FEL2011 - List of Keywords (undulator)

Paper	Title	Other Keywords	Page
MOOA2	First Lasing of the ALICE IR-FEL at Daresbury Laboratory	FEL, cavity, electron, linac	1
	D.J. Dunning, S. Leonard, A.D. Smith STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom J.A. Clarke, Y.M. Saveliev, N. Thompson Cockcroft Institute, Warrington, Cheshire, United Kingdom M. Surman STFC/DL/SRD, Daresbury, Warrington, Cheshire, United Kingdom
	We report the first lasing of the ALICE IR-FEL, an oscillator FEL at the UK’s STFC Daresbury Laboratory. The ALICE (Accelerators and Lasers In Combined Experiments) facility is a testbed for advanced accelerator technologies and experiments, based on an Energy Recovery Linac (ERL) accelerator. First lasing of the ALICE IR-FEL was achieved on October 23rd 2010, making it the first FEL to operate in the UK, and the first FEL based on an ERL accelerator in Europe. First lasing was achieved at 27.5 MeV electron beam energy and 8 μm radiation wavelength. This report describes the steps taken in commissioning the FEL, and the characterisation of the FEL performance and output. Continuous wavelength tuning between 5.7-8 μm (through varying the undulator gap) has been demonstrated.
	Slides MOOA2 [3.435 MB]

MOOA5	Coherent Harmonic Generation at the DELTA Storage Ring	laser, electron, radiation, storage-ring	5
	H. Huck, M. Bakr, M. Höner, S. Khan, R. Molo, A. Nowaczyk, A. Schick, P. Ungelenk, M. Zeinalzadeh DELTA, Dortmund, Germany
	Funding: Supported by DFG, BMBF, and the Federal State NRW First commissioning results from a new Coherent Harmonic Generation (CHG) source, recently installed at the DELTA storage ring, are presented. DELTA, a university-operated synchrotron light source in Dortmund, has successfully operated an optical klystron as storage-ring FEL. After installing a Ti:sapphire laser system and new undulator power supplies earlier this year, the optical klystron can be seeded using ultrashort pulses at 800 nm wavelength and harmonics thereof during standard operation of the storage ring at 1.5 GeV. The energy modulation induced within a short slice of an electron bunch is converted to a density modulation and the micro-bunched electrons emit ultrashort pulses coherently at harmonics of the initial wavelength. Several meters downstream of the optical klystron, path length differences of the energy-modulated electrons cause a dip in the charge distribution, giving rise to coherent ultrashort THz pulses which are extracted using a dedicated beamline.
	Slides MOOA5 [2.605 MB]

MOOBI2	High Harmonics from Gas, a Suitable Source for Seeding FEL from the Vacuum-ultraviolet to Soft X-ray Region	FEL, laser, electron, radiation	9
	G. Lambert, J. Gautier, V. Malka, A. Sardinha, S. Sebban, F. Tissandier, B. Vodungbo, P. Zeitoun LOA, Palaiseau, France B. Carré, D. Garzella CEA/DSM/DRECAM/SPAM, Gif-sur-Yvette, France O.V. Chubar, M.-E. Couprie, M. Labat SOLEIL, Gif-sur-Yvette, France M. Fajardo IPFN, Lisbon, Portugal T. Hara RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan C.P. Hauri Paul Scherrer Institut, Villigen, Switzerland H. Kitamura, T. Shintake RIKEN/SPring-8, Hyogo, Japan J. Lüning CCPMR, Paris, France Y.T. Tanaka JASRI/SPring-8, Hyogo-ken, Japan T. Tanikawa PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
	FEL have been recently evolving very fast in the extreme-ultraviolet to soft X-ray region. Once seeded with high harmonics generated in gas, these light sources deliver amplified emissions with properties which are, for most of them, directly linked to the injected harmonic beam, e.g. the ultrashort pulse duration for FEL and the high temporal and spatial degree of coherence. Since the last two years the developments of techniques for improving the harmonic properties for seeding FEL lead to major results on tunability, intensity, repetition rate and polarization. Actually harmonics are nowadays used for numbers of applications, before limited to FEL facility. Also, FEL based on harmonic seeding can benefit from the natural synchronization between the FEL, the harmonic and the laser used for generation, which makes it a perfect candidate for pump-probe experiment with fs resolution.
	Slides MOOBI2 [1.782 MB]

MOPB07	Soft X-ray Free-electron Laser with a 10-time Reduced Size	electron, FEL, bunching, laser	28
	F.H. Chao, C.H. Chen, K.Y. Huang, Y.-C. Huang NTHU, Hsinchu, Taiwan
	We present a 30-m long soft x-ray FEL consisting of a 5-MeV photoinjector, a 150 MeV linac, a magnetic chicane compressor, and a 3-m long undulator. We propose to employ both the 3rd and the 4th harmonics of a Nd laser at 355 and 266 nm, respectively, to illuminate the cathode of the photoinjector. Owing to the beating of the two lasers, the emitted electron beam could be modulated at 282 THz. The electrons are further accelerated to 150 MeV and, after acceleration, compressed by 33 times in a magnetic chicane. The temporal compression of the electron macropulse increases the electron bunching frequency to 9.3 PHz, corresponding to a soft x-ray wavelength of 32.2 nm. We adopt a solenoid-derived staggered array undulator* with a 3 m length, 5 mm undulator period, and 1.2 mm gap. With a solenoid field of 10 kG, we estimate an undulator parameter of 0.4 and a corresponding radiation wavelength of 32.2 nm for a 150 MeV driving beam. With 3.3 kA peak current, 0.03% energy spread, 2 mm-mrad emittance, and 80-micron beam radius at the undulator entrance, the GENESIS code predicts 0.2 GW radiation power from the 3 m long undulator for an initial bunching factor of merely 10 ppm. * Y.C. Huang, H.C. Wang, R.H. Pantell, and J. Feinstein, "A staggered-array wiggler for far infrared, free-electron laser operation," IEEE J. Quantum Electronics 30 (1994) 1289.

MOPB08	Studies for Polarization Control at LCLS	polarization, FEL, electron, simulation	31
	E. Allaria, Y.T. Ding, P. Emma, Z. Huang, H.-D. Nuhn, M. Rowen, J.J. Welch, J. Wu SLAC, Menlo Park, California, USA
	In order to improve the capabilities of LCLS to meet more of the user requirements it has been proposed to implement a method to produce circularly polarized coherent radiation in the LCLS free electron laser. In this work we will present the results of a new set of studies and simulations that have been done for adding polarization control to LCLS using circularly polarizing undulators. Attention has been focused mainly on the use of variable gap APPLE-II undulators to be used at the end of a long SASE radiator that is based on the standard planar LCLS undulators. Issues like polarization contamination from the planar polarized light, polarization fluctuation and the choice of undulator configuration have been studied.

MOPB15	Numerical Simulation of CAEP Compact FEL THz Source	FEL, cavity, emittance, simulation	35
	L.J. Chen, Q.K. Jia USTC/NSRL, Hefei, Anhui, People's Republic of China M. Li, X. Yang CAEP/IAE, Mianyang, Sichuan, People's Republic of China
	Free Election Laser Terahertz source is a good choice for THz source, whose wavelength is tunable. Using 1D FEL stimulation code FELO, we simulate the output characteristic of China Academy of Engineering Physics (CAEP) FEL THz, which is a waveguide FEL oscillator. The beam qualitys’ influence on the operation of FEL, such as energy dispersion, emittance and beam current, have been studied to designate a set of beam parameters. Besides, the output performance of FEL at different output coupling ratio is analyzed. The cavity detuning is discussed too. Meanwhile the influence of the position of the undulator in the cavity on the FEL performance is also studied.

MOPB16	New Tunable DUV Light Source for Seeding Free-electron Lasers	FEL, laser, simulation, electron	38
	N.Y. Joly, W. Chang, P. Hölzer, J. Nold, P.St.J. Russell, J.C. Travers Max Planck Institute for the Science of Light, Erlangen, Germany M.-E. Couprie, M. Labat SOLEIL, Gif-sur-Yvette, France
	Seeding of single-pass free-electron lasers is a promising approach for improving the temporal coherence compared to self-amplified spontaneous emission [1], at the same time reducing the saturation length and reinforcing the harmonic level. Convention lasers or harmonics generated in gas are usually used as coherent seeds [1]. However such sources require complicated set-up and have limited tuneability. Here, we suggest the use of a newly discovered and efficient source of UV light, continuously tunable from 120 nm to 320 nm. The extremely compact and simple set-up consists of 20 cm of hollow-core photonic crystal fibre filled with a noble gas at variable pressure up to a few tens of bar and pumped by ~1 μJ 30 fs pulses at 800 nm [2]. The process relies on a favourable sequence of linear and nonlinear effects: low pressure-tunable dispersion, pulse compression due to a combination of self-phase-modulation and anomalous dispersion, self-steepening and dispersive wave generation. Tunable diffraction-limited DUV pulses of ~50 nJ and fs duration are generated. Seeding of FEL is discussed. [1] G. Lambert et al., Nature Physics 4, 296-300 (2008) [2] N. Joly et al., accepted in PRL

MOPB17	Harmonic Generation for a Hard X-ray FEL	electron, FEL, emittance, bunching	41
	Q.R. Marksteiner, K. Bishofberger, B.E. Carlsten, L.D. Duffy, N.A. Yampolsky LANL, Los Alamos, New Mexico, USA
	Funding: We gratefully acknowledge the support of the US Department of Energy through the LANL LDRD Propgram for this work. The proposed MaRIE XFEL at Los Alamos National Laboratory will generate ¼ Å, longitudinally coherent x-rays with a 20 GeV electron beam. A masked emittance exchanger can be used to generate coherent electron bunching at nm wavelengths. This masked emittance exchanger must be at 1 GeV in the accelerator, in order to mitigate debunching from incoherent synchrotron radiation (ISR). After this, the harmonic content must be stepped up by a factor of 200 in frequency and the electrons must be accelerated to 20 GeV. The nonlinear debunching effects in the accelerator from emittance must be mitigated by keeping the beam transversely large. There are several schemes to step the coherent bunching up to higher harmonics, all which require modulator and dispersive sections [1]. Echo-Enhanced Harmonic Generation, which requires large dispersion, must be incorporated at low energies, where ISR is reduced. Here we compare the usefulness of different harmonic generation schemes, and examine the possibility of placing successive harmonic generation sections at energies lower than 20 GeV in the accelerator line, with the accelerator sections in between used to introduce dispersion to the beam. [1] Phys. Rev. E 71, 046501 (2005), etc.

MOPB19	Using Laser Harmonics to Increase Bunching Factor in EEHG	bunching, laser, FEL, factory	45
	G.V. Stupakov SLAC, Menlo Park, California, USA M.S. Zolotorev LBNL, Berkeley, California, USA
	Funding: This work was supported by U.S. DOE Contracts No. DE-AC02-76SF00515 and DE-AC02-05CH11231 Echo-enabled harmonic generation (EEHG) is one of most promising approaches to seeding of soft x-ray FELs. It allows one to obtain beam bunching at high harmonics (of order of 100) of the laser frequency at a level of a few percent. In this paper we demonstrate that using the second and third harmonics of the laser radiation one can substantially increase the beam bunching: for a cold beam one can obtain values approaching 0.4 in the range of harmonic numbers 100~200. Such bunching factors are close to those achieved at saturation in the FEL process, which means that one can eliminate the lasing process and use coherent radiation of the pre-bunched beam in the undulator-radiator as a bright source of x-rays. We also discuss an option of using nonlinear dispersive elements to increase the bunching factor.

MOPB20	Effect of Coulomb Collisions on Echo-Enabled Harmonic Generation (EEHG)	bunching, FEL, scattering, emittance	49
	G.V. Stupakov SLAC, Menlo Park, California, USA
	Funding: Work supported by U.S. DOE Contract No. DE-AC02-76SF00515. Echo-enabled harmonic generation (EEHG) for FEL seeding uses two undulator-modulators and two chicanes to introduce a fine structure into the beam longitudinal phase space which, at the end of the system, transforms into high harmonic modulation of the beam current. As a result of this phase space manipulation, after the first chicane, the energy distribution function becomes a rapidly modulated function of energy, with the scale of the modulation of the order of the initial energy spread of the beam divided by the EEHG harmonic number. Small-angle Coulomb collisions between the particles of the beam (also known as intrabeam scattering) tend to smear out this modulation and hence to suppress the beam bunching. In this paper we calculate the EEHG bunching factor with account of the collisions and derive a simple scaling relation for the strength of the effect. Our estimates show that collisions become a limiting factor in EEGH seeding for harmonic numbers roughly exceeding 100.

MOPB25	Improvement of the Crossed Undulator Design for Effective Circular Polarization	polarization, radiation, electron, controls	61
	G. Geloni European XFEL GmbH, Hamburg, Germany V. Kocharyan, E. Saldin DESY, Hamburg, Germany
	The production of X-ray radiation with a high degree of circular polarization constitutes an important goal at XFEL facilities. A simple scheme to obtain circular polarization control with crossed undulators has been proposed so far. In its simplest configuration the crossed undulators consist of pair of short planar undulators in crossed position separated by an electromagnetic phase shifter. An advantage of this configuration is a fast helicity switching. A drawback is that a high degree of circular polarization (over 90%) can only be achieved for lengths of the insertion devices significantly shorter than the gain length, i.e. at output power significantly lower than the saturation power level. Here we propose to use a setup with two or more crossed undulators separated by phase shifters. This cascade crossed undulator scheme is distinguished, in performance, by a fast helicity switching, a high degree of circular polarization (over 95%) and a high output power level, comparable with the saturation power level in the baseline undulator at fundamental wavelength. We present feasibility study and exemplifications for the LCLS baseline in the soft X-ray regime.

MOPB26	Self-seeded Operation of the LCLS Hard X-ray FEL in the Long-bunch Mode of Operation	electron, wakefield, FEL, radiation	65
	G. Geloni European XFEL GmbH, Hamburg, Germany V. Kocharyan, E. Saldin DESY, Hamburg, Germany
	Self-seeding options for the LCLS baseline were recently investigated using a scheme which relies on a single-crystal monochromator in Bragg-transmission geometry. The LCLS low-charge (0.02 nC) mode of operation was considered in order to demonstrate the feasibility of the proposed scheme. The wakefield effects from the linac and from the undulator vacuum chamber are much reduced at such low charge, and can be ignored. In this paper we extend our previous investigations to the case of the LCLS mode of operation with nominal charge. Based on the LCLS start-to-end simulation for an electron beam charge of 0.25 nC, and accounting for the wakefields from the undulator vacuum chamber we demonstrate that the same simplest self-seeding system (two undulators with a single-crystal monochromator in between) is appropriate not only for short (few femtosecond) bunches, but for longer bunches too.

MOPB27	Circular Polarization Control for the LCLS Baseline in the Soft X-ray Regime	radiation, electron, polarization, controls	69
	G. Geloni European XFEL GmbH, Hamburg, Germany V. Kocharyan, E. Saldin DESY, Hamburg, Germany
	Several schemes have been discussed to obtain soft-polarization control in the context of the LCLS. We propose a novel method to generate 10 GW level power at the fundamental harmonic with 99% degree of circular polarization from the LCLS baseline. Its merits are low cost, simplicity and easy implementation. As in previously proposed methods, the microbunching of the planar undulator is used here as well. After the baseline undulator, the electron beam is sent through a 40 m long straight section, and subsequently through a short helical (APPLE II) radiator. The microbunching is easily preserved, and intense coherent radiation is emitted in the helical radiator. The background radiation from the baseline undulator can be suppressed by letting radiation and electrons through horizontal and vertical slits upstream the helical radiator, where the radiation spot size is about ten times larger than the electron bunch transverse size. Thin Be foils for the slits will preserve from electron losses. Other facilities e.g. LCLS II or the European XFEL may benefit from this work as well, due to availability of sufficiently long free space at the end of undulator tunnel.

MOPB29	Generation of Doublet Spectral Lines at Self-seeded X-ray FELs	radiation, electron, FEL, laser	77
	G. Geloni European XFEL GmbH, Hamburg, Germany V. Kocharyan, E. Saldin DESY, Hamburg, Germany
	We propose to extend our recently proposed single-crystal monochromatization setup to the case when two or more crystals are arranged in a series to spectrally filter the SASE radiation at two or more closely-spaced wavelengths within the FEL gain band. This allows for the production of doublet or multiplet spectral lines. We present simulation results for the LCLS baseline operating at two closely spaced wavelengths. We show that we can produce fully coherent radiation shared between two longitudinal modes. Mode spacing can be easily tuned within the FEL gain band. The proposed scheme allows for a modulation of the electron bunch at optical frequencies without a seed quantum laser. In fact, the XFEL output intensity contains an oscillating "mode-beat" component whose frequency is related to the frequency difference between the pair of longitudinal modes considered. At saturation one obtains FEL-induced optical modulations of energy loss and energy spread in the electron bunch, which can be converted into density modulation with a weak chicane behind the baseline undulator. Powerful coherent radiation, synchronized with the X-ray pulses, can then be generated with an OTR station.

MOPB30	The Effects of Betatron Motion on the Preservation of FEL Microbunching	electron, betatron, bunching, emittance	81
	G. Geloni European XFEL GmbH, Hamburg, Germany V. Kocharyan, E. Saldin DESY, Hamburg, Germany
	In some options for circular polarization control at X-ray FELs, a helical radiator is placed a few ten meters distance behind the baseline undulator. If the microbunch structure induced in the baseline (planar) undulator can be preserved, intense coherent radiation is emitted in the helical radiator. The effects of betatron motion on the preservation ofμbunching in such in-line schemes should be accounting for. In this paper we present a comprehensive study of these effects. It is shown that one can work out an analytical expression for the debunching of an electron beam moving in a FODO lattice, strictly valid in the asymptote for a FODO cell much shorter than the betatron function. Further on, numerical studies can be used to demonstrate that the validity of such analytical expression goes beyond the above-mentioned asymptote, and can be used in much more a general context. Finally, a comparison with Genesis simulations is given.

MOPB31	Self-seeding Scheme with Gas Monochromator for Narrow-Bandwidth Soft X-Ray	radiation, electron, FEL, resonance	85
	G. Geloni European XFEL GmbH, Hamburg, Germany V. Kocharyan, E. Saldin DESY, Hamburg, Germany
	We propose an extension of our recently-proposed single-crystal self-seeding scheme to the soft X-ray range using a cell filled with resonantly absorbing gas as monochromator. The transmittance spectrum in the gas exhibits an absorbing resonance with narrow bandwidth. Then, similarly to the hard X-ray case, the temporal waveform of the transmitted radiation pulse is characterized by a long monochromatic wake, whose power is much larger than the equivalent shot noise power in the electron bunch. The monochromatic wake of the radiation pulse is combined with the delayed electron bunch and amplified in the second undulator. The proposed setup is extremely simple, and composed of as few as two simple elements: a gas cell, to be filled with noble gas, and a short magnetic chicane. The installation of the magnetic chicane does not perturb the undulator focusing system and does not interfere with the baseline mode of operation.

