FEL 2006 - List of Keywords (radiation)

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radiation

Paper	Title	Other Keywords	Page
MOAAU01	FEL Prize Lecture: Coherent Electron-Beam Radiation Sources and FELs: A Theoretical Overview	electron, bunching, undulator, laser	1
	A. Gover, E. Dyunin University of Tel-Aviv, Faculty of Engineering, Tel-Aviv
	The theory of Coherent electron beam radiation devices in general, and FEL in particular, is reviewed in terms of a general simple formulation based on modal expansion of the radiation field. A variety of e-beam radiation mechanisms (FEL, TWT, Cerenkov Radiation) have common features. All these radiation mechanisms can emit coherent or partially coherent radiation by means of three basic kinds of radiation processes: Spontaneous emission (shot-noise radiation), Superradiance (bunched-beam coherent radiation) and Stimulated emission. The common radiation processes and their relations are explained, in both frequency and time domains, in terms of the radiation modes expansion formulation. It is shown that the coherence properties of the emitted radiation, in each radiation process, depend on the phase relations between the radiation wave-packets, emitted by the individual electrons and their entrance distribution statistics. In the high gain linear regime all these radiation mechanisms satisfy the Pierce dispersion equation, and all radiation characteristics are derived from the Pierce transfer functions. I employ the formulation to delineate limits of coherence of electron beam radiation sources, and particularly examine possible schemes for turning SASE FELs to operate as coherent radiation sources.
	Slides
	Talk

MOAAU04	First Lasing at SCSS	emittance, undulator, focusing, gun	16
	T. Shintake RIKEN Spring-8 Harima, Hyogo
	On 20 June, the SCSS prototype accelerator firstly generated pulses at VUV 49 nm FEL radiation, using ultra-low emittance beam provided by a newly developed single-crystal CeB6 thermionic cathode. SCSS prototype accelerator has been recently constructed in 2004-2005 at SPring-8 site in Japan, and comissioned recently. Its major purpose is to test hardware components developed at RIKEN/SPring-8 in SCSS R&D required to realize X-ray FEL at 1 Angstrom wavelength. One of the most challenging ideas in SCSS is to use CeB6 single crystal cathode to generate ultra-low emittance beam. We start from a lower beam current of 1 A from 500 kV e-gun, then we compress the bunch length more than a few 100 times to generate a few 100 A beam without deteliorating the emittance in the injector. Careful design was made on rf-cavities and magnetic lenses to perform velocity bunching in the injector system, which has been installed in the prototype accelerator. After four C-band accelerators, beam energy reaches 250 MeV. On 15 June, evening 4 pm, we firstly closed the upstream undulator, after one hour tuning, we observed narrow spectrum peaked at 49 nm in the intense VUV radiation, which was totally different from the natural undulator radiation (spontanenous mode). We performed careful measurements on various aspects, and announced "the first lasing" on 20 June.
	Slides
	Talk

MOBAU03	The European XFEL Project	linac, electron, undulator, photon	24
	R. Brinkmann DESY, Hamburg
	The European X-ray Free Electron Laser XFEL is a 4th generation synchrotron radiation facility based on the SASE FEL concept and the superconducting TESLA technology for the linear accelerator. This multi-user facility will provide photon beams in a wavelength regime from 0.1nm to 5nm in three FEL beam lines and hard X-rays in two spontaneous radiation beam lines, serving in total 10 experimental stations in the first stage. The project is in an advanced planning and technical preparation stage and its construction as a European/International facility near DESY in Hamburg will start in 2007. This talk gives an overview of the overall layout and parameters of the facility, with emphasis on the accelerator design, technology and physics.
	Slides
	Talk

MOBAU04	Optical Klystron Enhancement to SASE X-Ray FELs	klystron, undulator, electron, simulation	29
	Y. T. Ding, P. Emma, Z. Huang SLAC, Menlo Park, California V. Kumar RRCAT, Indore (M. P.)
	The optical klystron enhancement to self-amplified spontaneous emission (SASE) free electron lasers (FELs) is studied in theory and in simulations. In contrast to a seeded FEL, the optical klystron gain in a SASE FEL is not sensitive to any phase mismatch between the radiation and the microbunched electron beam. The FEL performance with the addition of four optical klystrons located at the undulator long breaks in the Linac Coherent Light Source (LCLS) shows significant improvement if the uncorrelated energy spread at the undulator entrance can be controlled to a very small level. In addition, FEL saturation at shorter x-ray wavelengths (around 1.0 angstrom) within the LCLS undulator length becomes possible. We also discuss the application of the optical klystron in a compact x-ray FEL design that employs relatively low electron beam energy together with a shorter-period undulator.
	Slides
	Talk

MOBAU05	Status of Japanese XFEL Project and SCSS Test Accelerator	emittance, electron, undulator, cathode	33
	T. Shintake RIKEN Spring-8 Harima, Hyogo
	Japanese XFEL based on SASE, aming at generating 1 A X-ray with 8 GeV e-beam, has been funded. Construction 2006-2010, beam comissioning is scheduled in 2010. In order to estabilish technology for XFEL, SCSS test accelerator, e-beam 250 MeV, 60 nm minimum wavelength, has been constructed, now under beam comissioning. We hope to be able to report the first lasing.
	Slides
	Talk

MOPPH001	Coherent Harmonic Generation on UVSOR-II Storage Ring	laser, electron, storage-ring, undulator	37
	M. Labat, G. Lambert CEA, Gif-sur-Yvette M.-E. Couprie SOLEIL, Gif-sur-Yvette T. Hara RIKEN Spring-8 Harima, Hyogo M. Hosaka, M. Katoh, A. Mochihashi, M. Shimada, J. Yamazaki UVSOR, Okazaki D. Nutarelli LAC, Orsay Y. Takashima Nagoya University, Nagoya
	In the Coherent Harmonic Generation Free Electron Laser configuration, an external seed signal, a commercial laser source, is focused inside the first undulator. The interaction between the electron beam and this seed leads to a more coherent light emission. Such devices are very promising for short wavelength operation with a rather compact facility. Experiments have been performed on the UVSOR-II Storage Ring (Okazaki, Japan) with electrons stored at 600 MeV, and using a 2.5 mJ Ti:Sa laser at 800 nm wavelength, 1 kHz repetition rate, and 100 fs up to 2 ps pulse duration, allowing emission at 266 nm. This third harmonic has been characterised versus various parameters. Optimizations have been realized on the electron beam and laser synchronisation, seed characteristics (focussing point, energy, and pulse duration). The dependency of the harmonic signal on the gain (undulator gap, magnetic functions) has also been studied. Theory is compared to experiment using both analytical models and simulation. These encouraging results make UVSOR-II storage ring an active test facility for Coherent Harmonic Generation scheme, as well as a potential VUV source for users experiments.

MOPPH005	Generation Regimes of FEL With Volume Distributed Feedback	electron, controls, electromagnetic-fields, feedback	41
	K. G. Batrakov, S. Sytova Belarussian State University, Scientific Research Institute of Nuclear Problems, Minsk
	As was shown earlier, threshold conditions for FEL with volume distributed feedback (VDFB) depends on geometry of Bragg diffraction. Present work considers nonlinear dynamics of quasi-Cherenkov (parametric) FEL, linear stage of generation of which was studied in previous works. Dependence of emission on electron beam density and diffraction geometry is produced using the computer code VOLC (volume laser code) created for simulation of volume FEL (VFEL). It is shown that operation regime of VFEL can be changed from amplification to regenerative amplification and to stationary and non-stationary generation by the changing of angle between transmitted and diffracted waves. Curves for dependence of threshold current and output power on diffraction geometry are built and discussed. V. G.Baryshevsky, K. G.Batrakov, I. Ya. Dubovskaya, Parametric (quasi-Cherenkov) X-ray FEL, Journal of Physics D, v.24, p. 1250 (1991).

MOPPH006	Extracting Information from Smith-Purcell FEL Simulations	simulation, multipole, bunching, electron	45
	J. T. Donohue CENBG, Gradignan J. Gardelle CESTA, Le Barp
	Simulations of Smith-Purcell radiation using 2D particle-in-cell codes have provided insight into the behavior of such devices, and have generally provided support to the viewpoint of the Vanderbilt University group. However, if one is interested in Terahertz frequencies, the need for small meshes and short time intervals makes the calculations exceedingly long. In particular, the S-P correlation between frequency and angle is only valid at distances large compared to the grating size, and may not be apparent if the simulation area is too small. With the help of the multipole expansion, we show how simulation data obtained with a small area may be extended to an area of arbitrary size. This enables us to confirm the presence of coherent higher order S-P peaks at the appropriate angles. H. L. Andrews, C. H. Boulware, C. A. Brau, and J. D. Jarvis, Phys. Rev. ST Accel. Beams 8, 050703 (2005)

MOPPH007	Simulation of Smith-Purcell FELs at Terahertz Frequencies	simulation, electron, bunching, resonance	49
	J. T. Donohue CENBG, Gradignan J. Gardelle CESTA, Le Barp
	Our previous work on the 2D simulation of a coherent Smith-Purcell FEL operating in the Terahertz domain is extended to a systematic study of the dependence on various parameters. The important question of the starting current reqired to produce coherent radiation is addressed, and our new results will be presented. As in our previous work we concentrate on two configurations, one similar to the Dartmouth S-P FEL, with a low energy continuous beam, and the other similar to the MIT experiment which uses a pre-bunched 15 MeV beam. A Bakhtyari, J. E. Walsh, and J. H. Brownell, Phys. Rev. Lett. E 65, 066503 (2002).** S. E. Korbly, A. S. Kesar, J. R. Sirigiri, and R. J. Temkin, Phys. Rev. Lett. 94, 054803 (2005)

MOPPH008	A Beam Shaper for the Optical Beamline of RF Photoinjectors	laser, cathode, electron, controls	53
	G. Klemz MBI, Berlin I. Will FZR, Dresden
	The transversal beam profile of a laser beam irradiating the photocathode has a significant influence on the emittance of the generated electron beam. Achieving the lowest emittance requires a flat-top beam profile. A typical laser, however, produces an intensity profile which is close to a Gaussian. That is why a special optical element, the so-called beam shaper, is required. We compare different technical solutions for the critical beam-shaping element. The demands on the design of the beamline resulting from the insertion of the beam shaper will be outlined. An aspherical lens pair of the Galilean type seems to be a favourable solution. It permits to precisely control the final intensity profile, it maintains both the temporal shape of the pulse and the coherence of the laser beam. Simulation of the propagation of the beam profile are presented. The described refractive beam-shaper significantly improves the energy efficiency of the complete beamline. It therefore allows to reduce the requirements regarding the energy of the laser pulses. Consequently, the application of an appropriately designed beam shaper can lead to a significant reduction of the overall costs of the laser.

MOPPH011	FELO: A One-Dimensional Time-Dependent FEL Oscillator Code	simulation, electron, emittance, undulator	59
	B. W.J. McNeil, G. R.M. Robb USTRAT/SUPA, Glasgow D. J. Dunning, N. Thompson CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire
	A one-dimensional, SDDS compliant time-dependent FEL oscillator code has been developed in Fortran 90. The code, FELO, solves universally-scaled FEL equations to simulate oscillator FELs operating from the low to high gain regime. The code can simulate start-up from shot noise, different electron pulse current distributions, the effects of cavity length detuning and temporal jitter between electron bunches. Cavity detuning curves for both the low-gain IR-FEL and the regenerative amplifier VUV-FEL of the 4th Generation Light Source (4GLS) proposal at Daresbury Laboratory are modelled. The code predictions for the VUV-FEL output are compared with simulations performed with the parallel implementation of Genesis 1.3 and are found to be in good agreement.

MOPPH020	Enhancement of a Coherent (Super Radiant) Emission in FEL by Means of Energy Modulation of an Emitting Short Electron Bunch	electron, simulation, electromagnetic-fields, wiggler	79
	Yu. Lurie, Y. Pinhasi CJS, Ariel A. Gover University of Tel-Aviv, Faculty of Engineering, Tel-Aviv
	The developing techniques for generation of short bunches of relativistic electron beams enable construction of high-power, compact super-radiant free-electron lasers (FELs). Optimal efficiency of the super-radiant emission is achieved with ultra-short pulses (the beam duration is much less then the period of radiation). Unfortunately, the minimum duration of the pulse that can be achieved in practice is technologically limited, restricting the frequency of the radiation. We demonstrate that a super-radiant emission can be strongly enhanced by means of a proper energy modulation of the driving beam pulse, as suggested by A. Doria et al.. In this way, a THz FEL source driven by short electron bunches generated by photo-cathode injection can be realized. Numerical simulations carried out using the WB3D code* show that linear energy modulation of a driving electron bunch enables one to increase the power of the super-radiant emission by a few orders of magnitude, approaching the power that can be achieved if ultra-short e-beam bunches are available. Possible limitations for the application of this method are also discussed, as well as the spectral purity of enhanced radiation. * A. Doria et al., Phys. Rev. Lett. 80, 2841 (1998).** Y. Pinhasi, Yu. Lurie and A. Yahalom, Nucl. Instr. and Meth. in Phys. Res. A 475, 147 (2001).

