FEL2013 - List of Keywords (electron)

Paper	Title	Other Keywords	Page
MOOBNO01	First Lasing of FERMI FEL-2	FEL, laser, injection, free-electron-laser	1
	L. Giannessi, E. Allaria, D. Castronovo, P. Cinquegrana, G. D'Auria, M. Dal Forno, M.B. Danailov, G. De Ninno, A.A. Demidovich, S. Di Mitri, B. Diviacco, W.M. Fawley, M. Ferianis, E. Ferrari, L. Fröhlich, G. Gaio, R. Ivanov, B. Mahieu, N. Mahne, I. Nikolov, F. Parmigiani, G. Penco, L. Raimondi, C. Serpico, P. Sigalotti, C. Spezzani, M. Svandrlik, C. Svetina, M. Trovò, M. Veronese, D. Zangrando, M. Zangrando Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy M. Dal Forno DEEI, Trieste, Italy G. De Ninno, D. Gauthier University of Nova Gorica, Nova Gorica, Slovenia E. Ferrari, F. Parmigiani Università degli Studi di Trieste, Trieste, Italy L. Giannessi ENEA C.R. Frascati, Frascati (Roma), Italy B. Mahieu CEA/DSM/DRECAM/SPAM, Gif-sur-Yvette, France M. Zangrando IOM-CNR, Trieste, Italy
	During the month of October 2012 the commissioning of the light source FEL-2 at FERMI was successfully concluded. Fermi FEL-2 is the first seeded FEL operating with a double stage cascade in the "fresh bunch injection" mode. The two stages are two high gain harmonic generation FELs where the first stage is seeded by the 3rd harmonic of a Ti:Sa laser system, which is up converted to the 4th-6th harmonic. The output of the first stage is then used to seed the second stage. A final wavelengths of 10.8 nm was obtained as the 24th harmonic of the seed wavelength at the end of the two frequency conversion processes, demonstrating that the FEL is capable of producing single mode narrow bandwidth pulses with an energy of several tens of microjoules. I. Ben-Zvi, K. M. Yang, L. H. Yu, ”The ”fresh-bunch” technique in FELs”, NIM A 318 (1992), p 726-729
	Slides MOOBNO01 [25.265 MB]

MOICNO01	Generation of a Train of Short Pulses by Means of FEL Emission of a Combed Electron Beam	FEL, radiation, undulator, laser	2
	V. Petrillo Universita' degli Studi di Milano, Milano, Italy M.P. Anania, M. Bellaveglia, E. Chiadroni, D. Di Giovenale, G. Di Pirro, M. Ferrario, G. Gatti, R. Pompili, C. Vaccarezza, F. Villa INFN/LNF, Frascati (Roma), Italy M. Artioli ENEA-Bologna, Bologna, Italy A. Bacci, A.R. Rossi Istituto Nazionale di Fisica Nucleare, Milano, Italy A. Cianchi Università di Roma II Tor Vergata, Roma, Italy F. Ciocci, G. Dattoli, L. Giannessi, A. Petralia, M. Quattromini, C. Ronsivalle, E. Sabia ENEA C.R. Frascati, Frascati (Roma), Italy A. Mostacci Rome University La Sapienza, Roma, Italy P. Musumeci UCLA, Los Angeles, California, USA J.V. Rau ISM-CNR, Rome, Italy
	We present a direct and powerful method for generating train of radiation pulses based on the FEL radiation from a multi-peaked electron beam produced with a combed laser pulse accelerated and compressed in a linac by the velocity bunching technique. The electron beam, constituted by two bunches, can be extracted from the accelerating section when they are temporaly superimposed but separated in energy, so that each of them is characterized by a different value of the Lorentz factor. When driven in the FEL undulator, they emit two separate spectral lines, according to the FEL resonance condition, that interfere producing fringes in the time-domain. In this way a train of regular pulses can be obtained, without limitation in frequency, and with the perspective of reaching the attosecond domain in the X ray regime.
	Slides MOICNO01 [8.836 MB]

MOOCNO01	Emittance Control in the Presence of Collective Effects in the FERMI@Elettra Free Electron Laser Linac Driver	emittance, FEL, linac, brightness	6
	S. Di Mitri, E. Allaria, D. Castronovo, M. Cornacchia, P. Craievich, M. Dal Forno, G. De Ninno, W.M. Fawley, E. Ferrari, L. Fröhlich, L. Giannessi, E. Karantzoulis, A.A. Lutman, G. Penco, C. Serpico, S. Spampinati, C. Spezzani, M. Trovò, M. Veronese Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy P. Craievich PSI, Villigen PSI, Switzerland M. Dal Forno University of Trieste, Trieste, Italy G. De Ninno, S. Spampinati University of Nova Gorica, Nova Gorica, Slovenia E. Ferrari Università degli Studi di Trieste, Trieste, Italy L. Giannessi ENEA C.R. Frascati, Frascati (Roma), Italy A.A. Lutman SLAC, Menlo Park, California, USA
	Recent beam transport experiments conducted on the the linac driving the FERMI@Elettra free electron laser have provided new insights concerning the transverse emittance degradation due to both coherent synchrotron radiation (CSR) and geometric transverse wakefield (GTW), together with methods to counteract such degradation. For beam charges of several 100's of pC, optics control in a magnetic compressor results to minimize the CSR once the H-function is considered. We successfully extended this approach to the case of a modified double bend achromat system, opening the door to relatively large bending angles and compact transfer lines. At the same time, the GTWs excited in few mm diameter iris collimators** and accelerating structures have been characterized in terms of the induced emittance growth. A model integrating both CSR and GTW effects suggests that there is a limit on the maximum obtainable electron beam brightness in the presence of such collective effects. * S. Di Mitri et al., PRST-AB 15, 020701 (2012) S. Di Mitri et al., PRL 110, 014801 (2013) * S. Di Mitri et al., PRST-AB 15, 061001 (2012)
	Slides MOOCNO01 [6.919 MB]

MOOCNO04	Using a Lienard-Wiechert Solver to Study Coherent Synchrotron Radiation Effects	radiation, simulation, undulator, dipole	17
	R.D. Ryne LBNL, Berkeley, California, USA B.E. Carlsten, N.A. Yampolsky LANL, Los Alamos, New Mexico, USA
	We report on coherent synchrotron radiation (CSR) modeling using a new first-principles Lienard-Wiechert solver (CSR3D) that simulates real-world number of particles (624 million to 6.24 billion for 100-pC to 1-nC bunch charges). Using this tool, we have verified the limits of applicability of the common 1-D CSR model, including effect due to transverse beam size and shape. We also have observed energy dependent, wavelength dependent, and transverse-size dependent effects on CSR enhancement from microbunching. Additionally, we describe statistics of CSR shot noise, including dependencies on beam energy and transverse position and resulting energy diffusion. We consider the full transverse equation of motion and also quantify the effect of emittance growth from the bunch’s transverse radiation force.
	Slides MOOCNO04 [6.258 MB]

MOPSO02	Measurement of Electron-Beam and Seed Laser Properties Using an Energy Chirped Electron Beam	laser, FEL, simulation, linac	24
	E. Allaria, G. De Ninno, S. Di Mitri, W.M. Fawley, E. Ferrari, L. Fröhlich, G. Penco, P. Sigalotti, S. Spampinati, C. Spezzani, M. Trovò Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy G. De Ninno, S. Spampinati University of Nova Gorica, Nova Gorica, Slovenia E. Ferrari Università degli Studi di Trieste, Trieste, Italy
	We present a new method that uses CCD images of the FERMI electron beam at the dump spectrometer after the undulator to determine various electron beam and external seed laser properties. By taking advantage of the correlation between time and electron beam energy for a quasi-linearly chirped electron beam and the fact that the FERMI seed laser pulse (~180 fs) is much shorter than the electron beam duration (~1 ps), measurements of the e-beam pulse length and temporally local energy chirp and current are possible. Moreover, the scheme allows accurate determination of the timing jitter between the electron beam and the seed laser, as well as a measure of the latter's effective pulse length in the FEL undulators. The scheme can be also provide an independent measure of the energy transferred from the electron beam to the FEL output radiation. We describe the proposed method as well as some experimental results obtained at the seeded FERMI FEL.

MOPSO04	Theoretical Analysis of a Laser Undulator-Based High Gain FEL	laser, FEL, undulator, radiation	27
	P. Baxevanis, R.D. Ruth SLAC, Menlo Park, California, USA
	The use of laser (or RF) undulators is nowadays considered attractive for FEL applications, particularly those that aim to utilize relatively low-energy electron beams. In the context of the standard theoretical analysis, the counter-propagating laser pulse is usually treated in the plane-wave approximation, neglecting amplitude and phase variation. In this paper, we develop a three-dimensional, analytical theory of a high-gain FEL based on a laser or RF undulator, taking into account the longitudinal variation of the undulator field amplitude, the laser Gouy phase and the effects of emittance and energy spread in the electron beam. Working in the framework of the Vlasov-Maxwell formalism, we derive a self-consistent equation for the radiation amplitude in the linear regime, which is then solved to good approximation by means of an orthogonal expansion technique []. Numerical results obtained from our analysis are used in the study of an example of a compact, laser undulator-based, X-ray FEL. P. Baxevanis, R. Ruth, Z. Huang, Phys. Rev. ST-AB 16, 010705 (2013).

MOPSO07	Channeling Radiation With Low-Energy Electron Beams: Experimental Plans and Status at Fermilab	radiation, emittance, brilliance, laser	38
	B.R. Blomberg, D. Mihalcea, H. Panuganti, P. Piot Northern Illinois University, DeKalb, Illinois, USA C.A. Brau, B.K. Choi, B.L. Ivanov, M.H. Mendenhall Vanderbilt University, Nashville, TN, USA W.E. Gabella Vanderbilt University, W.M. Keck Foundation Free-Electron Laser Center, Nashville, USA W.S. Wagner Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Radiation Physics, Dresden, Germany
	Funding: This work was supported by the DARPA Axis program under contract AXIS N66001-11-1-4196 with Vanderbilt University and Northern Illinois University. Channeling radiation is an appealing radiation process to produce x-ray radiation with low-energy electron beams. In this contribution we describe the anticipated performance and preliminary results from a channeling radiation experiment to produce ~ 1.2-keV radiation from a ~ 4-MeV electron beam at Fermilab's high-brightness electron source lab(HBESL). We also discuss plans to produce X-ray radiation ([10,80]-keV photon energy) at Fermilab's advanced superconducting test accelerator (ASTA).

MOPSO08	Unaveraged Modelling of a LWFA Driven FEL	FEL, simulation, radiation, undulator	43
	L.T. Campbell, B.W.J. MᶜNeil USTRAT/SUPA, Glasgow, United Kingdom F.J. Grüner, A.R. Maier CFEL, Hamburg, Germany F.J. Grüner, A.R. Maier Uni HH, Hamburg, Germany F.J. Grüner LMU, Garching, Germany
	Preliminary simulations of a Laser Wakefield Field Accelerator driven FEL are presented using the 3D unaveraged, broad bandwidth FEL simulation code Puffin. The radius of the matched low emittance electron beam suggests that the FEL interaction will be strongly affected by radiation diffraction. The parameter scaling and comparison between 3D and equivalent 1D simulations appears to confirm the interaction is diffraction dominated. Nevertheless, output powers are predicted to be greater than those of similar unaveraged FEL models. Possible reasons for the discrepancies between the averaged and unaveraged simulation results are discussed. [1] - AR Maier, A Meseck, S Reiche, CB Schroeder, T Seggebrock, and F Gruner, Phys Rev X 2, 031019 (2012)

MOPSO09	Investigation of a 2-Colour Undulator FEL Using Puffin	undulator, FEL, radiation, bunching	47
	L.T. Campbell, B.W.J. MᶜNeil USTRAT/SUPA, Glasgow, United Kingdom S. Reiche PSI, Villigen PSI, Switzerland
	The unaveraged FEL code Puffin* is used to investigate a 2 color FEL. In the scheme under investigation, undulator modules are tuned alternately to generate 2 frequencies quasi-simultaneously, which should result in greater stability than generating them consecutively. The advantage of using Puffin is that it provides the capability of modelling a broad bandwidth spectrum. For example, radiation at 1nm and 2.4nm is difficult to model simultaneously in standard averaged FEL codes. An unaveraged code like Puffin is able to model 2 (or more) wavelengths with a much wider spacing. * LT Campbell and BWJ McNeil, Phys. Plasmas 19, 093119 (2012)

MOPSO17	The Present Status of the Theory of the FEL-based Hadron Beam Cooling	FEL, hadron, kicker, ion	52
	A. Elizarov, V. Litvinenko 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 (CeC)* device is one of the new facilities under construction in BNL. The CeC is a realization of the stochastic cooling with an electron beam serving as a pick-up and kicker. Hadrons generate electron density perturbations in the modulator section, then these perturbations are amplified in an FEL, and then, they accelerate (or decelerate) hadrons in the kicker by electric field with respect to their velocities. Here we present the theoretical description of the modulator sector,, where the electron density perturbations are formed and our new results on the time evolution of these perturbations in the FEL section, where they are amplified. V. N. Litvinenko, Y. S. Derbenev, Phys. Rev. Lett. 102, 114801 (2009). A. Elizarov, V. Litvinenko, G. Wang, IPAC'12, weppr099 (2012). * A. Elizarov, V. Litvinenko, IPAC'13, mopwo088 (2013).

MOPSO30	Simple Setups for Carrier-envelope-phase Stable Single-cycle Attosecond Pulse Generation	undulator, laser, radiation, FEL	63
	J. Hebling, G. Almási, J.A. Fülöp, M.I. Mechler, Z. Tibai, Gy. Tóth University of Pecs, Pécs, Hungary
	Funding: Work supported by Hungarian Research Fund (OTKA), grant number 101846, and from SROP-4.2.1.B-10/2/KONV-2010-0002 and SROP-4.2.2/B-10/1-2010-0029 Robust methods for producing waveform-controlled half-cycle–few-cycle pulses in the mid-infrared (MIR)–extreme ultraviolet (EUV) spectral range are proposed. They are based on coherent Thomson scattering of THz pulses on relativistic ultrathin electron layers and coherent undulator radiation of relativistic ultrathin electron layers, respectively. The ultrathin electron layers are produced by microbunching of ultrashort electron bunches by a TW power laser in a modulator undulator. According to our numerical calculations it is possible to generate as short as 10 nm long electron layers if a single-period modulator undulator with period length significantly shorter than the resonant one is used and the undulator parameter is only K=0.25. Thomson scattering of THz pulses on ultrathin electron layers with only 50 MeV energy can generate for example 170 as long single-cycle pulses at 80 nm wavelength with 0.1 nJ energy. Coherent undulator radiation of ultrathin electron layers with 450 MeV energy can generate single-cycle radiation in the 20 nm – 1000 nm wavelength range. The corresponding pulse energy and pulse duration vary in the 10 pJ – 2 nJ and 47 as – 2.1 fs ranges, respectively.

MOPSO31	Quasiperiodic Method of Averaging Applied to Planar Undulator Motion Excited by a Fixed Traveling Wave	resonance, undulator, FEL, radiation	762
	K.A. Heinemann, J.A. Ellison UNM, Albuquerque, New Mexico, USA M. Vogt DESY, Hamburg, Germany
	Funding: The work of JAE and KH was supported by DOE under DE-FG-99ER41104. The work of MV was supported by DESY. We present a mathematical analysis of planar motion of energetic electrons moving through a planar dipole undulator, excited by a fixed planar polarized plane wave Maxwell field in the X-Ray FEL regime.* We study the associated 6D Lorentz system as the wavelength of the traveling wave varies. The 6D system is reduced, without approximation, to a 2D system (for a scaled energy deviation and generalized ponderomotive phase) in a form for a rigorous asymptotic analysis using the Method of Averaging (MoA), a long time perturbation theory. As the wavelength varies the system passes through resonant and nonresonant (NR) zones and we develop NR and near-to-resonant (NtoR) normal form approximations. For a special initial condition, on resonance, we obtain the well-known FEL pendulum system. We prove NR and NtoR first-order averaging theorems, in a novel way, which give optimal error bounds for the approximations. The NR case is an example of quasiperiodic averaging where the small divisor problem enters in the simplest possible way. To our knowledge the analysis has not been done with the generality here nor has the standard FEL pendulum system been derived with error bounds. * J.A. Ellison, K. Heinemann, M. Vogt, M. Gooden: arXiv:1303.5797 [physics.acc-ph]

MOPSO34	Highly Efficient, High-energy THz Pulses from Cryo-cooled Lithium Niobate for Accelerator and FEL Applications	laser, acceleration, cryogenics, FEL	68
	K.-H. Hong, E. Granados, S.-W. Huang, W.R. Huang, F.X. Kaertner, R. Koustuban, L.E. Zapata MIT, Cambridge, Massachusetts, USA F.X. Kaertner CFEL, Hamburg, Germany
	Funding: This work was supported by DARPA under contract N66001-1-11-4192. Intense, ultrafast THz fields are of great interest for electron acceleration, beam manipulation and measurement, and pump-probe experiments with coherent soft/hard x-ray sources based on FELs or inverse Compton scattering sources. Acceleration at THz frequencies has an advantage over RF in terms of accessing high electric-field gradients (>100 MV/cm), while the beam delivery can be treated quasi-optically. However, high-field THz pulse generation is still demanding when compared with conventional RF generation. In this paper, we present highly efficient, single-cycle, 0.45 THz pulse generation by optical rectification of 1.03 μm pulses in cryogenically cooled lithium niobate (LN). Using a near-optimal duration of 680 fs and a pump energy of 1.2 mJ, we report conversion efficiencies above 3% [1], >10 times higher than previous report (0.24%) [2]. Cryogenic cooling of lithium niobate significantly reduces the THz absorption, which will enable the scaling of THz pulse energies to the mJ. We will also report on polarization and mode conversion using segmented THz waveplates to generate radially-polarized TEM01 modes, suitable for THz electron acceleration in dielectric waveguide. [1] S.-W. Huang et al., Opt. Lett. 38, 796-798 (2013). [2] J. A. Fülöp et al., Opt. Lett. 37, 557-559 (2012).

MOPSO43	High Power Laser Transport System for Laser Cooling to Counteract Back-Bombardment Heating in Microwave Thermionic Electron Guns	laser, vacuum, gun, coupling	75
	J.M.D. Kowalczyk, M.R. Hadmack, J. Madey, E.B. Szarmes, M.H.E.H. Vinci University of Hawaii, Honolulu, HI, USA
	Funding: This work was funded by the Department of Homeland Security through grant #2011-DN-077-ARI055-03. Heat from a high power, short pulse laser deposited on the surface of a thermionic electron gun cathode will diffuse into the bulk producing a surface cooling effect that counteracts the electron back-bombardment (BB) heating intrinsic to the gun. The resulting constant temperature stabilizes the current allowing extension of the gun’s peak current and duty cycle. To enable this laser cooling, high power laser pulses must be transported to the high radiation zone of the electron gun, and their transverse profile must be converted from Gaussian to top-hat to uniformly cool the cathode. A fiber optic transport system is simple, inexpensive, and will convert a Gaussian to a top-hat profile. Coupling into the fiber efficiently and without damage is difficult as tight focusing is required at the input and, if coupled in air, the high fluence will breakdown the air resulting in lost energy. We have devised a vacuum fiber coupler (VFC) that allows the focus to occur in vacuum, avoiding the breakdown of air, and have successfully transported 10 ns long, 85 mJ pulses from a 1064 nm Nd:YAG laser through 20 m of 1 mm diameter fiber enabling testing of the laser cooling concept.

MOPSO44	Laser Cooling to Counteract Back-Bombardment Heating in Microwave Thermionic Electron Guns	laser, cathode, gun, simulation	79
	J.M.D. Kowalczyk, M.R. Hadmack, J. Madey University of Hawaii, Honolulu, HI, USA
	Funding: This work was funded by the Department of Homeland Security through grant #2011-DN-077-ARI055-03. A theoretical study of the use of laser cooling to counteract electron back-bombardment heating (BB) in thermionic electron guns is presented. Electron beams with short bunches, minimum energy spread, and maximum length pulse trains are required for many applications, including the inverse-Compton X-ray source being developed at UH. Currently, these three electron beam parameters are limited by BB which causes the cathode temperature and emission current to increase leading to beam loading. Beam loading elongates the bunches by shifting the electrons’ relative phases, introduces energy spread by reducing the energy of electrons emitted later in the macropulse, and forces the use of shorter macropulses to minimize energy spread. Irradiation of the electron gun cathode with a short laser pulse prior to beam acceleration allows the laser heat to diffuse into the cathode bulk effectively cooling the surface and counteracting the BB. Calculation of the the cooling produced by laser pulses of various duration and energy is presented.

MOPSO49	Numerical Accuracy When Solving the FEL Equations	FEL, simulation, undulator, bunching	82
	R.R. Lindberg ANL, Argonne, USA
	Funding: U.S. Dept. of Energy Office of Sciences under Contract No. DE-AC02-06CH11357 The usual method of numerically solving the FEL equations involves dividing both the e-beam and radiation field into "slices" that are loaded one at a time into memory. This scheme is only first order accurate in the discretization of the ponderomotive phase because having only one slice in memory effectively results in a first order interpolation of the field-particle coupling. While experience has shown that FEL simulations work quite well, the first order accuracy opens the door to two possible ways of speeding up simulation time. First, one can consider higher order algorithms; unfortunately, these methods appear to require all the particle and field data in memory at the same time, and therefore will typically only be important for either small (probably 1D) problems or for parallel simulations run on many processors. Second, one may consistently solving the equations to some low order using faster, simpler algorithms (replacing, for example, the usual RK4). The latter is particularly attractive, although in practice it may be desirable to retain higher order methods when integrating along z. We investigate some of the possibilities.

MOPSO51	Feasibility of an XUV FEL Oscillator at ASTA	FEL, undulator, simulation, cryomodule	88
	A.H. Lumpkin Fermilab, Batavia, USA H. Freund LANL, Los Alamos, New Mexico, USA M.W. Reinsch LBNL, Berkeley, California, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. A significant opportunity exists at the Advanced Superconducting Test Accelerator (ASTA) facility presently under construction at Fermilab to enable the first XUV free electron laser (FEL) oscillator experiments. The ultrabright beam from the L-band photoinjector will provide sufficient gain to compensate for reduced mirror reflectances in the VUV-XUV regimes, the 3-MHz micropulse repetition rate for 1 ms will support an oscillator configuration, the SCRF linac will provide stable energy, and the eventual GeV-scale energy with three TESLA-type cryomodules will satisfy the FEL resonance condition in the XUV regime. Concepts based on combining such beams with a 5-cm-period undulator and optical resonator cavity for an FEL oscillator are described. We used the 68% reflectances for normal incidence on multilayer metal mirrors developed at LBNL. Initial simulations using GINGER with an oscillator module and MEDUSA:OPC show saturation for the 13.4-nm case after 300 and 350 passes, respectively,of the 3000 pulses. Initially, VUV experiments could begin in the 180- to 120-nm regime using MgF2-coated Al mirrors with only one cryomodule installed and beam energies of 250-300 MeV. LBNL X-ray optics site: http://xdb.lbl.gov/Section4

MOPSO57	Measurement of Wigner Distribution Function for Beam Characterization of FELs	laser, free-electron-laser, FEL, focusing	92
	T. Mey, K. Mann, B. Schäfer LLG, Goettingen, Germany B. Keitel, S. Kreis, M. Kuhlmann, E. Plönjes, K.I. Tiedtke DESY, Hamburg, Germany
	Free-electron lasers deliver VUV and soft x-ray pulses with the highest brilliance available and high spatial coherence. Users of such facilities have high demands on phase and coherence properties of the beam, for instance when working with coherent diffractive imaging (CDI). To gain highly resolved spatial coherence information, we have performed a caustic scan at BL2 of FLASH using the ellipsoidal beam line focusing mirror and a movable XUV sensitive CCD detector. This measurement allows for retrieving the Wigner distribution function, being the two-dimensional Fourier transform of the mutual intensity of the beam. Computing the reconstruction on a four-dimensional grid, this yields the Wigner distribution which describes the beam propagation completely. Hence, we are able to provide comprehensive information about spatial coherence properties of the FLASH beam including the mutual coherence function and the global degree of coherence. Additionally, we derive the beam propagation parameters such as Rayleigh length, waist diameter and the beam quality factor M².

MOPSO59	The Influence of the Magnetic Field Inhomogeneity on the Spontaneous Radiation and the Gain in the Plane Wiggler	wiggler, laser, undulator, FEL	97
	K.B. Oganesyan ANSL, Yerevan, Armenia
	Funding: ISTC We calculate the spectral distribution of spontaneous emission and the gain of electrons moving in plane wiggler with inhomogeneous magnetic field. We show that electrons do complicated motion consisting of slow(strophotron) and fast(undulator) parts. We average the equations of motion over fast undulator part and obtain equations for connected motion. It is shown, that the account of inhomogenity of the magnetic field leads to appearence of additional peaks in the spectral distribution of spontaneous radiation and the gain.

MOPSO60	Channeled Positrons as a Source of Gamma Radiation	positron, photon, radiation, ion	101
	K.B. Oganesyan ANSL, Yerevan, Armenia
	Funding: ISTC A possibility of channeling of low-energy (5 / 20Mev) relativistic positrons with coaxial symmetry around separate crystal axes of negative ions in some types of crystals, is shown. The annihilation processes of positrons with medium electrons are investigated in details. The lifetime of a positron in the regime of channeling is estimated 〖10〗^-6 sec which on a 〖10〗⁹/〖10〗⁸ times is bigger than at usual cases.

MOPSO61	Modulated Medium for Generation of Transition Radiation	radiation, dipole, lattice, polarization	105
	K.B. Oganesyan ANSL, Yerevan, Armenia
	Funding: ISTC It is shown on an example of amorphous quartz, under the influence of a standing microwave field, at its certain parameters, superlattice is created in the medium where difference in values of dielectric constants of neighboring layers can be up to third order. This superlattice exists during the nanosecond, however it is sufficient for using it as a radiator for generation of transition radiation by relativistic electrons.

MOPSO65	Suppression of Wakefield Induced Energy Spread Inside an Undulator Through Current Shaping	wakefield, undulator, impedance, FEL	108
	J. Qiang, C.E. Mitchell LBNL, Berkeley, California, USA
	Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Wakefields from resistive wall and surface roughness inside an undulatory can cause significant growth of beam energy spread and limit the performance of x-ray FEL radiation. In this paper, we propose a method to mitigate such energy modulation by appropriately conditioning the electron beam current profile. Numerical example and potential applications will also be discussed.

MOPSO66	Start-to-end Simulation of a Next Generation Light Source Using the Real Number of Electrons	simulation, FEL, emittance, radiation	112
	J. Qiang, J.N. Corlett, P. Emma, C.E. Mitchell, C. F. Papadopoulos, G. Penn, M.W. Reinsch, R.D. Ryne, M. Venturini LBNL, Berkeley, California, USA S. Reiche PSI, Villigen PSI, Switzerland
	Funding: This research was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Start-to-end simulation plays an important role in design and optimization of next generation light sources. In this paper, we will present start-to-end (from the photocathode to the end of undulator) simulations of a high repetition rate FEL-based Next Generation Light Source driven by CW superconducting linac with the real number of electrons (~2 billion electrons/bunch) using the multi-physics parallel beam dynamics code IMPACT. We will discuss challenges, numerical methods and physical models used in the simulation. We will also present simulation results of a beam transporting through photoinjector, beam delivery system, and final X-ray FEL radiation.

MOPSO69	Free-Electron Lasers Driven by Laser-Plasma Accelerators Using Decompression or Dispersion	FEL, undulator, plasma, laser	117
	C.B. Schroeder, E. Esarey, W. Leemans, J. van Tilborg LBNL, Berkeley, California, USA Y. Ding, Z. Huang SLAC, Menlo Park, California, USA F.J. Grüner, A.R. Maier CFEL, Hamburg, Germany
	Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Laser-plasma accelerators (LPAs) compactly produce fs beams with kA peak current and low (sub-micron) transverse emittance. Presently, the energy spread (percent-level) hinders the FEL application. Slippage of the fs beam in the FEL also suppresses lasing in the soft-x-ray, and longer, wavelength regimes. Given experimentally demonstrated LPA electron beam parameters, we discuss methods of beam phase space manipulation after the LPA to achieve FEL lasing. Decompression is examined as a solution to reduce the slice energy spread and slippage effects. We present a theoretical analysis of the stretched (and chirped) LPA beam in the FEL and determine the optimal decompression. Dispersion, coupled to a transverse gradient undulator (TGU), is also considered to enable LPA-driven FELs. Using a TGU has the advantages of shorter pulse duration, smaller bandwidth, and wavelength stabilization. We present numerical modeling for SASE and seeded XUV and soft x-ray FELs driven by LPAs after beam manipulation (decompression and/or dispersion). Recent advances in LPA performance will be presented, and experimental plans to demonstrate LPA-driven FEL lasing at LBNL will be discussed.

MOPSO70	Crystal Channeling Acceleration Research for High Energy Linear Collider at ASTA Facility	acceleration, plasma, radiation, laser	122
	Y.-M. Shin Northern Illinois University, DeKalb, Illinois, USA K. Carlson, M.D. Church, V.D. Shiltsev, D.A. Still Fermilab, Batavia, USA J.C. Tobin UMD, College Park, Maryland, USA
	The density of charge carriers in solids is significantly higher than what was considered above in plasma, and correspondingly, the longitudinal fields of up to 10 TV/m are possible. It was suggested that particles are accelerated along major crystallographic directions, which provide a channeling effect in combination with low emittance determined by an Angstrom-scale aperture of the atomic “tubes.” However, the major challenge of this channeling acceleration is that ultimate acceleration gradients might require relativistic intensities at hard x-ray regime (~ 40 keV), exceeding those conceivable for x-rays as of today, though x-ray lasers can efficiently excite solid plasma and accelerate particles inside a crystal channel. However, the acceleration will take place only in a short time before full dissociation of the lattice. Carbon nanotubes have great potential with a wide range of flexibility and superior physical strength, which can be applied to channeling acceleration and possibly fast cooling. This talk will present past and current efforts on crystal acceleration research and discuss feasible experiments with the ASTA and beyond.

MOPSO73	Suface Roughness Wakefield in FEL Undulator	wakefield, impedance, undulator, FEL	127
	G.V. Stupakov SLAC, Menlo Park, California, USA S. Reiche PSI, Villigen PSI, Switzerland
	Among several wakefield models for the FEL undulator vacuum chamber a simple sinusoidal wall modulation with a small ratio of height to wavelength is especially attractive because of its simplicity [1]. The model neglects a so called resonant mode wakefield and has an (integrable) singularity at the origin which makes difficult its use in practical simulations. In this work we generalize the longitudinal wake of a sinusoidally modulated wall to include the effect of the resonant mode. This also removes the singularity of the wake at the origin. The new wake is used to evaluate the roughness wakefield effect in the undulator of SwissFEL. [1] G. Stupakov, in "Nonlinear and Collective Phenomena in Beam Physics 1998" Workshop, New York (1999), no. 468 in AIP Conference Proceedings, pp. 334–47.

MOPSO74	Reevaluation of Coherent Electron Cooling Gain Factor	FEL, undulator, hadron, radiation	132
	G.V. Stupakov SLAC, Menlo Park, California, USA M.S. Zolotorev LBNL, Berkeley, California, USA
	In Ref. [1] the authors put forward a concept of coherent electron cooling of hadrons. At the core of the concept lies the following idea: a density perturbation induced by an hadron in a co-propagating relativistic electron beam is amplified by several orders of magnitude in a free electron laser (FEL). After the FEL the electron beam is merged again with the hadron one and the amplified electric field in the electron beam acts back on each hadron resulting, after many repetitions, in cooling of the hadron beam. The efficiency of the process is critically determined by the amplification factor of the longitudinal electric field induced by the hadron in the electron beam. In this work we show that this factor is actually considerably smaller than the (conventionally defined) FEL gain with the smallness parameter to be the relative bandwidth of the FEL amplifier. [1] V. N. Litvinenko and Y. S. Derbenev, Phys. Rev. Lett. 102, 114801 (2009).

MOPSO77	Timing Jitter Measurements of the SwissFEL Test Injector	laser, gun, cathode, feedback	140
	C. Vicario, B. Beutner, M.C. Divall, C.P. Hauri, S. Hunziker, M.G. Kaiser, M. Luethi, M. Pedrozzi, T. Schietinger PSI, Villigen PSI, Switzerland C.P. Hauri EPFL, Lausanne, Switzerland
	To reach nominal bunch compression and FEL performance of SwissFEL with stable beam conditions for the users, less than 40fs relative rms jitter is required from the injector. Phase noise measurement of the gun laser oscillator shows an exceptional 30fs integrated rms jitter. We present these measurements and analyze the contribution to the timing jitter and drift from the rest of the laser chain. These studies were performed at the SwissFEL injector test facility, using the rising edge of the Schottky-scan curve and on the laser system using fast digital signal analyzer and photodiode, revealing a residual jitter of 150fs at the cathode from the pulsed laser amplifier and beam transport, measured at 10Hz. Spectrally resolved cross-correlation technique will also be reviewed here as a future solution of measuring timing jitter at 100Hz directly against the pulsed optical timing link with an expected resolution in the order of 50fs. This device will provide the signal for feedback systems compensating for long term timing drift of the laser for the gun as well as for the pulsed lasers at the experimental stations.

MOPSO81	Broad-band Amplifier Based on Two-stream Instability	FEL, plasma, free-electron-laser, space-charge	144
	G. Wang, Y.C. Jing, V. Litvinenko BNL, Upton, Long Island, New York, USA
	A broadband FEL amplifier is of great interests for short-pulse generation in FEL technology as well as for novel hadron beam cooling technique, such as CeC. We present our founding of a broadband amplification in 1D FEL based on electron beam with two energy peaks and a strong space charge forces. We present the optimization of such amplifier and connect its origin to the two-stream instability in electron plasma. In this work, we study how the two-stream instability affects the FEL process and consider various applications in amplifying short spikes of electron current modulation.

MOPSO84	Numerical Investigations of Transverse Gradient Undulator Based Novel Light Sources	FEL, laser, undulator, simulation	152
	T. Zhang, D. Wang, G.L. Wang, H.F. Yao SINAP, Shanghai, People's Republic of China J.S. Liu, C. Wang, W.T. Wang, Z.N. Zeng Shanghai Institute of Optics and Fine Mechanics, Shanghai, People's Republic of China J.Q. Wang, S.H. Wang IHEP, Beijing, People's Republic of China
	With the stat-of-the-art laser technique, the quality of electron beam generated from laser-plasma accelerator (LPA) is now becoming much more better. The natural merits LPA beam, e.g. high peak current, ultra-low emittance and ultra-short bunch length, etc., pave the way to the novel light sources, especially in the realm of developing much compact X-ray light sources, e.g. table-top X-ray free-electron laser, although the radiation power is limited by the rather larger energy spread than conventional LINAC. Luckily, much more power could be extracted by using the undulator with transverse gradient (TGU) when energy spread effect could be compensated. Here we introduce a novel soft x-ray light source driven by LPA based on TGU technique. Meanwhile we present a simple idea on how to achieve much higher rep-rate (e.g. ~100 kHz) storage ring based FELs boosted by TGU.

