| Paper |
Title |
Other Keywords |
Page |
| MOBAU02 |
Technology Challenges Towards Short-Wavelength FELs
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electron, emittance, radiation, space-charge |
9 |
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- J. Rossbach
Uni HH, Hamburg
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Since the very first proposal of high-gain FELs for the X-ray wavelength regime it was obvious that realization of such a device, potentially rewarding revolutionary science opportunities, would impose extraordinary challenges in terms of accelerator physics and technology. The talk will review the major steps that had to be taken to finally construct an FEL user facility for soft X-rays. Also, a few issues will be pointed out that are to be addressed in order to make full profit of the FEL principle at X-ray wavelengts.
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Slides
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| MOPPH006 |
Longitudinal Wake Field for an Electron Beam Accelerated through a Ultra-High Field Gradient
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electron, impedance, acceleration, radiation |
26 |
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- E. Saldin, E. Schneidmiller, M. V. Yurkov, G. Geloni
DESY, Hamburg
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Electron accelerators with higher longitudinal field gradients can produce high-energy beams with compact, cheap setups. Laser-plasma acceleration appears to constitute the more promising breakthrough in this direction, delivering field gradients up to TV/m. Here we describe the impact of longitudinal wake fields on the electron beam, based on solution of Maxwell's equations for the longitudinal field. We consider an acceleration distance much smaller than the overtaking length (the length that electrons travel as a light signal from the tail of the bunch overtakes the head of the bunch), that is the case for laser-plasma devices. We give expressions for impedance and wake function that may be evaluated numerically. We show that the rate of energy loss in the bunch due to radiative interaction is equal to that of coherently radiated energy in the far-zone. A limiting expression is found for a large distance of the electron beam from the accelerator compared with the overtaking length. We derive analytical solutions for a Gaussian transverse and longitudinal bunch shape. We apply our analytical asymptote by studying the feasibility of a Table-Top FEL based on laser-plasma driver. Numerical estimations indicate that the effects of the time-dependent energy change induced by the longitudinal wake pose a serious threat to the operation of this device. (See DESY 06-222)
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| MOPPH007 |
Theory of Nonlinear Harmonic Generation in Free-Electron Lasers with Helical Wigglers
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electron, wiggler, radiation, resonance |
30 |
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- E. Saldin, E. Schneidmiller, M. V. Yurkov, G. Geloni
DESY, Hamburg
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Coherent Harmonic Generation (CHG), and in particular Nonlinear Harmonic Generation (NHG), is of importance for both short wavelength Free-Electron Lasers (FELs), in relation with the achievement of shorter wavelengths with a fixed electron-beam energy, and high-average power FEL resonators, in relation with destructive effects of higher harmonics radiation on mirrors. In this paper we present a treatment of NHG from helical wigglers with particular emphasis on the second harmonic. Our study is based on an exact analytical solution of Maxwell's equations, derived with the help of a Green's function method. In particular, we demonstrate that nonlinear harmonic generation (NHG) from helical wigglers vanishes on axis. Our conclusion is in open contrast with results in literature, that include a kinematical mistake in the description of the electron motion. (See DESY 07-058)
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| MOPPH009 |
Undulator Radiation in a Waveguide
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resonance, radiation, vacuum, diagnostics |
34 |
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- E. Saldin, E. Schneidmiller, M. V. Yurkov, G. Geloni
DESY, Hamburg
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We propose an analytical approach to characterize undulator radiation near resonance, when the presence of the vacuum-pipe considerably affects radiation properties. This is the case of the far-infrared undulator beamline at the Free-electron LASer (FEL) in Hamburg (FLASH), that is designed to deliver pulses in the TeraHertz (THz) range. This undulator can be used for pump-probe experiments where THz pulses are naturally synchronized to the VUV pulse from the FEL, as well as the development of novel electron-beam diagnostics techniques. Since the THz radiation diffraction-size exceeds the vacuum-chamber dimensions, characterization of infrared radiation must be performed accounting for the presence of a waveguide. We developed a theory of undulator radiation in a waveguide based on paraxial and resonance approximation. We solved the field equation with a tensor Green's function technique, and extracted figure of merits describing in a simple way the influence of the vacuum-pipe on the radiation pulse as a function of the problem parameters. Our theory, that makes consistent use of dimensionless analysis, allows treatment and physical understanding of many asymptotes of the parameter space, together with their region of applicability. (See DESY 07-031)
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| MOPPH017 |
1D Linear Intensity Spiking Evolution in a Single Shot of a SASE FEL
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radiation, electron, free-electron-laser, laser |
54 |
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- V. Petrillo
Universita' degli Studi di Milano, Milano
- L. Serafini, C. Maroli
INFN-Milano, Milano
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The analysis is based on the 1D Maxwell-Lorentz equations which are reduced to the usual averaged linear equation in the limit of vanishingly small radiation field A(z,t) and average length lm. It is shown that if this equation is solved with initial shot noise conditions in which the widths of the spikes and the average distance between successive spikes are both uniformly smaller than the cooperation length Lc, it may lead to large amplitude coherent signals. The intensity spiking RMS relative amplitude decreases from the 100% values it has at t=0, down to values of the order or less than 0.1% in time intervals from ten to twenty gain times.