MOPPH028	Future Seeding Experiments at SPARC	undulator, laser, resonance, electron	95
	L. Giannessi, S. Ambrogio, F. Ciocci, G. Dattoli, A. Doria, G. P. Gallerano, E. Giovenale, M. Quattromini, A. Renieri, C. Ronsivalle, I. P. Spassovsky ENEA C. R. Frascati, Frascati (Roma) D. Alesini, M. E. Biagini, R. Boni, M. Castellano, A. Clozza, A. Drago, M. Ferrario, V. Fusco, A. Gallo, A. Ghigo, M. Migliorati, L. Palumbo, C. Sanelli, F. Sgamma, B. Spataro, S. Tomassini, C. Vaccarezza, C. Vicario INFN/LNF, Frascati (Roma) M. Bougeard, B. Carré, D. Garzella, M. Labat, G. Lambert, H. Merdji, P. Salieres, O. Tcherbakoff CEA, Gif-sur-Yvette M.-E. Couprie SOLEIL, Gif-sur-Yvette A. Dipace, E. Sabia ENEA Portici, Portici (Napoli) M. Mattioli Università di Roma I La Sapienza, Roma P. Musumeci, M. Petrarca INFN-Roma, Roma M. Nisoli, G. Sansone, S. Stagira, S. de Silvestri Politecnico/Milano, Milano P. L. Ottaviani, S. Pagnutti, M. Rosetti ENEA-Bologna, Bologna L. P. Poletto, G. T. Tondello Univ. degli Studi di Padova, Padova L. Serafini INFN-Milano, Milano
	Sources based on high order harmonics generated in gas with high power Ti:Sa lasers pulses represent promising candidates as seed for FEL amplifiers for several reasons, as spatial and temporal coherence, wavelength tunability and spectral range, which extends down to the 10^-9m wavelength scale. This communication is devoted to the description of a research work plan that is under implementation at the SPARC FEL facility in the framework of the EUROFEL programme. The main goal of the collaboration is to study and test the amplification and the FEL harmonic generation process of an input seed signal obtained as higher order harmonics generated both in crystal (400nm and 266 nm) and in gas (266nm, 160nm, 114nm) from a high intensity Ti:Sa laser pulse.

MOPPH030	X-Rays Generation with a FEL Based on an Optical Wiggler	laser, electron, emittance, bunching	99
	A. Bacci, C. Maroli, L. Serafini INFN-Milano, Milano M. Ferrario INFN/LNF, Frascati (Roma) V. Petrillo Universita' degli Studi di Milano, Milano
	The interaction between high-brilliance electron beams and counter-propagating laser pulses produces X rays via Thomson back-scattering. If the laser source is long and intense enough, the electron beam can bunch on the scale of the X-ray wavelength and a regime of collective effects can establish. In this case the FEL instability can develop and the system behaves like a FEL based on an optical undulator. Coherent X-rays can be irradiated, with a bandwidth thinner than that of the corresponding incoherent emission. The emittance of the electron beam and the non-uniformity of the laser energy limit the growth of the X-ray signal. We analyse with a 3-D code the transverse effects in the emission. The scalings typical of the optical wiggler make possible considerable emission also in violation of the Pellegrini criterion for static wigglers. A generalized form of this criterion is validated on the basis of the numerical evidence. An optimization of the radiation intensity has been done shifting the focus of the beam. The dependence of the radiation on the stability of the laser pulse has been studied. INFN, Section of MIlan, Via Celoria,16 20133 Milano (Italy)

MOPPH031	The Saturated Regime of a Seeded Single-Pass Free Electron Laser: a Theoretical Investigation through the Statistical Mechanics of the Vlasov Equation	electron, undulator, bunching, laser	103
	F. Curbis, F. Curbis Università degli Studi di Trieste, Trieste A. Antoniazzi, D. Fanelli Università di Firenze, Florence G. De Ninno ELETTRA, Basovizza, Trieste
	The quasi-stationary state characterizing the saturation of a single-pass free-electron laser is governed by the Vlasov equation obtained by performing the continuum limit of the Colson-Bonifacio model. By means of a statistical treatment, this approach allows to predict analytically the saturated laser intensity as well as the final electron-beam energy distribution. In this paper we consider the case of coherent harmonic generation obtained from a seeded free-electron laser and present predictions for the first stage of the project FERMI at Elettra project at Sincrotrone Trieste.

MOPPH032	Analysis of FEL Oscillations in a Perfectly Synchronized Optical Cavity	electron, undulator, laser, linac	107
	N. Nishimori JAEA/FEL, Ibaraki-ken
	We analyze free electron laser (FEL) oscillations in a perfectly synchronized optical cavity by solving the one dimensional FEL equations. The radiation stored in the cavity is shown to finally evolve into an intense few-cycle optical pulse in the high gain and low loss regime. The evolution of the leading slope of the optical pulse, which is defined from the front edge toward the primary peak, is found to play an important role in generating the intense few-cycle pulse. The phase space evolution of electrons on the second pass which interact with the leading slope of a SASE output pulse is obtained in a perturbation method similar to that used in our previous study for a SASE FEL. The resulting analytical solution of the leading slope in the 2nd pass is shown to be approximated by that of a SASE FEL with FEL parameter greater than rho. The same perturbation method can thus be used to the subsequent passes. The peak amplitude and the pulse length at saturation are found to scale with the electron beam density and optical cavity loss. Those scalings accounts for the intense few-cycle FEL pulses observed in a high power FEL. N. Nishimori, Phys. Rev. ST-AB 8, 100701 (2005).

MOPPH033	Two-Stream Smith-Purcell Free-Electron Laser Using a Dual-Grating: Linear Analysis	electron, laser, free-electron-laser, simulation	111
	D. Li, K. Imasaki ILT, Suita, Osaka Z. Liang, W. Liu, Z. Yang UESTC, Chengdu, Sichuan
	We present a linear analysis of two-stream Smith-Purcell Free-Electron Laser (SP-FEL). In this system, two electron-beams with velocity separation pass a rectangular dual-grating. The dispersion relation is derived employing the linear fluid theory and the growth rate is investigated through the numerical solutions. The instability of two-stream is obtained at an optimize separation velocity, and the effects of separation velocity , distance between the dual-grating, groove-depth, groove-width, beams energy on growth rate and bandwidth are studied in detail.

MOPPH034	Production of 'Giant' Pulses of Scattered Radiation from Pump Wave Spot Runing over the Electron Beam	electron, laser, scattering, simulation	115
	N. S. Ginzburg, V. R. Baryshev, A. Sergeev, I. V. Zotova IAP/RAS, Nizhny Novgorod
	To generate ultrashort electromagnetic pulses it is suggested to use the superradiance (SR) effects in the process of stimulatted scattering when the spot illuminated by pump wave shifts along the electron beam with group velocity of scattered radiation. According to theoretical consideration it is shown that in such conditions the amplitude of scattered SR pulse is proportional to interaction distance. This process is not sensitive to the dispersion of beam parameters due to extremely short time of wave interaction with every electron. In the case of scattering of laser radiation by a moderately relativistic electron beam it is possible to produce intense SR pulses either at terahertz (down conversion) or at UV (up conversion) frequency band depending on direction of pump wave propagation with respect to electron beam. In principle, to shift the illuminated spot along the electron beam, reflection of the pump wave by rotating mirror can be used. More realistic method is the transmission of the frequency-modulated pump wave through an optical prism.

MOPPH036	Influence of Linear Fluctuations on Low- and High-Gain Cherenkov FELs	electron, laser, free-electron-laser, bunching	118
	I. de la Fuente, K.-J. Boller, P. J.M. van der Slot Twente University, Laser Physics and Non-Linear Optics Group, Enschede
	In a previous study* it was shown that irregularities in the liner result in phase fluctuations of the ponderomotive potential which affects the gain of a low energy Cerenkov FEL. Here we investigate numerically how sensitive a Cerenkov FEL is to such fluctuations when operating in different gain regimes. For this study we considered an increased transverse dimensions of the liner and electron beam as compared to the study presented in, while the resonance frequency and beam voltage are held constant around 50 GHz and 80 kV respectively. The different gain regimes then correspond to different electron beam currents ranging from 0.8 A to 20 A. Without liner fluctuations, these beam currents result in a single pass saturated output power of approx. 200 W to 25 kW respectively, where the laser output saturates in a much shorter distance for the higher beam current. We have found that the low gain system (I=0.8 A) shows a much higher sensitivity to liner fluctuations than the high gain system (I=20 A). I de la Fuente, PJM van der Slot and K-J Boller. Proceedings of the 26th International Free-Electron Laser Conference and the 11th FEL User-Workshop. Trieste, Italy, p53-56 (2004)

MOPPH037	Theory of Radiation of Electrons in the Field of a Linear Polarized Stationary Electromagnetic Wave	electron, laser, polarization	122
	I. V. Drebot, Yu. N. Grigor'ev, A. Y. Zelinsky NSC/KIPT, Kharkov
	In the paper the results of exact integration of Lorentz equation for a free electron in the field of a linear polarized stationery electromagnetic wave are presented. Stationary wave is considered as a sum of two running in opposite directions linear polarized waves. Single integration of projections of equations on coordinate axes allows to reduce the task to solution of nonlinear equation of the second order for electron coordinate. The axis of projection coincides with a wave line. For approximate integration of the second order equation the expansion on two small parameters are used. Velocity and coordinate of electron in parametric form are presented in the paper. It is shown that under interaction of a relativistic electron with stationary wave there is a motion, which has a beat character. The amplitude and period of the beating were calculated.

MOPPH040	Transverse Coherence Properties of the LCLS X-Ray Beam	undulator, electron, simulation, laser	126
	S. Reiche UCLA, Los Angeles, California H.-D. Nuhn SLAC, Menlo Park, California
	Self-amplifying spontaneous radiation free-electron lasers, such as the LCLS or the European XFEL, rely on the incoherent, spontaneous radiation as the seed for the amplifying process. Though this method overcomes the need for an external seed source one drawback is the incoherence of the effective seed signal. The FEL process allows for a natural growth of the coherence because the radiation phase information is spread out within the bunch due to slippage and diffraction of the radiation field. However, at short wavelengths this spreading is not sufficient to achieve complete coherence. In this presentation we report on the results of numerical simulations of the LCLS X-ray FEL. From the obtained radiation field distribution the coherence properties are extracted to help to characterize the FEL as a light source.

MOPPH042	An Analysis of Shot Noise Propagation and Amplification in Harmonic Cascade FELs	electron, laser, bunching, undulator	130
	Z. Huang SLAC, Menlo Park, California
	The harmonic generation process in a harmonic cascade (HC) FEL is subject to noise degradation which is proportional to the square of the total harmonic order. In this paper, we study the shot noise evolution in the first-stage modulator and radiator of a HC FEL that produces the dominant noise contributions. We derive the effective input noise for a modulator operating in the low-gain regime, and analyze the radiator noise for a density-modulated beam. The significance of these noise sources in different harmonic cascade designs is also discussed. E. Saldin, E. Schneidmiller, M. Yurkov, Opt. Commun. 202, 169 (2002).

MOPPH046	Seeding the FEL of the SCSS Prototype Accelerator with Harmonics of a Ti:Sa Laser Produced in Gas.	laser, undulator, focusing, simulation	138
	G. Lambert, M. Bougeard, W. Boutu, B. Carré, D. Garzella, M. Labat CEA, Gif-sur-Yvette O. V. Chubar, M.-E. Couprie SOLEIL, Gif-sur-Yvette T. Hara, H. Kitamura, T. Shintake RIKEN Spring-8 Harima, Hyogo
	A particular seeded configuration will be tested in 2006 on the SCSS test facility (SPring-8 Compact Sase Source, Japan). This facility is based on a thermionic cathode electron gun (1 nC), a C-band LINAC (5712 MHz, 35 MV/m) and two in-vacuum undulators (15 mm of period). The maximum electron beam energy is 250 MeV and the SASE emission from visible to 60 nm can be obtained. The external source, obtained by the High order Harmonic Generation (HHG) process, can be tuned from the 3th (260 nm) to the 13th harmonic (60 nm) of a Ti: Sa laser generated in a gas cell. The experiment contains a first chamber, dedicated to harmonic generation and a second one for harmonic beam diagnostics and adaptation of the harmonic waist in the modulator. The tests have been performed in Saclay (15 mJ, 10 Hz, 50 fs). An energy of 2e-6J with a high stability for the 3th harmonic and a good transversal shape with an optimized energy level and a high stability for the 13th harmonic have been obtained at the modulator center place. The performances using PERSEO, GENESIS and SRW will be updated. The chambers will be installed on the SCSS test facility in the beginning of July for seeding tests during summer.

MOPPH048	The ARC-EN-CIEL FEL Proposal	laser, emittance, undulator, electron	146
	C. Bruni, O. V. Chubar, J.-M. Filhol, A. Loulergue, L. Nahon SOLEIL, Gif-sur-Yvette P. Bosland, B. Carré, M.-E. Couprie, G. Devanz, D. Garzella, O. Gobert, Ph. Hollander, M. Jablonka, M. Labat, G. Lambert, M. Luong, F. Meot, P. Monot, A. Mosnier, G. Petite, O. Tcherbakoff, B. Visentin CEA, Gif-sur-Yvette J.-R. Marquès LULI, Palaiseaux H. Monard, J.-M. Ortega CLIO/ELYSE/LCP, Orsay A. Rousse LOA, Palaiseau
	ARC-EN-CIEL (Accelerator-Radiation for Enhanced Coherent Intense Extended Light aims at providing the user community with coherent femtosecond light pulses covering from UV to soft X ray in France. Phase 1 aims at exploiting the different sources of seeding, in particular Harmonic generation in Gas (HHG), to improve the longitudinal coherence and shortening the output radiation wavelength in a rather compact device. Phase 2 uses a CW 10 KHz 1 GeV superconducting linear accelerator delivering high charge, subpicosecond, low emittance electron bunches for HHG seeded High Gain harmonic Generation extending to 1 nm. In phase 3, fs undulator sources in the IR, VUV and X ray and a FEL oscillator in the 10 nm range will be implemented on ERL beam loops for beam current or energy enhancement. Electron plasma acceleration and fs hard X ray produced by Thomson Scattering are also foreseen. Preliminary studies are carried out in the frame of the EUROFEL collaboration, concerning the electro-optical measurement at ELYSE, carbon nanotubes, synchronisation and beam shaping for the gun, seeding with high harmonics produced in gas on SPARC and compensation of microphonics for the Linac.

