FEL2011 - List of Keywords (laser)

Paper	Title	Other Keywords	Page
MOOA5	Coherent Harmonic Generation at the DELTA Storage Ring	electron, radiation, undulator, 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, electron, radiation, undulator	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]

MOPA02	Development of a Microscopic Irradiation Technique for Delivering VIS-FELs to Single Cells through a Fine-tapered Glass Rod	FEL, electron, controls, free-electron-laser	16
	F. Shishikura Nihon University School of Medicine, Tokyo, Japan K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Tanaka LEBRA, Funabashi, Japan
	The first lasing of LEBRA* succeeded in 2001 to produce near infrared FELs, by which the higher harmonics generated by means of the non-linear optical crystals now covered with visible and near infrared regions from 0.35 to 6 microns. The VIS-FELs are of particular interest and are expected to reveal photochemical reactions of single cells, even those in living organisms. To do this, it is a prerequisite to develop a micro-irradiation technique for targeting a single cell without photochemical effect to neighboring cells. We have established a microscopic irradiation technique with VIS-FELs through a fine glass rod. The FEL delivered through a fine-tapered glass rod with a diameter of about 5 microns has two major advantages compared with conventional microscope irradiation systems. The first is to deliver the FEL directly into targeted single cells in accordance with standard microinjection techniques used in developmental biology. The second is the ability to irradiate specific areas of the cytoplasm including cell organelle without severely damaging targeted cells. Using this technique, we also report micro-irradiation experiments on targeted single cells in living organisms. *Laboratory for Electron Beam Research and Application, Nihon University

MOPB05	Smith-Purcell Radiation with Negative-index Material	radiation, electron, free-electron-laser, feedback	20
	D. Li, K. Imasaki ILT, Suita, Osaka, Japan M.R. Asakawa Kansai University, Osaka, Japan M. Hangyo, K. Takano ILE Osaka, Suita, Japan S. Miyamoto LASTI, Hyogo, Japan Y. Tsunawaki OSU, Daito, Osaka, Japan Z. Yang UESTC, Chengdu, Sichuan, People's Republic of China
	Smith-Purcell radiation from an electric line charge that moves, at constant speed, parallel to a grating made of metamaterial with negative index is analyzed. Through theoretical analysis and computations, we show that the Smith-Purcell radiation is stronger from a grating of negative-index material, than positive-index material and perfect conductor. Also, we found the radiation strongly depends on the values of permeability and permittivity.

MOPB06	Smith-Purcell Free Electron Laser with Bragg Reflector	electron, free-electron-laser, simulation, radiation	24
	D. Li, K. Imasaki ILT, Suita, Osaka, Japan M.R. Asakawa Kansai University, Osaka, Japan M. Hangyo ILE Osaka, Suita, Japan S. Miyamoto LASTI, Hyogo, Japan Y. Tsunawaki OSU, Daito, Osaka, Japan Z. Yang UESTC, Chengdu, Sichuan, People's Republic of China
	Grating with Bragg reflectors for the Smith-Purcell free-electron laser is proposed to improve the reflection coefficient, resulting in enhancing the interaction of the surface wave with the electron beam and, consequently, relax the requirements to the electron beam. With the help of particle-in-cell simulations, it has been shown that, the usage of Bragg reflectors may improve the growth rate, shorten the time for the device to reach saturation and lower the start current for the operation of a Smith-Purcell free-electron laser.

MOPB07	Soft X-ray Free-electron Laser with a 10-time Reduced Size	electron, undulator, FEL, bunching	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.

MOPB16	New Tunable DUV Light Source for Seeding Free-electron Lasers	FEL, simulation, electron, undulator	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

MOPB19	Using Laser Harmonics to Increase Bunching Factor in EEHG	bunching, undulator, 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.

MOPB21	Seeded Radiation Sources with Sawtooth Waveforms	bunching, FEL, radiation, damping	53
	D.F. Ratner Stanford University, Stanford, California, USA A. Chao SLAC, Menlo Park, California, USA
	Despite the recent success of SASE-based FELs, there is still considerable interest in driving coherent radiation sources with external seeding. Seeding schemes, such as HGHG and EEHG, can increase longitudinal coherence, decrease saturation lengths, and improve performance of tapering, polarization control and other FEL features. Typically, seeding schemes start with a simple sinusoidal modulation, which is manipulated to provide bunching at a high harmonic of the original wavelength. In this paper, we consider variations starting with a sawtooth modulation. The sawtooth creates a clean phase space structure, providing a maximal bunching factor without the need for an FEL interaction. While a pure sawtooth modulation is a theoretical construct, it is possible to approach the waveform by combining two or more of the composite wavelengths. We give examples of sawtooth seeding for HGHG, EEHG and other schemes including compressed seeding, steady state microbunching, and reversible seeding. Finally, we note that the sawtooth modulation may aid in suppression of the microbunching instability.

MOPB23	Reversible Seeding in Storage Rings	storage-ring, bunching, radiation, simulation	57
	D.F. Ratner Stanford University, Stanford, California, USA A. Chao SLAC, Menlo Park, California, USA
	We propose to generate steady-state microbunching in a storage ring by implementing a reversible seeding scheme. High gain harmonic generation (HGHG) and echo-enhanced harmonic generation (EEHG) are two promising methods for microbunching linac electron beams. Because both schemes increase the energy spread of the seeded beam, they cannot drive a coherent radiator turn-by-turn in a storage ring. However, reversing the seeding process following the radiator minimizes the impact on the electron beam and may allow coherent radiation at or near the storage ring repetition rate. In this paper we describe the general idea and outline a proof-of-principle experiment.

MOPB29	Generation of Doublet Spectral Lines at Self-seeded X-ray FELs	radiation, electron, undulator, FEL	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.

MOPC01	Compact THz Radiation Source Based on a Photocathode RF Gun	wiggler, electron, gun, FEL	92
	S. Liu Shanghai Jiao Tong University, Shanghai, People's Republic of China J. Urakawa KEK, Ibaraki, Japan
	Terahertz (THz) science and technology have already become the research highlight at present. In this paper, we put forward a proposal to generate THz radiation at tens of MW peak power. Due to the ultrafast laser and the high accelerating field of photocathode RF gun, we can generate and accelerate electron beam to several MeV, of which the bunch length is less than sub-ps. When the short electron bunches are injected into the wiggler, THz radiation based on Coherent Synchrotron Radiation could be achieved with tens of MW peak power. The whole THz FEL facility can be scaled to the size of a tabletop.

MOPC04	The Effects of Jitters on Coherent X-ray Radiation Using a Modulation Compression Scheme	radiation, electron, FEL, resonance	103
	J. Qiang LBNL, Berkeley, California, USA J. Wu SLAC, Menlo Park, California, USA
	Modulation compression scheme based on a chirped beam, laser modulator and laser chirper, and two bunch compressors was proposed recently to generate coherent multi-color atto-second X-ray radiation [1]. In this paper, we will present studies of effects of the initial longitudinal beam chirp jitter, time synchronization jitter between the electron beam and the laser chirper, and the laser chirper amplitude jitter on the final coherent X-ray radiation. [1]Ji Qiang and Juhao Wu, “Generation multi-color attosecond X-ray radiation through modulation compression,” arXiv:1102.4806v1.

MOPC21	Comparison of Growth Rates of Two-Stream Free Electron Lasers (TSFEL) with Planar Wiggler Magnet and AC Electrical Wiggler Pumps	wiggler, electron, FEL, free-electron-laser	136
	N. Mahdizadeh Islamic Azad University, Sabzevar Branch, Sabzevar, Iran F.M. Aghamir University of Tehran, Tehran, Iran
	Funding: Sabzevar Branch, Islamic Azad University A Comparison between growth rates of a Two Stream Free Electron Laser (TSFEL) with a planar wiggler pump and ac electrical wiggler pump has been presented. With the aid of fluid theory, dispersion relations are derived and their characteristics have been numerically analyzed. In this analysis, the longitudinal component of the stress tensor has been retained for beam temperature consideration. Similarities and differences in dispersion relations and growth rate have, also, been presented.

TUOCI1	Latest Developments for Photoinjector, Seeding and THz Laser Systems	cathode, gun, electron, radiation	173
	C.P. Hauri, A. Trisorio, C. Vicario Paul Scherrer Institut, Villigen, Switzerland C. Ruchert PSI, Villigen PSI, Switzerland
	For driving compact FEL facilities cutting edge laser technology is required. We present the latest laser developments and concepts for ultrastable and versatile electron gun lasers, seed lasers and high-power laser-based THz sources taking place at the Paul Scherrer Institute and at other Free Electron Laser facilities. Such developments are of fundamental interest for next generation FEL pump-probe experiments requiring a temporal resolution beyond state of the art.
	Slides TUOCI1 [5.159 MB]

TUOC3	High QE, Low Emittance, Green Sensitive FEL Photocathodes Using K₂CsSb	emittance, electron, cathode, gun	179
	H.A. Padmore, D. Dowell, J. Feng, T. Vecchione, W. Wan LBNL, Berkeley, California, USA I. Ben-Zvi Stony Brook University, Stony Brook, USA T. Rao, J. Smedley BNL, Upton, Long Island, New York, USA
	Funding: Work was supported by the Director, Office of Science, Office of Basic Energy Sciences of the U.S. Department of Energy, under Contract No. DE-AC02-05CH11231, KC0407-ALSJNT-I0013, and DE-SC0005713. We describe the development of photocathodes based on Potassium-Cesium-Antimonide that satisfy many of the key requirements of future light sources, such as robustness, high quantum efficiency when excited with visible light and low transverse emittance. We have demonstrated QE of 7% at 532 nm, a normalized transverse emittance of 0.36 μm at 543 nm and 3 MV/m field gradient[1]. We have also shown that the material can be relatively robust to residual water contamination and we have extracted current densities of 1 mA/mm² with very long lifetime. We believe that this work is an important step forward in FEL development where high repetition rate is required. [1] Applied Physics Letters (submitted)
	Slides TUOC3 [4.825 MB]

TUOC4	Design and First Experience with the FERMI Seed Laser	FEL, undulator, 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]

TUPA01	Tunable THz-pulse-train Photoinjector	electron, bunching, beat-wave, acceleration	187
	Y.-C. Huang, F.H. Chao, C.H. Chen, H.H. Chen, K.Y. Huang NTHU, Hsinchu, Taiwan
	Funding: This work is jointly supported by the National Science Council, under Contract NSC97-2112-M-007-018-MY2; the National Synchrotron Radiation Research Center,under Project 955LRF01N. A THz-pulse-train photoinjector is under construction at the High-energy OPtics and Electronics (HOPE) Laboratory at National Tsinghua University, Taiwan. This photoinjector is believed to be useful for generating high-power THz radiation, as well as for driving or loading a plasma-wave accelerator. A THz laser beat wave with full tunability in its beat frequency is employed to induce the emission of the THz electron pulses from the photoinjector. We show in our study that such a photoinjector is capable of generating periodically bunched MeV electrons with a bunching factor larger than 0.1 at THz frequencies for a total amount of 1 nC charges in a 10-ps time duration. We will also present a driver laser technology that can tune the electron bunch frequency with ease and help the growth of the high harmonics in the bunching spectrum of accelerated electrons. Experimental progress on this photoinjector will be reported in the conference.

TUPA02	Development of Material Analysis Facility in KU-FEL	FEL, lattice, electron, photon	190
	K. Yoshida, M. A. Bakr, Y.W. Choi, H. Imon, K. Ishida, T. Kii, N. Kimura, R. Kinjo, K. Komai, K. Masuda, H. Ohgaki, M. Omer, S. Shibata, K. Shimahashi, T. Sonobe, H. Zen Kyoto University, Institute for Advanced Energy, Kyoto, Japan
	A mid infrared-free electron laser (MIR-FEL) (5-20 μm) facility (KU-FEL: Kyoto University Free Electron Laser) has been constructed for contributing to researches on energy science at Institute of Advanced Energy, Kyoto University. Up to now 12-14 μm FEL beam has been generated. When MIR-FEL with the wavelength matched to the molecular vibration mode is irradiated to the material, a particular chemical bond in the material will be selectively excited, or dissociated [1]. The selective photochemical reaction can be applied for surface modification and the evaluation of material in biochemistry, chemistry, and solid physics. Therefore, material analysis facility in combination with MIR-FEL is constructed. In the material analysis facility, advanced analysis systems such as photoluminescence measurement system, photoelectron spectroscopy, super centrifuge and high performance liquids chromatography, ICP emission spectroscopy, and high speed atomic force spectroscopy are installed. In this meeting, the development of material analysis facility will be introduced. [1] Jhon C.Tully, Science, 312(2006) 1004

TUPA04	sFLASH - Present Status and Commisioning Results	undulator, electron, 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	electron, undulator, 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.

TUPA09	LUNEX5: A FEL Project Towards the Fifth Generation in France	FEL, electron, undulator, 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.

TUPA11	Saturation Effect on VUV Coherent Harmonic Generation at UVSOR-II	electron, simulation, FEL, bunching	212
	T. Tanikawa PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France M. Adachi, M. Katoh, J. Yamazaki, H. Zen UVSOR, Okazaki, Japan M. Hosaka, Y. Taira, N. Yamamoto Nagoya University, Nagoya, Japan
	Light source by using a laser seeding technique are under development at the UVSOR-II electron storage ring. In the past experiments, we have succeeded in generating coherent harmonics (CHs) in deep ultraviolet (UV) and vacuum UV (VUV) region, and also in generating CH with variable polarizations in deep UV [1]. In previous conferences, we reported an introduction of new-constructed spectrometer for VUV and results of spectra measurement, undulator gap dependencies, and injection laser power dependencies on VUV CHs [2]. This time we have successfully observed saturation on CHs intensities and have found some interesting phenomena, which are the necessary power of injection laser to achieve the saturation of CHG is different in different harmonic orders, and the CH intensity is oscillated in deep saturated regime. In this conference, we will discuss the results of some systematic measurements and those analytical and particle tracking simulations. [1] M. Labat, et al., Phys. Rev. Lett. 101 (2008) 164803 [2] T. Tanikawa, et al., Prc. 1st Int. Particle Accelerator Conf., Kyoto, 2010. [3] T. Tanikawa, et al., Appl. Phys. Express 3 (2010) 122702

TUPA13	Present Status and Future Prospects of Project on Utilizing Coherent Light Sources for User Experiments at UVSOR-II	electron, FEL, storage-ring, undulator	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	undulator, 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)

TUPA16	A Simple Spectral Calibration Technique for Terahertz Free Electron Laser Radiation	FEL, radiation, electron, cavity	227
	G. Berden FOM Rijnhuizen, Nieuwegein, The Netherlands R.T. Jongma, F.J.P. Wijnen, H.J.F.M. van der Pluijm Radboud University, Nijmegen, The Netherlands
	Upconversion of terahertz FEL radiation to the optical spectral region allows the use of highly efficient optical detection techniques (such as photo-diodes, spectrometers, array detectors) for sensitive characterization of the THz radiation. For online monitoring of the FEL radiation, a small fraction of the radiation is upconverted to the near-infrared region using a ZnTe crystal and a narrow bandwidth continuous wave (cw) laser operating at 780 nm. The ZnTe crystal does not need any angle tuning, and allows the efficient conversion of all wavelengths longer than 100 μm. Because the upconversion laser is cw, the FEL radiation is automatically temporally synchronized. Furthermore, its narrow bandwidth ensures that the spectral properties of the upconverted light can be directly related to the FEL radiation. In this contribution we demonstrate the upconversion technique for the spectral characterization of THz pulses of FELIX. In the near future, the upconversion spectrometer will be used as online wavelength spectrometer for FLARE, the THz FEL under construction at the Radboud University in Nijmegen which will operate in the 100-1500 μm spectral range.

