will demonstrate that pulse artifacts such as pre- and post-pulses in the seed pulse in the femtosecond and picosecond timescales can be identified without any temporal ambiguity. Authors acknowledge the support received from FLASH team and many groups at DESY in preparation and commissioning of experiments. We thank our colleagues in the FLASH seeding team for their support.

TUB01	Review of Coherent SASE Schemes	electron, undulator, FEL, bunching	327
	B.W.J. MᶜNeil, L.T. Campbell, J. Henderson USTRAT/SUPA, Glasgow, United Kingdom D.J. Dunning, N. Thompson STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Funding: We acknowledge STFC Agreement No. 4163192; ARCHIE-WeSt HPC, EPSRC grant EP/K000586/1; John von Neumann Institute for Computing (NIC) on JUROPA at Julich Supercomputing Centre (JSC), project HHH20 A review is presented of some of the methods and their origins that have recently been proposed to improve the temporal coherence of SASE output. These methods do not require any external laser seed field, or the use of the so-called self-seeding methods, where the SASE radiation is optically filtered and improved at an early stage of the interaction before re-injection and amplification to saturation. By using methods that introduce an additional relative propagation between the electron beam and the radiation field, the localised collective interaction, which leads to the formation of the ‘spiking’ associated with normal SASE output, is removed. The result is output pulses which are close to the fourier transform limit without the need for any external seeds or intermediate optics.
	Slides TUB01 [6.256 MB]

TUB03	FEL Overcompression in the LCLS	electron, simulation, FEL, diagnostics	337
	J.L. Turner, F.-J. Decker, Y. Ding, Z. Huang, R.H. Iverson, J. Krzywinski, H. Loos, A. Marinelli, T.J. Maxwell, H.-D. Nuhn, D.F. Ratner, T.J. Smith, J.J. Welch, F. Zhou SLAC, Menlo Park, California, USA
	Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515 Overcompression of the Linac Coherent Light Source (LCLS) x-ray Free Electron Laser (FEL) at the SLAC National Accelerator Center is studied. The studies and operational implications are summarized in this talk.
	Slides TUB03 [4.493 MB]

TUP020	MINERVA, a New Code to Model Free-Electron Lasers	FEL, undulator, electron, simulation	408
	H. Freund, P.J.M. van der Slot CSU, Fort Collins, Colorado, USA P.J.M. van der Slot Mesa+, Enschede, The Netherlands
	Simulation codes modelling the interaction of electrons with an optical field inside an undulator are an essential tool for understanding and designing free-electron lasers (FELs). As there exists a large variety of FELs ranging from long-wavelength oscillators using partial wave guiding to soft and hard x-ray FELs that are either seeded or starting from noise, a simulation code should be capable of modelling this huge variety of FEL configurations. A new code under development, named MINERVA, will be capable of modelling such a large variety of FELs. The code uses a modal expansion for the optical field, e.g., a Gaussian expansion for free-space propagation, and an expansion in waveguide modes for propagation at long wavelengths, or a combination of the two for partial guiding at THz frequencies. MINERVA uses the full Newton-Lorentz force equation to track the particles through the optical and magnetic fields. To allow propagation of the optical field outside the undulator and interact with optical elements, MINERVA interfaces with the optical propagation code OPC to model oscillators. Here we describe the main features of MINERVA and give various examples of its capabilities.

TUP036	Observation of Smith-Purcell Radiation at 32 GHz from a Multi-channel Grating with Sidewalls	radiation, simulation, electron, free-electron-laser	470
	J.T. Donohue CENBG, Gradignan, France J. Gardelle, P. Modin CEA, LE BARP cedex, France
	In a demonstration experiment at 5 GHz, we found copious emission of coherent Smith-Purcell (SP) radiation at the fundamental frequency of the evanescent surface wave, when the grating had sidewalls. Reaching higher frequencies requires a reduction in the size of the grating, which leads to a considerable reduction in power. To partially compensate this, we suggested superposing several copies of the reduced grating in parallel. A test of this concept has been performed with a seven-channel grating, at a frequency near 32 GHz. The SP radiation signals were observed directly with a fast oscilloscope. Power levels were of order 5 kW, in fair agreement with three-dimensional simulations made using the code "MAGIC".

TUP042	High Efficiency Lasing with a Strongly Tapered Undulator	undulator, laser, electron, radiation	478
	J.P. Duris, P. Musumeci UCLA, Los Angeles, California, USA
	Funding: This work was supported by DOE grant DE-FG02-92ER40693, Defense of Threat Reduction Agency award HDTRA1-10-1-0073 and University of California Office of the President award 09-LR-04-117055-MUSP. Typical electrical to optical energy conversion efficiencies for FELs are limited by the Pierce parameter to 10^-3 or smaller. Undulator tapering schemes have enabled extraction of as much as 1 or 2% of the electron energy. Recently, the UCLA BNL helical inverse free electron laser (IFEL) experiment at ATF demonstrated energy doubling and acceleration of 30% of an electron beam from 52 to 93 MeV with a modest 10¹¹ W power CO2 laser pulse. By reversing and retuning the undulator, the electrons may be violently decelerated, thereby transferring energy from the beam to the laser pulse. Simulations show that by sending a 1 kA, 70 MeV electron beam and 100 GW laser into a prebuncher and the reversed undulator, 41% of the electron beam energy should be converted to radiation, allowing the laser pulse power to grow to 127 GW.

TUP060	Potential Photochemical Applications of the Free Electron Laser Irradiation Technique in Living Organisms	FEL, radiation, electron, laser	505
	F. Shishikura, K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Sakai, T. Tanaka LEBRA, Funabashi, Japan T. Kii, H. Ohgaki, H. Zen Kyoto University, Kyoto, Japan T. Sakae Nihon University School of Dentistry at Matsudo, Matsudo-shi, Japan
	In 2001, the Laboratory for Electron Beam Research and Application (LEBRA) achieved the first lasing of 0.9–6.5 microns near-infrared free electron lasers (FELs), in which higher harmonics were generated by using nonlinear optical crystals. Following this breakthrough, we have paid considerable attention to LEBRA-FEL’s potential for investigating photochemical reactions in living organisms. We have established a micro-irradiation technique using an optical fiber connected to a fine tapered glass rod of <5 microns in diameter, enabling FEL irradiation of a single cell and even the inner organelles of live cells. We then verified that visible LEBRA-FEL light can control the germination of lettuce seeds, a well-known photochemical reaction, and determined that red light (660 nm FEL) promotes germination and far-red light (740 nm FEL) inhibits it. Here, we summarize the efficiency of various visible wavelengths of LEBRA-FEL light, ranging from 0.4–0.8 microns, for regulating photoreactions in lettuce seeds and we also summarize the efficiency of infrared wavelengths up to 20 microns, which can be generated by combined use of the LEBRA-FEL and the Kyoto University FEL. We thank the staff of Prof. T. Morii (Institute of Advanced Energy, Kyoto Univ.) for helpful assistance.