MOPPH050	The Properties of the FEL Output for Different Seeding Schemes	undulator, simulation, optics, electron	150
	J. Bahrdt BESSY GmbH, Berlin B. Faatz, R. Treusch DESY, Hamburg V. Miltchev Uni HH, Hamburg R. Reininger New Affiliation Request Pending, -TBS-
	Several seeding schemes, like self seeding for FLASH or seeded HGHG cascades for BESSY soft X-ray FEL, are proposed for existing or planned free electron laser facilities. The simulation of these schemes requires the detailed knowledge of the properties of the seeding radiation and the implementation of these properties in the Codes. Time dependent simulations with the 3D code GENESIS calculate the electric field distribution in and at the end of the undulator. The physical optics code PHASE permits the propagation of wave fronts across grazing incidence optics. Using the combination GENESIS PHASE GENESIS, the properties of the FEL output for different seeding schemes can be obtained. For example, the radiation quality of a SASE FEL can be improved in a self seeding scheme. Here, the radiation is monochromatized after a first undulator section and reflected back to the second Undulator modules. We present simulation studies for the self seeding option of FLASH.

MOPPH051	Development and Application of Figures of Merit to Evaluate the Output of HGHG FEL Cascades	background, linac, electron, simulation	154
	B. C. Kuske, R. Follath, A. Meseck BESSY GmbH, Berlin
	In the design of Free Electron Lasers, parameters like the peak power and the spectral power were established as figures of merit to evaluate the FEL output quality. However, spectra obtained with FEL studies using bunches from start-to-end simulations do not have a purely Gaussian profile, so that these simple parameters can no longer be used as figures of merit. Furthermore, criteria such as the signal-to-noise ratio and the stability of the source point, which is of extreme importance for the transport of the radiation to the user experiment, should be included in the design considerations. This paper suggests different criteria and parameters to describe and compare the FEL output, which are not readily provided by the common FEL codes. An IDL code has been written, that extracts this information from the regular GENESIS output. This procedure will be used to analyze the output of the BESSY FEL.

MOPPH052	Study of a Deflecting Dispersive Chicane for BESSY Soft X-Ray FEL	electron, dipole, coupling, simulation	158
	A. Meseck, G. Wuestefeld BESSY GmbH, Berlin
	High power, short pulse lengths and full coherence are the main parameters of the second generation free electron lasers like BESSY soft X-ray FEL. To provide radiation with these properties, cascades of HGHG stages are planned. In these stages an energy modulation is imprinted on the electron beam by seeding radiation. A dispersive section converts this energy modulation to a spatial modulation which is optimized for a particular harmonic. The following radiator is tuned to this harmonic and generates radiation with high power. The separation of the electron beam and seeding radiation after the modulation is desirable, as not only the quality of the radiator improves but also the seeding radiation itself can be used for diagnostics. A simple bending magnet leads to the separation but it causes a coupling of the longitudinal and transverse motion and could spoil the longitudinal modulation. Based on an exact linear model, a dispersive chicane is designed for one stage of the BESSY FEL which bends the electron beam without the coupling effects. The linear model will be presented and used to design a chicane. Simulations of the spatial modulation will also be discussed.

MOPPH053	Simulation Studies on the Self-Seeding Option at FLASH	undulator, electron, simulation, optics	162
	V. Miltchev, J. Rossbach Uni HH, Hamburg B. Faatz, R. Treusch DESY, Hamburg
	In order to improve the temporal coherence of the radiation generated by FLASH, a two-stage seeding scheme* is presently being realized. It consists of two undulator stages and a magnetic chicane and a monochromator located between them. In this contribution we investigate various configurations of the electron optics of the seeding set-up. The optimization of the lattice in the first seeding stage and the parameters of the magnetic chicane will be discussed. Simulation results for the performance of the seeded FEL at different resonant wavelengths will be presented. * J. Feldhaus et. al. "Possible application of X-ray optical elements for reducing the spectral bandwidth of an X-ray SASE FEL". Optics Communications, Volume 140, Pages 341-352

MOPPH054	FERMI @ Elettra: A Seeded FEL Facility for EUV and Soft X-Rays	electron, linac, undulator, laser	166
	J. N. Corlett, L. R. Doolittle, W. M. Fawley, S. M. Lidia, G. Penn, I. V. Pogorelov, J. Qiang, A. Ratti, J. W. Staples, R. B. Wilcox, A. Zholents LBNL, Berkeley, California E. Allaria, C. J. Bocchetta, D. Bulfone, F. C. Cargnello, D. Cocco, P. Craievich, G. D'Auria, M. B. Danailov, G. De Ninno, S. Di Mitri, B. Diviacco, M. Ferianis, A. Galimberti, A. Gambitta, M. Giannini, F. Iazzourene, E. Karantzoulis, M. Lonza, F. M. Mazzolini, G. Penco, L. Rumiz, S. Spampinati, G. Tromba, M. Trovo, A. Vascotto, M. Veronese, M. Zangrando ELETTRA, Basovizza, Trieste M. Cornacchia, P. Emma, Z. Huang, J. Wu SLAC, Menlo Park, California W. Graves, F. X. Kaertner, D. Wang MIT, Middleton, Massachusetts
	We describe the conceptual design and major performance parameters for the FERMI FEL project funded for construction at the Sincrotrone Trieste, Italy. This user facility complements the existing storage ring light source at Sincrotrone Trieste, and will be the first facility to be based on seeded harmonic cascade FELs. Seeded FELs provide high peak-power pulses, with controlled temporal duration of the coherent output allowing tailored x-ray output for time-domain explorations with short pulses of 100 fs or less, and high resolution with output bandwidths of the order of meV. The facility uses the existing 1.2 GeV S-band linac, driven by electron beam from a new high-brightness rf photocathode gun, and will provide tunable output over a range from ~100 nm to ~10 nm, and APPLE undulator radiators allow control of x-ray polarization. Initially, two FEL cascades are planned, a single-stage harmonic generation to operate over ~100 nm to ~40 nm, and a two-stage cascade operating from ~40 nm to ~10 nm or shorter wavelengh, each with spatially and temporally coherent output, and peak power in the GW range.

MOPPH063	Coherent X-Ray Production by Cascading Stages of High Gain Harmonic Generation Free Electron Lasers Seeded by IR Laser Driven High-Order Harmonic Generation	electron, laser, undulator, emittance	186
	J. Wu, P. R. Bolton SLAC, Menlo Park, California
	Coherent x-ray production achieved by seeded free electron lasing with cascaded high gain harmonic generation (HGHG) is important for next generation development of synchrotron light sources. We examine the feasibility and some features of FEL emission seeded by a high order harmonic of an intense infrared conventional laser source (HHG). In addition to the intrinsic FEL chirp phenomenon, the longitudinal profile and spectral bandwidth of the HHG seed are modified significantly by the FEL interaction well before saturation occurs. This smears out the original attosecond pulselet structure. As an example, we describe a cascaded HGHG scheme for coherent x-ray FEL generation that is seeded by the twenty-seventh harmonic of an ultrashort 800 nm laser pulse with 10 fs rms duration. Given the multiple order HHG spectrum, proof-of-principle experiments using lower order harmonics can also be considered.

MOPPH065	The First Experimental Observation of FEL Amplifier Efficiency Improvement using Electron Beam Energy Detuning at the NSLS SDL	electron, laser, resonance, simulation	190
	T. Watanabe, J. B. Murphy, J. Rose, Y. Shen, T. Tsang, X. J. Wang BNL, Upton, Long Island, New York H. Freund SAIC, McLean
	We report on the first observation of efficiency enhancement in a single-pass laser seeded FEL amplifier by detuning electron beam energy away from resonance. The dependence of the output FEL energy on the electron energy was measured; a maximum and average enhancement of 100 % and 70 % were observed. The spectral output of the seeded FEL both with and without an energy detuning was also measured. It was verified that the peak wavelength was dominated by the seed laser. The experimental results are compared with the analytical theory and the numerical simulation code, GENESIS 1.3.

MOPPH068	Attosecond Pulses from X-Ray FEL with an Energy-Chirped Electron Beam and a Tapered Undulator	undulator, electron, laser, simulation	202
	E. Saldin, E. Schneidmiller, M. V. Yurkov DESY, Hamburg
	We present a new scheme for generation of attosecond pulses in X-ray SASE FEL. A short slice in the electron beam is strongly modulated in energy by a few-cycle laser pulse in a short undulator, placed in front of the main undulator. Gain degradation within this slice is compensated by an appropriate undulator taper while the rest of the bunch suffers from this taper and does not lase. Three-dimensional simulations with the code FAST predict that short (200 attoseconds) high-power (up to 100 GW) pulses can be produced in Angstrom wavelength range with a high degree of contrast. A possibility to reduce pulse duration to sub-100 attosecond scale is discussed.

MOPPH069	Transverse and Longitudinal Coherence Properties of the Radiation from X-Ray SASE FELs	electron, undulator, simulation, emittance	206
	E. Saldin, E. Schneidmiller, M. V. Yurkov DESY, Hamburg
	We present the results of comprehensive numerical studies on transverse and longitudinal coherence of SASE FEL radiation. Development of coherence in exponential gain regime and saturation is studied with the help of similarity techniques. Expected coherence properties of X-ray sourses at the European XFEL, LCLS and SCSS are compared. The simulations were performed with the three-dimensional time-dependent code FAST using a real number of particles in the electron bunch.

MOPPH071	Design Status of PAL-XFEL	undulator, linac, electron, space-charge	210
	T.-Y. Lee, Y. S. Bae, J. Choi, J. Y. Huang, H.-S. Kang, C. Kim, D. E. Kim, M. Kim, I. S. Ko, J.-S. Oh, Y. W. Parc PAL, Pohang, Kyungbuk Y. Kim FEL/Duke University, Durham, North Carolina J. H. Park POSTECH, Pohang, Kyungbuk
	Pohang Accelerator Laboratory has a plan to build an X-ray FEL machine. This new machine will utilize the existing 2.5 GeV injection linac to the storage ring by upgrading its energy up to 3.7 GeV or more. The target wavelength will be 3-4.5 Angstrom and its third harmonic 1-1.5 Angstrom will also be used. The project will proceed in two stages: In the first stage, a VUV SASE machine with 385 MeV will be constructed and tested for the proof-of-principle. The full X-ray machine will be constructed in the next stage.

MOPPH073	An Enhanced GINGER Simulation Code with Harmonic Emission and HDF5 IO Capabilities	simulation, undulator, vacuum, diagnostics	218
	W. M. Fawley LBNL, Berkeley, California
	GINGER* is an axisymmetric, polychromatic (r-z-t) FEL simulation code originally developed in the mid-1980's to model the performance of single-pass amplifiers. Over the past 15 years GINGER's capabilities have been extended to include more complicated configurations such as undulators with drift spaces, dispersive sections, and vacuum chamber wakefield effects; multi-pass oscillators; and multi-stage harmonic cascades. Its coding base has been tuned to permit running effectively on platforms ranging from desktop PC's to massively parallel processors such as the IBM-SP. Recently, we have made significant changes to GINGER by replacing the original predictor-corrector field solver with a new direct implicit algorithm, adding harmonic emission capability, and switching to the HDF5 IO library** for output diagnostics. In this paper, we discuss some details regarding these changes and also present simulation results for a number of test cases ranging from LCLS SASE emission to performance of the FERMI@ELETTRA two-stage, harmonic cascade. * http://www-ssrl.slac.stanford.edu/lcls/technotes/LCLS-TN-04-3.pdf (also LBNL-49625-Rev. 1) ** http://hdf.ncsa.uiuc.edu/HDF5/

MOCAU01	The BESSY Soft X-Ray FEL: A Seeded HGHG FEL	electron, undulator, laser, bunching	226
	A. Meseck BESSY GmbH, Berlin
	Reproducibility, high power and short pulse length combined with variable polarization and tunable wavelength are the requirements to open new frontiers for the soft X-ray users. To provide radiation with such extraordinary properties, BESSY has been designing a seeded FEL based on high-gain harmonic-generation (HGHG) concept. The seeding with an external tunable laser ensures the reproducibility of the full-coherent radiation. The combination of so-called HGHG stages, used to down-convert the seed wavelength, and a final amplifier provides for the high power and superior spectral properties. Furthermore, the HGHG concept and the fresh bunch techniques planned for BESSY FEL mitigate the effects of parameter variation along the bunch which are expected from realistic assumptions of the Gun and LINAC structure. The design concept of the BESSY soft X-ray FEL will be presented and the stabilizing effect of HGHG stages and the benefits from the fresh bunch techniques and final amplifier will be discussed.
	Slides
	Talk

MOCAU03	The Use of HHG at 4GLS	undulator, electron, photon, simulation	234
	B. W.J. McNeil USTRAT/SUPA, Glasgow D. J. Dunning, N. Thompson CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire B. Sheehy Sheehy Scientific Consulting, Wading River, New York
	4GLS is a facility proposed for the Daresbury Laboratory in the UK* which will offer users a suite of high brightness synchronised sources from THz frequencies into the XUV. In the current design, photon energies from 8-100eV will be generated in a variable polarisation FEL amplifier directly seeded by a High Harmonic Gain system. The reasoning behind this choice will be discussed and characterisation of the sources based on the present design presented. *http://www.4gls.ac.uk/documents.htm#CDR
	Slides
	Talk

