FEL2013 - List of Keywords (undulator)

Paper	Title	Other Keywords	Page
MOICNO01	Generation of a Train of Short Pulses by Means of FEL Emission of a Combed Electron Beam	electron, FEL, radiation, 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]

MOOCNO02	Multi-Objective Genetic Optimization for LCLS-II X-Ray FEL	emittance, simulation, linac, wakefield	12
	L. Wang, T.O. Raubenheimer SLAC, Menlo Park, California, USA
	The Linac Coherent Light Source II (LCLS-II) will build on the success of the world's most powerful X-ray laser, the Linac Coherent Light Source (LCLS). It will add two new X-ray laser beams and room for additional new instruments, greatly increasing the number of experiments carried out each year. Multiple operation modes are proposed to accommodate a variety of user requirements. There are a large number of variables and objectives in the design. For each operation mode, Multi-Objective Genetic Algorithm (MOGA) is applied to optimize the machine parameters in order to minimize the jitters, energy spread, collective effects and emittance. The optimal designs for various operation modes are presented in this paper. The phase and voltage of the linac RF, R56 at the two bunch compressors are optimized. The CSR (coherent synchrotron radiation) can induce large emittance growth, which is minimized by optimizing the phase advance between the compressor and the bend section. The final emittance at the beginning of the undulator is just about 1um and even lower.
	Slides MOOCNO02 [3.046 MB]

MOOCNO04	Using a Lienard-Wiechert Solver to Study Coherent Synchrotron Radiation Effects	radiation, simulation, electron, 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]

MOPSO04	Theoretical Analysis of a Laser Undulator-Based High Gain FEL	laser, FEL, electron, 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).

MOPSO08	Unaveraged Modelling of a LWFA Driven FEL	FEL, simulation, electron, radiation	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	FEL, electron, 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)

MOPSO30	Simple Setups for Carrier-envelope-phase Stable Single-cycle Attosecond Pulse Generation	electron, 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, FEL, radiation, electron	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]

MOPSO49	Numerical Accuracy When Solving the FEL Equations	FEL, simulation, electron, 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, electron, 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

MOPSO59	The Influence of the Magnetic Field Inhomogeneity on the Spontaneous Radiation and the Gain in the Plane Wiggler	electron, wiggler, laser, 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.

MOPSO65	Suppression of Wakefield Induced Energy Spread Inside an Undulator Through Current Shaping	wakefield, impedance, electron, 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.

MOPSO69	Free-Electron Lasers Driven by Laser-Plasma Accelerators Using Decompression or Dispersion	FEL, electron, 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.

MOPSO73	Suface Roughness Wakefield in FEL Undulator	wakefield, impedance, electron, 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, electron, 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).

MOPSO84	Numerical Investigations of Transverse Gradient Undulator Based Novel Light Sources	FEL, electron, laser, 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.

TUOCNO05	Design Concepts for a Next Generation Light Source at LBNL	FEL, linac, electron, laser	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]

TUPSO04	Simulations of a Corrugated Beam Pipe for the Chirp Compensation in SwissFEL	wakefield, laser, emittance, simulation	214
	S. Bettoni, P. Craievich, M. Pedrozzi, S. Reiche PSI, Villigen PSI, Switzerland
	In short wavelength FEL designs, bunch compression is obtained by making the beam passing through a magnetic chicane with an energy chirp typically of a percent level. At SwissFEL, before injection into the undulator it is foreseen to remove the residual chirp using the wakes in the C-band accelerating structures of the linac. This scheme works well for the hard X-ray undulator line, which includes the largest accumulation of wakefields, but it leaves a residual chirp in the other undulator line for the soft X-ray beam line, midway in the main linac. Another possibility to remove the residual chirp consists in using the longitudinal wakefields generated by a corrugated beam pipe, as recently proposed by G. Stupakov et al. Before planning a dechirper section in a FEL, an experimental verification of the analytical formulae describing the wakefields is crucial. The SwissFEL injector test facility (SITF) fulfils all the necessary criteria to perform such a proof of principle. We are investigating the technical implementation to perform an experiment in SITF in the second half of 2014. In this paper we present the tracking studies performed to optimize the experiment layout.