MOPB32	System Trade Analysis for an FEL Facility	FEL, photon, linac, emittance	89
	M.W. Reinsch, B. Austin, J.N. Corlett, L.R. Doolittle, G. Penn, D. Prosnitz, J. Qiang, A. Sessler, M. Venturini, J.S. Wurtele LBNL, Berkeley, California, USA
	Designing an FEL from scratch requires the design team to balance multiple science needs, FEL and accelerator physics constraints and engineering limitations. STAFF (System Trade Analysis for an FEL Facility) enables the user to rapidly explore a large range of Linac and FEL design options. The model utilzes analytical models such as the Ming Xie formulas when appropriate and look-up tables when necessary to maintain speed, flexibility and extensiblity. STAFF allows for physics models for FEL harmonics, wake fields, cavity higher-order modes and aspects of linac particle dynamics. The code will permit the user to study error tolerances and multiple beamlines so as to explore the full capabilities of an entire user facility. This makes it possible to optimize the integrated system in terms of performance metrics such as photons/pulse, photons/sec and tunability range while ensuring that unrealistic requirements are not put on either the electron beam quality, undulator field/gap requirements or other system elements. This paper will describe preliminary results from STAFF as applied to a CW FEL soft X-ray facility.

MOPC02	Improvement of Termination Field of Bulk HTSC Staggered Array Undulator	electron, simulation, solenoid, controls	96
	N. Kimura, M. A. Bakr, Y.W. Choi, H. Imon, K. Ishida, T. Kii, R. Kinjo, K. Komai, K. Masuda, H. Ohgaki, M. Omer, S. Shibata, K. Shimahashi, T. Sonobe, K. Yoshida Kyoto University, Institute for Advanced Energy, Kyoto, Japan
	We have proposed a bulk High Temperature Superconductor Staggered Array Undulator (Bulk HTSC SAU) to achieve higher undulator field, shorter period, and variable K-value without changing gap[1]. The purpose of this study is to revise the controversial point, that bulk HTSC SAU generates strong wicked magnetic field on its terminations, which scatters electron beam. Therefore we studied a new method to correct the field. We developed a physical model which based on Bean model to deal with the bulk superconducting material and then constructed a simulation code. By using the calculation results, we developed the correction method by adding bulk material on the edge of undulator. Measurement of the magnetic field of a prototype of bulk HTSC SAU with this method has been performed. We confirm that the numerical calculation well describe the experimental results. In this conference, numerical and experimental results of our end field termination method will be presented. [1] R. Kinjyo, T. Kii, H. Zen, K Higashimura, K Masuda, K. Nagasaki, H. Ohgaki, Y.U. Jeong "Bulk High-TC Super Conductor Staggered Array Undulator" Proceedings of FEL2008

MOPC03	Modeling of the Quiet Start Algorithm in the Framework of the Correlation Function Theory	FEL, simulation, radiation, electron	99
	O.A. Shevchenko, N. Vinokurov BINP SB RAS, Novosibirsk, Russia
	To suppress initial beam current fluctuations at the fundamental harmonic the macroparticle based FEL simulation codes use the quiet start algorithm. This algorithm should be valid at linear stage but there is no simple method to check whether it gives correct results at saturation. The regular approach to the start-up from noise problem should be based on the correlation function equation. In this paper we show that the quiet start algorithm can be naturally described in the framework of the correlation function theory. For this purpose one just needs to assume nonzero correlations in the initial particle distribution. This approach gives the possibility to compare simulation results for the system with reduced number of particles and artificially suppressed initial fluctuations with the case of real system with large number of particles.

MOPC05	HGHG Scheme for FLASH II	electron, simulation, FEL, radiation	107
	A. Meseck, R. Mitzner HZB, Berlin, Germany W. Decking, B. Faatz, M. Scholz DESY, Hamburg, Germany
	FLASH II is a major extension of the existing FLASH facility at DESY. It has been proposed in collaboration with the HZB. FLASH II is a seeded FEL in the parameter range of FLASH. The final layout of the undulator section of FLASH II allows for different seeding schemes. So that seeding with an HHG source as well as seeding in cascaded HGHG scheme and several combination of these schemes are possible. However, for the shortest wavelengths down to 4 nm the cascaded HGHG scheme will be utilized. It consists of two frequency up conversion stages utilizing a Ti:Sa laser based seeding source in UVU range. We present and discuss start-to-end simulation studies for the shortest wavelength generated in the HGHG cascade of FLASH II.

MOPC06	X-Ray FELs Based on ERL Facilities	FEL, radiation, electron, emittance	111
	A. Meseck HZB, Berlin, Germany G.H. Hoffstaetter, F. Löhl, C.E. Mayes CLASSE, Ithaca, New York, USA
	The characteristic high repetition rate and the high spectral brightness of the electron beams delivered by ERLs have led to a large number of ERL based proposals for hard X-ray sources including X-ray FELs. FEL oscillators, including those proposed for hard X-rays, require comparatively low peak currents and are particularly suitable for ERLs. However single-pass FELs in SASE or seeded mode do not seem out of reach when bunch-compression schemes for higher peak currents are utilized. Using the proposed Cornell ERL as an example, we present and discuss oscillator and single-pass FEL schemes which provide extremely high spectral-brightness ultra-short X-ray pulses for experiments.

MOPC09	Use of Re-Acceleration and Tapering in High Gain Free Electron Lasers to Enhance Power and Energy Extraction	FEL, electron, acceleration, extraction	115
	R. Dusad, G. Travish UCLA, Los Angeles, USA
	In high gain Free Electron Lasers (FELs), it is possible to use undulator tapering to increase power and energy extraction beyond saturation. For some applications, however, tapering is not sufficient or results in excessively long structures. Here we the study use of tapered undulators interrupted by short accelerator sections to increase the power extracted per unit length. Re-acceleration restores nominal energy to the beam with minimal disruption to bunching, and allows repeated use of a single taper profile. We show that for suitable parameter sets this approach can perform better than ideal tapering alone, and may serve to greatly improve and simplify high peak and average power FELs. Based on these findings, we propose a first experiment to test the re-acceleration with tapering concept.

MOPC10	Numerical Investigation of Longitudinal Coherence in a Linear Tapered SASE FEL	radiation, FEL, electron, simulation	118
	H.T. Li, Q.K. Jia USTC/NSRL, Hefei, Anhui, People's Republic of China
	One goal of the several FEL facilities operating in soft X-ray range, is the production of high-gain narrow-bandwidth FEL. In this report, the performance of radiation power and longitudinal cohence is studied for x-ray FEL generated through several different methods, including tapered，inverse-tapered and step-tapered undulator, and the SASE-FEL applying distributed optical klystron. Three–dimensional simulation demonstrate that these methods all can increase the FEL power and improve the time and spectrum structure with their own parameter optimization. In particular, FEL generated from toothed undulaor is studied. It is shown that the longitudinal cohence is improved and a series of several fettosecond pulses at gigawatt power levels at a wavelength of 1.5 nm is generated.

MOPC14	Infrared Single Spike Pulses Generation Using a Short Period Superconducting Tape Undulator at APEX	FEL, emittance, space-charge, electron	129
	D. Filippetto, C. F. Papadopoulos, G. Penn, S. Prestemon, F. Sannibale LBNL, Berkeley, California, USA C. Pellegrini UCLA, Los Angeles, California, USA M. Yoon POSTECH, Pohang, Kyungbuk, Republic of Korea
	Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231 We report on the possibility of constructing an infrared FEL by combining a novel design super-conducting undulator developed at LBNL with the high brightness beam from the APEX injector facility at the Lawrence Berkeley National Laboratory. Calculations show that the resulting FEL is expected to deliver a saturated power of about a MW within a 4 m undulator length when operating in Self-Amplified-Spontaneus-Emission mode, with a single-spike of coherent radiation at 2 μm wavelength. The sub-cm undulator periods, associated with the relatively low energy of the APEX beam (20-25 MeV), forces the FEL to operate in a regime with unusual and interesting characteristics. The alternative option of laser seeding the FEL is also examined, showing the potential to reduce the saturation length even further.

MOPC28	Fine Tuning of the K-parameter of Two Segments of the European XFEL Undulator Systems	radiation, electron, simulation, diagnostics	144
	Y. Li, J. Pflüger European XFEL GmbH, Hamburg, Germany E. Gluskin ANL, Argonne, USA N. Vinokurov BINP SB RAS, Novosibirsk, Russia
	For large and segmented undulator systems as needed for the European XFEL a non-destructive, in situ, radiation diagnostics method would strongly compliment e-beam diagnostics. If such method would allow to fine tune the K parameter of individual undulator segments with an accuracy set by the Pierce parameter ρ, which is on the order of 2~3×10^-4, this would provide a very helpful tool for FEL commissioning. This paper provides a first analysis of a strategy of tuning the K parameter of two adjacent undulator segments. The spontaneous, monochromatized, on axis intensity is analyzed as a function of the phase delay set by the phase shifter in between. It makes use of diagnostic equipment which will be available at the European XFEL anyway. First results are demonstrated and limitations will be discussed.

TUOAI1	Hard X-ray Self-seeding for XFELs: Towards Coherent FEL Pulses	electron, radiation, FEL, wakefield	148
	G. Geloni European XFEL GmbH, Hamburg, Germany V. Kocharyan, E. Saldin DESY, Hamburg, Germany
	Start-up from shot noise limits the longitudinal coherence of typical SASE XFEL pulses. Self-seeding schemes provide an elegant solution to this problem. However, their applicability to the baseline of already working or designed XFELs is subject to constraints, including minimal changes to the baseline design and possibility to recover the baseline mode of operation. Here we discuss a recently proposed single-bunch self-seeding scheme for hard X-rays. The physical principles of this scheme can be extended to soft X-rays as well. The method is based on a particular kind of monochromator, which relies on the use of a single crystal in Bragg-transmission geometry. In its simplest configuration, the setup consists of an input undulator and an output undulator separated by such monochromator. Several, more advanced configurations can be considered. For example, for high repetition rates of the X-ray pulses, or when a high spectral purity of the output radiation is requested, the simplest two-undulator configuration is not optimal: three or more undulators separated by monochromators can then be used. Exemplifications, based on facilities working or under construction will be discussed.
	Slides TUOAI1 [2.818 MB]

TUOA4	Toward TW-level, Hard X-ray Pulses at LCLS	electron, FEL, radiation, simulation	160
	W.M. Fawley, J.C. Frisch, Z. Huang, Y. Jiao, H.-D. Nuhn, C. Pellegrini, J. Wu SLAC, Menlo Park, California, USA S. Reiche Paul Scherrer Institut, Villigen, Switzerland
	Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515. Coherent diffraction imaging of complex molecules, like proteins, requires a large number of hard X-ray photons, ~10⁺¹³/pulse, within a time ~10 fs or less. This is equivalent to a peak power of about one TW, much larger than that currently generated by LCLS or other proposed X-ray FELs. We study the feasibility of producing such pulses from LCLS and the proposed LCLS-II, employing a configuration beginning with a SASE amplifier, followed by a "self-seeding" crystal monochromator [1], and finishing with a long tapered undulator. Results suggest that TW-level output power at 8 keV is possible, with a total undulator length below 200 m. We use a 40 pC electron bunch charge, normalized transverse emittance of 0.2-mm-mrad, peak current of 4 kA, and electron energy about 14 GeV. We present a tapering strategy that extends the original "resonant particle" formalism by optimizing the transport lattice to maximize optical guiding and enhance net energy extraction. We also discuss the transverse and longitudinal coherence properties of the output radiation pulse. Fluctuation of such a tapered FEL is studied with realistic jitter measured at LCLS and with start-to-end simulation.
	Slides TUOA4 [9.357 MB]

TUOBI2	First Lasing in the Water Window with 4.1nm at FLASH	FEL, radiation, electron, klystron	164
	S. Schreiber DESY, Hamburg, Germany
	The free-electron laser facility FLASH at DESY, Germany has been upgraded. The electron beam energy has been increased from 1 to 1.25 GeV by adding a 7th superconducting accelerating module. In September 2010, for the first time, lasing in the water window at a fundamental wavelength of 4.1 nm has been achieved. The water window is a wavelength region between 2.3 and 4.4 nm in which water is transparent for light. This remarkable achievement opens the possibility for new class of experiments, especially for biological samples in aqueous solution.
	Slides TUOBI2 [6.481 MB]

TUOBI3	Operational Experience at LCLS	linac, emittance, electron, FEL	166
	H. Loos SLAC, Menlo Park, California, USA
	Funding: *Work supported by DOE contract DE-AC02-76SF00515 The Linac Coherent Light Source (LCLS) X-ray FEL has been operational since 2009 and is delivering soft and hard x-rays to users now in the 4th user run. Reliable operation to deliver x-rays to users, quick machine turn on after shutdowns, and fast configuration changes for the wide range of user requests are particularly important for a facility serving a single user at a time. This talk will discuss procedures to set-up and optimize the accelerator and FEL x-ray beam for user operation. The emphasis will be on the most relevant diagnostics and tuning elements as well as the experience with feedback systems and high level support software to automate FEL operation.
	Slides TUOBI3 [3.074 MB]

TUOC4	Design and First Experience with the FERMI Seed Laser	laser, FEL, insertion, beam-transport	183
	M.B. Danailov, P. Cinquegrana, A.A. Demidovich, R. Ivanov, I. Nikolov, P. Sigalotti ELETTRA, Basovizza, Italy
	Fermi@Elettra is the first fully seeding-based FEL. Laser operation was first demonstrated in December 2010 and later consistently studied during the runs in 2011. It is known that seeded operation puts heavy demands on the seed laser performance. This paper describes the design of the FERMI seed laser system, including the main laser as well as the most important subsystems and the issues that were solved to easily reach seeded operation. The main requirements to the seed were set by the use of High Gain Harmonic Generation FEL scheme and can be found in details in the FERMI CDR. Here we only recall that the seed needs to be broadly tunable in UV (down to 200 nm) with a peak power above 100 MW all over the tunability range. Obviously, such a tunability imposed the use of a parametric amplifier. For the first seeding comissioning, a fixed wavelength scheme was used, allowing much higher peak power. Here we present both solutions, showing the obtained performance and the limitations. The synchronization of the laser to the timing signals was of crucial importance for the successful seeded operation so the last part of the paper to the laser synchronization setup developed for FERMI.
	Slides TUOC4 [1.360 MB]

TUPA04	sFLASH - Present Status and Commisioning Results	electron, laser, radiation, FEL	194
	V. Miltchev, S. Ackermann, A. Azima, J. Bödewadt, F. Curbis, M. Drescher, E. Hass, Th. Maltezopoulos, M. Mittenzwey, J. Rönsch-Schulenburg, J. Roßbach, R. Tarkeshian Uni HH, Hamburg, Germany H. Delsim-Hashemi, K. Honkavaara, T. Laarmann, H. Schlarb, S. Schreiber, M. Tischer DESY, Hamburg, Germany R. Ischebeck Paul Scherrer Institut, Villigen, Switzerland
	The free-electron laser in Hamburg (FLASH) was previously being operated in the self-amplified spontaneous emission (SASE) mode, producing photons in the XUV wavelength range. Due to the start-up from noise the SASE-radiation consists of a number of uncorrelated modes, which results in a reduced coherence. One option to simultaneously improve both the coherence and the synchronisation between the FEL-pulse and an external laser is to operate FLASH as an amplifier of a seed produced using high harmonics generation (HHG). An experimental set-up - sFLASH, has been installed to test this concept for the wavelengths below 40 nm. The sFLASH installation took place during the planed FLASH shutdown in the winter of 2009/2010. The technical commissioning, which began in the spring of 2010, has been followed by FEL-characterization and seeded-FEL commissioning in 2011. In this contribution the present status and the sFLASH commissioning results will be discussed.

TUPA06	Seeding Schemes on the French FEL Project LUNEX5	laser, electron, simulation, FEL	198
	C. Evain, F. Briquez, M.-E. Couprie, M. Labat, A. Loulergue SOLEIL, Gif-sur-Yvette, France V. Malka LOA, Palaiseau, France
	LUNEX5 is a single pass FEL project producing coherent synchrotron radiation with, in a first step, an electron bunch accelerated in conventional RF cavities up to 300 MeV. It is planned to work in a seeded configuration where the longitudinal coherence of the emitted light is improved and the gain length reduced, compared to the SASE configuration (Self-Amplified Spontaneous Emission). Two seeding schemes are considered: High order Harmonic in Gas seeding and EEHG scheme (Echo Enabled Harmonic Generation). Preliminary simulation results indicate that these two schemes permit to reach the saturation below a wavelength of 7 nm, and with less undulator periods for the EEHG scheme. Finally, the feasibility of plasma acceleration based FEL will also be investigated on this facility.

TUPA07	Study of a Silicon Based XFELO for the European XFEL	radiation, electron, cavity, simulation	202
	J. Zemella, D. Novikov, M. Tolkiehn DESY, Hamburg, Germany J. Roßbach Uni HH, Hamburg, Germany H. Sinn European XFEL GmbH, Hamburg, Germany
	For the European XFEL in Hamburg three different SASE undulators are planed whose radiation output have a high peak brilliance up to 5.4·10³³ photon/s/mm²/mrad²/0.1% BW at wavelengths down to below 5·10^-11 m. The radiation pulses are nearly fully coherent in transverse direction but have a poor longitudinal coherence of about 0.3 fs. Several schemes were developed to get a better longitudinal coherence. In this paper an X-ray Free Electron Laser Oscillator is presented whose radiation output is nearly fully coherent in all directions. In contrast to previous schemes it is based on Silicon crystals rather than Diamond. The use of Silicon has the advantage of the availability of perfect crystals in nearly any size and crystal geometry but with a lower reflectivity and heat conduction than Diamond. To overcome the lower round-trip reflectivity of a Silicon cavity a longer undulator has to be used to get a sufficiently large gain. To reduce the heat load an extremely asymmetric crystal geometry has to be used to enlarge the beam spot on the crystal.

TUPA09	LUNEX5: A FEL Project Towards the Fifth Generation in France	laser, FEL, electron, linac	208
	M.-E. Couprie, C. Benabderrahmane, F. Briquez, J. Daillant, J.-C. Denard, C. Evain, P. Eymard, F. Ferrari, J.-M. Filhol, M. Labat, A. Loulergue, P. Marchand, C. Miron, P. Morin, F. Polack SOLEIL, Gif-sur-Yvette, France S. Bielawski, C. Szwaj PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France B. Carré CEA/DSM/DRECAM/SPAM, Gif-sur-Yvette, France N. Delerue, R. Roux, A. Variola LAL, Orsay, France G. Lambert, V. Malka, A. Rousse LOA, Palaiseau, France J. Lüning CCPMR, Paris, France
	LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation) aims at investigating the production of short intense and coherent pulses in the soft X rays region (down to 7 nm on the fifth harmonic). It comprises a free electron laser in the seeded configuration (High order Harmonic in Gas seeding and Echo Enable Harmonic Generation) using a conventional linear accelerator of 300 MeV. The FEL beamline including 15 m of in vacuum (potentially cryogenic undulators) of 15 and 30 mm period is designed so as to also accommodate a Laser Wake Field Accelerator (LWFA) ranging from 0.3 to 1 GeV, relying on electron beam parameters produced and accelerated by either the 60 TW laser of LOA or by the 10 PW APOLLON laser of ILE. After the completion and testing of the FEL with the conventional accelerator installed inside the SOLEIL booster inner area, the FEL line can be transported to a LWFA. A laser could alternatively be implemented at SOLEIL for starting testing the principles of a fifth generation light source.

