• G. Geloni, V. Kocharyan, E. Saldin, E. Schneidmiller, M.V. Yurkov
  DESY, Hamburg

In this paper we exploit a formalism to describe Edge Radiation, which relies on Fourier Optics techniques, described in another contribution to this conference. First, we apply our method to develop an analytical model to describe Edge Radiation in the presence of a vacuum chamber. Such model is based on the solution of the field equation with a tensor Green's function technique. In particular, explicit calculations for a circular vacuum chamber are reported. Second, we consider the use of Edge Radiation as a tool for electron beam diagnostics. We discuss coherent Edge Radiation, extraction of Edge Radiation by a mirror, and other issues becoming important at high electron energy and long radiation wavelength. Based on this work we also study the impact of Edge Radiation on XFEL setups and we discuss recent results.

• Y. Li, W. Decking, B. Faatz, J. Pflüger
  DESY, Hamburg

At the European XFEL circular polarized radiation in the wavelength range 0.4-1.6 nm is highly desired. An economically and technically convenient method is to utilize a long planar undulator to pre-bunch electron beam first and then pass it through a shorter and specially designed undulator to generate arbitrary polarized radiation. Between these two parts, the electrons and the radiation from the long undulator must be spatially separated by a bend. In this paper, a solution for an isochronous bend is presented considering nonlinear aberrations, which preserves theμbunching even for the 0.4 nm case.

• H. Delsim-Hashemi, V. Miltchev, J. Roßbach
  Uni HH, Hamburg
• Y. Holler, A. Schöps, M. Tischer
  DESY, Hamburg
• I. Vasserman
  ANL, Argonne

A seeded free-electron laser (FEL) experiment at VUV wavelengths, called sFLASH will be installed at the existing SASE-FEL user facility FLASH until Spring 2010. Seed pulses at wavelengths around 30 nm and 13 nm from high harmonic generation (HHG) will interact with the electron beam in sFLASH undulators upstream of the existing SASE undulator section. In this paper, status of the sFLASH undulators are described.

• V. Miltchev, A. Azima, J. Bödewadt, F. Curbis, H. Delsim-Hashemi, M. Drescher, Th. Maltezopoulos, M. Mittenzwey, J. Roßbach, R. Tarkeshian, M. Wieland
  Uni HH, Hamburg
• S. Düsterer, J. Feldhaus, T. Laarmann, H. Schlarb
  DESY, Hamburg
• R. Ischebeck
  PSI, Villigen
• S. Khan
  DELTA, Dortmund
• A. Meseck
  Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin

The Free-electron-laser at Hamburg (FLASH) operates in the Self-Amplified Spontaneous Emission (SASE) mode, delivering to users photons in the XUV wavelength range. The FEL seeding schemes promise to improve the properties of the generated radiation in terms of stability in intensity and time. Such an experiment using higher harmonics of an optical laser as a seed is currently under construction at FLASH. The installation of the XUV seeding experiment (sFLASH) is going to take place in fall 2009. This includes mounting of new variable-gap undulators upstream of the existing SASE-undulators, building the XUV-seed source as well as installation of additional photon diagnostics and electron beam instrumentation. In this contribution the layout of sFLASH will be discussed together with the technical design of its major components.

• G. Fuchert, T. Baumbach, A. Bernhard, S. Ehlers, P. Peiffer, D. Wollmann
  KIT, Karlsruhe
• R. Rossmanith
  FZK, Karlsruhe

In addition to large synchrotron radiation and FEL facilities, smaller and cheaper intense UV and X-ray facilities are needed (so-called table-top sources). The electron beam for such a table-top source could be provided by a laser wakefield accelerator. Despite dramatic improvements during the last years on stability and intensity of those devices, one disadvantage remains: the energy spread of the electron beam is in the range of several percent, leading to an energy spread of the photon beam emitted by a conventional undulator. In this paper ideas for new designs of superconductive undulators are presented, which can produce an almost monochromatic photon beam out of an electron beam with a relatively large energy spread.

• H. S. Marks, J. Dadoun, O. Faingersh, Kh. Garb, A. Gover
  University of Tel-Aviv, Faculty of Engineering, Tel-Aviv
• B.Yu. Kapilevich, B. Litvak
  Ariel University Center of Samaria, Faculty of Engineering, Ariel

The design, operating principles, and results of characterization for a novel resonator are outlined. Measurements were conducted prior to insertion into the Wiggler cavity for future testing under lasing. The W-band (75-110 GHz) resonator consists of two Talbot splitters and two confocal cylindrical mirrors for decoupling the electron beam from the radiation, a corrugated waveguide, and an adjustable three grid reflector system. Two degrees of freedom have been built into the grid system, firstly, the central grid can be rotated via remote control to alter the out-coupling coefficient, and secondly, also using a motor it is possible to remotely move the grid system back and forth altering the length of the resonator. Allowing continuous tuning of the longitudinal mode resonant frequencies (spaced about 100MHz apart). The radiation pattern of the resonator mode is nearly a Gaussian. The round trip reflectivity and its Q factors where measured by matching the S parameters of the device (measured with a Scalar VNA) to the theoretical Fabry-Perot resonator reflection and transmission curves. Based on this estimate the roundtrip losses of the tunable resonator are less than 35%.

• H. S. Marks, E. Dyunin, A. Gover, M. Volshonok
  University of Tel-Aviv, Faculty of Engineering, Tel-Aviv
• Y. Lasser, R. Shereshevsky, A. Yahalom
  Ariel University Center of Samaria, Faculty of Engineering, Ariel

Deviations in the electron beam trajectory through the planar wiggler of the Israeli Electrostatic Accelerator FEL were found to be primarily caused by small variations in the strength and angle of polarisation of lateral focussing bar magnets which are positioned on both sides of the wiggler, and provide a quadrupole guiding field on axis. The field of the wiggler on axis was measured using a Labview controlled automated system built in our lab, based on a 2-axis Hall Effect magnetic sensor driven by a stepper motor. Polarisation field components of the individual focussing magnets were measured separately. Then, using an algorithm, the focussing magnets were paired, such that their non-uniformities were utilised to not only cancel out each other's error, but also to cancel out the field errors on axis due to variation in strength and polarisation angle of the wiggler magnets. The quality of the predicted electron beam transport was evaluated by 3-D simulation with the General Particle Tracer code which allowed the input of all the measured fields.