TUOANO02	Long-term Stable, Large-scale, Optical Timing Distribution Systems With Sub-femtosecond Timing Stability	laser, polarization, feedback, optics	156
	M.Y. Peng, P.T. Callahan, F.X. Kaertner, A.H. Nejadmalayeri MIT, Cambridge, Massachusetts, USA K. Ahmed, S. Valente, M. Xin DESY, Hamburg, Germany P. Battle, T.D. Roberts AdvR, Inc., Montana, USA J.M. Fini, L. Grüner-Nielsen, E. Monberg, M. Yan OFS Laboratories, New Jersey, USA F.X. Kaertner CFEL, Hamburg, Germany
	Funding: US Department of Energy Contract DE-SC0005262 and Center for Free-Electron Laser Science, DESY, Hamburg Sub-fs X-ray pulse generation in kilometer-scale FEL facilities will require sub-fs long-term timing stability between optical sources over kilometer distances. We present here key developments towards a completely fiber-coupled, sub-fs optical timing distribution system. Our approach [] is to lock a femtosecond pulsed laser to a microwave reference and distribute its pulse train through fiber links stabilized by balanced optical cross-correlators (BOCs) []. First, we verified that low-noise optical master oscillators for sub-fs timing distribution are available today; the measured jitter for two commercial femtosecond lasers is less than 70 as for frequencies above 1 kHz. Second, we developed a novel 1.2 km dispersion-compensated, polarization-maintaining fiber link to eliminate drifts induced by polarization mode dispersion. Link stabilization for 16 days showed 0.6 fs RMS timing drift and during a 3-day interval only 0.13 fs drift. Lastly, we fabricated a hybrid-integrated BOC using PPKTP waveguides [*] to eliminate alignment drifts and to reduce the link operation power by a factor of 10-100, which will reduce timing errors induced by fiber nonlinearities. J. Kim et al., Nat. Photon., 2, 12, 733–736, 2008. J. Kim et al., Opt. Lett., 32, 9, 1044–1046, 2007. * A. H. Nejadmalayeri et al., Opt. Lett., 34, 16, 2522–2524, 2009.
	Slides TUOANO02 [1.387 MB]

TUOANO04	PITZ Experience on the Experimental Optimization of the RF Photo Injector for the European XFEL	emittance, laser, cathode, brightness	160
	M. Krasilnikov, H.-J. Grabosch, M. Groß, L. Hakobyan, I.I. Isaev, L. Jachmann, M. Khojoyan, W. Köhler, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, A. Shapovalov, F. Stephan, G. Vashchenko, S. Weidinger, R.W. Wenndorff DESY Zeuthen, Zeuthen, Germany G. Asova INRNE, Sofia, Bulgaria K. Flöttmann, M. Hoffmann, G. Klemz, S. Lederer, H. Schlarb, S. Schreiber DESY, Hamburg, Germany Ye. Ivanisenko PSI, Villigen PSI, Switzerland M.A. Nozdrin JINR, Dubna, Moscow Region, Russia V.V. Paramonov RAS/INR, Moscow, Russia D. Richter HZB, Berlin, Germany S. Rimjaem Chiang Mai University, Chiang Mai, Thailand I.H. Templin, I. Will MBI, Berlin, Germany
	The Photo Injector Test facility at DESY, Zeuthen site (PITZ), develops high brightness electron sources for modern free electron lasers. A continuous experimental optimization of the L-band photo injector for such FEL facilities like FLASH and the European XFEL has been performed for a wide range of electron bunch charges – from 20 pC to 2 nC – yielding very small emittance values for all charge levels. Experience and results of the experimental optimization will be presented in comparison with beam dynamics simulations. The influence of various parameters onto the photo injector performance will be discussed. Phys. Rev. ST Accel. Beams 15, 100701 (2012)
	Slides TUOANO04 [3.126 MB]

TUOBNO03	An RF Deflecting Cavity Based Spreader System for Next Generation Light Sources	gun, FEL, cavity, dipole	173
	C. Sun, L.R. Doolittle, P. Emma, J.-Y. Jung, M. Placidi, A. Ratti LBNL, Berkeley, California, USA
	Lawrence Berkeley National Laboratory (LBNL) is developing design concepts for a multi-beamline (up to 10 lines) soft x-ray FEL array powered by a superconducting linear accelerator with a high bunch repetition rate of approximately one MHz. The FEL array requires a beam spreader system which can distribute individual electron bunches from the linac to each independently configurable beamline. We propose a new spreader system using RF deflecting cavities to deflect electron bunches as an alternative design to the fast kicker scheme. This RF approach offers more stable deflection amplitude while removing the limitations on the bunch repetition rate characteristic of the kicker approach. In this work, we describes the design concept of this RF based spreader system, including technical choices, design parameters and beamline optics. [1] M. Placidi et al., Proceedings of IPAC2012, New Orleans, Louisiana, USA, pp.1765-1767
	Slides TUOBNO03 [1.391 MB]

TUICNO01	Progress in SRF Guns	gun, SRF, cavity, cathode	176
	S.A. Belomestnykh BNL, Upton, Long Island, New York, USA
	Funding: Work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE In the last couple of years great progress has been made in the commissioning and operation of SRF electron beam sources. Both elliptical cavity designs and reentrant cavities have been developed. This talk will review recent progress in SRF guns.
	Slides TUICNO01 [12.748 MB]

TUOCNO01	Electron Beam Longitudinal Phase Space Manipulation by Means of an AD-HOC Photoinjector Laser Pulse Shaping	linac, FEL, laser, simulation	180
	G. Penco, D. Castronovo, M.B. Danailov, G. De Ninno, A.A. Demidovich, S. Di Mitri, W.M. Fawley, L. Giannessi, C. Spezzani, M. Trovò Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	In a seeded FEL machine as FERMI, the interplay between the electrons energy curvature and the seed laser frequency chirp has a relevant impact on the output FEL spectrum. It is therefore crucial controlling and manipulating the electron beam longitudinal phase space at the undulator entrance. In case of very short bunches, i.e. high compression scheme, the longitudinal wakefields generated in the linac induce a positive quadratic curvature in the electrons longitudinal phase space that is hard to compensate by tuning the phase of the main RF sections or the possible high harmonic cavity. At FERMI we have experimentally exploited a longitudinal ramp current distribution at the cathode, obtained with an ad-hoc photoinjector laser pulse shaping, to linearize the longitudinal wakefields in the downstream linac and flatten the electrons energy distribution, as theoretical foreseen in [1]. Longitudinal phase space measurements in this novel configuration are here presented, providing a comparison with the typical longitudinal flat-top profile. [1] Phys. Rev. Special Topics - Accel. and Beams 9 (12), 120701 (2006)
	Slides TUOCNO01 [28.792 MB]

TUOCNO04	Feasibility of CW and LP Operation of the XFEL Linac	cryomodule, linac, HOM, cavity	189
	J.K. Sekutowicz, V. Ayvazyan, J. Branlard, M. Ebert, J. Eschke, T. Feldmann, A. Gössel, D. Kostin, I.M. Kudla, W. Merz, F. Mittag, C. Müller, R. Onken, I. Sandvoss, E. Schneidmiller, A.A. Sulimov, M.V. Yurkov DESY, Hamburg, Germany W. Cichalewski, A. Piotrowski, K.P. Przygoda TUL-DMCS, Łódź, Poland K. Czuba Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland W. Jałmużna Embedded Integrated Control Systems GmbH, Hamburg, Germany J. Szewiński NCBJ, Świerk/Otwock, Poland
	The European XFEL superconducting linac is based on cavities and cryomodules (CM) developed for TESLA linear collider. The XFEL linac will operate nominally in short pulse (sp) mode with 1.3 ms RF pulses (650 μs rise time and 650 μs long bunch train). For 240 ns bunch spacing and 10 Hz RF-pulse repetition rate, up to 27000 bunches per second can be accelerated to 17.5 GeV to generate uniquely high average brilliance photon beams at very short wavelengths. While many experiments can take advantage of full bunch trains, others prefer an increased to several μ-seconds intra-pulse distance between bunches, or short bursts with a kHz repetition rate. For these types of experiments, the high average brilliance can be preserved only with duty factors much larger than that of the currently proposed sp operation. In this contribution, we discuss progress in the R&D program for future upgrade of the European XFEL linac, namely an operation in the continuous wave (cw) and long pulse (lp) mode, which will allow for more flexibility in the electron and photon beam time structure.
	Slides TUOCNO04 [8.910 MB]

TUOCNO05	Design Concepts for a Next Generation Light Source at LBNL	FEL, linac, laser, undulator	193
	J.N. Corlett, A.P. Allezy, D. Arbelaez, K.M. Baptiste, J.M. Byrd, C.S. Daniels, S. De Santis, W.W. Delp, P. Denes, R.J. Donahue, L.R. Doolittle, P. Emma, D. Filippetto, J.G. Floyd, J.P. Harkins, G. Huang, J.-Y. Jung, D. Li, T.P. Lou, T.H. Luo, G. Marcus, M.T. Monroy, H. Nishimura, H.A. Padmore, C. F. Papadopoulos, G.C. Pappas, S. Paret, G. Penn, M. Placidi, S. Prestemon, D. Prosnitz, H.J. Qian, J. Qiang, A. Ratti, M.W. Reinsch, D. Robin, F. Sannibale, R.W. Schoenlein, C. Serrano, J.W. Staples, C. Steier, C. Sun, M. Venturini, W.L. Waldron, W. Wan, T. Warwick, R.P. Wells, R.B. Wilcox, S. Zimmermann, M.S. Zolotorev LBNL, Berkeley, California, USA C. Adolphsen, K.L.F. Bane, Y. Ding, Z. Huang, C.D. Nantista, C.-K. Ng, H.-D. Nuhn, C.H. Rivetta, G.V. Stupakov SLAC, Menlo Park, California, USA D. Arenius, G. Neil, T. Powers, J.P. Preble JLAB, Newport News, Virginia, USA C.M. Ginsburg, R.D. Kephart, A.L. Klebaner, T.J. Peterson, A.I. Sukhanov Fermilab, Batavia, USA
	Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 The NGLS collaboration is developing design concepts for a multi-beamline soft x-ray FEL array powered by a superconducting linear accelerator, operating with a high bunch repetition rate of approximately 1 MHz. The CW superconducting linear accelerator design is based on developments of TESLA and ILC technology, and is supplied by an injector based on a high-brightness, high-repetition-rate photocathode electron gun. Electron bunches from the linac are distributed by RF deflecting cavities to the array of independently configurable FEL beamlines with nominal bunch rates of ~100 kHz in each FEL, with uniform pulse spacing, and some FELs capable of operating at the full linac bunch rate. Individual FELs may be configured for different modes of operation, including self-seeded and external-laser-seeded, and each may produce high peak and average brightness x-rays with a flexible pulse format, and with pulse durations ranging from femtoseconds and shorter, to hundreds of femtoseconds. In this paper we describe current design concepts, and progress in R&D activities.
	Slides TUOCNO05 [5.982 MB]

TUPSO18	Optimization of Dielectric Loaded Metal Waveguides for Acceleration of Electron Bunches using Short THz Pulses	acceleration, space-charge, laser, emittance	250
	A. Fallahi, F.X. Kaertner CFEL, Hamburg, Germany F.X. Kaertner, A. Sell, L.J. Wong MIT, Cambridge, Massachusetts, USA
	Funding: DARPA contract number N66001-11-1-4192 and the Center for Free-Electron Laser Science, DESY Hamburg The last decade has witnessed extensive research efforts to reduce the size of charged particle accelerators to achieve compact devices for providing relativistic particles. To this end, various methods such as laser plasma and dielectric wakefield acceleration are investigated and their pros and cons are studied. With the advent of efficient THz generation techniques based on optical rectification, THz waveguides are also considered to be proper candidates for compact accelerators. Sofar, the proposed schemes toward high power THz generation are capable of producing short pulses, which dictates the study of particle acceleration in the pulsed regime rather than continuous-wave regime. Therefore, THz waveguides are more suitable than cavities for the considered purpose. Consequently, various effects such as group velocity mismatch and group velocity dispersion start to influence the acceleration scenario and impose limits on the maximum energy gain from the pulse. In this contribution, we investigate electron bunch acceleration and compression in dielectrically loaded metal waveguides for the THz wavelength range and present design methodologies to optimize their performance. Liang Jie Wong, Arya Fallahi, and Franz X. Kärtner. "Compact electron acceleration and bunch compression in THz waveguides." Optics Express 21, no. 8 (2013): 9792-9806.

TUPSO19	The Photocathode Laser System for the APEX High Repetition Rate Photoinjector	laser, cathode, controls, feedback	255
	D. Filippetto, L.R. Doolittle, G. Huang, G. Marcus, H.J. Qian, F. Sannibale LBNL, Berkeley, California, USA
	Funding: DOE grants No. DE-AC02-05CH11231. The APEX injector has been built and commissioned at LBNL. A CW-RF Gun accelerates electron bunches to up 750 keV at MHz repetition rate. Different high efficiency photocathodes with different work functions are being tested with the help of a load lock system. The photocathode drive laser is thus conceived to provide up to 40 nJ per pulse in the UV and 200 nJ per pulse in the green at 1 MHz, with transverse and longitudinal shaping (flat top, up to 60 ps) for electron beam creation. A transfer line of about 15 meters has been designed and optimized for minimal jitters. Remote control of repetition rate, energy and position have been implemented on the system, together with offline and online diagnostic for beam monitoring. Here we present the laser system setup as well as the first measurements on longitudinal pulse shaping and jitter characterization.

TUPSO22	Status of SwissFEL Undulator Lines	undulator, quadrupole, dipole, alignment	263
	R. Ganter, M. Aiba, H.-H. Braun, M. Calvi, P. Heimgartner, G. Janzi, H. Jöhri, R. Kobler, F. Löhl, M. Negrazus, L. Patthey, E. Prat, S. Reiche, S. Sanfilippo, U. Schaer, T. Schmidt, L. Schulz, V. Vranković, J. Wickstroem PSI, Villigen PSI, Switzerland
	An overview of the Aramis Hard-X ray FEL line of SwissFEL is presented, showing its future integration in the tunnel as well as the space reservation for possible future upgrades: Athos Soft X-ray FEL line, post-undulator deflecting cavities. The design of the FEL components like the energy collimator, the matching sections or the dog leg transfer line linking the linac to the future Athos line are almost completed. The characterization of the in-vacuum undulator prototype is described in a companion paper. The installation of the components will start in spring 2015 while the first photons are planned for December 2016 with the alignment and adjustment of the undulators foreseen for first SASE operation by spring 2017 .

TUPSO24	Dispersion Based Beam Tilt Correction	quadrupole, FEL, sextupole, emittance	267
	M.W. Guetg, B. Beutner, E. Prat, S. Reiche PSI, Villigen PSI, Switzerland
	In Free Electron Lasers (FEL), a transverse centroid misalignment of longitudinal slices in an electron bunch reduces the effective overlap between radiation field and electron bunch and therefore the FEL performance. The dominant sources of slice misalignments for FELs are the incoherent and coherent synchrotron radiation within bunch compressors as well as transverse wake fields in the accelerating cavities. This is of particular importance for over-compression which is required for one of the key operation modes for the SwissFEL planned at the Paul Scherrer Institute. The centroid shift is corrected using corrector magnets in dispersive sections, e.g. the bunch compressors. First and second order corrections are achieved by pairs of sextupole and quadrupole magnets in the horizontal plane while skew quadrupoles correct to first order in the vertical plane. Simulations and measurements at the SwissFEL Injector Test Facility are done to investigate the proposed correction scheme for SwissFEL. This paper presents the methods and results obtained.

TUPSO25	Status of the EU-XFELl Laser Heater	laser, vacuum, undulator, alignment	271
	M. Hamberg, V.G. Ziemann Uppsala University, Uppsala, Sweden
	Funding: This work was supported by the Swedish Research Council under contract number DNR-828-2008-1093. We describe the technical layout and the status of the laser heater system for the EuXFEL. The laser heater is needed to increase the momentum spread of the electron beam to prevent micro-bunching instabilities in the linac.

TUPSO27	Design for a Fast, XFEL-Quality Wire Scanner	photon, radiation, vacuum, instrumentation	276
	M.A. Harrison, R.B. Agustsson, T.J. Campese, P.S. Chang, A.Y. Murokh, M. Ruelas RadiaBeam, Santa Monica, USA
	RadiaBeam Technologies has designed and manufactured a new wire scanner for high-speed emittance measurements of XFEL-type beams of energy 139 MeV. Using three 25-micron thick tungsten wires, this wire scanner measures vertical and horizontal beam size as well as transverse spatial correlation in one pass. The intensity of the beam at a wire position is determined from emitted bremsstrahlung photons as measured by a BGO scintillator system. The wires are transported on a two-ended support structure moved by a ball-screw linear stage. The double-ended structure reduces vibrations in the wire holder, and the two-bellows design negates the effects of air pressure on the motion. The expected minimum beam size measurable by this system is on the order of 10 microns with 0.1-micron accuracy. To achieve this, new algorithms are presented that reduce the effect of the non-zero thickness of the wire on the wire scan output. In addition, novel calculations are presented for determining the elliptical geometric parameters (vertical and horizontal beam size and correlation, or alternatively, the axis lengths and rotation) of the beam from the wire scanner measurements.

TUPSO28	Development of Photocathode RF-gun at PAL	gun, laser, emittance, coupling	279
	J.H. Hong, J.H. Han, H.-S. Kang, Y.W. Parc, S.J. Park, Y.J. Park PAL, Pohang, Kyungbuk, Republic of Korea I.S. Ko POSTECH, Pohang, Kyungbuk, Republic of Korea
	We are developing two types of S-band photocathode RF-guns for the X-ray free electron laser (XFEL) at Pohang Accelerator Laboratory (PAL). One is a 1.6-cell RF-gun with a dual side coupler and two pumping ports. This RF-gun is similar to the earlier guns developed at PAL. The other one is a 1.5-cell RF-gun with a coaxial coupler and a cathode preparation system. This RF-gun is similar to the DESY-type L-band RF-gun. We have designed and fabricated two types of RF-guns. In this paper we introduce and compare two different RF-guns.

TUPSO32	Project of the Short Pulse Facility at KAERI	quadrupole, gun, kicker, bunching	287
	N. Vinokurov, S.V. Miginsky BINP SB RAS, Novosibirsk, Russia S. Bae, B.A. Gudkov, B. Han, K.H. Jang, Y.U. Jeong, H.W. Kim, K. Lee, S.V. Miginsky, J. Mun, S. H. Park, G.I. Shim, N. Vinokurov KAERI, Daejon, Republic of Korea N. Vinokurov NSU, Novosibirsk, Russia
	Funding: This work is supported by the WCI Program of the National Research Foundation of Korea funded by the Ministry of Education, Science, and Technology of Korea (NRF Grant No. WCI 2011-001). The low-energy electron accelerator with subpicosecond electron bunches is under construction at Korea Atomic Energy Research Institute (KAERI). It will serve as the user facility for high-energy ultrafast electron difraction and synchronized high-power terahertz pulse and short x-ray pulse generation. The accelerator consists of RF gun with photocathode and 20-MeV linac. The bunching of accelerated beam is achieved in the ninety-degree achromatic bend. After that fast kicker deflects some of bunches to the target for x-ray generation, other bunches come to terahertz radiator (undulator or multifoil). Bunches from the RF gun are also planned to use for ultrafast electron difraction. Some detailes of the design, current status of the project and future plans are described.

TUPSO33	The Commissioning of Tess: An Experimental Facility for Measuring the Electron Energy Distribution From Photocathodes	cathode, laser, brightness, vacuum	290
	L.B. Jones, R.J. Cash, B.D. Fell, K.J. Middleman, B.L. Militsyn, T.C.Q. Noakes STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom D.V. Gorshkov, H.E. Scheibler, A.S. Terekhov ISP, Novosibirsk, Russia
	ASTeC have developed a Transverse Energy Spread Spectrometer (TESS) – an experimental facility to characterise the energy distribution of electrons emitted by a photocathode. Electron injector brightness is fundamentally limited by the width of this distribution or energy spread, and brightness will be increased significantly by reducing the longitudinal and transverse energy spread at source. TESS supports photocathode performance measurements at room and LN2-temperature under illumination from a range of fixed- and variable-wavelength light sources, allowing characterisation of both metal and semiconductor photocathodes. Preliminary work with GaAs* has shown that electron energy spread is dependent on the quantum efficiency (Q.E.) of the photocathode source, and TESS includes a piezo-electric leak valve to allow controlled degradation of the photocathode Q.E. whilst monitoring the energy spread of emitted electrons. This system offers huge potential to support future photocathode R&D work into a range of photocathode materials. Using GaAs photocathodes activated to high levels of Q.E. in our photocathode preparation facility*, we present commissioning results for TESS. Proc. IPAC ’12, TUPPD067, 1557-1559 ** Proc. IPAC ’11, THPC129, 3185-3187

TUPSO35	The MAX IV Linac as X-Ray FEL Injector: Comparison of Two Compression Schemes	linac, emittance, wakefield, FEL	294
	O. Karlberg, F. Curbis, S. Thorin, S. Werin MAX-lab, Lund, Sweden
	The MAX IV linac will be used for injections and top up of two storage rings and at the same time provide a high brightness pulses to a short pulse facility (SPF) and an X-ray FEL (phase 2). Compression in the linac is done in two double achromats which implies a positive R56 unlike the commonly used chicane compressor scheme with negative R56. Compression using the achromats scheme requires the electron bunch to be accelerated on a falling RF slope resulting in an energy chirp that longitudinal wakefields will boost along the linac. This permits a stronger compression. In this proceeding we will present how the longitudinal wakefields interact with the bunch compression in the double achromat scheme compared with the chicane compression case. Focus is brought on how the unique MAX IV linac lattice is fully capable to cope with the high demands of an FEL injector. The charge related electron beam jitter in both set-ups will also be investigated.

TUPSO36	Beam Dynamics Optimization for the High Brightness PITZ Photo Injector Using 3D Ellipsoidal Cathode Laser Pulses	laser, emittance, cathode, simulation	298
	M. Khojoyan, M. Krasilnikov, F. Stephan, G. Vashchenko DESY Zeuthen, Zeuthen, Germany
	Funding: The work is funded by the German Federal Ministry of education and Research, project 05K10CHE “Development and experimental test of a laser system for producing quasi 3D ellipsoidal laser pulses”. The Photo Injector Test facility at DESY, Zeuthen Site (PITZ) is one of the leading producers of high brightness electron beams for linac based Free Electron Lasers (FELs) with a specific focus on the requirements of FLASH and the European XFEL. The main activities at PITZ are devoted to the detailed characterization and optimization of electron sources yielding to an extremely small transverse beam emittance. The cathode laser pulse shaping is considered as one of the key issues for the high brightness photo injector. Beam dynamics simulations show that the injector performance could be further improved by replacing the typical cylindrically shaped PITZ bunches by uniformly filled 3D ellipsoidal shaped electron beams. A set of numerical simulations were performed to study the beam dynamics of uniformly filled 3D ellipsoidal bunches with 1 nC charge in order to find an optimum PITZ machine setup which will yield the best transverse emittance. Simulation results comparing both options of cylindrical and 3D ellipsoidal beams are also presented and discussed.

TUPSO39	Development of a Photo Cathode Laser System for Quasi Ellipsoidal Bunches at PITZ	laser, diagnostics, polarization, cathode	303
	M. Krasilnikov, M. Khojoyan, F. Stephan DESY Zeuthen, Zeuthen, Germany A. Andrianov, E. Gacheva, E. Khazanov, S. Mironov, A. Poteomkin, V. Zelenogorsky IAP/RAS, Nizhny Novgorod, Russia E. Syresin JINR, Dubna, Moscow Region, Russia
	Funding: The work is funded by the German Federal Ministry of education and Research, project 05K10CHE “Development and experimental test of a laser system for producing quasi 3D ellipsoidal laser pulses”. Cathode laser pulse shaping is one of the key issues for high brightness photo injector optimization. A flat-top temporal profile of the cylindrical pulses reduces significantly the transverse emittance of space charge dominated beams. As a next step towards further improvement in photo injector performance a 3D pulse shaping is considered. An ellipsoid with uniform photon density is the goal of studies in the frame of a Joint German-Russian Research Group, including the Institute of Applied Physics (Nizhny Novgorod), Joint Institute of Nuclear Research (Dubna) and the Photo Injector test facility at DESY, Zeuthen site (PITZ). The major purpose of the project is the development of a laser system capable of producing 3D quasi ellipsoidal bunches and supporting a bunch train structure close to the European XFEL specifications. The laser pulse shaping is realized using the spatial light modulator technique. The laser pulse shape diagnostics based on a cross-correlator is under development as well. Experimental tests of the new laser system with electron beam production are foreseen at PITZ. First results on the quasi ellipsoidal laser pulse shaping will be reported.

TUPSO41	The Ultrashort Beam Linac System and Proposed Coherent THz Radiation Sources at NSRRC	radiation, linac, gun, undulator	309
	W.K. Lau, A.P. Lee NSRRC, Hsinchu, Taiwan N.Y. Huang, Z.Y. Wei NTHU, Hsinchu, Taiwan
	The NSRRC ultrashort beam facility is a low energy linac system which is being built to produce femtosecond electron beam for novel light source development. Experiments on prebunched THz FEL and inverse Compton scattering x-ray source are under study. The electron source is a 2998 MHz, 1.5-cell thermionic rf gun with uneven full-cell to half-cell field ratio that is optimized to produce a energy-chirped electron beam. With movable slits in its vacuum vessel, the alpha magnet system is served also as a beam selector. Further bunch compression is done by velocity bunching in the rf linac. Recent progress of the construction of this facility as well as the design study of a prebunched THz FEL with this ultrashort electron beam will be reported.

TUPSO42	Shimming Strategy for the Phase Shifters Used in the European XFEL	simulation, undulator, laser, target	313
	Y. Li, J. Pflüger, F. Wolff-Fabris XFEL. EU, Hamburg, Germany H.H. Lu, Y.F. Yang IHEP, Beijing, People's Republic of China
	The undulator systems of the European XFEL need a total of 91 Phase Shifters. The 1st field integral of these devices must not exceed 0.004Tmm for working gaps > 16mm. For smaller gaps it is slightly released. In spite of the highly magnetically symmetric design and considerable effort such as the selection and sorting of the magnets small 1st field integral errors cannot be excluded. In this paper a strategy is studied to correct small gap dependent kicking errors as expected for the phase shifters of the XFEL. EU.by using shims of different geometries and sizes. It is found, that small gap dependent kicking errors can well be corrected for using this method. This is a systematic effort to provide effective fast tuning methods, which can be applied for the mass production. The meaning of shim signature will be explained in this paper. The method is demonstrated by simulations and measurements.

TUPSO45	Initial Streak Camera Measurements of the S-band Linac Beam for the University of Hawaii FEL Oscillator	FEL, linac, undulator, radiation	325
	A.H. Lumpkin Fermilab, Batavia, USA M.R. Hadmack, J.M.D. Kowalczyk, J. Madey, E.B. Szarmes University of Hawaii, Honolulu, HI, USA
	Funding: Work at Fermilab supported by Fermi Research Alliance, LLC under U.S.DOE Contract No.DE-AC02-07CH11359. Work at UH supported by U.S. Dept. of Homeland Security grant No. 20120-DN-077-AR1045-02. The S-band linac driven Mark V free-electron laser oscillator (FELO) at the University of Hawai‘i operates in the mid-IR at electron beam energies of 40-45 MeV with a four microsecond macropulse length. Recently investigations of the electron beam micropulse bunch length and phase as a function of macropulse time became of interest for potentially optimizing the FELO performance. These studies involved the implementation of a Hamamatsu C5680 streak camera with dual sweep capabilities and the transport of optical transition radiation (OTR) generated at an upstream Cu mirror and of coherent spontaneous emission radiation (CSER) generated in the undulator to the streak camera location outside of the linac tunnel. Both a fast single-sweep vertical unit and a synchroscan unit tuned to 119.0 MHz were used. Initial results include measurements of the individual CSER (on the FEL7th harmonic at 652 nm) micropulse bunch lengths (3 to 5 ps FWHM), the CSER signal intensity variation along macropulse time, and a detected phase slew of 4 ps over the last 700 ns of the macropulse. Complementary OTR measurements are also being evaluated and will be presented as available.

TUPSO46	Analysis and Measurement of Focusing Effects in a Traveling Wave Linear Accelerator	quadrupole, acceleration, focusing, simulation	329
	H. Maesaka, T. Asaka, H. Ego, T. Hara, T. Inagaki, Y. Otake, T. Sakurai, H. Tanaka, K. Togawa RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	We propose a further precise model of the transverse dynamics in a traveling wave linear accelerator (TWA) and report experimental results to demonstrate the validity of the model. In SACLA, the beam orbit is calculated by using a transfer matrix based on the transverse dynamics model of each component and the matrix is utilized for orbit stabilization, beam envelop matching etc. For the TWA part, a transfer matrix including an emittance damping effect and an edge focusing effect [] is employed. However, the beam orbit measured by rf cavity beam position monitors (RF-BPM) [] did not agree with the calculated orbit, especially for the off-crest acceleration part. Therefore, focusing effects in a TWA structure were analyzed by using a 3-dimensional rf simulation code. The analysis indicated that the transverse dynamics model of the TWA should include an additional quadrupole edge focusing effect. The amount of the additional focusing effect of the TWA was measured in SACLA and the rf simulation result was confirmed to be consistent with the measurement. After the modification of the transverse dynamics model, the beam orbit measured by RF-BPM agrees with the calculation. T. Hara et al., Nucl. Instrum. Methods A 624, 65 (2010). ** H. Maesaka et al., Nucl. Instrum. Methods A 696, 66 (2012).

TUPSO47	First Results of a Longitudinal Phase Space Tomography at PITZ	booster, gun, laser, emittance	334
	D. Malyutin, M. Groß, I.I. Isaev, M. Khojoyan, G. Kourkafas, M. Krasilnikov, B. Marchetti, F. Stephan, G. Vashchenko DESY Zeuthen, Zeuthen, Germany
	The Photo Injector Test facility at DESY, Zeuthen Site (PITZ), was established as a test stand of the electron source for FLASH and the European X-ray Free Electron Laser (XFEL). One of the tasks at PITZ is the detailed characterization of longitudinal properties of the produced electron bunches. The measurements of the electron bunch longitudinal phase space can be done by tomographic methods using measurements of the momentum spectra by varying the electron bunch energy chirp. At PITZ the energy chirp of the electron bunch can be changed by varying the RF phase of the accelerating structure downstream the gun. The resulting momentum distribution can be measured in a dispersive section installed downstream the accelerating structure. The idea of the measurement and the tomographic reconstruction technique is described in this paper. The setup and first measurement results of the bunch longitudinal phase space measurements using the tomographic technique for several electron bunch charges, including 20 pC, 100 pC and 1 nC, are presented as well.

TUPSO50	Numerical Study on Electron Beam Properties in Triode Type Thermionic RF Gun	cavity, gun, cathode, FEL	344
	M. Mishima, M. Inukai, T. Kii, K. Masuda, H. Negm, H. Ohgaki, K. Okumura, M. Omer, K. Torgasin, K. Yoshida, H. Zen Kyoto University, Institute for Advanced Energy, Kyoto, Japan
	The KU-FEL(Kyoto University- Free Electron Laser) facility uses a thermionic 4.5 cell S-band RF gun for electron beam generation because of such advantages over photocathode rf guns as lower cost, higher average current, longer cathode lifetime, and less vacuum requirement. The main disadvantage of using a thermionic RF gun is the back bombardment effect, which causes energy drop in macro pulse of FEL. A triode structure for RF gun was designed in order to minimize the inherent back-bombardment effect. The 2D-simulation has shown significant reduction of back-bombardment power, longitudinal emittance, and an increase of peak current. A coaxial RF cavity was fabricated based on the design for modification of the existing RF gun to a triode type one. The coaxial RF cavity is equipped with gasket tuning system in order to adjust the cavity resonance frequency. However the frequency adjustment by variation of gasket thickness changes the coaxial cavity geometry and might affect the predicted beam optics. Another parameter influencing beam optics is the position of thermionic cathode to be installed in the coaxial cavity, which might vary due to misalignment. K. Masuda, et al., Proceedings of FEL 2009, Liverpool, Pages 281-284 (2009). **K. Torgasin, et al., Proceedings of FEL 2012, Nara(2012).

TUPSO54	Undulators for Free Electron Lasers	undulator, focusing, insertion, insertion-device	351
	C.W. Ostenfeld, M. Pedersen Danfysik A/S, Taastrup, Denmark
	Danfysik has produced insertion devices for the FEL community for almost 10 years. In this poster, we describe two recent undulator deliveries: a 2.8 m long undulator for the FELIX free electron laser, and a 4.5 m device for the FLARE project, both at Radboud University in Nijmegen, in the Netherlands. The device for FELIX is a 2.8 m PPM device, with a peak field of 0.483 T, and a minimum gap of 22 mm. The device for FLARE, is a 4.5 m hybrid device, with special poles, which allow for double focusing. For both devices, we describe the magnetic modelling, and the magnetic performance.

TUPSO55	300 mm Electromagnetic Wiggler for ELBE	wiggler, insertion, insertion-device, vacuum	353
	C.W. Ostenfeld, M. Pedersen Danfysik A/S, Taastrup, Denmark
	Danfysik has designed and built a 300 mm fixed-gap electromagnetic wiggler for the ELBE radiation source at Helmholz Zentrum Dresden Rossendorff. This wiggler will serve as a source of narrow-band THz radiation in the 100 μm to 10 mm range. Due to careful magnetic modelling, and an effective shimming process, we were able to deliver magnetic performance at a high level. We present the details of the modelling, as well as magnetic results.

TUPSO57	Generation of Ultrafast, High-brightness Electron Beams	gun, cathode, cavity, brightness	355
	J.H. Park, H. Bluem, J. Rathke, T. Schultheiss, A.M.M. Todd AES, Princeton, New Jersey, USA
	Funding: This work was supported by the U.S. Department of Energy, under Contract No. DE-SC0009556. The production and preservation of ultrafast, high-brightness electron beams is a major R&D challenge for free electron laser (FEL) and ultrafast electron diffraction (UED) because transverse and longitudinal space charge forces drive emittance dilution and bunch lengthening in such beams. Several approaches, such as velocity bunching and magnetic compression, have been considered to solve this problem but each has drawbacks. We present a concept that uses radial bunch compression in an X-band photocathode radio frequency electron gun. By compensating for the path length differential with a curved cathode in an extremely high acceleration gradient cavity, we have demonstrated numerically the possibility of achieving more than an order of magnitude increase in beam brightness over existing electron guns. The initial thermo-structural analysis and mechanical conceptual design of this electron source are presented.

TUPSO58	Developments of a High-average-current Thermionic RF Gun for ERLs and FELs	gun, cavity, cathode, FEL	359
	J.H. Park, H. Bluem, J. Rathke, T. Schultheiss, A.M.M. Todd AES, Princeton, New Jersey, USA
	Funding: Supported by ONR under Contract No. N00014-10-C-0191. The development of a high-average-current thermionic RF gun with the required beam performance for lasing would provide significant cost of ownership and reliability gains for high-average-power energy recovery linac (ERL) and free electron laser (FEL) devices. The beam for these applications requires high quality and high performance, specifically: low transverse emittance, short pulse duration and high average current. We are developing a gridded thermionic cathode embedded in a copper one-and-half cell UHF cavity to generate the electron beam. The fundamental RF and higher harmonics are combined on the grid and a gated DC voltage controls the beam emission from the cathode. Simulations indicate that short pulse ~ 10 psec, < 1 MeV electron beams with low-emittance ~ 15 mm-mrad at currents ≥ 100 mA can be generated. The elimination of sensitive photocathodes and their drive laser systems would provide significant capital cost saving, improved reliability and uptime due to increased robustness and hence operating and lifecycle cost savings as well. We will present the gun design and performance simulations and the progress achieved to date in optimizing the device.

TUPSO59	Study of a Photocathode-based Microtron using a PIC Code	microtron, laser, acceleration, injection	363
	S. Park Kyungpook National University, Daegu, Republic of Korea K.H. Jang, Y.U. Jeong, S. H. Park, N. Vinokurov KAERI, Daejon, Republic of Korea E.-S. Kim KNU, Deagu, Republic of Korea N. Vinokurov BINP SB RAS, Novosibirsk, Russia
	Korea Atomic Energy Research Institute (KAERI) has used thermionic cathode-based microtron accelerator for operating compact THz FEL due to its compact size and high energy resolution. In this thermionic cathode-based microtron, rightly phased electron bunch train are automatically accelerated during the RF macro-pulse over threshold power for their emission. But, the thermionic cathode should be replaced with a photocathode for applying the microtron to UED or THz/X-ray pump prove experiment requiring femto-second and high peak current. But, it is needed to analyze precisely the electron beam dynamics in a microtron, especially, the relation between the RF phase in a microtron cavity and Laser input time for adapting the photocathode to a microtron. Hence, we conduct computer simulation with 3D PIC-code to find those optimized conditions for operating photocathode-based microtron.

TUPSO60	Status of the Undulator Systems for the European X-ray Free Electron Laser	undulator, controls, laser, FEL	367
	J. Pflüger, M. Bagha-Shanjani, A. Beckmann, K.H. Berndgen, P. Biermordt, G. Deron, U. Englisch, S. Karabekyan, B. Ketenoğlu, M. Knoll, Y. Li, F. Wolff-Fabris, M. Yakopov XFEL. EU, Hamburg, Germany
	The three undulator systems for the European XFEL consist of a total of 91 Undulator Cells. Each cell consists of an Undulator Segment and an intersection. They will be operational by end of 2015. The serial production of the 91 Undulator Segments is a great challenge and without precedence. It is now in full swing. This contribution gives an overview over the most important design aspects as well as the experience and strategy with the serial production. Representative results of magnetic performance are given. The status of the other system components is briefly described.

TUPSO62	Status of the Planar Undulator Applied in HUST THz-FEL Oscillator	undulator, FEL, radiation, focusing	372
	B. Qin, X. Lei, K.F. Liu, X. Liu, P. Tan, Y.Q. Xiong, J. Yang, L. Yang HUST, Wuhan, People's Republic of China Y.B. Wang Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People's Republic of China
	To fulfill the physical requirement of a 50-100 um Free Electron Laser (FEL) oscillator, design considerations of a planar undulator are described. Some technical issues, including the tolerances study, the beam match, the field measurement setup and the influence on the magnetic field by the waveguide are discussed as well.