TUPA13	Present Status and Future Prospects of Project on Utilizing Coherent Light Sources for User Experiments at UVSOR-II	laser, electron, FEL, storage-ring	215
	H. Zen, K. Hayashi, S.I. Kimura, E. Nakamura, J. Yamazaki UVSOR, Okazaki, Japan M. Adachi, M. Katoh Sokendai - Okazaki, Okazaki, Aichi, Japan M. Hosaka, Y. Takashima, N. Yamamoto Nagoya University, Nagoya, Japan T. Takahashi Kyoto University, Research Reactor Institute, Osaka, Japan
	Funding: Quantum Beam Technology Program supported by JST/MEXT (Japan) We have been intensively developing coherent light sources utilizing electron bunches in the storage ring, UVSOR-II, by adding some external components to the ring. After successful generation of coherent synchrotron radiation (CSR) in THz range* and coherent harmonic generation (CHG) in DUV range** by using an intense driving laser, a 5-year new research project named as Quantum Beam Technology Program has been started from FY2008. The project includes introduction of new driving laser system, dedicated undulators and beamlines, and aims at utilizing those coherent radiations for user experiments. The new driving laser system has been installed last year. The undulators and beamlines are now under construction. Installation of those components will be finished before the conference. In the conference, we will report on the present status of system development and future plan of application experiments. M. Shimada et al., Japanese Journal of Applied Physics, vol. 46, pp. 7939-7944 (2007). *M. Labat et al., European Physical Journal D, vol. 44, pp. 187-200 (2007).

TUPA14	Conceptual Layout of a New Short-Pulse Radiation Source at DELTA Based on Echo-Enabled Harmonic Generation	laser, electron, lattice, dipole	219
	R. Molo, M. Bakr, H. Huck, M. Höner, S. Khan, A. Nowaczyk, A. Schick, P. Ungelenk, M. Zeinalzadeh DELTA, Dortmund, Germany
	As an upgrade of the present coherent harmonic generation (CHG) source at the DELTA storage ring, the installation of an additional undulator to implement and study the echo-enabled harmonic generation (EEHG) scheme [1] is planned. Compared to the CHG scheme, EEHG allows to produce radiation of shorter wavelengths, thus reaching more relevant absorption edges. In order to avoid dispersive distortions, all undulators should be placed along a straight line. This requires to increase the length of the present straight section by rearranging several magnets and vacuum components as well as a significant modification of the storage ring optics. [1] G. Stupakov, PRL 102, 074801 (2009)

TUPA15	Status of the SwissFEL Facility at the Paul Scherrer Institute	FEL, linac, electron, emittance	223
	S. Reiche Paul Scherrer Institut, Villigen, Switzerland
	SwissFEL is a X-ray Free-electron Laser facility with a soft and hard X-ray beamline, planned to be built at the Paul Scherrer Institute and to be finished in 2016. It covers the wavelength range from 1 Angstrom to 7 nm. In addition to the SASE operation at the entire wavelength, seeding is foreseen down to a wavelength of 1 nm. We report in this presentation the status of the SwissFEL facility, including the layout, the timeline of the project, the different operation modes and the expected performance of the FEL beamlines.

TUPA19	Operation Modes and Longitudinal Layout for the SwissFEL Hard X-Ray Facility	photon, linac, FEL, wakefield	235
	B. Beutner, S. Reiche Paul Scherrer Institut, Villigen, Switzerland
	The SwissFEL facility will produce coherent, ultrabright, and ultra-short photon pulses covering a wavelength range from 0.1 nm to 7 nm, requiring an emittance between 0.18 to 0.43 mm mrad at bunch charges between 10pC and 200pC. In nominal operation continous changes between these two bunch charges will be offered to the users in order to allow them an individual tradeoff between photon power and pulse length depending on thier requirements. The facility consists of an S-band rf-gun and booster and a C-band main linac, which accelerates the beam up to 5.8 GeV. Two compression chicanes will provide a nominal peak current of about 1-3 kA depending on the charge. In addition special operation setups for ultra short single mode photon pulses and large bandwidth will be availiable to users. In this paper different operation modes including nominal operation as well as special modes are presented and discussed in terms of photon performance and machine stability requiremnts.

TUPA22	FLASH II: A Project Update	kicker, laser, electron, radiation	247
	B. Faatz, V. Ayvazyan, N. Baboi, V. Balandin, W. Decking, S. Düsterer, H.-J. Eckoldt, M. Felber, J. Feldhaus, N. Golubeva, K. Honkavaara, M. Körfer, T. Laarmann, A. Leuschner, L. Lilje, T. Limberg, D. Nölle, F. Obier, A. Petrov, E. Plönjes, K. Rehlich, H. Schlarb, B. Schmidt, M. Schmitz, S. Schreiber, H. Schulte-Schrepping, J. Spengler, M. Staack, K.I. Tiedtke, M. Tischer, R. Treusch, M. Vogt, H.C. Weddig DESY, Hamburg, Germany J. Bahrdt, R. Follath, K. Holldack, A. Meseck, R. Mitzner HZB, Berlin, Germany J. Chen, H.X. Deng, B. Liu SINAP, Shanghai, People's Republic of China M. Drescher, A. Hage, V. Miltchev, R. Riedel, J. Rönsch-Schulenburg, J. Roßbach, M. Schulz, A. Willner Uni HH, Hamburg, Germany M. Gensch HZDR, Dresden, Germany F. Tavella HIJ, Jena, Germany
	FLASH II is an extension of the existing FLASH facility by an undulator line and an experimental Hall of which the construction will start before the end of the year. Aims are to increase beamtime for users and implement HHG seeding for the longer wavelength range from 10 to 40 nm at a reduced repetition rate of 100 kHz. Additional seeding schemes are under discussion as a future option. We will present a progress report of FLASH II.

TUPA26	Beam Commissioning of the SACLA Accelerator	FEL, electron, radiation, alignment	255
	T. Hara, H. Tanaka, K. Togawa RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan T. Hasegawa, Y. Kano, T. Morinaga, Y. Tajiri, S. Tanaka, R. Yamamoto SES, Hyogo-pref., Japan
	The commissioning of the X-ray FEL facility of SPring-8, which is named SACLA (SPring-8 Angstrom Compact free-electron LAser), has been started since February 2011. During the beam commissioning, beam diagnostic system and control system are also tested and improved to enable fine tuning of the machine. The position and energy of the electron beam shows excellent stability and the fault rate of the RF system per hour is currently decreased to less than one. Since coherent OTR hinders the beam profile measurement after full bunch compression, several OTR screens are changed to YAG screens with a partial mask installed in its optics. So far the electron beam is successfully accelerated up to 8 GeV and spontaneous emission was observed with weak bunch compression. For the lasing, the RF parameters are first set so that a 0.1 nC bunch is compressed to 30 fs to obtain 3 kA beam current. Then the transverse beam profile is adjusted to match the focusing condition of the undulator section. In the conference, we will report the beam commissioning of the SACLA accelerator.

TUPA31	Transverse Phase-space Studies for the Electron Optics at the Direct XUV-seeding Experiment at FLASH (DESY)	electron, simulation, emittance, diagnostics	263
	S. Ackermann, V. Miltchev, J. Roßbach Uni HH, Hamburg, Germany
	Funding: BMBF under contract No. 05 ES7GU1 - DFG GrK 1355 - Joachim Herz Stiftung During the shutdown in 2009/2010 the Free-Electron Laser in Hamburg (FLASH) was upgraded with an experiment to study the high-gain-FEL amplification of a laser ‘‘seed'' from a high harmonic generation (HHG) source in the XUV wavelength range-sFLASH. For an optimal FEL-performance knowledge of the electron bunch transverse phase-space as well as control on the electron optics parameters is required. In this contribution the technical design, the present status and the commissioning results of the sFLASH diagnostic stations will be presented. The possible options for transverse phase space characterization will be discussed. An emphasis will be put on the error analysis and the tolerance estimations. Analysis of experimental data from both OTR-screens and wire scanners will be presented and discussed.

TUPB09	Free Electron Lasers in 2011	FEL, electron, laser, free-electron-laser	274
	J. Blau, K. R. Cohn, W.B. Colson, C.M. Pogue, M. Stanton, A.I. Yilmaz NPS, Monterey, California, USA
	Funding: This work has been supported by the Office of Naval Research. Thirty-five years after the first operation of the short wavelength free electron laser (FEL) at Stanford University, there continue to be many important experiments, proposed experiments, and user facilities around the world. Properties of FELs in the infrared, visible, UV, and x-ray wavelength regimes are tabulated and discussed.

TUPB10	Echo Seeding Experiment at FLASH	laser, bunching, electron, FEL	279
	K.E. Hacker, S. Khan DELTA, Dortmund, Germany G. Angelova Hamberg, V.G. Ziemann Uppsala University, Uppsala, Sweden A. Azima Uni HH, Hamburg, Germany P. Salén, P. van der Meulen FYSIKUM, AlbaNova, Stockholm University, Stockholm, Sweden H. Schlarb DESY, Hamburg, Germany
	Using the two perpendicularly oriented undulators and chicanes developed for an optical replica synthesizer (ORS) experiment together with the sFLASH 800 nm seed laser, radiator undulators and diagnostics, an echo seeding experiment will be conducted at FLASH in January 2012. For this experiment, the 800 nm laser pulse will be transported with a new, 12 meter long, in-vacuum laser transport line. On an in-vacuum optical breadboard, the 800 nm pulse will then be tripled in beta-BBO nonlinear crystals. The laser pulse will then be split longitudinally using a birefringent alpha BBO crystal into two pulses with orthogonal polarization states corresponding to the orthogonal orientations of the ORS undulators. These pulses will be focused to a 400 μm waist between the undulators with a Galileo telescope and steered with 4 motorized mirrors onto the electron beam axis in the ORS undulator section. The hardware layout and simulations of the echo seeding parameters will be described.

TUPB21	Conceptual Design of a High Brightness and Fully Coherent Free Electron Laser in VUV Regime	FEL, laser, electron, radiation	302
	D. Wang, T. Zhang, Z.T. Zhao SINAP, Shanghai, People's Republic of China X.M. Yang DICP, Dalian, People's Republic of China
	In this paper we propose a new generation light source based on the High Gain Harmonic Generation (HGHG) Free Electron Laser (FEL) for scientific researches. This facility is designed to cover wavelength range from 50 nm to 150 nm with high brightness and full coherence by using the continuously tuning Optical Parametric Amplifier (OPA) seed laser system and variable gap undulators.

TUPB22	THz Pump and X-Ray Probe Development at LCLS	electron, FEL, laser, radiation	304
	A.S. Fisher, H.A. Durr, J.C. Frisch, M. Fuchs, S. Ghimire, J.J. Goodfellow, A. Lindenberg, H. Loos, M. Petree, D.A. Reis SLAC, Menlo Park, California, USA D.R. Daranciang Stanford University, Stanford, California, USA
	Funding: This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under contract DE-AC02-76SF00515. We report on measurements of broadband, intense, coherent transition radiation at terahertz frequencies, generated as the highly compressed electron bunches in LCLS pass through a thin metal foil. The foil is inserted at 45 degrees to the electron beam, 30 m downstream of the undulator. The THz emission passes downward through a diamond window to an optical table below the beamline. A fully compressed 350-pC bunch produces over 0.5 mJ in a nearly half-cycle pulse of 50 fs FWHM with a spectrum peaking at 10 THz. We estimate a peak field at the focus of over 2.5 GV/m. Electro-optic measurements using a newly installed 20-fs Ti:sapphire oscillator will be presented. We will discuss plans to add a THz pump and x-ray probe setup, in which a thin silicon crystal diffracts FEL light onto the table with adjustable time delay from the THz. This will provide a rapid start to user studies of materials excited by intense single-cycle pulses and will serve as a step toward a THz transport line for LCLS-II.

TUPB28	Considerations for a Light Source Test Facility at Daresbury Laboratory	electron, FEL, laser, emittance	308
	N. Thompson STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom J.A. Clarke, D.J. Dunning, J.W. McKenzie Cockcroft Institute, Warrington, Cheshire, United Kingdom
	This paper considers design options for a dedicated light source test facility at Daresbury Laboratory in the United Kingdom. The facility layout should be easily configurable to enable exploration of many research themes including: ultrashort pulse generation; seeding and harmonic generation; direct laser/electron beam interactions; compact FELs; high brightness photoinjectors. The strategy is to develop and demonstrate novel concepts and expertise relevant to future generations of FEL-based light sources, significantly shortening the R&D phase of any future light source in the UK.

TUPB29	Status of the FERMI@Elettra Project	FEL, linac, photon, laser	312
	M. Svandrlik, E. Allaria, E. Busetto, C. Callegari, D. Cocco, P. Craievich, I. Cudin, G. D'Auria, M.B. Danailov, S. Di Mitri, B. Diviacco, A. Fabris, R. Fabris, M. Ferianis, R. Gobessi, E. Karantzoulis, M. Kiskinova, M. Lonza, C. Masciovecchio, S. Noè, F. Parmigiani, G. Penco, M. Trovò, A. Vascotto, R. Visintini, M. Zaccaria, D. Zangrando, M. Zangrando ELETTRA, Basovizza, Italy
	FERMI@Elettra is a seeded FEL user-facility covering the wavelength range from 100 nm (12 eV) to 4 nm (310 eV) located next to the third-generation synchrotron light source Elettra in Trieste, Italy. The facility is based on a normal conducting linac and covers the wavelength range with two FEL lines, FEL-1 and FEL-2. A photon distribution and diagnostic system transports the photons from the end of the two FEL lines to three experimental stations. Beneficial occupancy of the new undulator hall and experimental hall was given end of Summer 2010 when also all auxiliary systems were made available. The installation of the machine is now almost completed; commissioning of the linac has started in parallel to the installation activities and now commissioning of FEL-1 is in a well advanced status. The first seeded lasing from FEL-1 was actually observed in December 2010 and first experiments are starting in 2011. In this paper an overview of the facility will be given as well as the general status of installation and commissioning and a perspective into future developments and user programs.

TUPB30	Status of the Fritz Haber Institute THz FEL	electron, FEL, cavity, linac	315
	W. Schöllkopf, W. Erlebach, S. Gewinner, H. Junkes, A. Liedke, G. Meijer, W.Q. Zhang, G. von Helden FHI, Berlin, Germany H. Bluem, V. Christina, M.D. Cole, J. Ditta, D. Dowell, R. Lange, J.H. Park, J. Rathke, T. Schultheiss, A.M.M. Todd, L.M. Young AES, Princeton, New Jersey, USA S.C. Gottschalk STI, Washington, USA K. Jordan Kevin Jordan PE, Newport News, Virginia, USA U. Lehnert, P. Michel, W. Seidel, R. Wünsch FZD, Dresden, Germany
	The THz FEL at the Fritz Haber Institute (FHI) in Berlin is designed to deliver radiation from 4 to 400 microns. A single-plane-focusing undulator combined with a 5.4 m long cavity is used is the mid-IR (< 50 micron), while a two-plane-focusing undulator in combination with a 7.2 m long cavity with a 1-d waveguide for the optical mode is used for the far-IR. A key aspect of the accelerator performance is low longitudinal emittance, < 50 keV-psec, at 200 pC bunch charge and 50 MeV from a gridded thermionic electron source. We utilize twin accelerating structures separated by a chicane to deliver the required performance over the < 20 - 50 MeV energy range. The first structure operates at near fixed field while the second structure controls the output energy, which, under some conditions, requires running in a decelerating mode. "First Light" is targeted for the centennial of the FHI in October 2011 and we will describe progress in the commissioning of this device. Specifically, the measured performance of the accelerated electron beam will be compared to design simulations and the observed matching of the beam to the mid-IR wiggler will be described.

WEOA2	SASE FEL Pulse Duration Analysis from Spectral Correlation Function	electron, FEL, simulation, radiation	318
	A.A. Lutman, Y.T. Ding, Y. Feng, Z. Huang, J. Krzywinski, M. Messerschmidt, J. Wu SLAC, Menlo Park, California, USA
	Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515. A new method to measure the X-rays pulse duration through the analysis of the statistical properties of the SASE FEL spectra has been developed. The information on the pulse duration is contained in the correlation function of the intensity spectra measured after a spectrometer. The spectral correlation function is derived analytically for different profile shapes in the exponential growth regime and issues like spectral central frequency jitter and shot by shot statistical gain are addressed. Numerical simulations will show that the method is applicable also in saturation regime and that both pulse duration and spectrometer resolution can be recovered from the spectral correlation function. The method has been experimentally demonstrated at LCLS, measuring the soft X-rays pulse durations for different electron bunch lengths, and the evolution of the pulse durations for different undulator distances. Shorter pulse durations down to 13 fs FWHM have been measured using the slotted foil.
	Slides WEOA2 [0.758 MB]

WEPA14	Effect of a Quasiperiodic Undulator on FEL Radiation	radiation, electron, FEL, free-electron-laser	352
	F. Briquez, C. Benabderrahmane, M.-E. Couprie, C. Evain, M. Labat SOLEIL, Gif-sur-Yvette, France
	The operation of conventional undulators results from an interference scheme in order to generate radiation of a fundamental wavelength and its harmonics. Whereas these harmonics are in most of the cases useful to reach higher energies, it is profitable in specific configurations to shift or reduce them, for instance to limit power on optics or to distinguish between one or two photon process in user experiments. This can be performed by so-called quasi-periodic undulators in which the periodicity of the magnetic field is destructed. In this case, the field amplitude is reduced on a few positions among the axis, inducing a destruction of the interference scheme. Such undulators are commonly used to generate spontaneous emission in synchrotron radiation facilities but could also be installed in Free Electron Lasers. The emitted radiation of the quasi-periodic undulator is compared with the usual configuration one, in the case of LUNEX5. Simulations using GENESIS code are described and results are discussed.

WEPA22	Development of Insertion Devices Measurement System at IHEP	alignment, insertion, controls, insertion-device	381
	W. Chen, X. Feng, H.H. Lu, C. Shi, Y. Yang, J.C. Zhang IHEP, Beijing, People's Republic of China
	In the cooperation between IHEP and EXFEL, prototype undulator U48 for EXFEL is developed by IHEP. In order to meet, maintain and verify the ID’s magnetic performance, a magnetic measurement system has been developed. The development status of the system at IHEP is described in this paper. A 6.5 m long measurement bench with hall probe and small coil is used to measure the vertical and horizontal components of the Insertion Device magnetic field. The measurement system includes a precise granite bench to position and move the magnetic sensors, motion control part and data acquisition part. The characteristics and performances of the magnetic measurement system are presented.