• L. Catani, A. Cianchi, D. Di Giovenale
  INFN-Roma II, Roma
• F. Broggi
  INFN/LASA, Segrate (MI)
• G. Di Pirro
  INFN/LNF, Frascati (Roma)

Beam Loss Position Monitors (BLPM) are diagnostic systems that, by detecting anomalies in the quantity of particles in proximity of the beam pipe, can give hint of accidental interaction of beam with vacuum pipe caused by beam lost particles providing also information on the position where the loss originated. This paper describes the design and characterization of the BLPM system proposed for the SPARC accelerator providing real-time information on the intensity and position of beam losses that might occur along the undulator section. The BLPM system will consist of optic fibers aligned to the undulator hanging few centimeters from the beam pipe. Solid state MPPC from Hamamatsu will be used to convert the Cerenkov light produced by electrons traversing the fiber into a proportional time dependent signal. By analyzing its temporal structure and by comparing the intensities between the signals from different fibers information about the sources of the beam losses can be obtained.

• S.M. Matsubara, A. Higashiya, N. Hosoda, S.I. Inoue, H. Maesaka, M. Nagasono, T. Ohshima, Y. Otake, K. Tamasaku, M. Yabashi
  RIKEN/SPring-8, Hyogo
• T. Togashi
  JASRI/SPring-8, Hyogo-ken

The SCSS test accelerator was constructed and user experiments using SASE-FEL light in an extreme-ultraviolet (EUV) region have been performed at SPring-8. It is necessary to distribute an accurate timing signal both to accelerator components and experimental instruments. We developed a trigger system targeted as a timing jitter of less than 100 fs. The jitter of the time difference between the reference timing signal and a beam-induced signal from an RF BPM cavity was measured. The jitter value was nearly 50 fs in rms. However, this value was measured with electron beams after C-band accelerator cavities and not measured with the SASE light pulses at the experimental end station. Therefore, we employed an in-vacuum fast photo diode in order to directly observe EUV light at a 60 nm and to detect the arrival timing at the end station. The measured time jitter was 2.5 ps in rms, which was limited by the photo diode. Even thorough the resolution of the time jitter did not reach to 50 fs, the system is still usable to verify trigger delay values for user experiments. This fast timing measurement using the in-vacuum photo diode is still a pioneer of optical technology in an FEL field.

• T. Tanaka
  RIKEN/SPring-8, Hyogo

In order to achieve FEL lasing in an x-ray region, the undulator should be long enough for saturation and thus consists of a large number of segments. Such segmention can cause nonnegligible errors degrading the FEL gain, such as the phase mismatching, K-value discrepancy between segments and trajectory error. The undulator commissioning, i.e., tuning of the components in the undulator system to correct these errors, is cruicially important. In the SPring-8 XFEL, the undulator commissioning is to be made in two steps. Firstly, optical properties of spontaneous radiation from two adjacent undulator segments are measured to specify the error sources between the two segments, which will be corrected accordingly. Secondly, the intensity of FEL radiation is monitored to adjust the components more accurately. In this paper, results of calculation and simulation for spontaneous and FEL radiation with possible error sources in SPring-8 XFEL are reported together with consideration on the correction accuracy.

• E.J. Minehara
  WERC, Tsuruga , Fukui

A compact cryogenic ERL-FEL(energy-recovery linac based Free-electron laser) should be usable for laser cleaning applications in radio-isotope contaminated nuclear power reactors in the world. A new compact zero-boil off(ZBO) superconducting accelerating cavity module like the JAEA FEL machines will be discussed and optimized to realize the easy operation and free-maintenance for nuclear power and other industries. We will firstly make such a high peak and high average power ERL-FEL to realize all of them. The ERL-FEL will be used near future for decommissioning nuclear power plants and other purposes in heavy metal industries.

• F. Hellberg, H. Danared, A. Hedqvist
  MSL, Stockholm
• Y. Holler, B. Krause, A. Petrov, J. Pflüger
  DESY, Hamburg

A rotating coil system has been set-up at the Manne-Siegbahn Laboratory to characterize the XFEL undulator quadrupoles with respect to magnetic center stability. In combination with a coordinate measuring machine the position of the magnetic center with respect to fiducials is measured. The rotating coil system has previously been used to measure the magnetic center stability with respect to magnet excitation for two prototype magnets with yokes of different materials [1]. That work has now been extended to a third material for the yoke. Here the results from measurements of the prototype magnets are presented together with results from test measurements performed to determine the accuracy of the fiducialization process.

[1] F. Hellberg et al, "Investigation of Quadrupole Magnets for the XFEL Project Using a Rotating Coil Set-up", FEL08, TUPPH044, Gyeongju, Korea, 2008

• M.A. Bowler
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• B. Faatz, K.I. Tiedtke
  DESY, Hamburg
• F. Siewert
  BESSY GmbH, Berlin

Imperfections on the surfaces of the optical components of photon transport systems can degrade the quality of the radiation, causing amongst other effects structure in the transverse beam profile. This effect is being investigated for one of the beamlines at FLASH. The FEL mirror surfaces have been measured in the metrology laboratory at Helmholtz Zentrum Berlin / BESSY-II, and these data are input into wavefront propagation calculations, which model the transport of the radiation field from the exit of the FEL across the optics to the experiment. The input fields for the propagation were generated using the Genesis1.3 code. This work is part of collaboration in the IRUVX-PP consortium.

• F. Jackson, D. Angal-Kalinin, J.-L. Fernandez-Hernando, B.D. Muratori
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire

The next generation light source for the UK requires transport, collimation and dumping of high power, high quality beams. The accelerated beam must be transported to several different FELs. A design for the post-linac beam collimation, spreader (including diagnostics), and dump is presented.