MOCAU04	Focal Point Laser-Field as Optical Seeder	laser, electron, cathode, coupling	242
	T. Shintake RIKEN Spring-8 Harima, Hyogo
	Focusing optical laser into its wavlength size, and crossing the electron beam through the focal point, interaction of electron with laser field becomes non zero, as a result, creates velocity modulation. In contrast with modulation scheme using undulator, this method does not require energy resonance condition to the electron beam, thus works all energy, even with energy chirp. Using it in front of the bunch compressor, with energy chirp, the wavelength can be compressed by large factor with bunch length compression.
	Slides
	Talk

MOCAU05	Analysis of the Process of Amplification in a Single Pass FEL of High Order Harmonics Generated in a Gas Jet	electron, laser, simulation, undulator	248
	L. Giannessi, M. Quattromini ENEA C. R. Frascati, Frascati (Roma) P. Musumeci INFN-Roma, Roma M. Nisoli, G. Sansone, S. Stagira, S. de Silvestri Politecnico/Milano, Milano
	We have studied the amplification of high harmonics generated by a short infrared pulse in a gas jet, injected in a free electron laser amplifier. The high-order harmonic spectra have been simulated using a 3D non-adiabatic model that includes both the single atom response and the effect of the propagation of the XUV field inside the gas jet. The response of a single atom to the IR field is calculated in the framework of the Strong Field Approximation (SFA); The nonlinear polarization associated to this process is evaluated as the acceleration of the nonlinear dipole moment. This term is used as source term in the propagation of the harmonic field inside the gas jet. The propagation effect are extremely relevant for the temporal structure of the XUV field as the coherent interference of the dipole emission of the different atoms leads to the selection of only one XUV pulse for each semi-cycle of the driving IR field. The amplification in the free electron laser has been simulated both in 1D and 3D with Perseo and GENESIS 1.3 respectively. The effects of filtering the seed spectrum have been analyzed and the coherence properties of the light are considered.
	Slides
	Talk

TUAAU01	Performance Achievements and Challenges for FELs Based on Energy Recovery Linacs	electron, linac, laser, recirculation	252
	G. A. Krafft Jefferson Lab, Newport News, Virginia
	During the past decade several groups have assembled free electron lasers based on energy recovered linacs (ERLs). Such arrangements have been built to obtain high average power electron and photon beams, by using high repetition rate beam pulses driving FEL oscillators. In this talk the performance of many existing and several proposed facilities from around the world are analyzed and reviewed. Going forward, many questions must be addressed to achieve still better performance including: higher average current injectors, better optimized accelerating cavities, higher energy acceptance and lower loss beam recirculation systems, and better optical cavity designs for dealing with the optical beam power circulating in the ERL FELs. The talk presents some of the current thinking on each of these issues.
	Slides
	Talk

TUAAU02	Future Light Sources: Integration of Lasers, FELs and Accelerators at 4GLS	electron, linac, undulator, laser	257
	J. A. Clarke CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire
	4GLS is a novel next generation proposal for a UK national light source to be sited at Daresbury Laboratory, based on a superconducting energy recovery linac (ERL) with both high average current photon sources (undulators and bending magnets) and three high peak current free electron lasers. Key features are a high gain, seeded FEL amplifier to generate XUV radiation and the prospect of advanced research arising from unique combinations of sources with femtosecond pulse structure. The conceptual design is now completed and a CDR recently published. The 4GLS concept will be summarised, highlighting how the significant design challenges have been addressed, and the project status and plans explained.
	Slides
	Talk

TUBAU01	Prospects of Cascaded Harmonic Generation FELs	laser, electron, bunching, undulator	281
	G. Penn LBNL, Berkeley, California
	Harmonic generation in Free Electron Lasers (FELs) encompasses many techniques for using an input seed laser to produce FEL radiation at a frequency that is multiples above that of the seed laser itself. This allows for the advantages of seeded FELs to be preserved, while extending the reach of these FELs to photon energies far above those produced by conventional laser sources. Many new projects are underway to make use of these methods, including the FERMI@Elettra* facility which envisions the use of two harmonic generation stages to reach photon energies above 100 eV. Different methods of harmonic generation are discussed, as well as the technical challenges to overcome in attempting to chain together multiple harmonic stages in an FEL. * C. Bocchetta et al., Proceedings of the 2005 FEL Conference, (2005) 682.
	Slides
	Talk

TUBAU04	Inverse Free Electron Lasers for Advanced Light Sources	undulator, laser, electron, simulation	292
	P. Musumeci, F. Germoni, M. Mattioli, M. Serluca INFN-Roma, Roma
	Laser accelerators hold the promise for high gradient acceleration and production of ultra short electron bunches. Among these, the inverse free-electron laser has recently demonstrated to be a mature and reliable scheme ready to step up from successful proof-of-principle experiments to cutting-edge applications. The very high gradient and the multi kAmp peak current of the output beam make it an attractive option in the hundreds of MeV to few GeV energy region. We examine the feasibility of using an IFEL driven by an high power Ti:Sa laser source to generate soft x-rays by FEL interaction in an undulator. A control of the slippage of the radiation over the ultrashort spikes of the IFEL-microbunched beam current is implemented to increase the gain and maintain the 200as-long pulse structure in the radiation profile.
	Slides
	Talk

TUPPH001	A 3D Model of the 4GLS VUV-FEL Conceptual Design Including Improved Modelling of the Optical Cavity	simulation, undulator, electron, optics	304
	N. Thompson, D. J. Dunning CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire K.-J. Boller, J. G. Karssenberg, P. J.M. van der Slot Twente University, Laser Physics and Non-Linear Optics Group, Enschede B. W.J. McNeil USTRAT/SUPA, Glasgow
	The Conceptual Design Report for the 4th Generation Light Source (4GLS) at Daresbury Laboratory in the UK was published in Spring 2006. The proposal includes a low-Q cavity (also called a regenerative amplifier) FEL to generate variably-polarised, temporally-coherent radiation in the photon energy range 3-10eV. A new simulation code has been developed that incorporates the 3D FEL code Genesis 1.3 and which simulates in 3D the optical components and radiation propagation within the non-amplifying sections of an optical cavity. This code is used to estimate the optimum low-Q cavity design and characterise the output from the 4GLS VUV-FEL. J. G. Karstenberg, P. J.M. van der Slot, J. W.J. Verschuur, I. V. Volohkin, K.-J. Boller (ibid)

TUPPH009	A Design Study of a FIR/THz-FEL for High Magnetic Field Research	linac, resonance, wiggler, electron	327
	M. Tecimer, L. C. Brunel, J. van Tol NHMFL, Tallahassee, Florida G. Neil Jefferson Lab, Newport News, Virginia
	Presently a conceptual design work for a NIR-FIR FEL system at the NHMFL/FSU is being undertaken. The system is intended to combine high magnetic field research with an intense, tuneable photon source, spanning the spectral region ~2–10⁰⁰ microns. Here, we present a design study involving the FIR/THz part of the NHMFL FEL design proposal. The suggested long-wavelength FEL encompasses in the first phase a thermionic injector (similar to that in use at the Forschungszentrum-Rossendorf ELBE facility) with a planned ~2 mA average current and a ~10 MeV superconducting rf linac module operating at 1.3 GHz. The broadband outcoupling over the envisaged FIR/THz spectral range (100–110⁰ microns) is accomplished by adopting a single (variable height slot) outcoupler in a waveguided cavity. Besides the performance predictions of the suggested long-wavelength FEL, techniques for the generation of high peak power, nanoseconds long THz pulses (for magnetic resonance applications) are also reported.

TUPPH012	Experimental Study of a Volume Free Electron Laser with a ''Grid'' Resonator	electron, laser, free-electron-laser, polarization	331
	V. G. Baryshevsky, N. A. Belous, A. Gurinovich, A. S. Lobko, P. V. Molchanov, V. I. Stolyarsky Belarussian State University, Scientific Research Institute of Nuclear Problems, Minsk
	Volume Free Electron Laser (VFEL) uses volume distributed feedback formed by diffraction gratings with different patterns,. First lasing of a Volume Free Electron Laser with a ''grid'' resonator, built from periodically strained metallic threads, was observed in*. Structures of this kind are often referred to as photonic crystals. Experiments with ''grid'' VFEL are carried out. Radiation is detected in the frequency range about 10 GHz. Backward wave regime is tested. Dependence of the generation threshold on the resonator length is investigated. It is demonstrated that use of volume resonators of the described type provides to weaken requirements for the electron beam shape and guiding precision. Radiation frequency tuning, which is an advantage of VFEL, can be achieved in such a structure by change of threads tilt to the electron beam velocity. V. G.Baryshevsky, K. G. Batrakov, A. A. Gurinovich et al., NIM 483A (2002) 21. V. G. Baryshevsky, NIM A 445 (2000) 281. * V. G. Baryshevsky et.al. LANL e-print archive: physics/0409125

TUPPH014	Laser Gain and Intra-Cavity Losses of the ELBE Mid-IR FEL	laser, electron, undulator, optics	339
	U. Lehnert, P. Michel, W. Seidel, J. Teichert, R. Wuensch FZR, Dresden
	The the U27-FEL of the ELBE radiation source allows to choose between five mirrors with different outcoupling holes. This allows to adapt the optical resonator to the required wavelength range to ensure the needed laser gain and to optimize the outcoupled laser power. Another parameter which influences the achievable laser gain and output power is the detuning length of the optical cavity. While for CW operation often the minimum detuning point is choosen which maximizes the outcoupled power, for pulsed-mode operation about one wavelength of cavity detuning maximizes the laser gain and yields best stability of the laser. To gain some insight into the behavior of the optical resonator we have measured the round-trip losses and the net laser gain and compare both to calulations. For the measurements we have used a fast-readout MCT detector to measure the decay and rise-time of the outcoupled infrared beam caused by a 10μs break in the electron beam micro-pulse train. We show gain and loss for 5, 10 and 20μm wavelength with the typical detuning curves of an FEL.

TUPPH015	Remote Controlled IR-Diagnostic Station for the FEL at Rossendorf	diagnostics, plasma, laser, electron	341
	W. Seidel, S. Friebel, R. Jainsch, M. Justus, K.-W. Leege, D. Proehl, D. Stehr, H. Weigelt, S. Winnerl, D. Wohlfarth FZR, Dresden
	The remote controlled diagnostic station delivers a small amount of the IR radiation by means of a system of relocatable mirrors and beam splitters to the spectrometer and to various power detectors working in different power ranges. Furthermore, a long wavelength MCT detector is integrated in the diagnostic station for gain and loss measurement in the whole wavelength range of the U27-FEL. The average radiation power available for the users can be reduced by a remote controlled attenuator. To characterize the optical micropulse duration we have built a non-collinear background-free autocorrelator as a part of the diagnostic station. By using a CdTe single-crystal for second-harmonic generation a broad wavelength coverage is obtained. Certain experiments require high pulse energies but moderate or low average power. For such experiments the repetition rate of the Rossendorf FEL can be reduced from 13 MHz to 1 kHz, in the future also to 1 Hz, by a semiconductor plasma switch excited with a synchronized Nd:YAG amplifier. This system is under commissioning and we will report on first results. Submitted as a poster to the FEL 2006 conference.

TUPPH018	New Resonator for the Israeli FEL	wiggler, electron, coupling, controls	349
	A. Faingersh, J. Dadoun, Kh. Garb, A. Gover, Y. Socol University of Tel-Aviv, Faculty of Engineering, Tel-Aviv G. G. Denisov, M. Y. Shmelyov IAP/RAS, Nizhny Novgorod M. Einat, B. Kapilevich, B. Litvak, Y. Pinhasi, A. Yahalom CJS, Ariel
	The Israeli FEL resonator was re-designed in order to reduce the overall round-trip losses and achieve control on the radiation output-coupling. In its new configuration, the resonator consists of overmoded corrugated rectangular waveguide and two radiation mode splitters, separating the high-energy e-beam from the laser radiation. The electron input splitter is based on Talbot effect in an overmoded rectangular waveguide. The radiation out-coupling is done in the output splitter. It is based on novel design and it combines Talbot effect between two parallel plates with free space propagation, and focusing by two curved cylindrical mirrors in a confocal imaging scheme. The waveguide and the splitters were tested experimentally, showing improved performance in comparison with the former resonator. The measured unloaded Q-factor of the new version is increased by a factor of ~ 3, attaining up to Q=30,000. Accordingly, the round-trip losses are ~15%. Rotating grids control the radiation out-coupling allowing wide variation for maximization of the radiation output power and extraction efficiency. The design layout and the testing results are presented.

TUPPH019	Present Status of the Israeli FEL: Increasing FEL Power by Electron Beam Energy Boosting	electron, controls, electromagnetic-fields, synchrotron	352
	Y. Socol, E. Dyunin, A. Gover, M. Volshonok University of Tel-Aviv, Faculty of Engineering, Tel-Aviv M. Einat, Yu. Lurie, Y. Pinhasi, A. Yahalom CJS, Ariel
	The status of R&D work aimed on increasing FEL power by boosting the electron beam energy after the radiation build-up is reported. A fine control of the electron beam energy during the radiation pulse is designed to compensate the small energy degradation during the pulse. Also, a controlled ramp (up or down) in the electron energy during the pulse will be applicable as well. Theoretical estimations of the output power in the presence of electron energy change during the pulse compared to the obtained experimental results are presented. 2 models, showing good agreement between them and with the existing data, are compared: low-gain analytical model based on the pendulum equation, and rigorous 3D FEL interaction model solved numerically. Another expected result of the design is to further extend the pulse duration with stable conditions and to obtain improved coherency. The electrical and mechanical lay-outs of the high-voltage boosting (leading to electron beam energy boosting) are also presented.