TUP082	Coherent Harmonic Generation at the DELTA Storage Ring: Towards User Operation	electron, laser, radiation, undulator	556
	A. Meyer auf der Heide, S. Hilbrich, H. Huck, M. Huck, M. Höner, S. Khan, C. Mai, R. Molo, H. Rast, A. Schick, P. Ungelenk DELTA, Dortmund, Germany
	Funding: Work supported by DFG, BMBF, FZ Jülich, and by the Land NRW. At DELTA, a 1.5-GeV synchrotron light source at the TU Dortmund University, a short-pulse facility based on Coherent Harmonic Generation (CHG) is in operation and shall soon be used for pump-probe experiments. Due to the interaction of ultrashort laser pulses with electron bunches in an undulator, CHG provides short and coherent pulses at harmonics of the laser wavelength. In this paper, recent progress towards user operation, pulse characterization studies such as transverse and longitudinal coherence measurements as well as CHG in the presence of an RF phase modulation are presented.

TUP085	FERMI Status Report	FEL, electron, laser, operation	564
	M. Svandrlik, E. Allaria, F. Bencivenga, C. Callegari, F. Capotondi, D. Castronovo, P. Cinquegrana, M. Coreno, R. Cucini, I. Cudin, G. D'Auria, M.B. Danailov, R. De Monte, G. De Ninno, P. Delgiusto, A.A. Demidovich, S. Di Mitri, B. Diviacco, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, E. Ferrari, P. Finetti, L. Fröhlich, P. Furlan Radivo, G. Gaio, D. Gauthier, F. Gelmetti, L. Giannessi, M. Kiskinova, S. Krecic, M. Lonza, N. Mahne, C. Masciovecchio, M. Milloch, F. Parmigiani, G. Penco, L. Pivetta, O. Plekan, M. Predonzani, E. Principi, L. Raimondi, P. Rebernik Ribič, F. Rossi, L. Rumiz, C. Scafuri, C. Serpico, P. Sigalotti, C. Spezzani, C. Svetina, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	FERMI, the seeded FEL located at the Elettra laboratory in Trieste, Italy, is now in regular operation for users with its first FEL line, FEL-1, which covers the wavelength range between 100 and 20 nm. We will give an overview of the typical operating modes of the facility for users and we will report on the status of beamlines and experimental stations. Three beamlines are now opened for users, three more are in construction. Meanwhile, the second FEL line of FERMI, FEL-2, a HGHG double stage cascade covering the wavelength range 20 to 4 nm is still under commissioning; we will report on the latest results in particular at the shortest wavelength, 4 nm in the fundamental.

WEA04	First Lasing from a High Power Cylindrical Grating Smith-Purcell Device	electron, radiation, simulation, cathode	611
	H. Bluem, R.H. Jackson, J.D. Jarvis, A.M.M. Todd AES, Medford, New York, USA J.T. Donohue CENBG, Gradignan, France J. Gardelle, P. Modin CEA, LE BARP cedex, France
	Funding: Work supported by ONR under Contract No. N00014-10-C-0191 and N62909-13-1-N62. Many applications of THz radiation remain impractical or impossible due to an absence of compact sources with sufficient power. A source where the interaction occurs between an annular electron beam and a cylindrical grating is capable of generating high THz power in a very compact package. The strong beam bunching generates significant power at the fundamental frequency and harmonics. A collaboration between Advanced Energy Systems and CEA/CESTA has been ongoing in performing proof-of-principle tests on cylindrical grating configurations producing millimeter wave radiation. First lasing was achieved in such a device. Further experiments performed with a 6 mm period grating produced fundamental power at 15 GHz, second harmonic power at 30 GHz and although not measured, simulations show meaningful third harmonic power at 45 GHz. Comparison with simulations shows very good agreement and high conversion efficiency. Planned experiments will increase the frequency of operation to 100 GHz and beyond. Ongoing simulations indicate excellent performance for a device operating at a fundamental frequency of 220 GHz with realistic beam parameters at 10 kV and simple extraction of the mode.
	Slides WEA04 [2.344 MB]

THB03	Femtosecond-Stability Delivery of Synchronized RF-Signals to the Klystron Gallery over 1-km Optical Fibers	laser, timing, klystron, detector	663
	J. Kim, K. Jung, J. Lim, J. Shin, H. Yang KAIST, Daejeon, Republic of Korea H.-S. Kang, C.-K. Min PAL, Pohang, Kyungbuk, Republic of Korea
	Funding: This work was supported by the PAL-XFEL Project and the National Research Foundation (Grant number 2012R1A2A2A01005544) of South Korea. We present our recent progress in optical frequency comb-based remote optical and RF distribution system at PAL-XFEL. A 238 MHz mode-locked Er-laser is used as an optical master oscillator (OMO), which is stabilized to a 2.856 GHz RF master oscillator (RMO) using a fiber- loop optical-microwave phase detector (FLOM-PD). We partly installed a pair of 1.15 km long fiber links through a cable duct to connect and OMO room to a klystron gallery in the PAL-XFEL Injector Test Facility (ITF). The fiber links are stabilized using balanced optical cross- correlators (BOC). A voltage controlled RF oscillator (VCO) is locked to the delivered optical pulse train using the second FLOM-PD. Residual timing jitter and drift between the two independently distributed optical pulse train and RF signal is measured at the klystron gallery. The results are 6.6 fs rms and 31 fs rms over 7 hours and 62 hours, respectively. This is the first comb-based optical/RF distribution and phase comparison in the klystron gallery environment.
	Slides THB03 [7.478 MB]