WEPA24	Error Analysis for Hybrid Undulators	insertion, insertion-device, free-electron-laser, laser	387
	D. Arbelaez, A. Madur, S. Marks, S. Prestemon, D. Schlueter LBNL, Berkeley, California, USA H.-D. Nuhn SLAC, Menlo Park, California, USA
	Funding: This work was supported by the Director, Office of Science, of the US Department of Energy under Contract No. DE-AC02-05CH11231. An analysis is performed on various possible errors that may occur throughout a hybrid undulator. Of particular significance is the scaling of the various errors with variations in the gap of the device. Tuning strategies are considered for the mitigation of these errors for the entire range of usable gap. Sorting strategies for the reduction of the initial errors in the undulator are also considered. Specifically, the effectiveness of the sorting algorithm is evaluated with respect to the number of permanent magnet blocks used per pole as well as the size and distribution of the block population. The results of this analysis are applied to the LCLS-II undulators to determine the required machining and positioning tolerances and viable tuning strategies in order to meet the design requirements.

WEPB02	Study of Highly Isochronous Beamlines for FEL Seeding	bunching, FEL, quadrupole, laser	391
	C. Sun, H. Nishimura, G. Penn, M.W. Reinsch, D. Robin, F. Sannibale, C. Steier, W. Wan LBNL, Berkeley, California, USA
	Recently seeding schemes, such as ECHO for short (nm) wavelength FELs, have been proposed. These schemes require that the nm level longitudinal bunch structure be preserved over distance of several meters. This poses a challenge for the beamline design. In this paper we present our studies of several solutions for beamlines that are nearly isochronous.

WEPB03	LCLS-II Undulator Tolerance Analysis	FEL, simulation, electron, radiation	394
	H.-D. Nuhn, J. Wu SLAC, Menlo Park, California, USA S. Marks LBNL, Berkeley, California, USA
	Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515 The SLAC National Accelerator Laboratory is constructing the new FEL user facility LCLS-II, as a major upgrade to the Linear Coherent Light Source (LCLS). The upgrade will include two new Free Electron Lasers, to generate soft (SXR) and hard X-ray (HXR) SASE FEL radiation, based on planar, variable gap hybrid undulators with two different undulator periods (SXR 55 mm, HXR 32 mm). An systematic FEL tolerance analysis for the undulator lines, including tuning, alignment, yaw deformation, and phase correction tolerances has been performed. The methods and results are presented in this work.

WEPB04	Position Stability Monitoring of the LCLS Undulator Quadrupoles	quadrupole, controls, ground-motion, monitoring	398
	H.-D. Nuhn, G.L. Gassner, F. Peters SLAC, Menlo Park, California, USA
	Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515 In the era of SASE FELs, the demand for position stability of undulator components scales down to the range of sub-micrometers per day. Simultaneously, the undulator length increases significantly, in order to reach X-ray wavelengths. To minimize the impact of the outside environment, the LCLS undulator is placed underground, but reliable data about ground motion inside such a tunnel were not available in the required stability range. Therefore, a new position monitor system has been developed and installed for the LCLS undulator. That system is capable to measure X-, Y- and Roll positions of each of the 33 undulator quadrupoles, with respect to stretched wires. Instrument resolution is about 20 nm and instrument drift is negligible small. Position data of individual quadrupoles can be correlated along the entire undulator, which has a length of 132 m. The system is under continuous operation since 2009. The report describes long term experience with the running system and the observed position stability of the undulator quadrupoles.

WEPB14	Ultra-short Electron Bunch and X-ray Temporal Diagnostics with an X-band Transverse Deflector	FEL, electron, radiation, diagnostics	405
	C. Behrens DESY, Hamburg, Germany Y.T. Ding, P. Emma, J.C. Frisch, Z. Huang, P. Krejcik, H. Loos, M.-H. Wang SLAC, Menlo Park, California, USA
	The measurement of ultra-short electron bunches on the femtosecond time scale constitutes a very challenging problem. In X-ray free-electron laser facilities such as the Linac Coherent Light Source (LCLS), generation of sub-ten femtosecond X-ray pulses is possible, and some efforts have been put into both ultra-short electron and X-ray beam diagnostics. Here we propose a single-shot method using a transverse deflector (X-band) after the undulator to reconstruct both the electron bunch and X-ray temporal profiles. Simulation studies show that about 1 fs (rms) time resolution may be achievable in the LCLS and is applicable to a wide range of FEL wavelengths and pulse lengths. The jitter, resolution and other related issues will be discussed.

WEPB16	Study for Evaluation of Undulator Magnetic Field Using Vibrating Wire Method	electron, resonance, radiation, damping	413
	Y. Tanaka Tohoku University, School of Science, Sendai, Japan H. Hama, F. Hinode, S. Kashiwagi, M. Kawai, X. Li, T. Muto, K. Nanbu Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
	A test accelerator for a terahertz source project (t-ACTS) has been progressed at the Electron Light Science Centre, Tohoku University, in which a generation of intense coherent terahertz radiation from the very short electron bunch will be demonstrated. A narrow-band coherent terahertz radiation using an undulator has been considered to be implemented. We have constructed a planer undulator that is basically a Halbach type composed of permanent magnet blocks. The period length of the undulator and the number of periods are 100 mm and 25, respectively. The vibrating wire method is studied to measure the periodic magnetic field of the undulator. A thin copper-beryllium wire is placed on beam axis in the undulator, and an AC current flow is applied in the wire. By measuring amplitudes and phases of standing waves excited on the wire by the Lorentz force between AC current and magnetic field, we can reconstruct the magnetic field distribution along the wire. We discuss relations between reproducibility of the undulator field and the mode harmonics number used for the reconstruction. The results of preliminary measurement using the vibrating wire will be shown in this conference.

WEPB17	Evaluation of Lasing Range with a 1.8 m Undulator in KU-FEL	FEL, electron, cavity, gun	417
	K. Ishida, M. A. Bakr, Y.W. Choi, H. Imon, T. Kii, N. Kimura, R. Kinjo, K. Komai, K. Masuda, H. Ohgaki, M. Omer, S. Shibata, K. Shimahashi, T. Sonobe, K. Yoshida, H. Zen Kyoto University, Institute for Advanced Energy, Kyoto, Japan
	In KU-FEL (Kyoto University FEL) 12-14 μm FEL has been available by using a 40 MeV S-bend linac and 1.6 m undulator. We are going to install 1.8 m undulator which was used in JAEA to extend the lasing range of KU-FEL. Numerical evaluation of the lasing range has been carried out by using GENESIS1.3. However, this work used an ideal undulator field data which was measured by JAEA in several years before. Therefore we re-measured the undulator field for different gaps. Then we evaluated the FEL gain and possible lasing range with 1.8 m undulator using measured undulator field. The undulator field measurement, FEL gain calculations and evaluation of lasing range in KU-FEL will be presented in the conference.

WEPB18	Development of the First U48 Undulator Prototype for the European X-ray Free Electron Laser	controls, alignment, FEL, laser	420
	H.H. Lu, W. Chen, X. Feng, X.M. Jiang, C. Shi, S.C. Sun, M.T. Wang, Z.X. Wang, Y.F. Yang IHEP, Beijing, People's Republic of China Y. Li, J. Pflüger European XFEL GmbH, Hamburg, Germany
	Funding: MOST973 Program The European XFEL will be a user facility consisting of three beamlines named SASE1/2/3 at the first stage. The first undulator prototype U48 for the European XFEL SASE2 beamline has been developed and tested by IHEP, China. Its magnetic design and specifications are briefly given. Development of U48, including magnetic material, mechanical structure, control system and assembly, are introduced. Magnetic tuning and test results are presented and discussed.

WEPB19	Enhancement of Undulator Field in Bulk HTSC Staggered Array Undulator with Hybrid Configuration	solenoid, synchrotron, radiation, ion	424
	R. Kinjo, M. A. Bakr, Y.W. Choi, H. Imon, K. Ishida, T. Kii, N. Kimura, K. Komai, K. Masuda, K. Nagasaki, H. Ohgaki, M. Omer, S. Shibata, K. Shimahashi, T. Sonobe, K. Yoshida, H. Zen Kyoto University, Institute for Advanced Energy, Kyoto, Japan
	Funding: This work was supported by the Grant-in-Aid for Scientific Research B and JSPS Fellows by the Ministry of Education, Culture, Sports, Science and Technology of Japan The purpose of this study is enhancement of the undulator field and it's stability in bulk high temperature superconductor staggered array undulator by introducing hybrid configuration. The authors made the magnetic field calculations with some hybrid configurations consists of bulk HTSCs, ferromagnetic pieces and permanent magnets. We also made prototype measurements. The results shows the hybrid configuration can generates stronger and more uniform magnetic field than bulk-HTSCs-only configuration. In this conference, numerical and experimental results of the hybrid configuration will be presented.

THOAI1	Pushing the Limits of Short Period Permanent Magnet Undulators	vacuum, permanent-magnet, cryogenics, FEL	435
	J. Bahrdt HZB, Berlin, Germany
	Short period undulators to be used as FEL radiators permit lower electron energies and, thus, reduce linac and undulator lengths. The first X-ray FEL facility based on in-vacuum undulators goes into operation soon (SPRING-8 XFEL). Other in-vacuum undulator based FELs are under construction (SWISS-FEL) or are planned. The in-vacuum undulators have period lengths between 18mm (SPRING-8-X-FEL) and 15mm (SWISS-FEL). In the future the period length will be pushed further into the sub-cm regime. The technical implications of these devices will be discussed: New materials such as PrFeB-magnets are employed. They show their superior characteristics at cryogenic temperatures. Geometric and magnetic tolerances will be tighter and the construction and shimming concepts have to be revised. New magnetic measurement systems are required as well. Recently, a 9mm period length 20 period prototype undulator has been built in collaboration between Ludwig-Maximilian-University Munich and Helmholtz-Zentrum Berlin. The potential and the challenges of sub-cm undulators will be illustrated based on first results from this prototype.
	Slides THOAI1 [3.344 MB]

THOA4	Three Bunch Compressor Scheme for SASE FEL	linac, emittance, FEL, electron	447
	H.-S. Kang, I.S. Ko, S.H. Nam PAL, Pohang, Kyungbuk, Republic of Korea M.-H. Cho, C.H. Yi POSTECH, Pohang, Kyungbuk, Republic of Korea
	The bend angle of dipoles in bunch compressor needs to be small enough to reduce the emittance increase due to CSR, which requires a larger energy chirp at the preceding RF linac. Correlated energy spread is not reduced below FEL parameter after the following RF linac because of the small number of accelerating sections as in the PAL XFEL design. Three bunch compressor scheme can make it possible to minimize the CSR induced emittnace growth as well as reduce the correlated energy spread below FEL parameter.
	Slides THOA4 [1.467 MB]

THOB3	First Demonstration of a Slippage-dominant Superradiant Free-electron Laser Amplifier	FEL, electron, laser, simulation	455
	X. Yang, Y. Hidaka, B. Podobedov, S. Seletskiy, Y. Shen, X.J. Wang BNL, Upton, Long Island, New York, USA
	We report the first experimental demonstration of a slippage-dominant superradiant free-electron laser (FEL) using an ultrafast seed-laser pulse. We measured the evolution of the longitudinal phase space in the slippage-dominant superradiant regime, and also the output spectrum and pulse energy versus the electron beam energy. With a ±1% variation in the electron beam energy, we observed a seed-like fully longitudinal coherence, and ±2% spectral tuning range. The temporal and spectral evolution of the slippage-dominant FEL radiation as predicted by a numerical simulation was experimentally verified for the first time.
	Slides THOB3 [0.374 MB]

THOB4	Transverse Coherence and Polarization Measurement of Coherent Femtosecond Pulses from a Seeded FEL	polarization, FEL, laser, electron	458
	J. Schwenke, N. Čutić, F. Lindau, S. Werin MAX-lab, Lund, Sweden E. Mansten Lund University, Division of Atomic Physics, Lund, Sweden
	We report on measurements of the transverse coherence and polarization of light pulses at 131 nm generated by a seeded free-electron laser. Our setup consists of two undulators. The first undulator is used to energy modulate relativistic electron bunches (375 MeV) with the help of an ultraviolet seed laser pulse at 263 nm. The electron bunches subsequently pass through a dispersive section, where the energy modulation is converted into microbunching, and then enter the radiator undulator. The radiator is an APPLE-II type undulator set to be in resonance for 131 nm radiation. The radiator emits coherent femtosecond pulses up to the 6th harmonic of the seed laser [1]. The state of polarization of the pulses can be tuned from planar to helical polarization by shifting the undulator magnets. The emitted pulses are analyzed with a grating spectrometer. A double slit aperture is positioned in the beam in order to determine the transverse coherence of the light pulses by analyzing the fringe visibility. Furthermore, the generation of circular polarized light is demonstrated. The polarization state of the light pulses is measured with a Rochon prism polarizer. [1] Cutic et al, Phys. Rev. Spec. Top-AC 14, 030706 (2011)
	Slides THOB4 [1.173 MB]

THOB5	FEL Spectral Measurements at LCLS	FEL, electron, photon, laser	461
	J.J. Welch, F.-J. Decker, Y.T. Ding, P. Emma, A.S. Fisher, J.C. Frisch, Z. Huang, R.H. Iverson, H. Loos, M. Messerschmidt, H.-D. Nuhn, D.F. Ratner, J.L. Turner, J. Wu SLAC, Menlo Park, California, USA
	Funding: Work supported in part by the DOE Contract DE-AC02-76SF00515. Control and knowledge of the spectrum of FEL X-ray radiation at the LCLS is important to the quality and interpretation of experimental results. Narrow bandwidth is useful in experiments requiring high-brightness beams. Wide bandwidth is particularly useful for photon energy calibration using absorption spectra. Since LCLS was commissioned in 2009 measurements have been made of average and single shot spectra of X-ray FEL radiation at the LCLS over a range of 800 to 8000 eV, for fundamental and harmonic radiation. These include correlations with chirp, bunch current, undulator K-taper, electron beam energy, and charge as well as some specialized machine configurations. In this paper we present results and discuss the relationship of the electron beam energy distribution to the observed X-ray spectrum.
	Slides THOB5 [0.442 MB]

THOC4	Transverse Size and Distribution of FEL X-ray Radiation of the LCLS	simulation, electron, FEL, background	465
	J.L. Turner, F.-J. Decker, Y.T. Ding, P. Emma, J.C. Frisch, K. Horovitz, Z. Huang, R.H. Iverson, J. Krzywinski, H. Loos, M. Messerschmidt, S.P. Moeller, H.-D. Nuhn, D.F. Ratner, J.J. Welch, J. Wu SLAC, Menlo Park, California, USA
	Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515 Understanding and controlling the transverse size and distribution of FEL X-ray radiation of the LCLS at the SLAC National Accelerator Laboratory is discussed. Understanding divergence, source size, and distributions under various conditions is a convolution of many effects such as the electron distribution, the undulator alignment, micro-bunching suppression, and beta-match. Measurements of transverse size along the X-ray pulse and other studies designed to sort out the dominant effects are presented and discussed.
	Slides THOC4 [1.874 MB]

THPA24	Development of Pr₂Fe₁₄B Cryogenic Undulator CPMU at SOLEIL	cryogenics, vacuum, permanent-magnet, electron	523
	C. Benabderrahmane, P. Berteaud, N. Béchu, L. Chapuis, M.-E. Couprie, J.P. Daguerre, J.-M. Filhol, C. Herbeaux, A. Lestrade, M. Louvet, J.L. Marlats, K. Tavakoli, M. Valléau, D. Zerbib SOLEIL, Gif-sur-Yvette, France
	Short period, high field undulators can enable short wavelength FEL at low beam energy, with decreased gain length, thus allowing much more compact and less costly FEL systems. A R&D programme for the construction of a 2 m long 18 mm period CPMU is under progress at SOLEIL. The use of PrFeB which features a 1.35 T remanence (Br) at room temperature enables to increase the peak magnetic field at 5.5 mm minimum gap, from 1.04 T at room temperature to 1.15 T at a cryogenic temperature of 77 K. For FELs, we can reach higher magnetic field of 1.91 T at lower gap of 3 mm. Pr was chosen instead of Nd magnetic material, because of the no appearance of the SRT phenomenon. Different corrections were performed first at room temperature to adjust the phase error, the electron trajectory and to reduce the multipolar components. The mounting inside the vacuum chamber enables the fitting of a dedicated magnetic measurement bench to check the magnetic performance of the undulator at low temperature. The results of the magnetic measurements at low temperature and the comparison with the measurement at room temperature are reported. A U18 CPMU will be used in LUNEX5 project at SOLEIL.

THPA25	Standard Electron Beam Diagnostics for the European XFEL	electron, cavity, diagnostics, dipole	527
	D. Lipka DESY, Hamburg, Germany
	The European XFEL under construction in Hamburg needs to control the electron beam parameters for reliable machine and FEL operation. Due to the flexible bunch pattern, a minimum bunch spacing of 222 ns and large beam charge range a high dynamic range of the monitors is necessary. Furthermore the high average beam power enforces an elaborated machine protection system. This paper presents an overview of the planned standard electron beam diagnostics. The status of the main systems is presented, as well as the results from prototype tests with beam at FLASH.

THPA29	Performance of the RF Cavity BPM at XFEL/SPring-8 “SACLA”	cavity, electron, factory, low-level-rf	539
	H. Maesaka, T. Ohshima, Y. Otake RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan H. Ego, S. Matsubara JASRI/SPring-8, Hyogo-ken, Japan S.I. Inoue SES, Hyogo-pref., Japan T. Shintake RIKEN Spring-8 Harima, Hyogo, Japan
	We have developed an rf cavity beam position monitor (RF-BPM) for the XFEL facility at SPring-8, “SACLA”. The demanded position resolution of the BPM is less than 1 μm, because an electron beam and X-rays must be overlapped with 4 μm precision in the undulator section. To achieve this requirement, we employed a C-band RF-BPM that has a resonant frequency of 4760 MHz. The RF-BPM has a TM110 dipole mode resonator for position detection and a TM010 monopole mode resonator for phase reference and charge normalization. Rf signals from the RF-BPM are detected by IQ (In-phase and Quadrature) demodulators and the detected signals are recorded by 238 MHz waveform digitizers. The position resolution was confirmed to be 0.2 μm by using a 250 MeV electron beam at the SCSS test accelerator. Then, 57 RF-BPMs were produced and installed into SACLA. The beam tuning of SACLA started in February 2011 and the RF-BPM system has been working well. We report the basic performance such as a resonant frequency, a Q factor, machining accuracy etc. for each cavity and the achieved position resolution of the RF-BPM system.

THPB31	Multiple FELs from the One LCLS Undulator	FEL, electron, quadrupole, linac	629
	F.-J. Decker, P. Emma, J.C. Frisch, K. Horovitz, Z. Huang, R.H. Iverson, J. Krzywinski, H. Loos, S.P. Moeller, H.-D. Nuhn, J.L. Turner, J.J. Welch, J. Wu SLAC, Menlo Park, California, USA
	Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Science, under Contract DE-AC02-76SF00515. The FEL of the Linac Coherent Light Source (LCLS) at SLAC is generated in a 132 m long undulator. By introducing a kink in the undulator setup and launching different electron pulses with a small kick, we achieved two FEL beams with a separation of about 10 σ. These beams were separated at down stream mirrors and brought to the entrances of the soft and hard X-ray hutches. This was done at low energy creating soft X-rays which require only a shorter length to get to saturation. At high energy the whole undulator has to be "re-pointed" pulse by pulse. This can be done using 33 undulator correctors creating two straight lines for the photons with small angle to point the FEL to different mirrors pulse by pulse even at high energy. Experiments will be presented and further ideas discussed to get different energy photons created and sent to the soft and hard X-ray mirrors and experiments.