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| MOPPH020 |
FEL with Orotron Type Feedback
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electron, coupling, radiation, feedback |
61 |
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- R. Ando, K. Kamada
Kanazawa University, Kanazawa
- N. S. Ginzburg, N. Yu. Peskov, R. M. Rozental, A. Sergeev, V. Yu. Zaslavsky, A. Malkin
IAP/RAS, Nizhny Novgorod
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In microwave electronics orotron is widely used as a source of RF radiation in millimeter and submillimeter wavebands. In this device an electron beam is coupled to a mode of quasi-optical resonator by means of the periodical grating one of the resonator mirror. In our paper we discuss a relativistic modification of such a device. A novel FEL scheme is suggested in which the slow wave structure of orotron is replaced by shallow Bragg corrugation which provides the coupling of the transverse (with respect to direction of beam propagation) mode of a two-mirror cavity with longitudinally propagating wave. The latter can be excited by the electron beam wiggling in undulator field. Described scheme allows to combine selective properties of an orotron with relativistic frequency conversion of a free electron laser. The transverse mode provides the feedback in the system thus leading to self-excitation, while the propagating wave is responsible for energy extraction in the steady-state regime of operation. The discussed system was investigated both analytically and numerically using direct codes and averaged equations approach.
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| MOPPH022 |
A Description of Guided FEL Radiation Using Dielectric Waveguide Eigenmodes
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radiation, coupling, electron, bunching |
65 |
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| MOPPH023 |
Enhancing FEL Power with Phase Shifters
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radiation, electron, simulation, linac |
69 |
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- A. Chao, Z. Huang
SLAC, Menlo Park, California
- D. F. Ratner
Stanford University, Stanford, Califormia
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Undulator taper is a well-known technique to increase the FEL efficiency past saturation by maintaining the resonant condition. In this paper, we demonstrate that shifting the electron bunch phase relative to the radiation is equivalent to tapering the undulator parameter. Using discrete phase changes derived from optimized undulator tapers for the LCLS x-ray FEL, we show that placing appropriate phase shifters between undulator sections can reproduce the power enhancement of these undulator tapers. The phase shifters are relatively easy to implement and operate, and hence can be used to aid or replace the undulator taper for optimizing the FEL performance.
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| MOPPH034 |
Diagnostics of an Electron Beam using Coherent Cherenkov Radiation
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radiation, electron, laser, diagnostics |
95 |
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| MOPPH036 |
First Experiences with the FIR-FEL at ELBE
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electron, laser, radiation, free-electron-laser |
97 |
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- P. Michel, W. Seidel, G. Staats, J. Teichert, R. Wuensch, U. Lehnert
FZD, Dresden
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We show the design and the parameters of operation of the long-wavelength (U100) FEL of ELBE. First lasing has been shown in August, 2006. Since then, the laser has undergone thorough commissioning and is available for user experiments since fall, 2006. Besides in-house users the IR beam is available to external users in the FELBE (FEL@ELBE) program witch is a part of the integrated activity on synchrotron and free electron laser science in the EU. At the beginning of 2007 lasing in the full designed wavelength range from 20μm to 200μm was demonstrated. The laser power typically reaches several W in CW operation but drops for very long wavelengths depending on the size of the used outcoupling hole. However, there exists a serious problem with small gaps in the providable wavelength spectrum. We attribute this behaviour to the transmission characteristics of the overmoded partial waveguide used from the undulator entrance to the first mirror.