TUPA21	Optical Synchronization of the SwissFEL 250 Mev Test Injector Gun Laser With the Optical Master Oscillator	controls, FEL, cathode, gun	243
	V.R. Arsov, S. Hunziker, M.G. Kaiser, V. Schlott Paul Scherrer Institut, Villigen, Switzerland F. Löhl CLASSE, Ithaca, New York, USA
	Funding: This work is partly supported by IRUVX-PP, an EU co-funded project under FP7 (Grant Agreement 211285) The SwissFEL gun laser stability is crucial for stable SASE operation in the hard X-ray regime. In 10 pC mode in which sub-10 fs photon pulses will be delivered for the users, the gun laser arrival time jitter at the cathode shouldn't exceed 30 fs (rms). In the present design it is foreseen that the gun oscillator is optically stabilized. It is also necessary to check the stability of the combination laser oscillator and transfer line with an optical reference. For this, the Ti:Sa oscillator was used as a master laser and its pulses were delivered through a ca. 5 m long free space transfer line to optically synchronize an Er-fiber oscillator via two color balanced optical cross correlator with a BBO crystal. The two lasers were placed on different optical tables, which didn't have a mechanical connection through the transfer line. Stable optical lock for at least 60 minutes was demonstrated with an in-loop stability in the range 3.7-17.6 fs. In the range 10 Hz-1 kHz the phase noise stability of the optically locked Er-fiber oscillator varied between 76.5 fs and 118.5 fs rms, 76 fs of which was the contribution of the 1.5 GHz PLO, to which the Ti:Sa oscillator was RF-locked.

TUPA22	FLASH II: A Project Update	undulator, kicker, 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.

TUPA25	EEHG Seeding Design for SwissFEL	bunching, electron, FEL, emittance	251
	E. Prat, S. Reiche Paul Scherrer Institut, Villigen, Switzerland
	The SwissFEL facility, planned at the Paul Scherrer Institute, is based on the SASE operation of a hard (1-7 Å) and a soft (7-70 Å) X-ray FEL beamline. In addition, seeding is foreseen for the soft X-ray beamline, down to a wavelength of 1 nm. The Echo-Enabled Harmonic Generation (EEHG) scheme, which utilizes a rather complex manipulation of the longitudinal phase space distribution of the electron beam to generate high harmonic density modulation, is presently considered the first choice for seeding at SwissFEL. However, EEHG is highly demanding and complex at 1 nm, therefore other strategies like High-Harmonic Generation (HHG) and self-seeding are also evaluated. This paper presents the current status of the seeding design for SwissFEL based on EEHG.

TUPA30	Multi-stage Bunch Compression at the Japanese X-ray Free Electron Laser SACLA	cavity, electron, linac, bunching	259
	K. Togawa, T. Hara, H. Tanaka RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	The Japanese x-ray free electron laser facility, named as SACLA (Spring-8 Angstrom Compact free electron LAser), was constructed at SPring-8 site. After finishing installation of all accelerator components, beam commissioning started on February 21, 2011. In order to produce a high-quality electron beam with extremely low-emittance and high-peak current, SACLA adopts multi-stage bunch compression scheme that uses an injector velocity bunching system and following three magnetic bunch compressors. A design bunch compression factor reaches to 3000, namely the peak current of 1 A at the CeB6 thermionic gun increases up to 3 kA at the exit of the final bunch compressor at 1.4 GeV. A longitudinal bunch profile was measured using a transverse beam deflector cavity that was located at the exit of the final bunch compressor. After step-by-step beam commissioning from the injector, we have accomplished a peak current of 3 kA and a short bunch length less than 100 fs. In this conference, we will report the commissioning of the multi-stage bunch compression system at SACLA.

TUPB04	Status of the FEL User Facility FLASH	FEL, radiation, photon, electron	267
	S. Schreiber, B. Faatz, J. Feldhaus, K. Honkavaara, R. Treusch, M. Vogt DESY, Hamburg, Germany
	The free-electron laser FLASH at DESY, Germany has been upgraded in 2010 and extended its wavelength range down to 4.1 nm. Beside the increased electron beam energy to 1.25 GeV, an other important upgrade is the installation of 3.9 GHz superconducting RF cavities in the injector. They are used to shape the longitudinal electron beam phase space. Now, significantly more FEL radiation energy per pulse of up to several hundreds of microjoules are achieved. Moreover, the system allows to adjust the FEL pulse length, from long pulses of more than 200 fs to short pulses well below 50 fs. The upgraded FLASH facility shows an excellent performance in terms of FEL radiation quality and stability as well as in reliability of operation. The 3rd user period started as scheduled in September 2010.

TUPB09	Free Electron Lasers in 2011	FEL, electron, undulator, 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	undulator, 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.

TUPB14	Design Studies for Cascaded HGHG and EESHG Experiments Based on SDUV-FEL	radiation, FEL, electron, bunching	291
	C. Feng, J.H. Chen, H.X. Deng, Q. Gu, D. Wang, M. Zhang, Z.T. Zhao SINAP, Shanghai, People's Republic of China
	Funding: This work was supported by the National Natural Science Foundation of China (Grant No. 10935011). As a test facility for modern FEL R&D, The Shanghai deep ultra-violent FEL (SDUV-FEL) is now under upgrading for the cascading two stage of HGHG experiment. It is found that this upgraded facility will be also well suited for the echo-enabled staged harmonic generation (EESHG) scheme demonstration. With help of 3D simulation codes, design studies on the FEL physics for both these two schemes based on the upgraded SDUV-FEL is presented in this paper.

TUPB19	Design and Beam Dynamics Simulation for the Photoinjector of Shanghai Soft X-ray Free Electron Laser Test Facility	gun, linac, emittance, simulation	299
	W.-H. Huang, Q. Du, Y.-C. Du, H.J. Qian, C.-X. Tang, L.X. Yan TUB, Beijing, People's Republic of China
	The Shanghai soft X-ray free electron laser test facility (SXFEL) aims to radiate at 9 nm based on the cascaded high-gain harmonic-generation (HGHG) scheme. The photoinjector of SXFEL consists of Ti-sapphire driving laser system, S-band photocathode RF gun, booster linacs, laser heater, beam diagnostics and matching section. It will produce ~130 MeV electron beam in high charge regime (~0.5 nC) with a baseline transverse emittance of 1.5 mm-mrad. This paper will present basic designs and beam dynamics simulations of SXFEL photoinjector.

TUPB21	Conceptual Design of a High Brightness and Fully Coherent Free Electron Laser in VUV Regime	FEL, undulator, 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, undulator, 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	undulator, electron, FEL, 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, undulator, linac, photon	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.

WEOCI1	Beam Line Commissioning of a UV/VUV FEL at Jefferson Lab	FEL, electron, cavity, vacuum	326
	S.V. Benson, G.H. Biallas, K. Blackburn, D.B. Bullard, J.L. Coleman, C. Dickover, D. Douglas, F.K. Ellingsworth, P. Evtushenko, C.W. Gould, J.G. Gubeli, D. Hardy, C. Hernandez-Garcia, K. Jordan, J.M. Klopf, J. Kortze, R.A. Legg, M. Marchlik, S.W. Moore, G. Neil, T. Powers, D.W. Sexton, M.D. Shinn, C. Tennant, R.L. Walker, G.P. Williams, F.G. Wilson, S. Zhang JLAB, Newport News, Virginia, USA C. Clavero The College of William and Mary, Williamsburg, USA
	Funding: Work supported by U.S. DOE Contract DE-AC05-84-ER40150, Air Force Office of Scientific Research, DOE Basic Energy Sciences, Office of Naval Research, and the Joint Technology Office. Many novel applications in photon sciences require very high source brightness and/or short pulses in the vacuum ultra-violet (VUV). Jefferson Lab has commissioned a UV oscillator with high gain and has transported the third harmonic of the UV to a user lab. The experimental performance of the UV FEL is much better than simulated performance in both gain and efficiency. This success is important for efforts to push towards higher gain FELs at short wavelengths where mirrors absorb strongly. We will report on efforts to characterize the UV laser and the VUV coherent harmonics as well as designs to lase directly in the VUV wavelength range.
	Slides WEOCI1 [3.331 MB]

WEPA01	Commissioning of a Photoinjector in HLS	cathode, emittance, solenoid, gun	331
	Z.G. He, Q.K. Jia, B.G. Sun, X.H. Wang USTC/NSRL, Hefei, Anhui, People's Republic of China
	A BNL type photoinjector was installed in HLS (Hefei Light Source) and commissioning work was carrying out in last months. The dark current was measured when the high power testing of the gun was processed. The quantum efficiency (QE) of the photocathode was measured and studied, the main parameters of beam quality such as electric charge, transverse emittance and energy were measured and presented in this paper.

WEPA06	Experimental Studies with Spatial Gaussian-cut Laser for the LCLS Photocathode Gun	emittance, simulation, cathode, electron	341
	F. Zhou, A. Brachmann, P. Emma, A. Gilevich, Z. Huang SLAC, Menlo Park, California, USA
	Funding: U.S. Department of Energy under contract DE-AC02-76SF00515 To further enhance the LCLS injector performances or simplify its operating conditions, we are evaluating the various parameters including the photocathode drive laser. Simulations show that both the projected and time-sliced emittances with spatial Gaussian profiles having reasonable tail-cutoff are better than those with uniform one. The simulated results are also supported by theoretical analyses. In the LCLS, the spatial uniform or quasi-Gaussian laser profiles are conveniently obtained by adjusting the optics of telescope upstream of an iris, used to define laser size on the cathode. Preliminary beam studies at the LCLS show that both the projected and time-sliced emittances with spatial quasi-Gaussian laser are almost as good as, although not better than, those with uniform one, and also laser transmission through the iris with the quasi-Gaussian is twice that with uniform one, which is to ease copper cathode operations and thus improve the LCLS operation efficiency. More beam studies are planned in the coming summer to measure FEL performances with the quasi-Gaussian in comparison with the uniform one. All simulations and measurements are presented.

WEPA12	The Driving Laser for FEL-THz	FEL, cathode, gun, electron	349
	Y. Chen, M. Li, H.B. Wang, D. Wu, X. Yang CAEP/IAE, Mianyang, Sichuan, People's Republic of China
	A solid-state driving laser system have been developed to meet the requirements of the FEL-THz research. The design specifications, configuration and diode-pumped amplifier of the drive-laser system are also described. The laser system can generate continuous or 10μs-20μs pulses light with wavelength 10⁶⁴ nm, 532nm, 266nm at a repetition rate 54.167MHz. The average power of the driving laser system is more than 25W, 8W, 1W at wavelength 1064nm, 532nm, 266nm respectively. The cathode material is GaAs. The second harmonic is used, of which average power is 8.55W, pulse width is about 12ps, power stability is 0.72% and pointing stability is 46urad.

WEPA17	Technical Developments for Injecting External Laser to a Storage Ring FEL in CW and Q-switched Operation	FEL, electron, injection, cavity	362
	H. Zen UVSOR, Okazaki, Japan M. Adachi, M. Katoh Sokendai - Okazaki, Okazaki, Aichi, Japan S. Bielawski, C. Szwaj PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France M. Hosaka Nagoya University, Nagoya, Japan
	For controlling the dynamics of a storage ring FEL, we propose to inject the FEL oscillator with an external laser [1]. Another purpose is generation of long sustain and intense coherent synchrotron radiation with combining Q-switched and injected FEL [2]. In this presentation, we will report on technical developments for injecting the external laser to FEL oscillator, which works both in CW and Q-switched operation. Optical system for injecting external laser and RF modulation system for Q-switching are newly developed. Practical problems and way to overcome them will be discussed. [1] C. Szwaj et al., FEL2011, TUPB05, in this conference. [2] M. Hosaka et al., FEL2011, WEOC4, in this conference.

WEPA18	Chirped Pulse Generation by CHG-FEL	FEL, electron, radiation, storage-ring	366
	H. Zen, T. Tanikawa UVSOR, Okazaki, Japan M. Adachi, M. Katoh Sokendai - Okazaki, Okazaki, Aichi, Japan M. Hosaka, N. Yamamoto Nagoya University, Nagoya, Japan
	Funding: Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Young Scientists (B), 23760067 (Japan) Coherent Harmonic Generation Free Electron Laser (CHG-FEL)* is one of the promising ways to generate coherent, femtosecond and short-wavelength optical pulses from electron bunches circulating in an electron storage ring. However, the CHG pulse energy becomes smaller as the shorter pulse of laser is used for driving CHG-FEL because the number of electrons which contribute to the CHG production is limited by the pulse duration of driving laser. We proposed “chirped pulse generation and compression of CHG-FEL” to overcome such trade-off relationship, and got a small budget for proof-of-principle experiments in DUV region. In the experiment, chirped DUV pulses will be generated by CHG-FEL driving with chirped laser, and the DUV pulses will be compressed by a pulse compressor. The pulse duration of CHG-FEL before and after the compressor will be measured by a crosscorrelator. The principle, strategy, present status, and future prospects will be presented in the conference. *R. Coisson and F De Martini, Physics of Quantum Electronics (Addison−Wesley, 1982) vol. 9. chap. 42.

WEPA19	Report on the Redesign of the Fibre Link Stabilisation Units at FLASH	optics, controls, alignment, free-electron-laser	370
	M.K. Bock, M. Bousonville, M. Felber, P. Gessler, T. Lamb, H. Schlarb, B. Schmidt, S. Schulz DESY, Hamburg, Germany M. Kuntzsch HZDR, Dresden, Germany
	Funding: This work is partly supported by IRUVX-PP an EU co-funded project under FP7 (Grant Agreement 211285) Recently, the fibre link stabilisation unit of the optical synchronisation system at FLASH has been subject to several design changes involving some major issues. Enhancements of the optical design have led to improvements in the efficiency of the free space optics and a new optical delay line allows for a more than two times longer adjustment range. The amplitude noise, encountered previously at the remote station of the links, was drastically decreased by a new beam splitting configuration. In future, this new link design will not only be used for the planned additional fibre links at FLASH, but it will also replace the already installed ones. In this paper we report on the changes of opto-mechanical design and we present first results from the recently commissioned links.

WEPA20	Designing a Pulse-resolved Photon Diagnostic System for Shanghai SXFEL	diagnostics, FEL, photon, synchrotron	374
	Y.Q. Wu, J.H. Chen, J.N. Liu, R.Z. Tai, D. Wang, R. Wang, C.F. Xue, G.F. Zhao SINAP, Shanghai, People's Republic of China
	It is presented the design of photon diagnostic system for SSRF-XFEL, the X-ray Free Electron Laser facility in Shanghai Synchrotron Radiation Facility. The system mainly includes a diagnostic beamline with two branches and some diagnostic devices. In the direct passing branch, the intensity distribution of the spot is measured. A set of multi-slit plates are applied for measuring the spatial coherence of a single FEL pulse; In the deflecting branch, a high-resolution VLS-PGM type monochromator, with a simple manual adjusting system, is set up for detecting spectrum of single FEL pulse. The measuring range of wavelength is 45nm-3nm. A fast responding EUV CCD ensures a high pulse resolution to 100Hz.

WEPA24	Error Analysis for Hybrid Undulators	undulator, insertion, insertion-device, free-electron-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, undulator	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.