• M.D. Roper
  STFC/DL, Daresbury, Warrington, Cheshire

The initial three FELs for the proposed UK NLS facility will cover the soft x-ray range 50 to 1000 eV in the fundamental and up to 5000 eV in the 3rd to 5th harmonics. The FELs will be seeded to produce pulse lengths of ~20 fs FWHM, equivalent to a transform limited bandwidth of ~0.1 eV. Whilst spectral filtering of the FEL pulses will not always be necessary, reasons for passing the FEL beam through a monochromator include: removing unwanted spectral content produced by SASE or spontaneous emission but without lengthening the pulse, improving the spectral resolving power from the inherent pulse bandwidth, and removing the fundamental radiation when using the harmonics. In this paper, a grating based monochromator is described that fulfills all three roles. It is based on the SX700 type of monochromator that uses a variable-included-angle plane-grating operating in collimated light. This flexible design allows different modes of operation optimised for minimising temporal stretch of the pulse or for achieving high spectral resolving power. The performance of a beamline operating over the fundamental range of NLS FEL2 (250 to 850 eV) and the harmonics to 2000 eV is calculated.

• N.M. Kelez, Y.D. Chuang, R.M. Duarte, D.E. Lee, W.R. McKinney, V.V. Yashchuk, S.S. Yuan
  LBNL, Berkeley, California
• J.D. Bozek
  SLAC, Menlo Park, California

There is an increasing demand for highly de-magnified and well-focused beams with high quality imaging of the full field to further explore the potential of novel instruments. For beamlines operating at a focal point, mechanical benders have often been used to shape the refocusing mirror into an ideal elliptical cylinder. However, the limited number of couplings for these mechanisms requires specific substrate side-shaping, often calculated using beam bending theory, to meet demanding figure requirements. Here, we use finite element analysis (FEA) to both validate the side-shaping algorithm and then couple the output with SHADOW and a bender couple optimization algorithm to evaluate the resulting mirror figure and ultimately improve the mechanical design. Finally, the metrology results of the Long Trace Profiler (LTP) are used to both set the final shape of the completed assembly and validate the model and analysis methods.

• A. Novokhatski
  SLAC, Menlo Park, California

An ultra short bunch is used in the LCLS operation. The bunch is prepared, compressed and accelerated in the main part of the machine, which includes an injector, two bunch compressors and a linac. A feedback system precisely controls the bunch energy before it enters a 300 m long beam transport beam line (LTU). In this line and later in the undulator section (132 m long) the bunch may loss energy due to wake field radiation. Additionally, wake fields may add a significant linear energy spread to the bunch which has to be compensated at an early stage in the linac. The energy loss has to be compensated by varying the K-parameter of the undulators. This means that a precise knowledge of the wake fields in this part of the machine is very important. Resistive wake fields are known and well calculated. We discuss an additional part of the wake fields, which comes from the different vacuum elements like bellows, BPMs, transitions, vacuum ports, vacuum valves and other elements. We use the code NOVO and include analytical estimations for the wake potential calculations. We show that the bunch energy losses due to these elements are about 20% of the total wake field losses.

• J. Vollaire, A.F. Fassó, J.C. Liu, X.S. Mao, A.A. Prinz, S.H. Rokni, M. Santana-Leitner
  SLAC, Menlo Park, California

The Front End Enclosure (FEE) of the Linac Coherent Light Source (LCLS) is a shielding housing located between the electron dump area and the first experimental hutch. The upstream part of the FEE hosts the commissioning diagnostic for the FEL beam. In the downstream part of the FEE, two sets of grazing incidence mirror and several collimators are used to direct the beam to one of the experimental station and reduce the bremsstrahlung background and the hard component of the spontaneous radiation spectrum. This paper addresses beam loss assumption, the design limits and the simulations performed using the Monte-Carlo code FLUKA for the design of the shielding necessary to attenuate secondary radiations (including muons) induced by the bremsstrahlung photons. Other Radiation Safety Systems associated to the containment of the FEL beam and an overview of the Personnel Protection system is provided for completeness.

• D. Li, K. Imasaki
  ILT, Suita, Osaka
• S. Amano, K. Horikawa, S. Miyamoto, T. Mochizuki
  NewSUBARU/SPring-8, Laboratory of Advanced Science and Technology for Industry (LASTI), Hyogo

Transmutation is considered as an approach by reducing the radioactive life of the nuclear waste through converting the nuclei of long-lived activity to its corresponding isotope of short-lived activity. High-energy photons can induce nuclear reaction, which is regarded as an approach to make transmutation. Laser Compton scattering (LCS) gamma ray seems a good photons source. The LCS gamma ray is generated from the collision of a laser light to a high-energy electron beam, and it holds a peak in the energy spectrum, which can well overlap the peak of nuclear giant resonance and hence realize a good coupling. I¹²⁹ has a very long life of more than 16 million years and a high chemical activity. Besides these, Iodine is hard to include in the normal reposing container due to their low temperature boiling point. So Iodine is recognized as discrete waste for transmutation. The reaction rate of transmutation plays an important role in this proposal of deposing nuclear waste; therefore, the aim of this paper is to experimentally investigate the reaction rate of Iodine.

• F. Shishikura, K. Ishikawa
  Nihon University School of Medicine, Tokyo
• K. Hayakawa, Y. Hayakawa, T. Kuwada, K. Nakao, K. Nogami, T. Tanaka
  LEBRA, Funabashi
• M. Inagaki, T. Sakai, I. Sato
  Nihon University, Advanced Research Institute for the Sciences and Humanities, Funabashi

The Free-Electron Laser (FEL) of LEBRA[1] produces near infrared FELs (IR FELs) including tunable wavelength from 1 to 6 microns. The higher harmonics generated by means of the nonlinear optical crystals are also available with output energy of about 0.5 mJ/micro-pulse. The IR FELs of LEBRA are of significant interest because these tunable wavelengths covered with visible and near infrared regions (350 nm-6000 nm) expect to unveil photochemical reactions of bio-macromolecules even in living organisms. We use LEBRA IR FELs for macromolecules such as caronmonoxy hemoglobin (COHb), whose maximum absorption spectra are known as Soret band (418 nm) and two weaker bands (538 nm and 568 nm). We first selected three of the visible wavelengths. After irradiation (up to about 10 J), the each effect of three wavelengths on COHb was separately investigated by several methods icluding visible scanning absorption spectroscopy and Raman microscopy. We report the present results on the mesurements.