THP034	Further Analysis of Corrugated Plate Dechirper Experiment at BNL-ATF	wakefield, simulation, electron, free-electron-laser	788
	M.A. Harrison, G. Andonian, P. Frigola, A.Y. Murokh, M. Ruelas, A.V. Smirnov RadiaBeam Systems, Santa Monica, California, USA M.G. Fedurin BNL, Upton, Long Island, New York, USA
	Funding: This work is supported by Department of Energy grant number DE-SC0009550. RadiaBeam Systems successfully completed testing of a proof-of-concept corrugated plate dechirper at the Brookhaven National Laboratory Accelerator Test Facility.* Such passive devices should prove indispensable for the efficient operation of future XFEL facilities. These experiments demonstrated a narrowing of the energy spectrum in chirped beam bunches at 57.6 MeV. In this paper, we compare these results with results from Elegant simulations of the BNL-ATF beam. We also compare GdfidL simulations of the wakefield with the analytic results of Bane and Stupakov.** * Harrison, M., et al "Removal of Residual Chirp in Compressed Beams Using a Passive Wakefield Technique." NaPAC13, 2013 ** K. Bane, et al "Corrugated Pipe as a Beam Dechirper," SLAC-PUB-14925, 2012

THP048	Formation of the Electron Bunch Longitudinal Profile for Coherent Electron Cooling Experiment	electron, cavity, gun, laser	840
	I. Pinayev, D. Kayran, V. Litvinenko BNL, Upton, Long Island, New York, USA
	Proof-of-princilpe experiment of the coherent electron cooling is ongoing at Brookhaven National Lab. CeC mechanism utilizes amplification of density modulation, induced by hadrons, by an FEL structure. To fully utilize electron beam cooling capacity we need uniform longitudinal beam profile. In this paper we present two frequency injector system tuned for this requirement.

THP053	Steady State Multipacting in a Micro-pulse Electron Gun	electron, cavity, cathode, gun	851
	K. Zhou, X.Y. Lu, X. Luo, S.W. Quan, Z.Q. Yang, J. Zhao PKU, Beijing, People's Republic of China
	Multipacting is a resonant electron discharge phenomenon via secondary electron emission, while micro-pulse electron gun (MPG) utilizes the multipacting current in a radio-frequency (RF) cavity to produce short pulse electron beams. The concept of MPG has been proposed for many years. However, the unstable operating state of MPG vastly obstructs its practical applications. This paper presents a study on the steady state mulitpacting in a MPG. The requirements for steady state multipacting are proposed through the analysis of the interaction between the RF cavity and the beam load. Accordingly, a MPG cavity with the frequency of 2856 MHz has been designed and constructed. Various kinds of grid-anodes are tested in our primary experiments. Both the unstable and stable multipacting current have been observed. Presently, the stable output beam current has been detected at about 12.2 mA. Further experimental study is under way now.
	Poster THP053 [2.525 MB]

THP069	Performance Study of High Bandwidth Pickups Installed at FLASH and ELBE for Femtosecond-Precision Arrival Time Monitors	pick-up, laser, electron, operation	893
	M.K. Czwalinna, C. Gerth, H. Schlarb, C. Sydlo DESY, Hamburg, Germany A. Angelovski, R. Jakoby, A. Penirschke TU Darmstadt, Darmstadt, Germany M. Gensch, M. Kuntzsch HZDR, Dresden, Germany M. Kuntzsch TU Dresden, Dresden, Germany T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany
	At today's free-electron lasers, high-resolution electron bunch arrival time measurements have become increasingly more important in fast feedback systems for a timing jitter reduction down to the femtosecond level as well as for time-resolved pump-probe experiments. This is fulfilled by arrival time monitors which employ an electro-optical detection scheme by means of synchronised ultrashort laser pulses. Even more, at FLASH and the European XFEL the measurement has to cover a wide range of bunch charges from 1 nC down to 20 pC with equally sub-10 fs resolution. To meet these requirements, recently a high bandwidth pickup electrode with a cut-off frequency above 40 GHz has been developed. These pickups are installed at the macro-pulsed SRF accelerator of the free-electron laser FLASH and at the macro-pulsed continuous wave SRF accelerator ELBE. In this paper we present an evaluation of the pickup performance by direct signal measurements with high bandwidth oscilloscopes and by use of the electro-optical arrival time monitor.

THP074	Infrared Diagnostics Instrumentation Design for the Coherent Electron Cooling Proof of Principle Experiment	wiggler, electron, FEL, ion	905
	T.A. Miller, D.M. Gassner, V. Litvinenko, M.G. Minty, I. Pinayev, B. Sheehy BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy The Coherent Electron Cooling Proof-of-Principle experiment [] based on an FEL is currently under construction in the RHIC tunnel at BNL. Diagnostics for the experimental machine [] are currently being designed, built and installed. This paper focuses on the design of the infrared diagnostic instrumentation downstream of the three tandem 2.8m long helical wiggler sections that will act on a 22MeV 68uA electron beam co-propagating with the 40GeV/u RHIC gold beam. The 14 um FEL radiation, or wiggler light, will be extracted from RHIC via a viewport in a downstream DX magnet cryostat and analysed by instrumentation on a nearby optics bench. Instruments concentrating on three parameters, namely intensity, spectral content, and transverse profile, will extract information from the wiggler light in an attempt to quantify the overlap of the electron and ion beams and act as an indicator of coherent cooling. V. Litvinkenko, et al THOBN3, PAC2011, New York, NY ** D. M. Gassner, et al WEAP01, BIW2012, Newport News, VA

THP076	Measurements of the Timing Stability at the FLASH1 Seeding Experiment	laser, electron, timing, FEL	913
	C. Lechner, A. Azima, M. Drescher, L.L. Lazzarino, Th. Maltezopoulos, V. Miltchev, T. Plath, J. Rönsch-Schulenburg, J. Roßbach, M. Wieland Uni HH, Hamburg, Germany S. Ackermann, J. Bödewadt, H. Dachraoui, N. Ekanayake, B. Faatz, M. Felber, K. Honkavaara, T. Laarmann, J.M. Mueller, H. Schlarb, S. Schreiber, S. Schulz DESY, Hamburg, Germany G. Angelova Hamberg Uppsala University, Uppsala, Sweden K.E. Hacker, S. Khan, R. Molo DELTA, Dortmund, Germany P.M. Salen, P. van der Meulen FYSIKUM, AlbaNova, Stockholm University, Stockholm, Sweden
	Funding: Supported by Federal Ministry of Education and Research of Germany under contract No. 05K10PE1, 05K10PE3, 05K13GU4 and 05K13PE3 and the German Research Foundation programme graduate school 1355. For seeding of a free-electron laser, the spatial and temporal overlap of the seed laser pulse and the electron bunch in the modulator is critical. To establish the temporal overlap, the time difference between pulses from the seed laser and spontaneous undulator radiation is reduced to a few pico-seconds with a combination of a photomultiplier tube and a streak camera. Finally, for the precise overlap the impact of the seed laser pulses on the electron bunches is observed. In this contribution, we describe the current experimental setup, discuss the techniques applied to establish the temporal overlap and analyze its stability.