WEPB05	Experiments on Femtosecond Stabilization of Fiber Link for Shanghai Soft-XFEL	FEL, electron, LLRF, controls	402
	X.P. Ma IHEP, Beijing, People's Republic of China B. Liu SINAP, Shanghai, People's Republic of China
	The Shanghai Soft X-ray Free Electron Laser (SXFEL) facility will be constructed in the Shanghai Synchrotron Radiation Facility (SSRF) campus. SXFEL will operate in the HGHG and/or EEHG mode and require a femtosecond timing distribution system as well as the synchronization between femtosecond pulsed lasers, femtosecond pulsed X-rays, CW microwave signals and electron bunches with 10 fs precision. The pulsed fiber laser based femtosecond T&S system which has been proposed by the MIT/DESY team is adopted. In this paper the status of the femtosecond T&S system for SXFEL is introduced. Some initial progress of the phase stabilization by electronics control when laser pulses transport though long optical fibers is presented.

WEPB15	Reversible Electron Beam Heater for Suppression of Microbunching Instabilities Based on Transverse Deflecting Cavities	emittance, linac, FEL, simulation	409
	C. Behrens DESY, Hamburg, Germany Z. Huang, D. Xiang SLAC, Menlo Park, California, USA
	The presence of the microbunching instability due to the compression of high-brightness electron beams at existing and future X-ray free-electron lasers (FEL) results in restrictions on the attainable lasing performance and renders diagnostics like beam imaging with optical transition radiation impossible. The instability can be suppressed by introducing additional energy spread, i.e. heating the beam, as demonstrated by the successful operation of the laser heater system at the Linac Coherent Light Source. The increased energy spread is typically tolerable for self-amplified spontaneous emission FELs but limits the effectiveness of seeded FELs. In this paper, we present a reversible electron beam heating system based on two transverse deflecting cavities (TCAV) in front and behind a bunch compressor chicane. The additional energy spread will be introduced in the first TCAV, which suppresses the microbunching instability, and then will be eliminated in the second TCAV. We show the feasibility of the suppression of microbunching instabilities based on calculations and simulations, and set limits to the acceptable jitter tolerances.

WEPB18	Development of the First U48 Undulator Prototype for the European X-ray Free Electron Laser	undulator, controls, alignment, FEL	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.

WEPB22	An Optical Streaking Method for Measuring Femtosecond Electron Bunches	electron, wiggler, FEL, background	431
	Y.T. Ding, K.L.F. Bane, Z. Huang SLAC, Menlo Park, California, USA
	The measurement of the ultra-short electron bunch on the femotosecond time scale constitutes a very challenging problem. In the X-ray free electron laser facilities such as the Linac Coherent Light Source (LCLS), generation of a sub-ten femtoseconds electron beam at low charge operation mode is possible, based on indirect measurements and computer simulations. Direct measurements are not available due to the resolution limit of the present diagnostics. We propose a new method based on the energy modulation of the ultra-short electron bunch by interacting with an optical laser in a short wiggler. Compared with a laser-based transverse deflector, which requires the laser wavelength much longer than the electron bunch length, here we propose a scheme to use a laser with its wavelength shorter than the electron bunch length, where the slope on the laser intensity envelope has been used to help distinguish the different periods. The calibration is simple and it is possible to reconstruct the bunch longitudinal profile from a single shot measurement.

THOB2	Advanced Beam Dynamics Experiments at SPARC	gun, emittance, radiation, electron	451
	A. Bacci, D. Alesini, M. Bellaveglia, M. Castellano, E. Chiadroni, G. Di Pirro, A. Drago, M. Ferrario, A. Gallo, G. Gatti, A. Ghigo, E. Pace, A.R. Rossi, C. Vaccarezza INFN/LNF, Frascati (Roma), Italy A. Cianchi Università di Roma II Tor Vergata, Roma, Italy M. Del Franco, L. Giannessi, A. Petralia, M. Quattromini, C. Ronsivalle, V. Surrenti ENEA C.R. Frascati, Frascati (Roma), Italy S. Lupi Coherentia, Naples, Italy B. Marchetti INFN-Roma II, Roma, Italy A. Mostacci, L. Palumbo Rome University La Sapienza, Roma, Italy V. Petrillo Universita' degli Studi di Milano, Milano, Italy L. Serafini Istituto Nazionale di Fisica Nucleare, Milano, Italy M. Serluca INFN-Roma, Roma, Italy
	The successful operation of the SPARC injector in the Velocity Bunching (VB) mode (bunches with 1 kA current with emittance of 3 mm-mrad have been produced) has opened new perspectives to conduct advanced beam dynamics experiments with ultra-short electron pulses able to extend the THz spectrum or to drive the FEL in the SASE Single Spike mode. A new technique called Laser Comb, able to generate a train of short pulses with high repetition rate, has been extensively tested in the VB configuration. Two electron beam pulses 300 fs long separated by 1 ps have been characterized and the spectrum produced by the SASE interaction has been observed, showing that both pulses have been correctly matched to the undulator and were both lasing. In this paper we report the experimental and theoretical results obtained so far.
	Slides THOB2 [6.673 MB]

THOB3	First Demonstration of a Slippage-dominant Superradiant Free-electron Laser Amplifier	FEL, electron, undulator, 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, undulator, FEL, 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, undulator, photon	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]

THPA06	Emittance for Different Bunch Charges at the Upgraded PITZ Facility	emittance, gun, booster, cavity	473
	S. Rimjaem, G. Asova, H.-J. Grabosch, M. Groß, L. Hakobyan, I.I. Isaev, Ye. Ivanisenko, M.A. Khojoyan, G. Klemz, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, A. Shapovalov, F. Stephan, G. Vashchenko, S. Weidinger DESY Zeuthen, Zeuthen, Germany M. Hoffmann, H. Schlarb DESY, Hamburg, Germany M.A. Nozdrin JINR, Dubna, Moscow Region, Russia D. Richter HZB, Berlin, Germany I.H. Templin, I. Will MBI, Berlin, Germany
	Optimizations of electron sources for short-wavelength Free Electron Laser (FELs) at the Photo Injector Test facility at DESY, location Zeuthen (PITZ) have been continued with a new radio frequency (RF) gun cavity, a new post-accelerating Cut Disk Structure (CDS) booster cavity and several upgraded diagnostic components. The new booster cavity allows stable operation with higher acceleration and longer pulse trains than the operation with the previous TESLA type cavity. Electron beams with a maximum mean momentum of about 25 MeV/c can be produced with the setup described in this paper. Together with the upgraded RF system for the gun and the new CDS booster cavity, the electron beam stability was significantly improved. A large fraction of the measurement program in 2010-2011was devoted to study the dependence of the transverse projected emittance on the bunch charge. Measurement results using this upgraded facility are reported and discussed.

THPA08	An Option of High Charge Operation for the European XFEL	emittance, electron, FEL, gun	481
	M. Krasilnikov, H.-J. Grabosch, M. Groß, L. Hakobyan, Ye. Ivanisenko, G. Klemz, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, S. Rimjaem, F. Stephan, G. Vashchenko, S. Weidinger DESY Zeuthen, Zeuthen, Germany G. Asova INRNE, Sofia, Bulgaria I.I. Isaev, A. Shapovalov MEPhI, Moscow, Russia M.A. Khojoyan ANSL, Yerevan, Armenia D. Richter HZB, Berlin, Germany E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany I.H. Templin, I. Will MBI, Berlin, Germany
	The 1.3 GHz superconducting accelerator developed in the framework of TESLA and the European XFEL project holds potential to accelerate high charge electron beams. This feature has been successfully demonstrated during the first run of the free electron laser at the TESLA Test Facility with lasing driven by electron bunches with a charge of up to 4 nC. Currently DESY and the European XFEL GmbH perform revision of the baseline parameters for the electron beam. In this report we discuss a potential option of operation of the European XFEL driven by high charge (1 nC to 3 nC) electron beams. We present the results of the production and characterization of high charge electron bunches. Experiments have been performed at PITZ and demonstrated good properties of the electron beam in terms of emittance. Simulations of the radiation properties of SASE FELs show that application of high charge electron beams will open up the possibility to generate radiation pulse energies up to a few hundred milli-Joule level.

THPA10	RF Photo Gun Stability Measurement at PITZ	gun, feedback, monitoring, cathode	485
	I.I. Isaev, G. Asova, H.-J. Grabosch, M. Groß, L. Hakobyan, Ye. Ivanisenko, G. Klemz, W. Köhler, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, S. Rimjaem, F. Stephan, G. Vashchenko, S. Weidinger, R.W. Wenndorff DESY Zeuthen, Zeuthen, Germany M. Hoffmann, H. Schlarb DESY, Hamburg, Germany M.A. Khojoyan ANSL, Yerevan, Armenia D. Richter BESSY GmbH, Berlin, Germany A. Shapovalov MEPhI, Moscow, Russia
	High stability of the RF photo gun is one of the necessary conditions for the successful operation of linac based free electron lasers. Fluctuations of the RF launch phase have significant influence on the beam quality. Investigation on the dependence of different gun parameters and selection of optimal conditions are required to achieve high RF gun phase stability. Measurements of the gun RF phase stability are based on beam charge and momentum monitoring downstream of the gun. The stability of the RF gun phase for different operating conditions has been measured at the Photo Injector Test facility at DESY in Zeuthen (PITZ) and the results will be presented.

THPA13	A 54.167MHz Laser Wire System for Free Electron Laser in CAEP	photon, electron, FEL, gun	493
	D. Wu TUB, Beijing, People's Republic of China W. Bai, M. Li, H.B. Wang, J. Wang CAEP/IAE, Mianyang, Sichuan, People's Republic of China
	The laser wire (LW) method has been demonstrated as an effective non-interceptive technique for measuring transverse electron beam size of CW FELs and ERLs. To measure the beam size of a CW DC gun, which is built as an electron source of THz FEL in China Academy of Engineering Physics (CAEP), a high repetition LW system is proposed. The first proposed system is going to be installed at the exit of the DC gun, where the energy of electron beam is extremely low. In this paper, the LW system adapted to the FEL beam parameters is discussed, and the main parameters are given.

THPA14	Upgrade of the Optical Synchronization System for FLASH II	FEL, electron, LLRF, feedback	496
	M. Felber, M.K. Bock, M. Bousonville, P. Gessler, T. Lamb, S. Ruzin, H. Schlarb, B. Schmidt, S. Schulz DESY, Hamburg, Germany
	The optical synchronization system at FLASH has been in operation since 2008. Due to continuous improvement and several upgrades it has become an integral part of the machine operation and of pump-probe experiments as both rely on its performance. In summer 2013, a second FEL section, called FLASH II, which is using the same accelerator as FLASH will start its operation to increase the number of user experiments and to test new seeding schemes. This also requires a major extension of the synchronization system since new clients have to be supplied with a 10 fs-stable timing signal. Six additional stabilized fiber links and the according end stations like bunch arrival time monitors and laser synchronization setups will be installed.

THPA15	Simulation Studies of Generating Ultra Short Pulses at PITZ	electron, emittance, simulation, cathode	499
	M.A. Khojoyan, M. Krasilnikov, A. Oppelt, F. Stephan DESY Zeuthen, Zeuthen, Germany M.A. Khojoyan ANSL, Yerevan, Armenia
	Generation of the ultra short electron bunches (<10fs bunch length) which have a small transverse phase space volume and relatively small energy spread is of great interest. Such bunches are required for fully coherent (transversally and longitudinally) FEL radiation (single spike lasing) and for plasma acceleration experiments. The Photo Injector Test Facility at DESY in Zeuthen has already demonstrated the possibility to generate and characterize high quality electron beams for a wide range of bunch charges. Currently electron bunches have a typical length of several ps. To study the possibility of producing short electron bunches at PITZ many beam dynamics simulations have been performed for 1pC bunch charge using the ASTRA code. The current PITZ beam line is supposed to be extended by a small magnet chicane. Several temporal profiles of the cathode laser pulse have been used for the simulations to produce ultra-short electron bunches with small transverse sizes. The results of the beam dynamics simulations are presented and discussed.

THPA18	Operation of the FLASH Photoinjector Laser System	electron, gun, cathode, controls	507
	S. Schreiber, M. Görler, K. Klose, T. Schulz, M. Staack DESY, Hamburg, Germany G. Klemz, G. Koss DESY Zeuthen, Zeuthen, Germany I.H. Templin, I. Will, H. Willert MBI, Berlin, Germany
	The photoinjector of FLASH uses an RF gun equipped with caesium telluride photocathodes illuminated by appropriate UV laser pulses as a source of ultra-bright electron beams. The superconducting accelerator of FLASH is able to accelerate thousands of electron bunches per second in burst mode. This puts special demands on the design of the electron source, especially the laser system. The fully diode pumped laser system is based on Nd:YLF and produces a train of 2400 UV pulses in a burst of 0.8 ms length with a repetition rate of 5 Hz and 800 pulses with 10 Hz. The single pulse energy is up to 25 μJ per pulse at 262 nm. The laser uses a pulsed oscillator synchronized to the master RF with a stability of better than 200 fs in arrival time at the RF gun. Special care has been taken to produce a uniform and stable pulse train in terms of pulse energy, shape, and phase. Since FLASH is a free-electron laser user facility, the laser is designed to operate for more than 8000 h per year without operator intervention and little maintenance. We report on operational experience with the new system brought in operation in spring 2010.

THPA19	Photocathodes at FLASH	cathode, gun, solenoid, electron	511
	S. Schreiber, H. Hansen, S. Lederer, H.-H. Sahling DESY, Hamburg, Germany P. Michelato, L. Monaco, D. Sertore INFN/LASA, Segrate (MI), Italy
	For several years now, caesium telluride photocathodes are successfully used in the photoinjector of the free electron laser FLASH at DESY, Germany. They show a high quantum efficiency and long lifetime. The injector produces routinely thousand of bunches per second with a single bunch charge in the range of 0.1 to 1.5 nC. Recent results on lifetime, quantum efficiency, darkcurrent, and operating experience is reported. At DESY, a new preparation system has been set-up. First cathodes have been produced and tested successfully.

THPA21	Commissioning of a Streak Camera for Laser Characterization at NML	space-charge, booster, linac, cryomodule	515
	J. Ruan, A.H. Lumpkin Fermilab, Batavia, USA T.J. Maxwell Northern Illinois University, DeKalb, Illinois, USA
	A streak camera will be used for longitudinal profile measurement of a drive laser for the superconducting radio frequency photoinjector test facility at Fermilab. We are evaluating both a Photek intensified CCD camera and a Hamamatsu cooled CCD camera as the readout camera option for the Hamamatsu C5680 streak camera unit with a synchroscan sweep unit. Trade on low signal sensitivity and spatial resolution for the two lens-coupled options are being evaluated. In addition, an ultrashort laser pulse from a Ti:sapphire laser is used to measure the temporal resolution for both configurations.

THPA23	Investigations on Thermal Emittance at PITZ	emittance, electron, cathode, simulation	519
	M. Otevřel, G. Asova, H.-J. Grabosch, M. Groß, L. Hakobyan, I.I. Isaev, Ye. Ivanisenko, M.A. Khojoyan, G. Klemz, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, B. Petrosyan, D. Richter, S. Rimjaem, A. Shapovalov, F. Stephan, G. Vashchenko, S. Weidinger DESY Zeuthen, Zeuthen, Germany S. Lederer DESY, Hamburg, Germany
	The main aim of the Photo-Injector Test Facility at DESY, location Zeuthen (PITZ) is to develop and test an FEL photo-injector system capable of producing high charge electron bunches of lowest possible transverse emittance, which has a fundamental impact on FEL performance. Recent measurement results at PITZ showed a fairly small electron beam transverse projected emittance [1] which increased interest in the thermal emittance and its contribution to the overall electron beam emittance budget. Therefore thermal emittance was investigated at PITZ. Results of these studies are presented and discussed.