TUPSO14	Transverse Deflecting Structures for Bunch Length and Slice Emittance Measurements on SwissFEL	linac, emittance, diagnostics, FEL	236
	P. Craievich, R. Ischebeck, F. Löhl, G.L. Orlandi, E. Prat PSI, Villigen PSI, Switzerland
	The SwissFEL project, under development at the Paul Scherrer Institut, will produce FEL radiation in a wavelength range from 0.1 nm to 7 nm. The facility consists of an S-band rf-gun and booster, and a C-band main linac which accelerates the beam up to 5.8 GeV. Two magnetic chicanes will compress the beam between 2.5 fs rms and 25 fs rms depending on the operation mode. The bunch length and slice parameters will be measured after the first bunch compressor (330 MeV) by using an S-band transverse deflecting structure (TDS). A C-band TDS will be employed to measure the longitudinal parameters of the beam just upstream the undulator beamline (5.8 GeV). With the designed transverse beam optics, an integrated deflecting voltage of 70 MV is required in order to achieve a longitudinal resolution on the femtosecond time scale. In this paper we present the TDS measurement systems to be used at SwissFEL, with a particular emphasis on the new C-band device, including hardware, lattice layout and beam optics.

TUPSO22	Status of SwissFEL Undulator Lines	quadrupole, dipole, electron, 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 .

TUPSO25	Status of the EU-XFELl Laser Heater	laser, vacuum, electron, 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.

TUPSO41	The Ultrashort Beam Linac System and Proposed Coherent THz Radiation Sources at NSRRC	electron, radiation, linac, gun	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, electron, 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, electron, linac, 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.

TUPSO52	R&D Towards a Delta-type Undulator for the LCLS	vacuum, polarization, FEL, radiation	348
	H.-D. Nuhn, S.D. Anderson, G.B. Bowden, Y. Ding, G.L. Gassner, Z. Huang, E.M. Kraft, Yu.I. Levashov, F. Peters, F.E. Reese, J.J. Welch, Z.R. Wolf, J. Wu SLAC, Menlo Park, California, USA A.B. Temnykh Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	The LCLS generates linearly polarized, intense, high brightness x-ray pulses from planar fixed-gap undulators. While the fixed-gap design supports a very successful and tightly controlled alignment concept, it provides only limited taper capability (up to 1% through canted pole and horizontal position adjustability) and lacks polarization control. The latter is of great importance for soft x-ray experiments. A new compact undulator design (Delta) has been developed and tested with a 30-cm-long in-vacuum prototype at Cornell University, which adds those missing properties to the LCLS undulator design and is readily adapted to the LCLS alignment concept. Tuning Delta undulators within tight, FEL type tolerances is a challenge due to the fact that the magnetic axis and the magnet blocks are not easily accessible for measurements and tuning in the fully assembled state. An R&D project is underway to install a 3.2-m long out-of-vacuum device in place of the last LCLS undulator, to provide controllable levels of polarized radiation and to develop measurement and tuning techniques to achieve x-ray FEL type tolerances. Presently, the installation of the device is scheduled for August 2013.

TUPSO54	Undulators for Free Electron Lasers	electron, 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.

TUPSO60	Status of the Undulator Systems for the European X-ray Free Electron Laser	controls, laser, electron, 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	FEL, radiation, electron, 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.

TUPSO66	Transport of Terahertz-Wave Coherent Synchrotron Radiation With a Free-electron Laser Beamline at LEBRA	FEL, electron, radiation, 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.

TUPSO77	Analytical and Numerical Analysis of Electron Trajectories in a 3-D Undulator Magnetic Field	electron, 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.

TUPSO78	Design of a Collimation System for the Next Generation Light Source at LBNL	collimation, kicker, gun, linac	410
	C. Steier, P. Emma, H. Nishimura, C. F. Papadopoulos, H.J. Qian, F. Sannibale, C. Sun LBNL, Berkeley, California, USA
	Funding: This work is 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. The planned Next Generation Light Source at LBNL is designed to deliver MHz repetition rate electron beams to an array of free electron lasers. Because of the high beam power approaching one MW in such a facility, effective beam collimation is extremely important to minimize radiation damage, prevent quenches of superconducting cavities, limit dose rates outside of the accelerator tunnel and prevent equipment damage. We describe the conceptual design of a collimation system, including detailed simulations to verify its effectiveness.