THP084	Longitudinal Diagnostics of RF Electron Gun using a 2-cell RF Deflector	electron, gun, cavity, laser	929
	M. Nishiyama, K. Sakaue, T. Takahashi, T. Toida, M. Washio Waseda University, Tokyo, Japan T. Takatomi, J. Urakawa KEK, Ibaraki, Japan
	Funding: This work was supported by JSPS Grant-in-Aid for Scientific Research (A) 10001690 and the Quantum Beam Technology Program of MEXT. We have been studying a compact electron accelerator based on an S-band Cs-Te photocathode rf electron gun at Waseda University. We are using this high quality electron bunch for many application researches. It is necessary to measure the bunch length and temporal distribution for evaluating application researches and for improving an rf gun itself. Thus we adopted the rf deflector system. It kicks the electron bunch with resonated rf electromagnetic field. Using this technique, the longitudinal distribution is mapped into the transverse space. The rf deflector has a 2-cell standing wave π-mode structure, operating in TM120 dipole mode at 2856 MHz. It provides a maximum vertical kick of 1.00MV with 750 kW input rf-power which is equivalent to the temporal resolution of around 58 femtoseconds bunch length. In this conference, we report the details of our rf deflector, the latest progress of longitudinal phase space diagnostics and future prospective.

THP095	Evolvement of the Laser and Synchronization System for the Shanghai DUV-FEL Test Facility	laser, electron, FEL, free-electron-laser	960
	B. Liu, L. Feng, T. Lan, X.Q. Liu, D. Wang, X.T. Wang, W.Y. Zhang, S.P. Zhong SINAP, Shanghai, People's Republic of China
	Funding: supported by the National Natural Science Foundation of China (Grant No. 11175241) Many attractive experiments including HGHG, EEHG, cascaded HGHG, chirped pulse amplification etc. are carried out or planned on the Shanghai Deep Ultra-Violet Free Electron Laser test facility. These experiments are all utilizing a laser as seed, and need precise synchronization between the electron beam and the laser pulse. We will describe the history and current status of the seeding and synchronization scheme for the SDUV-FEL together with some related experiment results in this paper.

FRA02	Wave-Mixing Experiments with Multi-colour Seeded FEL Pulses	FEL, laser, polarization, photon	985
	F. Bencivenga, A. Battistoni, F. Capotondi, R. Cucini, M.B. Danailov, G. De Ninno, M. Kiskinova, C. Masciovecchio Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	The extension of wave-mixing experiments in the extreme ultraviolet (EUV) and x-ray spectral range represents one of the major breakthroughs for ultrafast x-ray science. Essential prerequisites to develop such kind of non-linear coherent methods are the strength of the input fields, comparable with the atomic field one, as well as the high temporal coherence and stability of the photon source(s). These characteristics are easily achievable by optical lasers. Seeded free-electron-lasers (FELs) are similar in many respects to conventional lasers, hence calling for the development of wave-mixing methods. At the FERMI seeded FEL facility this ambitious task is tackled by the TIMER project, which includes the realization of a dedicated experimental end-station. The wave-mixing approach will be initially used to study collective atomic dynamics in disordered systems and nanostructures, through transient grating (TG) experiments. However, the wavelength and polarization tunability of FERMI, as well as the possibility to radiate multi-colour seeded FEL pulses, would allow to expand the range of possible scientific applications.
	Slides FRA02 [7.731 MB]

Paper

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MOA01

Remembering Samuel Krinsky

FEL, electron, laser, free-electron-laser

1

L.-H. Yu
BNL, Upton, Long Island, New York, USA

The presentation recalls the person, life, and achievements of Samuel Krinsky, who passed away this year.

Slides MOA01 [5.784 MB]

MOB02

Small-scale Accelerator-based Radiation Sources and Their Applications

FEL, electron, target, free-electron-laser

14

Y.U. Jeong
KAERI, Daejon, Republic of Korea

Small-scale accelerator-based radiation sources can be used more widely for developing advanced technologies and exploring new science with high convenience and low cost. Sometimes they are competitive comparing with giant facilities like X-ray free-electron lasers (X-FELs). We have developed a table-top terahertz (THz) FEL for substituting X-ray or millimeter-wave-based security imaging technologies (body scanners) and a laboratory-scale ultrashort electron accelerator for investigating femtosecond dynamics of atoms or molecules with pump-probe experiments. I will present on the status of the development of the small-scale radiation sources and plans for the pump-probe experiments. Additionally recent research results on biological study with the operating KAERI (Korea Atomic Energy Research Institute) THz FEL will be given.

Slides MOB02 [32.237 MB]

MOP023

Development of a Magnetic System to Cancel the Attractive Force toward Structural Reform of Undulators

undulator, multipole, vacuum, synchrotron

75

R. Kinjo, T. Tanaka
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
A. Kagamihata, T. Seike
JASRI/SPring-8, Sayo-gun, Japan
S. Yamamoto
KEK, Tsukuba, Japan

As part of a development on a compact and lightweight structure toward structural reform of undulators, cancellation of magnetic attractive force is being studied. Undulators usually require rigid mechanical components and frames to control the magnet gap precisely against the large attractive force in between. If the attractive force is canceled out near the point of load, the requirement for the undulator structure is relaxed and the cost and lead time of construction and installation are saved largely. For that purpose, we have proposed to add periodically-magnetized monolithic magnets beside the main magnets, which are expected to generate a repulsive force having the same gap-dependency as the attractive force in a cost-effective way. In the conference, the present status of the development of the force cancellation system will be presented, with a focus on the result of preliminary experiments using the periodically-magnetized magnets. Also introduced will be a development plan for the compact and lightweight undulator based on the cancellation system.

MOP046

Undulator Radiation Damage Experience at LCLS

undulator, radiation, electron, operation

127

H.-D. Nuhn, R.C. Field, Yu.I. Levashov, X.S. Mao, M. Santana-Leitner, J.J. Welch, Z.R. Wolf
SLAC, Menlo Park, California, USA

Funding: Work supported by U.S. Department of Energy contract DE-AC02-76SF00515
The SLAC National Accelerator Laboratory has been running the Linac Coherent Light Source (LCLS), the first x-ray Free Electron Laser since 2009. Undulator magnet damage from radiation, produced by the electron beam traveling through the 133-m long straight vacuum tube, has been and is a concern. A damage measurement experiment has been performed in 2007 in order to obtain dose versus damage calibrations. Radiation reduction and detection devices have been integrated into the LCLS undulator system. The accumulated radiation dose rate was continuously monitored and recorded. In addition, undulator segments have been routinely removed from the beamline to be checked for magnetic (50 ppm, rms) and mechanic (about 0.25 μm, rms) changes. A reduction in strength of the undulator segments is being observed, at a level, which is now clearly above the noise. Recently, potential sources for the observed integrated radiation levels have been investigated. The paper discusses the results of these investigation as well as comparison between observed damage and measured dose accumulations and discusses, briefly, strategies for the new LCLS-II upgrade, which will be operating at more than 300 times larger beam rate.