THPA26	Feedback Strategies for Bunch Arrival Time Stabilization at FLASH Towards 10 fs	feedback, controls, electron, beam-loading	531
	Ch. Schmidt, M.K. Bock, W. Koprek, S. Pfeiffer, H. Schlarb DESY, Hamburg, Germany W. Jałmużna TUL-DMCS, Łódź, Poland
	Highly precise regulation of accelerator RF fields is a prerequisite for a stable and reproducible photon generation at Free Electron Lasers such as FLASH. Due to major improvements of the RF field controls during 2010 and 2011 the FEL performance and the beam stability was significantly improved. In order to facilitate femtosecond precision pump-probe and seeding experiments at FLASH a combination of RF and beam based feedback loops are used. In this paper, we present the achieved stabilization of the arrival time and the pulse compression at FLASH using intra-pulse train feedbacks. Current limitations and future steps toward sub-10fs rms jitter are discussed.

THPA30	First Results with Tomographic Reconstruction of the Transverse Phase Space at PITZ	emittance, booster, cathode, gun	543
	G. Asova, H.-J. Grabosch, M. Groß, L. Hakobyan, I.I. Isaev, Ye. Ivanisenko, M.A. Khojoyan, G. Klemz, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, S. Rimjaem, F. Stephan, G. Vashchenko DESY Zeuthen, Zeuthen, Germany G. Asova INRNE, Sofia, Bulgaria D. Richter HZB, Berlin, Germany
	The development of high brightness electron sources capable to drive FELs like FLASH and European XFEL is a major objective of the Photo-Injector Test Facility at DESY in Zeuthen, PITZ. A key parameter used to define the beam quality at PITZ is the transverse phase-space density distribution and its evolution along the beamline. Complementary to the standard phase-space measurement setup constituting slit-scan stations, a module for tomographic diagnostics has been commissioned in 2010/2011. It consists of four observation screens separated by FODO cells and an upstream matching section. The expected advantages of the tomography method are the possibility to measure both transverse planes simultaneously and an improved resolution for low charges and short pulse trains. The fundamental challenges are related to strong space-charge forces at low beam momentum of only 25~MeV/c at PITZ at the moment. Such a constraint presents an obstacle to obtain beam envelope parameters well-matched to the optics of the FODO lattice. This contribution presents the first practical experience with the phase-space tomography module.

THPA32	Femtosecond Stable Laser-to-RF Phase Detection Using Optical Modulators	controls, coupling, feedback, free-electron-laser	551
	T. Lamb, M.K. Bock, M. Bousonville, M. Felber, P. Gessler, F. Ludwig, S. Ruzin, H. Schlarb, B. Schmidt, S. Schulz DESY, Hamburg, Germany E. Janas Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
	Free-Electron Lasers like FLASH and the European XFEL require the synchronization of RF stations to the optical timing reference of the accelerator. For this purpose, a new technique to phase-lock RF sources to an optical pulse train has been invented. The new technique uses an opto-microwave coupling device together with an ultra-low phase-noise RF source operating at a frequency of 1.3 GHz. In our arrangement, the laser-to-RF phase detector is insensitive to amplitude fluctuations of the optical reference pulse train, which allows the detector to achieve femtosecond precision over long time periods. In this paper, we present the balanced laser-to-RF phase detection principle along with a tolerance study of the arrangement and first results from our prototype setup.

THPB01	Optical Comb and Interferometer Development for Laser Synchronization in Femtosecond FELs	FEL, controls, optics, feedback	561
	R.B. Wilcox, J.M. Byrd LBNL, Berkeley, California, USA R. Holzwarth Menlo Systems GmbH, Martinsried, Germany
	Funding: This work supported by the U.S. Department of Energy under contract DE-AC02-05CH11231 We describe a method of synchronizing lasers in FELs to potential sub-femtosecond precision using interferometry and optical clock techniques, and show supporting experimental results. This precision is needed for pump/probe experiments in ultrafast FELs. The proposed system consists of carrier/offset phase stabilized, pulsed lasers synchronized via a single optical frequency delivered over fiber, analogous to RF oscillators synchronized with a reference frequency, but at 200 to 400THz. Our tests of modelocked lasers, interferometers and stabilized CW lasers show that subsystems can perform to the required precision. We have synchronized fiber lasers to less than 10fs jitter using two different frequency comb line locking schemes, and demonstrated interferometers in a working FEL with less than 100as jitter over 150m fiber. Based on these tests and published work by others, we calculate the performance of an optimized, integrated timing system to be less than 1fs in the short term. Long term stability is maintained by feedback from X-ray/optical cross-correlation at the experiment.

THPB09	Study of the Microbunching Instablity in the LINAC of the Future Shanghai Soft X-ray FEL Facility (SXFEL)	linac, impedance, FEL, simulation	579
	D. Huang IIT, Chicago, Illinois, USA Q. Gu SINAP, Shanghai, People's Republic of China
	The microbunching instability in the LINAC of a FEL facility has always been an issue which may degrade the quality of the electron beam. As the result, the whole facility may not be working properly. Therefore, learning how to control and reduce the instability is the key to the success of a FEL project. Shanghai soft X-ray FEL project (SXFEL) has just been granted, once it is built, it will be the first X-ray FEL facility in China. In this article, detailed study will be given based on the design parameters of the facility to gain better understanding and control over the possible microbunching instability in SXFEL, which is important to the success of the project.

THPB14	APEX Project Phase 0 and I Status and Plans and Activities for Phase II	gun, cathode, cavity, electron	582
	F. Sannibale, B.J. Bailey, K.M. Baptiste, J.M. Byrd, A.L. Catalano, D. Colomb, C.W. Cork, J.N. Corlett, S. De Santis, L.R. Doolittle, J. Feng, D. Filippetto, G. Huang, S. Kwiatkowski, W.E. Norum, H.A. Padmore, C. F. Papadopoulos, G. Penn, G.J. Portmann, S. Prestemon, J. Qiang, D.G. Quintas, J.W. Staples, M.E. Stuart, T. Vecchione, M. Venturini, M. Vinco, W. Wan, R.P. Wells, M.S. Zolotorev, F.A. Zucca LBNL, Berkeley, California, USA M. J. Messerly, M.A. Prantil LLNL, Livermore, 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 The APEX project at the Lawrence Berkeley National Laboratory is devoted to the development of a high repetition rate (MHz-class) electron injector for X-ray FEL applications. The injector is based on a new concept photo-gun, utilizing a normal conducting 187 MHz RF cavity operating in CW mode in conjunction with high quantum efficiency photocathodes able to deliver the required repetition rates with available laser technology. The APEX activities are staged in two phases. In Phase I, the electron photo-gun is constructed, tested and several different photo-cathodes, such as alkali antimonides, Cs₂Te [1], diamond amplifiers [2], and metals, are tested at full repetition rate. In Phase II, a pulsed linac is added for accelerating the beam at several tens of MeV to prove the high brightness performance of the gun when integrated in an injector scheme. Based on funding availability, after Phase II, the program could also include testing of new undulator technologies and FEL studies. The status of Phase I, in its initial experimental phase, is described together with plans and activities for Phase II and beyond. [1] In collaboration with INFN-LASA, Milano, Italy. [2] In collaboration with Brookhaven National Laboratory, Upton NY, USA

THPB24	Generation and Acceleration of Uniformly-filled Ellipsoidal Bunches Obtained via Space-charge Expansion from a Semiconductor Photocathode	electron, cavity, booster, simulation	605
	P. Piot, J. Ruan, Y.-E. Sun, J.C.T. Thangaraj Fermilab, Batavia, USA T.J. Maxwell Northern Illinois University, DeKalb, Illinois, USA
	We report on the experimental generation, acceleration and characterization of a uniformly-filled electron bunch obtained via space-charge-driven expansion (so called "blow-out regime") at the A0 photoinjector at Fermilab. The beam is photoemitted from a CsTe photocathode using a short (<~200 fs) ultraviolet pulse obtained via frequency-tripling of an amplified Ti:Sp infrared pulse. The produced electron bunches are characterized with conventional diagnostics and the measurements are bench-marked against numerical simulations performed with ASTRA and GPT.

THPB27	Application and Design of the Streak and TV Readout Systems at PITZ	electron, radiation, booster, dipole	613
	M. Mahgoub, H.-J. Grabosch, M. Groß, L. Hakobyan, I.I. Isaev, Ye. Ivanisenko, M.A. Khojoyan, G. Klemz, M. Krasilnikov, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, D. Richter, S. Rimjaem, F. Stephan, G. Vashchenko, S. Weidinger DESY Zeuthen, Zeuthen, Germany G. Asova, J.W. Bähr DESY, Hamburg, Germany J. Rönsch-Schulenburg Uni HH, Hamburg, Germany K. Rosbach Humboldt University Berlin, Institut für Physik, Berlin, Germany
	Funding: Deutsches Elektronen-Synchrotron DESY, Germany The Photo Injector Test facility at DESY in Zeuthen (PITZ) was built to develop and optimize photoelectron injectors for FELs like FLASH and the European XFEL. In PITZ electrons can be accelerated to momenta up to 20 MeV/c. Optimization of all injector parameters such as the longitudinal properties of the electron bunch is needed. A streak system is used to measure the complete longitudinal phase space distribution of the bunch with an accuracy of few ps. In this system the electron beam penetrates Aerogel radiators or Optical Transition Radiation screens OTR and produces Cherenkov light, which is transported by an optical line to a streak camera. The emitted light presents the charge distribution in the electron bunch. Some modifications of the streak beamline, such as using a Hybrid of lenses and mirrors to improve resolution and using quartz lenses to overcome the radiation damage are foreseen. A TV system is used to observe the electron beam directly, where screens of Yttrium Aluminum Garnet YAG and OTR are used to produce a direct image of the beam. An overview of the existing systems, the measurements, the difficulties and future modifications will be presented.

THPB29	Design of a Low Emittance and High Repetition Rate S-band Photoinjector	gun, emittance, solenoid, cathode	621
	J.H. Han Diamond, Oxfordshire, United Kingdom
	One of key components for the success of X-ray free-electron lasers (FELs) is the electron injector. Injectors starting with photocathode RF guns provide exceptionally high brightness electron beams and therefore they are being adopted as injectors of X-ray FELs. In this paper we show how to improve the photoinjector performance in terms of emittance and repetition rate by means of components optimization based on mature technologies. Transverse emittance at an injector is reduced by optimizing the RF gun cavity design, gun solenoid position, and accelerating section position. The repetition rate of an injector mainly depends on the cooling capability of the gun cavity. By adopting the coaxial RF gun coupler and improving cooling-water channels of the gun, a maximum repetition rate of 1 kHz for the injector will be achieved.

THPB30	SwissFEL Injector Test Facility – Test and Plans	emittance, cathode, gun, cavity	625
	M. Pedrozzi, M. Aiba, S. Bettoni, B. Beutner, A. Falone, R. Ganter, R. Ischebeck, F. Le Pimpec, G.L. Orlandi, E. Prat, S. Reiche, T. Schietinger, A. Trisorio, C. Vicario Paul Scherrer Institut, Villigen, Switzerland
	In August 2010 the Paul Scherrer Institute inaugurated the SwissFEL Injector test facility as a first step toward the Swiss hard X-ray FEL planned at PSI. The main purpose of the facility is to demonstrate and consolidate the generation of high-brightness beam as required to drive the 6 GeV SwissFEL accelerator. Additionally the injector serves as a platform supporting development and test of accelerator components/systems and optimization procedures foreseen for SwissFEL. In this paper we report on the present status of the commissioning with some emphasis on emittance measurements and component performances. The scientific program and long-term plans will be discussed as well.

FROAI1	State-of-the-Art RF Distribution and Synchronization Techniques	controls, cavity, electron, klystron	633
	Y. Otake RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	In a recent FEL accelerator, the temporal stability of an accelerated electron beam is the most crucial problem to achieve stable lasing. The demanded temporal stability is less than several ten fs (rms) to stably keep an extremely high peak current formed at a bunch compressor, as well as attaining required temporal resolution of a pump-probe experiment. To realize this stability, elaborate rf distribution and synchronization system for the accelerator are strongly needed. One of the most promising methods to realize the system is unified instruments of laser technology and electrical technology. Because the system can control an rf phase based on optical wavelength resolution and reduce effects of environmental perturbations arising from temperature variation, vibration and electrical noise. Many institutes already employed the unified system comprising instruments, such as optical fiber signal transmission and in-phase and quadrature rf vector manipulation. We recently obtained less than 30 fs (rms) temporal fluctuation of electron beams at XFEL/SPring-8 “SACLA” by using this kind system. This paper reviews state of the art timing systems using the unified technology for FEL.

FROAI2	All-optical Femtosecond Timing System for the Fermi@Elettra FEL	FEL, linac, klystron, electron	641
	M. Ferianis, A.O. Borga, A. Bucconi, M. Predonzani, F. Rossi ELETTRA, Basovizza, Italy L. Pavlovič University of Ljubljana, Faculty of Electrical Engineering, Ljubljana, Slovenia
	FERMI@Elettra, a 4th generation light source under commissioning at Sincrotrone Trieste, is the first FEL facility to use an all-optical system for femtosecond timing and synchronization over the entire facility ranging from the photoinjector, linac, FEL and beamline endstations. The system is a unique combination of state-of-the-art femtosecond timing distribution based on pulsed and CW stabilized optical fiber links. We describe the details of this unique system and present the performance to date.
	Slides FROAI2 [4.210 MB]

FROA3	Sub-100-attosecond Timing Jitter Ultrafast Fiber Lasers for FEL Optical Master Oscillators	FEL, cavity, electron, free-electron-laser	648
	J. Kim, K. Jung, C. Kim, H. Kim, T.K. Kim, S. Park, Y. Song, H. Yang KAIST, Daejeon, Republic of Korea
	Funding: Pohang Accelerator Laboratory and NRF of Korea (2010-0003974) Future FELs require femtosecond and even sub-femtosecond timing precision over the entire facility. To meet this timing demand, optical techniques based on modulated cw lasers or ultrafast pulsed lasers have been investigated intensively. It has recently been shown that the timing system based on ultrafast fiber lasers and timing-stabilized fiber links enables long-term stable, sub-10-femtosecond level synchronization []. In order to achieve sub-femtosecond level synchronization, the optimization of timing jitter in ultrafast fiber lasers is required. In this work, by operating the fiber lasers at close-to-zero intracavity dispersion, we optimize the timing jitter of ultrafast fiber lasers toward sub-femtosecond level for the first time. The measured timing jitter of 80 MHz Er-fiber and Yb-fiber lasers is 100 attosecond and 185 attosecond, respectively, when integrated from 10 kHz to 40 MHz (Nyquist frequency) offset frequency. To our knowledge, this is the lowest high-frequency timing jitter from ultrafast fiber lasers so far. The sub-100-attosecond timing jitter from optical master oscillators is the first step toward attosecond-precision FEL timing systems. [1] J. Kim et al, "Drift-free femtosecond timing synchronization of remote optical and microwave sources," Nature Photonics 2, 733-736 (2008).*