TUPPH021	Q-Switch Techniques Implemented at the ELETTRA Storage-Ring Free Electron Laser	electron, storage-ring, laser, synchrotron	360
	F. Curbis, F. Curbis Università degli Studi di Trieste, Trieste M. B. Danailov, G. De Ninno, B. Diviacco, L. Romanzin, M. Trovo ELETTRA, Basovizza, Trieste
	In a storage-ring FEL the gain can be calculated measuring the rise-time of giant pulses, produced by the interaction between the light stored in the optical cavity and an electron beam with low energy-spread (cold beam). This interplay produces the heating of the beam. Therefore, after the generation of a single giant pulse, the overlap between electrons and radiation is periodically prevented for a time necessary to dump the energy spread and recover the cold-beam condition. For this purpose two different methods are implemented at Elettra. In the first, modifying the radio-frequency of the ring, the change of the revolution time of electrons avoids the temporal overlap between the electron beam and the optical field in the mirror cavity. The second method relies on a mechanical gating (chopper) which intercept the light produced during previous interactions, inducing a periodic emptying of the optical cavity. The gain can be also estimated using an indirect formula after measuring the electron-beam energy spread and bunch length. In this paper we compare the different techniques mentioned above for the case of the Elettra SR-FEL.

TUPPH022	Development of a Compact Cherenkov Free-Electron Laser in Terahertz Spectral Range	electron, cathode, focusing, laser	364
	M. R. Asakawa, N. Miyabe Kansai University, Osaka M. Kusaba, K. Nakao, Y. Tsunawaki OSU, Daito, Osaka
	A Cherenkov free-electron laser (CFEL) generating terahertz radiation is now being developed under the joint research of Osaka Sangyo university and Kansai university. The main feature of this CFEL is its compactness. Electron beamlets emitted by a Spindt cathode are accelerated up to 60 keV in a D. C. electron gun and then are injected into 100μm-gaps between stacked plates of silicon, which acts as radiator. The radiation frequency will be ranged from 0.8 to 2 THz according to the acceleration voltage. In order to suppress diverging of the beamlet with a high current density about 1kA/cm², the electron gun and the radiator section are immersed in a longitudinal magnetic field produced by a super-conducting (SC) coil. The total length of the CFEL section, i.e., the distance between the cathode and beam dumper, is 4 cm and the diameter of this section is less than 2 cm. Such compact laser module is placed in the bore of SC coil. In spite of the large size of the cryostat and the power supply of the SC coil, the total footprint is about 1×1 m².

TUPPH023	High Power Deep UV Lasing on the UVSOR-II Storage Ring FEL	electron, laser, storage-ring, synchrotron	368
	M. Hosaka, M. Katoh, A. Mochihashi, M. Shimada UVSOR, Okazaki T. Hara RIKEN Spring-8 Harima, Hyogo Y. Takashima Nagoya University, Nagoya
	Thanks to an improved quality of the electron beam at the UVSOR-II storage ring, we have obtained a high power FEL lasing of 0.25 W in the deep UV region around 215 nm. The beam emittance of the UVSOR-II storage ring are improved by factor 6 in 2002. Recently we have renewed an rf accelerating cavity, which can be operated in about 3 time higher cavity voltage ( 150 kV) than the previous cavity voltage. All these improvement increased the FEL gain and we have obtained FEL lasing around 215 nm using Al2O3/SiO2 multilayer mirrors. In the primarily lasing experiment, the storage ring was operated at an electron energy of 600 MeV, which is ordinary energy for FEL experiments. Then we increased the energy to 750 MeV and obtained an extracted power of 0.25 W. The deep UV FEL has been already applied to an users irradiation experiment. Two other application experiments are planned now. In the presentation, the latest status of UVSOR-II FEL will be reported.

TUPPH024	Super Coherent THz Light Source Based on an Isochronous Ring with Very Short Electron Bunches	gun, lattice, simulation, electron	371
	H. Hama, K. Akiyama, F. Hinode, K. Kasamsook, M. Kawai, T. Muto, K. Nanbu, T. Tanaka, M. Yasuda Laboratory of Nuclear Science, Tohoku University, Sendai H. Tanaka JASRI/SPring-8, Hyogo-ken
	A project to develop a coherent Teraherz (THz) light has been progressed at Laboratory of Nuclear Science, Tohoku University. The coherent synchrotron light at the frequency region of THz is emitted from electron bunches of several tens femto-second bunch length created by a thermionic RF gun and a sophisticated bunch compressor. In addition, the beam is circulating a ring consisted of nearly complete isochronous optics for many turns, so that the average power of the radiation may be considerably enhanced. Forgetting about the amount of the charge, thermionic RF gun is quite suitable to produce such a very short bunch. We have developed an ITC (Independently-Tunabel-Cells) RF gun, which is consisted with two independent cavities in order to manipulate the longitudinal phase space. In addition to expected performance of the ITC RF gun and the bunch compressor, the paper describes the latest version of the lattice design of the isochronous ring and results of tracking simulations as well. Possibility of long wavelength SASE mode and superradiant on the isochronous ring are also discussed. H. Hama, Proc. the 27th Int. Free Electron Laser Conf., Stanford, CA (2005) 1-7. ** T. Tanaka, F. Hinode, M Kawai, A. Miyamoto, K. Shinto, H. Hama, Proc. PAC2005, Knoxville, TN (2005) 3499-3501.

TUPPH026	Dispersion Effects in Short Pulse Waveguide FEL	electron, simulation, undulator, free-electron-laser	378
	N. S. Ginzburg, A. Sergeev IAP/RAS, Nizhny Novgorod E. R. Kocharovskaya New Affiliation Request Pending, -TBS-
	The influence of waveguide dispersion on the FEL operation driven by short electron bunches is studied. Under the assumption of a high quality resonator a parabolic equation for the evolution of electromagnetic pulse profile is derived. Based on an analytical theory describing the linear stage of generation a starting condition is determined. A structure of supermodes representing the sum of resonator eigenmodes with locked phases is found as well. It is demonstrated that due to waveguide dispersion FEL is able to generate not only for positive but also for negative cavity detuning. The computer simulation of a nonlinear regime taking into account electromagnetic pulse dispersion defines a stationary profile of electromagnetic pulse in good agreement with experimental results,. It is shown that regimes with periodic and chaotic self-modulation of the pulse profile are realized for considerable exceeding of the length of interaction region over the threshold. A superradiant (transient) regime of short pulse generation is found for small cavity detuning. Jeong Y. U., et al. Proc. of the 2004 FEL Conference, Trieste, Italy, 2004, P.667. ** Doria A., Bartolini R., Feinstein J. IEEE J. Quantum Electron., 1993, V.29, P.1428.

TUPPH027	The Experimental Research of the SR-FEL Cavity Mirrors at 355nm and 248nm	laser, free-electron-laser, storage-ring, synchrotron	382
	H. L. Gao, R. Q. Tan, D. L. Wang, Y. Wang, J. Wu Institute of Electronics, Chinese Academy of Sciences, Beijing N. Y. Wang CIAE, Beijing
	The cavity mirrors of the storage-ring free-electron laser (SR-FEL) at 355nm and 248nm central wavelengths have been investigated experimentally with the optical coating materials of Al2O3/HfO2/SiO2 on fused silica. They were deposited by the electron-beans evaporation technology and ion-beam sputtering technology, so that the mirror have high damage threshold to laser pulse and resist to the reflectance degeneration- induced by the synchrotron radiation. The experimental results show that the absolute reflectance of the broad-band mirror at reaches up to R=99.45%, the frequency-tunable range with reflectance higher 99.00% is 406nm-331nm=75nm. For the dual-central wavelength mirror, the absolute reflectance are R(248nm)=98.21% and R(355nm)= 99.69%. The frequency-tunable range is 373nm-314nm for 355nm central wavelength; 275nm-272nm and 240nm-234nm for 248nm central wavelength, it isn't continual due to the absorption of HfO2 optical materials. All of the samples have passed the high-temperature test under the condition 400°C-4hrs successfully, and shown very stable optical property.

TUPPH032	Development of Powerful FEMs for X, Ka and W Bands for Physical and Industrial Applications	electron, controls, wiggler, linac	390
	M. Einat CJS, Ariel N. S. Ginzburg, N. Yu. Peskov, M. I. Petelin IAP/RAS, Nizhny Novgorod A. Gover, Y. Socol University of Tel-Aviv, Faculty of Engineering, Tel-Aviv A. Kaminsky, S. Sedykh JINR, Dubna, Moscow Region J. Lucas University of Liverpool, Liverpool
	FEMs are among the main sources of powerful microwave pulses from X to W-bands. Interest to such sources is caused by the large number of potential physical and industrial applications, requiring a wide variety of the radiation parameters. The new generation of the accelerators (SLAC, CERN) requires sources of ~100 MW pulse RF power at 30-38 GHz with a narrow spectrum. Material processing stations require kW-level average power. Alternatively, spectroscopic and biological experiments require lower power but for a specific frequency spectrum. The possibility to develop such sources is being studied at Tel-Aviv University, IAP RAS, JINR and The University of Liverpool within the framework of the INTAS collaboration project. Three successful FEM experiments have been carried out: Electrostatic-accelerator driven 70-130 GHz Tandem-FEM with kW-level pulse power (Tel-Aviv University.) Linac-driven 30-GHz FEM-oscillator with pulse RF power of ~ 20 MW (JINR + IAP RAS) Sub-relativistic e-beam industrial FEM tunable over X-band with output power up 1 kW (The University of Liverpool). The presentation summarizes the progress in the development of FEMs and their applications.

TUPPH034	Generation of Narrow Band Short mm Wave Superradiance Pulses in a Non-uniform Planar Waveguide	electron, simulation, undulator, cyclotron	397
	N. S. Ginzburg, R. M. Rozental, A. Sergeev, I. V. Zotova IAP/RAS, Nizhny Novgorod
	Recently significant progress was achieved in production of ultrashort pulses in millimeter wave band based on intense electron bunch supperradiance,,*. One of the problems for advance similar mechanisms in shorter wave bands is spectrum broadening caused by the simultaneous bunch interaction with several waveguide modes. To suppress spurious interaction we suggest to use the non-uniform planar waveguide. In such a waveguide the phase velocities of the different modes varied over longitudinal coordinate, with the exception of the fundamental TEM mode. As a result it is possible to suppress interaction of the short electron bunch with higher-orders modes responsible for lower frequencies radiation including cut-off modes. We studied 200-500 GHz superradiance of a 2 MV, 100 A, 100-300 ps electron bunch in a planar regular wiggler. It is shown that narrow band superradiance pulses could be produced in the 2 m long planar waveguide with the gap between plates linear increasing from 1-2 to 5-8 wavelength. The peak power of the pulses amounted 3 MW and hundreds of kW for the 200 GHz and 500 GHz bands correspondingly. Ginzburg N. S, et al. // Nucl. Instr. Meth. Phys. Res., 1999, A429 (1), 94 N. S.Ginzburg, et al. // Opt. Comm., 2000, 175 (1-3), 139 *A. G.Reutova, et al. // JETP Lett., 2005, 82(5), 263

TUPPH035	Generation of Superradiant Pulses by Backscattering of Pumping Wave on the Intense Electron Bunch	electron, simulation, scattering, background	400
	N. S. Ginzburg JINR, Dubna, Moscow Region V. I. Belousov, G. G. Denisov, A. Sergeev, I. V. Zotova IAP/RAS, Nizhny Novgorod A. G. Reutova, K. A. Sharypov, V. G. Shpak, S. A. Shunailov, M. R. Ulmaskulov, M. I. Yalandin RAS/IEP, Ekaterinburg
	Recently significant progress was archived in the generation of multimegawatt subnanosecond pulses in millimeter wave band utilizing the cyclotron and Cherenkov mechanisms of superradiance (SR). We study the novel mechanism of SR when the powerful pumping wave undergoes the stimulated backscattering on the intense electron bunch. Due to the Doppler up shift the radiation frequency can significantly exceed the frequency of the pumping wave. With the relativistic microwave generator as a pumping wave source such a mechanism can be used for generation of the powerful pulse radiation in the short millimeter and submillimeter wave bands. Experiments on the observation of the stimulated scattering in the superradiance regime were carried out at Institute of Electrophysics RAS with two synchronized accelerators. The 4 ns electron beam from the first accelerator is used for generation of the 38 GHz 100 MW pumping wave which subsequently scattered on the subnanosecond 250 keV 1 kA electron bunch produced by the second accelerator. The SR pulses with duration 200 ps and peak power about 1 MW were generated. The spectrum of scattered signal included the frequencies up to 150 GHz.