TUPSO63	High Average Brightness Photocathode Development for FEL Applications	cathode, gun, laser, SRF	376
	T. Rao, I. Ben-Zvi, J. Skaritka, E. Wang BNL, Upton, Long Island, New York, USA
	Next generation, high average flux, light sources call for electron beams with high average current as well as high peak brightness. Alkali antimonide cathodes, especially K2CsSb show great promise in delivering electron beams to meet these requirements. In the past few years, there have been a number of experiments geared towards understanding the stoichiometry, crystalline structure, surface properties and sensitivity of these cathodes. At BNL, we have used the x-ray beams from NSLS, CFN and CHESS for in-situ characterization of K-Cs-Sb cathode growth. We have also designed and built several load-lock systems for ex-situ cathode fabrication and quick cathode exchange, to be used with a number of guns. One load-lock system/cathode combination has been tested with a DC gun and the others will be tested with SRF guns operating at 112 and 704 MHz. In this paper we will present the results on improving the QE with excimer laser and the performance of the load-lock/cathode combination in the guns.

TUPSO64	Short SASE-FEL Pulses at FLASH	laser, FEL, radiation, free-electron-laser	379
	J. Rönsch-Schulenburg, E. Hass, A. Kuhl, T. Plath, M. Rehders, J. Roßbach Uni HH, Hamburg, Germany G. Brenner, C. Gerth, U. Mavrič, H. Schlarb, E. Schneidmiller, S. Schreiber, B. Steffen, M. Yan, M.V. Yurkov DESY, Hamburg, Germany
	Funding: This project has been supported by BMBF under contract 05K10GU2 & FS FLASH 301 FLASH is a high-gain free-electron laser (FEL) in the soft x-ray range. This paper discusses the production of very short FEL pulses in the SASE-mode without an external seeding signal at FLASH in the optimal case the single-spike operation. A new photo-injector laser has been commissioned, which allows the generation of shorter bunches with low bunch charge directly at the photo-cathode. This shorter injector laser reduces the required bunch compression for short pulses and thus allows a stable SASE performance with shorter pulses. First SASE performance using the new injector laser has been demonstrated and electron bunch and FEL radiation properties have been measured. Beam dynamics as well as the optimization of bunch diagnostics for low charge and short bunches are discussed.

TUPSO66	Transport of Terahertz-Wave Coherent Synchrotron Radiation With a Free-electron Laser Beamline at LEBRA	FEL, radiation, undulator, linac	383
	N. Sei, H. Ogawa AIST, Tsukuba, Ibaraki, Japan K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Sakai, T. Tanaka LEBRA, Funabashi, Japan
	Funding: This work was supported by JSPS Grant-in-Aid for Challenging Exploratory Research 2365696. Nihon University and AIST have jointly developed terahertz-wave coherent synchrotron radiation (CSR) at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University. We have already observed intense terahertz-wave radiation from a bending magnet located above an undulator, and confirmed it to be CSR. To avoid a damage caused by ionizing radiation, we worked on transporting the CSR to an experimental room which was next to the accelerator room. By using a beamline of an infrared free-electron laser, the CSR more than 1 mW was successfully transported to the experimental room. The transport of the CSR and imaging experiments with the CSR at LEBARA will be reported. : N. Sei et al., “Observation of intense terahertz-wave coherent synchrotron radiation at LEBRA”, J. Phys. D, 46 (2013) 045104.

TUPSO67	Design Optimization of 100 Kv DC Gun Wehnelt Electrode for FEL Linac at LEBRA	gun, cathode, simulation, extraction	387
	T. Sakai, K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Tanaka LEBRA, Funabashi, Japan
	The 125-MeV electron linac at the Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University has been used for generation of the near infrared FEL and the Parametric X-ray Radiation. In addition, the THz beam generated in a bending magnet became available in the FEL experimental rooms in 2012 by transporting in the FEL optical beam line. The electron gun system for the LEBRA linac can extract the electron beam in three modes, the full bunch, the superimposed and the burst modes. However, the shape of the electron gun wehnelt electrode has not been optimized for the operation with the superimposed or the burst modes; the wehnelt was designed for use in the full bunch operation. The beam trace simulation suggested that the beam extracted from the cathode in the superimposed and the burst modes was slightly lost at the anode due to the strong space charge effect resulted from a high peak extraction current. Therefore, simulation of the beam trace was carried out to optimize the wehnelt shape for the maximum beam extraction efficiency for all the beam operation modes. The present paper reports the result of the simulation on the optimized electron gun design.

TUPSO69	Injector Design Studies for NGLS	gun, emittance, simulation, cathode	391
	C. F. Papadopoulos, P. Emma, D. Filippetto, H.J. Qian, F. Sannibale, M. Venturini, R.P. Wells LBNL, Berkeley, California, USA
	Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231 The APEX project at LBNL is developing an electron injector to operate a high repetition rate x-ray FEL. The injector is based on the VHF gun, a high-brightness, high-repetition-rate photocathode electron gun presently under test at LBNL. The design of the injector is particularly critical because it has to take the relatively low energy beam from the VHF gun, accelerate it at more relativistic energies while simultaneously preserving high-brightness and performing longitudinal compression. The present status of the APEX injector design studies is presented.

TUPSO74	A Coaxially Coupled Deflecting-accelerating Mode Cavity System for Phase-space Exchange (PSEX)	cavity, coupling, simulation, emittance	395
	Y.-M. Shin, P. Piot Northern Illinois University, DeKalb, Illinois, USA M.D. Church Fermilab, Batavia, USA J.H. Park, A.M.M. Todd AES, Princeton, New Jersey, USA
	A feasible method to readily remove energy spread (R56 term) due to thick lens effect of a deflecting mode RF-cavity has been widely investigated for emittance exchange in 6D phase-space,. By means of theoretical calculation and numerical analysis, it was found that an accelerating cavity effectively cancel the longitudinal phase space chirp. We have extensively investigated the combined deflecting-accelerating mode phase-space exchanger with the simple RF distribution system of the beam-pipe coaxial coupler. EM simulations proved the coupling scheme with eigenmode and S-parameter analyses. Currently we are looking into 3D beam dynamics in the system with tracking/particle-in-cell (PIC) simulations and wakefield analysis. Proof-of-concept (POC) experiment is planned with a high-Q normal conducting cavity built in a cryogenic cooling system (liquid nitrogen) in Fermilab. P. Emma, et. al., Phys. Rev. ST Accel. Beams 9, 100702 (2006) ** Zholents and M. Zolotorev, LBNL CBP Seminar (2010) and No. ANL/APS/LS-327(2011)

TUPSO77	Analytical and Numerical Analysis of Electron Trajectories in a 3-D Undulator Magnetic Field	undulator, focusing, radiation, simulation	406
	N.V. Smolyakov, S.I. Tomin NRC, Moscow, Russia G. Geloni XFEL. EU, Hamburg, Germany
	In this contribution we present an analysis of electron trajectories in the three dimensional magnetic field from a planar undulator. The electron trajectory is influenced by the focusing properties of the undulator field. These focusing properties should be taken into account in simulations of spontaneous radiation, which constitutes the background signal of the FEL. The ideal magnetic field of an undulator can be described, in agreement with Maxwell equations, by a sinusoidal vertical magnetic field on the undulator axis, and by horizontal and longitudinal field components that appear out of axis. Exploiting this description for the ideal case, the differential equations of motion were solved by means of a perturbation theory approach, and the corresponding expressions for the electrons velocities and trajectories are derived. A computer code was also written, which relies on the Runge-Kutta algorithm. The analytical and numerical methods could then be compared, showing a good agreement.

TUPSO80	The MAX IV Linac and First Design for an Upgrade to 5 GeV to Drive an X-ray FEL	linac, FEL, simulation, storage-ring	413
	S. Thorin, F. Curbis, N. Čutić, M. Eriksson, O. Karlberg, F. Lindau, A.W.L. Mak, E. Mansten, S. Werin MAX-lab, Lund, Sweden
	The installation of the MAX IV linear accelerator is in full progress, and commissioning is planned to start in the second quarter of 2014. The 3 GeV linac will be used as a full energy injector for the two storage rings, and as a high brightness driver for a Short Pulse linac light source. The linac has been deigned to also handle the high demands of an FEL injector. The long term strategic plan for the MAX IV laboratory includes an extension of the linac to 5 GeV and an X-ray FEL. In this paper we present the both design concept and status of the MAX IV linac along with parameters of the 3 GeV high quality electron pulses. We also present the first design and simulation results of the upgrade to a 5 GeV X-ray FEL driver.

TUPSO81	Challenges for Detection of Highly Intense FEL Radiation: Photon Beam Diagnostics at FLASH1 and FLASH2	FEL, photon, diagnostics, radiation	417
	K.I. Tiedtke, M. Braune, G. Brenner, S. Dziarzhytski, B. Faatz, J. Feldhaus, B. Keitel, M. Kuhlmann, H. Kühn, E. Plönjes, A.A. Sorokin, R. Treusch DESY, Hamburg, Germany
	In spite of the evident progress in the development of FEL facilities, the characterization of important FEL photon beam parameters during FEL-commissioning and user experiments is still a great challenge. In particular pulse-resolved photon beam characterization is essential for most user experiments, but the unique properties of FEL radiation properties such as extremely high peak powers and short pulse lengths makes the shot-to-shot monitoring of important parameters very difficult. Therefore, sophisticated concepts have been developed and used at FLASH in order to measure radiation pulse intensity, beam position and spectral as well as temporal distribution – always coping with the highly demanding requirements of user experiments as well as machine operation. Here, an overview on the photon diagnostic devices operating at FLASH and FLASH II will be presented, with emphasizes on the pulse resolving intensity and energy detectors based on photoionization of rare gases.

TUPSO82	Spectroscopy System for LCLS Photocathodes	vacuum, gun, cathode, emittance	421
	P. Stefan, A. Brachmann, T. Vecchione SLAC, Menlo Park, California, USA
	Funding: Work supported by US DOE contract DE-AC02-76SF00515. Photocathode reliability is important from an operational standpoint. Unfortunately LCLS copper photocathodes have not always been reliable. Some have operated well for long periods of time while others have required continual maintenance. It is believed that the observed variations in quantum efficiency, emittance and lifetimes are inherently surface related, corresponding to changes in composition or morphology. The RF Electron-gun Cathode, Electron Surface Spectrometer, or RECESS, system has been commissioned to study this by making essential measurements that could not be obtained otherwise. These involve photocathode surface chemical characterization. The system is designed to use a combination of angle-resolved ultraviolet and x-ray photoelectron spectroscopy and is capable of either stand-alone operation or interoperability with a beam line at SSRL. Here we report on the first commissioning spectra and the direction of the project going forward.

TUPSO83	Quantum Efficiency and Transverse Momentum From Metals	brightness, FEL, vacuum, laser	424
	T. Vecchione, D. Dowell SLAC, Menlo Park, California, USA J. Feng, H.A. Padmore, W. Wan LBNL, Berkeley, California, USA
	Funding: Work supported by US DOE contracts DE-AC02-05CH11231, KC0407-ALSJNT-I0013, and DE-SC000571. QE and transverse momentum are key parameters limiting the achievable brightness of FELs. Despite the importance, little data is available to substantiate current models. Expressions for each and experimental confirmation of each expression with respect to excess energy are presented. Novel instrumentation and analysis techniques developed are described.

TUPSO85	High Brightness Electron Beams from a Multi-filamentary Niobium-tin Photocathode	cathode, emittance, laser, space-charge	431
	C. Vicario, A. Anghel, F. Ardana-Lamas, C.P. Hauri, F. Le Pimpec PSI, Villigen PSI, Switzerland C.P. Hauri EPFL, Lausanne, Switzerland
	High-brightness electron sources are of fundamental interest for modern FELs. Inspired by the micro-structure of field emitter arrays, we propose a new type of metallic photo-cathode consisting of thousands of Nb3Sn micro-columns. With this metallic photo-cathode quantum efficiencies up to 0.5% are achieved under stable operation, and preliminary emittance measurements are presented.

TUPSO86	Photocathode Laser Wavelength-tuning for Thermal Emittance and Quantum Efficiency Studies	laser, emittance, cathode, photon	434
	C. Vicario, S. Bettoni, B. Beutner, M.C. Divall, C.P. Hauri, E. Prat, T. Schietinger, A. Trisorio PSI, Villigen PSI, Switzerland
	SwissFEL compact design is based on extremely low emittance electron beam from an RF photoinjector. Proper temporal and spatial shaping of the photocathode drive laser is employed to reduce the space charge emittance contribution. However, the ultimate limit for the beam emittance is the thermal emittance, which depends on the excess energy of the emitted photoelectrons. By varying the photocathode laser wavelength it is possible to reduce the thermal emittance. For this purpose, we developed a tunable Ti:sapphire laser and an optical parametric amplifier which allow to scan the wavelength between 250 and 305 nm. The system permits to study the thermal emittance and the quantum efficiency evolution as function of the laser wavelength for the copper photocathode in the RF gun of the SwissFEL injector test facility. The results are presented and discussed.

TUPSO88	New Concept for the SwissFEL Gun Laser	laser, cathode, gun, FEL	442
	A. Trisorio, M.C. Divall, C.P. Hauri, C. Vicario PSI, Villigen PSI, Switzerland A. Courjaud Amplitude Systemes, Pessac, France
	The operation of Swiss FEL put very stringent constrains on the gun laser system. First the parameters, such as energy stability, timing jitter, double pulse operation, temporal and spatial pulse shape of the ultra-violet laser pulses used to generate the photo-electrons are challenging even for the state of the art laser technologies. Second, the laser system must be extremely stable, reliable and its maintenance cost as low as possible. In this perspective, we prospected for alternative technologies to the well known, commonly used but costly Ti:sapphire laser systems. We show that a hybrid Yb fiber and solid state Yb:CaF2 amplifier system can be a very interesting approach. This gain medium allows the production of sub-500 fs, high fidelity, high stability, high energy pulses in the ultra-violet with low timing jitter. The system profits of the mature, stable direct diode pumping technology and optimized design. It delivers the two high-energy, shaped UV pulses separated by 28 ns to produce the photo-electrons, a short IR probe (<100 fs FWHM) to temporally characterize those pulses and the two stretched IR pulses ( 50 ps FWHM) necessary for the laser heater.

TUPSO91	FEL R&D Within LA3NET	laser, diagnostics, pick-up, ion	452
	C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom C.P. Welsch The University of Liverpool, Liverpool, United Kingdom
	Funding: Work supported by the EU under Grant Agreement 289191. The detailed diagnostics of the shortest beam pulses in free-electron lasers still pose significant challenges to beam instrumentation. Electro-optical methods are a promising approach for the non-intercepting measurement of electron bunches with a time resolution of better than 50 fs, but suitable optical materials need to be better understood and carefully studied. In addition, adequate timing systems with stability in the fs regime based on mode-locked fibre laser optical clocks, and actively length-stabilised optical fibre distribution require further investigation. Within the EU-funded LA³NET project these important problems are being addressed by an international consortium of research centres, universities, and industry partners. This contribution gives an overview of the LA3NET project and results from initial studies in both areas. It also describes the events, such as schools, topical workshops and conferences that LA3NET will organize.

TUPSO92	Dark Current Measurements at the Rossendorf SRF Gun	cavity, gun, cathode, SRF	455
	R. Xiang, A. Arnold, P.N. Lu, P. Murcek, J. Teichert, H. Vennekate HZDR, Dresden, Germany R. Barday, T. Kamps HZB, Berlin, Germany V. Volkov BINP SB RAS, Novosibirsk, Russia
	Funding: the European Community-Research Infrastructure Activity (EuCARD, contract number 227579) and the German Federal Ministry of Education and Research grant 05 ES4BR1/8 In high gradient photo injectors electron field emission creates so-called dark current. The dark current produces beam loss that increases the radiation level, causes damages to the accelerator components, and produces additional background for the users. Field emitted electrons which stay inside the gun, increases RF power consumption and heat load for the superconducting cavities. It is also believed that dark current is the source of local outgassing and plasma formation which can damage sensitive photocathodes. Thus, to understand and control the dark current has become increasingly important for accelerators. In this presentation, we report on dark current measurement at the ELBE SRF Gun at HZDR. The measurements were carried out with the 3.5 cell-cavity SRF gun and Cs2Te photocathodes. We discuss the dark current behavior for different cavity gradients and various solenoid fields. Simulations have been done to understand the experimental results.

WEIANO01	Towards Zeptosecond-scale Pulses From X-ray Free Electron Lasers	FEL, radiation, undulator, laser	458
	D.J. Dunning, N. Thompson STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom B.W.J. MᶜNeil USTRAT/SUPA, Glasgow, United Kingdom
	The short wavelength and high peak power of the present generation of Free-Electron Lasers (FELs) opens the possibility of ultra-short pulses even surpassing the present (~10-100 attosecond) capabilities of other light sources – but only if x-ray FELs can be made to generate pulses consisting of just a few optical cycles. For hard x-ray operation (<~0.1nm), this corresponds to durations of approximately a single attosecond, and below into the zeptosecond scale. This talk will describe a proposed method [1] to generate trains of few-cycle pulses, at GW peak powers, from existing x-ray FEL facilities by using a relatively short 'afterburner'. Such pulses would enhance research opportunity in atomic dynamics and push capability towards the investigation of electronic-nuclear and nuclear dynamics. The corresponding multi-colour spectral output, with a bandwidth envelope increased by up to two orders of magnitudes over SASE, also has potential applications. [1] D.J. Dunning, B.W.J. McNeil, N.R. Thompson, Phys. Rev. Lett. 110, 104801 (2013).
	Slides WEIANO01 [3.492 MB]

WEOANO01	New Scheme to Generate a Multi-terawatt and Attosecond X-ray Pulse in XFELs	target, laser, undulator, FEL	464
	T. Tanaka RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	A new scheme to be applied in XFELs has been recently proposed, which effectively compresses the X-ray pulse, i.e., shortens the pulse length and enhances the peak power by means of inducing a periodic current enhancement with an optical laser and applying a temporal shift between the X-ray and electron beams. In this paper, detailed mechanism of the new scheme is explained together with numerical results applied to the SACLA XFEL facility. T. Tanaka, PRL 110, 084801 (2013)
	Slides WEOANO01 [4.177 MB]

WEOANO03	Longitudinal Coherence in an FEL With a Reduced Level of Shot Noise	FEL, laser, radiation, undulator	469
	V.A. Goryashko Private Address, Uppsala, Sweden V.G. Ziemann Uppsala University, Uppsala, Sweden
	For a planar free electron laser (FEL) configuration we study self-amplified coherent spontaneous emission driven by a gradient of the bunch current in the presence of different levels of noise in bunches [1]. We calculate the probability density distribution of the maximum power of the radiation pulses for different levels of shot noise. It turns out that the temporal coherence quickly increases as the noise level reduces. We also show that the FEL based on coherent spontaneous emission produces almost Fourier transform limited pulses and the time-bandwidth product is mainly determined by the bunch length and the interaction distance in an undulator. We also propose a scheme that permits the formation of electron bunches with a reduced level of noise and a high gradient of the current at the bunch tail to enhance coherent spontaneous emission. The presented scheme uses effects of noise reduction and controlled microbunching instability and consists of a laser heater, a bunch compressor, and a shot noise suppression section. The noise factor and microbunching gain of the overall proposed scheme with and without laser heater are estimated. V.A. Goryashko and V. Ziemann, Phys. Rev. ST Accel. Beams 16, 030702 (2013).
	Slides WEOANO03 [1.999 MB]

WEIBNO01	Super-radiant Linac-based THz Sources in 2013	laser, undulator, photon, linac	474
	M. Gensch HZDR, Dresden, Germany
	There is a growing interest in THz and far infrared light sources for use in material studies. Both coherent radiative sources (CSR, COTR, etc.) and FEL sources have been developed in the last few years to address this need. This talk will describe recent developments in this growing field.

WEOBNO03	Intense Emission of Smith-Purcell Radiation at the Fundamental Frequency from a Grating Equipped with Sidewalls	radiation, simulation, bunching, solenoid	477
	J.T. Donohue CENBG, Gradignan, France J. Gardelle, P. Modin CEA, LE BARP cedex, France
	The two-dimensional theory of the Smith-Purcell free-electron laser predicts that coherent Smith-Purcell radiation can occur only at harmonics of the frequency of the evanescent wave that is resonant with the beam. Particle-in-cell simulations have shown that in a three-dimensional context, where the lamellar grating has sidewalls, coherent Smith-Purcell radiation can be copiously emitted at the fundamental frequency, for a well-defined range of beam energy. An experiment at microwave frequencies has confirmed this prediction . The power output is considerably greater than for the previously observed emission at the second harmonic, in agreement with three-dimensional simulations . The dependence of frequency on beam energy and emission angle is in good agreement with three-dimensional theory and simulations. Provided that a reduction in scale can be achieved, a path is open to coherent Smith-Purcell radiation at Terahertz frequencies. (1) J. Gardelle, P. Modin and J.T. Donohue, Appl. Phys. Lett. 100, 131103 (2012). (2) J. T. Donohue and J. Gardelle, Appl. Phys. Lett. 99, 161112 (2011).
	Slides WEOBNO03 [11.891 MB]

WEOCNO03	3-D Theory of a High Gain Free-Electron Laser Based on a Transverse Gradient Undulator	FEL, undulator, emittance, radiation	481
	P. Baxevanis, Y. Ding, Z. Huang, R.D. Ruth SLAC, Menlo Park, California, USA
	The performance of a free-electron laser (FEL) depends significantly on the various parameters of the driving electron beam. In particular, a large energy spread in the beam results in a great reduction of the FEL gain, an effect which is relevant when one considers FELs driven by plasma accelerators or storage rings. For such cases, one possible solution is to use a transverse gradient undulator (TGU) [,]. In this concept, the energy spread problem is mitigated by properly dispersing the e-beam and introducing a linear, transverse field dependence in the undulator. This paper presents a self-consistent theoretical analysis of a TGU-based high gain FEL, taking into account three-dimensional (3-D) effects and beam size variations along the undulator [*]. The results of our theory compare favorably with simulation and are used in fast optimization studies of various X-ray FEL configurations. T. Smith et al., J. Appl. Phys. 50, 4580 (1979). Z. Huang, Y. Ding, C. Schroeder, Phys. Rev. Lett. 109, 204801 (2012). *P. Baxevanis, R. Ruth, Z. Huang, Phys. Rev. ST-AB 16, 010705 (2013).
	Slides WEOCNO03 [3.217 MB]

WEPSO01	Free Electron Lasers in 2013	FEL, undulator, laser, free-electron-laser	486
	J. Blau, K. R. Cohn, W.B. Colson, R. Vigil NPS, Monterey, California, USA
	Funding: This work has been supported by the Office of Naval Research. Thirty-seven years after the first operation of the short wavelength free electron laser (FEL) at Stanford University, there continue to be many important experiments, proposed experiments, and user facilities around the world. Properties of FELs in the infrared, visible, UV, and x-ray wavelength regimes are tabulated and discussed.

WEPSO02	Results and Perspectives on the FEL Seeding Activities at FLASH	laser, undulator, FEL, radiation	491
	J. Bödewadt, C. Lechner Uni HH, Hamburg, Germany
	In recent years, several methods of free-electron laser (FEL) seeding, such as high-gain harmonic generation (HGHG), self-seeding, or direct FEL amplification of external seed pulses, have proven to generate intense, highly coherent radiation pulses in the extreme ultraviolet (XUV), soft- (SXR) and hard (HXR) X-ray spectral range. At DESY in Hamburg, the FEL facility FLASH is currently being upgraded by a second undulator beamline (FLASH2) which allows for the implementation of various seeding schemes. The development of high repetition-rate, high-power laser systems allows for the production of seed sources which match the bunch-train pattern of FLASH. Furthermore, the FLASH1 beamline arrangement is well suited for testing various seeding schemes including HGHG, EEHG, HHG-seeding, and hybrid schemes. In this contribution, we* give an overview of latest results and planned FEL seeding activities at FLASH. *Joern Boedewadt on behalf of the FLASH seeding collaboration (DESY, U Hamburg, TU Dortmund, U Uppsala, U Stockholm)

WEPSO04	The Conceptual Design of CLARA, a Novel FEL Test Facility for Ultra-short Pulse Generation	FEL, laser, undulator, free-electron-laser	496
	J.A. Clarke, D. Angal-Kalinin, R.K. Buckley, S.R. Buckley, P.A. Corlett, L.S. Cowie, D.J. Dunning, B.D. Fell, P. Goudket, A.R. Goulden, S.P. Jamison, J.K. Jones, A. Kalinin, B.P.M. Liggins, L. Ma, K.B. Marinov, P.A. McIntosh, J.W. McKenzie, K.J. Middleman, B.L. Militsyn, A.J. Moss, B.D. Muratori, H.L. Owen, R.N.C. Santer, Y.M. Saveliev, R.J. Smith, S.L. Smith, E.W. Snedden, M. Surman, T.T. Thakker, N. Thompson, R. Valizadeh, A.E. Wheelhouse, P.H. Williams STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom R. Appleby, R.J. Barlow, H.L. Owen, M. Serluca, G.X. Xia UMAN, Manchester, United Kingdom R. Appleby, G. Burt, S. Chattopadhyay, D. Newton, A. Wolski Cockcroft Institute, Warrington, Cheshire, United Kingdom R. Bartolini, S.T. Boogert, A. Lyapin JAI, Oxford, United Kingdom N. Bliss, R.J. Cash, G. Cox, G.P. Diakun, A. Gallagher, D.M.P. Holland, B.G. Martlew, M.D. Roper STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom S.T. Boogert Royal Holloway, University of London, Surrey, United Kingdom G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom L.T. Campbell, B.W.J. MᶜNeil USTRAT/SUPA, Glasgow, United Kingdom A.M. Kolano University of Huddersfield, Huddersfield, United Kingdom I.P.S. Martin Diamond, Oxfordshire, United Kingdom D. Newton, A. Wolski The University of Liverpool, Liverpool, United Kingdom V.V. Paramonov RAS/INR, Moscow, Russia
	The conceptual design of CLARA, a novel FEL test facility focussed on the generation of ultra-short photon pulses with extreme levels of stability and synchronisation is described. The ultimate aim of CLARA is to experimentally demonstrate that sub-coherence length pulse generation with FELs is viable, and to compare the various schemes being championed. The results will translate directly to existing and future X-ray FELs, enabling them to generate attosecond pulses, thereby extending the science capabilities of these intense light sources. This paper will describe the design of CLARA, pointing out the flexible features that will be incorporated to allow multiple novel FEL schemes to be proven.

WEPSO05	Progress of the LUNEX5 Project	laser, FEL, undulator, free-electron-laser	502
	M.-E. Couprie, C. Benabderrahmane, L. Cassinari, J. Daillant, C. Evain, N. Hubert, M. Labat, A. Loulergue, J. Lüning, P. Marchand, O. Marcouillé, C. Miron, P. Morin, A. Nadji, P. Roy, T. Tanikawa SOLEIL, Gif-sur-Yvette, France S. Bielawski, M. Le Parquier, E. Roussel, C. Szwaj PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France B. Carré, D. Garzella CEA/DSM/DRECAM/SPAM, Gif-sur-Yvette, France N. Delerue LAL, Orsay, France G. Devanz CEA/IRFU, Gif-sur-Yvette, France A. Dubois CCPMR, Paris, France G. Lambert, R. Lehé, V. Malka, C. Thaury LOA, Palaiseau, France G. Le Bec ESRF, Grenoble, France M. Luong CEA/DSM/IRFU, France
	LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation) aims at investigating the production of short, intense, and coherent pulses in the soft X-ray region, with a 400 MeV superconducting linear accelerator and a laser wakefield accelerator (LWFA), feeding a single Free Electron Laser line with seeding with High order Harmonic in Gas and Echo Enable Harmonic Generation. After the Conceptual Design Report (CDR), R&D has been launched on specific magnetic elements (cryo-ready 3 m long in-vacuum undulator, a variable strong permanent magnet quadrupoles), on diagnostics (Smith-Purcell, electro-optics). In recent transport studies from a LWFA with more realistic beam parameters (1 % energy spread, 1 μm size and 1 mrad divergence) than the ones taken in the CDR, a longitudinal and transverse manipulation enables to provide theoretical amplification. A test experiment is under preparation. The French scientific community is increasing its participation to the use of operating FELs.

WEPSO06	The Test-FEL at MAX-lab: Implementation of the HHG Source and First Results	laser, FEL, radiation, undulator	507
	F. Curbis, N. Čutić, F. Lindau, E. Mansten, S. Werin MAX-lab, Lund, Sweden F. Brizuela, B. Kim, A. L'Huillier Lund University, Division of Atomic Physics, Lund, Sweden M. Gisselbrecht SLF, Lund, Sweden
	The test-FEL at MAX-lab is a development set-up for seeding techniques. After the successful demonstration of coherent harmonic generation from a conventional laser, the new layout now presents a gas target for generation of harmonics. The drive laser will be up-converted and the low harmonics (around 100 nm) will seed the electron beam. The energy modulated electrons will then be bunched in the dispersive section and will radiate in the second undulator. We will detect the second harmonic of the HHG radiation around 50 nm. This experiment has several challenges never tried before: co-propagation of the electron beam and the drive laser, interaction of the electron beam with the gas in the target, no-focusing of the harmonics and no drive laser removal. The commissioning will show if this kind of in-line chamber has advantages with respect to more traditional approaches with optical beam transport. The results are relevant for many facilities that are planning to implement HHG seeding in the near future.

WEPSO07	Simulation Studies for an X-ray FEL Based on an Extension of the MAX IV Linac	FEL, linac, undulator, radiation	510
	F. Curbis, N. Čutić, O. Karlberg, F. Lindau, A.W.L. Mak, E. Mansten, S. Thorin, S. Werin MAX-lab, Lund, Sweden
	It is well known that the few X-ray FELs around the world are severely overbooked by users. Having a medium energy linac, such as the one now being installed at the MAX IV laboratory, it becomes natural to think about slightly increasing the electron energy to drive an X-ray FEL. This development is now included in the long term strategic plan for the MAX IV laboratory. We will present the current FEL studies based on an extension of the MAX IV linac to 5 GeV to reach the Angstrom region. The injector for the MAX IV accelerator complex is also equipped with a photocathode gun, capable of producing low emittance electron beam. The bunch compression and linearization of the beam is taken care by two double achromats. The basic FEL layout would consist of short period undulators with tapering for extracting all the power from the electron beam. Self-seeding is considered as an option for increasing the spectral and intensity stability.

WEPSO09	Two-Color Self-seeding and Scanning the Energy of Seeded Beams at LCLS	FEL, photon, background, free-electron-laser	514
	F.-J. Decker, Y. Ding, Y. Feng, M. Gibbs, J.B. Hastings, Z. Huang, H. Lemke, A.A. Lutman, A. Marinelli, A. Robert, J.L. Turner, J.J. Welch, D.H. Zhang, D. Zhu SLAC, Menlo Park, California, USA
	Funding: Work supported by U.S. Department of Energy, Contract DE-AC02-76SF00515. The Linac Coherent Light Source (LCLS) produces typically SASE FEL pulses with an intensity of up to 5 mJ and at high photon energy a spread of 0.2% (FWHM). Self seeding with a diamond crystal reduces the energy spread by a factor of 10 to 40. The range depends on which Bragg reflection is used, or the special setup of the electron beam like over-compression. The peak intensity level is lower by a factor of about five, giving the seeded beam an advantage of about 2.5 in average intensity over the use of a monochromator with SASE. Some experiments want to scan the photon energy, which requires that the crystal angle be carefully tracked. At certain energies and crystal angles different lines are crossing which allows seeding at two or even three different colors inside the bandwidth of the SASE pulse. Out-off plane lines come in pairs, like [1 -1 1] and [-1 1 1], which can be split by using the yaw angle adjustments of the crystal, allowing a two-color seeding for all energies above 4.83 keV.

WEPSO10	Increased Stability Requirements for Seeded Beams at LCLS	FEL, linac, klystron, undulator	518
	F.-J. Decker, W.S. Colocho, Z. Huang, R.H. Iverson, A. Krasnykh, A.A. Lutman, M.N. Nguyen, T.O. Raubenheimer, M.C. Ross, J.L. Turner, L. Wang SLAC, Menlo Park, California, USA
	Funding: Work supported by U.S. Department of Energy, Contract DE-AC02-76SF00515. Running the Linac Coherent Light Source (LCLS) with self-seeded photon beams requires better electron beam stability, especially in energy, to reduce the otherwise huge intensity variations of more than 100%. Code was written to identify and quantify the different jitter sources. Some improvements are being addressed, especially the stability of the modulator high voltage of some critical RF stations. Special setups like running the beam off crest in the last part of the linac can also be used to reduce the energy jitter. Even a slight dependence on the transverse position was observed. The intensity jitter distribution of a seeded beam is still more contained with peaks up too twice the average intensity, compared to the jitter distribution of a SASE beam going through a monochromator, which can have damaging spikes up to 5 times the average intensity.

WEPSO11	Coherent X-Ray Seeding Source for Driving FELs	cavity, undulator, FEL, radiation	522
	A. Novokhatski, F.-J. Decker, R.O. Hettel, Z. Huang, H.-D. Nuhn, M.K. Sullivan SLAC, Menlo Park, California, USA
	Funding: "Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515 The success of the hard X-ray self-seeding experiment at the LCLS is very important in that it provided narrow, nearly transform-limited bandwidth from the FEL, fulfilling a beam quality requirement for experimental applications requiring highly monochromatic X-rays. Yet, because the HXRSS signal is generated random spikes of noise, it is not a truly continuous monochromatic seed signal and even higher FEL performance would be achieved using a continuous seed source. We propose developing such a source using an X-ray cavity to achieve a continuous, narrow band X-ray seed signal. This cavity consists of four crystals with corresponding Bragg angles of about 45 degrees for each. We will analyze and the interaction of X-rays and electron beams with this cavity. This source uses a train of electron bunches initially accelerated in a linear accelerator which then pass through a radiator element situated within an X-ray cavity. The number of bunches is proportional to the achievable Q-value of the X-ray cavity and may be in the range of 10-100. We do not need a high output power of X-ray beams, which leads to relaxed electron beam requirements. We will consider several options.

WEPSO14	Towards High Frequency Operation with a Multi-Grating Smith-Purcell FEL	simulation, radiation, FEL, bunching	525
	J.T. Donohue CENBG, Gradignan, France J. Gardelle CEA, LE BARP cedex, France
	Three-dimensional simulations and experiments have shown that, for a grating equipped with sidewalls, copious emission of coherent Smith-Purcell (SP) radiation at the fundamental frequency of the evanescent surface wave is possible 1, 2. Since the underlying theory is scale invariant, the wavelength emitted is reduced in proportion to a uniform rescaling of the grating. In order to increase our 5 GHz to 100 GHz , the grating surface would be reduced by a factor of 400, which would lead to greatly reduced power. In addition, the required beam might be hard to generate. To avoid this, we propose to use several gratings in parallel with no overall reduction in the total width and the same beam as in our microwave experiment. For this scheme to succeed, it is essential that the bunching in the different gratings be coherent. . Simulations suggest that this occurs for as much as a ten-fold scale reduction. To test this idea, an experiment is using several gratings is being performed. 1. J. T. Donohue and J. Gardelle, Appl. Phys. Lett. 99, 161112 (2011). 2. J. Gardelle, P. Modin and J.T. Donohue, Appl. Phys. Lett. 100, 131103 (2012),.

WEPSO17	High-resolution Seeding Monochromator Design for NGLS	FEL, optics, undulator, brightness	529
	Y. Feng, J.B. Hastings, J. Wu SLAC, Menlo Park, California, USA P. Emma, R.W. Schoenlein, T. Warwick LBNL, Berkeley, California, USA
	Funding: DOE/BES A high-resolution soft X-ray seeding monochromator has been designed for self-seeding the Next-Generation Light Source (NGLS). The seeding monochromator system consists of a single variable-line-spacing grating, three mirrors and an exit slit and operates in the “fixed-focus” mode to achieve complete tuning of the seeding energy in range from 200 to 2000 eV with a nearly constant resolving power of over 2x104. The optical delay is less than 1 ps. The design is based upon a fully coherent treatment of the SASE FEL beam propagating from the upstream SASE undulator through the entire seeding monochromator system. This approach guides the design optimization in order to preserve the transverse beam profile entering the seeding undulator to ensure maximum efficiency.

WEPSO19	A Full Beam 1D Simulation Code for Modeling Hybrid HGHG/EEHG Seeding Schemes for Evaluating the Dependence of Bunching Factor Bandwidth on Multiple Parameters	bunching, laser, simulation, FEL	533
	C.M. Fortgang, B.E. Carlsten, Q.R. Marksteiner, N.A. Yampolsky LANL, Los Alamos, New Mexico, USA
	Multiple seeding schemes are available for design of narrow-band, short-wavelength FELs. Analysis of such schemes often focus on the amplitude of the final bunching factor b, and how far it is above shot noise. Only under ideal conditions is the bandwidth of b FT limited. We have developed a 1D simulation tool that models complex hybrid seeding schemes using macro properties of the entire beam bunch to assess effects on both the amplitude and bandwidth of b. In particular the effects on bunching factor from using non-ideal beam driven radiators for downstream modulators, energy slew and curvature, and energy spread are investigated with the 1D tool.