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MOOA2

First Lasing of the ALICE IR-FEL at Daresbury Laboratory

FEL, cavity, electron, linac

1

D.J. Dunning, S. Leonard, A.D. Smith
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
J.A. Clarke, Y.M. Saveliev, N. Thompson
Cockcroft Institute, Warrington, Cheshire, United Kingdom
M. Surman
STFC/DL/SRD, Daresbury, Warrington, Cheshire, United Kingdom

We report the first lasing of the ALICE IR-FEL, an oscillator FEL at the UK’s STFC Daresbury Laboratory. The ALICE (Accelerators and Lasers In Combined Experiments) facility is a testbed for advanced accelerator technologies and experiments, based on an Energy Recovery Linac (ERL) accelerator. First lasing of the ALICE IR-FEL was achieved on October 23rd 2010, making it the first FEL to operate in the UK, and the first FEL based on an ERL accelerator in Europe. First lasing was achieved at 27.5 MeV electron beam energy and 8 μm radiation wavelength. This report describes the steps taken in commissioning the FEL, and the characterisation of the FEL performance and output. Continuous wavelength tuning between 5.7-8 μm (through varying the undulator gap) has been demonstrated.

Slides MOOA2 [3.435 MB]

MOOA5

Coherent Harmonic Generation at the DELTA Storage Ring

laser, electron, radiation, storage-ring

5

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

Funding: Supported by DFG, BMBF, and the Federal State NRW
First commissioning results from a new Coherent Harmonic Generation (CHG) source, recently installed at the DELTA storage ring, are presented. DELTA, a university-operated synchrotron light source in Dortmund, has successfully operated an optical klystron as storage-ring FEL. After installing a Ti:sapphire laser system and new undulator power supplies earlier this year, the optical klystron can be seeded using ultrashort pulses at 800 nm wavelength and harmonics thereof during standard operation of the storage ring at 1.5 GeV. The energy modulation induced within a short slice of an electron bunch is converted to a density modulation and the micro-bunched electrons emit ultrashort pulses coherently at harmonics of the initial wavelength. Several meters downstream of the optical klystron, path length differences of the energy-modulated electrons cause a dip in the charge distribution, giving rise to coherent ultrashort THz pulses which are extracted using a dedicated beamline.

Slides MOOA5 [2.605 MB]

MOOBI2

High Harmonics from Gas, a Suitable Source for Seeding FEL from the Vacuum-ultraviolet to Soft X-ray Region

FEL, laser, electron, radiation

9

G. Lambert, J. Gautier, V. Malka, A. Sardinha, S. Sebban, F. Tissandier, B. Vodungbo, P. Zeitoun
LOA, Palaiseau, France
B. Carré, D. Garzella
CEA/DSM/DRECAM/SPAM, Gif-sur-Yvette, France
O.V. Chubar, M.-E. Couprie, M. Labat
SOLEIL, Gif-sur-Yvette, France
M. Fajardo
IPFN, Lisbon, Portugal
T. Hara
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
C.P. Hauri
Paul Scherrer Institut, Villigen, Switzerland
H. Kitamura, T. Shintake
RIKEN/SPring-8, Hyogo, Japan
J. Lüning
CCPMR, Paris, France
Y.T. Tanaka
JASRI/SPring-8, Hyogo-ken, Japan
T. Tanikawa
PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France

FEL have been recently evolving very fast in the extreme-ultraviolet to soft X-ray region. Once seeded with high harmonics generated in gas, these light sources deliver amplified emissions with properties which are, for most of them, directly linked to the injected harmonic beam, e.g. the ultrashort pulse duration for FEL and the high temporal and spatial degree of coherence. Since the last two years the developments of techniques for improving the harmonic properties for seeding FEL lead to major results on tunability, intensity, repetition rate and polarization. Actually harmonics are nowadays used for numbers of applications, before limited to FEL facility. Also, FEL based on harmonic seeding can benefit from the natural synchronization between the FEL, the harmonic and the laser used for generation, which makes it a perfect candidate for pump-probe experiment with fs resolution.

Slides MOOBI2 [1.782 MB]

MOPB07

Soft X-ray Free-electron Laser with a 10-time Reduced Size

electron, FEL, bunching, laser

28

F.H. Chao, C.H. Chen, K.Y. Huang, Y.-C. Huang
NTHU, Hsinchu, Taiwan

We present a 30-m long soft x-ray FEL consisting of a 5-MeV photoinjector, a 150 MeV linac, a magnetic chicane compressor, and a 3-m long undulator. We propose to employ both the 3rd and the 4th harmonics of a Nd laser at 355 and 266 nm, respectively, to illuminate the cathode of the photoinjector. Owing to the beating of the two lasers, the emitted electron beam could be modulated at 282 THz. The electrons are further accelerated to 150 MeV and, after acceleration, compressed by 33 times in a magnetic chicane. The temporal compression of the electron macropulse increases the electron bunching frequency to 9.3 PHz, corresponding to a soft x-ray wavelength of 32.2 nm. We adopt a solenoid-derived staggered array undulator* with a 3 m length, 5 mm undulator period, and 1.2 mm gap. With a solenoid field of 10 kG, we estimate an undulator parameter of 0.4 and a corresponding radiation wavelength of 32.2 nm for a 150 MeV driving beam. With 3.3 kA peak current, 0.03% energy spread, 2 mm-mrad emittance, and 80-micron beam radius at the undulator entrance, the GENESIS code predicts 0.2 GW radiation power from the 3 m long undulator for an initial bunching factor of merely 10 ppm.
* Y.C. Huang, H.C. Wang, R.H. Pantell, and J. Feinstein, "A staggered-array wiggler for far infrared, free-electron laser operation," IEEE J. Quantum Electronics 30 (1994) 1289.

MOPB08

Studies for Polarization Control at LCLS

polarization, FEL, electron, simulation

31

E. Allaria, Y.T. Ding, P. Emma, Z. Huang, H.-D. Nuhn, M. Rowen, J.J. Welch, J. Wu
SLAC, Menlo Park, California, USA

In order to improve the capabilities of LCLS to meet more of the user requirements it has been proposed to implement a method to produce circularly polarized coherent radiation in the LCLS free electron laser. In this work we will present the results of a new set of studies and simulations that have been done for adding polarization control to LCLS using circularly polarizing undulators. Attention has been focused mainly on the use of variable gap APPLE-II undulators to be used at the end of a long SASE radiator that is based on the standard planar LCLS undulators. Issues like polarization contamination from the planar polarized light, polarization fluctuation and the choice of undulator configuration have been studied.

MOPB15

Numerical Simulation of CAEP Compact FEL THz Source

FEL, cavity, emittance, simulation

35

L.J. Chen, Q.K. Jia
USTC/NSRL, Hefei, Anhui, People's Republic of China
M. Li, X. Yang
CAEP/IAE, Mianyang, Sichuan, People's Republic of China

Free Election Laser Terahertz source is a good choice for THz source, whose wavelength is tunable. Using 1D FEL stimulation code FELO, we simulate the output characteristic of China Academy of Engineering Physics (CAEP) FEL THz, which is a waveguide FEL oscillator. The beam qualitys’ influence on the operation of FEL, such as energy dispersion, emittance and beam current, have been studied to designate a set of beam parameters. Besides, the output performance of FEL at different output coupling ratio is analyzed. The cavity detuning is discussed too. Meanwhile the influence of the position of the undulator in the cavity on the FEL performance is also studied.

MOPB16

New Tunable DUV Light Source for Seeding Free-electron Lasers

FEL, laser, simulation, electron

38

N.Y. Joly, W. Chang, P. Hölzer, J. Nold, P.St.J. Russell, J.C. Travers
Max Planck Institute for the Science of Light, Erlangen, Germany
M.-E. Couprie, M. Labat
SOLEIL, Gif-sur-Yvette, France

Seeding of single-pass free-electron lasers is a promising approach for improving the temporal coherence compared to self-amplified spontaneous emission [1], at the same time reducing the saturation length and reinforcing the harmonic level. Convention lasers or harmonics generated in gas are usually used as coherent seeds [1]. However such sources require complicated set-up and have limited tuneability. Here, we suggest the use of a newly discovered and efficient source of UV light, continuously tunable from 120 nm to 320 nm. The extremely compact and simple set-up consists of 20 cm of hollow-core photonic crystal fibre filled with a noble gas at variable pressure up to a few tens of bar and pumped by ~1 μJ 30 fs pulses at 800 nm [2]. The process relies on a favourable sequence of linear and nonlinear effects: low pressure-tunable dispersion, pulse compression due to a combination of self-phase-modulation and anomalous dispersion, self-steepening and dispersive wave generation. Tunable diffraction-limited DUV pulses of ~50 nJ and fs duration are generated. Seeding of FEL is discussed.
[1] G. Lambert et al., Nature Physics 4, 296-300 (2008)
[2] N. Joly et al., accepted in PRL

MOPB17

Harmonic Generation for a Hard X-ray FEL

electron, FEL, emittance, bunching

41

Q.R. Marksteiner, K. Bishofberger, B.E. Carlsten, L.D. Duffy, N.A. Yampolsky
LANL, Los Alamos, New Mexico, USA

Funding: We gratefully acknowledge the support of the US Department of Energy through the LANL LDRD Propgram for this work.
The proposed MaRIE XFEL at Los Alamos National Laboratory will generate ¼ Å, longitudinally coherent x-rays with a 20 GeV electron beam. A masked emittance exchanger can be used to generate coherent electron bunching at nm wavelengths. This masked emittance exchanger must be at 1 GeV in the accelerator, in order to mitigate debunching from incoherent synchrotron radiation (ISR). After this, the harmonic content must be stepped up by a factor of 200 in frequency and the electrons must be accelerated to 20 GeV. The nonlinear debunching effects in the accelerator from emittance must be mitigated by keeping the beam transversely large. There are several schemes to step the coherent bunching up to higher harmonics, all which require modulator and dispersive sections [1]. Echo-Enhanced Harmonic Generation, which requires large dispersion, must be incorporated at low energies, where ISR is reduced. Here we compare the usefulness of different harmonic generation schemes, and examine the possibility of placing successive harmonic generation sections at energies lower than 20 GeV in the accelerator line, with the accelerator sections in between used to introduce dispersion to the beam.
[1] Phys. Rev. E 71, 046501 (2005), etc.

MOPB19

Using Laser Harmonics to Increase Bunching Factor in EEHG

bunching, laser, FEL, factory

45

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

Funding: This work was supported by U.S. DOE Contracts No. DE-AC02-76SF00515 and DE-AC02-05CH11231
Echo-enabled harmonic generation (EEHG) is one of most promising approaches to seeding of soft x-ray FELs. It allows one to obtain beam bunching at high harmonics (of order of 100) of the laser frequency at a level of a few percent. In this paper we demonstrate that using the second and third harmonics of the laser radiation one can substantially increase the beam bunching: for a cold beam one can obtain values approaching 0.4 in the range of harmonic numbers 100~200. Such bunching factors are close to those achieved at saturation in the FEL process, which means that one can eliminate the lasing process and use coherent radiation of the pre-bunched beam in the undulator-radiator as a bright source of x-rays. We also discuss an option of using nonlinear dispersive elements to increase the bunching factor.

MOPB20

Effect of Coulomb Collisions on Echo-Enabled Harmonic Generation (EEHG)

bunching, FEL, scattering, emittance

49

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

Funding: Work supported by U.S. DOE Contract No. DE-AC02-76SF00515.
Echo-enabled harmonic generation (EEHG) for FEL seeding uses two undulator-modulators and two chicanes to introduce a fine structure into the beam longitudinal phase space which, at the end of the system, transforms into high harmonic modulation of the beam current. As a result of this phase space manipulation, after the first chicane, the energy distribution function becomes a rapidly modulated function of energy, with the scale of the modulation of the order of the initial energy spread of the beam divided by the EEHG harmonic number. Small-angle Coulomb collisions between the particles of the beam (also known as intrabeam scattering) tend to smear out this modulation and hence to suppress the beam bunching. In this paper we calculate the EEHG bunching factor with account of the collisions and derive a simple scaling relation for the strength of the effect. Our estimates show that collisions become a limiting factor in EEGH seeding for harmonic numbers roughly exceeding 100.

MOPB25

Improvement of the Crossed Undulator Design for Effective Circular Polarization

polarization, radiation, electron, controls

61

G. Geloni
European XFEL GmbH, Hamburg, Germany
V. Kocharyan, E. Saldin
DESY, Hamburg, Germany

The production of X-ray radiation with a high degree of circular polarization constitutes an important goal at XFEL facilities. A simple scheme to obtain circular polarization control with crossed undulators has been proposed so far. In its simplest configuration the crossed undulators consist of pair of short planar undulators in crossed position separated by an electromagnetic phase shifter. An advantage of this configuration is a fast helicity switching. A drawback is that a high degree of circular polarization (over 90%) can only be achieved for lengths of the insertion devices significantly shorter than the gain length, i.e. at output power significantly lower than the saturation power level. Here we propose to use a setup with two or more crossed undulators separated by phase shifters. This cascade crossed undulator scheme is distinguished, in performance, by a fast helicity switching, a high degree of circular polarization (over 95%) and a high output power level, comparable with the saturation power level in the baseline undulator at fundamental wavelength. We present feasibility study and exemplifications for the LCLS baseline in the soft X-ray regime.

MOPB26

Self-seeded Operation of the LCLS Hard X-ray FEL in the Long-bunch Mode of Operation

electron, wakefield, FEL, radiation

65

G. Geloni
European XFEL GmbH, Hamburg, Germany
V. Kocharyan, E. Saldin
DESY, Hamburg, Germany

Self-seeding options for the LCLS baseline were recently investigated using a scheme which relies on a single-crystal monochromator in Bragg-transmission geometry. The LCLS low-charge (0.02 nC) mode of operation was considered in order to demonstrate the feasibility of the proposed scheme. The wakefield effects from the linac and from the undulator vacuum chamber are much reduced at such low charge, and can be ignored. In this paper we extend our previous investigations to the case of the LCLS mode of operation with nominal charge. Based on the LCLS start-to-end simulation for an electron beam charge of 0.25 nC, and accounting for the wakefields from the undulator vacuum chamber we demonstrate that the same simplest self-seeding system (two undulators with a single-crystal monochromator in between) is appropriate not only for short (few femtosecond) bunches, but for longer bunches too.

MOPB27

Circular Polarization Control for the LCLS Baseline in the Soft X-ray Regime

radiation, electron, polarization, controls

69

G. Geloni
European XFEL GmbH, Hamburg, Germany
V. Kocharyan, E. Saldin
DESY, Hamburg, Germany

Several schemes have been discussed to obtain soft-polarization control in the context of the LCLS. We propose a novel method to generate 10 GW level power at the fundamental harmonic with 99% degree of circular polarization from the LCLS baseline. Its merits are low cost, simplicity and easy implementation. As in previously proposed methods, the microbunching of the planar undulator is used here as well. After the baseline undulator, the electron beam is sent through a 40 m long straight section, and subsequently through a short helical (APPLE II) radiator. The microbunching is easily preserved, and intense coherent radiation is emitted in the helical radiator. The background radiation from the baseline undulator can be suppressed by letting radiation and electrons through horizontal and vertical slits upstream the helical radiator, where the radiation spot size is about ten times larger than the electron bunch transverse size. Thin Be foils for the slits will preserve from electron losses. Other facilities e.g. LCLS II or the European XFEL may benefit from this work as well, due to availability of sufficiently long free space at the end of undulator tunnel.

MOPB29

Generation of Doublet Spectral Lines at Self-seeded X-ray FELs

radiation, electron, FEL, laser

77

G. Geloni
European XFEL GmbH, Hamburg, Germany
V. Kocharyan, E. Saldin
DESY, Hamburg, Germany

We propose to extend our recently proposed single-crystal monochromatization setup to the case when two or more crystals are arranged in a series to spectrally filter the SASE radiation at two or more closely-spaced wavelengths within the FEL gain band. This allows for the production of doublet or multiplet spectral lines. We present simulation results for the LCLS baseline operating at two closely spaced wavelengths. We show that we can produce fully coherent radiation shared between two longitudinal modes. Mode spacing can be easily tuned within the FEL gain band. The proposed scheme allows for a modulation of the electron bunch at optical frequencies without a seed quantum laser. In fact, the XFEL output intensity contains an oscillating "mode-beat" component whose frequency is related to the frequency difference between the pair of longitudinal modes considered. At saturation one obtains FEL-induced optical modulations of energy loss and energy spread in the electron bunch, which can be converted into density modulation with a weak chicane behind the baseline undulator. Powerful coherent radiation, synchronized with the X-ray pulses, can then be generated with an OTR station.

MOPB30

The Effects of Betatron Motion on the Preservation of FEL Microbunching

electron, betatron, bunching, emittance

81

G. Geloni
European XFEL GmbH, Hamburg, Germany
V. Kocharyan, E. Saldin
DESY, Hamburg, Germany

In some options for circular polarization control at X-ray FELs, a helical radiator is placed a few ten meters distance behind the baseline undulator. If the microbunch structure induced in the baseline (planar) undulator can be preserved, intense coherent radiation is emitted in the helical radiator. The effects of betatron motion on the preservation ofμbunching in such in-line schemes should be accounting for. In this paper we present a comprehensive study of these effects. It is shown that one can work out an analytical expression for the debunching of an electron beam moving in a FODO lattice, strictly valid in the asymptote for a FODO cell much shorter than the betatron function. Further on, numerical studies can be used to demonstrate that the validity of such analytical expression goes beyond the above-mentioned asymptote, and can be used in much more a general context. Finally, a comparison with Genesis simulations is given.

MOPB31

Self-seeding Scheme with Gas Monochromator for Narrow-Bandwidth Soft X-Ray

radiation, electron, FEL, resonance

85

G. Geloni
European XFEL GmbH, Hamburg, Germany
V. Kocharyan, E. Saldin
DESY, Hamburg, Germany

We propose an extension of our recently-proposed single-crystal self-seeding scheme to the soft X-ray range using a cell filled with resonantly absorbing gas as monochromator. The transmittance spectrum in the gas exhibits an absorbing resonance with narrow bandwidth. Then, similarly to the hard X-ray case, the temporal waveform of the transmitted radiation pulse is characterized by a long monochromatic wake, whose power is much larger than the equivalent shot noise power in the electron bunch. The monochromatic wake of the radiation pulse is combined with the delayed electron bunch and amplified in the second undulator. The proposed setup is extremely simple, and composed of as few as two simple elements: a gas cell, to be filled with noble gas, and a short magnetic chicane. The installation of the magnetic chicane does not perturb the undulator focusing system and does not interfere with the baseline mode of operation.