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| MOPPH043 |
Control and Diagnostic System of Novosibirsk FEL Radiation
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radiation, controls, diagnostics, linac |
111 |
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- V. V. Kubarev, E. V. Makashov, K. S. Palagin, S. S. Serednyakov
BINP SB RAS, Novosibirsk
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The architecture the main capabilities of control and diagnostic system of the Novosibirsk FEL coherent radiation are described. The client-server model is used for software, controlling this system. The developed software is capable to work both in client and server mode. Also it can control various equipment – from FEL optical cavity mirrors to local equipment of users stations. The mode of control program operation and controlled equipment are determinates by external configuration files. Some results of the system operation are also presented.
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| MOPPH046 |
Operation of Near-infrared FEL at Nihon University
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electron, coupling, linac, klystron |
114 |
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- A. Enomoto, S. Fukuda, K. Furukawa, S. Michizono, S. Ohsawa
KEK, Ibaraki
- Y. Hayakawa, K. Nakao, K. Nogami, T. Tanaka, K. Hayakawa
LEBRA, Funabashi
- M. Inagaki, T. Kuwada, T. Sakai, I. Sato
Nihon University
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The near-infrared FEL at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University has been operated for a variety of scientific applications since 2003. The stability of the FEL power was improved appreciably by the advanced stability of the 125 MeV electron linac. Currently fundamental FEL wavelength ranges from 1 to 6 microns, which is restricted by the electron energy and the optical devices. The higher harmonics in the visible region is also available. The maximum macropulse output energy of 60 mJ/pulse has been obtained at a wavelength of 1725 nm. The short FEL resonator at LEBRA causes relatively high optical energy density on the surface of the resonator mirrors; present copper-based Ag mirrors in use at LEBRA are not durable enough for long term operation. As an alternative way of generating intense harmonics in the visible to near-UV region, second and third harmonic generation by means of non-linear optical devices has been tested for the FELs around 1.5 microns as input fundamental photons.
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| MOPPH050 |
Status of the Undulator System of the Seeded HGHG-FEL Test Bench at MAX-lab
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electron, radiation, simulation, laser |
122 |
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| MOPPH051 |
Nonlinear Harmonic Generation in the BESSY Soft X-Ray FEL
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radiation, electron, simulation, laser |
126 |
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- K. Goldammer
BESSY GmbH, Berlin
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Free Electron Lasers do not only radiate at the fundamental frequency, they may also radiate coherently at higher harmonics. This process is referred to as nonlinear harmonic generation or NHG. NHG is of high interest, because it extends the FEL output wavelength of FELs to several harmonics of the FEL resonant frequency. In cascaded High Gain Harmonic Generation (HGHG) FELs, harmonic radiation may be used to improve frequency-conversion and reduce the number of HGHG-stages. BESSY proposes to build a cascaded HGHG FEL with three FEL lines. They cover a wavelength range of 51 nm (Low-Energy FEL) to 1.2 nm (High-Energy FEL) and consist of up to four HGHG-stages. In this paper, we present studies of the BESSY High-Energy FEL harmonic content performed with the upgraded version of the simulation code Genesis 1.3.
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| MOPPH052 |
Output Performance of the STARS HGHG Demonstrator at BESSY
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radiation, emittance, laser, electron |
130 |
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- K. Goldammer, A. Meseck, B. C. Kuske
BESSY GmbH, Berlin
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BESSY is planning to construct a free-electron laser facility (STARS) to demonstrate cascaded high-gain harmonic generation (HGHG) FELs. A 325MeV superconducting linear accelerator will drive two HGHG-stages, where the second stage is seeded by the radiation from the first stage. Such a cascading of the HGHG scheme, originally pioneered by L. H. Yu, allows a reduction of the STARS output wavelength down to the few 10nm range. This paper describes the expected performance of the facility, the achievable wavelength range, the harmonic content of the radiation, the potential of super-radiant pulses and first considerations about the stability of the source.