WEIANO01	Towards Zeptosecond-scale Pulses From X-ray Free Electron Lasers	electron, FEL, radiation, 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	electron, target, laser, 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, electron, laser, radiation	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, electron, 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.

WEOCNO03	3-D Theory of a High Gain Free-Electron Laser Based on a Transverse Gradient Undulator	FEL, electron, 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, electron, 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, electron, 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, electron, laser, 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, electron, 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, electron, FEL, radiation	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, electron, 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.

WEPSO10	Increased Stability Requirements for Seeded Beams at LCLS	FEL, linac, klystron, electron	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, FEL, electron, 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.

WEPSO17	High-resolution Seeding Monochromator Design for NGLS	FEL, optics, electron, 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.

WEPSO20	Wake Monochromator in Asymmetric and Symmetric Bragg and Laue Geometry for Self-seeding the European X-ray FEL	FEL, photon, coupling, scattering	538
	G. Geloni, V. Kocharyan, E. Saldin, S. Serkez, M. Tolkiehn DESY, Hamburg, Germany
	We discuss the use of self-seeding schemes with wake monochromators to produce TW power, fully coherent pulses for applications at the dedicated bio-imaging bealine at the European X-ray FEL, a concept for an upgrade of the facility beyond the baseline previously proposed by the authors. We exploit the asymmetric and symmetric Bragg and Laue reflections (σ polarization) in diamond crystal. Optimization of the bio-imaging beamline is performed with extensive start-to-end simulations, which also take into account effects such as the spatio-temporal coupling caused by the wake monochromator. The spatial shift is maximal in the range for small Bragg angles. A geometry with Bragg angles close to pi/2 would be a more advantageous option from this viewpoint, albeit with decrease of the spectral tunability. We show that it will be possible to cover the photon energy range from 3 keV to 13 keV by using four different planes of the same crystal with one rotational degree of freedom.

WEPSO26	Status of the Flash Facility	photon, FEL, electron, 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, diagnostics, electron, 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).

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	photon, FEL, electron, 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.

WEPSO43	EEHG and Femtoslicing at DELTA	electron, 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.

WEPSO47	Simulation Results of Self-seeding Scheme in PAL-XFEL	radiation, electron, 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	FEL, electron, 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, electron	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, simulation, electron, 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	electron, FEL, radiation, 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)

WEPSO56	Optical Design and Time-dependent Wavefront Propagation Simulation for a Hard X-Ray Split- and delay-unit for the European XFEL	photon, simulation, FEL, instrumentation	627
	S. Roling, B. Siemer, F. Wahlert, M. Wöstmann, H. Zacharias Universität Muenster, Physikalisches Institut, Muenster, Germany S. Braun, P. Gawlitza Fraunhofer IWS, Dresden, Germany O.V. Chubar BNL, Upton, Long Island, New York, USA L. Samoylova, H. Sinn XFEL. EU, Hamburg, Germany E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany F. Siewert HZB, Berlin, Germany E. Ziegler ESRF, Grenoble, France
	For the European XFEL an x-ray split- and delay-unit (SDU) is built covering photon energies from 5 keV up to 20 keV. This SDU will enable time-resolved x-ray pump / x-ray probe experiments as well as sequential diffractive imaging on a femtosecond to picosecond time scale. The wavefront of the x-ray FEL pulses will be split by an edge of a silicon mirror coated with Mo/B4C and W/B4C multilayers. Both partial beams will then pass variable delay lines. For different wavelengths the angle of incidence onto the multilayer mirrors will be adjusted in order to match the Bragg condition. Hence, maximum delays between ± 2.5 ps at hν = 20 keV and up to ± 33 ps at hν = 5 keV will be possible. The time-dependent wave-optics simulations have been done with SRW software, for the fundamental and the 3rd harmonic. The XFEL radiation was simulated both in the Gaussian approximation as well as using an output of time-dependent SASE code FAST. Main features of the optical layout, including diffraction on the splitter edge, and optics imperfections were taken into account. Impact of these effects on the possibility to characterize spatial-temporal properties of FEL pulses are analyzed.

WEPSO57	Optimization of a Dedicated Bio-imaging Beamline at the European X-ray Fel	electron, 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.

WEPSO59	A Possible Upgrade of FLASH for Harmonic Lasing Down to 1.3 nm	FEL, electron, 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.