MOPB32

System Trade Analysis for an FEL Facility

FEL, photon, linac, emittance

89

M.W. Reinsch, B. Austin, J.N. Corlett, L.R. Doolittle, G. Penn, D. Prosnitz, J. Qiang, A. Sessler, M. Venturini, J.S. Wurtele
LBNL, Berkeley, California, USA

Designing an FEL from scratch requires the design team to balance multiple science needs, FEL and accelerator physics constraints and engineering limitations. STAFF (System Trade Analysis for an FEL Facility) enables the user to rapidly explore a large range of Linac and FEL design options. The model utilzes analytical models such as the Ming Xie formulas when appropriate and look-up tables when necessary to maintain speed, flexibility and extensiblity. STAFF allows for physics models for FEL harmonics, wake fields, cavity higher-order modes and aspects of linac particle dynamics. The code will permit the user to study error tolerances and multiple beamlines so as to explore the full capabilities of an entire user facility. This makes it possible to optimize the integrated system in terms of performance metrics such as photons/pulse, photons/sec and tunability range while ensuring that unrealistic requirements are not put on either the electron beam quality, undulator field/gap requirements or other system elements. This paper will describe preliminary results from STAFF as applied to a CW FEL soft X-ray facility.

MOPC02

Improvement of Termination Field of Bulk HTSC Staggered Array Undulator

electron, simulation, solenoid, controls

96

N. Kimura, M. A. Bakr, Y.W. Choi, H. Imon, K. Ishida, T. Kii, R. Kinjo, K. Komai, K. Masuda, H. Ohgaki, M. Omer, S. Shibata, K. Shimahashi, T. Sonobe, K. Yoshida
Kyoto University, Institute for Advanced Energy, Kyoto, Japan

We have proposed a bulk High Temperature Superconductor Staggered Array Undulator (Bulk HTSC SAU) to achieve higher undulator field, shorter period, and variable K-value without changing gap[1]. The purpose of this study is to revise the controversial point, that bulk HTSC SAU generates strong wicked magnetic field on its terminations, which scatters electron beam. Therefore we studied a new method to correct the field. We developed a physical model which based on Bean model to deal with the bulk superconducting material and then constructed a simulation code. By using the calculation results, we developed the correction method by adding bulk material on the edge of undulator. Measurement of the magnetic field of a prototype of bulk HTSC SAU with this method has been performed. We confirm that the numerical calculation well describe the experimental results. In this conference, numerical and experimental results of our end field termination method will be presented.
[1] R. Kinjyo, T. Kii, H. Zen, K Higashimura, K Masuda, K. Nagasaki, H. Ohgaki, Y.U. Jeong "Bulk High-TC Super Conductor Staggered Array Undulator" Proceedings of FEL2008

MOPC03

Modeling of the Quiet Start Algorithm in the Framework of the Correlation Function Theory

FEL, simulation, radiation, electron

99

O.A. Shevchenko, N. Vinokurov
BINP SB RAS, Novosibirsk, Russia

To suppress initial beam current fluctuations at the fundamental harmonic the macroparticle based FEL simulation codes use the quiet start algorithm. This algorithm should be valid at linear stage but there is no simple method to check whether it gives correct results at saturation. The regular approach to the start-up from noise problem should be based on the correlation function equation. In this paper we show that the quiet start algorithm can be naturally described in the framework of the correlation function theory. For this purpose one just needs to assume nonzero correlations in the initial particle distribution. This approach gives the possibility to compare simulation results for the system with reduced number of particles and artificially suppressed initial fluctuations with the case of real system with large number of particles.

MOPC05

HGHG Scheme for FLASH II

electron, simulation, FEL, radiation

107

A. Meseck, R. Mitzner
HZB, Berlin, Germany
W. Decking, B. Faatz, M. Scholz
DESY, Hamburg, Germany

FLASH II is a major extension of the existing FLASH facility at DESY. It has been proposed in collaboration with the HZB. FLASH II is a seeded FEL in the parameter range of FLASH. The final layout of the undulator section of FLASH II allows for different seeding schemes. So that seeding with an HHG source as well as seeding in cascaded HGHG scheme and several combination of these schemes are possible. However, for the shortest wavelengths down to 4 nm the cascaded HGHG scheme will be utilized. It consists of two frequency up conversion stages utilizing a Ti:Sa laser based seeding source in UVU range. We present and discuss start-to-end simulation studies for the shortest wavelength generated in the HGHG cascade of FLASH II.

MOPC06

X-Ray FELs Based on ERL Facilities

FEL, radiation, electron, emittance

111

A. Meseck
HZB, Berlin, Germany
G.H. Hoffstaetter, F. Löhl, C.E. Mayes
CLASSE, Ithaca, New York, USA

The characteristic high repetition rate and the high spectral brightness of the electron beams delivered by ERLs have led to a large number of ERL based proposals for hard X-ray sources including X-ray FELs. FEL oscillators, including those proposed for hard X-rays, require comparatively low peak currents and are particularly suitable for ERLs. However single-pass FELs in SASE or seeded mode do not seem out of reach when bunch-compression schemes for higher peak currents are utilized. Using the proposed Cornell ERL as an example, we present and discuss oscillator and single-pass FEL schemes which provide extremely high spectral-brightness ultra-short X-ray pulses for experiments.

MOPC09

Use of Re-Acceleration and Tapering in High Gain Free Electron Lasers to Enhance Power and Energy Extraction

FEL, electron, acceleration, extraction

115

R. Dusad, G. Travish
UCLA, Los Angeles, USA

In high gain Free Electron Lasers (FELs), it is possible to use undulator tapering to increase power and energy extraction beyond saturation. For some applications, however, tapering is not sufficient or results in excessively long structures. Here we the study use of tapered undulators interrupted by short accelerator sections to increase the power extracted per unit length. Re-acceleration restores nominal energy to the beam with minimal disruption to bunching, and allows repeated use of a single taper profile. We show that for suitable parameter sets this approach can perform better than ideal tapering alone, and may serve to greatly improve and simplify high peak and average power FELs. Based on these findings, we propose a first experiment to test the re-acceleration with tapering concept.

MOPC10

Numerical Investigation of Longitudinal Coherence in a Linear Tapered SASE FEL

radiation, FEL, electron, simulation

118

H.T. Li, Q.K. Jia
USTC/NSRL, Hefei, Anhui, People's Republic of China

One goal of the several FEL facilities operating in soft X-ray range, is the production of high-gain narrow-bandwidth FEL. In this report, the performance of radiation power and longitudinal cohence is studied for x-ray FEL generated through several different methods, including tapered，inverse-tapered and step-tapered undulator, and the SASE-FEL applying distributed optical klystron. Three–dimensional simulation demonstrate that these methods all can increase the FEL power and improve the time and spectrum structure with their own parameter optimization. In particular, FEL generated from toothed undulaor is studied. It is shown that the longitudinal cohence is improved and a series of several fettosecond pulses at gigawatt power levels at a wavelength of 1.5 nm is generated.

MOPC14

Infrared Single Spike Pulses Generation Using a Short Period Superconducting Tape Undulator at APEX

FEL, emittance, space-charge, electron

129

D. Filippetto, C. F. Papadopoulos, G. Penn, S. Prestemon, F. Sannibale
LBNL, Berkeley, California, USA
C. Pellegrini
UCLA, Los Angeles, California, USA
M. Yoon
POSTECH, Pohang, Kyungbuk, Republic of Korea

Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
We report on the possibility of constructing an infrared FEL by combining a novel design super-conducting undulator developed at LBNL with the high brightness beam from the APEX injector facility at the Lawrence Berkeley National Laboratory. Calculations show that the resulting FEL is expected to deliver a saturated power of about a MW within a 4 m undulator length when operating in Self-Amplified-Spontaneus-Emission mode, with a single-spike of coherent radiation at 2 μm wavelength. The sub-cm undulator periods, associated with the relatively low energy of the APEX beam (20-25 MeV), forces the FEL to operate in a regime with unusual and interesting characteristics. The alternative option of laser seeding the FEL is also examined, showing the potential to reduce the saturation length even further.

MOPC28

Fine Tuning of the K-parameter of Two Segments of the European XFEL Undulator Systems

radiation, electron, simulation, diagnostics

144

Y. Li, J. Pflüger
European XFEL GmbH, Hamburg, Germany
E. Gluskin
ANL, Argonne, USA
N. Vinokurov
BINP SB RAS, Novosibirsk, Russia

For large and segmented undulator systems as needed for the European XFEL a non-destructive, in situ, radiation diagnostics method would strongly compliment e-beam diagnostics. If such method would allow to fine tune the K parameter of individual undulator segments with an accuracy set by the Pierce parameter ρ, which is on the order of 2~3×10^-4, this would provide a very helpful tool for FEL commissioning. This paper provides a first analysis of a strategy of tuning the K parameter of two adjacent undulator segments. The spontaneous, monochromatized, on axis intensity is analyzed as a function of the phase delay set by the phase shifter in between. It makes use of diagnostic equipment which will be available at the European XFEL anyway. First results are demonstrated and limitations will be discussed.

TUOAI1

Hard X-ray Self-seeding for XFELs: Towards Coherent FEL Pulses

electron, radiation, FEL, wakefield

148

G. Geloni
European XFEL GmbH, Hamburg, Germany
V. Kocharyan, E. Saldin
DESY, Hamburg, Germany

Start-up from shot noise limits the longitudinal coherence of typical SASE XFEL pulses. Self-seeding schemes provide an elegant solution to this problem. However, their applicability to the baseline of already working or designed XFELs is subject to constraints, including minimal changes to the baseline design and possibility to recover the baseline mode of operation. Here we discuss a recently proposed single-bunch self-seeding scheme for hard X-rays. The physical principles of this scheme can be extended to soft X-rays as well. The method is based on a particular kind of monochromator, which relies on the use of a single crystal in Bragg-transmission geometry. In its simplest configuration, the setup consists of an input undulator and an output undulator separated by such monochromator. Several, more advanced configurations can be considered. For example, for high repetition rates of the X-ray pulses, or when a high spectral purity of the output radiation is requested, the simplest two-undulator configuration is not optimal: three or more undulators separated by monochromators can then be used. Exemplifications, based on facilities working or under construction will be discussed.

Slides TUOAI1 [2.818 MB]

TUOA4

Toward TW-level, Hard X-ray Pulses at LCLS

electron, FEL, radiation, simulation

160

W.M. Fawley, J.C. Frisch, Z. Huang, Y. Jiao, H.-D. Nuhn, C. Pellegrini, J. Wu
SLAC, Menlo Park, California, USA
S. Reiche
Paul Scherrer Institut, Villigen, Switzerland

Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515.
Coherent diffraction imaging of complex molecules, like proteins, requires a large number of hard X-ray photons, ~10⁺¹³/pulse, within a time ~10 fs or less. This is equivalent to a peak power of about one TW, much larger than that currently generated by LCLS or other proposed X-ray FELs. We study the feasibility of producing such pulses from LCLS and the proposed LCLS-II, employing a configuration beginning with a SASE amplifier, followed by a "self-seeding" crystal monochromator [1], and finishing with a long tapered undulator. Results suggest that TW-level output power at 8 keV is possible, with a total undulator length below 200 m. We use a 40 pC electron bunch charge, normalized transverse emittance of 0.2-mm-mrad, peak current of 4 kA, and electron energy about 14 GeV. We present a tapering strategy that extends the original "resonant particle" formalism by optimizing the transport lattice to maximize optical guiding and enhance net energy extraction. We also discuss the transverse and longitudinal coherence properties of the output radiation pulse. Fluctuation of such a tapered FEL is studied with realistic jitter measured at LCLS and with start-to-end simulation.

Slides TUOA4 [9.357 MB]

TUOBI2

First Lasing in the Water Window with 4.1nm at FLASH

FEL, radiation, electron, klystron

164

S. Schreiber
DESY, Hamburg, Germany

The free-electron laser facility FLASH at DESY, Germany has been upgraded. The electron beam energy has been increased from 1 to 1.25 GeV by adding a 7th superconducting accelerating module. In September 2010, for the first time, lasing in the water window at a fundamental wavelength of 4.1 nm has been achieved. The water window is a wavelength region between 2.3 and 4.4 nm in which water is transparent for light. This remarkable achievement opens the possibility for new class of experiments, especially for biological samples in aqueous solution.

Slides TUOBI2 [6.481 MB]

TUOBI3

Operational Experience at LCLS

linac, emittance, electron, FEL

166

H. Loos
SLAC, Menlo Park, California, USA

Funding: *Work supported by DOE contract DE-AC02-76SF00515
The Linac Coherent Light Source (LCLS) X-ray FEL has been operational since 2009 and is delivering soft and hard x-rays to users now in the 4th user run. Reliable operation to deliver x-rays to users, quick machine turn on after shutdowns, and fast configuration changes for the wide range of user requests are particularly important for a facility serving a single user at a time. This talk will discuss procedures to set-up and optimize the accelerator and FEL x-ray beam for user operation. The emphasis will be on the most relevant diagnostics and tuning elements as well as the experience with feedback systems and high level support software to automate FEL operation.

Slides TUOBI3 [3.074 MB]

TUOC4

Design and First Experience with the FERMI Seed Laser

laser, FEL, insertion, beam-transport

183

M.B. Danailov, P. Cinquegrana, A.A. Demidovich, R. Ivanov, I. Nikolov, P. Sigalotti
ELETTRA, Basovizza, Italy

Fermi@Elettra is the first fully seeding-based FEL. Laser operation was first demonstrated in December 2010 and later consistently studied during the runs in 2011. It is known that seeded operation puts heavy demands on the seed laser performance. This paper describes the design of the FERMI seed laser system, including the main laser as well as the most important subsystems and the issues that were solved to easily reach seeded operation. The main requirements to the seed were set by the use of High Gain Harmonic Generation FEL scheme and can be found in details in the FERMI CDR. Here we only recall that the seed needs to be broadly tunable in UV (down to 200 nm) with a peak power above 100 MW all over the tunability range. Obviously, such a tunability imposed the use of a parametric amplifier. For the first seeding comissioning, a fixed wavelength scheme was used, allowing much higher peak power. Here we present both solutions, showing the obtained performance and the limitations. The synchronization of the laser to the timing signals was of crucial importance for the successful seeded operation so the last part of the paper to the laser synchronization setup developed for FERMI.

Slides TUOC4 [1.360 MB]

TUPA04

sFLASH - Present Status and Commisioning Results

electron, laser, radiation, FEL

194

V. Miltchev, S. Ackermann, A. Azima, J. Bödewadt, F. Curbis, M. Drescher, E. Hass, Th. Maltezopoulos, M. Mittenzwey, J. Rönsch-Schulenburg, J. Roßbach, R. Tarkeshian
Uni HH, Hamburg, Germany
H. Delsim-Hashemi, K. Honkavaara, T. Laarmann, H. Schlarb, S. Schreiber, M. Tischer
DESY, Hamburg, Germany
R. Ischebeck
Paul Scherrer Institut, Villigen, Switzerland

The free-electron laser in Hamburg (FLASH) was previously being operated in the self-amplified spontaneous emission (SASE) mode, producing photons in the XUV wavelength range. Due to the start-up from noise the SASE-radiation consists of a number of uncorrelated modes, which results in a reduced coherence. One option to simultaneously improve both the coherence and the synchronisation between the FEL-pulse and an external laser is to operate FLASH as an amplifier of a seed produced using high harmonics generation (HHG). An experimental set-up - sFLASH, has been installed to test this concept for the wavelengths below 40 nm. The sFLASH installation took place during the planed FLASH shutdown in the winter of 2009/2010. The technical commissioning, which began in the spring of 2010, has been followed by FEL-characterization and seeded-FEL commissioning in 2011. In this contribution the present status and the sFLASH commissioning results will be discussed.

TUPA06

Seeding Schemes on the French FEL Project LUNEX5

laser, electron, simulation, FEL

198

C. Evain, F. Briquez, M.-E. Couprie, M. Labat, A. Loulergue
SOLEIL, Gif-sur-Yvette, France
V. Malka
LOA, Palaiseau, France

LUNEX5 is a single pass FEL project producing coherent synchrotron radiation with, in a first step, an electron bunch accelerated in conventional RF cavities up to 300 MeV. It is planned to work in a seeded configuration where the longitudinal coherence of the emitted light is improved and the gain length reduced, compared to the SASE configuration (Self-Amplified Spontaneous Emission). Two seeding schemes are considered: High order Harmonic in Gas seeding and EEHG scheme (Echo Enabled Harmonic Generation). Preliminary simulation results indicate that these two schemes permit to reach the saturation below a wavelength of 7 nm, and with less undulator periods for the EEHG scheme. Finally, the feasibility of plasma acceleration based FEL will also be investigated on this facility.

TUPA07

Study of a Silicon Based XFELO for the European XFEL

radiation, electron, cavity, simulation

202

J. Zemella, D. Novikov, M. Tolkiehn
DESY, Hamburg, Germany
J. Roßbach
Uni HH, Hamburg, Germany
H. Sinn
European XFEL GmbH, Hamburg, Germany

For the European XFEL in Hamburg three different SASE undulators are planed whose radiation output have a high peak brilliance up to 5.4·10³³ photon/s/mm²/mrad²/0.1% BW at wavelengths down to below 5·10^-11 m. The radiation pulses are nearly fully coherent in transverse direction but have a poor longitudinal coherence of about 0.3 fs. Several schemes were developed to get a better longitudinal coherence. In this paper an X-ray Free Electron Laser Oscillator is presented whose radiation output is nearly fully coherent in all directions. In contrast to previous schemes it is based on Silicon crystals rather than Diamond. The use of Silicon has the advantage of the availability of perfect crystals in nearly any size and crystal geometry but with a lower reflectivity and heat conduction than Diamond. To overcome the lower round-trip reflectivity of a Silicon cavity a longer undulator has to be used to get a sufficiently large gain. To reduce the heat load an extremely asymmetric crystal geometry has to be used to enlarge the beam spot on the crystal.

TUPA09

LUNEX5: A FEL Project Towards the Fifth Generation in France

laser, FEL, electron, linac

208

M.-E. Couprie, C. Benabderrahmane, F. Briquez, J. Daillant, J.-C. Denard, C. Evain, P. Eymard, F. Ferrari, J.-M. Filhol, M. Labat, A. Loulergue, P. Marchand, C. Miron, P. Morin, F. Polack
SOLEIL, Gif-sur-Yvette, France
S. Bielawski, C. Szwaj
PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
B. Carré
CEA/DSM/DRECAM/SPAM, Gif-sur-Yvette, France
N. Delerue, R. Roux, A. Variola
LAL, Orsay, France
G. Lambert, V. Malka, A. Rousse
LOA, Palaiseau, France
J. Lüning
CCPMR, Paris, France

LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation) aims at investigating the production of short intense and coherent pulses in the soft X rays region (down to 7 nm on the fifth harmonic). It comprises a free electron laser in the seeded configuration (High order Harmonic in Gas seeding and Echo Enable Harmonic Generation) using a conventional linear accelerator of 300 MeV. The FEL beamline including 15 m of in vacuum (potentially cryogenic undulators) of 15 and 30 mm period is designed so as to also accommodate a Laser Wake Field Accelerator (LWFA) ranging from 0.3 to 1 GeV, relying on electron beam parameters produced and accelerated by either the 60 TW laser of LOA or by the 10 PW APOLLON laser of ILE. After the completion and testing of the FEL with the conventional accelerator installed inside the SOLEIL booster inner area, the FEL line can be transported to a LWFA. A laser could alternatively be implemented at SOLEIL for starting testing the principles of a fifth generation light source.