FROA4	Response Matrix of Longitudinal Instrumentation in SwissFEL	diagnostics, feedback, instrumentation, electron	652
	R. Ischebeck, B. Beutner, R. Kalt, P. Peier, S. Reiche, T. Schilcher, V. Schlott Paul Scherrer Institut, Villigen, Switzerland
	Several sources of jitter and drift affect the longitudinal phase space dynamics of SwissFEL. To evaluate how drifts can be identified and corrected through appropriate diagnostics and beam-based feedbacks, the response matrix of possible longitudinal diagnostics on laser and RF stability is modeled. To this intent, photocathode laser intensity, laser arrival time, RF phases and RF amplitudes are individually varied in an ELEGANT model, and the expected response of on-line diagnostics on the simulated bunches is evaluated. By comparing the slope of the response to the expected resolution of the instrumentation, suitable monitors can be selected for a feedback.
	Slides FROA4 [2.837 MB]

Paper

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Other Keywords

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MOOA5

Coherent Harmonic Generation at the DELTA Storage Ring

electron, radiation, undulator, 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, electron, radiation, undulator

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]

MOPA02

Development of a Microscopic Irradiation Technique for Delivering VIS-FELs to Single Cells through a Fine-tapered Glass Rod

FEL, electron, controls, free-electron-laser

16

F. Shishikura
Nihon University School of Medicine, Tokyo, Japan
K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Tanaka
LEBRA, Funabashi, Japan

The first lasing of LEBRA* succeeded in 2001 to produce near infrared FELs, by which the higher harmonics generated by means of the non-linear optical crystals now covered with visible and near infrared regions from 0.35 to 6 microns. The VIS-FELs are of particular interest and are expected to reveal photochemical reactions of single cells, even those in living organisms. To do this, it is a prerequisite to develop a micro-irradiation technique for targeting a single cell without photochemical effect to neighboring cells. We have established a microscopic irradiation technique with VIS-FELs through a fine glass rod. The FEL delivered through a fine-tapered glass rod with a diameter of about 5 microns has two major advantages compared with conventional microscope irradiation systems. The first is to deliver the FEL directly into targeted single cells in accordance with standard microinjection techniques used in developmental biology. The second is the ability to irradiate specific areas of the cytoplasm including cell organelle without severely damaging targeted cells. Using this technique, we also report micro-irradiation experiments on targeted single cells in living organisms.
*Laboratory for Electron Beam Research and Application, Nihon University

MOPB05

Smith-Purcell Radiation with Negative-index Material

radiation, electron, free-electron-laser, feedback

20

D. Li, K. Imasaki
ILT, Suita, Osaka, Japan
M.R. Asakawa
Kansai University, Osaka, Japan
M. Hangyo, K. Takano
ILE Osaka, Suita, Japan
S. Miyamoto
LASTI, Hyogo, Japan
Y. Tsunawaki
OSU, Daito, Osaka, Japan
Z. Yang
UESTC, Chengdu, Sichuan, People's Republic of China

Smith-Purcell radiation from an electric line charge that moves, at constant speed, parallel to a grating made of metamaterial with negative index is analyzed. Through theoretical analysis and computations, we show that the Smith-Purcell radiation is stronger from a grating of negative-index material, than positive-index material and perfect conductor. Also, we found the radiation strongly depends on the values of permeability and permittivity.

MOPB06

Smith-Purcell Free Electron Laser with Bragg Reflector

electron, free-electron-laser, simulation, radiation

24

D. Li, K. Imasaki
ILT, Suita, Osaka, Japan
M.R. Asakawa
Kansai University, Osaka, Japan
M. Hangyo
ILE Osaka, Suita, Japan
S. Miyamoto
LASTI, Hyogo, Japan
Y. Tsunawaki
OSU, Daito, Osaka, Japan
Z. Yang
UESTC, Chengdu, Sichuan, People's Republic of China

Grating with Bragg reflectors for the Smith-Purcell free-electron laser is proposed to improve the reflection coefficient, resulting in enhancing the interaction of the surface wave with the electron beam and, consequently, relax the requirements to the electron beam. With the help of particle-in-cell simulations, it has been shown that, the usage of Bragg reflectors may improve the growth rate, shorten the time for the device to reach saturation and lower the start current for the operation of a Smith-Purcell free-electron laser.

MOPB07

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

electron, undulator, FEL, bunching

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.

MOPB16

New Tunable DUV Light Source for Seeding Free-electron Lasers

FEL, simulation, electron, undulator

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

MOPB19

Using Laser Harmonics to Increase Bunching Factor in EEHG

bunching, undulator, 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.

MOPB21

Seeded Radiation Sources with Sawtooth Waveforms

bunching, FEL, radiation, damping

53

D.F. Ratner
Stanford University, Stanford, California, USA
A. Chao
SLAC, Menlo Park, California, USA

Despite the recent success of SASE-based FELs, there is still considerable interest in driving coherent radiation sources with external seeding. Seeding schemes, such as HGHG and EEHG, can increase longitudinal coherence, decrease saturation lengths, and improve performance of tapering, polarization control and other FEL features. Typically, seeding schemes start with a simple sinusoidal modulation, which is manipulated to provide bunching at a high harmonic of the original wavelength. In this paper, we consider variations starting with a sawtooth modulation. The sawtooth creates a clean phase space structure, providing a maximal bunching factor without the need for an FEL interaction. While a pure sawtooth modulation is a theoretical construct, it is possible to approach the waveform by combining two or more of the composite wavelengths. We give examples of sawtooth seeding for HGHG, EEHG and other schemes including compressed seeding, steady state microbunching, and reversible seeding. Finally, we note that the sawtooth modulation may aid in suppression of the microbunching instability.

MOPB23

Reversible Seeding in Storage Rings

storage-ring, bunching, radiation, simulation

57

D.F. Ratner
Stanford University, Stanford, California, USA
A. Chao
SLAC, Menlo Park, California, USA

We propose to generate steady-state microbunching in a storage ring by implementing a reversible seeding scheme. High gain harmonic generation (HGHG) and echo-enhanced harmonic generation (EEHG) are two promising methods for microbunching linac electron beams. Because both schemes increase the energy spread of the seeded beam, they cannot drive a coherent radiator turn-by-turn in a storage ring. However, reversing the seeding process following the radiator minimizes the impact on the electron beam and may allow coherent radiation at or near the storage ring repetition rate. In this paper we describe the general idea and outline a proof-of-principle experiment.

MOPB29

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

radiation, electron, undulator, FEL

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.

MOPC01

Compact THz Radiation Source Based on a Photocathode RF Gun

wiggler, electron, gun, FEL

92

S. Liu
Shanghai Jiao Tong University, Shanghai, People's Republic of China
J. Urakawa
KEK, Ibaraki, Japan

Terahertz (THz) science and technology have already become the research highlight at present. In this paper, we put forward a proposal to generate THz radiation at tens of MW peak power. Due to the ultrafast laser and the high accelerating field of photocathode RF gun, we can generate and accelerate electron beam to several MeV, of which the bunch length is less than sub-ps. When the short electron bunches are injected into the wiggler, THz radiation based on Coherent Synchrotron Radiation could be achieved with tens of MW peak power. The whole THz FEL facility can be scaled to the size of a tabletop.

MOPC04

The Effects of Jitters on Coherent X-ray Radiation Using a Modulation Compression Scheme

radiation, electron, FEL, resonance

103

J. Qiang
LBNL, Berkeley, California, USA
J. Wu
SLAC, Menlo Park, California, USA

Modulation compression scheme based on a chirped beam, laser modulator and laser chirper, and two bunch compressors was proposed recently to generate coherent multi-color atto-second X-ray radiation [1]. In this paper, we will present studies of effects of the initial longitudinal beam chirp jitter, time synchronization jitter between the electron beam and the laser chirper, and the laser chirper amplitude jitter on the final coherent X-ray radiation.
[1]Ji Qiang and Juhao Wu, “Generation multi-color attosecond X-ray radiation through modulation compression,” arXiv:1102.4806v1.

MOPC21

Comparison of Growth Rates of Two-Stream Free Electron Lasers (TSFEL) with Planar Wiggler Magnet and AC Electrical Wiggler Pumps

wiggler, electron, FEL, free-electron-laser

136

N. Mahdizadeh
Islamic Azad University, Sabzevar Branch, Sabzevar, Iran
F.M. Aghamir
University of Tehran, Tehran, Iran

Funding: Sabzevar Branch, Islamic Azad University
A Comparison between growth rates of a Two Stream Free Electron Laser (TSFEL) with a planar wiggler pump and ac electrical wiggler pump has been presented. With the aid of fluid theory, dispersion relations are derived and their characteristics have been numerically analyzed. In this analysis, the longitudinal component of the stress tensor has been retained for beam temperature consideration. Similarities and differences in dispersion relations and growth rate have, also, been presented.

TUOCI1

Latest Developments for Photoinjector, Seeding and THz Laser Systems

cathode, gun, electron, radiation

173

C.P. Hauri, A. Trisorio, C. Vicario
Paul Scherrer Institut, Villigen, Switzerland
C. Ruchert
PSI, Villigen PSI, Switzerland

For driving compact FEL facilities cutting edge laser technology is required. We present the latest laser developments and concepts for ultrastable and versatile electron gun lasers, seed lasers and high-power laser-based THz sources taking place at the Paul Scherrer Institute and at other Free Electron Laser facilities. Such developments are of fundamental interest for next generation FEL pump-probe experiments requiring a temporal resolution beyond state of the art.

Slides TUOCI1 [5.159 MB]

TUOC3

High QE, Low Emittance, Green Sensitive FEL Photocathodes Using K₂CsSb

emittance, electron, cathode, gun

179

H.A. Padmore, D. Dowell, J. Feng, T. Vecchione, W. Wan
LBNL, Berkeley, California, USA
I. Ben-Zvi
Stony Brook University, Stony Brook, USA
T. Rao, J. Smedley
BNL, Upton, Long Island, New York, USA

Funding: Work was supported by the Director, Office of Science, Office of Basic Energy Sciences of the U.S. Department of Energy, under Contract No. DE-AC02-05CH11231, KC0407-ALSJNT-I0013, and DE-SC0005713.
We describe the development of photocathodes based on Potassium-Cesium-Antimonide that satisfy many of the key requirements of future light sources, such as robustness, high quantum efficiency when excited with visible light and low transverse emittance. We have demonstrated QE of 7% at 532 nm, a normalized transverse emittance of 0.36 μm at 543 nm and 3 MV/m field gradient[1]. We have also shown that the material can be relatively robust to residual water contamination and we have extracted current densities of 1 mA/mm² with very long lifetime. We believe that this work is an important step forward in FEL development where high repetition rate is required.
[1] Applied Physics Letters (submitted)

Slides TUOC3 [4.825 MB]

TUOC4

Design and First Experience with the FERMI Seed Laser

FEL, undulator, 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]

TUPA01

Tunable THz-pulse-train Photoinjector

electron, bunching, beat-wave, acceleration

187

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

Funding: This work is jointly supported by the National Science Council, under Contract NSC97-2112-M-007-018-MY2; the National Synchrotron Radiation Research Center,under Project 955LRF01N.
A THz-pulse-train photoinjector is under construction at the High-energy OPtics and Electronics (HOPE) Laboratory at National Tsinghua University, Taiwan. This photoinjector is believed to be useful for generating high-power THz radiation, as well as for driving or loading a plasma-wave accelerator. A THz laser beat wave with full tunability in its beat frequency is employed to induce the emission of the THz electron pulses from the photoinjector. We show in our study that such a photoinjector is capable of generating periodically bunched MeV electrons with a bunching factor larger than 0.1 at THz frequencies for a total amount of 1 nC charges in a 10-ps time duration. We will also present a driver laser technology that can tune the electron bunch frequency with ease and help the growth of the high harmonics in the bunching spectrum of accelerated electrons. Experimental progress on this photoinjector will be reported in the conference.

TUPA02

Development of Material Analysis Facility in KU-FEL

FEL, lattice, electron, photon

190

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

A mid infrared-free electron laser (MIR-FEL) (5-20 μm) facility (KU-FEL: Kyoto University Free Electron Laser) has been constructed for contributing to researches on energy science at Institute of Advanced Energy, Kyoto University. Up to now 12-14 μm FEL beam has been generated. When MIR-FEL with the wavelength matched to the molecular vibration mode is irradiated to the material, a particular chemical bond in the material will be selectively excited, or dissociated [1]. The selective photochemical reaction can be applied for surface modification and the evaluation of material in biochemistry, chemistry, and solid physics. Therefore, material analysis facility in combination with MIR-FEL is constructed. In the material analysis facility, advanced analysis systems such as photoluminescence measurement system, photoelectron spectroscopy, super centrifuge and high performance liquids chromatography, ICP emission spectroscopy, and high speed atomic force spectroscopy are installed. In this meeting, the development of material analysis facility will be introduced.
[1] Jhon C.Tully, Science, 312(2006) 1004

TUPA04

sFLASH - Present Status and Commisioning Results

undulator, electron, 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

electron, undulator, 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.

TUPA09

LUNEX5: A FEL Project Towards the Fifth Generation in France

FEL, electron, undulator, 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.

TUPA11

Saturation Effect on VUV Coherent Harmonic Generation at UVSOR-II

electron, simulation, FEL, bunching

212

T. Tanikawa
PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
M. Adachi, M. Katoh, J. Yamazaki, H. Zen
UVSOR, Okazaki, Japan
M. Hosaka, Y. Taira, N. Yamamoto
Nagoya University, Nagoya, Japan

Light source by using a laser seeding technique are under development at the UVSOR-II electron storage ring. In the past experiments, we have succeeded in generating coherent harmonics (CHs) in deep ultraviolet (UV) and vacuum UV (VUV) region, and also in generating CH with variable polarizations in deep UV [1]. In previous conferences, we reported an introduction of new-constructed spectrometer for VUV and results of spectra measurement, undulator gap dependencies, and injection laser power dependencies on VUV CHs [2]. This time we have successfully observed saturation on CHs intensities and have found some interesting phenomena, which are the necessary power of injection laser to achieve the saturation of CHG is different in different harmonic orders, and the CH intensity is oscillated in deep saturated regime. In this conference, we will discuss the results of some systematic measurements and those analytical and particle tracking simulations.
[1] M. Labat, et al., Phys. Rev. Lett. 101 (2008) 164803
[2] T. Tanikawa, et al., Prc. 1st Int. Particle Accelerator Conf., Kyoto, 2010.
[3] T. Tanikawa, et al., Appl. Phys. Express 3 (2010) 122702

TUPA13

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

electron, FEL, storage-ring, undulator

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

undulator, 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)

TUPA16

A Simple Spectral Calibration Technique for Terahertz Free Electron Laser Radiation

FEL, radiation, electron, cavity

227

G. Berden
FOM Rijnhuizen, Nieuwegein, The Netherlands
R.T. Jongma, F.J.P. Wijnen, H.J.F.M. van der Pluijm
Radboud University, Nijmegen, The Netherlands

Upconversion of terahertz FEL radiation to the optical spectral region allows the use of highly efficient optical detection techniques (such as photo-diodes, spectrometers, array detectors) for sensitive characterization of the THz radiation. For online monitoring of the FEL radiation, a small fraction of the radiation is upconverted to the near-infrared region using a ZnTe crystal and a narrow bandwidth continuous wave (cw) laser operating at 780 nm. The ZnTe crystal does not need any angle tuning, and allows the efficient conversion of all wavelengths longer than 100 μm. Because the upconversion laser is cw, the FEL radiation is automatically temporally synchronized. Furthermore, its narrow bandwidth ensures that the spectral properties of the upconverted light can be directly related to the FEL radiation. In this contribution we demonstrate the upconversion technique for the spectral characterization of THz pulses of FELIX. In the near future, the upconversion spectrometer will be used as online wavelength spectrometer for FLARE, the THz FEL under construction at the Radboud University in Nijmegen which will operate in the 100-1500 μm spectral range.