WEPSO60	A Method for Obtaining High Degree of Circular Polarization at X-ray FELs	FEL, radiation, bunching, polarization	651
	E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	Baseline design of many X-ray FEL undulators assumes a planar configuration which results in a linear polarization of SASE FEL radiation. However, many users experiments would profit from using a circularly polarized radiation. As a cheap upgrade one can consider an installation of a helical afterburner, but then one should have an efficient method to suppress linearly polarized background from the main undulator. In this paper we consider a new method for such a suppression which is illustrated with the parameters of the soft X-ray undulator SASE3 of the European X-ray FEL.

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, electron, 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	FEL, photon, electron, 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.

WEPSO67	Progress with the FERMI Laser Heater Commissioning	FEL, laser, linac, electron	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

WEPSO68	Effect of Coulomb Collisions on Echo-enabled Harmonic Generation	laser, bunching, scattering, FEL	684
	G.V. Stupakov SLAC, Menlo Park, California, USA
	Echo Enabled Harmonic Generation (EEHG) for FEL seeding is sensitive to the intrabeam scattering (IBS) effect. The reason for this is that in the process of generation high-harmonic density modulation in the beam the phase space evolves through a stage with narrow energy bands, which are characterized by the energy spread many times smaller than the beam energy spread. Energy diffusion caused by IBS tends to smear our these bands leading to diminished bunching factors at high harmonics. In the previous work [1] IBS in EEHG was studied in a simple model of a drift. This work extends the analysis of [1] to realistic lattices, and is applied to some of the existing practical designs of EEHG seeding. [1] G. Stupakov, Effect of Coulomb Collisions on Echo-Enabled Harmonic Generation (EEHG), in Proceedings of the 2011 FEL Conference, Shanghai, China, 2011.

WEPSO69	Optical Cavity Losses Calculation and Optimization of THz FEL with a Waveguide	coupling, FEL, cavity, radiation	689
	P. Tan, Q. Fu, L. Li, B. Qin, K. Xiong, Y.Q. Xiong HUST, Wuhan, People's Republic of China
	Funding: the Fundamental Research Funds for the Central Universities，HUST：2012QN080 The optical cavity with waveguide is used in most long wavelength free electron lasers. In this paper, the losses, gains and modes of a terahertz FEL sources in Huazhong Univeristy of Science and Technology(HUST) are analysis. Then the radii of curvature of the optical mirrors and shapes of the waveguide are optimized.

WEPSO78	Harmonic Lasing Self-seeded FEL	FEL, simulation, electron, 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, electron	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	FEL, electron, 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

WEPSO89	Design of a Resonator for the CSU THz FEL	FEL, higher-order-mode, coupling, radiation	719
	P.J.M. van der Slot Mesa+, Enschede, The Netherlands S. Biedron, S.V. Milton, P.J.M. van der Slot CSU, Fort Collins, Colorado, USA
	Funding: This research is support by Office of Naval Research Global, grant number N62909-10-1-7151 A 6-MeV L-band linac will be used to drive a planar, fixed gap, 2.5-cm period, hybrid undulator with parabolic pole faces. Consequently, this system is capable of generating wavelengths from 160 to 600 μm. In this paper we discuss the design of an optical resonator for this system. The resonator uses hole-coupled mirrors to allow for a straight electron beam line. The Rayleigh length, the position of the waist of the cold-cavity mode and the hole radii will be investigated to optimize the performance of the FEL.

THIANO01	Double Stage Seeded FEL with Fresh Bunch Injection Technique at FERMI	FEL, electron, 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, electron, laser, feedback	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]

THOBNO01	Three Unique FEL Designs for the Next Generation Light Source	FEL, photon, radiation, laser	734
	G. Penn, D. Arbelaez, J.N. Corlett, P. Emma, G. Marcus, S. Prestemon, M.W. Reinsch, R.B. Wilcox LBNL, Berkeley, California, USA A. Zholents ANL, Argonne, USA
	The NGLS is a next generation light source initiative spearheaded by the Lawrence Berkeley National Laboratory and based on an array of free-electron lasers (FEL) driven by a CW, 1-MHz bunch rate, superconducting linear accelerator. The facility is being designed to produce high peak and high average brightness coherent soft x-rays in the wavelength range of 1-12 nm, with shorter wavelengths accessible in harmonics or in expansion FELs. The facility performance requirements are based on a wide spectrum of scientific research objectives, requiring high flux, narrow-to-wide bandwidth, broad wavelength tunability, femtosecond pulse durations, and two-color pulses with variable relative timing and polarization, all of which cannot be encompassed in one FEL design. In addition, the cost of the facility requires building in a phased approach with perhaps three initial FELs and up to 9-10 FELs in the long term. We describe three very unique and complimentary FEL designs here as candidates for the first NGLS configuration.
	Slides THOBNO01 [1.331 MB]