WEPSO22	FERMI@Elettra Status Report	FEL, laser, linac, free-electron-laser	546
	L. Giannessi, E. Allaria, F. Bencivenga, C. Callegari, F. Capotondi, D. Castronovo, P. Cinquegrana, P. Craievich, I. Cudin, G. D'Auria, M. Dal Forno, M.B. Danailov, R. De Monte, G. De Ninno, A.A. Demidovich, S. Di Mitri, B. Diviacco, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, E. Ferrari, L. Fröhlich, P. Furlan Radivo, G. Gaio, M. Kiskinova, M. Lonza, B. Mahieu, N. Mahne, C. Masciovecchio, F. Parmigiani, G. Penco, M. Predonzani, E. Principi, L. Raimondi, F. Rossi, L. Rumiz, C. Scafuri, C. Serpico, P. Sigalotti, S. Spampinati, C. Spezzani, M. Svandrlik, C. Svetina, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy P. Craievich PSI, Villigen PSI, Switzerland L. Giannessi ENEA C.R. Frascati, Frascati (Roma), Italy B. Mahieu CEA/DSM/DRECAM/SPAM, Gif-sur-Yvette, France
	Funding: Work supported in part by the Italian Ministry of University and Research under grants FIRB-RBAP045JF2 and FIRB-RBAP06AWK3 In this paper we report about the status of FERMI, the seeded Free Electron Laser located at the Elettra laboratory in Trieste, Italy. The facility welcomed the first external users on FEL-1 between December 2012 and March 2013, operating at wavelengths between 65 and 20 nm. Variable polarization and tunability of the radiation wavelength were widely used. Photon energies attained up to 200 microJoule, depending on the grade of spectral purity requested and on the selected wavelength. Pump-probe experiments were performed, both by double FEL pulses obtained via double pulse seeding of the electron beam and by providing part of the seed laser to the experimental stations as user laser. The FEL-2 line, covering the lower wavelength range between 20 and 4 nm thanks to a double stage cascaded HGHG scheme, operating in the "fresh bunch injection” mode, generated its first coherent photons in October 2012 and has seen further progress during the commissioning phases in 2013, at higher electron beam energy. In fact we will also report on the linac energy increase to 1.5 GeV and on the repetition rate upgrade from 10 to 50 Hz and eventually comment on the FEL operability and uptime.

WEPSO24	Compact XFEL Light Source	emittance, laser, FEL, cathode	757
	W.S. Graves, K.K. Berggren, F.X. Kaertner, D.E. Moncton MIT, Cambridge, Massachusetts, USA P. Piot Northern Illinois University, DeKalb, Illinois, USA
	Funding: This work was supported by DARPA grant N66001-11-1-4192, CFEL DESY, DOE grants DE-FG02-10ER46745, and NSF grant DMR-1042342. X-ray free electron laser studies are presented that rely on a nanostructured electron beam interacting with a “laser undulator” configured in the head-on inverse Compton scattering geometry. The structure in the electron beam is created by a nanoengineered cathode that produces a transversely modulated electron beam. Electron optics demagnify the modulation period and then an emittance exchange line translates the modulation to the longitudinal direction resulting in coherent bunching at x-ray wavelength. The predicted output radiation at 1 keV from a 7 MeV electron beam reaches 10 nJ or 6X10⁸ photons per shot and is fully coherent in all dimensions, a result of the dominant mode growth transversely and the longitudinal coherence imposed by the electron beam nanostructure. This output is several orders of magnitude higher than incoherent inverse Compton scattering and occupies a much smaller phase space volume, reaching peak brilliance of 10²⁷ and average brilliance of 10¹⁷ photons/(mm² mrad² 0.1% sec).

WEPSO26	Status of the Flash Facility	photon, FEL, undulator, radiation	550
	K. Honkavaara, B. Faatz, J. Feldhaus, S. Schreiber, R. Treusch, M. Vogt DESY, Hamburg, Germany
	The free-electron laser user facility FLASH at DESY (Hamburg, Germany)finished its 4th user period in February 2013. In total 2715 hours of SASE radiation has been delivered to user experiments with photon wavelengths between 4.2 nm and 44 nm with up to 5000 photon pulses per second. After a shutdown to connect the second undulator line - FLASH2 - to the FLASH linac, and a following commissioning period, FLASH is scheduled to continue user operation in October 2013. The year 2014 will be dedicated to the 5th period of user experiments. The commissioning of FLASH2 will take place in 2014 parallel to FLASH1 user operation.

WEPSO27	Recent LCLS Performance From 250 to 500 eV	FEL, undulator, diagnostics, laser	554
	R.H. Iverson, J. Arthur, U. Bergmann, C. Bostedt, J.D. Bozek, A. Brachmann, W.S. Colocho, F.-J. Decker, Y. Ding, Y. Feng, J.C. Frisch, J.N. Galayda, T. Galetto, Z. Huang, E.M. Kraft, J. Krzywinski, J.C. Liu, H. Loos, X.S. Mao, S.P. Moeller, H.-D. Nuhn, A.A. Prinz, D.F. Ratner, T.O. Raubenheimer, S.H. Rokni, W.F. Schlotter, P.M. Schuh, T.J. Smith, M. Stanek, P. Stefan, M.K. Sullivan, J.L. Turner, J.J. Turner, J.J. Welch, J. Wu, F. Zhou SLAC, Menlo Park, California, USA P. Emma LBNL, Berkeley, California, USA R. Soufli LLNL, Livermore, California, USA
	Funding: Work supported by US Department of Energy contract DE-AC02-76SF00515 and BES. The Linac Coherent Light Source is an X-ray free-electron laser at the SLAC National Accelerator Laboratory. It produces coherent soft and hard X-rays with peak brightness nearly ten orders of magnitude beyond conventional synchrotron sources and a range of pulse durations from 500 to <10 fs. The facility has been operating at X-ray energy from 500 to 10,000eV. Users have expressed great interest in doing experiments with X-Rays near the carbon absorption edge at 284eV. We describe the operation and performance of the LCLS in the newly established regime between 250 and 500eV. [1] Emma, P. et al., “First lasing and operation of an ˚angstrom-wavelength free-electron laser,” Nature Pho- ton. 4(9), 641–647 (2010).

WEPSO28	Fast Electron Beam and FEL Diagnostics at the ALICE IR-FEL at Daresbury Laboratory	FEL, cavity, laser, diagnostics	557
	F. Jackson, D. Angal-Kalinin, D.J. Dunning, J.K. Jones, A. Kalinin, T.T. Thakker, N. Thompson STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom D. Angal-Kalinin, D.J. Dunning, J.K. Jones, N. Thompson Cockcroft Institute, Warrington, Cheshire, United Kingdom
	The ALICE facility at Daresbury Laboratory is an energy recovery based infra-red free electron laser of the oscillator type that has been operational since 2010. Recently fast diagnostics have been installed to perform combined measurements on pulse-by pulse FEL pulse energy and bunch-by-bunch electron bunch position and arrival time. These measurements have highlighted and quantified fast instabilities in the electron beam and consequently the FEL output, and are presented and discussed here.

WEPSO31	THz Radiation Source Potential of the R&D ERL at BNL	gun, SRF, linac, emittance	566
	D. Kayran, I. Ben-Zvi, Y.C. Jing, B. Sheehy BNL, Upton, Long Island, New York, USA
	Funding: Work supported by BSA DOE, Contract No. DE-AC02-98CH10886 An ampere class 20 MeV superconducting Energy Recovery Linac (ERL) is under commissioning at Brookhaven National Laboratory (BNL) for testing concepts for high-energy electron cooling and electron-ion colliders. This ERL will be used as a test bed to study issues relevant for very high current ERLs. High repetition rate (9.5 MHz), CW operation and high performance of electron beam with some additional components make this ERL an excellent driver for high power coherent THz radiation source. We discuss potential use of BNL ERL as a source of THz radiation and results of the beam dynamics simulation. We present the status and commissioning progress of the ERL. Ilan Ben-Zvi. et al. Coherent harmonic generation of THz radiation using wakefield bunching (presented at this conference)

WEPSO33	Remote RF Synchronization With Femtosecond Drift at PAL	laser, free-electron-laser, photon, radio-frequency	570
	J. Kim, K. Jung, J. Lim KAIST, Daejeon, Republic of Korea L. Chen Idesta Quantum Electronics, New Jersey, USA S. Hunziker PSI, Villigen PSI, Switzerland F.X. Kaertner CFEL, Hamburg, Germany H.-S. Kang, C.-K. Min PAL, Pohang, Kyungbuk, Republic of Korea
	Funding: This research was supported by the PAL-XFEL Project, South Korea. We present our recent progress in remote RF synchronization using an optical way at PAL. A 79.33-MHz, low-jitter fiber laser is used as an optical master oscillator (OMO), which is locked to the 2.856-GHz RF master oscillator (RMO) using a balanced optical-microwave phase detector (BOM-PD). The locked optical pulse train is then transferred via a timing-stabilized 610-m long optical fiber link. The output is locked to the 2.856 GHz voltage controlled oscillator (VCO) using the second BOM-PD, which results in remote synchronization between the RMO and the VCO. We measured the long-term phase drift between the input optical pulse train and the remote RF signals using an out-of-loop BOM-PD, which results in 2.7 fs (rms) drift maintained over 7 hours. We are currently working to measure the phase drift between the two RF signals and reduce the phase drift over longer measurement time.

WEPSO34	Proposal for a Scheme to Generate a 10 tw Power Level, Femtosecond X-ray Pulses for Bio-imaging of Single Protein Molecules at the European XFEL	undulator, photon, FEL, radiation	574
	V. Kocharyan, G. Geloni, E. Saldin, S. Serkez, I. Zagorodnov DESY, Hamburg, Germany O. Yefanov CFEL, Hamburg, Germany
	Crucial parameters for bio-imaging experiments are photon energy range, peak power and pulse duration. For a fixed resolution, the largest diffraction signals are achieved at the longest wavelength supporting that resolution. In order to perform these experiments at the European XFEL, we propose to use a novel configuration combining self-seeding and undulator tapering techniques with the emittance-spoiler method. Experiments at the LCLS confirmed the feasibility of these three techniques. Their combination allows obtaining a dramatic increase the XFEL output peak power and a shortening of the photon pulse duration to levels sufficient for performing bio-imaging of single protein molecules at the optimal photon-energy range between 3 keV and 5 keV. We show here that it is possible to achieve up to a 100-fold increase in peak-power of the X-ray pulses at the European XFEL: the X-ray beam would be delivered in 10 fs-long pulses with 50 mJ energy each at a photon energy around 4 keV. We confirm by simulations that one can achieve diffraction before destruction with a resolution of 0.25 nm resolution.

WEPSO37	Femtosecond Fiber Timing Distribution System for the Linac Coherent Light Source	laser, free-electron-laser, linac, background	583
	H. Li, P.H. Bucksbaum, J.C. Frisch, A.R. Fry, J. May, K. Muehlig, S.R. Smith SLAC, Menlo Park, California, USA L. Chen, H.P.H. Cheng Idesta Quantum Electronics, New Jersey, USA F.X. Kaertner CFEL, Hamburg, Germany F.X. Kaertner MIT, Cambridge, Massachusetts, USA A. Uttamadoss PU, Princeton, New Jersey, USA
	Funding: This work is supported by Department of Energy under STTR grant DE-C0004702. We present the design and progress of a femtosecond fiber timing distribution system for the Linac Coherent Light Source (LCLS) at SLAC to enable the machine diagnostic at the 10 fs level. The LCLS at the SLAC is the world’s first hard x-ray free-electron laser (FEL) with unprecedented peak brightness and pulse duration. The time-resolved optical/x-ray pump-probe experiments on this facility open the era of exploring the ultrafast dynamics of atoms, molecules, proteins, and condensed matter. However, the temporal resolution of current experiments is limited by the time jitter between the optical and x-ray pulses. Recently, sub-25 fs rms jitter is achieved from an x-ray/optical cross-correlator at the LCLS, and external seeding is expected to reduce the intrinsic timing jitter, which would enable full synchronization of the optical and x-ray pulses with sub-10 fs precision. Of such a technique, synchronization between seed and pump lasers would be implemented. Preliminary test results of the major components for a 4 link system will be presented. Currently, the system is geared towards diagnostics to study the various sources of jitter at the LCLS. P. Emma et al.,Nat. Photonics 4,641-647(2010). J. Kim et al.,Opt. Lett,, 31,3659(2006). J. Kim et al.,Opt. Lett,, 32,1044(2007). J.Kim et al.,Nat. Photonics 2,733-736(2008).

WEPSO41	Feasibility Studies for Echo-enabled Harmonic Generation on CLARA	laser, bunching, FEL, radiation	588
	I.P.S. Martin, R. Bartolini Diamond, Oxfordshire, United Kingdom R. Bartolini JAI, Oxford, United Kingdom N. Thompson Cockcroft Institute, Warrington, Cheshire, United Kingdom N. Thompson STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	The Compact Linear Accelerator for Research and Applications (CLARA) is a proposed single-pass FEL test facility, designed to facilitate experimental studies of advanced FEL techniques applicable to the next generation of light source facilities. One such scheme under consideration is Echo-Enabled Harmonic Generation (EEHG). In this paper we explore the suitability of CLARA for carrying out studies of this scheme, combining analytical and numerical calculations to determine likely hardware operating ranges, parameters tolerances and estimated FEL performance. A possible adaptation to convert EEHG into a short-pulse scheme is also considered.

WEPSO43	EEHG and Femtoslicing at DELTA	undulator, radiation, laser, synchrotron	594
	R. Molo, H. Huck, M. Huck, M. Höner, S. Khan, A. Schick, P. Ungelenk DELTA, Dortmund, Germany
	The ultrashort-pulse facility at DELTA (a 1.5-GeV synchrotron light source operated by the TU Dortmund University) based on the coherent harmonic generation (CHG) technique will be upgraded using echo-enabled harmonic generation (EEHG) in order to reach shorter wavelengths. A laser-induced energy modulation is employed in the CHG and EEHG schemes to create a periodic electron density modulation, but can also be used to generate ultrashort pulses of incoherent radiation at arbitrary wavelengths by transversely displacing the off-energy electrons(femtoslicing). A new storage-ring lattice for DELTA will be presented that not only offers enough free straight sections for an EEHG and femtoslicing setup, but also allows to operate both radiation sources simultaneously.

WEPSO46	Study on the fluctuation of electron beam position in KU-FEL	gun, FEL, cavity, feedback	602
	K. Okumura, M. Inukai, T. Kii, T. Konstantin, K. Masuda, K. Mishima, H. Negm, H. Ohgaki, M. Omer, Y. Tsugamura, K. Yoshida, H. Zen Kyoto University, Institute for Advanced Energy, Kyoto, Japan
	Stability of electron beam is important for stable FEL operation. In Kyoto University MIR-FEL facility (KU-FEL), a BPM (Beam Position Monitor) system consisting of six 4-button electrode type BPMs was installed for monitoring of the electron beam position. The fluctuation of the electron beam position has been observed in horizontal and vertical directions. The origin of the beam position fluctuation is not clarified. In horizontal direction, the main fluctuation source is expected to be the energy fluctuation. As the one of candidate of the energy fluctuation, the cavity temperature of the RF gun has been suspected because the gun is operated in detuned condition [1] which enhances beam energy dependence on the cavity temperature. Another candidate is considered to be the fluctuation of the RF power fed to the gun. Therefore, we start to study the effect of the cavity temperature and the RF power on the position of electron beam. In this conference, we will present the measured result and numerical evaluation of the beam position dependence on temperature and RF power. [1] H. Zen, et al, “Beam Energy Compensation in a Thermionic RF Gun by Cavity Detuning,” IEEE transaction on nuclear science, Vol.56, No. 3, Pages 1487-1491 (2009)

WEPSO47	Simulation Results of Self-seeding Scheme in PAL-XFEL	radiation, undulator, simulation, emittance	606
	Y.W. Parc, J.H. Han, I. Hwang, H.-S. Kang PAL, Pohang, Kyungbuk, Republic of Korea I.S. Ko POSTECH, Pohang, Kyungbuk, Republic of Korea J. Wu SLAC, Menlo Park, California, USA
	There are two major undulator lines in Pohang Accelerator Laboratory XFEL (PAL XFEL), soft X-ray and hard X-ray. For the hard X-ray undulator line, self-seeding is the most promising approach to supply narrow bandwidth radiation to the users. The electron energy at hard X-ray undulator is 10 GeV and the central wavelength is 0.1 nm. We plan to provide the self-seeding option in the Phase I operation of PAL-XFEL. In this talk, the simulation results for the self-seeding scheme of hard X-ray undulator line in PAL XFEL will be presented.

WEPSO48	Simulation Studies of FELs for a Next Generation Light Source	undulator, FEL, photon, simulation	609
	G. Penn, P. Emma, G. Marcus, J. Qiang, M.W. Reinsch LBNL, Berkeley, California, USA
	Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Several possible FEL beamlines for a Next Generation Light Source are studied. These beamlines collectively cover a wide range of photon energies and pulse lengths. Microbunching and transverse offsets within the electron beam, generated through the linac, have the potential to significantly impact the longitudinal and transverse coherence of the x-ray pulses. We evaluate these effects and set tolerances on beam properties required to obtain the desired properties of the x-ray pulses.

WEPSO50	FLASH2 Beamline and Phontondiagnostics Concepts	photon, diagnostics, laser, undulator	614
	E. Plönjes, B. Faatz, J. Feldhaus, M. Kuhlmann, K.I. Tiedtke, R. Treusch DESY, Hamburg, Germany
	The FLASH II project will upgrade the soft X-ray free electron laser FLASH at DESY into a multi-beamline FEL user facility with the addition of a second undulator line FLASH2. The present FLASH linear accelerator will drive both undulator lines and FLASH2 will be equipped with variable-gap undulators to be able to deliver two largely independent wavelengths to user endstations at FLASH1 and FLASH2 simultaneously. A new experimental hall will offer space for up to seven user endstations, some of which will be installed permanently. The beamline system will be set up to cover a wide wavelength range with up to three beamlines capable of delivering the 5th harmonic at 0.8 nm and a fundamental in the water window while others will cover the longer wavelengths of 6 - 40 nm and beyond. Photon diagnostics have been developed for many years at FLASH and are in routine operation. Online measurements of intensity, position, wavelength, wavefront, and pulse length are optimized as well as photon beam manipulation tools such as a gas absorber and filters. Civil construction and installations of FLASH II are on-going and first beam is expected for early 2014.

WEPSO51	Self-seeding Design for SwissFEL	FEL, undulator, simulation, radiation	618
	E. Prat, S. Reiche PSI, Villigen PSI, Switzerland
	The SwissFEL facility, planned at the Paul Scherrer Institute, will provide SASE and self-seeded FEL radiation at a hard (1-7 Å) and soft (7-70 Å) X-ray FEL beamlines. This paper presents the current status of the self-seeding design for SwissFEL. The layout and full 6D start-to-end simulation results are presented for the hard X-ray beamline. Studies for different charges and optimization of the first and second undulator stages are shown.

WEPSO53	Harmonic Lasing at the LCLS	FEL, radiation, undulator, simulation	623
	D.F. Ratner, Z. Huang, P.A. Montanez SLAC, Menlo Park, California, USA E. Allaria Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy W.M. Fawley, L.N. Rodes LBNL, Berkeley, California, USA E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	Funding: Department of Energy The LCLS beamlines deliver X-rays to users at photon energies up to 24 keV. With the fundamental wavelength limited to around 10 keV, there is user interest in the third harmonic, which can reach a few percent of the total beam power. McNeil et al* and Schneidmiller and Yurkov** have showed that introducing phase shifts or attenuators into the undulator line can increase harmonic power by driving lasing at the third harmonic. With the development of self-seeding chicanes, LCLS is now in position for a proof-of-principle experiment. Here we present simulations and plans for an experimental test following commissioning of the Soft X-ray Self-Seeding system. B.W.J. McNeil, G.R.M. Robb, M.W. Poole and N.R. Thompson, Phys. Rev. Lett., 96 084801 (2006) *E. Schneidmiller and M. Yurkov, PR-STAB, 14 080702 (2012)

WEPSO57	Optimization of a Dedicated Bio-imaging Beamline at the European X-ray Fel	undulator, photon, FEL, radiation	632
	E. Saldin, G. Geloni, V. Kocharyan, S. Serkez DESY, Hamburg, Germany
	We recently proposed a basic concept for design and layout of a dedicated undulator source for bio-imaging experiments at the European XFEL. Here we present an optimization of that concept. The core of the scheme is composed by soft and hard X-ray self-seeding setups. Using an improved design for both monochromators it is possible to increase the design electron energy up to 17.5 GeV in photon energy range between 2 keV and 13 keV, which is the most preferable for life science experiments. Operating at such high electron energy one increases the X-ray output peak power. Moreover, 17.5 GeV is the preferred operation energy for SASE1 and SASE2 users. This choice will reduce the interference with other undulator lines. We include a study of the performance of the self-seeding scheme accounting for spatiotemporal coupling caused by the use of a single crystal monochromator. This distortion can be easily suppressed by the right choice of diamond crystal planes. The proposed undulator source yields about the same performance as in the case for a X-ray seed pulse with no coupling. Simulations show that the FEL power reaches 2 TW in the 3 keV - 5 keV photon energy range.

WEPSO58	Status Report of the Short-pulse Facility at the Delta Storage Ring	radiation, laser, synchrotron, klystron	642
	A. Schick, H. Huck, M. Huck, M. Höner, S. Khan, R. Molo, P. Ungelenk DELTA, Dortmund, Germany
	Funding: * Work supported by DFG, BMBF and by the Federal State NRW. At DELTA, a 1.5-GeV synchrotron light source operated by the TU Dortmund university, a short-pulse facility employing the CHG (Coherent Harmonic Generation) principle is in operation. Here, the interaction of an intense, ultrashort laser pulse and electrons in an undulator leads to microbunching of a small fraction of the electrons in the bunch. As a consequence, ultrashort, coherent synchrotron-radiation pulses in the VUV regime are emitted at harmonics of the incident laser wavelength. In addition, coherent THz pulses on the sub-ps timescale are generated. In this paper, the latest improvements of the facility and recent measurements are presented, including investigation of the transverse coherence and detection of the CHG radiation using photoemission spectroscopy in a VUV beamline.

WEPSO59	A Possible Upgrade of FLASH for Harmonic Lasing Down to 1.3 nm	undulator, FEL, radiation, simulation	646
	E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	We propose the 3rd harmonic lasing in a new FLASH undulator as a way to produce intense, narrow-band, and stable SASE radiation down to 1.3 nm with the present accelerator energy of 1.25 GeV. To provide optimal conditions for harmonic lasing, we suggest to suppress the fundamental with the help of a special set of phase shifters. We rely on the standard technology of gap-tunable planar hybrid undulators, and choose the period of 2.3 cm and the minimum gap of 0.9 cm; total length of the undulator system is 34.5 m. We demonstrate that the 3rd harmonic lasing at 1.3 nm provides peak power at a gigawatt level and the narrow intrinsic bandwidth, 0.1% (FWHM). Pulse duration can be controlled in the range of a few tens of femtoseconds, and the peak brilliance reaches the value of 10³¹ photons/(s mrad² mm² 0.1% BW). With the given undulator design, a standard option of lasing at the fundamental wavelength to saturation is possible through the entire water window and at longer wavelengths. In this paper we briefly consider additional options such as polarization control, bandwidth reduction, self-seeding, X-ray pulse compression, and two-color operation.

WEPSO62	The IR and THz Free Electron Laser at the Fritz-Haber-Institut	FEL, free-electron-laser, laser	657
	W. Schöllkopf, W. Erlebach, S. Gewinner, G. Heyne, H. Junkes, A. Liedke, G. Meijer, V. Platschkowski, G. von Helden FHI, Berlin, Germany H. Bluem, D. Dowell, K. Jordan, R. Lange, J. Rathke, A.M.M. Todd, L.M. Young AES, Princeton, New Jersey, USA M.A. Davidsaver BNL, Upton, New York, USA S.C. Gottschalk STI, Washington, USA U. Lehnert, P. Michel, W. Seidel, R. Wünsch HZDR, Dresden, Germany H. Loos SLAC, Menlo Park, California, USA
	A mid-infrared oscillator FEL with a design wavelength range from 4 to 50 μm has been commissioned at the Fritz-Haber-Institut in Berlin, Germany, for applications in molecular and cluster spectroscopy as well as surface science. The accelerator consists of a thermionic gridded electron gun, a subharmonic buncher and two S-band standing-wave copper structures. The device was designed to meet challenging specifications, including a final energy adjustable in the range of 15 to 50 MeV, low longitudinal emittance (< 50 keV-psec) and transverse emittance (< 20 π mm-mrad), at more than 200 pC bunch charge with aμpulse repetition rate of 1 GHz and a macro pulse length of up to 15 μs. Two isochronous achromatic 180 degree bends deliver the beam to the undulators, only one of which is presently installed, and to the beam dumps. Calculations of the FEL gain and IR-cavity losses predict that lasing will be possible in the wavelength range from less than 4 to more than 50 μm. First lasing was achieved at a wavelength of 16 μm in 2012. We will describe the FEL system design and performance, provide examples of lasing, and touch on the first anticipated user experiments. W. Schöllkopf et al., MOOB01, Proc. FEL 2012.

WEPSO63	Extension of SASE Bandwidth up to 2 % as a Way to Increase Number of Indexed Images for Protein Structure Determination by Femtosecond X-Ray Nanocrystallography at the European XFEL	radiation, undulator, simulation, photon	661
	S. Serkez, V. Kocharyan, E. Saldin, I. Zagorodnov DESY, Hamburg, Germany G. Geloni XFEL. EU, Hamburg, Germany O. Yefanov CFEL, Hamburg, Germany
	Experiments at the LCLS confirmed the feasibility of femtosecond nanocrystallography for protein structure determination at near-atomic resolution. These experiments rely on X-ray SASE pulses with a few microradians angular spread, and about 0.2 % bandwidth. By indexing individual patterns and then summing all counts in all partial reflections for each index it is possible to extract the square modulus of the structure factor. The number of indexed images and the SASE bandwidth are linked, as an increasing number of Bragg spots per individual image requires an increasing spectral bandwidth. This calls for a few percent SASE bandwidth. Based on start-to-end simulations of the European XFEL baseline, we demonstrate that it is possible to achieve up to a 10-fold increase of the electron energy chirp by strongly compressing a 0.25 nC electron bunch. This allows for data collection with a 2 % SASE bandwidth, a few mJ radiation pulse energy and a few fs-pulse duration, which would increase the efficiency of protein determination at the European XFEL. We prove this concept with simulations of photosystem-I nanocrystals, with a size of about 300 nm.

WEPSO64	Grating Monochromator for Soft X-ray Self-seeding the European XFEL	undulator, FEL, photon, optics	667
	S. Serkez, G. Geloni, V. Kocharyan, E. Saldin DESY, Hamburg, Germany
	Self-seeding implementation in the soft X-ray wavelength range involves gratings as dispersive elements. We study a very compact self-seeding scheme with a grating monochromator originally designed at SLAC, which can be straightforwardly installed in the SASE3 undulator beamline at the European XFEL. The design is based on a toroidal VLS grating at a fixed incidence angle, and without entrance slit. It covers the spectral range from 300 eV to 1000 eV. The performance was evaluated using wave optics method vs ray tracing methods. Wave optics analysis takes into account the actual beam wavefront of the radiation from the FEL source, third order aberrations, and errors from optical elements. We show that, without exit slit, the self-seeding scheme gives the same resolving power (about 7000) as with an exit slit. Wave optics is also naturally applicable to calculations of the scheme efficiency, which include the monochromator transmittance and the effect of the mismatching between seed beam and electron beam. Simulations show that the FEL power reaches 1 TW, with a spectral density about two orders of magnitude higher than that for the SASE pulse at saturation.

WEPSO65	LEBRA Free Electron Laser as a Radiation Source for Photochemical Reactions in Living Organisms	FEL, radiation, controls, laser	675
	F. Shishikura, K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Sakai, T. Tanaka LEBRA, Funabashi, Japan
	The radiation sources commonly used in plant applications are commercially available lamps developed for human lighting applications (fluorescent, metal halide, high-pressure sodium, incandescent, light-emitting diode, and laser diode). In contrast, free-electron lasers (FELs) such as LEBRA-FEL produce high-energy, tunable pulse radiation and thus are promising radiation sources for photochemical research. An advantage of LEBRA-FEL is that the peak intensity ranges from 0.35 to 6.5 microns which are wavelengths coinciding with the absorption peaks of living organisms. Previously, we established a microscopic irradiation technique for delivering visible FEL light to single cells through a tapered glass rod (< 10 microns). However, it is still unclear whether LEBRA-FEL can produce sufficient radiant energy at wavelengths effective for triggering photochemical reactions in living organisms. The aim of this study was to evaluate the effectiveness of LEBRA-FEL in lettuce-seed germination tests. Results show promotion by red light and inhibition by far-red light, indicating that LEBRA-FEL can be used to control lettuce-seed germination.

WEPSO67	Progress with the FERMI Laser Heater Commissioning	FEL, laser, linac, undulator	680
	S. Spampinati, E. Allaria, D. Castronovo, M. Dal Forno, M.B. Danailov, G. De Ninno, A.A. Demidovich, S. Di Mitri, B. Diviacco, W.M. Fawley, E. Ferrari, L. Fröhlich, L. Giannessi, G. Penco, C. Spezzani, M. Trovò Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	FERMI@ELETTRA is a seeded free electron laser facility composed by one linac and two FEL lines named FEL-1 and FEL-2. FEL-1 works in HGHG configuration, while FEL2 is a HGHG cascade implementing "fresh bunch" injection into the second stage. Perfomance of FEL-1 and FEL-2 lines have benefited from the use of the laser heater system, which is located right after the injector, at 100 MeV beam energy. Proper tuning of the laser heater parameters has allowed control of the microbunching instability, which is otherwise expected to degrade the high brightness electron beam quality sufficiently to reduce the FEL power. The laser heater was commissioned one year ago and positive effects upon microbunching instabilities and FEL-1 performance was soon observed. In this work we presents further measurements of microbunching suppression in two compressors scheme showing directly the reduction of beam slice energy spread due to laser heater action. We present measuerements showing the impact of the laser heater on FEL2

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MOOBNO01

First Lasing of FERMI FEL-2

FEL, laser, injection, free-electron-laser

1

L. Giannessi, E. Allaria, D. Castronovo, P. Cinquegrana, G. D'Auria, M. Dal Forno, M.B. Danailov, G. De Ninno, A.A. Demidovich, S. Di Mitri, B. Diviacco, W.M. Fawley, M. Ferianis, E. Ferrari, L. Fröhlich, G. Gaio, R. Ivanov, B. Mahieu, N. Mahne, I. Nikolov, F. Parmigiani, G. Penco, L. Raimondi, C. Serpico, P. Sigalotti, C. Spezzani, M. Svandrlik, C. Svetina, M. Trovò, M. Veronese, D. Zangrando, M. Zangrando
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
M. Dal Forno
DEEI, Trieste, Italy
G. De Ninno, D. Gauthier
University of Nova Gorica, Nova Gorica, Slovenia
E. Ferrari, F. Parmigiani
Università degli Studi di Trieste, Trieste, Italy
L. Giannessi
ENEA C.R. Frascati, Frascati (Roma), Italy
B. Mahieu
CEA/DSM/DRECAM/SPAM, Gif-sur-Yvette, France
M. Zangrando
IOM-CNR, Trieste, Italy

During the month of October 2012 the commissioning of the light source FEL-2 at FERMI was successfully concluded. Fermi FEL-2 is the first seeded FEL operating with a double stage cascade in the "fresh bunch injection" mode*. The two stages are two high gain harmonic generation FELs where the first stage is seeded by the 3rd harmonic of a Ti:Sa laser system, which is up converted to the 4th-6th harmonic. The output of the first stage is then used to seed the second stage. A final wavelengths of 10.8 nm was obtained as the 24th harmonic of the seed wavelength at the end of the two frequency conversion processes, demonstrating that the FEL is capable of producing single mode narrow bandwidth pulses with an energy of several tens of microjoules.
*I. Ben-Zvi, K. M. Yang, L. H. Yu, ”The ”fresh-bunch” technique in FELs”, NIM A 318 (1992), p 726-729

Slides MOOBNO01 [25.265 MB]

MOICNO01

Generation of a Train of Short Pulses by Means of FEL Emission of a Combed Electron Beam

FEL, radiation, undulator, laser

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V. Petrillo
Universita' degli Studi di Milano, Milano, Italy
M.P. Anania, M. Bellaveglia, E. Chiadroni, D. Di Giovenale, G. Di Pirro, M. Ferrario, G. Gatti, R. Pompili, C. Vaccarezza, F. Villa
INFN/LNF, Frascati (Roma), Italy
M. Artioli
ENEA-Bologna, Bologna, Italy
A. Bacci, A.R. Rossi
Istituto Nazionale di Fisica Nucleare, Milano, Italy
A. Cianchi
Università di Roma II Tor Vergata, Roma, Italy
F. Ciocci, G. Dattoli, L. Giannessi, A. Petralia, M. Quattromini, C. Ronsivalle, E. Sabia
ENEA C.R. Frascati, Frascati (Roma), Italy
A. Mostacci
Rome University La Sapienza, Roma, Italy
P. Musumeci
UCLA, Los Angeles, California, USA
J.V. Rau
ISM-CNR, Rome, Italy

We present a direct and powerful method for generating train of radiation pulses based on the FEL radiation from a multi-peaked electron beam produced with a combed laser pulse accelerated and compressed in a linac by the velocity bunching technique. The electron beam, constituted by two bunches, can be extracted from the accelerating section when they are temporaly superimposed but separated in energy, so that each of them is characterized by a different value of the Lorentz factor. When driven in the FEL undulator, they emit two separate spectral lines, according to the FEL resonance condition, that interfere producing fringes in the time-domain. In this way a train of regular pulses can be obtained, without limitation in frequency, and with the perspective of reaching the attosecond domain in the X ray regime.

Slides MOICNO01 [8.836 MB]

MOOCNO01

Emittance Control in the Presence of Collective Effects in the FERMI@Elettra Free Electron Laser Linac Driver

emittance, FEL, linac, brightness

6

S. Di Mitri, E. Allaria, D. Castronovo, M. Cornacchia, P. Craievich, M. Dal Forno, G. De Ninno, W.M. Fawley, E. Ferrari, L. Fröhlich, L. Giannessi, E. Karantzoulis, A.A. Lutman, G. Penco, C. Serpico, S. Spampinati, C. Spezzani, M. Trovò, M. Veronese
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
P. Craievich
PSI, Villigen PSI, Switzerland
M. Dal Forno
University of Trieste, Trieste, Italy
G. De Ninno, S. Spampinati
University of Nova Gorica, Nova Gorica, Slovenia
E. Ferrari
Università degli Studi di Trieste, Trieste, Italy
L. Giannessi
ENEA C.R. Frascati, Frascati (Roma), Italy
A.A. Lutman
SLAC, Menlo Park, California, USA

Recent beam transport experiments conducted on the the linac driving the FERMI@Elettra free electron laser have provided new insights concerning the transverse emittance degradation due to both coherent synchrotron radiation (CSR) and geometric transverse wakefield (GTW), together with methods to counteract such degradation. For beam charges of several 100's of pC, optics control in a magnetic compressor results to minimize the CSR once the H-function is considered*. We successfully extended this approach to the case of a modified double bend achromat system, opening the door to relatively large bending angles and compact transfer lines**. At the same time, the GTWs excited in few mm diameter iris collimators*** and accelerating structures have been characterized in terms of the induced emittance growth. A model integrating both CSR and GTW effects suggests that there is a limit on the maximum obtainable electron beam brightness in the presence of such collective effects.
* S. Di Mitri et al., PRST-AB 15, 020701 (2012)
** S. Di Mitri et al., PRL 110, 014801 (2013)
*** S. Di Mitri et al., PRST-AB 15, 061001 (2012)

Slides MOOCNO01 [6.919 MB]

MOOCNO04

Using a Lienard-Wiechert Solver to Study Coherent Synchrotron Radiation Effects

radiation, simulation, undulator, dipole

17

R.D. Ryne
LBNL, Berkeley, California, USA
B.E. Carlsten, N.A. Yampolsky
LANL, Los Alamos, New Mexico, USA

We report on coherent synchrotron radiation (CSR) modeling using a new first-principles Lienard-Wiechert solver (CSR3D) that simulates real-world number of particles (624 million to 6.24 billion for 100-pC to 1-nC bunch charges). Using this tool, we have verified the limits of applicability of the common 1-D CSR model, including effect due to transverse beam size and shape. We also have observed energy dependent, wavelength dependent, and transverse-size dependent effects on CSR enhancement from microbunching. Additionally, we describe statistics of CSR shot noise, including dependencies on beam energy and transverse position and resulting energy diffusion. We consider the full transverse equation of motion and also quantify the effect of emittance growth from the bunch’s transverse radiation force.