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| MOPPH054 |
Small-Aperture Vacuum-Chamber Design for STARS
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electron, vacuum, scattering, radiation |
134 |
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- J. Bahrdt, V. Duerr, M. Scheer, G. Wuestefeld, A. Meseck
BESSY GmbH, Berlin
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To demonstrate and investigate the cascaded HGHG-scheme proposed for the BESSY Soft X-ray FEL, BESSY plans to build a test-facility called STARS consisting of two HGHG stages. The radiator in the second stage is planned as an APPLE III device which provides the highest field for a circular beam pipe. The minimum Gap of 7 mm translates into a 5 mm inner diameter of the vacuum chamber. An analysis of the impact of the wakefields and the expected vacuum profile is thus required. Results of this analysis an vacuum measurements are presented.
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| MOPPH058 |
Status of the SPARX Project
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emittance, linac, radiation, simulation |
142 |
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- D. Filippetto
INFN/LNF, Frascati (Roma)
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The SPARX project consists in an Soft-X-ray-FEL facility jointly supported by MUR(Research Department of Italian Government), Regione Lazio, CNR, ENEA, INFN and the University of Roma Tor Vergata. It is the natural extension of the ongoing activities of the SPARC collaboration. The aim is the generation of electron beams characterized by ultra-high peak brightness at the energy of 1 and 2 GeV, for the first and the second phase respectively. The beam is expected to drive a single pass FEL experiment in the range of 13.5-6 nm and 6-1.5 nm, at 1 GeV and 2 GeV respectively, both in SASE and SEEDED FEL configurations. A hybrid scheme of RF and magnetic compression will be adopted, based on the expertise achieved at the SPARC. high brightness photoinjector presently under commissioning at Frascati INFN-LNF Laboratory.
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| MOPPH061 |
Design of the PAL Test FEL Machine
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linac, emittance, simulation, electron |
149 |
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- J. Choi, J. Y. Huang, H.-S. Kang, I. S. Ko, T.-Y. Lee, J.-S. Oh, S. J. Park, M. Kim
PAL, Pohang, Kyungbuk
- C. M. Yim
POSTECH, Pohang, Kyungbuk
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In a road to the PAL-XFEL, the 1st stage will be to build a test machine, whose design parameters are presented here. It will be a 230 MeV machine that has the target wavelength of visible range. The design details and simulation results are shown in this paper.
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| MOPPH062 |
Features of the PAL-XFEL Design
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electron, radiation, emittance, brightness |
152 |
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| MOPPH064 |
A Project of SC ERL at KAERI
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sextupole, electron, emittance, dipole |
160 |
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- Y. H. Han, Y. U. Jeong, B. C. Lee, S. H. Park
KAERI, Daejon
- S. V. Miginsky, A. V. Bondarenko
BINP SB RAS, Novosibirsk
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A project of an ERL at Korea Atomic Energy Research Institute is described. The ERL will be connected to the existing machine without any modification. It consists of two 180° bents and two straight sections: one is for an FEL, another for a Compton X-ray source. One can choose the regime controlling the lenses. The total ERL is isochronous to avoid any problem with longitudinal beam instability. It will be possible to control both Sx and Sy transormation matrix elements independently to suppress longitudinal beam instability and allow the increase of beam current. Sextuples will be installed in bents to suppress chromatic aberration. This design provides operation in FEL regime with high electron efficiency in the range of electron energies 12–22 MeV.
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| MOPPH068 |
The NCAS-FEL: an FEL Oscillator with High Slippage
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electron, radiation, simulation, laser |
163 |
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- K.-J. Boller, E. van Geijin
Mesa+, Enschede
- J. Jalink, W. J. van der Zande
Radboud University Nijmegen, Institute of Molecules and Materials, Nijmegen
- P. J.M. van der Slot
Twente University, Laser Physics and Non-Linear Optics Group, Enschede
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In normal operation of FEL oscillators with little or no slippage, the cavity length needs to be slightly smaller than the synchronous value due to the lethargy in the gain build-up. If the FEL experiences high slippage, i.e., when the slippage becomes comparable or even larger than the length of the electron pulse, a different cavity detuning may be required. We use the one dimensional Medusa1D code to study the NCAS-FEL* as an example of an FEL oscillator having high slippage. Medusa1d is basically equal to the fully three dimensional Medusa code** with the 3D effects stripped out. It includes multiple wiggler segments, electron beam transport elements, harmonics and a simple oscillator model. Medusa1D can also include 3D effects using the fitting formula of Xie***. The NCAS-FEL is a RF-linac based FEL dedicated for high resolution spectroscopic studies in the wavelength range from 100 micron to 1.5 mm. The design of the NCAS-FEL is currently under way, and we report here initial results of this design and focus on the effects of high slippage on cavity detuning and the development of coherence within the optical pulse.