THOBNO02	Transverse Gradient Undulators for a Storage Ring X-ray FEL Oscillator	FEL, electron, 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, electron, laser, 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]

Paper

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Other Keywords

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MOICNO01

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

electron, FEL, radiation, 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]

MOOCNO02

Multi-Objective Genetic Optimization for LCLS-II X-Ray FEL

emittance, simulation, linac, wakefield

12

L. Wang, T.O. Raubenheimer
SLAC, Menlo Park, California, USA

The Linac Coherent Light Source II (LCLS-II) will build on the success of the world's most powerful X-ray laser, the Linac Coherent Light Source (LCLS). It will add two new X-ray laser beams and room for additional new instruments, greatly increasing the number of experiments carried out each year. Multiple operation modes are proposed to accommodate a variety of user requirements. There are a large number of variables and objectives in the design. For each operation mode, Multi-Objective Genetic Algorithm (MOGA) is applied to optimize the machine parameters in order to minimize the jitters, energy spread, collective effects and emittance. The optimal designs for various operation modes are presented in this paper. The phase and voltage of the linac RF, R56 at the two bunch compressors are optimized. The CSR (coherent synchrotron radiation) can induce large emittance growth, which is minimized by optimizing the phase advance between the compressor and the bend section. The final emittance at the beginning of the undulator is just about 1um and even lower.

Slides MOOCNO02 [3.046 MB]

MOOCNO04

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

radiation, simulation, electron, 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]

MOPSO04

Theoretical Analysis of a Laser Undulator-Based High Gain FEL

laser, FEL, electron, 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).

MOPSO08

Unaveraged Modelling of a LWFA Driven FEL

FEL, simulation, electron, radiation

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

FEL, electron, 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)

MOPSO30

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

electron, 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, FEL, radiation, electron

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]

MOPSO49

Numerical Accuracy When Solving the FEL Equations

FEL, simulation, electron, 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, electron, 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

MOPSO59

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

electron, wiggler, laser, 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.

MOPSO65

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

wakefield, impedance, electron, 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.

MOPSO69

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

FEL, electron, 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.

MOPSO73

Suface Roughness Wakefield in FEL Undulator

wakefield, impedance, electron, 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, electron, 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).

MOPSO84

Numerical Investigations of Transverse Gradient Undulator Based Novel Light Sources

FEL, electron, laser, 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.

TUOCNO05

Design Concepts for a Next Generation Light Source at LBNL

FEL, linac, electron, laser

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]

TUPSO04

Simulations of a Corrugated Beam Pipe for the Chirp Compensation in SwissFEL

wakefield, laser, emittance, simulation

214

S. Bettoni, P. Craievich, M. Pedrozzi, S. Reiche
PSI, Villigen PSI, Switzerland

In short wavelength FEL designs, bunch compression is obtained by making the beam passing through a magnetic chicane with an energy chirp typically of a percent level. At SwissFEL, before injection into the undulator it is foreseen to remove the residual chirp using the wakes in the C-band accelerating structures of the linac. This scheme works well for the hard X-ray undulator line, which includes the largest accumulation of wakefields, but it leaves a residual chirp in the other undulator line for the soft X-ray beam line, midway in the main linac. Another possibility to remove the residual chirp consists in using the longitudinal wakefields generated by a corrugated beam pipe, as recently proposed by G. Stupakov et al. Before planning a dechirper section in a FEL, an experimental verification of the analytical formulae describing the wakefields is crucial. The SwissFEL injector test facility (SITF) fulfils all the necessary criteria to perform such a proof of principle. We are investigating the technical implementation to perform an experiment in SITF in the second half of 2014. In this paper we present the tracking studies performed to optimize the experiment layout.