MOP070

Design Study for the PEHG Experiment at SDUV-FEL

electron, FEL, bunching, simulation

219

C. Feng, H.X. Deng, B. Liu, D. Wang, X.T. Wang, M. Zhang, T. Zhang, W. Zhang, Z.T. Zhao
SINAP, Shanghai, People's Republic of China

Funding: This work was partially supported by National Natural Science Foundation of China (11475250, 11175240 and 11205234)
In this paper, design studies for the proof-of-principle experiment of the recently proposed phase-merging enhanced harmonic generation (PEHG) mechanism are presented. A dogleg and a new designed transverse gradient undulator should be added in the undulator system of SDUV-FEL to perform the phase-merging effect. With the help of 3D simulation codes, we show the possible performance of PEHG with the realistic parameters of SDUV-FEL.
* H. Deng, C. Feng, Phys. Rev. Lett. 111, 084801.
** C. Feng, H. Deng, D. Wang, Z. Zhao, New J. Phys.,16, 043021.
*** C. Feng, T. Zhang, H. Deng, Z. Zhao, Phys. Rev. ST Accel. Beams 17, 070701.

MOP077

Measurements of the FEL-bandwidth Scaling with Harmonic Number in a HGHG FEL

FEL, laser, electron, operation

227

E. Allaria, M.B. Danailov, W.M. Fawley, E. Ferrari, L. Giannessi
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

In this work we report recent measurements done at FERMI showing the dependence of the FEL bandwidth with respect to the seed laser harmonic at which the FEL is operated. Comparison of FEL spectra for different Fourier-limit seed and chirp pulses is also reported.

MOP078

Measurements of FEL Polarization at FERMI

polarization, FEL, radiation, electron

231

E. Allaria
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

We report detailed quantitative characterization of different polarization states of a single-pass, externally-seeded FEL operating with variable polarization undulators in the VUV spectral range. The experiment has been performed at FERMI FEL-1 operated in the 52–26 nm wavelength range. Three different, independent polarimeter setups, installed at the end of ex- perimental beamlines, have been used to characterize the four “pure” polarization states: horizontal, vertical, right-circular and left-circular. The impact of downstream transport optics upon the radia- tion polarization has been assessed; at longer wavelengths, dichroism effects lead to a non-negligible ellipticity for an originally circularly polarized state. The results from the different polarimeter setups validate each other and allow a cross-calibration of the instruments.
On behalf of the team organized for polarization measurements at FERMI.

MOP094

Indirect Measurements of NIR and UV Ultrashort Seed Laser Pulses using a Transverse Deflecting RF-Structure

laser, electron, undulator, interaction-region

272

N. Ekanayake, S. Ackermann
DESY, Hamburg, Germany
S. Ackermann, C. Lechner, Th. Maltezopoulos, T. Plath
Uni HH, Hamburg, Germany
K.E. Hacker
DELTA, Dortmund, Germany

Seeding of free-electron lasers (FELs) using external coherent optical pulses recently became an area of interest as users demand spectrally and temporally coherent FEL radiation which is not achievable in traditional self-amplified spontaneous emission operation mode. Since temporal and spectral properties of the seed laser pulses are directly imprinted on the electron bunch, a proper characterization of these seed pulses is needed. However, the lack of any measurement technique capable of characterizing ultrashort seed laser pulses at the laser-electron interaction region is a primary drawback. In this paper we report indirect measurements of seed laser pulses in an undulator section using a transverse deflecting RF-structure (TDS-LOLA) at the free-electron laser FLASH at DESY. Temporally chirped and unchirped seed pulse length measurements will be compared with second-harmonic generation frequency-resolved optical gating measurements and theoretical simulations. Using this technique we will demonstrate that pulse artifacts such as pre- and post-pulses in the seed pulse in the femtosecond and picosecond timescales can be identified without any temporal ambiguity.
Authors acknowledge the support received from FLASH team and many groups at DESY in preparation and commissioning of experiments. We thank our colleagues in the FLASH seeding team for their support.

TUB01

Review of Coherent SASE Schemes

electron, undulator, FEL, bunching

327

B.W.J. MᶜNeil, L.T. Campbell, J. Henderson
USTRAT/SUPA, Glasgow, United Kingdom
D.J. Dunning, N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Funding: We acknowledge STFC Agreement No. 4163192; ARCHIE-WeSt HPC, EPSRC grant EP/K000586/1; John von Neumann Institute for Computing (NIC) on JUROPA at Julich Supercomputing Centre (JSC), project HHH20
A review is presented of some of the methods and their origins that have recently been proposed to improve the temporal coherence of SASE output. These methods do not require any external laser seed field, or the use of the so-called self-seeding methods, where the SASE radiation is optically filtered and improved at an early stage of the interaction before re-injection and amplification to saturation. By using methods that introduce an additional relative propagation between the electron beam and the radiation field, the localised collective interaction, which leads to the formation of the ‘spiking’ associated with normal SASE output, is removed. The result is output pulses which are close to the fourier transform limit without the need for any external seeds or intermediate optics.

Slides TUB01 [6.256 MB]

TUB03

FEL Overcompression in the LCLS

electron, simulation, FEL, diagnostics

337

J.L. Turner, F.-J. Decker, Y. Ding, Z. Huang, R.H. Iverson, J. Krzywinski, H. Loos, A. Marinelli, T.J. Maxwell, H.-D. Nuhn, D.F. Ratner, T.J. Smith, J.J. Welch, F. Zhou
SLAC, Menlo Park, California, USA

Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515
Overcompression of the Linac Coherent Light Source (LCLS) x-ray Free Electron Laser (FEL) at the SLAC National Accelerator Center is studied. The studies and operational implications are summarized in this talk.