[1] Laboratory for Electron Beam Research and Application, Institute of Quantum Science, Nihon University.

• A. Afanasev, R.R. Ramdon
  Hampton University, Hampton, Virginia
• O.K. Baker, P. Slocum
  Yale University, Physics Department, New Haven, CT
• K.B. Beard
  Muons, Inc, Batavia
• G.H. Biallas, J.R. Boyce, M.D. Shinn
  JLAB, Newport News, Virginia
• M. Minarni
  UNRI, Riau

Cosmology provides evidence that most of the mass of the observable universe cannot be associated with any of the known Standard-Model elementary particles. Evidence of this ‘dark matter' was also obtained in the recent data from space telescopes. Axions - hypothetical particles proposed to solve a strong CP problem in Quantum Chromodynamics - are dark matter candidates. Although they carry zero electric charge, they can be produced via Primakoff mechanism, resulting in predictable effects in the laboratory. We present first results from an ongoing LIPSS experiment to search for axion-like particles with Jefferson Lab's Free Electron Laser.

• R. Hajima, N. Nishimori
  JAEA/ERL, Ibaraki

In Japan, we have organized the ERL collaboration initiative towards future ERL light sources. Construction of an X-ray synchrotron light source, a multi-GeV ERL, is one of the targets of our collaboration. As an option of the multi-GeV ERL, we consider an X-ray FEL oscillator (XFEL-O) to produce hard X-ray pulses with excellent temporal coherence [1]. In this study, we present simulation results of the XFEL-O such as FEL lasing including spectral narrowing and nonlinear phase shift at Bragg reflectors, possible energy-doubling configuration to enhance the single-pass gain and so on.

[1] R. Hajima, N. Nishimori, "Free-Electron Laser Options for the Energy-Recvory Linac Light Source in Japan", MOPPH048, Proc. FEL'08.

• H. Ohgaki, M. A. Bakr, K. Higashimura, T. Kii, R. Kinjo, K. Masuda, T. Sonobe, S. Ueda, K. Yoshida
  Kyoto IAE, Kyoto
• Y.U. Jeong
  KAERI, Daejon
• H. Zen
  UVSOR, Okazaki

A mid-infrared free electron laser facility has been constructed for developing energy materials in Institute of Advanced Energy, Kyoto University. The accelerator has been installed and FEL gain saturation at 13.2 μm has been achieved in May 2008. The FEL power of about 3 MW has been observed at the accelerator room. We have constructed the FEL transport system from the accelerator room to the user room. The beam characterization at user room and preparation of the application of MIR-FEL will be introduced in the conference.

• H. Zen, M. Adachi, K. Hayashi, M. Katoh, J. Yamazaki
  UVSOR, Okazaki
• M. Hosaka, M. Koike, Y. Taira, Y. Uno, N. Yamamoto
  Nagoya University, Nagoya
• T. Tanikawa
  Sokendai - Okazaki, Okazaki, Aichi

At the UVSOR storage ring, free electron laser (FEL) have been studied for more than a decade. After the upgrade of accelerator components in 2003, FEL lasing around 199 nm [1] has been achieved. In these years, several application experiments of the FEL in deep UV region have been carried out. A feedback alignment system of the optical resonator has been developed to improve long term stability of the laser power for user experiments. To promote application experiments more extensively, now we have two upgrade plans. One is FEL lasing with top-up operation in order to maintain a high beam current and then a high out-coupled power. The other is upgrade of the optical klystron to have higher gain at deep UV region. These two upgrades will allow us to attract more users to our FEL.

[1] M. Hosaka, “Lasing below 200 nm at the UVSOR-II FEL,” UVSOR Activity Report 2007.

• B. Ketenoğlu, A. Aksoy, Ö. Karsli, M. Tural, O. Yavas
  Ankara University, Faculty of Engineering, Tandogan, Ankara
• H. Aksakal
  N.U, Nigde
• P. Arikan, E. Kasap
  Gazi University, Faculty of Arts and Sciences, Teknikokullar, Ankara
• B. Bilen
  Ankara University, Faculty of Sciences, Tandogan/Ankara
• H. Duran Yildiz
  Dumlupinar University, Faculty of Science and Arts, Kutahya
• S.O. Ozkorucuklu
  SDU, Isparta
• I. Tapan
  UU, Bursa

The TAC (Turkish Accelerator Center) IR FEL Oscillator facility, which has been supported by Turkish State Planning Organization (SPO) since 2006, will be based on a 15-40 MeV electron linac accompanying two different undulators with 2.5 cm and 9 cm periods in order to obtain IR FEL ranging between 2-250 microns. The electron linac will consist of two sequenced modules, each housing two 9-cell superconducting TESLA cavities for cw operation. It is planned that the TAC IR FEL facility will be completed in 2012 at Golbasi campus of Ankara University. This facility will give an opportunity to the scientists and industry to use FEL in research and development in Turkey and our region. In this study, the results of optimization studies and present plans about construction process of the facility are presented.

• D.J. Dunning, J.A. Clarke, S. Leonard, N. Thompson
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• I. Burrows, D.M.P. Holland
  STFC/DL, Daresbury, Warrington, Cheshire

The ALICE (Accelerators and Lasers in Combined Experiments) facility (formerly known as ERLP) is currently being commissioned at Daresbury Laboratory. It serves as a test facility for novel accelerator and photon science applications. As part of this facility, an oscillator-type FEL will be commissioned later in 2009. The FEL will be used to test energy recovery with a disrupted beam and to provide output for a select experimental programme. The FEL output will be measured and used to determine the accuracy of FEL modelling techniques. The facility could also potentially be used as a testbed for novel FEL concepts. In this paper, an overview of the FEL design is presented, together with an update of the status of commissioning preparations, including time-dependent modelling using the expected electron beam parameters.