TUPA13

Present Status and Future Prospects of Project on Utilizing Coherent Light Sources for User Experiments at UVSOR-II

laser, electron, FEL, storage-ring

215

H. Zen, K. Hayashi, S.I. Kimura, E. Nakamura, J. Yamazaki
UVSOR, Okazaki, Japan
M. Adachi, M. Katoh
Sokendai - Okazaki, Okazaki, Aichi, Japan
M. Hosaka, Y. Takashima, N. Yamamoto
Nagoya University, Nagoya, Japan
T. Takahashi
Kyoto University, Research Reactor Institute, Osaka, Japan

Funding: Quantum Beam Technology Program supported by JST/MEXT (Japan)
We have been intensively developing coherent light sources utilizing electron bunches in the storage ring, UVSOR-II, by adding some external components to the ring. After successful generation of coherent synchrotron radiation (CSR) in THz range* and coherent harmonic generation (CHG) in DUV range** by using an intense driving laser, a 5-year new research project named as Quantum Beam Technology Program has been started from FY2008. The project includes introduction of new driving laser system, dedicated undulators and beamlines, and aims at utilizing those coherent radiations for user experiments. The new driving laser system has been installed last year. The undulators and beamlines are now under construction. Installation of those components will be finished before the conference. In the conference, we will report on the present status of system development and future plan of application experiments.
*M. Shimada et al., Japanese Journal of Applied Physics, vol. 46, pp. 7939-7944 (2007).
**M. Labat et al., European Physical Journal D, vol. 44, pp. 187-200 (2007).

TUPA14

Conceptual Layout of a New Short-Pulse Radiation Source at DELTA Based on Echo-Enabled Harmonic Generation

laser, electron, lattice, dipole

219

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

As an upgrade of the present coherent harmonic generation (CHG) source at the DELTA storage ring, the installation of an additional undulator to implement and study the echo-enabled harmonic generation (EEHG) scheme [1] is planned. Compared to the CHG scheme, EEHG allows to produce radiation of shorter wavelengths, thus reaching more relevant absorption edges. In order to avoid dispersive distortions, all undulators should be placed along a straight line. This requires to increase the length of the present straight section by rearranging several magnets and vacuum components as well as a significant modification of the storage ring optics.
[1] G. Stupakov, PRL 102, 074801 (2009)

TUPA15

Status of the SwissFEL Facility at the Paul Scherrer Institute

FEL, linac, electron, emittance

223

S. Reiche
Paul Scherrer Institut, Villigen, Switzerland

SwissFEL is a X-ray Free-electron Laser facility with a soft and hard X-ray beamline, planned to be built at the Paul Scherrer Institute and to be finished in 2016. It covers the wavelength range from 1 Angstrom to 7 nm. In addition to the SASE operation at the entire wavelength, seeding is foreseen down to a wavelength of 1 nm. We report in this presentation the status of the SwissFEL facility, including the layout, the timeline of the project, the different operation modes and the expected performance of the FEL beamlines.

TUPA19

Operation Modes and Longitudinal Layout for the SwissFEL Hard X-Ray Facility

photon, linac, FEL, wakefield

235

B. Beutner, S. Reiche
Paul Scherrer Institut, Villigen, Switzerland

The SwissFEL facility will produce coherent, ultrabright, and ultra-short photon pulses covering a wavelength range from 0.1 nm to 7 nm, requiring an emittance between 0.18 to 0.43 mm mrad at bunch charges between 10pC and 200pC. In nominal operation continous changes between these two bunch charges will be offered to the users in order to allow them an individual tradeoff between photon power and pulse length depending on thier requirements. The facility consists of an S-band rf-gun and booster and a C-band main linac, which accelerates the beam up to 5.8 GeV. Two compression chicanes will provide a nominal peak current of about 1-3 kA depending on the charge. In addition special operation setups for ultra short single mode photon pulses and large bandwidth will be availiable to users. In this paper different operation modes including nominal operation as well as special modes are presented and discussed in terms of photon performance and machine stability requiremnts.

TUPA22

FLASH II: A Project Update

kicker, laser, electron, radiation

247

B. Faatz, V. Ayvazyan, N. Baboi, V. Balandin, W. Decking, S. Düsterer, H.-J. Eckoldt, M. Felber, J. Feldhaus, N. Golubeva, K. Honkavaara, M. Körfer, T. Laarmann, A. Leuschner, L. Lilje, T. Limberg, D. Nölle, F. Obier, A. Petrov, E. Plönjes, K. Rehlich, H. Schlarb, B. Schmidt, M. Schmitz, S. Schreiber, H. Schulte-Schrepping, J. Spengler, M. Staack, K.I. Tiedtke, M. Tischer, R. Treusch, M. Vogt, H.C. Weddig
DESY, Hamburg, Germany
J. Bahrdt, R. Follath, K. Holldack, A. Meseck, R. Mitzner
HZB, Berlin, Germany
J. Chen, H.X. Deng, B. Liu
SINAP, Shanghai, People's Republic of China
M. Drescher, A. Hage, V. Miltchev, R. Riedel, J. Rönsch-Schulenburg, J. Roßbach, M. Schulz, A. Willner
Uni HH, Hamburg, Germany
M. Gensch
HZDR, Dresden, Germany
F. Tavella
HIJ, Jena, Germany

FLASH II is an extension of the existing FLASH facility by an undulator line and an experimental Hall of which the construction will start before the end of the year. Aims are to increase beamtime for users and implement HHG seeding for the longer wavelength range from 10 to 40 nm at a reduced repetition rate of 100 kHz. Additional seeding schemes are under discussion as a future option. We will present a progress report of FLASH II.

TUPA26

Beam Commissioning of the SACLA Accelerator

FEL, electron, radiation, alignment

255

T. Hara, H. Tanaka, K. Togawa
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
T. Hasegawa, Y. Kano, T. Morinaga, Y. Tajiri, S. Tanaka, R. Yamamoto
SES, Hyogo-pref., Japan

The commissioning of the X-ray FEL facility of SPring-8, which is named SACLA (SPring-8 Angstrom Compact free-electron LAser), has been started since February 2011. During the beam commissioning, beam diagnostic system and control system are also tested and improved to enable fine tuning of the machine. The position and energy of the electron beam shows excellent stability and the fault rate of the RF system per hour is currently decreased to less than one. Since coherent OTR hinders the beam profile measurement after full bunch compression, several OTR screens are changed to YAG screens with a partial mask installed in its optics. So far the electron beam is successfully accelerated up to 8 GeV and spontaneous emission was observed with weak bunch compression. For the lasing, the RF parameters are first set so that a 0.1 nC bunch is compressed to 30 fs to obtain 3 kA beam current. Then the transverse beam profile is adjusted to match the focusing condition of the undulator section. In the conference, we will report the beam commissioning of the SACLA accelerator.

TUPA31

Transverse Phase-space Studies for the Electron Optics at the Direct XUV-seeding Experiment at FLASH (DESY)

electron, simulation, emittance, diagnostics

263

S. Ackermann, V. Miltchev, J. Roßbach
Uni HH, Hamburg, Germany

Funding: BMBF under contract No. 05 ES7GU1 - DFG GrK 1355 - Joachim Herz Stiftung
During the shutdown in 2009/2010 the Free-Electron Laser in Hamburg (FLASH) was upgraded with an experiment to study the high-gain-FEL amplification of a laser ‘‘seed'' from a high harmonic generation (HHG) source in the XUV wavelength range-sFLASH. For an optimal FEL-performance knowledge of the electron bunch transverse phase-space as well as control on the electron optics parameters is required. In this contribution the technical design, the present status and the commissioning results of the sFLASH diagnostic stations will be presented. The possible options for transverse phase space characterization will be discussed. An emphasis will be put on the error analysis and the tolerance estimations. Analysis of experimental data from both OTR-screens and wire scanners will be presented and discussed.

TUPB09

Free Electron Lasers in 2011

FEL, electron, laser, free-electron-laser

274

J. Blau, K. R. Cohn, W.B. Colson, C.M. Pogue, M. Stanton, A.I. Yilmaz
NPS, Monterey, California, USA

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

TUPB10

Echo Seeding Experiment at FLASH

laser, bunching, electron, FEL

279

K.E. Hacker, S. Khan
DELTA, Dortmund, Germany
G. Angelova Hamberg, V.G. Ziemann
Uppsala University, Uppsala, Sweden
A. Azima
Uni HH, Hamburg, Germany
P. Salén, P. van der Meulen
FYSIKUM, AlbaNova, Stockholm University, Stockholm, Sweden
H. Schlarb
DESY, Hamburg, Germany

Using the two perpendicularly oriented undulators and chicanes developed for an optical replica synthesizer (ORS) experiment together with the sFLASH 800 nm seed laser, radiator undulators and diagnostics, an echo seeding experiment will be conducted at FLASH in January 2012. For this experiment, the 800 nm laser pulse will be transported with a new, 12 meter long, in-vacuum laser transport line. On an in-vacuum optical breadboard, the 800 nm pulse will then be tripled in beta-BBO nonlinear crystals. The laser pulse will then be split longitudinally using a birefringent alpha BBO crystal into two pulses with orthogonal polarization states corresponding to the orthogonal orientations of the ORS undulators. These pulses will be focused to a 400 μm waist between the undulators with a Galileo telescope and steered with 4 motorized mirrors onto the electron beam axis in the ORS undulator section. The hardware layout and simulations of the echo seeding parameters will be described.

TUPB21

Conceptual Design of a High Brightness and Fully Coherent Free Electron Laser in VUV Regime

FEL, laser, electron, radiation

302

D. Wang, T. Zhang, Z.T. Zhao
SINAP, Shanghai, People's Republic of China
X.M. Yang
DICP, Dalian, People's Republic of China

In this paper we propose a new generation light source based on the High Gain Harmonic Generation (HGHG) Free Electron Laser (FEL) for scientific researches. This facility is designed to cover wavelength range from 50 nm to 150 nm with high brightness and full coherence by using the continuously tuning Optical Parametric Amplifier (OPA) seed laser system and variable gap undulators.

TUPB22

THz Pump and X-Ray Probe Development at LCLS

electron, FEL, laser, radiation

304

A.S. Fisher, H.A. Durr, J.C. Frisch, M. Fuchs, S. Ghimire, J.J. Goodfellow, A. Lindenberg, H. Loos, M. Petree, D.A. Reis
SLAC, Menlo Park, California, USA
D.R. Daranciang
Stanford University, Stanford, California, USA

Funding: This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under contract DE-AC02-76SF00515.
We report on measurements of broadband, intense, coherent transition radiation at terahertz frequencies, generated as the highly compressed electron bunches in LCLS pass through a thin metal foil. The foil is inserted at 45 degrees to the electron beam, 30 m downstream of the undulator. The THz emission passes downward through a diamond window to an optical table below the beamline. A fully compressed 350-pC bunch produces over 0.5 mJ in a nearly half-cycle pulse of 50 fs FWHM with a spectrum peaking at 10 THz. We estimate a peak field at the focus of over 2.5 GV/m. Electro-optic measurements using a newly installed 20-fs Ti:sapphire oscillator will be presented. We will discuss plans to add a THz pump and x-ray probe setup, in which a thin silicon crystal diffracts FEL light onto the table with adjustable time delay from the THz. This will provide a rapid start to user studies of materials excited by intense single-cycle pulses and will serve as a step toward a THz transport line for LCLS-II.

TUPB28

Considerations for a Light Source Test Facility at Daresbury Laboratory

electron, FEL, laser, emittance

308

N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
J.A. Clarke, D.J. Dunning, J.W. McKenzie
Cockcroft Institute, Warrington, Cheshire, United Kingdom

This paper considers design options for a dedicated light source test facility at Daresbury Laboratory in the United Kingdom. The facility layout should be easily configurable to enable exploration of many research themes including: ultrashort pulse generation; seeding and harmonic generation; direct laser/electron beam interactions; compact FELs; high brightness photoinjectors. The strategy is to develop and demonstrate novel concepts and expertise relevant to future generations of FEL-based light sources, significantly shortening the R&D phase of any future light source in the UK.

TUPB29

Status of the FERMI@Elettra Project

FEL, linac, photon, laser

312

M. Svandrlik, E. Allaria, E. Busetto, C. Callegari, D. Cocco, P. Craievich, I. Cudin, G. D'Auria, M.B. Danailov, S. Di Mitri, B. Diviacco, A. Fabris, R. Fabris, M. Ferianis, R. Gobessi, E. Karantzoulis, M. Kiskinova, M. Lonza, C. Masciovecchio, S. Noè, F. Parmigiani, G. Penco, M. Trovò, A. Vascotto, R. Visintini, M. Zaccaria, D. Zangrando, M. Zangrando
ELETTRA, Basovizza, Italy

FERMI@Elettra is a seeded FEL user-facility covering the wavelength range from 100 nm (12 eV) to 4 nm (310 eV) located next to the third-generation synchrotron light source Elettra in Trieste, Italy. The facility is based on a normal conducting linac and covers the wavelength range with two FEL lines, FEL-1 and FEL-2. A photon distribution and diagnostic system transports the photons from the end of the two FEL lines to three experimental stations. Beneficial occupancy of the new undulator hall and experimental hall was given end of Summer 2010 when also all auxiliary systems were made available. The installation of the machine is now almost completed; commissioning of the linac has started in parallel to the installation activities and now commissioning of FEL-1 is in a well advanced status. The first seeded lasing from FEL-1 was actually observed in December 2010 and first experiments are starting in 2011. In this paper an overview of the facility will be given as well as the general status of installation and commissioning and a perspective into future developments and user programs.

TUPB30

Status of the Fritz Haber Institute THz FEL

electron, FEL, cavity, linac

315

W. Schöllkopf, W. Erlebach, S. Gewinner, H. Junkes, A. Liedke, G. Meijer, W.Q. Zhang, G. von Helden
FHI, Berlin, Germany
H. Bluem, V. Christina, M.D. Cole, J. Ditta, D. Dowell, R. Lange, J.H. Park, J. Rathke, T. Schultheiss, A.M.M. Todd, L.M. Young
AES, Princeton, New Jersey, USA
S.C. Gottschalk
STI, Washington, USA
K. Jordan
Kevin Jordan PE, Newport News, Virginia, USA
U. Lehnert, P. Michel, W. Seidel, R. Wünsch
FZD, Dresden, Germany

The THz FEL at the Fritz Haber Institute (FHI) in Berlin is designed to deliver radiation from 4 to 400 microns. A single-plane-focusing undulator combined with a 5.4 m long cavity is used is the mid-IR (< 50 micron), while a two-plane-focusing undulator in combination with a 7.2 m long cavity with a 1-d waveguide for the optical mode is used for the far-IR. A key aspect of the accelerator performance is low longitudinal emittance, < 50 keV-psec, at 200 pC bunch charge and 50 MeV from a gridded thermionic electron source. We utilize twin accelerating structures separated by a chicane to deliver the required performance over the < 20 - 50 MeV energy range. The first structure operates at near fixed field while the second structure controls the output energy, which, under some conditions, requires running in a decelerating mode. "First Light" is targeted for the centennial of the FHI in October 2011 and we will describe progress in the commissioning of this device. Specifically, the measured performance of the accelerated electron beam will be compared to design simulations and the observed matching of the beam to the mid-IR wiggler will be described.

WEOA2

SASE FEL Pulse Duration Analysis from Spectral Correlation Function

electron, FEL, simulation, radiation

318

A.A. Lutman, Y.T. Ding, Y. Feng, Z. Huang, J. Krzywinski, M. Messerschmidt, J. Wu
SLAC, Menlo Park, California, USA

Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515.
A new method to measure the X-rays pulse duration through the analysis of the statistical properties of the SASE FEL spectra has been developed. The information on the pulse duration is contained in the correlation function of the intensity spectra measured after a spectrometer. The spectral correlation function is derived analytically for different profile shapes in the exponential growth regime and issues like spectral central frequency jitter and shot by shot statistical gain are addressed. Numerical simulations will show that the method is applicable also in saturation regime and that both pulse duration and spectrometer resolution can be recovered from the spectral correlation function. The method has been experimentally demonstrated at LCLS, measuring the soft X-rays pulse durations for different electron bunch lengths, and the evolution of the pulse durations for different undulator distances. Shorter pulse durations down to 13 fs FWHM have been measured using the slotted foil.

Slides WEOA2 [0.758 MB]

WEPA14

Effect of a Quasiperiodic Undulator on FEL Radiation

radiation, electron, FEL, free-electron-laser

352

F. Briquez, C. Benabderrahmane, M.-E. Couprie, C. Evain, M. Labat
SOLEIL, Gif-sur-Yvette, France

The operation of conventional undulators results from an interference scheme in order to generate radiation of a fundamental wavelength and its harmonics. Whereas these harmonics are in most of the cases useful to reach higher energies, it is profitable in specific configurations to shift or reduce them, for instance to limit power on optics or to distinguish between one or two photon process in user experiments. This can be performed by so-called quasi-periodic undulators in which the periodicity of the magnetic field is destructed. In this case, the field amplitude is reduced on a few positions among the axis, inducing a destruction of the interference scheme. Such undulators are commonly used to generate spontaneous emission in synchrotron radiation facilities but could also be installed in Free Electron Lasers. The emitted radiation of the quasi-periodic undulator is compared with the usual configuration one, in the case of LUNEX5. Simulations using GENESIS code are described and results are discussed.

WEPA22

Development of Insertion Devices Measurement System at IHEP

alignment, insertion, controls, insertion-device

381

W. Chen, X. Feng, H.H. Lu, C. Shi, Y. Yang, J.C. Zhang
IHEP, Beijing, People's Republic of China

In the cooperation between IHEP and EXFEL, prototype undulator U48 for EXFEL is developed by IHEP. In order to meet, maintain and verify the ID’s magnetic performance, a magnetic measurement system has been developed. The development status of the system at IHEP is described in this paper. A 6.5 m long measurement bench with hall probe and small coil is used to measure the vertical and horizontal components of the Insertion Device magnetic field. The measurement system includes a precise granite bench to position and move the magnetic sensors, motion control part and data acquisition part. The characteristics and performances of the magnetic measurement system are presented.

WEPA24

Error Analysis for Hybrid Undulators

insertion, insertion-device, free-electron-laser, laser

387

D. Arbelaez, A. Madur, S. Marks, S. Prestemon, D. Schlueter
LBNL, Berkeley, California, USA
H.-D. Nuhn
SLAC, Menlo Park, California, USA

Funding: This work was supported by the Director, Office of Science, of the US Department of Energy under Contract No. DE-AC02-05CH11231.
An analysis is performed on various possible errors that may occur throughout a hybrid undulator. Of particular significance is the scaling of the various errors with variations in the gap of the device. Tuning strategies are considered for the mitigation of these errors for the entire range of usable gap. Sorting strategies for the reduction of the initial errors in the undulator are also considered. Specifically, the effectiveness of the sorting algorithm is evaluated with respect to the number of permanent magnet blocks used per pole as well as the size and distribution of the block population. The results of this analysis are applied to the LCLS-II undulators to determine the required machining and positioning tolerances and viable tuning strategies in order to meet the design requirements.