TUPSO14

Transverse Deflecting Structures for Bunch Length and Slice Emittance Measurements on SwissFEL

linac, emittance, diagnostics, FEL

236

P. Craievich, R. Ischebeck, F. Löhl, G.L. Orlandi, E. Prat
PSI, Villigen PSI, Switzerland

The SwissFEL project, under development at the Paul Scherrer Institut, will produce FEL radiation in a wavelength range from 0.1 nm to 7 nm. The facility consists of an S-band rf-gun and booster, and a C-band main linac which accelerates the beam up to 5.8 GeV. Two magnetic chicanes will compress the beam between 2.5 fs rms and 25 fs rms depending on the operation mode. The bunch length and slice parameters will be measured after the first bunch compressor (330 MeV) by using an S-band transverse deflecting structure (TDS). A C-band TDS will be employed to measure the longitudinal parameters of the beam just upstream the undulator beamline (5.8 GeV). With the designed transverse beam optics, an integrated deflecting voltage of 70 MV is required in order to achieve a longitudinal resolution on the femtosecond time scale. In this paper we present the TDS measurement systems to be used at SwissFEL, with a particular emphasis on the new C-band device, including hardware, lattice layout and beam optics.

TUPSO22

Status of SwissFEL Undulator Lines

quadrupole, dipole, electron, 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 .

TUPSO25

Status of the EU-XFELl Laser Heater

laser, vacuum, electron, 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.

TUPSO41

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

electron, radiation, linac, gun

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, electron, 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, electron, linac, 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.

TUPSO52

R&D Towards a Delta-type Undulator for the LCLS

vacuum, polarization, FEL, radiation

348

H.-D. Nuhn, S.D. Anderson, G.B. Bowden, Y. Ding, G.L. Gassner, Z. Huang, E.M. Kraft, Yu.I. Levashov, F. Peters, F.E. Reese, J.J. Welch, Z.R. Wolf, J. Wu
SLAC, Menlo Park, California, USA
A.B. Temnykh
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

The LCLS generates linearly polarized, intense, high brightness x-ray pulses from planar fixed-gap undulators. While the fixed-gap design supports a very successful and tightly controlled alignment concept, it provides only limited taper capability (up to 1% through canted pole and horizontal position adjustability) and lacks polarization control. The latter is of great importance for soft x-ray experiments. A new compact undulator design (Delta) has been developed and tested with a 30-cm-long in-vacuum prototype at Cornell University, which adds those missing properties to the LCLS undulator design and is readily adapted to the LCLS alignment concept. Tuning Delta undulators within tight, FEL type tolerances is a challenge due to the fact that the magnetic axis and the magnet blocks are not easily accessible for measurements and tuning in the fully assembled state. An R&D project is underway to install a 3.2-m long out-of-vacuum device in place of the last LCLS undulator, to provide controllable levels of polarized radiation and to develop measurement and tuning techniques to achieve x-ray FEL type tolerances. Presently, the installation of the device is scheduled for August 2013.

TUPSO54

Undulators for Free Electron Lasers

electron, 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.

TUPSO60

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

controls, laser, electron, 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

FEL, radiation, electron, 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.

TUPSO66

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

FEL, electron, radiation, 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.

TUPSO77

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

electron, 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.

TUPSO78

Design of a Collimation System for the Next Generation Light Source at LBNL

collimation, kicker, gun, linac

410

C. Steier, P. Emma, H. Nishimura, C. F. Papadopoulos, H.J. Qian, F. Sannibale, C. Sun
LBNL, Berkeley, California, USA

Funding: This work is 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.
The planned Next Generation Light Source at LBNL is designed to deliver MHz repetition rate electron beams to an array of free electron lasers. Because of the high beam power approaching one MW in such a facility, effective beam collimation is extremely important to minimize radiation damage, prevent quenches of superconducting cavities, limit dose rates outside of the accelerator tunnel and prevent equipment damage. We describe the conceptual design of a collimation system, including detailed simulations to verify its effectiveness.

WEIANO01

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

electron, FEL, radiation, 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

electron, target, laser, 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, electron, laser, radiation

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, electron, 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.

WEOCNO03

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

FEL, electron, 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, electron, 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, electron, 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, electron, laser, 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, electron, 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, electron, FEL, radiation

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, electron, 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.