• R.R. Lindberg, K.-J. Kim, Yu. Shvyd'ko
  ANL, Argonne
• W.M. Fawley
  LBNL, Berkeley, California

Simulations of the x-ray free-electron laser (FEL) oscillator are presented that include transverse effects and realistic Bragg mirror properties with the two-dimensional FEL code GINGER. In the present cases considered, the radiation divergence is much narrower than the mirror acceptance, and the numerical algorithm can be simplified by ignoring the finite angular bandwidth of the mirror. In this regime GINGER shows that the saturated x-ray pulses have 10⁹ photons and are nearly Fourier limited with peak powers in excess of 10 MW. We also include preliminary results for a four-mirror cavity that can be tuned in wavelength over a few percent, with future plans to incorporate the full transverse response of the Bragg mirrors into GINGER to more accurately model this tunable source.

• W.B. Colson, J. Blau, K.J. Cohn, J.C. Justin, R.J. Pifer
  NPS, Monterey, California

Thirty-three 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.

• V. Sahakyan, V.G. Khachatryan, A. Tarloyan, V.M. Tsakanov
  CANDLE, Yerevan

Time dependent simulations for the European XFEL SASE1 beamline for various FODO lattice quadrupole spacing in undulator section are presented. The dependence of radiation main parameters, saturation lengths, saturation power and brilliance on the betatron phase advance and the FODO lattice arrangement in undulator section are studied and compared with the case based on design focusing lattice. Impact of the trajectory correction and electron beam main parameters on the SASE FEL performance is discussed.

• C. Behrens, C. Gerth, I. Zagorodnov
  DESY, Hamburg

The free-electron laser (FEL) user facility FLASH at DESY operates a high-gain FEL and provides radiation in the vacuum-ultraviolet and soft X-ray regime. In order to improve the capability and performance of the facility, FLASH will be upgraded with a third-harmonic (3.9 GHz) RF system to linearise the longitudinal phase space in front of the bunch compressors. For the study of the phase space linearisation, a new diagnostic and matching section located directly in front of the undulators which are used for the generation of SASE (self-amplified spontaneous emission) was designed. This section makes it possible to determine sliced beam parameters with high longitudinal resolution. In this paper, we describe the design considerations for this diagnostic section and demonstrate the expected performance by means of particle tracking simulations.

• G. Geloni, P. Ilinski, E. Saldin, E. Schneidmiller, M.V. Yurkov
  DESY, Hamburg

Electron bunch imagers based on incoherent OTR constitute the main device presently available for the characterization of ultrashort electron bunches in the transverse direction. One difficulty to obtain high-resolution images is related with the very peculiar particle-spread function of OTR radiation, which has a large width compared to the usual point-spread function of a point-like source. In this contribution we explore the possibility of using coherent OTR instead of incoherent OTR radiation, by integrating an ORS setup with a high-resolution coherent optical transition radiation imager. Electron bunches are modulated at optical wavelengths in the ORS setup. When these electron bunches pass through a metal foil target, coherent radiation pulses of tens MW power are generated. It is thereafter possible to exploit the large number of available coherent photons. In particular we manipulate the particle spread function of the system, so that the imaging problem can be reduced to the usual (coherent or incoherent) imaging theory for point-like radiators.

• G. Geloni, P. Ilinski, E. Saldin, E. Schneidmiller, M.V. Yurkov
  DESY, Hamburg

We describe a novel technique to characterize ultrashort electron bunches in X-ray Free-Electron Lasers. Namely, we propose to use coherent Optical Transition Radiation to measure three-dimensional (3D) electron density distributions. Our method relies on the combination of two known diagnostics setups, an Optical Replica Synthesizer (ORS) and an Optical Transition Radiation (OTR) imager. Electron bunches are modulated at optical wavelengths in the ORS setup. When these electron bunches pass through a metal foil target, coherent radiation pulses of tens MW power are generated. It is thereafter possible to exploit advantages of coherent imaging techniques, such as diffractive imaging, Fourier holography and their combinations. The proposed method opens up the possibility of real-time, wavelength-limited, single-shot 3D imaging of an ultrashort electron bunch.

• E. Saldin, E. Schneidmiller, M.V. Yurkov
  DESY, Hamburg

We propose a new scheme for two-color operation of an FEL where an electron bunch generates an X-ray pulse and a long wavelength (VUV to infrared) radiation pulse. The scheme is very simple, cheap and robust, and therefore can be easily realized in facilities like FLASH, European XFEL, LCLS, and SCSS.

• E. Saldin, E. Schneidmiller, M.V. Yurkov
  DESY, Hamburg

FEL process leads to energy loss by electrons and increase of the energy spread. Further use of the electron beam for generation of the FEL radiation is possible, but only for longer wavelength. This technical solution is implemented in the design of the European XFEL. Two undulators, SASE1 and SASE3 are installed in a raw. SASE 1 is designed to operate at fixed photon wavelength of 0.1 nm. The SASE 3 undulator has been placed behind SASE1, and will produce radiation in the wavelength range of 0.4 - 1.6 nm. Degradation of the electron beam quality after SASE1 is not completely negligible, and its influence on SASE3 performance is the subject of the present study.

• S. Wesch, C. Behrens, B. Schmidt
  DESY, Hamburg
• P. Schmüser
  Uni HH, Hamburg

The observation of coherent optical transition radiation (COTR) has recently attracted a lot of attention because of its detrimental influence on OTR based diagnostic techniques, and also as evidence for a microbunching instability in magnetic bunch compressors. At FLASH, we have observed coherent visible and infrared radiation from bunches having passed the magnetic bunch compressor chicanes. The spectral distribution was measured from 400 nm to 1600 nm with high resolution for various settings of the magnet currents in the chicanes. Remarkably, the coherent visible radiation was found to be stronger for uncompressed bunches than for the compressed bunches needed for FEL operation. Additionally, images of the bunches using narrow band filters from 950 nm to 1650 nm have been recorded.