TUPPH037	FEL-Oscillator Simulations with Genesis 1.3	undulator, simulation, laser, optics	407
	J. G. Karssenberg, K.-J. Boller, J. W.J. Verschuur, P. J.M. van der Slot Twente University, Laser Physics and Non-Linear Optics Group, Enschede I. Volokhine Philips Research, Eindhoven
	We present a paraxial optical propagation code (OPC) as an extension to Genesis 1.3* for the theoretical description of FELs with an optical resonator. The OPC receives the optical output from a Genesis simulation, propagates it once through the resonator, and applies the result as the optical input pulse for a next run of Genesis. The OPC allows both the description of time dependent and steady state FEL operation. The propagation algorithms available are the Spectral algorithm, the Fresnel algorithm and a modified Fresnel algorithm. The latter enables a fast modelling of feedback via complex resonator designs that may include hard-edge elements (apertures) or hole-coupled mirrors with arbitrary shapes. The code enables to predict the output at each of the various optical elements which is of advantage for beam diagnostics and for designing suitable optics for a further propagation of the output beam. Finally, the OPC can be used to determine the far field output in connection with any Genesis 1.3 simulation, be it an oscillator or an amplifier FEL. As a test of the combined OPC and Genesis 1.3 codes we found good agreement with experimental data available for FELIX*. http://pbpl.physics.ucla.edu/~reiche/index.html** B. Faatz, Ph. D. Thesis, Nieuwegein, The Netherlands 1992.

TUPPH039	Bright Electron Beams and Smith-Purcell Free-Electron Lasers	electron, cathode, laser, space-charge	415
	C. H. Boulware, H. L. Andrews, C. A. Brau, J. D. Jarvis Vanderbilt University, Nashville, Tennessee
	We have continued to develop the theory of Smith-Purcell free-electron lasers * by including the effects of losses in the grating and reflections of the evanescent wave at the ends of the grating. We estimate the magnitude of the reflection coefficient to be about 15 % based on published simulations*, and compute the effect on the start current and the frequency shift. Experiments to observe these effects are underway. H. L. Andrews, C. H. Boulware, C. A. Brau, and J. D. Jarvis, Phys. Rev. ST-AB 8, 050703 (2005). ** D. Li, Z. Yang, K. Imasaki, and G.-S. Park, Phys. Rev. ST-AB 9, 040701 (2006).

TUPPH044	Free Electron Laser Study of Free Carbon Clusters	laser, photon, electron, background	423
	C. Spezzani, E. Allaria, F. Curbis, G. De Ninno, B. Diviacco, L. Romanzin, S. Tileva, M. Trovo ELETTRA, Basovizza, Trieste M. Amati, G. Bongiorno, C. Lenardi, T. Mazza, P. Milani, T. A. Mostefaoui, P. Piseri, L. Ravagnan Università degli Studi di Milano, Milano M. Coreno CNR - IMIP, Trieste
	UV absorption from carbon nanoparticles is a very interesting astrophysical topic. The prominent hump centered at 217.5nm is the most dominant feature in the interstellar extinction curve and also the most controversial and a long-standing problem in astrophysics. Actual models lack of experimental data about carbon dust in gas phase. At the University of Milano an experimental set-up based on a PulsedμPlasma Source has been developed for the investigation of free clusters at the Elettra Gas Phase beamline (CESyRA: Cluster Experiments with Synctrotron RAdiation). The cluster source produces very intense cluster beams with tunable size distribution. The design of the apparatus is extended with a chamber for gas phase reaction (water vapor, CO, H2…) providing a unique opportunity to study the gas phase properties of carbonaceous particles in different environment. We plan to investigate Resonant Raman scattering of free carbon particles tuning the high brilliance UV/VIS storage ring FEL of ELETTRA across the region of 217nm where the UV absorption hump in astrophysical data is observed and where a number of electronic transitions exist for variable size linear carbon chains.

TUPPH047	Absolute and Convective Instability of Smith-Purcell Free Electron Laser	simulation, electron, feedback, free-electron-laser	431
	D. Li, K. Imasaki ILT, Suita, Osaka G. S. Park SNU, Seoul Z. Yang UESTC, Chengdu, Sichuan
	Smith-Purcell free electron laser can operate on two different modes. The low-energy electron excites the absolute instability and it operates in the manner of a backward-wave oscillator, while the high-energy electron induces the convective instability and it operates like a traveling-wave tube. In this paper, we demonstrate those two instabilities using a two-dimensional particle-in-cell simulation. The simulation model supposes a rectangular grating to be driven by a continuous beam, and the radiation is in the THz regime. The beam bunching and the evolution of the radiation field are observed. The variation of the gain is reported as well.

TUPPH048	Superradiant Smith-Purcell Radiation in the Terahertz-wave Region from Bunched Electron Beams	simulation, bunching, electron, laser	435
	Z. Shi, Z. Liang, Z. Yang UESTC, Chengdu, Sichuan K. Imasaki, D. Li ILT, Suita, Osaka
	This paper presents a study of the characteristic of Smith-Purcell radiation (SPR) in the terahertz-wave (THz) region from bunched electron beams. The model consists of a grating with different period length and grating profile to be driven by a single electron bunch and a train of periodic bunches, respectively. The radiation efficiency and the angular distribution of SPR with various bunch distribution functions are investigated. According to the analysis, the coherent emission will occur when electron bunches are short compared with the radiation wavelength, and the coherent emission strongly depends on the longitudinal distribution of bunches. Some numerical results for the sinusoidal grating are compared with those for echellette grating .The results show that the THz radiation will be obtained using the reasonable parameters for the bunches and the grating. The results provide a basis for designing a superradiant SP free-electron laser in the THz wavelength region.

TUPPH049	Study on Superradiant Smith-Purcell Radiation	simulation, electron, bunching, single-bunch	439
	D. Li, K. Imasaki ILT, Suita, Osaka S. Amano, S. Miyamoto, T. Mochizuki NewSUBARU/SPring-8, Laboratory of Advanced Science and Technology for Industry (LASTI), Hyogo G. S. Park, Z. Yang SNU, Seoul
	A simulation of coherent and superradiant Smith-Purcell radiation is performed in GHz regime using a three-dimensional particle-in-cell code. The simulation model supposes a rectangular grating to be driven by a single electron bunch,a train of periodic bunches and a continuous beam, respectively. The true Smith-Purcell radiation is distinguished from the evanescent wave, which has an angle independent frequency lower than the minimum allowed Smith-Purcell frequency. We also find that the superradiant radiations excited by periodic bunches are emitted at higher harmonics of the bunching frequency and at the corresponding Smith-Purcell angles. The "start current" is determined as well as the distributions of the radiation intensity are presented.

TUPPH052	Future FEL Studies at the VISA Experiment in the SASE and Seeded Modes	undulator, electron, laser, simulation	443
	G. Andonian, M. P. Dunning, A. Y. Murokh, C. Pellegrini, S. Reiche, J. B. Rosenzweig UCLA, Los Angeles, California M. Babzien, I. Ben-Zvi, V. Yakimenko BNL, Upton, Long Island, New York
	The VISA (Visible to Infrared SASE Amplifier) experiment at BNL (Brookhaven National Laboratory) has previously demonstrated saturation at 840 nm in 2001. Further SASE studies, in 2003, have demonstrated an anomalously large bandwidth spread of the FEL spectrum due to off-angle emissions. This paper disseminates the current and future program of the VISA program at BNL. This includes a study of a seeded FEL, using a 1 micron YAG laser as a seed, and the accompanying diagnostics to characterize the radiation. Diagnostics include the double differential spectrometer, a mode converter to investigate the orbital angular momentum of light in the FEL, and an optical pepper-pot for coherence measurements. As usual, start-to-end simulations are presented.

TUPPH053	Magnetic Chicane Radiation Studies at the BNL ATF	electron, simulation, polarization, synchrotron	447
	M. P. Dunning, G. Andonian, A. M. Cook, E. Hemsing, A. Y. Murokh, S. Reiche, J. B. Rosenzweig, D. Schiller UCLA, Los Angeles, California M. Babzien, K. Kusche, V. Yakimenko BNL, Upton, Long Island, New York
	Coherent edge radiation, emitted from the edges of chicane dipole magnets, has recently been observed at the Accelerator Test Facility at Brookhaven National Laboratory. Using the 60 MeV linac, a series of experiments has been performed to characterize the radiation, including measurements of the spectrum, angular distribution, and polarization. Details and results of the experiments and plans for future experiments are presented.

TUPPH055	A Design for an XUV FEL Driven by the Laser-Plasma Accelerator at the LBNL LOASIS Facility	electron, undulator, laser, plasma	455
	W. M. Fawley, E. Esarey, W. Leemans, C. B. Schroeder LBNL, Berkeley, California
	We present a design for a compact FEL source of ultra-fast, high-peak flux, soft x-ray pulses employing a high-current, GeV-energy electron beam from the existing laser-plasma accelerator at LBNL's LOASIS facility. The proposed ultra-fast source would be intrinsically temporally synchronized to the drive laser pulse, enabling pump-probe studies in ultra-fast science with pulse lengths of ~10–25 fs. Owing both to the high current (>10 kA) and reasonable charge/pulse (~0.1-0.5 nC) of the laser-plasma-accelerated electron beams, saturated output fluxes are potentially on the order of 10¹⁴ photons/pulse. We examine devices based both on SASE and high-harmonic generated input seeds to give improved coherence and reduced undulator length, presenting both analytic scalings and numerical simulation results for expected FEL performance. A successful source would result in a new class of compact laser-driven FELs in which a conventional RF accelerator is replaced by a GeV-class laser-plasma accelerator whose active acceleration region is only several cm in length.

TUPPH057	First Tolerance Studies for the 4GLS FEL Sources	electron, simulation, undulator, photon	462
	D. J. Dunning, J. A. Clarke, D. J. Scott, N. Thompson CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire B. W.J. McNeil USTRAT/SUPA, Glasgow
	The Conceptual Design Report for the 4th Generation Light Source (4GLS) at Daresbury Laboratory in the UK was published in Spring 2006. 4GLS features three distinct FEL designs, each operating in a different wavelength range: an externally seeded amplifier operating in the photon energy range 8-100eV (XUV-FEL); a low-Q cavity (regenerative amplifier) FEL operating over 3-10eV (VUV-FEL); a high-Q cavity FEL operating from 2.5-200μm (IR-FEL). Preliminary results of tolerance studies for the FELs designs are presented. In particular, the effects of the relative timing offset between the seed pulse of the XUV-FEL and the electron bunch, as well as the effects of electron bunch timing jitter in the VUV-FEL, are presented.

TUPPH072	Generation and Characterization of the Microbunched Beams in the Range from 0.3 to 500 Femtoseconds	target, electron, laser, linac	481
	V. Yakimenko, M. Babzien, K. Kusche BNL, Upton, Long Island, New York E. K. Kallos, P. Muggli UCLA, Los Angeles, California W. D. Kimura STI, Washington
	The presentation will cover recent experimental results on generation and measurement of the beams with the bunch lengthes from 0.3 to 500 fs at Brookhaven Accelerator Test Facility. Double beam structure is produced at 100 fs - 0.5 ps time scale using compression in the magnetic chicane - "dog leg" arrangement. The beam structure is characterized using interferometer and 6 mm long plasma wakefield channel with the controllable plasma density. Arbitrary number of 10-100 femtosecond microbunches is sliced out of 5 ps long beam using wire mesh. CSR interferometer is used for detailed characterization of the beams. Accuracy of the bunch length measurement using CSR energy is greatly improved for the 0.3 fs bunches by spectral measurements of multiple harmonics.

TUCAU01	Design of a Long Wavelength FEL for Experiments under High Magnetic Fields	electron, laser, free-electron-laser, resonance	485
	W. J. van der Zande Nijmegen University, Physics Faculty, Nijmegen F. J.M. Harren, A. P.M. Kentgens, J. C. Maan, T. H.M. Rasing Radboud University Nijmegen, Institute of Molecules and Materials, Nijmegen
	At the University of Nijmegen, a novel collaboration has been established that combines a number of spectroscopic laboratories. These laboratories form a centre for advanced spectroscopy and constitute the spectroscopic department of the (Research) Institute for Molecules and Materials combining physical and chemical techniques. As part of the spectroscopic centre, a long-wavelength far-infrared free electron laser (FIR-FEL) operating between 100 um/3 THz and 1.5 mm/200 GHz will be designed and constucted in the coming years. The FIR-light should facilitate new experiments in the existing high field magnet laboratory (HFML), a large European Rerearch Infrastructure and in the NMR pavillion equipped with NMR instrumentation operating up to 800 MHz, especially for dynamic nuclear polarization technology.
	Slides
	Talk

TUCAU02	The Rossendorf IR-FEL ELBE	electron, laser, undulator, linac	488
	P. Michel, H. Buettig, F. G. Gabriel, M. Helm, U. Lehnert, Ch. Schneider, R. Schurig, W. Seidel, D. Stehr, J. Teichert, S. Winnerl, R. Wuensch FZR, Dresden
	The radiation source ELBE is the central research facility in the Forschungszentrum Rossendorf. The machine is based on a 40 MeV superconducting RF Linac wich can be operated up to 1 mA in cw mode. After commissioning the Bremsstrahlung and the X-ray facilities in 2002, and 2003 respectively, and the first lasing of the mid-IR FEL (4-22 um) in 2004 about 7000 hours user beam-time have been provided. At present a second FEL for long IR waves (15-150 um) using a partial waveguide is under commissioning. Besides in-house users especially the IR beam is available to external users in the FELBE (FEL@ELBE) program witch is a part of the integrated activity on synchrotron and free electron laser science in the EU. In this talk the fundamental features of the ELBE IR FEL's and the parameters demanded by users are displayed. In addition, an overview about user experimental work and important machine date like availability are shown. Future projects like the combination of the new High Magnetic Field lab with the ELBE-IR beams will be described.
	Slides
	Talk