WEPSO10

Increased Stability Requirements for Seeded Beams at LCLS

FEL, linac, klystron, electron

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, FEL, electron, 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.

WEPSO17

High-resolution Seeding Monochromator Design for NGLS

FEL, optics, electron, 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.

WEPSO20

Wake Monochromator in Asymmetric and Symmetric Bragg and Laue Geometry for Self-seeding the European X-ray FEL

FEL, photon, coupling, scattering

538

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

We discuss the use of self-seeding schemes with wake monochromators to produce TW power, fully coherent pulses for applications at the dedicated bio-imaging bealine at the European X-ray FEL, a concept for an upgrade of the facility beyond the baseline previously proposed by the authors. We exploit the asymmetric and symmetric Bragg and Laue reflections (σ polarization) in diamond crystal. Optimization of the bio-imaging beamline is performed with extensive start-to-end simulations, which also take into account effects such as the spatio-temporal coupling caused by the wake monochromator. The spatial shift is maximal in the range for small Bragg angles. A geometry with Bragg angles close to pi/2 would be a more advantageous option from this viewpoint, albeit with decrease of the spectral tunability. We show that it will be possible to cover the photon energy range from 3 keV to 13 keV by using four different planes of the same crystal with one rotational degree of freedom.

WEPSO26

Status of the Flash Facility

photon, FEL, electron, 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, diagnostics, electron, 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).

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

photon, FEL, electron, 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.

WEPSO43

EEHG and Femtoslicing at DELTA

electron, 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.

WEPSO47

Simulation Results of Self-seeding Scheme in PAL-XFEL

radiation, electron, 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

FEL, electron, 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, electron

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, simulation, electron, 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

electron, FEL, radiation, 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)

WEPSO56

Optical Design and Time-dependent Wavefront Propagation Simulation for a Hard X-Ray Split- and delay-unit for the European XFEL

photon, simulation, FEL, instrumentation

627

S. Roling, B. Siemer, F. Wahlert, M. Wöstmann, H. Zacharias
Universität Muenster, Physikalisches Institut, Muenster, Germany
S. Braun, P. Gawlitza
Fraunhofer IWS, Dresden, Germany
O.V. Chubar
BNL, Upton, Long Island, New York, USA
L. Samoylova, H. Sinn
XFEL. EU, Hamburg, Germany
E. Schneidmiller, M.V. Yurkov
DESY, Hamburg, Germany
F. Siewert
HZB, Berlin, Germany
E. Ziegler
ESRF, Grenoble, France

For the European XFEL an x-ray split- and delay-unit (SDU) is built covering photon energies from 5 keV up to 20 keV. This SDU will enable time-resolved x-ray pump / x-ray probe experiments as well as sequential diffractive imaging on a femtosecond to picosecond time scale. The wavefront of the x-ray FEL pulses will be split by an edge of a silicon mirror coated with Mo/B4C and W/B4C multilayers. Both partial beams will then pass variable delay lines. For different wavelengths the angle of incidence onto the multilayer mirrors will be adjusted in order to match the Bragg condition. Hence, maximum delays between ± 2.5 ps at hν = 20 keV and up to ± 33 ps at hν = 5 keV will be possible. The time-dependent wave-optics simulations have been done with SRW software, for the fundamental and the 3rd harmonic. The XFEL radiation was simulated both in the Gaussian approximation as well as using an output of time-dependent SASE code FAST. Main features of the optical layout, including diffraction on the splitter edge, and optics imperfections were taken into account. Impact of these effects on the possibility to characterize spatial-temporal properties of FEL pulses are analyzed.

WEPSO57

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

electron, 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.

WEPSO59

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

FEL, electron, 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.

WEPSO60

A Method for Obtaining High Degree of Circular Polarization at X-ray FELs

FEL, radiation, bunching, polarization

651

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

Baseline design of many X-ray FEL undulators assumes a planar configuration which results in a linear polarization of SASE FEL radiation. However, many users experiments would profit from using a circularly polarized radiation. As a cheap upgrade one can consider an installation of a helical afterburner, but then one should have an efficient method to suppress linearly polarized background from the main undulator. In this paper we consider a new method for such a suppression which is illustrated with the parameters of the soft X-ray undulator SASE3 of the European X-ray FEL.

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, electron, 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

FEL, photon, electron, 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.