Slides TUB03 [4.493 MB]

TUP020

MINERVA, a New Code to Model Free-Electron Lasers

FEL, undulator, electron, simulation

408

H. Freund, P.J.M. van der Slot
CSU, Fort Collins, Colorado, USA
P.J.M. van der Slot
Mesa+, Enschede, The Netherlands

Simulation codes modelling the interaction of electrons with an optical field inside an undulator are an essential tool for understanding and designing free-electron lasers (FELs). As there exists a large variety of FELs ranging from long-wavelength oscillators using partial wave guiding to soft and hard x-ray FELs that are either seeded or starting from noise, a simulation code should be capable of modelling this huge variety of FEL configurations. A new code under development, named MINERVA, will be capable of modelling such a large variety of FELs. The code uses a modal expansion for the optical field, e.g., a Gaussian expansion for free-space propagation, and an expansion in waveguide modes for propagation at long wavelengths, or a combination of the two for partial guiding at THz frequencies. MINERVA uses the full Newton-Lorentz force equation to track the particles through the optical and magnetic fields. To allow propagation of the optical field outside the undulator and interact with optical elements, MINERVA interfaces with the optical propagation code OPC to model oscillators. Here we describe the main features of MINERVA and give various examples of its capabilities.

TUP036

Observation of Smith-Purcell Radiation at 32 GHz from a Multi-channel Grating with Sidewalls

radiation, simulation, electron, free-electron-laser

470

J.T. Donohue
CENBG, Gradignan, France
J. Gardelle, P. Modin
CEA, LE BARP cedex, France

In a demonstration experiment at 5 GHz, we found copious emission of coherent Smith-Purcell (SP) radiation at the fundamental frequency of the evanescent surface wave, when the grating had sidewalls. Reaching higher frequencies requires a reduction in the size of the grating, which leads to a considerable reduction in power. To partially compensate this, we suggested superposing several copies of the reduced grating in parallel. A test of this concept has been performed with a seven-channel grating, at a frequency near 32 GHz. The SP radiation signals were observed directly with a fast oscilloscope. Power levels were of order 5 kW, in fair agreement with three-dimensional simulations made using the code "MAGIC".

TUP042

High Efficiency Lasing with a Strongly Tapered Undulator

undulator, laser, electron, radiation

478

J.P. Duris, P. Musumeci
UCLA, Los Angeles, California, USA

Funding: This work was supported by DOE grant DE-FG02-92ER40693, Defense of Threat Reduction Agency award HDTRA1-10-1-0073 and University of California Office of the President award 09-LR-04-117055-MUSP.
Typical electrical to optical energy conversion efficiencies for FELs are limited by the Pierce parameter to 10^-3 or smaller. Undulator tapering schemes have enabled extraction of as much as 1 or 2% of the electron energy. Recently, the UCLA BNL helical inverse free electron laser (IFEL) experiment at ATF demonstrated energy doubling and acceleration of 30% of an electron beam from 52 to 93 MeV with a modest 10¹¹ W power CO2 laser pulse. By reversing and retuning the undulator, the electrons may be violently decelerated, thereby transferring energy from the beam to the laser pulse. Simulations show that by sending a 1 kA, 70 MeV electron beam and 100 GW laser into a prebuncher and the reversed undulator, 41% of the electron beam energy should be converted to radiation, allowing the laser pulse power to grow to 127 GW.

TUP060

Potential Photochemical Applications of the Free Electron Laser Irradiation Technique in Living Organisms

FEL, radiation, electron, laser

505

F. Shishikura, K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Sakai, T. Tanaka
LEBRA, Funabashi, Japan
T. Kii, H. Ohgaki, H. Zen
Kyoto University, Kyoto, Japan
T. Sakae
Nihon University School of Dentistry at Matsudo, Matsudo-shi, Japan

In 2001, the Laboratory for Electron Beam Research and Application (LEBRA) achieved the first lasing of 0.9–6.5 microns near-infrared free electron lasers (FELs), in which higher harmonics were generated by using nonlinear optical crystals. Following this breakthrough, we have paid considerable attention to LEBRA-FEL’s potential for investigating photochemical reactions in living organisms. We have established a micro-irradiation technique using an optical fiber connected to a fine tapered glass rod of <5 microns in diameter, enabling FEL irradiation of a single cell and even the inner organelles of live cells. We then verified that visible LEBRA-FEL light can control the germination of lettuce seeds, a well-known photochemical reaction, and determined that red light (660 nm FEL) promotes germination and far-red light (740 nm FEL) inhibits it. Here, we summarize the efficiency of various visible wavelengths of LEBRA-FEL light, ranging from 0.4–0.8 microns, for regulating photoreactions in lettuce seeds and we also summarize the efficiency of infrared wavelengths up to 20 microns, which can be generated by combined use of the LEBRA-FEL and the Kyoto University FEL.
We thank the staff of Prof. T. Morii (Institute of Advanced Energy, Kyoto Univ.) for helpful assistance.

TUP082

Coherent Harmonic Generation at the DELTA Storage Ring: Towards User Operation

electron, laser, radiation, undulator

556

A. Meyer auf der Heide, S. Hilbrich, H. Huck, M. Huck, M. Höner, S. Khan, C. Mai, R. Molo, H. Rast, A. Schick, P. Ungelenk
DELTA, Dortmund, Germany

Funding: Work supported by DFG, BMBF, FZ Jülich, and by the Land NRW.
At DELTA, a 1.5-GeV synchrotron light source at the TU Dortmund University, a short-pulse facility based on Coherent Harmonic Generation (CHG) is in operation and shall soon be used for pump-probe experiments. Due to the interaction of ultrashort laser pulses with electron bunches in an undulator, CHG provides short and coherent pulses at harmonics of the laser wavelength. In this paper, recent progress towards user operation, pulse characterization studies such as transverse and longitudinal coherence measurements as well as CHG in the presence of an RF phase modulation are presented.

TUP085

FERMI Status Report

FEL, electron, laser, operation

564

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

FERMI, the seeded FEL located at the Elettra laboratory in Trieste, Italy, is now in regular operation for users with its first FEL line, FEL-1, which covers the wavelength range between 100 and 20 nm. We will give an overview of the typical operating modes of the facility for users and we will report on the status of beamlines and experimental stations. Three beamlines are now opened for users, three more are in construction. Meanwhile, the second FEL line of FERMI, FEL-2, a HGHG double stage cascade covering the wavelength range 20 to 4 nm is still under commissioning; we will report on the latest results in particular at the shortest wavelength, 4 nm in the fundamental.