* Proceedings of FEL 2006, Berlin, Germany (2006) p485 - 487 ** Phys. Rev. ST-AB 8, 110701 (2005)*** Nucl. Instrum. Methods Phys. Res., Sect. A 445, 59 (2000)
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| MOPPH074 |
Preliminary Design of the Proposed IR-FEL in India
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electron, simulation, radiation, linac |
179 |
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| MOCAU01 |
Short Wavelength Regenerative Amplifier FELs
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feedback, simulation, electron, radiation |
182 |
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- D. J. Dunning, N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
- B. W.J. McNeil
USTRAT/SUPA, Glasgow
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In this paper we discuss the possibility of extending the operating wavelength range of tunable Regenerative Amplifier FELs to shorter wavelengths than current design proposals, notably into the XUV regions of the spectrum and beyond where the reflectivity of broadband optics is very low. Simulation studies are presented which demonstrate the development of good temporal coherence in generic systems with a broadband radiation feedback of less than one part in ten thousand.
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Slides
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| MOCAU02 |
Numerical Solution of the FEL Correlation Function Equation
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electron, radiation, simulation |
188 |
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- N. Vinokurov, O. A. Shevchenko
BINP SB RAS, Novosibirsk
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The equation for two-particle correlation function in FEL was derived recently to provide a new way of noise calculations in FELs*. In this paper this equation is solved numerically for the simplest case of narrow electron beam. Time independent solution with saturation is obtained. It is compared with the results of quasilinear theory and results of previous SASE linewidth estimates.
* O. A. Shevchenko, N. A. Vinokurov, NIM A507 (2003) 84-88
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Slides
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| MOCAU04 |
Impact of Longitudinal Space-charge Wake from FEL Undulators on Current-enhanced SASE Schemes
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impedance, space-charge, radiation, electron |
196 |
| |
- E. Saldin, E. Schneidmiller, M. V. Yurkov, G. Geloni
DESY, Hamburg
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In this article we present a description of longitudinal wake fields in X-ray Free-Electron Lasers (XFELs) that is of relevance in relation with Enhanced Self-Amplified Spontaneous Emission (ESASE) schemes. We consider wakes in XFELs, in the limit when the electron beam has gone inside the undulator for a distance longer than the overtaking length (the length that electrons travel as a light signal from the tail of the bunch overtakes the head of the bunch). We find that the magnitude of the resulting energy chirp constitutes a reason of concern for the practical realization of ESASE schemes.
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Slides
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| TUAAU02 |
Electron Outcoupling Scheme for the Novosibirsk FEL
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electron, radiation, bunching, simulation |
204 |
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- O. A. Shevchenko, V. G. Tcheskidov, N. Vinokurov, A. N. Matveenko
BINP SB RAS, Novosibirsk
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One of the main problems of contemporary high power FELs is the mirror heating. One of the possible solutions of this problem is the use of electron outcoupling*. In this case the mirrors of optical resonator are not transparent and the coherent radiation from an additional undulator in the FEL magnetic system is used. To provide the output of this radiation the electron beam in the auxiliary undulator is deflected from the optical resonator axis. To save bunching it is preferable to use the achromatic deflecting bend. The project of electron outcoupling for the Novosibirsk FEL is described. Simulation results are presented.