• E. Saldin, E. Schneidmiller, M.V. Yurkov
  DESY, Hamburg

This report deals with an update of parameters of a soft x-ray SASE FEL (SASE3) at the European XFEL. Two scenario of SASE3 operation are considered: nominal mode of operation (fixed energy of 17.5 GeV, and operating wavelength range 04 - 1.6 nm), and long wavelength mode of operation (fixed energy of 8.75 GeV, and operating wavelength range 1.6 - 6.4 nm). Perspectives for obtaining ultimate intensity of the radiation is discussed as well.

• L.-G. Wißmann, S. Schulz
  Uni HH, Hamburg
• V. R. Arsov
  PSI, Villigen
• M.K. Bock, M. Felber, P. Gessler, K.E. Hacker, F. Löhl, F. Ludwig, H. Schlarb, B. Schmidt, S. Wesch, A. Winter, J. Zemella
  DESY, Hamburg

FLASH (The Free-Electron Laser At Hamburg) is a High-Gain SASE-FEL providing ultrashort pulses with a central wavelength of 6 to 40 nm. Measuring and controling the longitudinal shape of the electron bunches can dramatically improve the stability of the lasing process. Non-destructive electro-optical bunch profile diagnostics have proved to work with resolutions down to 100 fs. The electro-optical (EO) setup at FLASH relies on a standard Ti:sapphire laser delivering 80 fs pulses with 4 nJ pulse energy. For practical and physical reasons (i.e., space, costs, maintenance, performance) a new, ytterbium fiber laser system has been developed. This laser system supports pulse energies of 4.5 nJ and a bandwidth of 100 nm at a center wavelength of 1030 nm. Active repetition rate control allows to lock the laser to the RF based synchronisation system. A better EO signal-to-noise ratio is expected due to the improved group velocity matching in the EO crystal. First results from the prototype Yb laser system and comparison with the Ti:Sa based data will be presented. Furthermore, a structurally engineered version, promising enhanced stability and reliability will be introduced.

• E. Allaria
  ELETTRA, Basovizza
• G. De Ninno
  University of Nova Gorica, Nova Gorica
• W.M. Fawley
  LBNL, Berkeley, California

The second stage of the FERMI FEL, named FEL-2, is based on the principle of high-gain harmonic generation and relies on a double-seeded cascade. Recent developments stimulated a revision of the original setup, which was designed to cover the spectral range between 40 and 10 nm. According to the numerical simulations we present here, the nominal (expected) electron-beam performance allows to extend the FEL spectral range down to 3 nm. A significant amount of power can be also expected at about 1 nm. We also show that the proposed setup is flexible enough for exploiting future developments of new seed sources, like, e.g., high harmonic generation in gases.

• G. De Ninno
  University of Nova Gorica, Nova Gorica
• E. Allaria, M. Cornacchia, G. De Ninno, S. Di Mitri, B. Diviacco, G. Penco, C. Spezzani, M. Trovò
  ELETTRA, Basovizza

The commissioning of the first stage of FERMI@Elettra will start during the summer 2009. During the first year of operation, efforts will concentrate on the optimization of the gun performance, as well as of the electron-beam acceleration and transport through the LINAC. By fall 2010, it is our aim to generate out of the LINAC an electron beam as similar as possible to the one needed for obtaining the nominal (i.e., user-required) FEL performance [see, e.g., S. Di Mitri et al., this Conference]. Such a beam will be then injected into the undulator chain and used to get the first FEL light. In this paper, we present our strategy for the commissioning of the FEL process, both in SASE and seeded configurations. On the basis of start-to-end simulations, we also discuss the expected FEL performance for day-one operation.

• M. Labat, F. Ciocci, G. Dattoli, M. Del Franco, A. Doria, G.P. Gallerano, L. Giannessi, E. Giovenale, A. Petralia, M. Quattromini, C. Ronsivalle, E. Sabia, I.P. Spassovsky, V. Surrenti
  ENEA C.R. Frascati, Frascati (Roma)
• D. Alesini, M. Bellaveglia, R. Boni, M. Boscolo, M. Castellano, E. Chiadroni, A. Clozza, L. Cultrera, G. Di Pirro, A. Drago, M. Ferrario, L. Ficcadenti, D. Filippetto, V. Fusco, A. Gallo, G. Gatti, A. Mostacci, E. Pace, L. Palumbo, B. Spataro, C. Vaccarezza
  INFN/LNF, Frascati (Roma)
• A. Bacci, V. Petrillo, A.R. Rossi, L. Serafini
  Istituto Nazionale di Fisica Nucleare, Milano
• F. Briquez, M.-E. Couprie
  SOLEIL, Gif-sur-Yvette
• B. Carré, D. Garzella
  CEA, Gif-sur-Yvette
• A. Cianchi, B. Marchetti
  INFN-Roma II, Roma
• G. Marcus, J.B. Rosenzweig
  UCLA, Los Angeles, California
• M. Mattioli, M. Serluca
  INFN-Roma, Roma

The SPARC FEL can be operated in both SASE and seeded modes. A major part of the second stage of the commissioning, currently in progress, is dedicated to the characterization of the SASE radiation. Simultaneously, we are finalizing the experimental setup for seeding. We present an in-situ characterization of the two input seeds that are foreseen: both are obtained via harmonic generation, the first one in crystal (400 and 266 nm) and the second in rare gas (Argon). We also describe the specific diagnostics implemented for the electron-seed overlap in the undulator, together with the diagnostics for radiation analysis (2D spectrometer and FROG). The seeding will enable the operation of the SPARC FEL in original cascaded configurations.

• S. Reiche
  PSI, Villigen

The currently planned X-ray facility at the Paul Scherrer Institut will span a wavelength range between 1 Ångstroem and 7 nm, distributed over 2 beamlines. The design aims for a compact layout with low electron beam energies and short undulator periods for the hard X-ray beamline. The resulting tolerances are the most stringent for the operation at the shortest wavelength of 1 Å. The tolerance study, presented here, distinguish the error sources between those of components within the undulator beam line (e.g. undulator field errors) and jitter in the electron beam parameters. The latter can be used as the figure of merits for defining the tolerance budget of the injector and linac.