Slides MOOCNO04 [6.258 MB]

MOPSO02

Measurement of Electron-Beam and Seed Laser Properties Using an Energy Chirped Electron Beam

laser, FEL, simulation, linac

24

E. Allaria, G. De Ninno, S. Di Mitri, W.M. Fawley, E. Ferrari, L. Fröhlich, G. Penco, P. Sigalotti, S. Spampinati, C. Spezzani, M. Trovò
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
G. De Ninno, S. Spampinati
University of Nova Gorica, Nova Gorica, Slovenia
E. Ferrari
Università degli Studi di Trieste, Trieste, Italy

We present a new method that uses CCD images of the FERMI electron beam at the dump spectrometer after the undulator to determine various electron beam and external seed laser properties. By taking advantage of the correlation between time and electron beam energy for a quasi-linearly chirped electron beam and the fact that the FERMI seed laser pulse (~180 fs) is much shorter than the electron beam duration (~1 ps), measurements of the e-beam pulse length and temporally local energy chirp and current are possible. Moreover, the scheme allows accurate determination of the timing jitter between the electron beam and the seed laser, as well as a measure of the latter's effective pulse length in the FEL undulators. The scheme can be also provide an independent measure of the energy transferred from the electron beam to the FEL output radiation. We describe the proposed method as well as some experimental results obtained at the seeded FERMI FEL.

MOPSO04

Theoretical Analysis of a Laser Undulator-Based High Gain FEL

laser, FEL, undulator, radiation

27

P. Baxevanis, R.D. Ruth
SLAC, Menlo Park, California, USA

The use of laser (or RF) undulators is nowadays considered attractive for FEL applications, particularly those that aim to utilize relatively low-energy electron beams. In the context of the standard theoretical analysis, the counter-propagating laser pulse is usually treated in the plane-wave approximation, neglecting amplitude and phase variation. In this paper, we develop a three-dimensional, analytical theory of a high-gain FEL based on a laser or RF undulator, taking into account the longitudinal variation of the undulator field amplitude, the laser Gouy phase and the effects of emittance and energy spread in the electron beam. Working in the framework of the Vlasov-Maxwell formalism, we derive a self-consistent equation for the radiation amplitude in the linear regime, which is then solved to good approximation by means of an orthogonal expansion technique [*]. Numerical results obtained from our analysis are used in the study of an example of a compact, laser undulator-based, X-ray FEL.
*P. Baxevanis, R. Ruth, Z. Huang, Phys. Rev. ST-AB 16, 010705 (2013).

MOPSO07

Channeling Radiation With Low-Energy Electron Beams: Experimental Plans and Status at Fermilab

radiation, emittance, brilliance, laser

38

B.R. Blomberg, D. Mihalcea, H. Panuganti, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
C.A. Brau, B.K. Choi, B.L. Ivanov, M.H. Mendenhall
Vanderbilt University, Nashville, TN, USA
W.E. Gabella
Vanderbilt University, W.M. Keck Foundation Free-Electron Laser Center, Nashville, USA
W.S. Wagner
Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Radiation Physics, Dresden, Germany

Funding: This work was supported by the DARPA Axis program under contract AXIS N66001-11-1-4196 with Vanderbilt University and Northern Illinois University.
Channeling radiation is an appealing radiation process to produce x-ray radiation with low-energy electron beams. In this contribution we describe the anticipated performance and preliminary results from a channeling radiation experiment to produce ~ 1.2-keV radiation from a ~ 4-MeV electron beam at Fermilab's high-brightness electron source lab(HBESL). We also discuss plans to produce X-ray radiation ([10,80]-keV photon energy) at Fermilab's advanced superconducting test accelerator (ASTA).

MOPSO08

Unaveraged Modelling of a LWFA Driven FEL

FEL, simulation, radiation, undulator

43

L.T. Campbell, B.W.J. MᶜNeil
USTRAT/SUPA, Glasgow, United Kingdom
F.J. Grüner, A.R. Maier
CFEL, Hamburg, Germany
F.J. Grüner, A.R. Maier
Uni HH, Hamburg, Germany
F.J. Grüner
LMU, Garching, Germany

Preliminary simulations of a Laser Wakefield Field Accelerator driven FEL are presented using the 3D unaveraged, broad bandwidth FEL simulation code Puffin. The radius of the matched low emittance electron beam suggests that the FEL interaction will be strongly affected by radiation diffraction. The parameter scaling and comparison between 3D and equivalent 1D simulations appears to confirm the interaction is diffraction dominated. Nevertheless, output powers are predicted to be greater than those of similar unaveraged FEL models. Possible reasons for the discrepancies between the averaged and unaveraged simulation results are discussed.
[1] - AR Maier, A Meseck, S Reiche, CB Schroeder, T Seggebrock, and F Gruner, Phys Rev X 2, 031019 (2012)

MOPSO09

Investigation of a 2-Colour Undulator FEL Using Puffin

undulator, FEL, radiation, bunching

47

L.T. Campbell, B.W.J. MᶜNeil
USTRAT/SUPA, Glasgow, United Kingdom
S. Reiche
PSI, Villigen PSI, Switzerland

The unaveraged FEL code Puffin* is used to investigate a 2 color FEL. In the scheme under investigation, undulator modules are tuned alternately to generate 2 frequencies quasi-simultaneously, which should result in greater stability than generating them consecutively. The advantage of using Puffin is that it provides the capability of modelling a broad bandwidth spectrum. For example, radiation at 1nm and 2.4nm is difficult to model simultaneously in standard averaged FEL codes. An unaveraged code like Puffin is able to model 2 (or more) wavelengths with a much wider spacing.
* LT Campbell and BWJ McNeil, Phys. Plasmas 19, 093119 (2012)

MOPSO17

The Present Status of the Theory of the FEL-based Hadron Beam Cooling

FEL, hadron, kicker, ion

52

A. Elizarov, V. Litvinenko
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 (CeC)* device is one of the new facilities under construction in BNL. The CeC is a realization of the stochastic cooling with an electron beam serving as a pick-up and kicker. Hadrons generate electron density perturbations in the modulator section, then these perturbations are amplified in an FEL, and then, they accelerate (or decelerate) hadrons in the kicker by electric field with respect to their velocities. Here we present the theoretical description of the modulator sector**,***, where the electron density perturbations are formed and our new results on the time evolution of these perturbations in the FEL section, where they are amplified.
* V. N. Litvinenko, Y. S. Derbenev, Phys. Rev. Lett. 102, 114801 (2009).
** A. Elizarov, V. Litvinenko, G. Wang, IPAC'12, weppr099 (2012).
*** A. Elizarov, V. Litvinenko, IPAC'13, mopwo088 (2013).

MOPSO30

Simple Setups for Carrier-envelope-phase Stable Single-cycle Attosecond Pulse Generation

undulator, laser, radiation, FEL

63

J. Hebling, G. Almási, J.A. Fülöp, M.I. Mechler, Z. Tibai, Gy. Tóth
University of Pecs, Pécs, Hungary

Funding: Work supported by Hungarian Research Fund (OTKA), grant number 101846, and from SROP-4.2.1.B-10/2/KONV-2010-0002 and SROP-4.2.2/B-10/1-2010-0029
Robust methods for producing waveform-controlled half-cycle–few-cycle pulses in the mid-infrared (MIR)–extreme ultraviolet (EUV) spectral range are proposed. They are based on coherent Thomson scattering of THz pulses on relativistic ultrathin electron layers and coherent undulator radiation of relativistic ultrathin electron layers, respectively. The ultrathin electron layers are produced by microbunching of ultrashort electron bunches by a TW power laser in a modulator undulator. According to our numerical calculations it is possible to generate as short as 10 nm long electron layers if a single-period modulator undulator with period length significantly shorter than the resonant one is used and the undulator parameter is only K=0.25. Thomson scattering of THz pulses on ultrathin electron layers with only 50 MeV energy can generate for example 170 as long single-cycle pulses at 80 nm wavelength with 0.1 nJ energy. Coherent undulator radiation of ultrathin electron layers with 450 MeV energy can generate single-cycle radiation in the 20 nm – 1000 nm wavelength range. The corresponding pulse energy and pulse duration vary in the 10 pJ – 2 nJ and 47 as – 2.1 fs ranges, respectively.

MOPSO31

Quasiperiodic Method of Averaging Applied to Planar Undulator Motion Excited by a Fixed Traveling Wave

resonance, undulator, FEL, radiation

762

K.A. Heinemann, J.A. Ellison
UNM, Albuquerque, New Mexico, USA
M. Vogt
DESY, Hamburg, Germany

Funding: The work of JAE and KH was supported by DOE under DE-FG-99ER41104. The work of MV was supported by DESY.
We present a mathematical analysis of planar motion of energetic electrons moving through a planar dipole undulator, excited by a fixed planar polarized plane wave Maxwell field in the X-Ray FEL regime.* We study the associated 6D Lorentz system as the wavelength of the traveling wave varies. The 6D system is reduced, without approximation, to a 2D system (for a scaled energy deviation and generalized ponderomotive phase) in a form for a rigorous asymptotic analysis using the Method of Averaging (MoA), a long time perturbation theory. As the wavelength varies the system passes through resonant and nonresonant (NR) zones and we develop NR and near-to-resonant (NtoR) normal form approximations. For a special initial condition, on resonance, we obtain the well-known FEL pendulum system. We prove NR and NtoR first-order averaging theorems, in a novel way, which give optimal error bounds for the approximations. The NR case is an example of quasiperiodic averaging where the small divisor problem enters in the simplest possible way. To our knowledge the analysis has not been done with the generality here nor has the standard FEL pendulum system been derived with error bounds.
* J.A. Ellison, K. Heinemann, M. Vogt, M. Gooden: arXiv:1303.5797 [physics.acc-ph]

MOPSO34

Highly Efficient, High-energy THz Pulses from Cryo-cooled Lithium Niobate for Accelerator and FEL Applications

laser, acceleration, cryogenics, FEL

68

K.-H. Hong, E. Granados, S.-W. Huang, W.R. Huang, F.X. Kaertner, R. Koustuban, L.E. Zapata
MIT, Cambridge, Massachusetts, USA
F.X. Kaertner
CFEL, Hamburg, Germany

Funding: This work was supported by DARPA under contract N66001-1-11-4192.
Intense, ultrafast THz fields are of great interest for electron acceleration, beam manipulation and measurement, and pump-probe experiments with coherent soft/hard x-ray sources based on FELs or inverse Compton scattering sources. Acceleration at THz frequencies has an advantage over RF in terms of accessing high electric-field gradients (>100 MV/cm), while the beam delivery can be treated quasi-optically. However, high-field THz pulse generation is still demanding when compared with conventional RF generation. In this paper, we present highly efficient, single-cycle, 0.45 THz pulse generation by optical rectification of 1.03 μm pulses in cryogenically cooled lithium niobate (LN). Using a near-optimal duration of 680 fs and a pump energy of 1.2 mJ, we report conversion efficiencies above 3% [1], >10 times higher than previous report (0.24%) [2]. Cryogenic cooling of lithium niobate significantly reduces the THz absorption, which will enable the scaling of THz pulse energies to the mJ. We will also report on polarization and mode conversion using segmented THz waveplates to generate radially-polarized TEM01 modes, suitable for THz electron acceleration in dielectric waveguide.
[1] S.-W. Huang et al., Opt. Lett. 38, 796-798 (2013).
[2] J. A. Fülöp et al., Opt. Lett. 37, 557-559 (2012).

MOPSO43

High Power Laser Transport System for Laser Cooling to Counteract Back-Bombardment Heating in Microwave Thermionic Electron Guns

laser, vacuum, gun, coupling

75

J.M.D. Kowalczyk, M.R. Hadmack, J. Madey, E.B. Szarmes, M.H.E.H. Vinci
University of Hawaii, Honolulu, HI, USA

Funding: This work was funded by the Department of Homeland Security through grant #2011-DN-077-ARI055-03.
Heat from a high power, short pulse laser deposited on the surface of a thermionic electron gun cathode will diffuse into the bulk producing a surface cooling effect that counteracts the electron back-bombardment (BB) heating intrinsic to the gun. The resulting constant temperature stabilizes the current allowing extension of the gun’s peak current and duty cycle. To enable this laser cooling, high power laser pulses must be transported to the high radiation zone of the electron gun, and their transverse profile must be converted from Gaussian to top-hat to uniformly cool the cathode. A fiber optic transport system is simple, inexpensive, and will convert a Gaussian to a top-hat profile. Coupling into the fiber efficiently and without damage is difficult as tight focusing is required at the input and, if coupled in air, the high fluence will breakdown the air resulting in lost energy. We have devised a vacuum fiber coupler (VFC) that allows the focus to occur in vacuum, avoiding the breakdown of air, and have successfully transported 10 ns long, 85 mJ pulses from a 1064 nm Nd:YAG laser through 20 m of 1 mm diameter fiber enabling testing of the laser cooling concept.

MOPSO44

Laser Cooling to Counteract Back-Bombardment Heating in Microwave Thermionic Electron Guns

laser, cathode, gun, simulation

79

J.M.D. Kowalczyk, M.R. Hadmack, J. Madey
University of Hawaii, Honolulu, HI, USA

Funding: This work was funded by the Department of Homeland Security through grant #2011-DN-077-ARI055-03.
A theoretical study of the use of laser cooling to counteract electron back-bombardment heating (BB) in thermionic electron guns is presented. Electron beams with short bunches, minimum energy spread, and maximum length pulse trains are required for many applications, including the inverse-Compton X-ray source being developed at UH. Currently, these three electron beam parameters are limited by BB which causes the cathode temperature and emission current to increase leading to beam loading. Beam loading elongates the bunches by shifting the electrons’ relative phases, introduces energy spread by reducing the energy of electrons emitted later in the macropulse, and forces the use of shorter macropulses to minimize energy spread. Irradiation of the electron gun cathode with a short laser pulse prior to beam acceleration allows the laser heat to diffuse into the cathode bulk effectively cooling the surface and counteracting the BB. Calculation of the the cooling produced by laser pulses of various duration and energy is presented.

MOPSO49

Numerical Accuracy When Solving the FEL Equations

FEL, simulation, undulator, bunching

82

R.R. Lindberg
ANL, Argonne, USA

Funding: U.S. Dept. of Energy Office of Sciences under Contract No. DE-AC02-06CH11357
The usual method of numerically solving the FEL equations involves dividing both the e-beam and radiation field into "slices" that are loaded one at a time into memory. This scheme is only first order accurate in the discretization of the ponderomotive phase because having only one slice in memory effectively results in a first order interpolation of the field-particle coupling. While experience has shown that FEL simulations work quite well, the first order accuracy opens the door to two possible ways of speeding up simulation time. First, one can consider higher order algorithms; unfortunately, these methods appear to require all the particle and field data in memory at the same time, and therefore will typically only be important for either small (probably 1D) problems or for parallel simulations run on many processors. Second, one may consistently solving the equations to some low order using faster, simpler algorithms (replacing, for example, the usual RK4). The latter is particularly attractive, although in practice it may be desirable to retain higher order methods when integrating along z. We investigate some of the possibilities.

MOPSO51

Feasibility of an XUV FEL Oscillator at ASTA

FEL, undulator, simulation, cryomodule

88

A.H. Lumpkin
Fermilab, Batavia, USA
H. Freund
LANL, Los Alamos, New Mexico, USA
M.W. Reinsch
LBNL, Berkeley, California, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
A significant opportunity exists at the Advanced Superconducting Test Accelerator (ASTA) facility presently under construction at Fermilab to enable the first XUV free electron laser (FEL) oscillator experiments. The ultrabright beam from the L-band photoinjector will provide sufficient gain to compensate for reduced mirror reflectances in the VUV-XUV regimes, the 3-MHz micropulse repetition rate for 1 ms will support an oscillator configuration, the SCRF linac will provide stable energy, and the eventual GeV-scale energy with three TESLA-type cryomodules will satisfy the FEL resonance condition in the XUV regime. Concepts based on combining such beams with a 5-cm-period undulator and optical resonator cavity for an FEL oscillator are described. We used the 68% reflectances for normal incidence on multilayer metal mirrors developed at LBNL*. Initial simulations using GINGER with an oscillator module and MEDUSA:OPC show saturation for the 13.4-nm case after 300 and 350 passes, respectively,of the 3000 pulses. Initially, VUV experiments could begin in the 180- to 120-nm regime using MgF2-coated Al mirrors with only one cryomodule installed and beam energies of 250-300 MeV.
*LBNL X-ray optics site: http://xdb.lbl.gov/Section4

MOPSO57

Measurement of Wigner Distribution Function for Beam Characterization of FELs

laser, free-electron-laser, FEL, focusing

92

T. Mey, K. Mann, B. Schäfer
LLG, Goettingen, Germany
B. Keitel, S. Kreis, M. Kuhlmann, E. Plönjes, K.I. Tiedtke
DESY, Hamburg, Germany

Free-electron lasers deliver VUV and soft x-ray pulses with the highest brilliance available and high spatial coherence. Users of such facilities have high demands on phase and coherence properties of the beam, for instance when working with coherent diffractive imaging (CDI). To gain highly resolved spatial coherence information, we have performed a caustic scan at BL2 of FLASH using the ellipsoidal beam line focusing mirror and a movable XUV sensitive CCD detector. This measurement allows for retrieving the Wigner distribution function, being the two-dimensional Fourier transform of the mutual intensity of the beam. Computing the reconstruction on a four-dimensional grid, this yields the Wigner distribution which describes the beam propagation completely. Hence, we are able to provide comprehensive information about spatial coherence properties of the FLASH beam including the mutual coherence function and the global degree of coherence. Additionally, we derive the beam propagation parameters such as Rayleigh length, waist diameter and the beam quality factor M².

MOPSO59

The Influence of the Magnetic Field Inhomogeneity on the Spontaneous Radiation and the Gain in the Plane Wiggler

wiggler, laser, undulator, FEL

97

K.B. Oganesyan
ANSL, Yerevan, Armenia

Funding: ISTC
We calculate the spectral distribution of spontaneous emission and the gain of electrons moving in plane wiggler with inhomogeneous magnetic field. We show that electrons do complicated motion consisting of slow(strophotron) and fast(undulator) parts. We average the equations of motion over fast undulator part and obtain equations for connected motion. It is shown, that the account of inhomogenity of the magnetic field leads to appearence of additional peaks in the spectral distribution of spontaneous radiation and the gain.

MOPSO60

Channeled Positrons as a Source of Gamma Radiation

positron, photon, radiation, ion

101

K.B. Oganesyan
ANSL, Yerevan, Armenia

Funding: ISTC
A possibility of channeling of low-energy (5 / 20Mev) relativistic positrons with coaxial symmetry around separate crystal axes of negative ions in some types of crystals, is shown. The annihilation processes of positrons with medium electrons are investigated in details. The lifetime of a positron in the regime of channeling is estimated 〖10〗^-6 sec which on a 〖10〗⁹/〖10〗⁸ times is bigger than at usual cases.

MOPSO61

Modulated Medium for Generation of Transition Radiation

radiation, dipole, lattice, polarization

105

K.B. Oganesyan
ANSL, Yerevan, Armenia

Funding: ISTC
It is shown on an example of amorphous quartz, under the influence of a standing microwave field, at its certain parameters, superlattice is created in the medium where difference in values of dielectric constants of neighboring layers can be up to third order. This superlattice exists during the nanosecond, however it is sufficient for using it as a radiator for generation of transition radiation by relativistic electrons.

MOPSO65

Suppression of Wakefield Induced Energy Spread Inside an Undulator Through Current Shaping

wakefield, undulator, impedance, FEL

108

J. Qiang, C.E. Mitchell
LBNL, Berkeley, California, USA

Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Wakefields from resistive wall and surface roughness inside an undulatory can cause significant growth of beam energy spread and limit the performance of x-ray FEL radiation. In this paper, we propose a method to mitigate such energy modulation by appropriately conditioning the electron beam current profile. Numerical example and potential applications will also be discussed.

MOPSO66

Start-to-end Simulation of a Next Generation Light Source Using the Real Number of Electrons

simulation, FEL, emittance, radiation

112

J. Qiang, J.N. Corlett, P. Emma, C.E. Mitchell, C. F. Papadopoulos, G. Penn, M.W. Reinsch, R.D. Ryne, M. Venturini
LBNL, Berkeley, California, USA
S. Reiche
PSI, Villigen PSI, Switzerland

Funding: This research was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Start-to-end simulation plays an important role in design and optimization of next generation light sources. In this paper, we will present start-to-end (from the photocathode to the end of undulator) simulations of a high repetition rate FEL-based Next Generation Light Source driven by CW superconducting linac with the real number of electrons (~2 billion electrons/bunch) using the multi-physics parallel beam dynamics code IMPACT. We will discuss challenges, numerical methods and physical models used in the simulation. We will also present simulation results of a beam transporting through photoinjector, beam delivery system, and final X-ray FEL radiation.

MOPSO69

Free-Electron Lasers Driven by Laser-Plasma Accelerators Using Decompression or Dispersion

FEL, undulator, plasma, laser

117

C.B. Schroeder, E. Esarey, W. Leemans, J. van Tilborg
LBNL, Berkeley, California, USA
Y. Ding, Z. Huang
SLAC, Menlo Park, California, USA
F.J. Grüner, A.R. Maier
CFEL, Hamburg, Germany

Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Laser-plasma accelerators (LPAs) compactly produce fs beams with kA peak current and low (sub-micron) transverse emittance. Presently, the energy spread (percent-level) hinders the FEL application. Slippage of the fs beam in the FEL also suppresses lasing in the soft-x-ray, and longer, wavelength regimes. Given experimentally demonstrated LPA electron beam parameters, we discuss methods of beam phase space manipulation after the LPA to achieve FEL lasing. Decompression is examined as a solution to reduce the slice energy spread and slippage effects. We present a theoretical analysis of the stretched (and chirped) LPA beam in the FEL and determine the optimal decompression. Dispersion, coupled to a transverse gradient undulator (TGU), is also considered to enable LPA-driven FELs. Using a TGU has the advantages of shorter pulse duration, smaller bandwidth, and wavelength stabilization. We present numerical modeling for SASE and seeded XUV and soft x-ray FELs driven by LPAs after beam manipulation (decompression and/or dispersion). Recent advances in LPA performance will be presented, and experimental plans to demonstrate LPA-driven FEL lasing at LBNL will be discussed.

MOPSO70

Crystal Channeling Acceleration Research for High Energy Linear Collider at ASTA Facility

acceleration, plasma, radiation, laser

122

Y.-M. Shin
Northern Illinois University, DeKalb, Illinois, USA
K. Carlson, M.D. Church, V.D. Shiltsev, D.A. Still
Fermilab, Batavia, USA
J.C. Tobin
UMD, College Park, Maryland, USA

The density of charge carriers in solids is significantly higher than what was considered above in plasma, and correspondingly, the longitudinal fields of up to 10 TV/m are possible. It was suggested that particles are accelerated along major crystallographic directions, which provide a channeling effect in combination with low emittance determined by an Angstrom-scale aperture of the atomic “tubes.” However, the major challenge of this channeling acceleration is that ultimate acceleration gradients might require relativistic intensities at hard x-ray regime (~ 40 keV), exceeding those conceivable for x-rays as of today, though x-ray lasers can efficiently excite solid plasma and accelerate particles inside a crystal channel. However, the acceleration will take place only in a short time before full dissociation of the lattice. Carbon nanotubes have great potential with a wide range of flexibility and superior physical strength, which can be applied to channeling acceleration and possibly fast cooling. This talk will present past and current efforts on crystal acceleration research and discuss feasible experiments with the ASTA and beyond.

MOPSO73

Suface Roughness Wakefield in FEL Undulator

wakefield, impedance, undulator, FEL

127

G.V. Stupakov
SLAC, Menlo Park, California, USA
S. Reiche
PSI, Villigen PSI, Switzerland

Among several wakefield models for the FEL undulator vacuum chamber a simple sinusoidal wall modulation with a small ratio of height to wavelength is especially attractive because of its simplicity [1]. The model neglects a so called resonant mode wakefield and has an (integrable) singularity at the origin which makes difficult its use in practical simulations. In this work we generalize the longitudinal wake of a sinusoidally modulated wall to include the effect of the resonant mode. This also removes the singularity of the wake at the origin. The new wake is used to evaluate the roughness wakefield effect in the undulator of SwissFEL.
[1] G. Stupakov, in "Nonlinear and Collective Phenomena in Beam Physics 1998" Workshop, New York (1999), no. 468 in AIP Conference Proceedings, pp. 334–47.

MOPSO74

Reevaluation of Coherent Electron Cooling Gain Factor

FEL, undulator, hadron, radiation

132

G.V. Stupakov
SLAC, Menlo Park, California, USA
M.S. Zolotorev
LBNL, Berkeley, California, USA

In Ref. [1] the authors put forward a concept of coherent electron cooling of hadrons. At the core of the concept lies the following idea: a density perturbation induced by an hadron in a co-propagating relativistic electron beam is amplified by several orders of magnitude in a free electron laser (FEL). After the FEL the electron beam is merged again with the hadron one and the amplified electric field in the electron beam acts back on each hadron resulting, after many repetitions, in cooling of the hadron beam. The efficiency of the process is critically determined by the amplification factor of the longitudinal electric field induced by the hadron in the electron beam. In this work we show that this factor is actually considerably smaller than the (conventionally defined) FEL gain with the smallness parameter to be the relative bandwidth of the FEL amplifier.
[1] V. N. Litvinenko and Y. S. Derbenev, Phys. Rev. Lett. 102, 114801 (2009).

MOPSO77

Timing Jitter Measurements of the SwissFEL Test Injector

laser, gun, cathode, feedback

140

C. Vicario, B. Beutner, M.C. Divall, C.P. Hauri, S. Hunziker, M.G. Kaiser, M. Luethi, M. Pedrozzi, T. Schietinger
PSI, Villigen PSI, Switzerland
C.P. Hauri
EPFL, Lausanne, Switzerland

To reach nominal bunch compression and FEL performance of SwissFEL with stable beam conditions for the users, less than 40fs relative rms jitter is required from the injector. Phase noise measurement of the gun laser oscillator shows an exceptional 30fs integrated rms jitter. We present these measurements and analyze the contribution to the timing jitter and drift from the rest of the laser chain. These studies were performed at the SwissFEL injector test facility, using the rising edge of the Schottky-scan curve and on the laser system using fast digital signal analyzer and photodiode, revealing a residual jitter of 150fs at the cathode from the pulsed laser amplifier and beam transport, measured at 10Hz. Spectrally resolved cross-correlation technique will also be reviewed here as a future solution of measuring timing jitter at 100Hz directly against the pulsed optical timing link with an expected resolution in the order of 50fs. This device will provide the signal for feedback systems compensating for long term timing drift of the laser for the gun as well as for the pulsed lasers at the experimental stations.

MOPSO81

Broad-band Amplifier Based on Two-stream Instability

FEL, plasma, free-electron-laser, space-charge

144

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

A broadband FEL amplifier is of great interests for short-pulse generation in FEL technology as well as for novel hadron beam cooling technique, such as CeC. We present our founding of a broadband amplification in 1D FEL based on electron beam with two energy peaks and a strong space charge forces. We present the optimization of such amplifier and connect its origin to the two-stream instability in electron plasma. In this work, we study how the two-stream instability affects the FEL process and consider various applications in amplifying short spikes of electron current modulation.

MOPSO84

Numerical Investigations of Transverse Gradient Undulator Based Novel Light Sources

FEL, laser, undulator, simulation

152

T. Zhang, D. Wang, G.L. Wang, H.F. Yao
SINAP, Shanghai, People's Republic of China
J.S. Liu, C. Wang, W.T. Wang, Z.N. Zeng
Shanghai Institute of Optics and Fine Mechanics, Shanghai, People's Republic of China
J.Q. Wang, S.H. Wang
IHEP, Beijing, People's Republic of China

With the stat-of-the-art laser technique, the quality of electron beam generated from laser-plasma accelerator (LPA) is now becoming much more better. The natural merits LPA beam, e.g. high peak current, ultra-low emittance and ultra-short bunch length, etc., pave the way to the novel light sources, especially in the realm of developing much compact X-ray light sources, e.g. table-top X-ray free-electron laser, although the radiation power is limited by the rather larger energy spread than conventional LINAC. Luckily, much more power could be extracted by using the undulator with transverse gradient (TGU) when energy spread effect could be compensated. Here we introduce a novel soft x-ray light source driven by LPA based on TGU technique. Meanwhile we present a simple idea on how to achieve much higher rep-rate (e.g. ~100 kHz) storage ring based FELs boosted by TGU.

TUOANO02

Long-term Stable, Large-scale, Optical Timing Distribution Systems With Sub-femtosecond Timing Stability

laser, polarization, feedback, optics

156

M.Y. Peng, P.T. Callahan, F.X. Kaertner, A.H. Nejadmalayeri
MIT, Cambridge, Massachusetts, USA
K. Ahmed, S. Valente, M. Xin
DESY, Hamburg, Germany
P. Battle, T.D. Roberts
AdvR, Inc., Montana, USA
J.M. Fini, L. Grüner-Nielsen, E. Monberg, M. Yan
OFS Laboratories, New Jersey, USA
F.X. Kaertner
CFEL, Hamburg, Germany

Funding: US Department of Energy Contract DE-SC0005262 and Center for Free-Electron Laser Science, DESY, Hamburg
Sub-fs X-ray pulse generation in kilometer-scale FEL facilities will require sub-fs long-term timing stability between optical sources over kilometer distances. We present here key developments towards a completely fiber-coupled, sub-fs optical timing distribution system. Our approach [*] is to lock a femtosecond pulsed laser to a microwave reference and distribute its pulse train through fiber links stabilized by balanced optical cross-correlators (BOCs) [**]. First, we verified that low-noise optical master oscillators for sub-fs timing distribution are available today; the measured jitter for two commercial femtosecond lasers is less than 70 as for frequencies above 1 kHz. Second, we developed a novel 1.2 km dispersion-compensated, polarization-maintaining fiber link to eliminate drifts induced by polarization mode dispersion. Link stabilization for 16 days showed 0.6 fs RMS timing drift and during a 3-day interval only 0.13 fs drift. Lastly, we fabricated a hybrid-integrated BOC using PPKTP waveguides [***] to eliminate alignment drifts and to reduce the link operation power by a factor of 10-100, which will reduce timing errors induced by fiber nonlinearities.
* J. Kim et al., Nat. Photon., 2, 12, 733–736, 2008.
** J. Kim et al., Opt. Lett., 32, 9, 1044–1046, 2007.
*** A. H. Nejadmalayeri et al., Opt. Lett., 34, 16, 2522–2524, 2009.

Slides TUOANO02 [1.387 MB]

TUOANO04

PITZ Experience on the Experimental Optimization of the RF Photo Injector for the European XFEL

emittance, laser, cathode, brightness

160

M. Krasilnikov, H.-J. Grabosch, M. Groß, L. Hakobyan, I.I. Isaev, L. Jachmann, M. Khojoyan, W. Köhler, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, A. Shapovalov, F. Stephan, G. Vashchenko, S. Weidinger, R.W. Wenndorff
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
K. Flöttmann, M. Hoffmann, G. Klemz, S. Lederer, H. Schlarb, S. Schreiber
DESY, Hamburg, Germany
Ye. Ivanisenko
PSI, Villigen PSI, Switzerland
M.A. Nozdrin
JINR, Dubna, Moscow Region, Russia
V.V. Paramonov
RAS/INR, Moscow, Russia
D. Richter
HZB, Berlin, Germany
S. Rimjaem
Chiang Mai University, Chiang Mai, Thailand
I.H. Templin, I. Will
MBI, Berlin, Germany

The Photo Injector Test facility at DESY, Zeuthen site (PITZ), develops high brightness electron sources for modern free electron lasers. A continuous experimental optimization of the L-band photo injector for such FEL facilities like FLASH and the European XFEL has been performed for a wide range of electron bunch charges – from 20 pC to 2 nC – yielding very small emittance values for all charge levels. Experience and results of the experimental optimization will be presented in comparison with beam dynamics simulations. The influence of various parameters onto the photo injector performance will be discussed.
Phys. Rev. ST Accel. Beams 15, 100701 (2012)

Slides TUOANO04 [3.126 MB]

TUOBNO03

An RF Deflecting Cavity Based Spreader System for Next Generation Light Sources

gun, FEL, cavity, dipole

173

C. Sun, L.R. Doolittle, P. Emma, J.-Y. Jung, M. Placidi, A. Ratti
LBNL, Berkeley, California, USA

Lawrence Berkeley National Laboratory (LBNL) is developing design concepts for a multi-beamline (up to 10 lines) soft x-ray FEL array powered by a superconducting linear accelerator with a high bunch repetition rate of approximately one MHz. The FEL array requires a beam spreader system which can distribute individual electron bunches from the linac to each independently configurable beamline. We propose a new spreader system using RF deflecting cavities to deflect electron bunches as an alternative design to the fast kicker scheme. This RF approach offers more stable deflection amplitude while removing the limitations on the bunch repetition rate characteristic of the kicker approach. In this work, we describes the design concept of this RF based spreader system, including technical choices, design parameters and beamline optics.
[1] M. Placidi et al., Proceedings of IPAC2012, New Orleans, Louisiana, USA, pp.1765-1767

Slides TUOBNO03 [1.391 MB]

TUICNO01

Progress in SRF Guns

gun, SRF, cavity, cathode

176

S.A. Belomestnykh
BNL, Upton, Long Island, New York, USA

Funding: Work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE
In the last couple of years great progress has been made in the commissioning and operation of SRF electron beam sources. Both elliptical cavity designs and reentrant cavities have been developed. This talk will review recent progress in SRF guns.

Slides TUICNO01 [12.748 MB]

TUOCNO01

Electron Beam Longitudinal Phase Space Manipulation by Means of an AD-HOC Photoinjector Laser Pulse Shaping

linac, FEL, laser, simulation

180

G. Penco, D. Castronovo, M.B. Danailov, G. De Ninno, A.A. Demidovich, S. Di Mitri, W.M. Fawley, L. Giannessi, C. Spezzani, M. Trovò
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

In a seeded FEL machine as FERMI, the interplay between the electrons energy curvature and the seed laser frequency chirp has a relevant impact on the output FEL spectrum. It is therefore crucial controlling and manipulating the electron beam longitudinal phase space at the undulator entrance. In case of very short bunches, i.e. high compression scheme, the longitudinal wakefields generated in the linac induce a positive quadratic curvature in the electrons longitudinal phase space that is hard to compensate by tuning the phase of the main RF sections or the possible high harmonic cavity. At FERMI we have experimentally exploited a longitudinal ramp current distribution at the cathode, obtained with an ad-hoc photoinjector laser pulse shaping, to linearize the longitudinal wakefields in the downstream linac and flatten the electrons energy distribution, as theoretical foreseen in [1]. Longitudinal phase space measurements in this novel configuration are here presented, providing a comparison with the typical longitudinal flat-top profile.
[1] Phys. Rev. Special Topics - Accel. and Beams 9 (12), 120701 (2006)

Slides TUOCNO01 [28.792 MB]

TUOCNO04

Feasibility of CW and LP Operation of the XFEL Linac

cryomodule, linac, HOM, cavity

189

J.K. Sekutowicz, V. Ayvazyan, J. Branlard, M. Ebert, J. Eschke, T. Feldmann, A. Gössel, D. Kostin, I.M. Kudla, W. Merz, F. Mittag, C. Müller, R. Onken, I. Sandvoss, E. Schneidmiller, A.A. Sulimov, M.V. Yurkov
DESY, Hamburg, Germany
W. Cichalewski, A. Piotrowski, K.P. Przygoda
TUL-DMCS, Łódź, Poland
K. Czuba
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
W. Jałmużna
Embedded Integrated Control Systems GmbH, Hamburg, Germany
J. Szewiński
NCBJ, Świerk/Otwock, Poland

The European XFEL superconducting linac is based on cavities and cryomodules (CM) developed for TESLA linear collider. The XFEL linac will operate nominally in short pulse (sp) mode with 1.3 ms RF pulses (650 μs rise time and 650 μs long bunch train). For 240 ns bunch spacing and 10 Hz RF-pulse repetition rate, up to 27000 bunches per second can be accelerated to 17.5 GeV to generate uniquely high average brilliance photon beams at very short wavelengths. While many experiments can take advantage of full bunch trains, others prefer an increased to several μ-seconds intra-pulse distance between bunches, or short bursts with a kHz repetition rate. For these types of experiments, the high average brilliance can be preserved only with duty factors much larger than that of the currently proposed sp operation. In this contribution, we discuss progress in the R&D program for future upgrade of the European XFEL linac, namely an operation in the continuous wave (cw) and long pulse (lp) mode, which will allow for more flexibility in the electron and photon beam time structure.