WEPSO67

Progress with the FERMI Laser Heater Commissioning

FEL, laser, linac, electron

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

WEPSO68

Effect of Coulomb Collisions on Echo-enabled Harmonic Generation

laser, bunching, scattering, FEL

684

G.V. Stupakov
SLAC, Menlo Park, California, USA

Echo Enabled Harmonic Generation (EEHG) for FEL seeding is sensitive to the intrabeam scattering (IBS) effect. The reason for this is that in the process of generation high-harmonic density modulation in the beam the phase space evolves through a stage with narrow energy bands, which are characterized by the energy spread many times smaller than the beam energy spread. Energy diffusion caused by IBS tends to smear our these bands leading to diminished bunching factors at high harmonics. In the previous work [1] IBS in EEHG was studied in a simple model of a drift. This work extends the analysis of [1] to realistic lattices, and is applied to some of the existing practical designs of EEHG seeding.
[1] G. Stupakov, Effect of Coulomb Collisions on Echo-Enabled Harmonic Generation (EEHG), in Proceedings of the 2011 FEL Conference, Shanghai, China, 2011.

WEPSO69

Optical Cavity Losses Calculation and Optimization of THz FEL with a Waveguide

coupling, FEL, cavity, radiation

689

P. Tan, Q. Fu, L. Li, B. Qin, K. Xiong, Y.Q. Xiong
HUST, Wuhan, People's Republic of China

Funding: the Fundamental Research Funds for the Central Universities，HUST：2012QN080
The optical cavity with waveguide is used in most long wavelength free electron lasers. In this paper, the losses, gains and modes of a terahertz FEL sources in Huazhong Univeristy of Science and Technology(HUST) are analysis. Then the radii of curvature of the optical mirrors and shapes of the waveguide are optimized.

WEPSO78

Harmonic Lasing Self-seeded FEL

FEL, simulation, electron, 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, electron

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

FEL, electron, 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

WEPSO89

Design of a Resonator for the CSU THz FEL

FEL, higher-order-mode, coupling, radiation

719

P.J.M. van der Slot
Mesa+, Enschede, The Netherlands
S. Biedron, S.V. Milton, P.J.M. van der Slot
CSU, Fort Collins, Colorado, USA

Funding: This research is support by Office of Naval Research Global, grant number N62909-10-1-7151
A 6-MeV L-band linac will be used to drive a planar, fixed gap, 2.5-cm period, hybrid undulator with parabolic pole faces. Consequently, this system is capable of generating wavelengths from 160 to 600 μm. In this paper we discuss the design of an optical resonator for this system. The resonator uses hole-coupled mirrors to allow for a straight electron beam line. The Rayleigh length, the position of the waist of the cold-cavity mode and the hole radii will be investigated to optimize the performance of the FEL.

THIANO01

Double Stage Seeded FEL with Fresh Bunch Injection Technique at FERMI

FEL, electron, 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, electron, laser, feedback

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]

THOBNO01

Three Unique FEL Designs for the Next Generation Light Source

FEL, photon, radiation, laser

734

G. Penn, D. Arbelaez, J.N. Corlett, P. Emma, G. Marcus, S. Prestemon, M.W. Reinsch, R.B. Wilcox
LBNL, Berkeley, California, USA
A. Zholents
ANL, Argonne, USA

The NGLS is a next generation light source initiative spearheaded by the Lawrence Berkeley National Laboratory and based on an array of free-electron lasers (FEL) driven by a CW, 1-MHz bunch rate, superconducting linear accelerator. The facility is being designed to produce high peak and high average brightness coherent soft x-rays in the wavelength range of 1-12 nm, with shorter wavelengths accessible in harmonics or in expansion FELs. The facility performance requirements are based on a wide spectrum of scientific research objectives, requiring high flux, narrow-to-wide bandwidth, broad wavelength tunability, femtosecond pulse durations, and two-color pulses with variable relative timing and polarization, all of which cannot be encompassed in one FEL design. In addition, the cost of the facility requires building in a phased approach with perhaps three initial FELs and up to 9-10 FELs in the long term. We describe three very unique and complimentary FEL designs here as candidates for the first NGLS configuration.

Slides THOBNO01 [1.331 MB]

THOBNO02

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

FEL, electron, 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, electron, laser, 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]