WEA04

First Lasing from a High Power Cylindrical Grating Smith-Purcell Device

electron, radiation, simulation, cathode

611

H. Bluem, R.H. Jackson, J.D. Jarvis, A.M.M. Todd
AES, Medford, New York, USA
J.T. Donohue
CENBG, Gradignan, France
J. Gardelle, P. Modin
CEA, LE BARP cedex, France

Funding: Work supported by ONR under Contract No. N00014-10-C-0191 and N62909-13-1-N62.
Many applications of THz radiation remain impractical or impossible due to an absence of compact sources with sufficient power. A source where the interaction occurs between an annular electron beam and a cylindrical grating is capable of generating high THz power in a very compact package. The strong beam bunching generates significant power at the fundamental frequency and harmonics. A collaboration between Advanced Energy Systems and CEA/CESTA has been ongoing in performing proof-of-principle tests on cylindrical grating configurations producing millimeter wave radiation. First lasing was achieved in such a device. Further experiments performed with a 6 mm period grating produced fundamental power at 15 GHz, second harmonic power at 30 GHz and although not measured, simulations show meaningful third harmonic power at 45 GHz. Comparison with simulations shows very good agreement and high conversion efficiency. Planned experiments will increase the frequency of operation to 100 GHz and beyond. Ongoing simulations indicate excellent performance for a device operating at a fundamental frequency of 220 GHz with realistic beam parameters at 10 kV and simple extraction of the mode.

Slides WEA04 [2.344 MB]

THB03

Femtosecond-Stability Delivery of Synchronized RF-Signals to the Klystron Gallery over 1-km Optical Fibers

laser, timing, klystron, detector

663

J. Kim, K. Jung, J. Lim, J. Shin, H. Yang
KAIST, Daejeon, Republic of Korea
H.-S. Kang, C.-K. Min
PAL, Pohang, Kyungbuk, Republic of Korea

Funding: This work was supported by the PAL-XFEL Project and the National Research Foundation (Grant number 2012R1A2A2A01005544) of South Korea.
We present our recent progress in optical frequency comb-based remote optical and RF distribution system at PAL-XFEL. A 238 MHz mode-locked Er-laser is used as an optical master oscillator (OMO), which is stabilized to a 2.856 GHz RF master oscillator (RMO) using a fiber- loop optical-microwave phase detector (FLOM-PD). We partly installed a pair of 1.15 km long fiber links through a cable duct to connect and OMO room to a klystron gallery in the PAL-XFEL Injector Test Facility (ITF). The fiber links are stabilized using balanced optical cross- correlators (BOC). A voltage controlled RF oscillator (VCO) is locked to the delivered optical pulse train using the second FLOM-PD. Residual timing jitter and drift between the two independently distributed optical pulse train and RF signal is measured at the klystron gallery. The results are 6.6 fs rms and 31 fs rms over 7 hours and 62 hours, respectively. This is the first comb-based optical/RF distribution and phase comparison in the klystron gallery environment.

Slides THB03 [7.478 MB]

THP034

Further Analysis of Corrugated Plate Dechirper Experiment at BNL-ATF

wakefield, simulation, electron, free-electron-laser

788

M.A. Harrison, G. Andonian, P. Frigola, A.Y. Murokh, M. Ruelas, A.V. Smirnov
RadiaBeam Systems, Santa Monica, California, USA
M.G. Fedurin
BNL, Upton, Long Island, New York, USA

Funding: This work is supported by Department of Energy grant number DE-SC0009550.
RadiaBeam Systems successfully completed testing of a proof-of-concept corrugated plate dechirper at the Brookhaven National Laboratory Accelerator Test Facility.* Such passive devices should prove indispensable for the efficient operation of future XFEL facilities. These experiments demonstrated a narrowing of the energy spectrum in chirped beam bunches at 57.6 MeV. In this paper, we compare these results with results from Elegant simulations of the BNL-ATF beam. We also compare GdfidL simulations of the wakefield with the analytic results of Bane and Stupakov.**
* Harrison, M., et al "Removal of Residual Chirp in Compressed Beams Using a Passive Wakefield Technique." NaPAC13, 2013
** K. Bane, et al "Corrugated Pipe as a Beam Dechirper," SLAC-PUB-14925, 2012

THP048

Formation of the Electron Bunch Longitudinal Profile for Coherent Electron Cooling Experiment

electron, cavity, gun, laser

840

I. Pinayev, D. Kayran, V. Litvinenko
BNL, Upton, Long Island, New York, USA

Proof-of-princilpe experiment of the coherent electron cooling is ongoing at Brookhaven National Lab. CeC mechanism utilizes amplification of density modulation, induced by hadrons, by an FEL structure. To fully utilize electron beam cooling capacity we need uniform longitudinal beam profile. In this paper we present two frequency injector system tuned for this requirement.

THP053

Steady State Multipacting in a Micro-pulse Electron Gun

electron, cavity, cathode, gun

851

K. Zhou, X.Y. Lu, X. Luo, S.W. Quan, Z.Q. Yang, J. Zhao
PKU, Beijing, People's Republic of China

Multipacting is a resonant electron discharge phenomenon via secondary electron emission, while micro-pulse electron gun (MPG) utilizes the multipacting current in a radio-frequency (RF) cavity to produce short pulse electron beams. The concept of MPG has been proposed for many years. However, the unstable operating state of MPG vastly obstructs its practical applications. This paper presents a study on the steady state mulitpacting in a MPG. The requirements for steady state multipacting are proposed through the analysis of the interaction between the RF cavity and the beam load. Accordingly, a MPG cavity with the frequency of 2856 MHz has been designed and constructed. Various kinds of grid-anodes are tested in our primary experiments. Both the unstable and stable multipacting current have been observed. Presently, the stable output beam current has been detected at about 12.2 mA. Further experimental study is under way now.

Poster THP053 [2.525 MB]

THP069

Performance Study of High Bandwidth Pickups Installed at FLASH and ELBE for Femtosecond-Precision Arrival Time Monitors

pick-up, laser, electron, operation

893

M.K. Czwalinna, C. Gerth, H. Schlarb, C. Sydlo
DESY, Hamburg, Germany
A. Angelovski, R. Jakoby, A. Penirschke
TU Darmstadt, Darmstadt, Germany
M. Gensch, M. Kuntzsch
HZDR, Dresden, Germany
M. Kuntzsch
TU Dresden, Dresden, Germany
T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany

At today's free-electron lasers, high-resolution electron bunch arrival time measurements have become increasingly more important in fast feedback systems for a timing jitter reduction down to the femtosecond level as well as for time-resolved pump-probe experiments. This is fulfilled by arrival time monitors which employ an electro-optical detection scheme by means of synchronised ultrashort laser pulses. Even more, at FLASH and the European XFEL the measurement has to cover a wide range of bunch charges from 1 nC down to 20 pC with equally sub-10 fs resolution. To meet these requirements, recently a high bandwidth pickup electrode with a cut-off frequency above 40 GHz has been developed. These pickups are installed at the macro-pulsed SRF accelerator of the free-electron laser FLASH and at the macro-pulsed continuous wave SRF accelerator ELBE. In this paper we present an evaluation of the pickup performance by direct signal measurements with high bandwidth oscilloscopes and by use of the electro-optical arrival time monitor.