Slides TUOCNO04 [8.910 MB]

TUOCNO05

Design Concepts for a Next Generation Light Source at LBNL

FEL, linac, laser, undulator

193

J.N. Corlett, A.P. Allezy, D. Arbelaez, K.M. Baptiste, J.M. Byrd, C.S. Daniels, S. De Santis, W.W. Delp, P. Denes, R.J. Donahue, L.R. Doolittle, P. Emma, D. Filippetto, J.G. Floyd, J.P. Harkins, G. Huang, J.-Y. Jung, D. Li, T.P. Lou, T.H. Luo, G. Marcus, M.T. Monroy, H. Nishimura, H.A. Padmore, C. F. Papadopoulos, G.C. Pappas, S. Paret, G. Penn, M. Placidi, S. Prestemon, D. Prosnitz, H.J. Qian, J. Qiang, A. Ratti, M.W. Reinsch, D. Robin, F. Sannibale, R.W. Schoenlein, C. Serrano, J.W. Staples, C. Steier, C. Sun, M. Venturini, W.L. Waldron, W. Wan, T. Warwick, R.P. Wells, R.B. Wilcox, S. Zimmermann, M.S. Zolotorev
LBNL, Berkeley, California, USA
C. Adolphsen, K.L.F. Bane, Y. Ding, Z. Huang, C.D. Nantista, C.-K. Ng, H.-D. Nuhn, C.H. Rivetta, G.V. Stupakov
SLAC, Menlo Park, California, USA
D. Arenius, G. Neil, T. Powers, J.P. Preble
JLAB, Newport News, Virginia, USA
C.M. Ginsburg, R.D. Kephart, A.L. Klebaner, T.J. Peterson, A.I. Sukhanov
Fermilab, Batavia, USA

Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
The NGLS collaboration is developing design concepts for a multi-beamline soft x-ray FEL array powered by a superconducting linear accelerator, operating with a high bunch repetition rate of approximately 1 MHz. The CW superconducting linear accelerator design is based on developments of TESLA and ILC technology, and is supplied by an injector based on a high-brightness, high-repetition-rate photocathode electron gun. Electron bunches from the linac are distributed by RF deflecting cavities to the array of independently configurable FEL beamlines with nominal bunch rates of ~100 kHz in each FEL, with uniform pulse spacing, and some FELs capable of operating at the full linac bunch rate. Individual FELs may be configured for different modes of operation, including self-seeded and external-laser-seeded, and each may produce high peak and average brightness x-rays with a flexible pulse format, and with pulse durations ranging from femtoseconds and shorter, to hundreds of femtoseconds. In this paper we describe current design concepts, and progress in R&D activities.

Slides TUOCNO05 [5.982 MB]

TUPSO18

Optimization of Dielectric Loaded Metal Waveguides for Acceleration of Electron Bunches using Short THz Pulses

acceleration, space-charge, laser, emittance

250

A. Fallahi, F.X. Kaertner
CFEL, Hamburg, Germany
F.X. Kaertner, A. Sell, L.J. Wong
MIT, Cambridge, Massachusetts, USA

Funding: DARPA contract number N66001-11-1-4192 and the Center for Free-Electron Laser Science, DESY Hamburg
The last decade has witnessed extensive research efforts to reduce the size of charged particle accelerators to achieve compact devices for providing relativistic particles. To this end, various methods such as laser plasma and dielectric wakefield acceleration are investigated and their pros and cons are studied. With the advent of efficient THz generation techniques based on optical rectification, THz waveguides are also considered to be proper candidates for compact accelerators. Sofar, the proposed schemes toward high power THz generation are capable of producing short pulses, which dictates the study of particle acceleration in the pulsed regime rather than continuous-wave regime. Therefore, THz waveguides are more suitable than cavities for the considered purpose*. Consequently, various effects such as group velocity mismatch and group velocity dispersion start to influence the acceleration scenario and impose limits on the maximum energy gain from the pulse. In this contribution, we investigate electron bunch acceleration and compression in dielectrically loaded metal waveguides for the THz wavelength range and present design methodologies to optimize their performance.
* Liang Jie Wong, Arya Fallahi, and Franz X. Kärtner. "Compact electron acceleration and bunch compression in THz waveguides." Optics Express 21, no. 8 (2013): 9792-9806.

TUPSO19

The Photocathode Laser System for the APEX High Repetition Rate Photoinjector

laser, cathode, controls, feedback

255

D. Filippetto, L.R. Doolittle, G. Huang, G. Marcus, H.J. Qian, F. Sannibale
LBNL, Berkeley, California, USA

Funding: DOE grants No. DE-AC02-05CH11231.
The APEX injector has been built and commissioned at LBNL. A CW-RF Gun accelerates electron bunches to up 750 keV at MHz repetition rate. Different high efficiency photocathodes with different work functions are being tested with the help of a load lock system. The photocathode drive laser is thus conceived to provide up to 40 nJ per pulse in the UV and 200 nJ per pulse in the green at 1 MHz, with transverse and longitudinal shaping (flat top, up to 60 ps) for electron beam creation. A transfer line of about 15 meters has been designed and optimized for minimal jitters. Remote control of repetition rate, energy and position have been implemented on the system, together with offline and online diagnostic for beam monitoring. Here we present the laser system setup as well as the first measurements on longitudinal pulse shaping and jitter characterization.

TUPSO22

Status of SwissFEL Undulator Lines

undulator, quadrupole, dipole, alignment

263

R. Ganter, M. Aiba, H.-H. Braun, M. Calvi, P. Heimgartner, G. Janzi, H. Jöhri, R. Kobler, F. Löhl, M. Negrazus, L. Patthey, E. Prat, S. Reiche, S. Sanfilippo, U. Schaer, T. Schmidt, L. Schulz, V. Vranković, J. Wickstroem
PSI, Villigen PSI, Switzerland

An overview of the Aramis Hard-X ray FEL line of SwissFEL is presented, showing its future integration in the tunnel as well as the space reservation for possible future upgrades: Athos Soft X-ray FEL line, post-undulator deflecting cavities. The design of the FEL components like the energy collimator, the matching sections or the dog leg transfer line linking the linac to the future Athos line are almost completed. The characterization of the in-vacuum undulator prototype is described in a companion paper. The installation of the components will start in spring 2015 while the first photons are planned for December 2016 with the alignment and adjustment of the undulators foreseen for first SASE operation by spring 2017 .

TUPSO24

Dispersion Based Beam Tilt Correction

quadrupole, FEL, sextupole, emittance

267

M.W. Guetg, B. Beutner, E. Prat, S. Reiche
PSI, Villigen PSI, Switzerland

In Free Electron Lasers (FEL), a transverse centroid misalignment of longitudinal slices in an electron bunch reduces the effective overlap between radiation field and electron bunch and therefore the FEL performance. The dominant sources of slice misalignments for FELs are the incoherent and coherent synchrotron radiation within bunch compressors as well as transverse wake fields in the accelerating cavities. This is of particular importance for over-compression which is required for one of the key operation modes for the SwissFEL planned at the Paul Scherrer Institute. The centroid shift is corrected using corrector magnets in dispersive sections, e.g. the bunch compressors. First and second order corrections are achieved by pairs of sextupole and quadrupole magnets in the horizontal plane while skew quadrupoles correct to first order in the vertical plane. Simulations and measurements at the SwissFEL Injector Test Facility are done to investigate the proposed correction scheme for SwissFEL. This paper presents the methods and results obtained.

TUPSO25

Status of the EU-XFELl Laser Heater

laser, vacuum, undulator, alignment

271

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

Funding: This work was supported by the Swedish Research Council under contract number DNR-828-2008-1093.
We describe the technical layout and the status of the laser heater system for the EuXFEL. The laser heater is needed to increase the momentum spread of the electron beam to prevent micro-bunching instabilities in the linac.

TUPSO27

Design for a Fast, XFEL-Quality Wire Scanner

photon, radiation, vacuum, instrumentation

276

M.A. Harrison, R.B. Agustsson, T.J. Campese, P.S. Chang, A.Y. Murokh, M. Ruelas
RadiaBeam, Santa Monica, USA

RadiaBeam Technologies has designed and manufactured a new wire scanner for high-speed emittance measurements of XFEL-type beams of energy 139 MeV. Using three 25-micron thick tungsten wires, this wire scanner measures vertical and horizontal beam size as well as transverse spatial correlation in one pass. The intensity of the beam at a wire position is determined from emitted bremsstrahlung photons as measured by a BGO scintillator system. The wires are transported on a two-ended support structure moved by a ball-screw linear stage. The double-ended structure reduces vibrations in the wire holder, and the two-bellows design negates the effects of air pressure on the motion. The expected minimum beam size measurable by this system is on the order of 10 microns with 0.1-micron accuracy. To achieve this, new algorithms are presented that reduce the effect of the non-zero thickness of the wire on the wire scan output. In addition, novel calculations are presented for determining the elliptical geometric parameters (vertical and horizontal beam size and correlation, or alternatively, the axis lengths and rotation) of the beam from the wire scanner measurements.

TUPSO28

Development of Photocathode RF-gun at PAL

gun, laser, emittance, coupling

279

J.H. Hong, J.H. Han, H.-S. Kang, Y.W. Parc, S.J. Park, Y.J. Park
PAL, Pohang, Kyungbuk, Republic of Korea
I.S. Ko
POSTECH, Pohang, Kyungbuk, Republic of Korea

We are developing two types of S-band photocathode RF-guns for the X-ray free electron laser (XFEL) at Pohang Accelerator Laboratory (PAL). One is a 1.6-cell RF-gun with a dual side coupler and two pumping ports. This RF-gun is similar to the earlier guns developed at PAL. The other one is a 1.5-cell RF-gun with a coaxial coupler and a cathode preparation system. This RF-gun is similar to the DESY-type L-band RF-gun. We have designed and fabricated two types of RF-guns. In this paper we introduce and compare two different RF-guns.

TUPSO32

Project of the Short Pulse Facility at KAERI

quadrupole, gun, kicker, bunching

287

N. Vinokurov, S.V. Miginsky
BINP SB RAS, Novosibirsk, Russia
S. Bae, B.A. Gudkov, B. Han, K.H. Jang, Y.U. Jeong, H.W. Kim, K. Lee, S.V. Miginsky, J. Mun, S. H. Park, G.I. Shim, N. Vinokurov
KAERI, Daejon, Republic of Korea
N. Vinokurov
NSU, Novosibirsk, Russia

Funding: This work is supported by the WCI Program of the National Research Foundation of Korea funded by the Ministry of Education, Science, and Technology of Korea (NRF Grant No. WCI 2011-001).
The low-energy electron accelerator with subpicosecond electron bunches is under construction at Korea Atomic Energy Research Institute (KAERI). It will serve as the user facility for high-energy ultrafast electron difraction and synchronized high-power terahertz pulse and short x-ray pulse generation. The accelerator consists of RF gun with photocathode and 20-MeV linac. The bunching of accelerated beam is achieved in the ninety-degree achromatic bend. After that fast kicker deflects some of bunches to the target for x-ray generation, other bunches come to terahertz radiator (undulator or multifoil). Bunches from the RF gun are also planned to use for ultrafast electron difraction. Some detailes of the design, current status of the project and future plans are described.

TUPSO33

The Commissioning of Tess: An Experimental Facility for Measuring the Electron Energy Distribution From Photocathodes

cathode, laser, brightness, vacuum

290

L.B. Jones, R.J. Cash, B.D. Fell, K.J. Middleman, B.L. Militsyn, T.C.Q. Noakes
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
D.V. Gorshkov, H.E. Scheibler, A.S. Terekhov
ISP, Novosibirsk, Russia

ASTeC have developed a Transverse Energy Spread Spectrometer (TESS) – an experimental facility to characterise the energy distribution of electrons emitted by a photocathode. Electron injector brightness is fundamentally limited by the width of this distribution or energy spread, and brightness will be increased significantly by reducing the longitudinal and transverse energy spread at source. TESS supports photocathode performance measurements at room and LN2-temperature under illumination from a range of fixed- and variable-wavelength light sources, allowing characterisation of both metal and semiconductor photocathodes. Preliminary work with GaAs* has shown that electron energy spread is dependent on the quantum efficiency (Q.E.) of the photocathode source, and TESS includes a piezo-electric leak valve to allow controlled degradation of the photocathode Q.E. whilst monitoring the energy spread of emitted electrons. This system offers huge potential to support future photocathode R&D work into a range of photocathode materials. Using GaAs photocathodes activated to high levels of Q.E. in our photocathode preparation facility**, we present commissioning results for TESS.
* Proc. IPAC ’12, TUPPD067, 1557-1559
** Proc. IPAC ’11, THPC129, 3185-3187

TUPSO35

The MAX IV Linac as X-Ray FEL Injector: Comparison of Two Compression Schemes

linac, emittance, wakefield, FEL

294

O. Karlberg, F. Curbis, S. Thorin, S. Werin
MAX-lab, Lund, Sweden

The MAX IV linac will be used for injections and top up of two storage rings and at the same time provide a high brightness pulses to a short pulse facility (SPF) and an X-ray FEL (phase 2). Compression in the linac is done in two double achromats which implies a positive R56 unlike the commonly used chicane compressor scheme with negative R56. Compression using the achromats scheme requires the electron bunch to be accelerated on a falling RF slope resulting in an energy chirp that longitudinal wakefields will boost along the linac. This permits a stronger compression. In this proceeding we will present how the longitudinal wakefields interact with the bunch compression in the double achromat scheme compared with the chicane compression case. Focus is brought on how the unique MAX IV linac lattice is fully capable to cope with the high demands of an FEL injector. The charge related electron beam jitter in both set-ups will also be investigated.

TUPSO36

Beam Dynamics Optimization for the High Brightness PITZ Photo Injector Using 3D Ellipsoidal Cathode Laser Pulses

laser, emittance, cathode, simulation

298

M. Khojoyan, M. Krasilnikov, F. Stephan, G. Vashchenko
DESY Zeuthen, Zeuthen, Germany

Funding: The work is funded by the German Federal Ministry of education and Research, project 05K10CHE “Development and experimental test of a laser system for producing quasi 3D ellipsoidal laser pulses”.
The Photo Injector Test facility at DESY, Zeuthen Site (PITZ) is one of the leading producers of high brightness electron beams for linac based Free Electron Lasers (FELs) with a specific focus on the requirements of FLASH and the European XFEL. The main activities at PITZ are devoted to the detailed characterization and optimization of electron sources yielding to an extremely small transverse beam emittance. The cathode laser pulse shaping is considered as one of the key issues for the high brightness photo injector. Beam dynamics simulations show that the injector performance could be further improved by replacing the typical cylindrically shaped PITZ bunches by uniformly filled 3D ellipsoidal shaped electron beams. A set of numerical simulations were performed to study the beam dynamics of uniformly filled 3D ellipsoidal bunches with 1 nC charge in order to find an optimum PITZ machine setup which will yield the best transverse emittance. Simulation results comparing both options of cylindrical and 3D ellipsoidal beams are also presented and discussed.

TUPSO39

Development of a Photo Cathode Laser System for Quasi Ellipsoidal Bunches at PITZ

laser, diagnostics, polarization, cathode

303

M. Krasilnikov, M. Khojoyan, F. Stephan
DESY Zeuthen, Zeuthen, Germany
A. Andrianov, E. Gacheva, E. Khazanov, S. Mironov, A. Poteomkin, V. Zelenogorsky
IAP/RAS, Nizhny Novgorod, Russia
E. Syresin
JINR, Dubna, Moscow Region, Russia

Funding: The work is funded by the German Federal Ministry of education and Research, project 05K10CHE “Development and experimental test of a laser system for producing quasi 3D ellipsoidal laser pulses”.
Cathode laser pulse shaping is one of the key issues for high brightness photo injector optimization. A flat-top temporal profile of the cylindrical pulses reduces significantly the transverse emittance of space charge dominated beams. As a next step towards further improvement in photo injector performance a 3D pulse shaping is considered. An ellipsoid with uniform photon density is the goal of studies in the frame of a Joint German-Russian Research Group, including the Institute of Applied Physics (Nizhny Novgorod), Joint Institute of Nuclear Research (Dubna) and the Photo Injector test facility at DESY, Zeuthen site (PITZ). The major purpose of the project is the development of a laser system capable of producing 3D quasi ellipsoidal bunches and supporting a bunch train structure close to the European XFEL specifications. The laser pulse shaping is realized using the spatial light modulator technique. The laser pulse shape diagnostics based on a cross-correlator is under development as well. Experimental tests of the new laser system with electron beam production are foreseen at PITZ. First results on the quasi ellipsoidal laser pulse shaping will be reported.

TUPSO41

The Ultrashort Beam Linac System and Proposed Coherent THz Radiation Sources at NSRRC

radiation, linac, gun, undulator

309

W.K. Lau, A.P. Lee
NSRRC, Hsinchu, Taiwan
N.Y. Huang, Z.Y. Wei
NTHU, Hsinchu, Taiwan

The NSRRC ultrashort beam facility is a low energy linac system which is being built to produce femtosecond electron beam for novel light source development. Experiments on prebunched THz FEL and inverse Compton scattering x-ray source are under study. The electron source is a 2998 MHz, 1.5-cell thermionic rf gun with uneven full-cell to half-cell field ratio that is optimized to produce a energy-chirped electron beam. With movable slits in its vacuum vessel, the alpha magnet system is served also as a beam selector. Further bunch compression is done by velocity bunching in the rf linac. Recent progress of the construction of this facility as well as the design study of a prebunched THz FEL with this ultrashort electron beam will be reported.

TUPSO42

Shimming Strategy for the Phase Shifters Used in the European XFEL

simulation, undulator, laser, target

313

Y. Li, J. Pflüger, F. Wolff-Fabris
XFEL. EU, Hamburg, Germany
H.H. Lu, Y.F. Yang
IHEP, Beijing, People's Republic of China

The undulator systems of the European XFEL need a total of 91 Phase Shifters. The 1st field integral of these devices must not exceed 0.004Tmm for working gaps > 16mm. For smaller gaps it is slightly released. In spite of the highly magnetically symmetric design and considerable effort such as the selection and sorting of the magnets small 1st field integral errors cannot be excluded. In this paper a strategy is studied to correct small gap dependent kicking errors as expected for the phase shifters of the XFEL. EU.by using shims of different geometries and sizes. It is found, that small gap dependent kicking errors can well be corrected for using this method. This is a systematic effort to provide effective fast tuning methods, which can be applied for the mass production. The meaning of shim signature will be explained in this paper. The method is demonstrated by simulations and measurements.

TUPSO45

Initial Streak Camera Measurements of the S-band Linac Beam for the University of Hawaii FEL Oscillator

FEL, linac, undulator, radiation

325

A.H. Lumpkin
Fermilab, Batavia, USA
M.R. Hadmack, J.M.D. Kowalczyk, J. Madey, E.B. Szarmes
University of Hawaii, Honolulu, HI, USA

Funding: Work at Fermilab supported by Fermi Research Alliance, LLC under U.S.DOE Contract No.DE-AC02-07CH11359. Work at UH supported by U.S. Dept. of Homeland Security grant No. 20120-DN-077-AR1045-02.
The S-band linac driven Mark V free-electron laser oscillator (FELO) at the University of Hawai‘i operates in the mid-IR at electron beam energies of 40-45 MeV with a four microsecond macropulse length. Recently investigations of the electron beam micropulse bunch length and phase as a function of macropulse time became of interest for potentially optimizing the FELO performance. These studies involved the implementation of a Hamamatsu C5680 streak camera with dual sweep capabilities and the transport of optical transition radiation (OTR) generated at an upstream Cu mirror and of coherent spontaneous emission radiation (CSER) generated in the undulator to the streak camera location outside of the linac tunnel. Both a fast single-sweep vertical unit and a synchroscan unit tuned to 119.0 MHz were used. Initial results include measurements of the individual CSER (on the FEL7th harmonic at 652 nm) micropulse bunch lengths (3 to 5 ps FWHM), the CSER signal intensity variation along macropulse time, and a detected phase slew of 4 ps over the last 700 ns of the macropulse. Complementary OTR measurements are also being evaluated and will be presented as available.

TUPSO46

Analysis and Measurement of Focusing Effects in a Traveling Wave Linear Accelerator

quadrupole, acceleration, focusing, simulation

329

H. Maesaka, T. Asaka, H. Ego, T. Hara, T. Inagaki, Y. Otake, T. Sakurai, H. Tanaka, K. Togawa
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

We propose a further precise model of the transverse dynamics in a traveling wave linear accelerator (TWA) and report experimental results to demonstrate the validity of the model. In SACLA, the beam orbit is calculated by using a transfer matrix based on the transverse dynamics model of each component and the matrix is utilized for orbit stabilization, beam envelop matching etc. For the TWA part, a transfer matrix including an emittance damping effect and an edge focusing effect [*] is employed. However, the beam orbit measured by rf cavity beam position monitors (RF-BPM) [**] did not agree with the calculated orbit, especially for the off-crest acceleration part. Therefore, focusing effects in a TWA structure were analyzed by using a 3-dimensional rf simulation code. The analysis indicated that the transverse dynamics model of the TWA should include an additional quadrupole edge focusing effect. The amount of the additional focusing effect of the TWA was measured in SACLA and the rf simulation result was confirmed to be consistent with the measurement. After the modification of the transverse dynamics model, the beam orbit measured by RF-BPM agrees with the calculation.
* T. Hara et al., Nucl. Instrum. Methods A 624, 65 (2010).
** H. Maesaka et al., Nucl. Instrum. Methods A 696, 66 (2012).

TUPSO47

First Results of a Longitudinal Phase Space Tomography at PITZ

booster, gun, laser, emittance

334

D. Malyutin, M. Groß, I.I. Isaev, M. Khojoyan, G. Kourkafas, M. Krasilnikov, B. Marchetti, F. Stephan, G. Vashchenko
DESY Zeuthen, Zeuthen, Germany

The Photo Injector Test facility at DESY, Zeuthen Site (PITZ), was established as a test stand of the electron source for FLASH and the European X-ray Free Electron Laser (XFEL). One of the tasks at PITZ is the detailed characterization of longitudinal properties of the produced electron bunches. The measurements of the electron bunch longitudinal phase space can be done by tomographic methods using measurements of the momentum spectra by varying the electron bunch energy chirp. At PITZ the energy chirp of the electron bunch can be changed by varying the RF phase of the accelerating structure downstream the gun. The resulting momentum distribution can be measured in a dispersive section installed downstream the accelerating structure. The idea of the measurement and the tomographic reconstruction technique is described in this paper. The setup and first measurement results of the bunch longitudinal phase space measurements using the tomographic technique for several electron bunch charges, including 20 pC, 100 pC and 1 nC, are presented as well.

TUPSO50

Numerical Study on Electron Beam Properties in Triode Type Thermionic RF Gun

cavity, gun, cathode, FEL

344

M. Mishima, M. Inukai, T. Kii, K. Masuda, H. Negm, H. Ohgaki, K. Okumura, M. Omer, K. Torgasin, K. Yoshida, H. Zen
Kyoto University, Institute for Advanced Energy, Kyoto, Japan

The KU-FEL(Kyoto University- Free Electron Laser) facility uses a thermionic 4.5 cell S-band RF gun for electron beam generation because of such advantages over photocathode rf guns as lower cost, higher average current, longer cathode lifetime, and less vacuum requirement. The main disadvantage of using a thermionic RF gun is the back bombardment effect, which causes energy drop in macro pulse of FEL. A triode structure for RF gun was designed in order to minimize the inherent back-bombardment effect. The 2D-simulation has shown significant reduction of back-bombardment power, longitudinal emittance, and an increase of peak current*. A coaxial RF cavity was fabricated based on the design for modification of the existing RF gun to a triode type one. The coaxial RF cavity is equipped with gasket tuning system in order to adjust the cavity resonance frequency**. However the frequency adjustment by variation of gasket thickness changes the coaxial cavity geometry and might affect the predicted beam optics. Another parameter influencing beam optics is the position of thermionic cathode to be installed in the coaxial cavity, which might vary due to misalignment.
*K. Masuda, et al., Proceedings of FEL 2009, Liverpool, Pages 281-284 (2009).
**K. Torgasin, et al., Proceedings of FEL 2012, Nara(2012).

TUPSO54

Undulators for Free Electron Lasers

undulator, focusing, insertion, insertion-device

351

C.W. Ostenfeld, M. Pedersen
Danfysik A/S, Taastrup, Denmark

Danfysik has produced insertion devices for the FEL community for almost 10 years. In this poster, we describe two recent undulator deliveries: a 2.8 m long undulator for the FELIX free electron laser, and a 4.5 m device for the FLARE project, both at Radboud University in Nijmegen, in the Netherlands. The device for FELIX is a 2.8 m PPM device, with a peak field of 0.483 T, and a minimum gap of 22 mm. The device for FLARE, is a 4.5 m hybrid device, with special poles, which allow for double focusing. For both devices, we describe the magnetic modelling, and the magnetic performance.

TUPSO55

300 mm Electromagnetic Wiggler for ELBE

wiggler, insertion, insertion-device, vacuum

353

C.W. Ostenfeld, M. Pedersen
Danfysik A/S, Taastrup, Denmark

Danfysik has designed and built a 300 mm fixed-gap electromagnetic wiggler for the ELBE radiation source at Helmholz Zentrum Dresden Rossendorff. This wiggler will serve as a source of narrow-band THz radiation in the 100 μm to 10 mm range. Due to careful magnetic modelling, and an effective shimming process, we were able to deliver magnetic performance at a high level. We present the details of the modelling, as well as magnetic results.

TUPSO57

Generation of Ultrafast, High-brightness Electron Beams

gun, cathode, cavity, brightness

355

J.H. Park, H. Bluem, J. Rathke, T. Schultheiss, A.M.M. Todd
AES, Princeton, New Jersey, USA

Funding: This work was supported by the U.S. Department of Energy, under Contract No. DE-SC0009556.
The production and preservation of ultrafast, high-brightness electron beams is a major R&D challenge for free electron laser (FEL) and ultrafast electron diffraction (UED) because transverse and longitudinal space charge forces drive emittance dilution and bunch lengthening in such beams. Several approaches, such as velocity bunching and magnetic compression, have been considered to solve this problem but each has drawbacks. We present a concept that uses radial bunch compression in an X-band photocathode radio frequency electron gun. By compensating for the path length differential with a curved cathode in an extremely high acceleration gradient cavity, we have demonstrated numerically the possibility of achieving more than an order of magnitude increase in beam brightness over existing electron guns. The initial thermo-structural analysis and mechanical conceptual design of this electron source are presented.

TUPSO58

Developments of a High-average-current Thermionic RF Gun for ERLs and FELs

gun, cavity, cathode, FEL

359

J.H. Park, H. Bluem, J. Rathke, T. Schultheiss, A.M.M. Todd
AES, Princeton, New Jersey, USA

Funding: Supported by ONR under Contract No. N00014-10-C-0191.
The development of a high-average-current thermionic RF gun with the required beam performance for lasing would provide significant cost of ownership and reliability gains for high-average-power energy recovery linac (ERL) and free electron laser (FEL) devices. The beam for these applications requires high quality and high performance, specifically: low transverse emittance, short pulse duration and high average current. We are developing a gridded thermionic cathode embedded in a copper one-and-half cell UHF cavity to generate the electron beam. The fundamental RF and higher harmonics are combined on the grid and a gated DC voltage controls the beam emission from the cathode. Simulations indicate that short pulse ~ 10 psec, < 1 MeV electron beams with low-emittance ~ 15 mm-mrad at currents ≥ 100 mA can be generated. The elimination of sensitive photocathodes and their drive laser systems would provide significant capital cost saving, improved reliability and uptime due to increased robustness and hence operating and lifecycle cost savings as well. We will present the gun design and performance simulations and the progress achieved to date in optimizing the device.

TUPSO59

Study of a Photocathode-based Microtron using a PIC Code

microtron, laser, acceleration, injection

363

S. Park
Kyungpook National University, Daegu, Republic of Korea
K.H. Jang, Y.U. Jeong, S. H. Park, N. Vinokurov
KAERI, Daejon, Republic of Korea
E.-S. Kim
KNU, Deagu, Republic of Korea
N. Vinokurov
BINP SB RAS, Novosibirsk, Russia

Korea Atomic Energy Research Institute (KAERI) has used thermionic cathode-based microtron accelerator for operating compact THz FEL due to its compact size and high energy resolution. In this thermionic cathode-based microtron, rightly phased electron bunch train are automatically accelerated during the RF macro-pulse over threshold power for their emission. But, the thermionic cathode should be replaced with a photocathode for applying the microtron to UED or THz/X-ray pump prove experiment requiring femto-second and high peak current. But, it is needed to analyze precisely the electron beam dynamics in a microtron, especially, the relation between the RF phase in a microtron cavity and Laser input time for adapting the photocathode to a microtron. Hence, we conduct computer simulation with 3D PIC-code to find those optimized conditions for operating photocathode-based microtron.

TUPSO60

Status of the Undulator Systems for the European X-ray Free Electron Laser

undulator, controls, laser, FEL

367

J. Pflüger, M. Bagha-Shanjani, A. Beckmann, K.H. Berndgen, P. Biermordt, G. Deron, U. Englisch, S. Karabekyan, B. Ketenoğlu, M. Knoll, Y. Li, F. Wolff-Fabris, M. Yakopov
XFEL. EU, Hamburg, Germany

The three undulator systems for the European XFEL consist of a total of 91 Undulator Cells. Each cell consists of an Undulator Segment and an intersection. They will be operational by end of 2015. The serial production of the 91 Undulator Segments is a great challenge and without precedence. It is now in full swing. This contribution gives an overview over the most important design aspects as well as the experience and strategy with the serial production. Representative results of magnetic performance are given. The status of the other system components is briefly described.

TUPSO62

Status of the Planar Undulator Applied in HUST THz-FEL Oscillator

undulator, FEL, radiation, focusing

372

B. Qin, X. Lei, K.F. Liu, X. Liu, P. Tan, Y.Q. Xiong, J. Yang, L. Yang
HUST, Wuhan, People's Republic of China
Y.B. Wang
Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People's Republic of China

To fulfill the physical requirement of a 50-100 um Free Electron Laser (FEL) oscillator, design considerations of a planar undulator are described. Some technical issues, including the tolerances study, the beam match, the field measurement setup and the influence on the magnetic field by the waveguide are discussed as well.

TUPSO63

High Average Brightness Photocathode Development for FEL Applications

cathode, gun, laser, SRF

376

T. Rao, I. Ben-Zvi, J. Skaritka, E. Wang
BNL, Upton, Long Island, New York, USA

Next generation, high average flux, light sources call for electron beams with high average current as well as high peak brightness. Alkali antimonide cathodes, especially K2CsSb show great promise in delivering electron beams to meet these requirements. In the past few years, there have been a number of experiments geared towards understanding the stoichiometry, crystalline structure, surface properties and sensitivity of these cathodes. At BNL, we have used the x-ray beams from NSLS, CFN and CHESS for in-situ characterization of K-Cs-Sb cathode growth. We have also designed and built several load-lock systems for ex-situ cathode fabrication and quick cathode exchange, to be used with a number of guns. One load-lock system/cathode combination has been tested with a DC gun and the others will be tested with SRF guns operating at 112 and 704 MHz. In this paper we will present the results on improving the QE with excimer laser and the performance of the load-lock/cathode combination in the guns.

TUPSO64

Short SASE-FEL Pulses at FLASH

laser, FEL, radiation, free-electron-laser

379

J. Rönsch-Schulenburg, E. Hass, A. Kuhl, T. Plath, M. Rehders, J. Roßbach
Uni HH, Hamburg, Germany
G. Brenner, C. Gerth, U. Mavrič, H. Schlarb, E. Schneidmiller, S. Schreiber, B. Steffen, M. Yan, M.V. Yurkov
DESY, Hamburg, Germany

Funding: This project has been supported by BMBF under contract 05K10GU2 & FS FLASH 301
FLASH is a high-gain free-electron laser (FEL) in the soft x-ray range. This paper discusses the production of very short FEL pulses in the SASE-mode without an external seeding signal at FLASH in the optimal case the single-spike operation. A new photo-injector laser has been commissioned, which allows the generation of shorter bunches with low bunch charge directly at the photo-cathode. This shorter injector laser reduces the required bunch compression for short pulses and thus allows a stable SASE performance with shorter pulses. First SASE performance using the new injector laser has been demonstrated and electron bunch and FEL radiation properties have been measured. Beam dynamics as well as the optimization of bunch diagnostics for low charge and short bunches are discussed.

TUPSO66

Transport of Terahertz-Wave Coherent Synchrotron Radiation With a Free-electron Laser Beamline at LEBRA

FEL, radiation, undulator, linac

383

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

Funding: This work was supported by JSPS Grant-in-Aid for Challenging Exploratory Research 2365696.
Nihon University and AIST have jointly developed terahertz-wave coherent synchrotron radiation (CSR) at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University. We have already observed intense terahertz-wave radiation from a bending magnet located above an undulator, and confirmed it to be CSR*. To avoid a damage caused by ionizing radiation, we worked on transporting the CSR to an experimental room which was next to the accelerator room. By using a beamline of an infrared free-electron laser, the CSR more than 1 mW was successfully transported to the experimental room. The transport of the CSR and imaging experiments with the CSR at LEBARA will be reported.
*: N. Sei et al., “Observation of intense terahertz-wave coherent synchrotron radiation at LEBRA”, J. Phys. D, 46 (2013) 045104.

TUPSO67

Design Optimization of 100 Kv DC Gun Wehnelt Electrode for FEL Linac at LEBRA

gun, cathode, simulation, extraction

387

T. Sakai, K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Tanaka
LEBRA, Funabashi, Japan

The 125-MeV electron linac at the Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University has been used for generation of the near infrared FEL and the Parametric X-ray Radiation. In addition, the THz beam generated in a bending magnet became available in the FEL experimental rooms in 2012 by transporting in the FEL optical beam line. The electron gun system for the LEBRA linac can extract the electron beam in three modes, the full bunch, the superimposed and the burst modes. However, the shape of the electron gun wehnelt electrode has not been optimized for the operation with the superimposed or the burst modes; the wehnelt was designed for use in the full bunch operation. The beam trace simulation suggested that the beam extracted from the cathode in the superimposed and the burst modes was slightly lost at the anode due to the strong space charge effect resulted from a high peak extraction current. Therefore, simulation of the beam trace was carried out to optimize the wehnelt shape for the maximum beam extraction efficiency for all the beam operation modes. The present paper reports the result of the simulation on the optimized electron gun design.

TUPSO69

Injector Design Studies for NGLS

gun, emittance, simulation, cathode

391

C. F. Papadopoulos, P. Emma, D. Filippetto, H.J. Qian, F. Sannibale, M. Venturini, R.P. Wells
LBNL, Berkeley, California, USA

Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
The APEX project at LBNL is developing an electron injector to operate a high repetition rate x-ray FEL. The injector is based on the VHF gun, a high-brightness, high-repetition-rate photocathode electron gun presently under test at LBNL. The design of the injector is particularly critical because it has to take the relatively low energy beam from the VHF gun, accelerate it at more relativistic energies while simultaneously preserving high-brightness and performing longitudinal compression. The present status of the APEX injector design studies is presented.

TUPSO74

A Coaxially Coupled Deflecting-accelerating Mode Cavity System for Phase-space Exchange (PSEX)

cavity, coupling, simulation, emittance

395

Y.-M. Shin, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
M.D. Church
Fermilab, Batavia, USA
J.H. Park, A.M.M. Todd
AES, Princeton, New Jersey, USA

A feasible method to readily remove energy spread (R56 term) due to thick lens effect of a deflecting mode RF-cavity has been widely investigated for emittance exchange in 6D phase-space*,**. By means of theoretical calculation and numerical analysis, it was found that an accelerating cavity effectively cancel the longitudinal phase space chirp. We have extensively investigated the combined deflecting-accelerating mode phase-space exchanger with the simple RF distribution system of the beam-pipe coaxial coupler. EM simulations proved the coupling scheme with eigenmode and S-parameter analyses. Currently we are looking into 3D beam dynamics in the system with tracking/particle-in-cell (PIC) simulations and wakefield analysis. Proof-of-concept (POC) experiment is planned with a high-Q normal conducting cavity built in a cryogenic cooling system (liquid nitrogen) in Fermilab.
* P. Emma, et. al., Phys. Rev. ST Accel. Beams 9, 100702 (2006)
** Zholents and M. Zolotorev, LBNL CBP Seminar (2010) and No. ANL/APS/LS-327(2011)

TUPSO77

Analytical and Numerical Analysis of Electron Trajectories in a 3-D Undulator Magnetic Field

undulator, focusing, radiation, simulation

406

N.V. Smolyakov, S.I. Tomin
NRC, Moscow, Russia
G. Geloni
XFEL. EU, Hamburg, Germany

In this contribution we present an analysis of electron trajectories in the three dimensional magnetic field from a planar undulator. The electron trajectory is influenced by the focusing properties of the undulator field. These focusing properties should be taken into account in simulations of spontaneous radiation, which constitutes the background signal of the FEL. The ideal magnetic field of an undulator can be described, in agreement with Maxwell equations, by a sinusoidal vertical magnetic field on the undulator axis, and by horizontal and longitudinal field components that appear out of axis. Exploiting this description for the ideal case, the differential equations of motion were solved by means of a perturbation theory approach, and the corresponding expressions for the electrons velocities and trajectories are derived. A computer code was also written, which relies on the Runge-Kutta algorithm. The analytical and numerical methods could then be compared, showing a good agreement.