TUCAU03	Status of the Novosibirsk High Power Terahertz FEL	electron, undulator, laser, linac	492
	N. Vinokurov, N. Gavrilov, B. A. Knyazev, E. I. Kolobanov, V. V. Kotenkov, V. V. Kubarev, G. Kulipanov, A. N. Matveenko, L. E. Medvedev, S. V. Miginsky, L. A. Mironenko, A. D. Oreshkov, A. V. Ovchar, V. Ovchar, V. M. Popik, T. V. Salikova, M. A. Scheglov, S. S. Serednyakov, O. A. Shevchenko, A. N. Skrinsky, V. G. Tcheskidov BINP SB RAS, Novosibirsk
	The first stage of Novosibirsk high power free electron laser (FEL) was commissioned in 2003. It is based on the normal conducting CW energy recovery linac (ERL). Now the FEL provides electromagnetic radiation in the wavelength range 120 - 230 micron. The maximum average power is 400 W. The minimum measured linewidth is 0.3%, which is close to the Fourier-transform limit. Four user stations are in operation now. Manufacturing of the second stage of the FEL (based on the four-turn ERL) is in progress.
	Slides
	Talk

THAAU02	Fourier Optics Treatment of Classical Relativistic Electrodynamics	undulator, electron, optics, laser	501
	G. Geloni, E. Saldin, E. Schneidmiller, M. V. Yurkov DESY, Hamburg
	In this paper we present a critical re-examination of Transition Undulator radiation, that has been first investigated a decade ago. We study a realistic undulator setup, which includes an undulator, two straight sections and two bends, before and after the undulator. This allows us to underline an important physical fact: it does not make sense to study the intensity distribution of transition radiation from an undulator without a detailed knowledge of the complete setup. The present paper also helps to point out several misconceptions present in literature regarding Coherent Transition Undulator Radiation.
	Slides
	Talk

THAAU03	A Scalloped Electron Beam Free-Electron Laser	wiggler, electron, emittance, simulation	509
	D. C. Nguyen LANL, Los Alamos, New Mexico W. B. Colson NPS, Monterey, California H. Freund SAIC, McLean
	Typical high-gain FEL amplifiers employ an electron beam that is matched to the wiggler so that the envelope remains constant throughout the wiggler. This paper describes a novel approach in which the electrons undergo natural betatron scalloping motion along the wiggler because the beams are deliberately mismatched at the wiggler entrance. We present an analysis of the electron scalloping motion and the FEL interaction with a scalloped electron beam. For a representative set of beam and wiggler parameters, we discuss the effect of the pinching the electron beams on the interaction in the FEL and on the focusing and propagation of the FEL radiation.
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	Talk

THAAU05	Space-Frequency Model of Ultra Wide-Band Interactions in Free-Electron Lasers	electron, free-electron-laser, laser, acceleration	513
	Y. Pinhasi, Yu. Lurie, A. Yahalom CJS, Ariel
	The principle of operation of intense radiation devices such as microwave tubes, free-electron lasers (FELs) and masers, is based on a distributed interaction between an electron beam and radiation. We developed a three-dimensional, space-frequency theory for the analysis and simulation of radiation excitation and propagation in electron devices and free-electron lasers operating in an ultra wide range of frequencies. The total electromagnetic field is presented in the frequency domain as an expansion in terms of cavity eigen-modes. The mutual interaction between the electron beam and the field is fully described by coupled equations, expressing the evolution of mode amplitudes and electron beam dynamics. The approach is applied in a numerical particle code WB3D, simulating wide band interactions in free-electron lasers operating in the linear and non-linear regimes. The code is used to study the statistical and spectral characteristics of multimode radiation generation in a free-electron laser, operating in various operational parameters. The theory is demonstrated also in the case of "grazing", resulting in a wide-band interaction between the electron beam and the radiation. Y. Pinhasi, Yu. Lurie, A. Yahalom: Space-frequency model of ultra wide-band interactions in millimeter wave masers, Phys. Rev. E 71, (2005), 036503- 1-8
	Slides
	Talk

THAAU06	Parametric Optimization of a X-Ray FEL Based on a Thomson Source	laser, electron, simulation, undulator	517
	L. Serafini, A. Bacci, C. Maroli, V. Petrillo, A. R. Rossi INFN-Milano, Milano M. Ferrario INFN/LNF, Frascati (Roma)
	We present a study based on a parametric optimization for a Thomson Source operated in FEL mode. This deals with the proposed scheme to use a high energy laser pulse colliding with a high brightness electron beam of low to medium energy electrons undulating in the incoming laser field may emit in a FEL coherent mode as far as some conditions are satisfied. A set of simple analytical formulas taking into account 3D effects is derived to express these conditions in terms of three free parameters, namely the wavelength of the laser, the amplitude of the ripples in the laser field, and the peak current of the eletron beam. A few examples of possible operating points are compared with results of 3D numerical simulations, showing the FEL coherent emission of X-rays in the 0.1 to 5 nm range with tens of MeV high brightness electron beams coliding with high energy laser pulses.
	Talk

THBAU01	APPLE Undulators for HGHG-FELs	undulator, electron, controls, vacuum	521
	J. Bahrdt BESSY GmbH, Berlin
	Cascaded HGHG-FEL facilities have been proposed by several groups. In these machines the beam characteristics of the initial seeding laser like short pulses and a small bandwidth are transformed to shorter wavelengths where lasers are not available. The first stages are equipped with planar devices. For full polarization control the last amplifier and the final radiator can be realized as APPLE devices. The specific demands on the polarizing devices as compared to planar hybrid devices are discussed for the example of the proposed BESSY HE-FEL to be operated at 1nm: the small good field region implies tight geometrical tolerances. Gap and phase dependent focussing effects have to be compensated. The field optimization procedure requires specific strategies. An improvement of the magnetic material is helpful in this context. Other important issues are the radiation protection system and the complexity of the control system.
	Slides
	Talk

THBAU03	How to Obtain High Quality Electron Bunches in the Presence of Normal Conducting LINAC Wake Fields	electron, emittance, linac, laser	537
	S. Di Mitri ELETTRA, Basovizza, Trieste
	The dynamics of electron beams involved in Free Electron Lasers (FELs) projects is an interplay between sources of 6-dimensional emittance dilution and methods of emittance preservation. Relatively long bunches are required for harmonic cascade seeded FELs in order to accommodate the timing jitter and the seed provided by the bunch itself at each stage of the cascade. A high quality is required from such electron beams (small transverse emittance and energy spread) together with a uniform distribution in time along the usable part of the bunch; non-linearity in the longitudinal phase space and in the transverse planes are also issues. A complex longitudinal phase space dynamics characterizes the study often in presence of by the Coherent Synchrotron Radiation (CSR) generated in magnetic compressors. This paper reviews specific problems related to the electron beam dynamics dominated by bunches of kA peak current and varying length (0.1 to 2 ps) in the presence of normal conducting linac wakefields. Methods implemented to minimize the 6-dimensonal phase space degradation are discussed. Results of high beam quality performance are illustrated with particles tracking codes.
	Slides
	Talk

THBAU05	Precision Measurement of the Undulator K Parameter using Spontaneous Radiation	undulator, photon, electron, alignment	548
	J. J. Welch, J. Arthur, P. Emma, J. B. Hastings, Z. Huang, H.-D. Nuhn, P. Stefan SLAC, Menlo Park, California R. M. Bionta LLNL, Livermore, California R. J. Dejus, B. X. Yang ANL, Argonne, Illinois
	Obtaining a precise and uniform value of the undulator parameter, K, over the full undulator length is critical for producing high-gain FEL radiation, especially in a hard x-ray source such as the LCLS. At an FEL wavelength of 1.5-Å the relative variation of K over the full undulator must be (dK/K)rms < 0.015%. Transverse misalignments, construction errors, radiation damage, and temperature variations all contribute to a different K value in each few-meter-long undulator segment. It is therefore important to measure relative K precisely, after installation and alignment, using beam-based techniques, if possible. We propose a fairly simple method using the angle-integrated spontaneous radiation spectrum of two interfering undulators, and the natural shot-to-shot energy centroid jitter of the electron beam, to measure the relative K error between two segments using both ideal and measured undulator fields. By 'leap-frogging' to different pairs of undulators with extended separations we hope to confirm or correct the value of K, including proper tapering, over the entire 130-m long FEL undulator.
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	Talk

THPPH006	Photocathode Laser for the Superconducting Photo Injector at the Forschungszentrum Rossendorf	laser, gun, emittance, focusing	564
	I. Will, G. Klemz MBI, Berlin F. Staufenbiel, J. Teichert FZR, Dresden
	We report on the design of the photocathode laser for a superconducting RF gun under development at the Forschungszentrum Rossendorf. The laser consists of a short-pulse oscillator, a pulse-picking Pockels cell, a linear amplifier chain and a frequency conversion stage. It generates pulses of about 5 ps duration with 13 MHz repetition rate and 1 W average power at 263 nm wavelength. Both the oscillator and the amplifiers are pumped by fiber-coupled semiconductor diodes. Nd:YLF is used as the gain medium of this laser. It introduces only small distortions on the optical wavefront of the laser beam and supports pulses of a few picoseconds duration. The beamline which transfers the laser beam to the photocathode of the RF gun has a large impact on the final beam profile. One can optimize the emittance of the electron beam by illuminating the cathode with a nearly flat-top beam profile. This is achieved by a pair of aspheric lenses and appropriate imaging optics in the beamline. Simulation of the beamline and its effect on the laser profile at the photocathode of the RF gun are also presented.

THPPH016	First Experience with the Machine Protections System of FLASH	undulator, linac, beam-losses, laser	587
	L. Fröhlich Uni HH, Hamburg M. Görler, P. Göttlicher, D. Noelle, D. Pugachov, H. Schlarb, S. Schreiber, M. Staack, M. Werner DESY, Hamburg A. Hamdi, M. Luong, J. Novo CEA, Gif-sur-Yvette
	Superconducting LINACs provide high brightness beams with substantial beam power. The design of the TTF2 machine is 70 kW beam power at the dump, XFEL will run 2 dump systems with 600 kW each. From this numbers is becomes very clear, that protections systems are required. This paper will present the design and implementation of the machine protection system of the FLASH facility, and will report on the first operational experience.

THPPH018	Single-Shot Longitudinal Diagnostics with THz Radiation at the Free-Electron Laser FLASH	electron, diagnostics, free-electron-laser, laser	594
	H. Delsim-Hashemi, J. Rossbach, P. Schmüser Uni HH, Hamburg O. Grimm, H. Schlarb, B. Schmidt DESY, Hamburg A. F.G. van der Meer FOM Rijnhuizen, Nieuwegein
	The longitudinal charge distribution in the electron bunches has a strong impact on the lasing process in a SASE-type FEL. The investigation of the longitudinal charge distribution in the electron bunches with very high resolution and on a bunch-by-bunch basis is enabled by a novel spectrometer which is based on diffraction gratings and multichannel signal detection. Measurements of coherent transition radiation with this spectrometer in both the scanning mode and the single-shot mode are presented. Structures in the electron bunches as short as 10 fs have been observed. Correlations between the measured FEL pulse energies and the signals in different wavelength channels of the single-shot spectrometer have been established. These data will be utilized to fine-tune the parameters of the bunch compression system at FLASH in order to optimize the gain in the SASE process.

THPPH029	The Diagnostics of the FERMI@Elettra Bunch Compressors	electron, diagnostics, dipole, feedback	629
	M. Veronese, S. Di Mitri, M. Ferianis ELETTRA, Basovizza, Trieste
	Bunch compressors are key components of the single pass Linac based seeded FEL FERMI@ELETTRA. Assuring their stable operation, to reliably produce sub-psec electron bunches, requires multiple non-destructive diagnostics. Most of these diagnostics provide the error signals to the feedback systems used to stabilize the energy and the peak current of the electron bunch which are crucial parameters for optimum FEL operation. The different operation regimes foreseen for FERMI* call for a flexible set-up, for both the bunch compressors and the associated diagnostics. In this paper we present the adopted diagnostics for the measurement of position, energy and energy spread; both "energy" BPM, in between BC, and OTR screen plus wire scanner will be used. The design of a relative bunch length monitor needed for the determination of the optimal compression and for peak current stabilization is presented as well. The scheme is based on non-invasive techniques, namely the detection of the coherent synchrotron radiation (CSR) from the last bending of the BC plus the coherent diffraction radiation (CDR) from a downstream slit. Finally, a technique for the bunch phase measurement is presented. * Study of the Electron Beam Dynamics in the FERMI @ ELETTRA Linac, M. Cornacchia, et al., Proc. of EPAC 2006 Conf., Scotland, UK (June 2006), to be published.

THPPH032	Free Electron Laser Triggered Photo-Cathode	cathode, emittance, laser, electron	641
	E. Sabia, A. Dipace ENEA Portici, Portici (Napoli) G. Dattoli ENEA C. R. Frascati, Frascati (Roma)
	The possibility of realizing a FEL triggered photocathode has been proposed long time ago and the advantages have been pointed out. In these devices the FEL can be exploited to extract electrons from a photocathode to provide a high quality e-beam. The device becomes even more appealing if photo-thermoionic cathodes can be exploited in two different phases. In the first the electrons are extracted from the cathode working as thermoionic and are used to drive a FEL oscillator, the FEL light is then used to flash the cathode which operates as a photo thermal assisted device. We comment on the possibility of using FEL triggered photocathodes to produce high quality e-beams for SASE or oscillator FEL devices. The use of the same e-beam driving the photocathode and the FEL makes the system naturally free of any synchronization problem arising when an external laser is used. Examples of interplay between the generation of electron and optical bursts are also investigated.