THP074

Infrared Diagnostics Instrumentation Design for the Coherent Electron Cooling Proof of Principle Experiment

wiggler, electron, FEL, ion

905

T.A. Miller, D.M. Gassner, V. Litvinenko, M.G. Minty, I. Pinayev, B. Sheehy
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy
The Coherent Electron Cooling Proof-of-Principle experiment [*] based on an FEL is currently under construction in the RHIC tunnel at BNL. Diagnostics for the experimental machine [**] are currently being designed, built and installed. This paper focuses on the design of the infrared diagnostic instrumentation downstream of the three tandem 2.8m long helical wiggler sections that will act on a 22MeV 68uA electron beam co-propagating with the 40GeV/u RHIC gold beam. The 14 um FEL radiation, or wiggler light, will be extracted from RHIC via a viewport in a downstream DX magnet cryostat and analysed by instrumentation on a nearby optics bench. Instruments concentrating on three parameters, namely intensity, spectral content, and transverse profile, will extract information from the wiggler light in an attempt to quantify the overlap of the electron and ion beams and act as an indicator of coherent cooling.
* V. Litvinkenko, et al THOBN3, PAC2011, New York, NY
** D. M. Gassner, et al WEAP01, BIW2012, Newport News, VA

THP076

Measurements of the Timing Stability at the FLASH1 Seeding Experiment

laser, electron, timing, FEL

913

C. Lechner, A. Azima, M. Drescher, L.L. Lazzarino, Th. Maltezopoulos, V. Miltchev, T. Plath, J. Rönsch-Schulenburg, J. Roßbach, M. Wieland
Uni HH, Hamburg, Germany
S. Ackermann, J. Bödewadt, H. Dachraoui, N. Ekanayake, B. Faatz, M. Felber, K. Honkavaara, T. Laarmann, J.M. Mueller, H. Schlarb, S. Schreiber, S. Schulz
DESY, Hamburg, Germany
G. Angelova Hamberg
Uppsala University, Uppsala, Sweden
K.E. Hacker, S. Khan, R. Molo
DELTA, Dortmund, Germany
P.M. Salen, P. van der Meulen
FYSIKUM, AlbaNova, Stockholm University, Stockholm, Sweden

Funding: Supported by Federal Ministry of Education and Research of Germany under contract No. 05K10PE1, 05K10PE3, 05K13GU4 and 05K13PE3 and the German Research Foundation programme graduate school 1355.
For seeding of a free-electron laser, the spatial and temporal overlap of the seed laser pulse and the electron bunch in the modulator is critical. To establish the temporal overlap, the time difference between pulses from the seed laser and spontaneous undulator radiation is reduced to a few pico-seconds with a combination of a photomultiplier tube and a streak camera. Finally, for the precise overlap the impact of the seed laser pulses on the electron bunches is observed. In this contribution, we describe the current experimental setup, discuss the techniques applied to establish the temporal overlap and analyze its stability.

THP084

Longitudinal Diagnostics of RF Electron Gun using a 2-cell RF Deflector

electron, gun, cavity, laser

929

M. Nishiyama, K. Sakaue, T. Takahashi, T. Toida, M. Washio
Waseda University, Tokyo, Japan
T. Takatomi, J. Urakawa
KEK, Ibaraki, Japan

Funding: This work was supported by JSPS Grant-in-Aid for Scientific Research (A) 10001690 and the Quantum Beam Technology Program of MEXT.
We have been studying a compact electron accelerator based on an S-band Cs-Te photocathode rf electron gun at Waseda University. We are using this high quality electron bunch for many application researches. It is necessary to measure the bunch length and temporal distribution for evaluating application researches and for improving an rf gun itself. Thus we adopted the rf deflector system. It kicks the electron bunch with resonated rf electromagnetic field. Using this technique, the longitudinal distribution is mapped into the transverse space. The rf deflector has a 2-cell standing wave π-mode structure, operating in TM120 dipole mode at 2856 MHz. It provides a maximum vertical kick of 1.00MV with 750 kW input rf-power which is equivalent to the temporal resolution of around 58 femtoseconds bunch length. In this conference, we report the details of our rf deflector, the latest progress of longitudinal phase space diagnostics and future prospective.

THP095

Evolvement of the Laser and Synchronization System for the Shanghai DUV-FEL Test Facility

laser, electron, FEL, free-electron-laser

960

B. Liu, L. Feng, T. Lan, X.Q. Liu, D. Wang, X.T. Wang, W.Y. Zhang, S.P. Zhong
SINAP, Shanghai, People's Republic of China

Funding: supported by the National Natural Science Foundation of China (Grant No. 11175241)
Many attractive experiments including HGHG, EEHG, cascaded HGHG, chirped pulse amplification etc. are carried out or planned on the Shanghai Deep Ultra-Violet Free Electron Laser test facility. These experiments are all utilizing a laser as seed, and need precise synchronization between the electron beam and the laser pulse. We will describe the history and current status of the seeding and synchronization scheme for the SDUV-FEL together with some related experiment results in this paper.

FRA02

Wave-Mixing Experiments with Multi-colour Seeded FEL Pulses

FEL, laser, polarization, photon

985

F. Bencivenga, A. Battistoni, F. Capotondi, R. Cucini, M.B. Danailov, G. De Ninno, M. Kiskinova, C. Masciovecchio
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

The extension of wave-mixing experiments in the extreme ultraviolet (EUV) and x-ray spectral range represents one of the major breakthroughs for ultrafast x-ray science. Essential prerequisites to develop such kind of non-linear coherent methods are the strength of the input fields, comparable with the atomic field one, as well as the high temporal coherence and stability of the photon source(s). These characteristics are easily achievable by optical lasers. Seeded free-electron-lasers (FELs) are similar in many respects to conventional lasers, hence calling for the development of wave-mixing methods. At the FERMI seeded FEL facility this ambitious task is tackled by the TIMER project, which includes the realization of a dedicated experimental end-station. The wave-mixing approach will be initially used to study collective atomic dynamics in disordered systems and nanostructures, through transient grating (TG) experiments. However, the wavelength and polarization tunability of FERMI, as well as the possibility to radiate multi-colour seeded FEL pulses, would allow to expand the range of possible scientific applications.

Slides FRA02 [7.731 MB]