WEPB02

Study of Highly Isochronous Beamlines for FEL Seeding

bunching, FEL, quadrupole, laser

391

C. Sun, H. Nishimura, G. Penn, M.W. Reinsch, D. Robin, F. Sannibale, C. Steier, W. Wan
LBNL, Berkeley, California, USA

Recently seeding schemes, such as ECHO for short (nm) wavelength FELs, have been proposed. These schemes require that the nm level longitudinal bunch structure be preserved over distance of several meters. This poses a challenge for the beamline design. In this paper we present our studies of several solutions for beamlines that are nearly isochronous.

WEPB03

LCLS-II Undulator Tolerance Analysis

FEL, simulation, electron, radiation

394

H.-D. Nuhn, J. Wu
SLAC, Menlo Park, California, USA
S. Marks
LBNL, Berkeley, California, USA

Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515
The SLAC National Accelerator Laboratory is constructing the new FEL user facility LCLS-II, as a major upgrade to the Linear Coherent Light Source (LCLS). The upgrade will include two new Free Electron Lasers, to generate soft (SXR) and hard X-ray (HXR) SASE FEL radiation, based on planar, variable gap hybrid undulators with two different undulator periods (SXR 55 mm, HXR 32 mm). An systematic FEL tolerance analysis for the undulator lines, including tuning, alignment, yaw deformation, and phase correction tolerances has been performed. The methods and results are presented in this work.

WEPB04

Position Stability Monitoring of the LCLS Undulator Quadrupoles

quadrupole, controls, ground-motion, monitoring

398

H.-D. Nuhn, G.L. Gassner, F. Peters
SLAC, Menlo Park, California, USA

Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515
In the era of SASE FELs, the demand for position stability of undulator components scales down to the range of sub-micrometers per day. Simultaneously, the undulator length increases significantly, in order to reach X-ray wavelengths. To minimize the impact of the outside environment, the LCLS undulator is placed underground, but reliable data about ground motion inside such a tunnel were not available in the required stability range. Therefore, a new position monitor system has been developed and installed for the LCLS undulator. That system is capable to measure X-, Y- and Roll positions of each of the 33 undulator quadrupoles, with respect to stretched wires. Instrument resolution is about 20 nm and instrument drift is negligible small. Position data of individual quadrupoles can be correlated along the entire undulator, which has a length of 132 m. The system is under continuous operation since 2009. The report describes long term experience with the running system and the observed position stability of the undulator quadrupoles.

WEPB14

Ultra-short Electron Bunch and X-ray Temporal Diagnostics with an X-band Transverse Deflector

FEL, electron, radiation, diagnostics

405

C. Behrens
DESY, Hamburg, Germany
Y.T. Ding, P. Emma, J.C. Frisch, Z. Huang, P. Krejcik, H. Loos, M.-H. Wang
SLAC, Menlo Park, California, USA

The measurement of ultra-short electron bunches on the femtosecond time scale constitutes a very challenging problem. In X-ray free-electron laser facilities such as the Linac Coherent Light Source (LCLS), generation of sub-ten femtosecond X-ray pulses is possible, and some efforts have been put into both ultra-short electron and X-ray beam diagnostics. Here we propose a single-shot method using a transverse deflector (X-band) after the undulator to reconstruct both the electron bunch and X-ray temporal profiles. Simulation studies show that about 1 fs (rms) time resolution may be achievable in the LCLS and is applicable to a wide range of FEL wavelengths and pulse lengths. The jitter, resolution and other related issues will be discussed.

WEPB16

Study for Evaluation of Undulator Magnetic Field Using Vibrating Wire Method

electron, resonance, radiation, damping

413

Y. Tanaka
Tohoku University, School of Science, Sendai, Japan
H. Hama, F. Hinode, S. Kashiwagi, M. Kawai, X. Li, T. Muto, K. Nanbu
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan

A test accelerator for a terahertz source project (t-ACTS) has been progressed at the Electron Light Science Centre, Tohoku University, in which a generation of intense coherent terahertz radiation from the very short electron bunch will be demonstrated. A narrow-band coherent terahertz radiation using an undulator has been considered to be implemented. We have constructed a planer undulator that is basically a Halbach type composed of permanent magnet blocks. The period length of the undulator and the number of periods are 100 mm and 25, respectively. The vibrating wire method is studied to measure the periodic magnetic field of the undulator. A thin copper-beryllium wire is placed on beam axis in the undulator, and an AC current flow is applied in the wire. By measuring amplitudes and phases of standing waves excited on the wire by the Lorentz force between AC current and magnetic field, we can reconstruct the magnetic field distribution along the wire. We discuss relations between reproducibility of the undulator field and the mode harmonics number used for the reconstruction. The results of preliminary measurement using the vibrating wire will be shown in this conference.

WEPB17

Evaluation of Lasing Range with a 1.8 m Undulator in KU-FEL

FEL, electron, cavity, gun

417

K. Ishida, M. A. Bakr, Y.W. Choi, H. Imon, T. Kii, N. Kimura, R. Kinjo, K. Komai, K. Masuda, H. Ohgaki, M. Omer, S. Shibata, K. Shimahashi, T. Sonobe, K. Yoshida, H. Zen
Kyoto University, Institute for Advanced Energy, Kyoto, Japan

In KU-FEL (Kyoto University FEL) 12-14 μm FEL has been available by using a 40 MeV S-bend linac and 1.6 m undulator. We are going to install 1.8 m undulator which was used in JAEA to extend the lasing range of KU-FEL. Numerical evaluation of the lasing range has been carried out by using GENESIS1.3. However, this work used an ideal undulator field data which was measured by JAEA in several years before. Therefore we re-measured the undulator field for different gaps. Then we evaluated the FEL gain and possible lasing range with 1.8 m undulator using measured undulator field. The undulator field measurement, FEL gain calculations and evaluation of lasing range in KU-FEL will be presented in the conference.

WEPB18

Development of the First U48 Undulator Prototype for the European X-ray Free Electron Laser

controls, alignment, FEL, laser

420

H.H. Lu, W. Chen, X. Feng, X.M. Jiang, C. Shi, S.C. Sun, M.T. Wang, Z.X. Wang, Y.F. Yang
IHEP, Beijing, People's Republic of China
Y. Li, J. Pflüger
European XFEL GmbH, Hamburg, Germany

Funding: MOST973 Program
The European XFEL will be a user facility consisting of three beamlines named SASE1/2/3 at the first stage. The first undulator prototype U48 for the European XFEL SASE2 beamline has been developed and tested by IHEP, China. Its magnetic design and specifications are briefly given. Development of U48, including magnetic material, mechanical structure, control system and assembly, are introduced. Magnetic tuning and test results are presented and discussed.

WEPB19

Enhancement of Undulator Field in Bulk HTSC Staggered Array Undulator with Hybrid Configuration

solenoid, synchrotron, radiation, ion

424

R. Kinjo, M. A. Bakr, Y.W. Choi, H. Imon, K. Ishida, T. Kii, N. Kimura, K. Komai, K. Masuda, K. Nagasaki, H. Ohgaki, M. Omer, S. Shibata, K. Shimahashi, T. Sonobe, K. Yoshida, H. Zen
Kyoto University, Institute for Advanced Energy, Kyoto, Japan

Funding: This work was supported by the Grant-in-Aid for Scientific Research B and JSPS Fellows by the Ministry of Education, Culture, Sports, Science and Technology of Japan
The purpose of this study is enhancement of the undulator field and it's stability in bulk high temperature superconductor staggered array undulator by introducing hybrid configuration. The authors made the magnetic field calculations with some hybrid configurations consists of bulk HTSCs, ferromagnetic pieces and permanent magnets. We also made prototype measurements. The results shows the hybrid configuration can generates stronger and more uniform magnetic field than bulk-HTSCs-only configuration. In this conference, numerical and experimental results of the hybrid configuration will be presented.

THOAI1

Pushing the Limits of Short Period Permanent Magnet Undulators

vacuum, permanent-magnet, cryogenics, FEL

435

J. Bahrdt
HZB, Berlin, Germany

Short period undulators to be used as FEL radiators permit lower electron energies and, thus, reduce linac and undulator lengths. The first X-ray FEL facility based on in-vacuum undulators goes into operation soon (SPRING-8 XFEL). Other in-vacuum undulator based FELs are under construction (SWISS-FEL) or are planned. The in-vacuum undulators have period lengths between 18mm (SPRING-8-X-FEL) and 15mm (SWISS-FEL). In the future the period length will be pushed further into the sub-cm regime. The technical implications of these devices will be discussed: New materials such as PrFeB-magnets are employed. They show their superior characteristics at cryogenic temperatures. Geometric and magnetic tolerances will be tighter and the construction and shimming concepts have to be revised. New magnetic measurement systems are required as well. Recently, a 9mm period length 20 period prototype undulator has been built in collaboration between Ludwig-Maximilian-University Munich and Helmholtz-Zentrum Berlin. The potential and the challenges of sub-cm undulators will be illustrated based on first results from this prototype.

Slides THOAI1 [3.344 MB]

THOA4

Three Bunch Compressor Scheme for SASE FEL

linac, emittance, FEL, electron

447

H.-S. Kang, I.S. Ko, S.H. Nam
PAL, Pohang, Kyungbuk, Republic of Korea
M.-H. Cho, C.H. Yi
POSTECH, Pohang, Kyungbuk, Republic of Korea

The bend angle of dipoles in bunch compressor needs to be small enough to reduce the emittance increase due to CSR, which requires a larger energy chirp at the preceding RF linac. Correlated energy spread is not reduced below FEL parameter after the following RF linac because of the small number of accelerating sections as in the PAL XFEL design. Three bunch compressor scheme can make it possible to minimize the CSR induced emittnace growth as well as reduce the correlated energy spread below FEL parameter.

Slides THOA4 [1.467 MB]

THOB3

First Demonstration of a Slippage-dominant Superradiant Free-electron Laser Amplifier

FEL, electron, laser, simulation

455

X. Yang, Y. Hidaka, B. Podobedov, S. Seletskiy, Y. Shen, X.J. Wang
BNL, Upton, Long Island, New York, USA

We report the first experimental demonstration of a slippage-dominant superradiant free-electron laser (FEL) using an ultrafast seed-laser pulse. We measured the evolution of the longitudinal phase space in the slippage-dominant superradiant regime, and also the output spectrum and pulse energy versus the electron beam energy. With a ±1% variation in the electron beam energy, we observed a seed-like fully longitudinal coherence, and ±2% spectral tuning range. The temporal and spectral evolution of the slippage-dominant FEL radiation as predicted by a numerical simulation was experimentally verified for the first time.

Slides THOB3 [0.374 MB]

THOB4

Transverse Coherence and Polarization Measurement of Coherent Femtosecond Pulses from a Seeded FEL

polarization, FEL, laser, electron

458

J. Schwenke, N. Čutić, F. Lindau, S. Werin
MAX-lab, Lund, Sweden
E. Mansten
Lund University, Division of Atomic Physics, Lund, Sweden

We report on measurements of the transverse coherence and polarization of light pulses at 131 nm generated by a seeded free-electron laser. Our setup consists of two undulators. The first undulator is used to energy modulate relativistic electron bunches (375 MeV) with the help of an ultraviolet seed laser pulse at 263 nm. The electron bunches subsequently pass through a dispersive section, where the energy modulation is converted into microbunching, and then enter the radiator undulator. The radiator is an APPLE-II type undulator set to be in resonance for 131 nm radiation. The radiator emits coherent femtosecond pulses up to the 6th harmonic of the seed laser [1]. The state of polarization of the pulses can be tuned from planar to helical polarization by shifting the undulator magnets. The emitted pulses are analyzed with a grating spectrometer. A double slit aperture is positioned in the beam in order to determine the transverse coherence of the light pulses by analyzing the fringe visibility. Furthermore, the generation of circular polarized light is demonstrated. The polarization state of the light pulses is measured with a Rochon prism polarizer.
[1] Cutic et al, Phys. Rev. Spec. Top-AC 14, 030706 (2011)

Slides THOB4 [1.173 MB]

THOB5

FEL Spectral Measurements at LCLS

FEL, electron, photon, laser

461

J.J. Welch, F.-J. Decker, Y.T. Ding, P. Emma, A.S. Fisher, J.C. Frisch, Z. Huang, R.H. Iverson, H. Loos, M. Messerschmidt, H.-D. Nuhn, D.F. Ratner, J.L. Turner, J. Wu
SLAC, Menlo Park, California, USA

Funding: Work supported in part by the DOE Contract DE-AC02-76SF00515.
Control and knowledge of the spectrum of FEL X-ray radiation at the LCLS is important to the quality and interpretation of experimental results. Narrow bandwidth is useful in experiments requiring high-brightness beams. Wide bandwidth is particularly useful for photon energy calibration using absorption spectra. Since LCLS was commissioned in 2009 measurements have been made of average and single shot spectra of X-ray FEL radiation at the LCLS over a range of 800 to 8000 eV, for fundamental and harmonic radiation. These include correlations with chirp, bunch current, undulator K-taper, electron beam energy, and charge as well as some specialized machine configurations. In this paper we present results and discuss the relationship of the electron beam energy distribution to the observed X-ray spectrum.

Slides THOB5 [0.442 MB]

THOC4

Transverse Size and Distribution of FEL X-ray Radiation of the LCLS

simulation, electron, FEL, background

465

J.L. Turner, F.-J. Decker, Y.T. Ding, P. Emma, J.C. Frisch, K. Horovitz, Z. Huang, R.H. Iverson, J. Krzywinski, H. Loos, M. Messerschmidt, S.P. Moeller, H.-D. Nuhn, D.F. Ratner, J.J. Welch, J. Wu
SLAC, Menlo Park, California, USA

Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515
Understanding and controlling the transverse size and distribution of FEL X-ray radiation of the LCLS at the SLAC National Accelerator Laboratory is discussed. Understanding divergence, source size, and distributions under various conditions is a convolution of many effects such as the electron distribution, the undulator alignment, micro-bunching suppression, and beta-match. Measurements of transverse size along the X-ray pulse and other studies designed to sort out the dominant effects are presented and discussed.

Slides THOC4 [1.874 MB]

THPA24

Development of Pr₂Fe₁₄B Cryogenic Undulator CPMU at SOLEIL

cryogenics, vacuum, permanent-magnet, electron

523

C. Benabderrahmane, P. Berteaud, N. Béchu, L. Chapuis, M.-E. Couprie, J.P. Daguerre, J.-M. Filhol, C. Herbeaux, A. Lestrade, M. Louvet, J.L. Marlats, K. Tavakoli, M. Valléau, D. Zerbib
SOLEIL, Gif-sur-Yvette, France

Short period, high field undulators can enable short wavelength FEL at low beam energy, with decreased gain length, thus allowing much more compact and less costly FEL systems. A R&D programme for the construction of a 2 m long 18 mm period CPMU is under progress at SOLEIL. The use of PrFeB which features a 1.35 T remanence (Br) at room temperature enables to increase the peak magnetic field at 5.5 mm minimum gap, from 1.04 T at room temperature to 1.15 T at a cryogenic temperature of 77 K. For FELs, we can reach higher magnetic field of 1.91 T at lower gap of 3 mm. Pr was chosen instead of Nd magnetic material, because of the no appearance of the SRT phenomenon. Different corrections were performed first at room temperature to adjust the phase error, the electron trajectory and to reduce the multipolar components. The mounting inside the vacuum chamber enables the fitting of a dedicated magnetic measurement bench to check the magnetic performance of the undulator at low temperature. The results of the magnetic measurements at low temperature and the comparison with the measurement at room temperature are reported. A U18 CPMU will be used in LUNEX5 project at SOLEIL.

THPA25

Standard Electron Beam Diagnostics for the European XFEL

electron, cavity, diagnostics, dipole

527

D. Lipka
DESY, Hamburg, Germany

The European XFEL under construction in Hamburg needs to control the electron beam parameters for reliable machine and FEL operation. Due to the flexible bunch pattern, a minimum bunch spacing of 222 ns and large beam charge range a high dynamic range of the monitors is necessary. Furthermore the high average beam power enforces an elaborated machine protection system. This paper presents an overview of the planned standard electron beam diagnostics. The status of the main systems is presented, as well as the results from prototype tests with beam at FLASH.

THPA29

Performance of the RF Cavity BPM at XFEL/SPring-8 “SACLA”

cavity, electron, factory, low-level-rf

539

H. Maesaka, T. Ohshima, Y. Otake
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
H. Ego, S. Matsubara
JASRI/SPring-8, Hyogo-ken, Japan
S.I. Inoue
SES, Hyogo-pref., Japan
T. Shintake
RIKEN Spring-8 Harima, Hyogo, Japan

We have developed an rf cavity beam position monitor (RF-BPM) for the XFEL facility at SPring-8, “SACLA”. The demanded position resolution of the BPM is less than 1 μm, because an electron beam and X-rays must be overlapped with 4 μm precision in the undulator section. To achieve this requirement, we employed a C-band RF-BPM that has a resonant frequency of 4760 MHz. The RF-BPM has a TM110 dipole mode resonator for position detection and a TM010 monopole mode resonator for phase reference and charge normalization. Rf signals from the RF-BPM are detected by IQ (In-phase and Quadrature) demodulators and the detected signals are recorded by 238 MHz waveform digitizers. The position resolution was confirmed to be 0.2 μm by using a 250 MeV electron beam at the SCSS test accelerator. Then, 57 RF-BPMs were produced and installed into SACLA. The beam tuning of SACLA started in February 2011 and the RF-BPM system has been working well. We report the basic performance such as a resonant frequency, a Q factor, machining accuracy etc. for each cavity and the achieved position resolution of the RF-BPM system.

THPB31

Multiple FELs from the One LCLS Undulator

FEL, electron, quadrupole, linac

629

F.-J. Decker, P. Emma, J.C. Frisch, K. Horovitz, Z. Huang, R.H. Iverson, J. Krzywinski, H. Loos, S.P. Moeller, H.-D. Nuhn, J.L. Turner, J.J. Welch, J. Wu
SLAC, Menlo Park, California, USA

Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Science, under Contract DE-AC02-76SF00515.
The FEL of the Linac Coherent Light Source (LCLS) at SLAC is generated in a 132 m long undulator. By introducing a kink in the undulator setup and launching different electron pulses with a small kick, we achieved two FEL beams with a separation of about 10 σ. These beams were separated at down stream mirrors and brought to the entrances of the soft and hard X-ray hutches. This was done at low energy creating soft X-rays which require only a shorter length to get to saturation. At high energy the whole undulator has to be "re-pointed" pulse by pulse. This can be done using 33 undulator correctors creating two straight lines for the photons with small angle to point the FEL to different mirrors pulse by pulse even at high energy. Experiments will be presented and further ideas discussed to get different energy photons created and sent to the soft and hard X-ray mirrors and experiments.