• R. Bartolini, J.H. Han, I.P.S. Martin, J. Rowland
  Diamond, Oxfordshire

We discuss the possible operation of the UK New Light Source in the single spike regime with photon energies ranging from 50 eV to 1 keV. The optimisation process of the beam dynamics in the single spike regime is outlined and we present the results of full start-to-end simulations to show that few-fs to sub-fs pulses can be obtained, depending on the photon energy, with interesting power level. The analysis of the jitter of the SASE output characteristic is also reported.

• R.A. Bosch, J. Bisognano, M. Bissen, M.A. Green, H. Höchst, K. Jacobs, K.J. Kleman, R.A. Legg, R. Reininger, R. Wehlitz
  UW-Madison/SRC, Madison, Wisconsin
• W. Graves, F.X. Kärtner, D.E. Moncton
  MIT, Cambridge, Massachusetts

The University of Wisconsin-Madison/Synchrotron Radiation Center and MIT are developing a design for a seeded VUV/soft X-ray Free Electron Laser serving multiple simultaneous users. The present design uses an L-band CW superconducting 2.2 GeV electron linac to deliver 200 pC bunches to multiple FELs operating at repetition rates from kHz to MHz. The FEL output will be fully coherent both longitudinally and transversely, with tunable pulse energy, cover the 5-900 eV photon range, and have variable polarization. Bunch seeding at higher photon energies will be done with HHG laser pulses to avoid the need for fresh electron bunches. This unique facility is expected to enable new science through ultrahigh resolution in the time and frequency domains, as well as coherent imaging and nano-fabrication. We have proposed a program of R&D to address the most critical aspects of the project, including prototyping of a CW superconducting RF photoinjector, and development of conventional laser systems for MHz seeding of the FEL. We present an overview of the facility and our proposed R&D plan.

• H. Geng, Y.T. Ding, P. Emma, J.N. Galayda, Z. Huang, Y. Nosochkov
  SLAC, Menlo Park, California

LCLS capabilities can be significantly extended with a second undulator aiming at the soft x-ray spectrum (0.5- 5 nm). To allow for simultaneous hard and soft x-ray operations, 14 GeV beams at the end of the LCLS accelerator can be intermittently switched into the SLAC A-line (the beam transport line to End Station A) where the second undulator may be located. Recently, a new optics has been designed to transport the LCLS beam through the A-Line while preserving the beam brightness. In this paper, we discuss the A-Line Soft X-ray FEL design ─ parameter selections and performance expectations with an energy-chirped LCLS beam as required by the A-Line optics. Start-to-end simulations using realistic LCLS beams show that it is possible to generate ~100 GW FEL power with the pulse duration as short as 1-fs.

• M.K. Bock, V. R. Arsov, M. Felber, P. Gessler, K.E. Hacker, F. Löhl, F. Ludwig, H. Schlarb, B. Schmidt, A. Winter, L.-G. Wißmann
  DESY, Hamburg
• S. Schulz, J. Zemella
  Uni HH, Hamburg

At FLASH an optical synchronisation system with femtosecond stability is now being installed and commissioned. The pulses from an erbium-doped fibre laser being distributed in length-stabilised fibres to various endstations are used to detect the electron bunch arrival time using electro-optical modulators. To determine variations of the arrival time caused by phase changes of the RF gun or by timing changes of the photo-injector laser a beam arrival time monitor has been installed after the first acceleration section, prior to the bunch compressor BC2. A second bunch arrival time monitor installed after the bunch compressor allows for measuring the beam energy with high precision through a time-of-flight detection. Both monitors provide futher insight into the accelerator subsystem stability and opens up the opportunity for a robust fast feedback stabilisation.

• K.E. Hacker, V. R. Arsov, M.K. Bock, M. Felber, P. Gessler, F. Löhl, F. Ludwig, H. Schlarb, B. Schmidt, S. Schulz, A. Winter, L.-G. Wißmann, J. Zemella
  DESY, Hamburg

The master laser oscillator (MLO) at FLASH is locked to the master RF oscillator (MO) by mixing a 1.3 GHz signal from an MLO-based photodetector and a 1.3 GHz signal from the MO. The baseband output of the mixer is sent to an ADC-DSP-DAC regulation system that feeds back on a piezo controlled mirror position in the laser. The rms jitter and long term drift stability of the RF-lock circuit alone can be less than 5 fs in the temperature controlled chassis, but it can jump 10 to 15 fs when the temperature regulation of the room is disturbed by people working inside. Out-of-loop and in-loop measurements were also conducted under various environmental conditions.

• K.E. Hacker, V. R. Arsov, M.K. Bock, M. Felber, P. Gessler, F. Löhl, F. Ludwig, H. Schlarb, B. Schmidt, S. Schulz, A. Winter, L.-G. Wißmann, J. Zemella
  DESY, Hamburg

A unique, perpendicularly-mounted stripline BPM pickup is installed in the dispersive sections of the FLASH bunch compressors. For 4-5 um resolution, it requires a front-end that can measure the difference between the phases of the beam transient pulses with a resolution that is better than 10-15 fs. Two front-ends have been tested with the pickup: a 10.4 GHz down-mixing scheme and an electro-optical modulator (EOM) based scheme that uses the optical synchronization system. The EOM scheme typically produces 6 to 12 fs resolution. It is, however, expensive, complex, and dependent on an optical infrastructure that is still in a development phase. It was not anticipated that an RF-mixing scheme could deliver the required, sub-15 fs resolution and drift stability, but with a temperature stabilized chassis in a climatized room and sufficiently high frequencies, an RF mixing scheme can deliver resolution that is comparable to that of the EOM scheme for this particular application, the measurement of the relative arrival-times of two ~ps pulses. A direct comparison of beam arrival time measurements with 10.4 GHz down-mixing and EOM sampling is also presented.

• S. Schulz, L.-G. Wißmann
  Uni HH, Hamburg
• V. R. Arsov, M.K. Bock, M. Felber, P. Gessler, K.E. Hacker, F. Löhl, F. Ludwig, H. Schlarb, B. Schmidt, A. Winter, J. Zemella
  DESY, Hamburg

Free-electron lasers like FLASH and the planned European XFEL generate X-ray light pulses with durations in the order of a few ten femtoseconds. For these next-generation light sources, an optical synchronization system has been proposed to enable time-resolved measurements with sub-10 fs resolution and the laser-driven seeded operation mode of the FEL. The system is based on the timing-stabilized distribution of an optical pulse train, from which RF signals can be generated or to which other laser systems can be synchronized. Furthermore, it facilitates several special diagnostic measurements on the sub-10 fs time-scale.