TUPA21

Optical Synchronization of the SwissFEL 250 Mev Test Injector Gun Laser With the Optical Master Oscillator

controls, FEL, cathode, gun

243

V.R. Arsov, S. Hunziker, M.G. Kaiser, V. Schlott
Paul Scherrer Institut, Villigen, Switzerland
F. Löhl
CLASSE, Ithaca, New York, USA

Funding: This work is partly supported by IRUVX-PP, an EU co-funded project under FP7 (Grant Agreement 211285)
The SwissFEL gun laser stability is crucial for stable SASE operation in the hard X-ray regime. In 10 pC mode in which sub-10 fs photon pulses will be delivered for the users, the gun laser arrival time jitter at the cathode shouldn't exceed 30 fs (rms). In the present design it is foreseen that the gun oscillator is optically stabilized. It is also necessary to check the stability of the combination laser oscillator and transfer line with an optical reference. For this, the Ti:Sa oscillator was used as a master laser and its pulses were delivered through a ca. 5 m long free space transfer line to optically synchronize an Er-fiber oscillator via two color balanced optical cross correlator with a BBO crystal. The two lasers were placed on different optical tables, which didn't have a mechanical connection through the transfer line. Stable optical lock for at least 60 minutes was demonstrated with an in-loop stability in the range 3.7-17.6 fs. In the range 10 Hz-1 kHz the phase noise stability of the optically locked Er-fiber oscillator varied between 76.5 fs and 118.5 fs rms, 76 fs of which was the contribution of the 1.5 GHz PLO, to which the Ti:Sa oscillator was RF-locked.

TUPA22

FLASH II: A Project Update

undulator, kicker, 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.

TUPA25

EEHG Seeding Design for SwissFEL

bunching, electron, FEL, emittance

251

E. Prat, S. Reiche
Paul Scherrer Institut, Villigen, Switzerland

The SwissFEL facility, planned at the Paul Scherrer Institute, is based on the SASE operation of a hard (1-7 Å) and a soft (7-70 Å) X-ray FEL beamline. In addition, seeding is foreseen for the soft X-ray beamline, down to a wavelength of 1 nm. The Echo-Enabled Harmonic Generation (EEHG) scheme, which utilizes a rather complex manipulation of the longitudinal phase space distribution of the electron beam to generate high harmonic density modulation, is presently considered the first choice for seeding at SwissFEL. However, EEHG is highly demanding and complex at 1 nm, therefore other strategies like High-Harmonic Generation (HHG) and self-seeding are also evaluated. This paper presents the current status of the seeding design for SwissFEL based on EEHG.

TUPA30

Multi-stage Bunch Compression at the Japanese X-ray Free Electron Laser SACLA

cavity, electron, linac, bunching

259

K. Togawa, T. Hara, H. Tanaka
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

The Japanese x-ray free electron laser facility, named as SACLA (Spring-8 Angstrom Compact free electron LAser), was constructed at SPring-8 site. After finishing installation of all accelerator components, beam commissioning started on February 21, 2011. In order to produce a high-quality electron beam with extremely low-emittance and high-peak current, SACLA adopts multi-stage bunch compression scheme that uses an injector velocity bunching system and following three magnetic bunch compressors. A design bunch compression factor reaches to 3000, namely the peak current of 1 A at the CeB6 thermionic gun increases up to 3 kA at the exit of the final bunch compressor at 1.4 GeV. A longitudinal bunch profile was measured using a transverse beam deflector cavity that was located at the exit of the final bunch compressor. After step-by-step beam commissioning from the injector, we have accomplished a peak current of 3 kA and a short bunch length less than 100 fs. In this conference, we will report the commissioning of the multi-stage bunch compression system at SACLA.

TUPB04

Status of the FEL User Facility FLASH

FEL, radiation, photon, electron

267

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

The free-electron laser FLASH at DESY, Germany has been upgraded in 2010 and extended its wavelength range down to 4.1 nm. Beside the increased electron beam energy to 1.25 GeV, an other important upgrade is the installation of 3.9 GHz superconducting RF cavities in the injector. They are used to shape the longitudinal electron beam phase space. Now, significantly more FEL radiation energy per pulse of up to several hundreds of microjoules are achieved. Moreover, the system allows to adjust the FEL pulse length, from long pulses of more than 200 fs to short pulses well below 50 fs. The upgraded FLASH facility shows an excellent performance in terms of FEL radiation quality and stability as well as in reliability of operation. The 3rd user period started as scheduled in September 2010.

TUPB09

Free Electron Lasers in 2011

FEL, electron, undulator, 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

undulator, 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.

TUPB14

Design Studies for Cascaded HGHG and EESHG Experiments Based on SDUV-FEL

radiation, FEL, electron, bunching

291

C. Feng, J.H. Chen, H.X. Deng, Q. Gu, D. Wang, M. Zhang, Z.T. Zhao
SINAP, Shanghai, People's Republic of China

Funding: This work was supported by the National Natural Science Foundation of China (Grant No. 10935011).
As a test facility for modern FEL R&D, The Shanghai deep ultra-violent FEL (SDUV-FEL) is now under upgrading for the cascading two stage of HGHG experiment. It is found that this upgraded facility will be also well suited for the echo-enabled staged harmonic generation (EESHG) scheme demonstration. With help of 3D simulation codes, design studies on the FEL physics for both these two schemes based on the upgraded SDUV-FEL is presented in this paper.

TUPB19

Design and Beam Dynamics Simulation for the Photoinjector of Shanghai Soft X-ray Free Electron Laser Test Facility

gun, linac, emittance, simulation

299

W.-H. Huang, Q. Du, Y.-C. Du, H.J. Qian, C.-X. Tang, L.X. Yan
TUB, Beijing, People's Republic of China

The Shanghai soft X-ray free electron laser test facility (SXFEL) aims to radiate at 9 nm based on the cascaded high-gain harmonic-generation (HGHG) scheme. The photoinjector of SXFEL consists of Ti-sapphire driving laser system, S-band photocathode RF gun, booster linacs, laser heater, beam diagnostics and matching section. It will produce ~130 MeV electron beam in high charge regime (~0.5 nC) with a baseline transverse emittance of 1.5 mm-mrad. This paper will present basic designs and beam dynamics simulations of SXFEL photoinjector.

TUPB21

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

FEL, undulator, 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, undulator, 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

undulator, electron, FEL, 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, undulator, linac, photon

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.

WEOCI1

Beam Line Commissioning of a UV/VUV FEL at Jefferson Lab

FEL, electron, cavity, vacuum

326

S.V. Benson, G.H. Biallas, K. Blackburn, D.B. Bullard, J.L. Coleman, C. Dickover, D. Douglas, F.K. Ellingsworth, P. Evtushenko, C.W. Gould, J.G. Gubeli, D. Hardy, C. Hernandez-Garcia, K. Jordan, J.M. Klopf, J. Kortze, R.A. Legg, M. Marchlik, S.W. Moore, G. Neil, T. Powers, D.W. Sexton, M.D. Shinn, C. Tennant, R.L. Walker, G.P. Williams, F.G. Wilson, S. Zhang
JLAB, Newport News, Virginia, USA
C. Clavero
The College of William and Mary, Williamsburg, USA

Funding: Work supported by U.S. DOE Contract DE-AC05-84-ER40150, Air Force Office of Scientific Research, DOE Basic Energy Sciences, Office of Naval Research, and the Joint Technology Office.
Many novel applications in photon sciences require very high source brightness and/or short pulses in the vacuum ultra-violet (VUV). Jefferson Lab has commissioned a UV oscillator with high gain and has transported the third harmonic of the UV to a user lab. The experimental performance of the UV FEL is much better than simulated performance in both gain and efficiency. This success is important for efforts to push towards higher gain FELs at short wavelengths where mirrors absorb strongly. We will report on efforts to characterize the UV laser and the VUV coherent harmonics as well as designs to lase directly in the VUV wavelength range.

Slides WEOCI1 [3.331 MB]

WEPA01

Commissioning of a Photoinjector in HLS

cathode, emittance, solenoid, gun

331

Z.G. He, Q.K. Jia, B.G. Sun, X.H. Wang
USTC/NSRL, Hefei, Anhui, People's Republic of China

A BNL type photoinjector was installed in HLS (Hefei Light Source) and commissioning work was carrying out in last months. The dark current was measured when the high power testing of the gun was processed. The quantum efficiency (QE) of the photocathode was measured and studied, the main parameters of beam quality such as electric charge, transverse emittance and energy were measured and presented in this paper.

WEPA06

Experimental Studies with Spatial Gaussian-cut Laser for the LCLS Photocathode Gun

emittance, simulation, cathode, electron

341

F. Zhou, A. Brachmann, P. Emma, A. Gilevich, Z. Huang
SLAC, Menlo Park, California, USA

Funding: U.S. Department of Energy under contract DE-AC02-76SF00515
To further enhance the LCLS injector performances or simplify its operating conditions, we are evaluating the various parameters including the photocathode drive laser. Simulations show that both the projected and time-sliced emittances with spatial Gaussian profiles having reasonable tail-cutoff are better than those with uniform one. The simulated results are also supported by theoretical analyses. In the LCLS, the spatial uniform or quasi-Gaussian laser profiles are conveniently obtained by adjusting the optics of telescope upstream of an iris, used to define laser size on the cathode. Preliminary beam studies at the LCLS show that both the projected and time-sliced emittances with spatial quasi-Gaussian laser are almost as good as, although not better than, those with uniform one, and also laser transmission through the iris with the quasi-Gaussian is twice that with uniform one, which is to ease copper cathode operations and thus improve the LCLS operation efficiency. More beam studies are planned in the coming summer to measure FEL performances with the quasi-Gaussian in comparison with the uniform one. All simulations and measurements are presented.

WEPA12

The Driving Laser for FEL-THz

FEL, cathode, gun, electron

349

Y. Chen, M. Li, H.B. Wang, D. Wu, X. Yang
CAEP/IAE, Mianyang, Sichuan, People's Republic of China

A solid-state driving laser system have been developed to meet the requirements of the FEL-THz research. The design specifications, configuration and diode-pumped amplifier of the drive-laser system are also described. The laser system can generate continuous or 10μs-20μs pulses light with wavelength 10⁶⁴ nm, 532nm, 266nm at a repetition rate 54.167MHz. The average power of the driving laser system is more than 25W, 8W, 1W at wavelength 1064nm, 532nm, 266nm respectively. The cathode material is GaAs. The second harmonic is used, of which average power is 8.55W, pulse width is about 12ps, power stability is 0.72% and pointing stability is 46urad.

WEPA17

Technical Developments for Injecting External Laser to a Storage Ring FEL in CW and Q-switched Operation

FEL, electron, injection, cavity

362

H. Zen
UVSOR, Okazaki, Japan
M. Adachi, M. Katoh
Sokendai - Okazaki, Okazaki, Aichi, Japan
S. Bielawski, C. Szwaj
PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
M. Hosaka
Nagoya University, Nagoya, Japan

For controlling the dynamics of a storage ring FEL, we propose to inject the FEL oscillator with an external laser [1]. Another purpose is generation of long sustain and intense coherent synchrotron radiation with combining Q-switched and injected FEL [2]. In this presentation, we will report on technical developments for injecting the external laser to FEL oscillator, which works both in CW and Q-switched operation. Optical system for injecting external laser and RF modulation system for Q-switching are newly developed. Practical problems and way to overcome them will be discussed.
[1] C. Szwaj et al., FEL2011, TUPB05, in this conference.
[2] M. Hosaka et al., FEL2011, WEOC4, in this conference.

WEPA18

Chirped Pulse Generation by CHG-FEL

FEL, electron, radiation, storage-ring

366

H. Zen, T. Tanikawa
UVSOR, Okazaki, Japan
M. Adachi, M. Katoh
Sokendai - Okazaki, Okazaki, Aichi, Japan
M. Hosaka, N. Yamamoto
Nagoya University, Nagoya, Japan

Funding: Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Young Scientists (B), 23760067 (Japan)
Coherent Harmonic Generation Free Electron Laser (CHG-FEL)* is one of the promising ways to generate coherent, femtosecond and short-wavelength optical pulses from electron bunches circulating in an electron storage ring. However, the CHG pulse energy becomes smaller as the shorter pulse of laser is used for driving CHG-FEL because the number of electrons which contribute to the CHG production is limited by the pulse duration of driving laser. We proposed “chirped pulse generation and compression of CHG-FEL” to overcome such trade-off relationship, and got a small budget for proof-of-principle experiments in DUV region. In the experiment, chirped DUV pulses will be generated by CHG-FEL driving with chirped laser, and the DUV pulses will be compressed by a pulse compressor. The pulse duration of CHG-FEL before and after the compressor will be measured by a crosscorrelator. The principle, strategy, present status, and future prospects will be presented in the conference.
*R. Coisson and F De Martini, Physics of Quantum Electronics (Addison−Wesley, 1982) vol. 9. chap. 42.

WEPA19

Report on the Redesign of the Fibre Link Stabilisation Units at FLASH

optics, controls, alignment, free-electron-laser

370

M.K. Bock, M. Bousonville, M. Felber, P. Gessler, T. Lamb, H. Schlarb, B. Schmidt, S. Schulz
DESY, Hamburg, Germany
M. Kuntzsch
HZDR, Dresden, Germany

Funding: This work is partly supported by IRUVX-PP an EU co-funded project under FP7 (Grant Agreement 211285)
Recently, the fibre link stabilisation unit of the optical synchronisation system at FLASH has been subject to several design changes involving some major issues. Enhancements of the optical design have led to improvements in the efficiency of the free space optics and a new optical delay line allows for a more than two times longer adjustment range. The amplitude noise, encountered previously at the remote station of the links, was drastically decreased by a new beam splitting configuration. In future, this new link design will not only be used for the planned additional fibre links at FLASH, but it will also replace the already installed ones. In this paper we report on the changes of opto-mechanical design and we present first results from the recently commissioned links.

WEPA20

Designing a Pulse-resolved Photon Diagnostic System for Shanghai SXFEL

diagnostics, FEL, photon, synchrotron

374

Y.Q. Wu, J.H. Chen, J.N. Liu, R.Z. Tai, D. Wang, R. Wang, C.F. Xue, G.F. Zhao
SINAP, Shanghai, People's Republic of China

It is presented the design of photon diagnostic system for SSRF-XFEL, the X-ray Free Electron Laser facility in Shanghai Synchrotron Radiation Facility. The system mainly includes a diagnostic beamline with two branches and some diagnostic devices. In the direct passing branch, the intensity distribution of the spot is measured. A set of multi-slit plates are applied for measuring the spatial coherence of a single FEL pulse; In the deflecting branch, a high-resolution VLS-PGM type monochromator, with a simple manual adjusting system, is set up for detecting spectrum of single FEL pulse. The measuring range of wavelength is 45nm-3nm. A fast responding EUV CCD ensures a high pulse resolution to 100Hz.

WEPA24

Error Analysis for Hybrid Undulators

undulator, insertion, insertion-device, free-electron-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, undulator

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.

WEPB05

Experiments on Femtosecond Stabilization of Fiber Link for Shanghai Soft-XFEL

FEL, electron, LLRF, controls

402

X.P. Ma
IHEP, Beijing, People's Republic of China
B. Liu
SINAP, Shanghai, People's Republic of China

The Shanghai Soft X-ray Free Electron Laser (SXFEL) facility will be constructed in the Shanghai Synchrotron Radiation Facility (SSRF) campus. SXFEL will operate in the HGHG and/or EEHG mode and require a femtosecond timing distribution system as well as the synchronization between femtosecond pulsed lasers, femtosecond pulsed X-rays, CW microwave signals and electron bunches with 10 fs precision. The pulsed fiber laser based femtosecond T&S system which has been proposed by the MIT/DESY team is adopted. In this paper the status of the femtosecond T&S system for SXFEL is introduced. Some initial progress of the phase stabilization by electronics control when laser pulses transport though long optical fibers is presented.