* N. G. Gavrilov et al., NIM A304 (1991) 63-65
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Slides
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| TUAAU05 |
Modelling Mirror Aberrations in FEL Oscillators Using OPC
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laser, simulation, free-electron-laser, radiation |
207 |
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- K.-J. Boller, J. G. Karssenberg, P. J.M. van der Slot
Mesa+, Enschede
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Thermal distortion in mirrors used in high average power FEL oscillators, like the JLAB FEL and the 4GLS VUV-FEL, will influence the mode quality and affect the FEL performance. In order to quantify these effects, these distortions needs to be characterised. Mirror aberrations are generally described using Zernike polynomials and also in case of thermal distortions, it has been shown that these polynomials can be used to describe the mirror distortion*. The Optical Propagation Code (OPC)** is a general optical propagation package in the paraxial approximation, that works together with gain codes like Medusa and Genesis 1.3 to model FEL oscillators. We have extended OPC to include phase masks, that can either be generated by an external program or internally using Zernike polynomials. This allows OPC to model mirror aberrations. We will present a few examples, illustrating the capabilities of OPC.
* Nucl. Instrum. Meth. A407 (1998)401** J. Appl. Phys. 100, 093106 (2006)
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Slides
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| TUBAU02 |
Status of SCSS & X-ray FEL Project in Japan
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emittance, electron, gun, cathode |
216 |
| |
- T. Shintake
RIKEN Spring-8 Harima, Hyogo
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Staus of SCSS project after the first lasing last year will be reported. The X-ray FEL, which uses 8 GeV C-band, is under construction, whose status will be reported.
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Slides
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| TUPPH011 |
Analytical Studies of Transverse Coherence Properties of X-ray FELs
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radiation, electron, emittance, free-electron-laser |
240 |
| |
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| TUPPH012 |
Compact X-ray Free-Electron-Laser Based on an Optical Undulator
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laser, radiation, electron, emittance |
244 |
| |
- A. Bacci, C. Maroli, A. R. Rossi, L. Serafini
INFN-Milano, Milano
- V. Petrillo
Universita' degli Studi di Milano, Milano
- P. Tomassini
INFN-Pisa, Pisa
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The interaction between a very high brightness electron beam and a relativistically intense optical laser pulse produces X rays via coherent Thomson back scattering with FEL collective amplification. The phenomenon is, however, very selective, so that the characteristics of both electron and laser beam must satisfy tight requirements in terms of beam current, emittance, energy spread and laser amplitude stability within the pulse. The three-dimensional equations governing the radiation phenomena have been studied in both linear and non linear regime and solved numerically for the particularly interesting values of wavelengths of 1 Ang, 1 nm and 12 nm. The performance of the collective Thomson source has been compared with that of an equivalent static undulator. A set of scaling laws ruling the phenomenon is also presented. The possibility of using an electron beam produced via LWFA in the bubble regime is investigated.
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| TUPPH013 |
Production of Ultra-short Radiation Pulses in Frequency Doubler
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electron, radiation, laser, simulation |
248 |
| |
- E. Schneidmiller, M. V. Yurkov, E. Saldin
DESY, Hamburg
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Typically beam formation system of driver linac for SASE FEL produces electron beams with small local energy spread. This feature opens up extra possibilities for implementation of different FEL schemes. One of them is an effective frequency doubler*. It consists of an undulator tuned to the fundamental harmonic, dispersion section, and undulator tuned to the second harmonic. The first stage is a conventional soft X-ray SASE FEL. Its gain is controlled in such a way that the maximum energy modulation of the electron beam at the XFEL exit is about equal to the local energy spread, but still far away from saturation. When electron bunch passes through dispersion section this energy modulation leads to effective compression of the particles. Then bunched electron beam enters the 2nd harmonic undulator, and produces the radiation at the 2nd harmonic. Recently SASE FEL FLASH in Hamburg demonstrated unique mode of operation generating sub-10-fs radiation pulses**. In this paper we study an option of frequency doubler for FLASH operating in the femtosecond mode of operation.
* J. Feldhaus et al., NIM A 528 (2004) 471.** W. Ackermann et al., "Operation of a free electron laser from the extreme ultraviolet to the water window", Nature Photonics, in press.