The optical synchronization system at FLASH has recently progressed from a bread-board/test-bench implementation to a more permanent engineered infrastructure. We report on the master laser oscillator, the lock to the master RF oscillator, the free-space distribution unit, four installed fiber links, three bunch arrival-time monitors, one optical cross-correlator and the controls development. We also identified a couple of design issues during the commissioning of the devices.

• K. Nakao, K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nogami, T. Sakai, I. Sato, T. Tanaka
  LEBRA, Funabashi

The near-infrared free electron laser (FEL) has been provided for scientific studies in various fields since 2003 at the Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University. The behaviour of the LEBRA electron linac system has been monitored using various diagnostic devices such as beam position monitors, vacuum gauges, thermocouples, optical power monitors and so on. The results obtained during operation of the linac have been routinely stored in databases or files. This paper discusses about the analysis on the factors of fluctuation for the electron beam energy/position and the FEL optical power on the basis of the linac diagnostic results. Intentional change in the linac cooling water temperature, introduced periodically with 0.1°C peak-to-peak, has resulted in negligibly small fluctuation of the FEL output power. This suggests that the LEBRA linac cooling water system offering the temperature regulation within 0.02°C has sufficient performance for stable FEL lasing.

• H. Dewa, T. Asaka, H. Hanaki, T. Kobayashi, A. Mizuno, S. Suzuki, T. Taniuchi, H. Tomizawa, K. Yanagida
  JASRI/SPring-8, Hyogo-ken

The synchronous technologies of RF signal and laser pulse is important for photo-cathode RF gun system, because it determines the beam stability in phase and energy. For time jitter as small as 300 fs between RF signal and laser pulse, laser driven RF generation has been developed for our synchronization system since 2002. In the system, RF signal is directly generated from the laser pulse of 89.25 MHz by filtering the output of the photo detector with a band pass filter of 2856 MHz. The remaining problem was that the amplitude of the RF signal linearly depended on the laser pulse amplitude. For this reason, there was some amplitude jitter in the generated RF signal, which might also cause time jitter. To reduce the amplitude jitter, we developed a new laser driven RF generation system with amplitude stabilization realized by saturation amplifiers. The RMS deviation of the RF amplitude could be decreased to 0.173 % from 1.18 %. The RMS time jitter measured with a sampling oscilloscope was so small that it could not be correctly measured. The whole triggering and RF system of Spring-8 RF-gun is also presented.

• M. Znidarcic, A. Kosicek, M.O. Oblak
  I-Tech, Solkan

Libera Brilliance is already a standard device for beam position monitoring, while Libera Brilliance Single Pass, as its variant, optimizes for single pass position measurement. Complete signal processing on it has now been moved from embedded computer to FPGA. This enables complete hard real time data processing. Together with already implemented fast communication protocols (e.g. Gb Ethernet) it represents a reliable and deterministic building block for building of fast feedback or fast forward loops. The motivation, processing principles and first results are presented.

• N. Čutić, F. Lindau, S. Thorin, S. Werin
  MAX-lab, Lund
• C. Erny
  Lund Laser Centre, Lund University, Lund

To get information about arrival of the electron bunch relative to the laser pulse; electro-optic detection scheme in crossed polarizer configuration was set up and tested. Electron bunch induced birefringence in ZnTe crystal leaves a polarization footprint in a chirped infrared pulse. IR pulse is sampled before third harmonic generation from the amplifier, stretched and synchronized to the ultraviolet beam that is used for seeding. We report details of this setup and preliminary jitter measurements.

• G. Berden, A.F.G. van der Meer
  FOM Rijnhuizen, Nieuwegein
• W.A. Gillespie, P.J. Phillips
  University of Dundee, Nethergate, Dundee, Scotland
• S.P. Jamison
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• A. MacLeod
  UAD, Dundee

Longitudinal electro-optic electron bunch diagnostics has been successfully applied at several accelerators. The electro-optic effect can be seen as an upconversion of the Coulomb field of the relativistic electron bunch (THz radiation) to the visible spectral range, where a variety of standard diagnostic tools are available. Standard techniques to characterise femtosecond optical laser pulses (auto- and cross-correlators) have led to the schemes that can measure electron bunch profiles with femtosecond resolution [1]. These techniques require, however, well synchronized femtosecond laser pulses, in order to obtain the desired temporal resolution. Currently, we are exploring other EO variants which require less advanced laser systems. The first results will be presented in our contribution.

[1] Berden et al. Phys. Rev. Lett. 99, 164801 (2007), B. Steffen et al. Phys. Rev. ST - Acc. Beams, 12, 032802 (2009)

• P.J. Phillips, A. MacLeod
  UAD, Dundee
• W.A. Gillespie
  University of Dundee, Nethergate, Dundee, Scotland
• S.P. Jamison
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire

Electro-optic longitudinal bunch profile monitors are being implemented on ALICE (Accelerators and Lasers In Combined Experiements) at Daresbury Laboratories and have been used to characterise the electron bunch and to provide a testbed for electro-optic diagnostic techniques. ALICE is a 20 MeV energy recovery linac based light source with a bunch length of approximately 0.4 ps and a bunch charge of 80 pC. It is being developed as an experimental test bed for a broad suite of science and technology activities that make use of electron acceleration and ultra-short pulse laser techniques. At ALICE the electro-optic station is located immediately after the bunch compressor. This location allows nearby OTR beam profile monitors and Coherent Synchrontron Radiation (CSR) diagnostics to be used for calibration and benchmarking. This range of diagnostics will be evulated for suitabililty on the Next Light Source (NLS) under development in the UK. We present data for both spectral decoding and temporal decoding of the electron bunch at different bunch compression ratios, plus a measurement of the timing jitter of the electron bunch.