WEPB15

Reversible Electron Beam Heater for Suppression of Microbunching Instabilities Based on Transverse Deflecting Cavities

emittance, linac, FEL, simulation

409

C. Behrens
DESY, Hamburg, Germany
Z. Huang, D. Xiang
SLAC, Menlo Park, California, USA

The presence of the microbunching instability due to the compression of high-brightness electron beams at existing and future X-ray free-electron lasers (FEL) results in restrictions on the attainable lasing performance and renders diagnostics like beam imaging with optical transition radiation impossible. The instability can be suppressed by introducing additional energy spread, i.e. heating the beam, as demonstrated by the successful operation of the laser heater system at the Linac Coherent Light Source. The increased energy spread is typically tolerable for self-amplified spontaneous emission FELs but limits the effectiveness of seeded FELs. In this paper, we present a reversible electron beam heating system based on two transverse deflecting cavities (TCAV) in front and behind a bunch compressor chicane. The additional energy spread will be introduced in the first TCAV, which suppresses the microbunching instability, and then will be eliminated in the second TCAV. We show the feasibility of the suppression of microbunching instabilities based on calculations and simulations, and set limits to the acceptable jitter tolerances.

WEPB18

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

undulator, controls, alignment, FEL

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.

WEPB22

An Optical Streaking Method for Measuring Femtosecond Electron Bunches

electron, wiggler, FEL, background

431

Y.T. Ding, K.L.F. Bane, Z. Huang
SLAC, Menlo Park, California, USA

The measurement of the ultra-short electron bunch on the femotosecond time scale constitutes a very challenging problem. In the X-ray free electron laser facilities such as the Linac Coherent Light Source (LCLS), generation of a sub-ten femtoseconds electron beam at low charge operation mode is possible, based on indirect measurements and computer simulations. Direct measurements are not available due to the resolution limit of the present diagnostics. We propose a new method based on the energy modulation of the ultra-short electron bunch by interacting with an optical laser in a short wiggler. Compared with a laser-based transverse deflector, which requires the laser wavelength much longer than the electron bunch length, here we propose a scheme to use a laser with its wavelength shorter than the electron bunch length, where the slope on the laser intensity envelope has been used to help distinguish the different periods. The calibration is simple and it is possible to reconstruct the bunch longitudinal profile from a single shot measurement.

THOB2

Advanced Beam Dynamics Experiments at SPARC

gun, emittance, radiation, electron

451

A. Bacci, D. Alesini, M. Bellaveglia, M. Castellano, E. Chiadroni, G. Di Pirro, A. Drago, M. Ferrario, A. Gallo, G. Gatti, A. Ghigo, E. Pace, A.R. Rossi, C. Vaccarezza
INFN/LNF, Frascati (Roma), Italy
A. Cianchi
Università di Roma II Tor Vergata, Roma, Italy
M. Del Franco, L. Giannessi, A. Petralia, M. Quattromini, C. Ronsivalle, V. Surrenti
ENEA C.R. Frascati, Frascati (Roma), Italy
S. Lupi
Coherentia, Naples, Italy
B. Marchetti
INFN-Roma II, Roma, Italy
A. Mostacci, L. Palumbo
Rome University La Sapienza, Roma, Italy
V. Petrillo
Universita' degli Studi di Milano, Milano, Italy
L. Serafini
Istituto Nazionale di Fisica Nucleare, Milano, Italy
M. Serluca
INFN-Roma, Roma, Italy

The successful operation of the SPARC injector in the Velocity Bunching (VB) mode (bunches with 1 kA current with emittance of 3 mm-mrad have been produced) has opened new perspectives to conduct advanced beam dynamics experiments with ultra-short electron pulses able to extend the THz spectrum or to drive the FEL in the SASE Single Spike mode. A new technique called Laser Comb, able to generate a train of short pulses with high repetition rate, has been extensively tested in the VB configuration. Two electron beam pulses 300 fs long separated by 1 ps have been characterized and the spectrum produced by the SASE interaction has been observed, showing that both pulses have been correctly matched to the undulator and were both lasing. In this paper we report the experimental and theoretical results obtained so far.

Slides THOB2 [6.673 MB]

THOB3

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

FEL, electron, undulator, 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, undulator, FEL, 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, undulator, photon

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]

THPA06

Emittance for Different Bunch Charges at the Upgraded PITZ Facility

emittance, gun, booster, cavity

473

S. Rimjaem, G. Asova, H.-J. Grabosch, M. Groß, L. Hakobyan, I.I. Isaev, Ye. Ivanisenko, M.A. Khojoyan, G. Klemz, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, A. Shapovalov, F. Stephan, G. Vashchenko, S. Weidinger
DESY Zeuthen, Zeuthen, Germany
M. Hoffmann, H. Schlarb
DESY, Hamburg, Germany
M.A. Nozdrin
JINR, Dubna, Moscow Region, Russia
D. Richter
HZB, Berlin, Germany
I.H. Templin, I. Will
MBI, Berlin, Germany

Optimizations of electron sources for short-wavelength Free Electron Laser (FELs) at the Photo Injector Test facility at DESY, location Zeuthen (PITZ) have been continued with a new radio frequency (RF) gun cavity, a new post-accelerating Cut Disk Structure (CDS) booster cavity and several upgraded diagnostic components. The new booster cavity allows stable operation with higher acceleration and longer pulse trains than the operation with the previous TESLA type cavity. Electron beams with a maximum mean momentum of about 25 MeV/c can be produced with the setup described in this paper. Together with the upgraded RF system for the gun and the new CDS booster cavity, the electron beam stability was significantly improved. A large fraction of the measurement program in 2010-2011was devoted to study the dependence of the transverse projected emittance on the bunch charge. Measurement results using this upgraded facility are reported and discussed.

THPA08

An Option of High Charge Operation for the European XFEL

emittance, electron, FEL, gun

481

M. Krasilnikov, H.-J. Grabosch, M. Groß, L. Hakobyan, Ye. Ivanisenko, G. Klemz, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, S. Rimjaem, F. Stephan, G. Vashchenko, S. Weidinger
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
I.I. Isaev, A. Shapovalov
MEPhI, Moscow, Russia
M.A. Khojoyan
ANSL, Yerevan, Armenia
D. Richter
HZB, Berlin, Germany
E. Schneidmiller, M.V. Yurkov
DESY, Hamburg, Germany
I.H. Templin, I. Will
MBI, Berlin, Germany

The 1.3 GHz superconducting accelerator developed in the framework of TESLA and the European XFEL project holds potential to accelerate high charge electron beams. This feature has been successfully demonstrated during the first run of the free electron laser at the TESLA Test Facility with lasing driven by electron bunches with a charge of up to 4 nC. Currently DESY and the European XFEL GmbH perform revision of the baseline parameters for the electron beam. In this report we discuss a potential option of operation of the European XFEL driven by high charge (1 nC to 3 nC) electron beams. We present the results of the production and characterization of high charge electron bunches. Experiments have been performed at PITZ and demonstrated good properties of the electron beam in terms of emittance. Simulations of the radiation properties of SASE FELs show that application of high charge electron beams will open up the possibility to generate radiation pulse energies up to a few hundred milli-Joule level.

THPA10

RF Photo Gun Stability Measurement at PITZ

gun, feedback, monitoring, cathode

485

I.I. Isaev, G. Asova, H.-J. Grabosch, M. Groß, L. Hakobyan, Ye. Ivanisenko, G. Klemz, W. Köhler, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, S. Rimjaem, F. Stephan, G. Vashchenko, S. Weidinger, R.W. Wenndorff
DESY Zeuthen, Zeuthen, Germany
M. Hoffmann, H. Schlarb
DESY, Hamburg, Germany
M.A. Khojoyan
ANSL, Yerevan, Armenia
D. Richter
BESSY GmbH, Berlin, Germany
A. Shapovalov
MEPhI, Moscow, Russia

High stability of the RF photo gun is one of the necessary conditions for the successful operation of linac based free electron lasers. Fluctuations of the RF launch phase have significant influence on the beam quality. Investigation on the dependence of different gun parameters and selection of optimal conditions are required to achieve high RF gun phase stability. Measurements of the gun RF phase stability are based on beam charge and momentum monitoring downstream of the gun. The stability of the RF gun phase for different operating conditions has been measured at the Photo Injector Test facility at DESY in Zeuthen (PITZ) and the results will be presented.

THPA13

A 54.167MHz Laser Wire System for Free Electron Laser in CAEP

photon, electron, FEL, gun

493

D. Wu
TUB, Beijing, People's Republic of China
W. Bai, M. Li, H.B. Wang, J. Wang
CAEP/IAE, Mianyang, Sichuan, People's Republic of China

The laser wire (LW) method has been demonstrated as an effective non-interceptive technique for measuring transverse electron beam size of CW FELs and ERLs. To measure the beam size of a CW DC gun, which is built as an electron source of THz FEL in China Academy of Engineering Physics (CAEP), a high repetition LW system is proposed. The first proposed system is going to be installed at the exit of the DC gun, where the energy of electron beam is extremely low. In this paper, the LW system adapted to the FEL beam parameters is discussed, and the main parameters are given.

THPA14

Upgrade of the Optical Synchronization System for FLASH II

FEL, electron, LLRF, feedback

496

M. Felber, M.K. Bock, M. Bousonville, P. Gessler, T. Lamb, S. Ruzin, H. Schlarb, B. Schmidt, S. Schulz
DESY, Hamburg, Germany

The optical synchronization system at FLASH has been in operation since 2008. Due to continuous improvement and several upgrades it has become an integral part of the machine operation and of pump-probe experiments as both rely on its performance. In summer 2013, a second FEL section, called FLASH II, which is using the same accelerator as FLASH will start its operation to increase the number of user experiments and to test new seeding schemes. This also requires a major extension of the synchronization system since new clients have to be supplied with a 10 fs-stable timing signal. Six additional stabilized fiber links and the according end stations like bunch arrival time monitors and laser synchronization setups will be installed.

THPA15

Simulation Studies of Generating Ultra Short Pulses at PITZ

electron, emittance, simulation, cathode

499

M.A. Khojoyan, M. Krasilnikov, A. Oppelt, F. Stephan
DESY Zeuthen, Zeuthen, Germany
M.A. Khojoyan
ANSL, Yerevan, Armenia

Generation of the ultra short electron bunches (<10fs bunch length) which have a small transverse phase space volume and relatively small energy spread is of great interest. Such bunches are required for fully coherent (transversally and longitudinally) FEL radiation (single spike lasing) and for plasma acceleration experiments. The Photo Injector Test Facility at DESY in Zeuthen has already demonstrated the possibility to generate and characterize high quality electron beams for a wide range of bunch charges. Currently electron bunches have a typical length of several ps. To study the possibility of producing short electron bunches at PITZ many beam dynamics simulations have been performed for 1pC bunch charge using the ASTRA code. The current PITZ beam line is supposed to be extended by a small magnet chicane. Several temporal profiles of the cathode laser pulse have been used for the simulations to produce ultra-short electron bunches with small transverse sizes. The results of the beam dynamics simulations are presented and discussed.

THPA18

Operation of the FLASH Photoinjector Laser System

electron, gun, cathode, controls

507

S. Schreiber, M. Görler, K. Klose, T. Schulz, M. Staack
DESY, Hamburg, Germany
G. Klemz, G. Koss
DESY Zeuthen, Zeuthen, Germany
I.H. Templin, I. Will, H. Willert
MBI, Berlin, Germany

The photoinjector of FLASH uses an RF gun equipped with caesium telluride photocathodes illuminated by appropriate UV laser pulses as a source of ultra-bright electron beams. The superconducting accelerator of FLASH is able to accelerate thousands of electron bunches per second in burst mode. This puts special demands on the design of the electron source, especially the laser system. The fully diode pumped laser system is based on Nd:YLF and produces a train of 2400 UV pulses in a burst of 0.8 ms length with a repetition rate of 5 Hz and 800 pulses with 10 Hz. The single pulse energy is up to 25 μJ per pulse at 262 nm. The laser uses a pulsed oscillator synchronized to the master RF with a stability of better than 200 fs in arrival time at the RF gun. Special care has been taken to produce a uniform and stable pulse train in terms of pulse energy, shape, and phase. Since FLASH is a free-electron laser user facility, the laser is designed to operate for more than 8000 h per year without operator intervention and little maintenance. We report on operational experience with the new system brought in operation in spring 2010.

THPA19

Photocathodes at FLASH

cathode, gun, solenoid, electron

511

S. Schreiber, H. Hansen, S. Lederer, H.-H. Sahling
DESY, Hamburg, Germany
P. Michelato, L. Monaco, D. Sertore
INFN/LASA, Segrate (MI), Italy

For several years now, caesium telluride photocathodes are successfully used in the photoinjector of the free electron laser FLASH at DESY, Germany. They show a high quantum efficiency and long lifetime. The injector produces routinely thousand of bunches per second with a single bunch charge in the range of 0.1 to 1.5 nC. Recent results on lifetime, quantum efficiency, darkcurrent, and operating experience is reported. At DESY, a new preparation system has been set-up. First cathodes have been produced and tested successfully.

THPA21

Commissioning of a Streak Camera for Laser Characterization at NML

space-charge, booster, linac, cryomodule

515

J. Ruan, A.H. Lumpkin
Fermilab, Batavia, USA
T.J. Maxwell
Northern Illinois University, DeKalb, Illinois, USA

A streak camera will be used for longitudinal profile measurement of a drive laser for the superconducting radio frequency photoinjector test facility at Fermilab. We are evaluating both a Photek intensified CCD camera and a Hamamatsu cooled CCD camera as the readout camera option for the Hamamatsu C5680 streak camera unit with a synchroscan sweep unit. Trade on low signal sensitivity and spatial resolution for the two lens-coupled options are being evaluated. In addition, an ultrashort laser pulse from a Ti:sapphire laser is used to measure the temporal resolution for both configurations.

THPA23

Investigations on Thermal Emittance at PITZ

emittance, electron, cathode, simulation

519

M. Otevřel, G. Asova, H.-J. Grabosch, M. Groß, L. Hakobyan, I.I. Isaev, Ye. Ivanisenko, M.A. Khojoyan, G. Klemz, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, B. Petrosyan, D. Richter, S. Rimjaem, A. Shapovalov, F. Stephan, G. Vashchenko, S. Weidinger
DESY Zeuthen, Zeuthen, Germany
S. Lederer
DESY, Hamburg, Germany

The main aim of the Photo-Injector Test Facility at DESY, location Zeuthen (PITZ) is to develop and test an FEL photo-injector system capable of producing high charge electron bunches of lowest possible transverse emittance, which has a fundamental impact on FEL performance. Recent measurement results at PITZ showed a fairly small electron beam transverse projected emittance [1] which increased interest in the thermal emittance and its contribution to the overall electron beam emittance budget. Therefore thermal emittance was investigated at PITZ. Results of these studies are presented and discussed.