THPPH035	Design Study on High-Tc Superconducting Micro-Undulator	undulator, electron, dipole, superconductivity	653
	T. Kii, K. Masuda, M. Nakano, H. Ohgaki, N. Okawachi, T. Yamazaki, K. Yoshikawa, H. Zen Kyoto IAE, Kyoto
	A micro-undulator will be essential for compact and economical FEL systems. In this work, we introduce staggered array type micro-undulator using high Tc superconducting material. The high Tc superconducting material works as antiferromagnet pieces with pinning effect. Because a transverse magnetic field is potentially high, a micro-undulator with high K-value will be possible. Results of the field measurement with test pieces and estimated performance will be discussed in this conference.

THPPH037	Magnetic Field Measurement of the Undulator in KU-FEL	undulator, electron, laser, gun	660
	M. Nakano, T. Kii, K. Masuda, H. Ohgaki, N. Okawachi, T. Yamazaki, K. Yoshikawa, H. Zen Kyoto IAE, Kyoto
	We have constructed an infrared FEL facility for advanced energy researches. In the last FEL conference, numerical studies on the undulator in KU-FEL by optimizing both for electron beam and for the optical cavity have been presented. On the other hand, since the undulator had been used in FELI, demagnetization has been anticipated. So we have measured the magnetic field of the undulator. In this conference, we will show the FEL gain and the spectrum of spontaneous emission by using the measurement data. T. Fukui, et al., Proc. of the 2005 FEL conference (2005) 195-198. ** E. Nishimura, et al., Nucl. Instr. and Methods, A341 (1994) 39-42.

THPPH040	Study on Focusing Property of New Type Wiggler and SASE-FEL Experiment at the ISIR, Osaka University	wiggler, focusing, electron, permanent-magnet	672
	S. Kashiwagi, G. Isoyama, R. Kato ISIR, Osaka H. Sasaki, K. Tsuchiya, S. Yamamoto KEK, Ibaraki
	We have developed a new type of wiggler based on the edge-focusing wiggler for free electron laser (FEL) in the infrared region at the Institute of Scientific and Industrial Research (ISIR), Osaka University. The strong focusing (SF) scheme is adopted for the new wiggler in order to keep the beam size small along the wiggler. The period length of the wiggler is 60 mm, the number of periods is 32, and the total length is 1.938 m, including end magnet blocks for the orbit compensation. The wiggler consists of four FODO cells for double focusing. Focusing elements and defocusing elements are incorporate with single wiggler periods with edge angles of +5 and -5 degrees, respectively, and they are separated by three normal wiggler periods. The focusing properties of the SF wiggler for FEL and SASE are studied using a high-intensity electron beam at ISIR L-band linear accelerator. Optics parameters of electron beam are changed at the entrance of the SF wiggler, and the profiles of the electron beam are measured using screen monitors at several points along the wiggler. We will present the result of the beam experiments using the focusing wiggler in this conference.

THPPH041	Longitudinal Phase-Space Measurements of a High-Brightness Single-Bunch Beam	electron, photon, linac, single-bunch	676
	R. Kato, T. Igo, G. Isoyama, S. Kashiwagi, Y. Kon ISIR, Osaka
	The performance of a SASE-FEL strongly depends on the beam parameters, such as a longitudinal beam profile, a bunch charge, transverse emittances and an energy profile. The correlation between the longitudinal electron positions in a bunch and their energies has a critical effect on the temporal evolution of the optical pulse of SASE, and various methods to evaluate the longitudinal phase-space profile are under intense study. A new technique to measure the longitudinal phase-space distribution of the bunched electrons in one-shot using the combination of an energy profile monitor and a streak camera are currently under development at ISIR, Osaka University. In this contribution, preliminary experimental results of the measurements are presented.

THPPH050	Beat-Wave Laser-Driven Photoinjector for Superradiance Free-Electron Laser	electron, laser, beat-wave, gun	699
	Y.-C. Huang, H.-L. Chang, A.-C. Chiang NTHU, Hsinchu
	Electron bunching plays a crucial role in a radiative emission process. Every free-electron laser (FEL) more or less relies on periodic bunching of electrons to build up radiation power. In this paper, we present our study on the generation and acceleration of periodically bunched electrons in a photo-injector. The idea is to use a laser beat wave to induce a density modulated photocurrent from a photocathode, which is subsequently accelerated to a relativistic speed. The electron micro-bunches in the density modulated current repeat at the laser beat frequency. Our computer simulations using the ASTRA* code show remarkable modulation contrast in > 50 A output current of a 4 MeV RF photocathode gun and a 20 MeV photocathode accelerator. With slight modifications to a conventional photocathode-gun driver laser, a UV beat-wave laser with a variable beat frequency can be implemented by combining two chirped laser pulses with a variable time delay. We will report our experimental progress toward realizing such a new technique in a compact superradiance Smith-Purcell FEL at THz frequencies. * K. Floettmann, ASTRA User Manual, http://www.desy.de/mpyflo/Astra\_dokumentation

THPPH055	Nonintercepting Beam Size and Position Monitor Using ODR for X-Ray FELs	quadrupole, diagnostics, polarization, dipole	710
	A. H. Lumpkin, W. Berg, N. Sereno, B. X. Yang, C. Yao ANL, Argonne, Illinois D. W. Rule NSWC, West Bethesda, Maryland
	Interest in nonintercepting (NI) beam size and position diagnostics in the undulators of x-ray free-electron lasers (XFELs) is driven by the requirement of beam-emittance matching, as well as by the need to minimize radiation damage to the undulator's permanent magnets from scattered beam produced by the insertion of converter screens. For these reasons, our investigations on optical diffraction radiation (ODR) as NI relative beam size and position diagnostics are particularly relevant to XFELs. We report the extensions of our studies at 7-GeV beam energy to aspects of the vertical and horizontal polarization components of the ODR near-field and far-field images. The near-field, vertically polarized data are particularly interesting since the vertical field lines at the metal more directly reflected the actual beam sizes. Although our experiments to date are with larger beams and impact parameters of 1-2 mm, our analytical model indicates that this technique scales with beam size and has sensitivity at the 20- to 50-micron regime with an impact parameter, d = 5 times σ-y =100 microns. This is the x-ray FEL intraundulator beam size regime.

THPPH056	Initial Search for 9-keV XTR from a 28-GeV Beam at SPPS*	wiggler, photon, background, diagnostics	714
	A. H. Lumpkin ANL, Argonne, Illinois J. B. Hastings SLAC, Menlo Park, California D. W. Rule NSWC, West Bethesda, Maryland
	The potential to use x-ray transition radiation (XTR) as a beam diagnostic and coherent XTR (CXTR) as a gain diagnostic in an x-ray FEL was proposed previously. At that time we noted that the unique configuration of the SLAC Sub-picosecond Photon Source (SPPS) with its known x-ray wiggler source, a special three-element x-ray monochromator, x-ray transport line, and experimental end station with x-ray detectors made it an ideal location for an XTR feasibility experiment. A test of XTR intensity with respect to the x-rays emitted by the SPPS wiggler was proposed. The three-element monochromator was first adjusted to transport 9-keV or 1.3-Angstrom x rays from the SPPS wiggler source to the camera. The expected source strength in the bandpass of the monochromator was about 2x10⁷ photons per 3 nC electron pulse, and our calculated XTR intensity was about 10³ photons. We first successfully imaged the SPPS x-ray beam with the ANDOR x-ray CCD by using an Al-foil attenuation of 4x10³. The wiggler gap was then opened, and x-ray images recorded with the Ti foils out for background evaluation and with the Ti foils inserted to search for XTR. Initial images will be presented.

THPPH059	Energy Modulation of the Electrons by the Laser Field in the Wiggler Magnet: Analysis and Experiment	electron, wiggler, laser, resonance	725
	K. Holldack BESSY GmbH, Berlin A. Zholents LBNL, Berkeley, California
	Energy modulation of the electron beam after the interaction with the laser field in the wiggler magnet can be calculated using interference of the laser field and the field of spontaneous emission in the far field region of wiggler radiation. Quite often this approach gives a deeper insight on the process than traditional calculations where the effect of the laser field on the electron energy is integrated along the electron trajectory in the wiggler. We demonstrate it by showing the agreement between the analytical model and the experiment involving wiggler scan measurements with large detuning from the FEL resonance producing more than one order of magnitude variations in the amplitude of the energy modulation. The high sensitivity was achieved using the THz radiation from a sub-mm density variations that energy modulated electron leave behind while propagating the storage ring lattice. All measurements were performed at the BESSY-II electron storage ring.

THPPH062	Calculation of the Beam Field in the LCLS Bunch Length Monitor	electron, electromagnetic-fields, synchrotron, synchrotron-radiation	728
	G. V. Stupakov, Y. T. Ding, Z. Huang SLAC, Menlo Park, California
	Maintaining a stable bunch length and peak current is a critical step for the reliable operation of a SASE based x-ray source. In the LCLS, a bunch length monitor (BLM) right after the bunch compressors is proposed based on the coherent radiation generated by the short electron bunch. Due to its diagnostic setup, the standard far field synchrotron radiation formula and well-developed numerical codes do not apply for the analysis of the BLM performance. In this paper, we develope a calculation procedure to take into account the near field effect, the effect of a short bending magnet, and the diffraction effect of the radiation transport optics. We find the frequency response of the BLM after the first LCLS bunch compressor and discuss its expected performance. J. Wu, P. Emma, Z. Huang, Proceedings of 2005 Particle Accelerator Conference 428.

THPPH064	Bunch Length Measurements at JLab FEL	electron, synchrotron, synchrotron-radiation, laser	736
	P. Evtushenko, J. L. Coleman, K. Jordan, J. M. Klopf, G. Neil, G. P. Williams Jefferson Lab, Newport News, Virginia
	The JLab FEL is routinely operated with sub-picosecond bunches. The short bunch length is important for high gain of the FEL. Coherent transition radiation has been used for the bunch length measurements for many years. This diagnostic can be used only in the pulsed beam mode. It is our goal to run FEL with CW beam and 74.85 MHz micropulse repetition rate. Hence it is very desirable to have the possibility of doing the bunch length measurements when running CW beam with any micropulse frequency. We use a Fourier transform infrared interferometer, which is essentially a Michelson interferometer, to measure the spectrum of the coherent synchrotron radiation generated in the last dipole of the magnetic bunch compressor upstream of the FEL wiggler. This noninvasive diagnostic provides the bunch length measurements for CW beam operation at any micropulse frequency. We also compare the measurements made with the help of the FTIR interferometer with the data obtained by the Martin-Puplett interferometer. Results of the two diagnostics are usually agree within 15%. Here we present a description of the experimental setup, data evaluation procedure and results of the beam measurements.

THCAU01	Overview on Diagnostics for X- and XUV-FELs	diagnostics, laser, electron, emittance	761
	B. Schmidt DESY, Hamburg
	Controlling and optimizing the SASE process of X-FELs and XUV-FELs requires detailed knowledge and information about the parameters of the driving electron beam which are of critical influence on the laser performance. Due to the very high peak current, collective phenomena have to be carefully measured and controlled while integral (projected) parameters are of limited use. This necessitates the development of a variety of diagnostics tools to monitor the electron bunch parameters in detailedness beyond the capabilities of conventional systems. Longitudinal bunch structures can be derived from time domain methods like electro optic techniques or using transverse deflecting RF-structures, and from frequency domain methods using coherent radiation. The talk will report on recent developments with special emphasis on single shot and online monitoring capabilities in this field. Other topics will be new concepts and experience in measuring the projected and time-sliced emittance of the beam, high precision beam position monitors and sub-picosecond beam phase and arrival time monitor systems.
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FRAAU01	Photon Optics at SCSS	photon, undulator, optics, diagnostics	785
	M. Yabashi, T. Ishikawa RIKEN Spring-8 Harima, Hyogo S. Goto, T. Hirono, H. Kimura, H. Ohashi, S. Takahashi, K. Tamasaku JASRI/SPring-8, Hyogo-ken
	Developments of x-ray optics for the SCSS project are summarized. The optics has two important roles: beam handling (conditioning) and diagnostics. For the former issue, our R&D program for improving qualities of optical components (diamond monochromator, total-reflection mirror, beryllium windows, etc.) are presented. For the latter, a new spectrometer will be introduced. M. Yabashi et al., PRL (in press)
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FRBAU03	Ultrafast Coherent Diffraction Imaging with X-ray Free Electron Lasers	electron, photon, scattering, laser	805
	H. Chapman, S. P. Hau-Riege LLNL, Livermore, California J. Hajdu Uppsala University, Biomedical Centre, Uppsala
	The ultrafast pulses of X-ray FELs allow high-resolution imaging of biological and other soft matter without limitations imposed by radiation damage. A collaboration between LLNL, University of Uppsala, SLAC, TU Berlin, and DESY has carried out high-resolution diffraction imaging of structures using single 25 fs duration, 32 nm wavelength pulses generated by FLASH at DESY. Our objects were placed in the focused FEL beam, with peak intensities up to 10¹⁴ W/cm². The objects were heated to about 60,000 K by the pulse, but destruction only occurred after the pulse traversed the sample. We reconstructed images from the finely-sampled coherent diffraction patterns by phase retrieval using our Shrinkwrap algorithm. These show no evidence of the effects of the pulse on the structure. We also performed quantitative measurements of the explosion of test particles in the focused FEL pulse, by recording their diffraction patterns. No motion occurred during the pulse and we followed the evolution of the explosion with a novel holographic time-resolved technique. Our results confirm the basic principles of flash imaging and lend great confidence to achieving molecular imaging at future short-wavelength X-ray FELs.
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	Talk