TUPSO80

The MAX IV Linac and First Design for an Upgrade to 5 GeV to Drive an X-ray FEL

linac, FEL, simulation, storage-ring

413

S. Thorin, F. Curbis, N. Čutić, M. Eriksson, O. Karlberg, F. Lindau, A.W.L. Mak, E. Mansten, S. Werin
MAX-lab, Lund, Sweden

The installation of the MAX IV linear accelerator is in full progress, and commissioning is planned to start in the second quarter of 2014. The 3 GeV linac will be used as a full energy injector for the two storage rings, and as a high brightness driver for a Short Pulse linac light source. The linac has been deigned to also handle the high demands of an FEL injector. The long term strategic plan for the MAX IV laboratory includes an extension of the linac to 5 GeV and an X-ray FEL. In this paper we present the both design concept and status of the MAX IV linac along with parameters of the 3 GeV high quality electron pulses. We also present the first design and simulation results of the upgrade to a 5 GeV X-ray FEL driver.

TUPSO81

Challenges for Detection of Highly Intense FEL Radiation: Photon Beam Diagnostics at FLASH1 and FLASH2

FEL, photon, diagnostics, radiation

417

K.I. Tiedtke, M. Braune, G. Brenner, S. Dziarzhytski, B. Faatz, J. Feldhaus, B. Keitel, M. Kuhlmann, H. Kühn, E. Plönjes, A.A. Sorokin, R. Treusch
DESY, Hamburg, Germany

In spite of the evident progress in the development of FEL facilities, the characterization of important FEL photon beam parameters during FEL-commissioning and user experiments is still a great challenge. In particular pulse-resolved photon beam characterization is essential for most user experiments, but the unique properties of FEL radiation properties such as extremely high peak powers and short pulse lengths makes the shot-to-shot monitoring of important parameters very difficult. Therefore, sophisticated concepts have been developed and used at FLASH in order to measure radiation pulse intensity, beam position and spectral as well as temporal distribution – always coping with the highly demanding requirements of user experiments as well as machine operation. Here, an overview on the photon diagnostic devices operating at FLASH and FLASH II will be presented, with emphasizes on the pulse resolving intensity and energy detectors based on photoionization of rare gases.

TUPSO82

Spectroscopy System for LCLS Photocathodes

vacuum, gun, cathode, emittance

421

P. Stefan, A. Brachmann, T. Vecchione
SLAC, Menlo Park, California, USA

Funding: Work supported by US DOE contract DE-AC02-76SF00515.
Photocathode reliability is important from an operational standpoint. Unfortunately LCLS copper photocathodes have not always been reliable. Some have operated well for long periods of time while others have required continual maintenance. It is believed that the observed variations in quantum efficiency, emittance and lifetimes are inherently surface related, corresponding to changes in composition or morphology. The RF Electron-gun Cathode, Electron Surface Spectrometer, or RECESS, system has been commissioned to study this by making essential measurements that could not be obtained otherwise. These involve photocathode surface chemical characterization. The system is designed to use a combination of angle-resolved ultraviolet and x-ray photoelectron spectroscopy and is capable of either stand-alone operation or interoperability with a beam line at SSRL. Here we report on the first commissioning spectra and the direction of the project going forward.

TUPSO83

Quantum Efficiency and Transverse Momentum From Metals

brightness, FEL, vacuum, laser

424

T. Vecchione, D. Dowell
SLAC, Menlo Park, California, USA
J. Feng, H.A. Padmore, W. Wan
LBNL, Berkeley, California, USA

Funding: Work supported by US DOE contracts DE-AC02-05CH11231, KC0407-ALSJNT-I0013, and DE-SC000571.
QE and transverse momentum are key parameters limiting the achievable brightness of FELs. Despite the importance, little data is available to substantiate current models. Expressions for each and experimental confirmation of each expression with respect to excess energy are presented. Novel instrumentation and analysis techniques developed are described.

TUPSO85

High Brightness Electron Beams from a Multi-filamentary Niobium-tin Photocathode

cathode, emittance, laser, space-charge

431

C. Vicario, A. Anghel, F. Ardana-Lamas, C.P. Hauri, F. Le Pimpec
PSI, Villigen PSI, Switzerland
C.P. Hauri
EPFL, Lausanne, Switzerland

High-brightness electron sources are of fundamental interest for modern FELs. Inspired by the micro-structure of field emitter arrays, we propose a new type of metallic photo-cathode consisting of thousands of Nb3Sn micro-columns. With this metallic photo-cathode quantum efficiencies up to 0.5% are achieved under stable operation, and preliminary emittance measurements are presented.

TUPSO86

Photocathode Laser Wavelength-tuning for Thermal Emittance and Quantum Efficiency Studies

laser, emittance, cathode, photon

434

C. Vicario, S. Bettoni, B. Beutner, M.C. Divall, C.P. Hauri, E. Prat, T. Schietinger, A. Trisorio
PSI, Villigen PSI, Switzerland

SwissFEL compact design is based on extremely low emittance electron beam from an RF photoinjector. Proper temporal and spatial shaping of the photocathode drive laser is employed to reduce the space charge emittance contribution. However, the ultimate limit for the beam emittance is the thermal emittance, which depends on the excess energy of the emitted photoelectrons. By varying the photocathode laser wavelength it is possible to reduce the thermal emittance. For this purpose, we developed a tunable Ti:sapphire laser and an optical parametric amplifier which allow to scan the wavelength between 250 and 305 nm. The system permits to study the thermal emittance and the quantum efficiency evolution as function of the laser wavelength for the copper photocathode in the RF gun of the SwissFEL injector test facility. The results are presented and discussed.

TUPSO88

New Concept for the SwissFEL Gun Laser

laser, cathode, gun, FEL

442

A. Trisorio, M.C. Divall, C.P. Hauri, C. Vicario
PSI, Villigen PSI, Switzerland
A. Courjaud
Amplitude Systemes, Pessac, France

The operation of Swiss FEL put very stringent constrains on the gun laser system. First the parameters, such as energy stability, timing jitter, double pulse operation, temporal and spatial pulse shape of the ultra-violet laser pulses used to generate the photo-electrons are challenging even for the state of the art laser technologies. Second, the laser system must be extremely stable, reliable and its maintenance cost as low as possible. In this perspective, we prospected for alternative technologies to the well known, commonly used but costly Ti:sapphire laser systems. We show that a hybrid Yb fiber and solid state Yb:CaF2 amplifier system can be a very interesting approach. This gain medium allows the production of sub-500 fs, high fidelity, high stability, high energy pulses in the ultra-violet with low timing jitter. The system profits of the mature, stable direct diode pumping technology and optimized design. It delivers the two high-energy, shaped UV pulses separated by 28 ns to produce the photo-electrons, a short IR probe (<100 fs FWHM) to temporally characterize those pulses and the two stretched IR pulses ( 50 ps FWHM) necessary for the laser heater.

TUPSO91

FEL R&D Within LA3NET

laser, diagnostics, pick-up, ion

452

C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom

Funding: Work supported by the EU under Grant Agreement 289191.
The detailed diagnostics of the shortest beam pulses in free-electron lasers still pose significant challenges to beam instrumentation. Electro-optical methods are a promising approach for the non-intercepting measurement of electron bunches with a time resolution of better than 50 fs, but suitable optical materials need to be better understood and carefully studied. In addition, adequate timing systems with stability in the fs regime based on mode-locked fibre laser optical clocks, and actively length-stabilised optical fibre distribution require further investigation. Within the EU-funded LA³NET project these important problems are being addressed by an international consortium of research centres, universities, and industry partners. This contribution gives an overview of the LA3NET project and results from initial studies in both areas. It also describes the events, such as schools, topical workshops and conferences that LA3NET will organize.

TUPSO92

Dark Current Measurements at the Rossendorf SRF Gun

cavity, gun, cathode, SRF

455

R. Xiang, A. Arnold, P.N. Lu, P. Murcek, J. Teichert, H. Vennekate
HZDR, Dresden, Germany
R. Barday, T. Kamps
HZB, Berlin, Germany
V. Volkov
BINP SB RAS, Novosibirsk, Russia

Funding: the European Community-Research Infrastructure Activity (EuCARD, contract number 227579) and the German Federal Ministry of Education and Research grant 05 ES4BR1/8
In high gradient photo injectors electron field emission creates so-called dark current. The dark current produces beam loss that increases the radiation level, causes damages to the accelerator components, and produces additional background for the users. Field emitted electrons which stay inside the gun, increases RF power consumption and heat load for the superconducting cavities. It is also believed that dark current is the source of local outgassing and plasma formation which can damage sensitive photocathodes. Thus, to understand and control the dark current has become increasingly important for accelerators. In this presentation, we report on dark current measurement at the ELBE SRF Gun at HZDR. The measurements were carried out with the 3.5 cell-cavity SRF gun and Cs2Te photocathodes. We discuss the dark current behavior for different cavity gradients and various solenoid fields. Simulations have been done to understand the experimental results.

WEIANO01

Towards Zeptosecond-scale Pulses From X-ray Free Electron Lasers

FEL, radiation, undulator, laser

458

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

The short wavelength and high peak power of the present generation of Free-Electron Lasers (FELs) opens the possibility of ultra-short pulses even surpassing the present (~10-100 attosecond) capabilities of other light sources – but only if x-ray FELs can be made to generate pulses consisting of just a few optical cycles. For hard x-ray operation (<~0.1nm), this corresponds to durations of approximately a single attosecond, and below into the zeptosecond scale. This talk will describe a proposed method [1] to generate trains of few-cycle pulses, at GW peak powers, from existing x-ray FEL facilities by using a relatively short 'afterburner'. Such pulses would enhance research opportunity in atomic dynamics and push capability towards the investigation of electronic-nuclear and nuclear dynamics. The corresponding multi-colour spectral output, with a bandwidth envelope increased by up to two orders of magnitudes over SASE, also has potential applications.
[1] D.J. Dunning, B.W.J. McNeil, N.R. Thompson, Phys. Rev. Lett. 110, 104801 (2013).

Slides WEIANO01 [3.492 MB]

WEOANO01

New Scheme to Generate a Multi-terawatt and Attosecond X-ray Pulse in XFELs

target, laser, undulator, FEL

464

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

A new scheme to be applied in XFELs has been recently proposed*, which effectively compresses the X-ray pulse, i.e., shortens the pulse length and enhances the peak power by means of inducing a periodic current enhancement with an optical laser and applying a temporal shift between the X-ray and electron beams. In this paper, detailed mechanism of the new scheme is explained together with numerical results applied to the SACLA XFEL facility.
*T. Tanaka, PRL 110, 084801 (2013)

Slides WEOANO01 [4.177 MB]

WEOANO03

Longitudinal Coherence in an FEL With a Reduced Level of Shot Noise

FEL, laser, radiation, undulator

469

V.A. Goryashko
Private Address, Uppsala, Sweden
V.G. Ziemann
Uppsala University, Uppsala, Sweden

For a planar free electron laser (FEL) configuration we study self-amplified coherent spontaneous emission driven by a gradient of the bunch current in the presence of different levels of noise in bunches [1]. We calculate the probability density distribution of the maximum power of the radiation pulses for different levels of shot noise. It turns out that the temporal coherence quickly increases as the noise level reduces. We also show that the FEL based on coherent spontaneous emission produces almost Fourier transform limited pulses and the time-bandwidth product is mainly determined by the bunch length and the interaction distance in an undulator. We also propose a scheme that permits the formation of electron bunches with a reduced level of noise and a high gradient of the current at the bunch tail to enhance coherent spontaneous emission. The presented scheme uses effects of noise reduction and controlled microbunching instability and consists of a laser heater, a bunch compressor, and a shot noise suppression section. The noise factor and microbunching gain of the overall proposed scheme with and without laser heater are estimated.
V.A. Goryashko and V. Ziemann, Phys. Rev. ST Accel. Beams 16, 030702 (2013).

Slides WEOANO03 [1.999 MB]

WEIBNO01

Super-radiant Linac-based THz Sources in 2013

laser, undulator, photon, linac

474

M. Gensch
HZDR, Dresden, Germany

There is a growing interest in THz and far infrared light sources for use in material studies. Both coherent radiative sources (CSR, COTR, etc.) and FEL sources have been developed in the last few years to address this need. This talk will describe recent developments in this growing field.

WEOBNO03

Intense Emission of Smith-Purcell Radiation at the Fundamental Frequency from a Grating Equipped with Sidewalls

radiation, simulation, bunching, solenoid

477

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

The two-dimensional theory of the Smith-Purcell free-electron laser predicts that coherent Smith-Purcell radiation can occur only at harmonics of the frequency of the evanescent wave that is resonant with the beam. Particle-in-cell simulations have shown that in a three-dimensional context, where the lamellar grating has sidewalls, coherent Smith-Purcell radiation can be copiously emitted at the fundamental frequency, for a well-defined range of beam energy. An experiment at microwave frequencies has confirmed this prediction . The power output is considerably greater than for the previously observed emission at the second harmonic, in agreement with three-dimensional simulations . The dependence of frequency on beam energy and emission angle is in good agreement with three-dimensional theory and simulations. Provided that a reduction in scale can be achieved, a path is open to coherent Smith-Purcell radiation at Terahertz frequencies.
(1) J. Gardelle, P. Modin and J.T. Donohue, Appl. Phys. Lett. 100, 131103 (2012).
(2) J. T. Donohue and J. Gardelle, Appl. Phys. Lett. 99, 161112 (2011).

Slides WEOBNO03 [11.891 MB]

WEOCNO03

3-D Theory of a High Gain Free-Electron Laser Based on a Transverse Gradient Undulator

FEL, undulator, emittance, radiation

481

P. Baxevanis, Y. Ding, Z. Huang, R.D. Ruth
SLAC, Menlo Park, California, USA

The performance of a free-electron laser (FEL) depends significantly on the various parameters of the driving electron beam. In particular, a large energy spread in the beam results in a great reduction of the FEL gain, an effect which is relevant when one considers FELs driven by plasma accelerators or storage rings. For such cases, one possible solution is to use a transverse gradient undulator (TGU) [*,**]. In this concept, the energy spread problem is mitigated by properly dispersing the e-beam and introducing a linear, transverse field dependence in the undulator. This paper presents a self-consistent theoretical analysis of a TGU-based high gain FEL, taking into account three-dimensional (3-D) effects and beam size variations along the undulator [***]. The results of our theory compare favorably with simulation and are used in fast optimization studies of various X-ray FEL configurations.
*T. Smith et al., J. Appl. Phys. 50, 4580 (1979).
**Z. Huang, Y. Ding, C. Schroeder, Phys. Rev. Lett. 109, 204801 (2012).
***P. Baxevanis, R. Ruth, Z. Huang, Phys. Rev. ST-AB 16, 010705 (2013).

Slides WEOCNO03 [3.217 MB]

WEPSO01

Free Electron Lasers in 2013

FEL, undulator, laser, free-electron-laser

486

J. Blau, K. R. Cohn, W.B. Colson, R. Vigil
NPS, Monterey, California, USA

Funding: This work has been supported by the Office of Naval Research.
Thirty-seven years after the first operation of the short wavelength free electron laser (FEL) at Stanford University, there continue to be many important experiments, proposed experiments, and user facilities around the world. Properties of FELs in the infrared, visible, UV, and x-ray wavelength regimes are tabulated and discussed.

WEPSO02

Results and Perspectives on the FEL Seeding Activities at FLASH

laser, undulator, FEL, radiation

491

J. Bödewadt, C. Lechner
Uni HH, Hamburg, Germany

In recent years, several methods of free-electron laser (FEL) seeding, such as high-gain harmonic generation (HGHG), self-seeding, or direct FEL amplification of external seed pulses, have proven to generate intense, highly coherent radiation pulses in the extreme ultraviolet (XUV), soft- (SXR) and hard (HXR) X-ray spectral range. At DESY in Hamburg, the FEL facility FLASH is currently being upgraded by a second undulator beamline (FLASH2) which allows for the implementation of various seeding schemes. The development of high repetition-rate, high-power laser systems allows for the production of seed sources which match the bunch-train pattern of FLASH. Furthermore, the FLASH1 beamline arrangement is well suited for testing various seeding schemes including HGHG, EEHG, HHG-seeding, and hybrid schemes. In this contribution, we* give an overview of latest results and planned FEL seeding activities at FLASH.
*Joern Boedewadt on behalf of the FLASH seeding collaboration (DESY, U Hamburg, TU Dortmund, U Uppsala, U Stockholm)

WEPSO04

The Conceptual Design of CLARA, a Novel FEL Test Facility for Ultra-short Pulse Generation

FEL, laser, undulator, free-electron-laser

496

J.A. Clarke, D. Angal-Kalinin, R.K. Buckley, S.R. Buckley, P.A. Corlett, L.S. Cowie, D.J. Dunning, B.D. Fell, P. Goudket, A.R. Goulden, S.P. Jamison, J.K. Jones, A. Kalinin, B.P.M. Liggins, L. Ma, K.B. Marinov, P.A. McIntosh, J.W. McKenzie, K.J. Middleman, B.L. Militsyn, A.J. Moss, B.D. Muratori, H.L. Owen, R.N.C. Santer, Y.M. Saveliev, R.J. Smith, S.L. Smith, E.W. Snedden, M. Surman, T.T. Thakker, N. Thompson, R. Valizadeh, A.E. Wheelhouse, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
R. Appleby, R.J. Barlow, H.L. Owen, M. Serluca, G.X. Xia
UMAN, Manchester, United Kingdom
R. Appleby, G. Burt, S. Chattopadhyay, D. Newton, A. Wolski
Cockcroft Institute, Warrington, Cheshire, United Kingdom
R. Bartolini, S.T. Boogert, A. Lyapin
JAI, Oxford, United Kingdom
N. Bliss, R.J. Cash, G. Cox, G.P. Diakun, A. Gallagher, D.M.P. Holland, B.G. Martlew, M.D. Roper
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
S.T. Boogert
Royal Holloway, University of London, Surrey, United Kingdom
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
L.T. Campbell, B.W.J. MᶜNeil
USTRAT/SUPA, Glasgow, United Kingdom
A.M. Kolano
University of Huddersfield, Huddersfield, United Kingdom
I.P.S. Martin
Diamond, Oxfordshire, United Kingdom
D. Newton, A. Wolski
The University of Liverpool, Liverpool, United Kingdom
V.V. Paramonov
RAS/INR, Moscow, Russia

The conceptual design of CLARA, a novel FEL test facility focussed on the generation of ultra-short photon pulses with extreme levels of stability and synchronisation is described. The ultimate aim of CLARA is to experimentally demonstrate that sub-coherence length pulse generation with FELs is viable, and to compare the various schemes being championed. The results will translate directly to existing and future X-ray FELs, enabling them to generate attosecond pulses, thereby extending the science capabilities of these intense light sources. This paper will describe the design of CLARA, pointing out the flexible features that will be incorporated to allow multiple novel FEL schemes to be proven.

WEPSO05

Progress of the LUNEX5 Project

laser, FEL, undulator, free-electron-laser

502

M.-E. Couprie, C. Benabderrahmane, L. Cassinari, J. Daillant, C. Evain, N. Hubert, M. Labat, A. Loulergue, J. Lüning, P. Marchand, O. Marcouillé, C. Miron, P. Morin, A. Nadji, P. Roy, T. Tanikawa
SOLEIL, Gif-sur-Yvette, France
S. Bielawski, M. Le Parquier, E. Roussel, C. Szwaj
PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
B. Carré, D. Garzella
CEA/DSM/DRECAM/SPAM, Gif-sur-Yvette, France
N. Delerue
LAL, Orsay, France
G. Devanz
CEA/IRFU, Gif-sur-Yvette, France
A. Dubois
CCPMR, Paris, France
G. Lambert, R. Lehé, V. Malka, C. Thaury
LOA, Palaiseau, France
G. Le Bec
ESRF, Grenoble, France
M. Luong
CEA/DSM/IRFU, France

LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation) aims at investigating the production of short, intense, and coherent pulses in the soft X-ray region, with a 400 MeV superconducting linear accelerator and a laser wakefield accelerator (LWFA), feeding a single Free Electron Laser line with seeding with High order Harmonic in Gas and Echo Enable Harmonic Generation. After the Conceptual Design Report (CDR), R&D has been launched on specific magnetic elements (cryo-ready 3 m long in-vacuum undulator, a variable strong permanent magnet quadrupoles), on diagnostics (Smith-Purcell, electro-optics). In recent transport studies from a LWFA with more realistic beam parameters (1 % energy spread, 1 μm size and 1 mrad divergence) than the ones taken in the CDR, a longitudinal and transverse manipulation enables to provide theoretical amplification. A test experiment is under preparation. The French scientific community is increasing its participation to the use of operating FELs.

WEPSO06

The Test-FEL at MAX-lab: Implementation of the HHG Source and First Results

laser, FEL, radiation, undulator

507

F. Curbis, N. Čutić, F. Lindau, E. Mansten, S. Werin
MAX-lab, Lund, Sweden
F. Brizuela, B. Kim, A. L'Huillier
Lund University, Division of Atomic Physics, Lund, Sweden
M. Gisselbrecht
SLF, Lund, Sweden

The test-FEL at MAX-lab is a development set-up for seeding techniques. After the successful demonstration of coherent harmonic generation from a conventional laser, the new layout now presents a gas target for generation of harmonics. The drive laser will be up-converted and the low harmonics (around 100 nm) will seed the electron beam. The energy modulated electrons will then be bunched in the dispersive section and will radiate in the second undulator. We will detect the second harmonic of the HHG radiation around 50 nm. This experiment has several challenges never tried before: co-propagation of the electron beam and the drive laser, interaction of the electron beam with the gas in the target, no-focusing of the harmonics and no drive laser removal. The commissioning will show if this kind of in-line chamber has advantages with respect to more traditional approaches with optical beam transport. The results are relevant for many facilities that are planning to implement HHG seeding in the near future.

WEPSO07

Simulation Studies for an X-ray FEL Based on an Extension of the MAX IV Linac

FEL, linac, undulator, radiation

510

F. Curbis, N. Čutić, O. Karlberg, F. Lindau, A.W.L. Mak, E. Mansten, S. Thorin, S. Werin
MAX-lab, Lund, Sweden

It is well known that the few X-ray FELs around the world are severely overbooked by users. Having a medium energy linac, such as the one now being installed at the MAX IV laboratory, it becomes natural to think about slightly increasing the electron energy to drive an X-ray FEL. This development is now included in the long term strategic plan for the MAX IV laboratory. We will present the current FEL studies based on an extension of the MAX IV linac to 5 GeV to reach the Angstrom region. The injector for the MAX IV accelerator complex is also equipped with a photocathode gun, capable of producing low emittance electron beam. The bunch compression and linearization of the beam is taken care by two double achromats. The basic FEL layout would consist of short period undulators with tapering for extracting all the power from the electron beam. Self-seeding is considered as an option for increasing the spectral and intensity stability.

WEPSO09

Two-Color Self-seeding and Scanning the Energy of Seeded Beams at LCLS

FEL, photon, background, free-electron-laser

514

F.-J. Decker, Y. Ding, Y. Feng, M. Gibbs, J.B. Hastings, Z. Huang, H. Lemke, A.A. Lutman, A. Marinelli, A. Robert, J.L. Turner, J.J. Welch, D.H. Zhang, D. Zhu
SLAC, Menlo Park, California, USA

Funding: Work supported by U.S. Department of Energy, Contract DE-AC02-76SF00515.
The Linac Coherent Light Source (LCLS) produces typically SASE FEL pulses with an intensity of up to 5 mJ and at high photon energy a spread of 0.2% (FWHM). Self seeding with a diamond crystal reduces the energy spread by a factor of 10 to 40. The range depends on which Bragg reflection is used, or the special setup of the electron beam like over-compression. The peak intensity level is lower by a factor of about five, giving the seeded beam an advantage of about 2.5 in average intensity over the use of a monochromator with SASE. Some experiments want to scan the photon energy, which requires that the crystal angle be carefully tracked. At certain energies and crystal angles different lines are crossing which allows seeding at two or even three different colors inside the bandwidth of the SASE pulse. Out-off plane lines come in pairs, like [1 -1 1] and [-1 1 1], which can be split by using the yaw angle adjustments of the crystal, allowing a two-color seeding for all energies above 4.83 keV.

WEPSO10

Increased Stability Requirements for Seeded Beams at LCLS

FEL, linac, klystron, undulator

518

F.-J. Decker, W.S. Colocho, Z. Huang, R.H. Iverson, A. Krasnykh, A.A. Lutman, M.N. Nguyen, T.O. Raubenheimer, M.C. Ross, J.L. Turner, L. Wang
SLAC, Menlo Park, California, USA

Funding: Work supported by U.S. Department of Energy, Contract DE-AC02-76SF00515.
Running the Linac Coherent Light Source (LCLS) with self-seeded photon beams requires better electron beam stability, especially in energy, to reduce the otherwise huge intensity variations of more than 100%. Code was written to identify and quantify the different jitter sources. Some improvements are being addressed, especially the stability of the modulator high voltage of some critical RF stations. Special setups like running the beam off crest in the last part of the linac can also be used to reduce the energy jitter. Even a slight dependence on the transverse position was observed. The intensity jitter distribution of a seeded beam is still more contained with peaks up too twice the average intensity, compared to the jitter distribution of a SASE beam going through a monochromator, which can have damaging spikes up to 5 times the average intensity.

WEPSO11

Coherent X-Ray Seeding Source for Driving FELs

cavity, undulator, FEL, radiation

522

A. Novokhatski, F.-J. Decker, R.O. Hettel, Z. Huang, H.-D. Nuhn, M.K. Sullivan
SLAC, Menlo Park, California, USA

Funding: "Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515
The success of the hard X-ray self-seeding experiment at the LCLS is very important in that it provided narrow, nearly transform-limited bandwidth from the FEL, fulfilling a beam quality requirement for experimental applications requiring highly monochromatic X-rays. Yet, because the HXRSS signal is generated random spikes of noise, it is not a truly continuous monochromatic seed signal and even higher FEL performance would be achieved using a continuous seed source. We propose developing such a source using an X-ray cavity to achieve a continuous, narrow band X-ray seed signal. This cavity consists of four crystals with corresponding Bragg angles of about 45 degrees for each. We will analyze and the interaction of X-rays and electron beams with this cavity. This source uses a train of electron bunches initially accelerated in a linear accelerator which then pass through a radiator element situated within an X-ray cavity. The number of bunches is proportional to the achievable Q-value of the X-ray cavity and may be in the range of 10-100. We do not need a high output power of X-ray beams, which leads to relaxed electron beam requirements. We will consider several options.

WEPSO14

Towards High Frequency Operation with a Multi-Grating Smith-Purcell FEL

simulation, radiation, FEL, bunching

525

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

Three-dimensional simulations and experiments have shown that, for a grating equipped with sidewalls, copious emission of coherent Smith-Purcell (SP) radiation at the fundamental frequency of the evanescent surface wave is possible 1, 2. Since the underlying theory is scale invariant, the wavelength emitted is reduced in proportion to a uniform rescaling of the grating. In order to increase our 5 GHz to 100 GHz , the grating surface would be reduced by a factor of 400, which would lead to greatly reduced power. In addition, the required beam might be hard to generate. To avoid this, we propose to use several gratings in parallel with no overall reduction in the total width and the same beam as in our microwave experiment. For this scheme to succeed, it is essential that the bunching in the different gratings be coherent. . Simulations suggest that this occurs for as much as a ten-fold scale reduction. To test this idea, an experiment is using several gratings is being performed.
1. J. T. Donohue and J. Gardelle, Appl. Phys. Lett. 99, 161112 (2011).
2. J. Gardelle, P. Modin and J.T. Donohue, Appl. Phys. Lett. 100, 131103 (2012),.

WEPSO17

High-resolution Seeding Monochromator Design for NGLS

FEL, optics, undulator, brightness

529

Y. Feng, J.B. Hastings, J. Wu
SLAC, Menlo Park, California, USA
P. Emma, R.W. Schoenlein, T. Warwick
LBNL, Berkeley, California, USA

Funding: DOE/BES
A high-resolution soft X-ray seeding monochromator has been designed for self-seeding the Next-Generation Light Source (NGLS). The seeding monochromator system consists of a single variable-line-spacing grating, three mirrors and an exit slit and operates in the “fixed-focus” mode to achieve complete tuning of the seeding energy in range from 200 to 2000 eV with a nearly constant resolving power of over 2x104. The optical delay is less than 1 ps. The design is based upon a fully coherent treatment of the SASE FEL beam propagating from the upstream SASE undulator through the entire seeding monochromator system. This approach guides the design optimization in order to preserve the transverse beam profile entering the seeding undulator to ensure maximum efficiency.

WEPSO19

A Full Beam 1D Simulation Code for Modeling Hybrid HGHG/EEHG Seeding Schemes for Evaluating the Dependence of Bunching Factor Bandwidth on Multiple Parameters

bunching, laser, simulation, FEL

533

C.M. Fortgang, B.E. Carlsten, Q.R. Marksteiner, N.A. Yampolsky
LANL, Los Alamos, New Mexico, USA

Multiple seeding schemes are available for design of narrow-band, short-wavelength FELs. Analysis of such schemes often focus on the amplitude of the final bunching factor b, and how far it is above shot noise. Only under ideal conditions is the bandwidth of b FT limited. We have developed a 1D simulation tool that models complex hybrid seeding schemes using macro properties of the entire beam bunch to assess effects on both the amplitude and bandwidth of b. In particular the effects on bunching factor from using non-ideal beam driven radiators for downstream modulators, energy slew and curvature, and energy spread are investigated with the 1D tool.

WEPSO22

FERMI@Elettra Status Report

FEL, laser, linac, free-electron-laser

546

L. Giannessi, E. Allaria, F. Bencivenga, C. Callegari, F. Capotondi, D. Castronovo, P. Cinquegrana, P. Craievich, I. Cudin, G. D'Auria, M. Dal Forno, M.B. Danailov, R. De Monte, G. De Ninno, A.A. Demidovich, S. Di Mitri, B. Diviacco, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, E. Ferrari, L. Fröhlich, P. Furlan Radivo, G. Gaio, M. Kiskinova, M. Lonza, B. Mahieu, N. Mahne, C. Masciovecchio, F. Parmigiani, G. Penco, M. Predonzani, E. Principi, L. Raimondi, F. Rossi, L. Rumiz, C. Scafuri, C. Serpico, P. Sigalotti, S. Spampinati, C. Spezzani, M. Svandrlik, C. Svetina, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
P. Craievich
PSI, Villigen PSI, Switzerland
L. Giannessi
ENEA C.R. Frascati, Frascati (Roma), Italy
B. Mahieu
CEA/DSM/DRECAM/SPAM, Gif-sur-Yvette, France

Funding: Work supported in part by the Italian Ministry of University and Research under grants FIRB-RBAP045JF2 and FIRB-RBAP06AWK3
In this paper we report about the status of FERMI, the seeded Free Electron Laser located at the Elettra laboratory in Trieste, Italy. The facility welcomed the first external users on FEL-1 between December 2012 and March 2013, operating at wavelengths between 65 and 20 nm. Variable polarization and tunability of the radiation wavelength were widely used. Photon energies attained up to 200 microJoule, depending on the grade of spectral purity requested and on the selected wavelength. Pump-probe experiments were performed, both by double FEL pulses obtained via double pulse seeding of the electron beam and by providing part of the seed laser to the experimental stations as user laser. The FEL-2 line, covering the lower wavelength range between 20 and 4 nm thanks to a double stage cascaded HGHG scheme, operating in the "fresh bunch injection” mode, generated its first coherent photons in October 2012 and has seen further progress during the commissioning phases in 2013, at higher electron beam energy. In fact we will also report on the linac energy increase to 1.5 GeV and on the repetition rate upgrade from 10 to 50 Hz and eventually comment on the FEL operability and uptime.

WEPSO24

Compact XFEL Light Source

emittance, laser, FEL, cathode

757

W.S. Graves, K.K. Berggren, F.X. Kaertner, D.E. Moncton
MIT, Cambridge, Massachusetts, USA
P. Piot
Northern Illinois University, DeKalb, Illinois, USA

Funding: This work was supported by DARPA grant N66001-11-1-4192, CFEL DESY, DOE grants DE-FG02-10ER46745, and NSF grant DMR-1042342.
X-ray free electron laser studies are presented that rely on a nanostructured electron beam interacting with a “laser undulator” configured in the head-on inverse Compton scattering geometry. The structure in the electron beam is created by a nanoengineered cathode that produces a transversely modulated electron beam. Electron optics demagnify the modulation period and then an emittance exchange line translates the modulation to the longitudinal direction resulting in coherent bunching at x-ray wavelength. The predicted output radiation at 1 keV from a 7 MeV electron beam reaches 10 nJ or 6X10⁸ photons per shot and is fully coherent in all dimensions, a result of the dominant mode growth transversely and the longitudinal coherence imposed by the electron beam nanostructure. This output is several orders of magnitude higher than incoherent inverse Compton scattering and occupies a much smaller phase space volume, reaching peak brilliance of 10²⁷ and average brilliance of 10¹⁷ photons/(mm² mrad² 0.1% sec).

WEPSO26

Status of the Flash Facility

photon, FEL, undulator, radiation

550

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

The free-electron laser user facility FLASH at DESY (Hamburg, Germany)finished its 4th user period in February 2013. In total 2715 hours of SASE radiation has been delivered to user experiments with photon wavelengths between 4.2 nm and 44 nm with up to 5000 photon pulses per second. After a shutdown to connect the second undulator line - FLASH2 - to the FLASH linac, and a following commissioning period, FLASH is scheduled to continue user operation in October 2013. The year 2014 will be dedicated to the 5th period of user experiments. The commissioning of FLASH2 will take place in 2014 parallel to FLASH1 user operation.

WEPSO27

Recent LCLS Performance From 250 to 500 eV

FEL, undulator, diagnostics, laser

554

R.H. Iverson, J. Arthur, U. Bergmann, C. Bostedt, J.D. Bozek, A. Brachmann, W.S. Colocho, F.-J. Decker, Y. Ding, Y. Feng, J.C. Frisch, J.N. Galayda, T. Galetto, Z. Huang, E.M. Kraft, J. Krzywinski, J.C. Liu, H. Loos, X.S. Mao, S.P. Moeller, H.-D. Nuhn, A.A. Prinz, D.F. Ratner, T.O. Raubenheimer, S.H. Rokni, W.F. Schlotter, P.M. Schuh, T.J. Smith, M. Stanek, P. Stefan, M.K. Sullivan, J.L. Turner, J.J. Turner, J.J. Welch, J. Wu, F. Zhou
SLAC, Menlo Park, California, USA
P. Emma
LBNL, Berkeley, California, USA
R. Soufli
LLNL, Livermore, California, USA

Funding: Work supported by US Department of Energy contract DE-AC02-76SF00515 and BES.
The Linac Coherent Light Source is an X-ray free-electron laser at the SLAC National Accelerator Laboratory. It produces coherent soft and hard X-rays with peak brightness nearly ten orders of magnitude beyond conventional synchrotron sources and a range of pulse durations from 500 to <10 fs. The facility has been operating at X-ray energy from 500 to 10,000eV. Users have expressed great interest in doing experiments with X-Rays near the carbon absorption edge at 284eV. We describe the operation and performance of the LCLS in the newly established regime between 250 and 500eV.
[1] Emma, P. et al., “First lasing and operation of an ˚angstrom-wavelength free-electron laser,” Nature Pho-
ton. 4(9), 641–647 (2010).

WEPSO28

Fast Electron Beam and FEL Diagnostics at the ALICE IR-FEL at Daresbury Laboratory

FEL, cavity, laser, diagnostics

557

F. Jackson, D. Angal-Kalinin, D.J. Dunning, J.K. Jones, A. Kalinin, T.T. Thakker, N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
D. Angal-Kalinin, D.J. Dunning, J.K. Jones, N. Thompson
Cockcroft Institute, Warrington, Cheshire, United Kingdom

The ALICE facility at Daresbury Laboratory is an energy recovery based infra-red free electron laser of the oscillator type that has been operational since 2010. Recently fast diagnostics have been installed to perform combined measurements on pulse-by pulse FEL pulse energy and bunch-by-bunch electron bunch position and arrival time. These measurements have highlighted and quantified fast instabilities in the electron beam and consequently the FEL output, and are presented and discussed here.