THPA26

Feedback Strategies for Bunch Arrival Time Stabilization at FLASH Towards 10 fs

feedback, controls, electron, beam-loading

531

Ch. Schmidt, M.K. Bock, W. Koprek, S. Pfeiffer, H. Schlarb
DESY, Hamburg, Germany
W. Jałmużna
TUL-DMCS, Łódź, Poland

Highly precise regulation of accelerator RF fields is a prerequisite for a stable and reproducible photon generation at Free Electron Lasers such as FLASH. Due to major improvements of the RF field controls during 2010 and 2011 the FEL performance and the beam stability was significantly improved. In order to facilitate femtosecond precision pump-probe and seeding experiments at FLASH a combination of RF and beam based feedback loops are used. In this paper, we present the achieved stabilization of the arrival time and the pulse compression at FLASH using intra-pulse train feedbacks. Current limitations and future steps toward sub-10fs rms jitter are discussed.

THPA30

First Results with Tomographic Reconstruction of the Transverse Phase Space at PITZ

emittance, booster, cathode, gun

543

G. Asova, H.-J. Grabosch, M. Groß, L. Hakobyan, I.I. Isaev, Ye. Ivanisenko, M.A. Khojoyan, G. Klemz, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, S. Rimjaem, F. Stephan, G. Vashchenko
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
D. Richter
HZB, Berlin, Germany

The development of high brightness electron sources capable to drive FELs like FLASH and European XFEL is a major objective of the Photo-Injector Test Facility at DESY in Zeuthen, PITZ. A key parameter used to define the beam quality at PITZ is the transverse phase-space density distribution and its evolution along the beamline. Complementary to the standard phase-space measurement setup constituting slit-scan stations, a module for tomographic diagnostics has been commissioned in 2010/2011. It consists of four observation screens separated by FODO cells and an upstream matching section. The expected advantages of the tomography method are the possibility to measure both transverse planes simultaneously and an improved resolution for low charges and short pulse trains. The fundamental challenges are related to strong space-charge forces at low beam momentum of only 25~MeV/c at PITZ at the moment. Such a constraint presents an obstacle to obtain beam envelope parameters well-matched to the optics of the FODO lattice. This contribution presents the first practical experience with the phase-space tomography module.

THPA32

Femtosecond Stable Laser-to-RF Phase Detection Using Optical Modulators

controls, coupling, feedback, free-electron-laser

551

T. Lamb, M.K. Bock, M. Bousonville, M. Felber, P. Gessler, F. Ludwig, S. Ruzin, H. Schlarb, B. Schmidt, S. Schulz
DESY, Hamburg, Germany
E. Janas
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland

Free-Electron Lasers like FLASH and the European XFEL require the synchronization of RF stations to the optical timing reference of the accelerator. For this purpose, a new technique to phase-lock RF sources to an optical pulse train has been invented. The new technique uses an opto-microwave coupling device together with an ultra-low phase-noise RF source operating at a frequency of 1.3 GHz. In our arrangement, the laser-to-RF phase detector is insensitive to amplitude fluctuations of the optical reference pulse train, which allows the detector to achieve femtosecond precision over long time periods. In this paper, we present the balanced laser-to-RF phase detection principle along with a tolerance study of the arrangement and first results from our prototype setup.

THPB01

Optical Comb and Interferometer Development for Laser Synchronization in Femtosecond FELs

FEL, controls, optics, feedback

561

R.B. Wilcox, J.M. Byrd
LBNL, Berkeley, California, USA
R. Holzwarth
Menlo Systems GmbH, Martinsried, Germany

Funding: This work supported by the U.S. Department of Energy under contract DE-AC02-05CH11231
We describe a method of synchronizing lasers in FELs to potential sub-femtosecond precision using interferometry and optical clock techniques, and show supporting experimental results. This precision is needed for pump/probe experiments in ultrafast FELs. The proposed system consists of carrier/offset phase stabilized, pulsed lasers synchronized via a single optical frequency delivered over fiber, analogous to RF oscillators synchronized with a reference frequency, but at 200 to 400THz. Our tests of modelocked lasers, interferometers and stabilized CW lasers show that subsystems can perform to the required precision. We have synchronized fiber lasers to less than 10fs jitter using two different frequency comb line locking schemes, and demonstrated interferometers in a working FEL with less than 100as jitter over 150m fiber. Based on these tests and published work by others, we calculate the performance of an optimized, integrated timing system to be less than 1fs in the short term. Long term stability is maintained by feedback from X-ray/optical cross-correlation at the experiment.

THPB09

Study of the Microbunching Instablity in the LINAC of the Future Shanghai Soft X-ray FEL Facility (SXFEL)

linac, impedance, FEL, simulation

579

D. Huang
IIT, Chicago, Illinois, USA
Q. Gu
SINAP, Shanghai, People's Republic of China

The microbunching instability in the LINAC of a FEL facility has always been an issue which may degrade the quality of the electron beam. As the result, the whole facility may not be working properly. Therefore, learning how to control and reduce the instability is the key to the success of a FEL project. Shanghai soft X-ray FEL project (SXFEL) has just been granted, once it is built, it will be the first X-ray FEL facility in China. In this article, detailed study will be given based on the design parameters of the facility to gain better understanding and control over the possible microbunching instability in SXFEL, which is important to the success of the project.

THPB14

APEX Project Phase 0 and I Status and Plans and Activities for Phase II

gun, cathode, cavity, electron

582

F. Sannibale, B.J. Bailey, K.M. Baptiste, J.M. Byrd, A.L. Catalano, D. Colomb, C.W. Cork, J.N. Corlett, S. De Santis, L.R. Doolittle, J. Feng, D. Filippetto, G. Huang, S. Kwiatkowski, W.E. Norum, H.A. Padmore, C. F. Papadopoulos, G. Penn, G.J. Portmann, S. Prestemon, J. Qiang, D.G. Quintas, J.W. Staples, M.E. Stuart, T. Vecchione, M. Venturini, M. Vinco, W. Wan, R.P. Wells, M.S. Zolotorev, F.A. Zucca
LBNL, Berkeley, California, USA
M. J. Messerly, M.A. Prantil
LLNL, Livermore, 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
The APEX project at the Lawrence Berkeley National Laboratory is devoted to the development of a high repetition rate (MHz-class) electron injector for X-ray FEL applications. The injector is based on a new concept photo-gun, utilizing a normal conducting 187 MHz RF cavity operating in CW mode in conjunction with high quantum efficiency photocathodes able to deliver the required repetition rates with available laser technology. The APEX activities are staged in two phases. In Phase I, the electron photo-gun is constructed, tested and several different photo-cathodes, such as alkali antimonides, Cs₂Te [1], diamond amplifiers [2], and metals, are tested at full repetition rate. In Phase II, a pulsed linac is added for accelerating the beam at several tens of MeV to prove the high brightness performance of the gun when integrated in an injector scheme. Based on funding availability, after Phase II, the program could also include testing of new undulator technologies and FEL studies. The status of Phase I, in its initial experimental phase, is described together with plans and activities for Phase II and beyond.
[1] In collaboration with INFN-LASA, Milano, Italy.
[2] In collaboration with Brookhaven National Laboratory, Upton NY, USA

THPB24

Generation and Acceleration of Uniformly-filled Ellipsoidal Bunches Obtained via Space-charge Expansion from a Semiconductor Photocathode

electron, cavity, booster, simulation

605

P. Piot, J. Ruan, Y.-E. Sun, J.C.T. Thangaraj
Fermilab, Batavia, USA
T.J. Maxwell
Northern Illinois University, DeKalb, Illinois, USA

We report on the experimental generation, acceleration and characterization of a uniformly-filled electron bunch obtained via space-charge-driven expansion (so called "blow-out regime") at the A0 photoinjector at Fermilab. The beam is photoemitted from a CsTe photocathode using a short (<~200 fs) ultraviolet pulse obtained via frequency-tripling of an amplified Ti:Sp infrared pulse. The produced electron bunches are characterized with conventional diagnostics and the measurements are bench-marked against numerical simulations performed with ASTRA and GPT.

THPB27

Application and Design of the Streak and TV Readout Systems at PITZ

electron, radiation, booster, dipole

613

M. Mahgoub, H.-J. Grabosch, M. Groß, L. Hakobyan, I.I. Isaev, Ye. Ivanisenko, M.A. Khojoyan, G. Klemz, M. Krasilnikov, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, D. Richter, S. Rimjaem, F. Stephan, G. Vashchenko, S. Weidinger
DESY Zeuthen, Zeuthen, Germany
G. Asova, J.W. Bähr
DESY, Hamburg, Germany
J. Rönsch-Schulenburg
Uni HH, Hamburg, Germany
K. Rosbach
Humboldt University Berlin, Institut für Physik, Berlin, Germany

Funding: Deutsches Elektronen-Synchrotron DESY, Germany
The Photo Injector Test facility at DESY in Zeuthen (PITZ) was built to develop and optimize photoelectron injectors for FELs like FLASH and the European XFEL. In PITZ electrons can be accelerated to momenta up to 20 MeV/c. Optimization of all injector parameters such as the longitudinal properties of the electron bunch is needed. A streak system is used to measure the complete longitudinal phase space distribution of the bunch with an accuracy of few ps. In this system the electron beam penetrates Aerogel radiators or Optical Transition Radiation screens OTR and produces Cherenkov light, which is transported by an optical line to a streak camera. The emitted light presents the charge distribution in the electron bunch. Some modifications of the streak beamline, such as using a Hybrid of lenses and mirrors to improve resolution and using quartz lenses to overcome the radiation damage are foreseen. A TV system is used to observe the electron beam directly, where screens of Yttrium Aluminum Garnet YAG and OTR are used to produce a direct image of the beam. An overview of the existing systems, the measurements, the difficulties and future modifications will be presented.

THPB29

Design of a Low Emittance and High Repetition Rate S-band Photoinjector

gun, emittance, solenoid, cathode

621

J.H. Han
Diamond, Oxfordshire, United Kingdom

One of key components for the success of X-ray free-electron lasers (FELs) is the electron injector. Injectors starting with photocathode RF guns provide exceptionally high brightness electron beams and therefore they are being adopted as injectors of X-ray FELs. In this paper we show how to improve the photoinjector performance in terms of emittance and repetition rate by means of components optimization based on mature technologies. Transverse emittance at an injector is reduced by optimizing the RF gun cavity design, gun solenoid position, and accelerating section position. The repetition rate of an injector mainly depends on the cooling capability of the gun cavity. By adopting the coaxial RF gun coupler and improving cooling-water channels of the gun, a maximum repetition rate of 1 kHz for the injector will be achieved.

THPB30

SwissFEL Injector Test Facility – Test and Plans

emittance, cathode, gun, cavity

625

M. Pedrozzi, M. Aiba, S. Bettoni, B. Beutner, A. Falone, R. Ganter, R. Ischebeck, F. Le Pimpec, G.L. Orlandi, E. Prat, S. Reiche, T. Schietinger, A. Trisorio, C. Vicario
Paul Scherrer Institut, Villigen, Switzerland

In August 2010 the Paul Scherrer Institute inaugurated the SwissFEL Injector test facility as a first step toward the Swiss hard X-ray FEL planned at PSI. The main purpose of the facility is to demonstrate and consolidate the generation of high-brightness beam as required to drive the 6 GeV SwissFEL accelerator. Additionally the injector serves as a platform supporting development and test of accelerator components/systems and optimization procedures foreseen for SwissFEL. In this paper we report on the present status of the commissioning with some emphasis on emittance measurements and component performances. The scientific program and long-term plans will be discussed as well.

FROAI1

State-of-the-Art RF Distribution and Synchronization Techniques

controls, cavity, electron, klystron

633

Y. Otake
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

In a recent FEL accelerator, the temporal stability of an accelerated electron beam is the most crucial problem to achieve stable lasing. The demanded temporal stability is less than several ten fs (rms) to stably keep an extremely high peak current formed at a bunch compressor, as well as attaining required temporal resolution of a pump-probe experiment. To realize this stability, elaborate rf distribution and synchronization system for the accelerator are strongly needed. One of the most promising methods to realize the system is unified instruments of laser technology and electrical technology. Because the system can control an rf phase based on optical wavelength resolution and reduce effects of environmental perturbations arising from temperature variation, vibration and electrical noise. Many institutes already employed the unified system comprising instruments, such as optical fiber signal transmission and in-phase and quadrature rf vector manipulation. We recently obtained less than 30 fs (rms) temporal fluctuation of electron beams at XFEL/SPring-8 “SACLA” by using this kind system. This paper reviews state of the art timing systems using the unified technology for FEL.

FROAI2

All-optical Femtosecond Timing System for the Fermi@Elettra FEL

FEL, linac, klystron, electron

641

M. Ferianis, A.O. Borga, A. Bucconi, M. Predonzani, F. Rossi
ELETTRA, Basovizza, Italy
L. Pavlovič
University of Ljubljana, Faculty of Electrical Engineering, Ljubljana, Slovenia

FERMI@Elettra, a 4th generation light source under commissioning at Sincrotrone Trieste, is the first FEL facility to use an all-optical system for femtosecond timing and synchronization over the entire facility ranging from the photoinjector, linac, FEL and beamline endstations. The system is a unique combination of state-of-the-art femtosecond timing distribution based on pulsed and CW stabilized optical fiber links. We describe the details of this unique system and present the performance to date.

Slides FROAI2 [4.210 MB]

FROA3

Sub-100-attosecond Timing Jitter Ultrafast Fiber Lasers for FEL Optical Master Oscillators

FEL, cavity, electron, free-electron-laser

648

J. Kim, K. Jung, C. Kim, H. Kim, T.K. Kim, S. Park, Y. Song, H. Yang
KAIST, Daejeon, Republic of Korea

Funding: Pohang Accelerator Laboratory and NRF of Korea (2010-0003974)
Future FELs require femtosecond and even sub-femtosecond timing precision over the entire facility. To meet this timing demand, optical techniques based on modulated cw lasers or ultrafast pulsed lasers have been investigated intensively. It has recently been shown that the timing system based on ultrafast fiber lasers and timing-stabilized fiber links enables long-term stable, sub-10-femtosecond level synchronization [*]. In order to achieve sub-femtosecond level synchronization, the optimization of timing jitter in ultrafast fiber lasers is required. In this work, by operating the fiber lasers at close-to-zero intracavity dispersion, we optimize the timing jitter of ultrafast fiber lasers toward sub-femtosecond level for the first time. The measured timing jitter of 80 MHz Er-fiber and Yb-fiber lasers is 100 attosecond and 185 attosecond, respectively, when integrated from 10 kHz to 40 MHz (Nyquist frequency) offset frequency. To our knowledge, this is the lowest high-frequency timing jitter from ultrafast fiber lasers so far. The sub-100-attosecond timing jitter from optical master oscillators is the first step toward attosecond-precision FEL timing systems.
[1] J. Kim et al, "Drift-free femtosecond timing synchronization of remote optical and microwave sources," Nature Photonics 2, 733-736 (2008).

FROA4

Response Matrix of Longitudinal Instrumentation in SwissFEL

diagnostics, feedback, instrumentation, electron

652

R. Ischebeck, B. Beutner, R. Kalt, P. Peier, S. Reiche, T. Schilcher, V. Schlott
Paul Scherrer Institut, Villigen, Switzerland

Several sources of jitter and drift affect the longitudinal phase space dynamics of SwissFEL. To evaluate how drifts can be identified and corrected through appropriate diagnostics and beam-based feedbacks, the response matrix of possible longitudinal diagnostics on laser and RF stability is modeled. To this intent, photocathode laser intensity, laser arrival time, RF phases and RF amplitudes are individually varied in an ELEGANT model, and the expected response of on-line diagnostics on the simulated bunches is evaluated. By comparing the slope of the response to the expected resolution of the instrumentation, suitable monitors can be selected for a feedback.

Slides FROA4 [2.837 MB]