WEPSO31

THz Radiation Source Potential of the R&D ERL at BNL

gun, SRF, linac, emittance

566

D. Kayran, I. Ben-Zvi, Y.C. Jing, B. Sheehy
BNL, Upton, Long Island, New York, USA

Funding: Work supported by BSA DOE, Contract No. DE-AC02-98CH10886
An ampere class 20 MeV superconducting Energy Recovery Linac (ERL) is under commissioning at Brookhaven National Laboratory (BNL) for testing concepts for high-energy electron cooling and electron-ion colliders. This ERL will be used as a test bed to study issues relevant for very high current ERLs. High repetition rate (9.5 MHz), CW operation and high performance of electron beam with some additional components make this ERL an excellent driver for high power coherent THz radiation source*. We discuss potential use of BNL ERL as a source of THz radiation and results of the beam dynamics simulation. We present the status and commissioning progress of the ERL.
*Ilan Ben-Zvi. et al. Coherent harmonic generation of THz radiation using wakefield bunching (presented at this conference)

WEPSO33

Remote RF Synchronization With Femtosecond Drift at PAL

laser, free-electron-laser, photon, radio-frequency

570

J. Kim, K. Jung, J. Lim
KAIST, Daejeon, Republic of Korea
L. Chen
Idesta Quantum Electronics, New Jersey, USA
S. Hunziker
PSI, Villigen PSI, Switzerland
F.X. Kaertner
CFEL, Hamburg, Germany
H.-S. Kang, C.-K. Min
PAL, Pohang, Kyungbuk, Republic of Korea

Funding: This research was supported by the PAL-XFEL Project, South Korea.
We present our recent progress in remote RF synchronization using an optical way at PAL. A 79.33-MHz, low-jitter fiber laser is used as an optical master oscillator (OMO), which is locked to the 2.856-GHz RF master oscillator (RMO) using a balanced optical-microwave phase detector (BOM-PD). The locked optical pulse train is then transferred via a timing-stabilized 610-m long optical fiber link. The output is locked to the 2.856 GHz voltage controlled oscillator (VCO) using the second BOM-PD, which results in remote synchronization between the RMO and the VCO. We measured the long-term phase drift between the input optical pulse train and the remote RF signals using an out-of-loop BOM-PD, which results in 2.7 fs (rms) drift maintained over 7 hours. We are currently working to measure the phase drift between the two RF signals and reduce the phase drift over longer measurement time.

WEPSO34

Proposal for a Scheme to Generate a 10 tw Power Level, Femtosecond X-ray Pulses for Bio-imaging of Single Protein Molecules at the European XFEL

undulator, photon, FEL, radiation

574

V. Kocharyan, G. Geloni, E. Saldin, S. Serkez, I. Zagorodnov
DESY, Hamburg, Germany
O. Yefanov
CFEL, Hamburg, Germany

Crucial parameters for bio-imaging experiments are photon energy range, peak power and pulse duration. For a fixed resolution, the largest diffraction signals are achieved at the longest wavelength supporting that resolution. In order to perform these experiments at the European XFEL, we propose to use a novel configuration combining self-seeding and undulator tapering techniques with the emittance-spoiler method. Experiments at the LCLS confirmed the feasibility of these three techniques. Their combination allows obtaining a dramatic increase the XFEL output peak power and a shortening of the photon pulse duration to levels sufficient for performing bio-imaging of single protein molecules at the optimal photon-energy range between 3 keV and 5 keV. We show here that it is possible to achieve up to a 100-fold increase in peak-power of the X-ray pulses at the European XFEL: the X-ray beam would be delivered in 10 fs-long pulses with 50 mJ energy each at a photon energy around 4 keV. We confirm by simulations that one can achieve diffraction before destruction with a resolution of 0.25 nm resolution.

WEPSO37

Femtosecond Fiber Timing Distribution System for the Linac Coherent Light Source

laser, free-electron-laser, linac, background

583

H. Li, P.H. Bucksbaum, J.C. Frisch, A.R. Fry, J. May, K. Muehlig, S.R. Smith
SLAC, Menlo Park, California, USA
L. Chen, H.P.H. Cheng
Idesta Quantum Electronics, New Jersey, USA
F.X. Kaertner
CFEL, Hamburg, Germany
F.X. Kaertner
MIT, Cambridge, Massachusetts, USA
A. Uttamadoss
PU, Princeton, New Jersey, USA

Funding: This work is supported by Department of Energy under STTR grant DE-C0004702.
We present the design and progress of a femtosecond fiber timing distribution system for the Linac Coherent Light Source (LCLS) at SLAC to enable the machine diagnostic at the 10 fs level. The LCLS at the SLAC is the world’s first hard x-ray free-electron laser (FEL) with unprecedented peak brightness and pulse duration. The time-resolved optical/x-ray pump-probe experiments on this facility open the era of exploring the ultrafast dynamics of atoms, molecules, proteins, and condensed matter. However, the temporal resolution of current experiments is limited by the time jitter between the optical and x-ray pulses. Recently, sub-25 fs rms jitter is achieved from an x-ray/optical cross-correlator at the LCLS, and external seeding is expected to reduce the intrinsic timing jitter, which would enable full synchronization of the optical and x-ray pulses with sub-10 fs precision. Of such a technique, synchronization between seed and pump lasers would be implemented. Preliminary test results of the major components for a 4 link system will be presented. Currently, the system is geared towards diagnostics to study the various sources of jitter at the LCLS.
*P. Emma et al.,Nat. Photonics 4,641-647(2010).
*J. Kim et al.,Opt. Lett,, 31,3659(2006).
*J. Kim et al.,Opt. Lett,, 32,1044(2007).
*J.Kim et al.,Nat. Photonics 2,733-736(2008).

WEPSO41

Feasibility Studies for Echo-enabled Harmonic Generation on CLARA

laser, bunching, FEL, radiation

588

I.P.S. Martin, R. Bartolini
Diamond, Oxfordshire, United Kingdom
R. Bartolini
JAI, Oxford, United Kingdom
N. Thompson
Cockcroft Institute, Warrington, Cheshire, United Kingdom
N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

The Compact Linear Accelerator for Research and Applications (CLARA) is a proposed single-pass FEL test facility, designed to facilitate experimental studies of advanced FEL techniques applicable to the next generation of light source facilities. One such scheme under consideration is Echo-Enabled Harmonic Generation (EEHG). In this paper we explore the suitability of CLARA for carrying out studies of this scheme, combining analytical and numerical calculations to determine likely hardware operating ranges, parameters tolerances and estimated FEL performance. A possible adaptation to convert EEHG into a short-pulse scheme is also considered.

WEPSO43

EEHG and Femtoslicing at DELTA

undulator, radiation, laser, synchrotron

594

R. Molo, H. Huck, M. Huck, M. Höner, S. Khan, A. Schick, P. Ungelenk
DELTA, Dortmund, Germany

The ultrashort-pulse facility at DELTA (a 1.5-GeV synchrotron light source operated by the TU Dortmund University) based on the coherent harmonic generation (CHG) technique will be upgraded using echo-enabled harmonic generation (EEHG) in order to reach shorter wavelengths. A laser-induced energy modulation is employed in the CHG and EEHG schemes to create a periodic electron density modulation, but can also be used to generate ultrashort pulses of incoherent radiation at arbitrary wavelengths by transversely displacing the off-energy electrons(femtoslicing). A new storage-ring lattice for DELTA will be presented that not only offers enough free straight sections for an EEHG and femtoslicing setup, but also allows to operate both radiation sources simultaneously.

WEPSO46

Study on the fluctuation of electron beam position in KU-FEL

gun, FEL, cavity, feedback

602

K. Okumura, M. Inukai, T. Kii, T. Konstantin, K. Masuda, K. Mishima, H. Negm, H. Ohgaki, M. Omer, Y. Tsugamura, K. Yoshida, H. Zen
Kyoto University, Institute for Advanced Energy, Kyoto, Japan

Stability of electron beam is important for stable FEL operation. In Kyoto University MIR-FEL facility (KU-FEL), a BPM (Beam Position Monitor) system consisting of six 4-button electrode type BPMs was installed for monitoring of the electron beam position. The fluctuation of the electron beam position has been observed in horizontal and vertical directions. The origin of the beam position fluctuation is not clarified. In horizontal direction, the main fluctuation source is expected to be the energy fluctuation. As the one of candidate of the energy fluctuation, the cavity temperature of the RF gun has been suspected because the gun is operated in detuned condition [1] which enhances beam energy dependence on the cavity temperature. Another candidate is considered to be the fluctuation of the RF power fed to the gun. Therefore, we start to study the effect of the cavity temperature and the RF power on the position of electron beam. In this conference, we will present the measured result and numerical evaluation of the beam position dependence on temperature and RF power.
[1] H. Zen, et al, “Beam Energy Compensation in a Thermionic RF Gun by Cavity Detuning,” IEEE transaction on nuclear science, Vol.56, No. 3, Pages 1487-1491 (2009)

WEPSO47

Simulation Results of Self-seeding Scheme in PAL-XFEL

radiation, undulator, simulation, emittance

606

Y.W. Parc, J.H. Han, I. Hwang, H.-S. Kang
PAL, Pohang, Kyungbuk, Republic of Korea
I.S. Ko
POSTECH, Pohang, Kyungbuk, Republic of Korea
J. Wu
SLAC, Menlo Park, California, USA

There are two major undulator lines in Pohang Accelerator Laboratory XFEL (PAL XFEL), soft X-ray and hard X-ray. For the hard X-ray undulator line, self-seeding is the most promising approach to supply narrow bandwidth radiation to the users. The electron energy at hard X-ray undulator is 10 GeV and the central wavelength is 0.1 nm. We plan to provide the self-seeding option in the Phase I operation of PAL-XFEL. In this talk, the simulation results for the self-seeding scheme of hard X-ray undulator line in PAL XFEL will be presented.

WEPSO48

Simulation Studies of FELs for a Next Generation Light Source

undulator, FEL, photon, simulation

609

G. Penn, P. Emma, G. Marcus, J. Qiang, M.W. Reinsch
LBNL, Berkeley, California, USA

Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Several possible FEL beamlines for a Next Generation Light Source are studied. These beamlines collectively cover a wide range of photon energies and pulse lengths. Microbunching and transverse offsets within the electron beam, generated through the linac, have the potential to significantly impact the longitudinal and transverse coherence of the x-ray pulses. We evaluate these effects and set tolerances on beam properties required to obtain the desired properties of the x-ray pulses.

WEPSO50

FLASH2 Beamline and Phontondiagnostics Concepts

photon, diagnostics, laser, undulator

614

E. Plönjes, B. Faatz, J. Feldhaus, M. Kuhlmann, K.I. Tiedtke, R. Treusch
DESY, Hamburg, Germany

The FLASH II project will upgrade the soft X-ray free electron laser FLASH at DESY into a multi-beamline FEL user facility with the addition of a second undulator line FLASH2. The present FLASH linear accelerator will drive both undulator lines and FLASH2 will be equipped with variable-gap undulators to be able to deliver two largely independent wavelengths to user endstations at FLASH1 and FLASH2 simultaneously. A new experimental hall will offer space for up to seven user endstations, some of which will be installed permanently. The beamline system will be set up to cover a wide wavelength range with up to three beamlines capable of delivering the 5th harmonic at 0.8 nm and a fundamental in the water window while others will cover the longer wavelengths of 6 - 40 nm and beyond. Photon diagnostics have been developed for many years at FLASH and are in routine operation. Online measurements of intensity, position, wavelength, wavefront, and pulse length are optimized as well as photon beam manipulation tools such as a gas absorber and filters. Civil construction and installations of FLASH II are on-going and first beam is expected for early 2014.

WEPSO51

Self-seeding Design for SwissFEL

FEL, undulator, simulation, radiation

618

E. Prat, S. Reiche
PSI, Villigen PSI, Switzerland

The SwissFEL facility, planned at the Paul Scherrer Institute, will provide SASE and self-seeded FEL radiation at a hard (1-7 Å) and soft (7-70 Å) X-ray FEL beamlines. This paper presents the current status of the self-seeding design for SwissFEL. The layout and full 6D start-to-end simulation results are presented for the hard X-ray beamline. Studies for different charges and optimization of the first and second undulator stages are shown.

WEPSO53

Harmonic Lasing at the LCLS

FEL, radiation, undulator, simulation

623

D.F. Ratner, Z. Huang, P.A. Montanez
SLAC, Menlo Park, California, USA
E. Allaria
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
W.M. Fawley, L.N. Rodes
LBNL, Berkeley, California, USA
E. Schneidmiller, M.V. Yurkov
DESY, Hamburg, Germany

Funding: Department of Energy
The LCLS beamlines deliver X-rays to users at photon energies up to 24 keV. With the fundamental wavelength limited to around 10 keV, there is user interest in the third harmonic, which can reach a few percent of the total beam power. McNeil et al* and Schneidmiller and Yurkov** have showed that introducing phase shifts or attenuators into the undulator line can increase harmonic power by driving lasing at the third harmonic. With the development of self-seeding chicanes, LCLS is now in position for a proof-of-principle experiment. Here we present simulations and plans for an experimental test following commissioning of the Soft X-ray Self-Seeding system.
*B.W.J. McNeil, G.R.M. Robb, M.W. Poole and N.R. Thompson, Phys. Rev. Lett., 96 084801 (2006)
**E. Schneidmiller and M. Yurkov, PR-STAB, 14 080702 (2012)

WEPSO57

Optimization of a Dedicated Bio-imaging Beamline at the European X-ray Fel

undulator, photon, FEL, radiation

632

E. Saldin, G. Geloni, V. Kocharyan, S. Serkez
DESY, Hamburg, Germany

We recently proposed a basic concept for design and layout of a dedicated undulator source for bio-imaging experiments at the European XFEL. Here we present an optimization of that concept. The core of the scheme is composed by soft and hard X-ray self-seeding setups. Using an improved design for both monochromators it is possible to increase the design electron energy up to 17.5 GeV in photon energy range between 2 keV and 13 keV, which is the most preferable for life science experiments. Operating at such high electron energy one increases the X-ray output peak power. Moreover, 17.5 GeV is the preferred operation energy for SASE1 and SASE2 users. This choice will reduce the interference with other undulator lines. We include a study of the performance of the self-seeding scheme accounting for spatiotemporal coupling caused by the use of a single crystal monochromator. This distortion can be easily suppressed by the right choice of diamond crystal planes. The proposed undulator source yields about the same performance as in the case for a X-ray seed pulse with no coupling. Simulations show that the FEL power reaches 2 TW in the 3 keV - 5 keV photon energy range.

WEPSO58

Status Report of the Short-pulse Facility at the Delta Storage Ring

radiation, laser, synchrotron, klystron

642

A. Schick, H. Huck, M. Huck, M. Höner, S. Khan, R. Molo, P. Ungelenk
DELTA, Dortmund, Germany

Funding: * Work supported by DFG, BMBF and by the Federal State NRW.
At DELTA, a 1.5-GeV synchrotron light source operated by the TU Dortmund university, a short-pulse facility employing the CHG (Coherent Harmonic Generation) principle is in operation. Here, the interaction of an intense, ultrashort laser pulse and electrons in an undulator leads to microbunching of a small fraction of the electrons in the bunch. As a consequence, ultrashort, coherent synchrotron-radiation pulses in the VUV regime are emitted at harmonics of the incident laser wavelength. In addition, coherent THz pulses on the sub-ps timescale are generated. In this paper, the latest improvements of the facility and recent measurements are presented, including investigation of the transverse coherence and detection of the CHG radiation using photoemission spectroscopy in a VUV beamline.

WEPSO59

A Possible Upgrade of FLASH for Harmonic Lasing Down to 1.3 nm

undulator, FEL, radiation, simulation

646

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

We propose the 3rd harmonic lasing in a new FLASH undulator as a way to produce intense, narrow-band, and stable SASE radiation down to 1.3 nm with the present accelerator energy of 1.25 GeV. To provide optimal conditions for harmonic lasing, we suggest to suppress the fundamental with the help of a special set of phase shifters. We rely on the standard technology of gap-tunable planar hybrid undulators, and choose the period of 2.3 cm and the minimum gap of 0.9 cm; total length of the undulator system is 34.5 m. We demonstrate that the 3rd harmonic lasing at 1.3 nm provides peak power at a gigawatt level and the narrow intrinsic bandwidth, 0.1% (FWHM). Pulse duration can be controlled in the range of a few tens of femtoseconds, and the peak brilliance reaches the value of 10³¹ photons/(s mrad² mm² 0.1% BW). With the given undulator design, a standard option of lasing at the fundamental wavelength to saturation is possible through the entire water window and at longer wavelengths. In this paper we briefly consider additional options such as polarization control, bandwidth reduction, self-seeding, X-ray pulse compression, and two-color operation.

WEPSO62

The IR and THz Free Electron Laser at the Fritz-Haber-Institut

FEL, free-electron-laser, laser

657

W. Schöllkopf, W. Erlebach, S. Gewinner, G. Heyne, H. Junkes, A. Liedke, G. Meijer, V. Platschkowski, G. von Helden
FHI, Berlin, Germany
H. Bluem, D. Dowell, K. Jordan, R. Lange, J. Rathke, A.M.M. Todd, L.M. Young
AES, Princeton, New Jersey, USA
M.A. Davidsaver
BNL, Upton, New York, USA
S.C. Gottschalk
STI, Washington, USA
U. Lehnert, P. Michel, W. Seidel, R. Wünsch
HZDR, Dresden, Germany
H. Loos
SLAC, Menlo Park, California, USA

A mid-infrared oscillator FEL with a design wavelength range from 4 to 50 μm has been commissioned at the Fritz-Haber-Institut in Berlin, Germany, for applications in molecular and cluster spectroscopy as well as surface science. The accelerator consists of a thermionic gridded electron gun, a subharmonic buncher and two S-band standing-wave copper structures. The device was designed to meet challenging specifications, including a final energy adjustable in the range of 15 to 50 MeV, low longitudinal emittance (< 50 keV-psec) and transverse emittance (< 20 π mm-mrad), at more than 200 pC bunch charge with aμpulse repetition rate of 1 GHz and a macro pulse length of up to 15 μs. Two isochronous achromatic 180 degree bends deliver the beam to the undulators, only one of which is presently installed, and to the beam dumps. Calculations of the FEL gain and IR-cavity losses predict that lasing will be possible in the wavelength range from less than 4 to more than 50 μm. First lasing was achieved at a wavelength of 16 μm in 2012*. We will describe the FEL system design and performance, provide examples of lasing, and touch on the first anticipated user experiments.
* W. Schöllkopf et al., MOOB01, Proc. FEL 2012.

WEPSO63

Extension of SASE Bandwidth up to 2 % as a Way to Increase Number of Indexed Images for Protein Structure Determination by Femtosecond X-Ray Nanocrystallography at the European XFEL

radiation, undulator, simulation, photon

661

S. Serkez, V. Kocharyan, E. Saldin, I. Zagorodnov
DESY, Hamburg, Germany
G. Geloni
XFEL. EU, Hamburg, Germany
O. Yefanov
CFEL, Hamburg, Germany

Experiments at the LCLS confirmed the feasibility of femtosecond nanocrystallography for protein structure determination at near-atomic resolution. These experiments rely on X-ray SASE pulses with a few microradians angular spread, and about 0.2 % bandwidth. By indexing individual patterns and then summing all counts in all partial reflections for each index it is possible to extract the square modulus of the structure factor. The number of indexed images and the SASE bandwidth are linked, as an increasing number of Bragg spots per individual image requires an increasing spectral bandwidth. This calls for a few percent SASE bandwidth. Based on start-to-end simulations of the European XFEL baseline, we demonstrate that it is possible to achieve up to a 10-fold increase of the electron energy chirp by strongly compressing a 0.25 nC electron bunch. This allows for data collection with a 2 % SASE bandwidth, a few mJ radiation pulse energy and a few fs-pulse duration, which would increase the efficiency of protein determination at the European XFEL. We prove this concept with simulations of photosystem-I nanocrystals, with a size of about 300 nm.

WEPSO64

Grating Monochromator for Soft X-ray Self-seeding the European XFEL

undulator, FEL, photon, optics

667

S. Serkez, G. Geloni, V. Kocharyan, E. Saldin
DESY, Hamburg, Germany

Self-seeding implementation in the soft X-ray wavelength range involves gratings as dispersive elements. We study a very compact self-seeding scheme with a grating monochromator originally designed at SLAC, which can be straightforwardly installed in the SASE3 undulator beamline at the European XFEL. The design is based on a toroidal VLS grating at a fixed incidence angle, and without entrance slit. It covers the spectral range from 300 eV to 1000 eV. The performance was evaluated using wave optics method vs ray tracing methods. Wave optics analysis takes into account the actual beam wavefront of the radiation from the FEL source, third order aberrations, and errors from optical elements. We show that, without exit slit, the self-seeding scheme gives the same resolving power (about 7000) as with an exit slit. Wave optics is also naturally applicable to calculations of the scheme efficiency, which include the monochromator transmittance and the effect of the mismatching between seed beam and electron beam. Simulations show that the FEL power reaches 1 TW, with a spectral density about two orders of magnitude higher than that for the SASE pulse at saturation.

WEPSO65

LEBRA Free Electron Laser as a Radiation Source for Photochemical Reactions in Living Organisms

FEL, radiation, controls, laser

675

F. Shishikura, K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Sakai, T. Tanaka
LEBRA, Funabashi, Japan

The radiation sources commonly used in plant applications are commercially available lamps developed for human lighting applications (fluorescent, metal halide, high-pressure sodium, incandescent, light-emitting diode, and laser diode). In contrast, free-electron lasers (FELs) such as LEBRA-FEL produce high-energy, tunable pulse radiation and thus are promising radiation sources for photochemical research. An advantage of LEBRA-FEL is that the peak intensity ranges from 0.35 to 6.5 microns which are wavelengths coinciding with the absorption peaks of living organisms. Previously, we established a microscopic irradiation technique for delivering visible FEL light to single cells through a tapered glass rod (< 10 microns). However, it is still unclear whether LEBRA-FEL can produce sufficient radiant energy at wavelengths effective for triggering photochemical reactions in living organisms. The aim of this study was to evaluate the effectiveness of LEBRA-FEL in lettuce-seed germination tests. Results show promotion by red light and inhibition by far-red light, indicating that LEBRA-FEL can be used to control lettuce-seed germination.

WEPSO67

Progress with the FERMI Laser Heater Commissioning

FEL, laser, linac, undulator

680

S. Spampinati, E. Allaria, D. Castronovo, M. Dal Forno, M.B. Danailov, G. De Ninno, A.A. Demidovich, S. Di Mitri, B. Diviacco, W.M. Fawley, E. Ferrari, L. Fröhlich, L. Giannessi, G. Penco, C. Spezzani, M. Trovò
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

FERMI@ELETTRA is a seeded free electron laser facility composed by one linac and two FEL lines named FEL-1 and FEL-2. FEL-1 works in HGHG configuration, while FEL2 is a HGHG cascade implementing "fresh bunch" injection into the second stage. Perfomance of FEL-1 and FEL-2 lines have benefited from the use of the laser heater system, which is located right after the injector, at 100 MeV beam energy. Proper tuning of the laser heater parameters has allowed control of the microbunching instability, which is otherwise expected to degrade the high brightness electron beam quality sufficiently to reduce the FEL power. The laser heater was commissioned one year ago and positive effects upon microbunching instabilities and FEL-1 performance was soon observed. In this work we presents further measurements of microbunching suppression in two compressors scheme showing directly the reduction of beam slice energy spread due to laser heater action. We present measuerements showing the impact of the laser heater on FEL2

WEPSO70

Fully Phase Matched High Harmonics Generation in a Hollow Waveguide for Free Electron Laser Seeding

laser, FEL, photon, free-electron-laser

693

C. Vicario
INFN/LNF, Frascati (Roma), Italy
F. Ardana-Lamas, C.P. Hauri, A. Trisorio
PSI, Villigen PSI, Switzerland
C.P. Hauri
EPFL, Lausanne, Switzerland
G. Lambert, V. Malka, B. Vodungbo, P. Zeitoun
LOA, Palaiseau, France

Funding: LASERLAB-EUROPE, grant n◦ 228334 PARIS ERC project (Contract No. 226424) Swiss National Science Foundation under grant PP00P2_128493
A bright high harmonic source is presented delivering up to 10¹¹ photons per second around a central photon energy of 120 eV. Fully phase matched harmonics are generated in an elongated capillary reaching a cut-off energy of 160 eV. The high HHG fluence opens new perspectives towards seeding FELs at shorter wavelengths than the state of the art. Characterization of the phase matching conditions in the capillary is presented.

WEPSO73

High Average Power Seed Laser Design for High Reprate FELs

laser, FEL, vacuum, controls

697

R.B. Wilcox, G. Marcus, G. Penn
LBNL, Berkeley, California, USA
T. Metzger, M. Schultze
TRUMPF Scientific Lasers GmbH + Co. KG, Munchen-Unterfoehring, Germany

Funding: US Department of Energy, under Contract Numbers DE-AC02-0SCH11231.
In the proposed Next Generation Light Source (NGLS), FEL designs use lasers to seed the FEL in an HGHG scheme or bunch the electron beam in an E-SASE scheme. The FELs would run at 100kHz to 1MHz, requiring high average power lasers. For the seeded FEL, laser modulation is applied at 200-240nm, with 250-700MW peak power depending on pulse length, which can vary from 100-10fs. The laser consists of a broadband oscillator and amplitude/phase shaper seeding an optical parametric amplifier (OPA). After recompression, the ~800nm pulse is converted to the fourth harmonic. Losses could be high enough to require 250W at 100kHz, making the OPA ~100x more powerful than existing femtosecond OPAs. In the E-SASE scheme, a single cycle of 5 micron light bunches the beam, which then radiates a short X-ray burst. This requires 100% fractional bandwidth, and precise phase control of the e-field within the pulse, as well as broad band compensation of dispersion throughout the laser path. Bandwidth can be increased by splitting the amplified spectrum into segments and coherently recombining. We present design concepts that are expected to meet requirements, and identify R&D needs.

WEPSO78

Harmonic Lasing Self-seeded FEL

undulator, FEL, simulation, resonance

700

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

In this paper we perform analysis of capabilities of SASE FELs at the European XFEL for generation of narrow band radiation. An approach based on application of harmonic lasing self-seeding (HLSS) is under study[*]. Effective harmonic lasing occurs in the exponential gain regime in the first part of the undulator, making sure that the fundamental frequency is well below saturation. In the second part of the undulator the value of undulator parameter is reduced such that now the fundamental mode is resonant to the wavelength, previously amplified as the harmonic. The amplification process proceeds in the fundamental mode up to saturation. In this case the bandwidth is defined by the harmonic lasing (i.e. it is reduced by a significant factor depending on harmonic number) but the saturation power is still as high as in the reference case of lasing at the fundamental, i.e. brilliance increases. Application of the undulator tapering in the deep nonlinear regime would allow to generate higher peak powers approaching TW level.
* E.A. Schneidmiller and M.V. Yurkov, Phys. Rev. ST-AB 15, 080702 (2012)

WEPSO80

Coherence Properties of the Radiation From FLASH

radiation, emittance, FEL, undulator

704

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

Several user groups at FLASH use higher odd harmonics (3rd and 5th) of the radiation in experiments. Some applications require knowledge of coherence properties of the radiation at he fundamental and higher harmonics. In this paper we presents results of the studies of coherence properties of the radiation from FLASH operating at radiation wavelength of 6.x nm at the fundamental harmonic, and higher odd harmonics (2.x nm and 1.x nm) at electron energy of 1 GeV.

WEPSO84

Present Status of Kyoto University Free Electron Laser

undulator, FEL, cavity, vacuum

711

H. Zen, M. Inukai, T. Kii, R. Kinjo, K. Masuda, K. Mishima, H. Negm, H. Ohgaki, K. Okumura, M. Omer, K. Torgasin, K. Yoshida
Kyoto University, Institute for Advanced Energy, Kyoto, Japan

A mid-infrared FEL named as KU-FEL (Kyoto University FEL) has been developed for energy related sciences [1]. After the achievement of the first lasing and the power saturation in 2008 [2, 3], we have been working to extend the tunable range of the FEL [4]. By replacing the original 1.6-m undulator into a 1.8 m one, the tunable range was expanded from 10-13 to 5-15 μm in January 2012. Then we fabricated a new undulator duct to reduce the minimum undulator gap from 20 to 15 mm. At 15-mm gap, the FEL gain can be expected to be twice as high as that at 20 mm gap. Commissioning of the new duct will be done in the end of this April. In this presentation, we will report on the result of the commissioning such as tunable range of KU-FEL and the estimated FEL gain, which would be compared with a simulation.
[1] H. Zen, et al., Infrared Phys. Techn., 51, 382 (2008)
[2] H. Ohgaki, et al., Proc. of FEL08, 4 (2008)
[3] H. Ohgaki, et al., Proc. of FEL2009, 572 (2009)
[4] H. Zen, et al., Proc. of FEL2012

THIANO01

Double Stage Seeded FEL with Fresh Bunch Injection Technique at FERMI

FEL, undulator, bunching, laser

723

E. Allaria, D. Castronovo, P. Cinquegrana, G. D'Auria, M. Dal Forno, M.B. Danailov, G. De Ninno, A.A. Demidovich, S. Di Mitri, B. Diviacco, W.M. Fawley, M. Ferianis, E. Ferrari, L. Fröhlich, G. Gaio, L. Giannessi, R. Ivanov, B. Mahieu, N. Mahne, I. Nikolov, F. Parmigiani, G. Penco, L. Raimondi, C. Serpico, P. Sigalotti, C. Spezzani, M. Svandrlik, C. Svetina, M. Trovò, M. Veronese, D. Zangrando, M. Zangrando
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
M. Dal Forno
DEEI, Trieste, Italy
G. De Ninno, D. Gauthier
University of Nova Gorica, Nova Gorica, Slovenia
E. Ferrari, F. Parmigiani
Università degli Studi di Trieste, Trieste, Italy
L. Giannessi
ENEA C.R. Frascati, Frascati (Roma), Italy
B. Mahieu
CEA/DSM/DRECAM/SPAM, Gif-sur-Yvette, France
M. Zangrando
IOM-CNR, Trieste, Italy

Seeding a FEL with an external coherent source has been extensively studied in the last decades as it can provide a way to enhance the radiation brightness and stability, with respect to that available from SASE. An efficient scheme for seed a VUV-soft x ray FEL uses, a powerful, long wavelength external laser to induce on the electron beam coherent bunching at the harmonics of the laser wavelength. When the bunching is further amplified by FEL interaction in the radiator, the scheme is called high gain harmonic generation (HGHG). The need of high power seed sources and of small energy spread are at the main limits for a direct extension of the HGHG scheme to short wavelengths. The fresh bunch scheme was proposed as a way to overcome these limitations; the scheme foresees the FEL radiation produced by one HGHG stage as an external seed in a second HGHG stage. We report the latest results obtained at FERMI that uses the two-stage HGHG scheme for generation of FEL pulses in the soft x-ray. A characterization of the FEL performance in terms of power, bandwidth and stability is reported. Starting from the FERMI results we will discuss extension of the scheme toward shorter wavelengths.

Slides THIANO01 [9.355 MB]

THOANO01

Stable Operation of HHG-Seeded EUV-FEL at the SCSS Test Accelerator

FEL, laser, feedback, undulator

728

H. Tomizawa, T. Hara, T. Ishikawa, K. Ogawa, H. Tanaka, T. Tanaka, T. Togashi, K. Togawa, M. Yabashi
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
M. Aoyama, K. Yamakawa
JAEA/Kansai, Kyoto, Japan
A. Iwasaki, S. Owada, T. Sato, K. Yamanouchi
The University of Tokyo, Tokyo, Japan
S. Matsubara, Y. Okayasu, T. Watanabe
JASRI/SPring-8, Hyogo, Japan
K. Midorikawa, E. Takahashi
RIKEN, Saitama, Japan

We performed the higher-order harmonic (HH) seeded FEL operation at a 61.2 nm fundamental wavelength, using a seeding source of HH pulses from a Ti:sapphire laser at the SCSS (EUV-FEL) accelerator. It is important for the HH seeded FEL scheme to synchronize the seeding laser pulses to the electron bunches. We constructed the relative arrival timing monitor based on Electro-Optic sampling (EOS). Since the EOS-probe laser pulses were optically split from HH-driving laser pulses, the arrival time difference of the seeding laser pulses, with respect to the electron bunches, were measured bunch-by-bunch. This non-invasive EOS monitor made uninterrupted, real-time monitoring possible even during the seeded FEL operation. The EOS system was used for the arrival timing feedback with a few-hundred-femtosecond adjustability for continual operation of the HH-seeded FEL. By using the EOS-locking system, the HH seeded FEL was operated over half a day with a 20-30% hit rate. The output pulse energy reached 20uJ at the 61.2 nm wavelength. A user experiment was performed by using the seeded EUV-EL and a clear difference between the SASE-FEL and the seeded FEL was observed.

Slides THOANO01 [11.493 MB]

THOBNO02

Transverse Gradient Undulators for a Storage Ring X-ray FEL Oscillator

FEL, undulator, storage-ring, emittance

740

R.R. Lindberg, K.-J. Kim
ANL, Argonne, USA
Y. Cai, Y. Ding, Z. Huang
SLAC, Menlo Park, California, USA

Funding: Work supported by U.S. Dept.~of Energy, Office of Basic Energy Sciences, Contract No.~DE-AC02-06CH11357.
An x-ray FEL oscillator (XFELO) is a fully coherent 4th generation source with complementary scientific applications to those based on self-amplified spontaneous emission*. While the naturally high repetition rate, intrinsic stability, and very small emittance produced by an ultimate storage ring (USR) makes it a potential candidate to drive an XFELO, the energy spread is typically an order of magnitude too large for sufficient gain. On the other hand, Smith and coworkers** showed how the energy spread requirement can be effectively mitigated with a transverse gradient undulator (TGU): since the TGU has a field strength that varies with transverse position, by properly correlating the electron energy with transverse position one can approximately satisfy the FEL resonance condition for all electrons. Motivated by recent work in the high-gain regime***, we investigate the utility of a TGU for low gain FELs at x-ray wavelengths. We find that a TGU may make an XFELO realizable in the largest ultimate storage rings now under consideration (e.g., in either the old Tevatron or PEP-II tunnel).
* K.-J. Kim, Y. Shvyd'ko and S. Reiche, PRL 100 244802 (2008).
** T. Smith, et al., J. Appl. Phys. 50, 4580 (1979).
*** Z. Huang, Y. Ding, and C.B. Schroeder, PRL 109, 204801 (2012).

Slides THOBNO02 [1.208 MB]

THOCNO04

Jitter-free Time Resolved Resonant CDI Experiments Using Two-color FEL Pulses Generated by the Same Electron Bunch

FEL, laser, undulator, polarization

753

M. Zangrando, E. Allaria, F. Bencivenga, F. Capotondi, D. Castronovo, P. Cinquegrana, M.B. Danailov, G. De Ninno, A.A. Demidovich, S. Di Mitri, B. Diviacco, W.M. Fawley, E. Ferrari, L. Fröhlich, L. Giannessi, R. Ivanov, M. Kiskinova, B. Mahieu, N. Mahne, C. Masciovecchio, I. Nikolov, E. Pedersoli, G. Penco, L. Raimondi, C. Serpico, P. Sigalotti, S. Spampinati, C. Spezzani, C. Svetina, M. Trovò
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
G. De Ninno, D. Gauthier
University of Nova Gorica, Nova Gorica, Slovenia
D. Fausti
Università degli Studi di Trieste, Trieste, Italy
L. Giannessi
ENEA C.R. Frascati, Frascati (Roma), Italy
M. Zangrando
IOM-CNR, Trieste, Italy

The generation of two-color FEL pulses by the same electron bunch at FERMI-FEL has opened unprecedented opportunity for jitter-free FEL pump-FEL probe time resolved coherent diffraction imaging (CDI) experiments in order to access spatial aspects in dynamic processes. This possibility was first explored in proof-of-principle resonant CDI experiments using specially designed sample consisting of Ti grating. The measurements performed tuning the energies of the FEL pulses to the Ti M-absorption edge clearly demonstrated the time dependence of Ti optical constants while varying the FEL-pump intensity and probe time delay. The next planned CDI experiments in 2013 will explore transient states in multicomponent nanostructures and magnetic systems, using the controlled linear or circular polarization of the two-color FEL pulses with temporal resolution in the fs to ps range.

Slides THOCNO04 [8.778 MB]