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| TUPPH014 |
Generation of X-ray FEL Light Using Laser Wakefield Accelerated Electron Beams
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electron, laser, radiation, simulation |
252 |
| |
- A. Rousse, K. Ta Phuoc
LOA, Palaiseau
- N. Vinokurov, O. A. Shevchenko
BINP SB RAS, Novosibirsk
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We consider a new class of high gain FELs based on femtosecond electron bunches with extra high current density produced by Laser Wake Field Acceleration (LWFA). The FELs of this kind can be used for generation of high power femtosecond x-ray pulses. We present the results of simulations of FEL operation with some reasonable beam parameters which will be obtained in future. We focus our attention on the advantages which can be gained from the unique possibility of the use of femtosecond hundred-kiloamperes bunches, generated by LWFA. We also consider the impact of the relatively poor electron beam properties on FEL characteristics.
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| WEAAU05 |
A Compact Electron Spectrometer for an LWFA
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electron, laser, radiation, plasma |
294 |
| |
- R. A. Crowell, K.-J. Kim, A. H. Lumpkin
ANL, Argonne, Illinois
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The use of a laser wakefield accelerator (LWFA) beam as a driver for a compact Free-Electron Laser (FEL) has been proposed recently. A project is underway at Argonnne National Laboratory (ANL) to operate an LWFA in the bubble regime and to use the quasi-monoenergetic electron beam as a driver for a 3-m long undulator for generation of sub-ps UV radiation. The Terawatt Ultrafast High Field Facility (TUHFF) in the Chemistry division provides the 20 TW peak power laser. Towards this goal, a compact electron spectrometer whose initial fields of 0.45 T provide energy coverage of 30-200 MeV has been selected to characterize the electron beams. The system is based on the Ecole Polytechnique design* used for their LWFA and incorporates the 5-cm long permanent magnet dipole, the LANEX scintillator screen located at the dispersive plane, a Roper Scientific 16-bit MCP-intensified CCD camera, and a Bergoz ICT for complementary charge measurements. Test results on the magnets, the 16-bit camera, and the ICT will be described, and initial electron beam data will be presented as available.
*Y. Glinnec et al., "Broadrange Single Shot Electron Spectrometer", Report dated July 6, 2006, Ecole Polytechnique.
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Slides
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| WEBAU03 |
Performance Tests of the Photon Monochromator for Self-seeding at FLASH
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photon, electron, radiation, vacuum |
306 |
| |
- H. K. Bechtold, J. Hartvig, H. Juul, V. Toft
Aarhus University, Aarhus
- R. Follath, G. Reichardt, F. Senf, F. Siewert
BESSY GmbH, Berlin
- U. Hahn, J. Viefhaus, R. Treusch
DESY, Hamburg
- S. V. Hoffmann
ISA, Aarhus
- Ch. Knoechel
LBNL, Berkeley, California
- R. Reininger
UW-Madison/SRC, Madison, Wisconsin
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A single pass FEL amplifier can produce extremely intense and fully coherent radiation at short wavelengths if it is seeded by a coherent light beam resonant with the magnetic structure and collinear with the electron beam. Since at the present time a single pass SASE FEL is the only source of sufficiently intense, tunable radiation in the soft X-ray region, it has been proposed to use such a source in combination with a narrow-band monochromator for seeding an FEL amplifier*. By means of such a "Self-Seeding", the soft X-ray free electron laser FLASH at DESY will be modified so that it can provide coherent radiation in space and time in a wavelength range from about 60-6nm (~20-200eV). In this presentation, we will focus on the performance of the photon monochromator beamline which was setup and tested at the synchrotron radiation storage ring ASTRID in Aarhus, Denmark. The optical, mechanical and vacuum design will be described along with results on the resolving power of the monochromator which have been obtained scanning across rare gas resonance lines at various energies. Based on these results we will conclude that the monochromator is mechanically very stable and reproducible and behaves according to its specifications with resolving powers between 10000 and 20000, i.e. bandwidths of a few meV only.
* J. Feldhaus, E. L. Saldin, J. R. Schneider, E. A. Schneidmiller, and M. V. Yurkov, Opt. Commun. 140, 341 (1997)
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Slides
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| WEBAU05 |
Magnetic Measurements, Tuning and Fiducialization of LCLS Undulators at SLAC
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alignment, background, linac, quadrupole |
314 |
| |
- V. Kaplounenko, A. W. Weidemann, Z. R. Wolf, Yu. I. Levashov
SLAC, Menlo Park, California
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A new Magnetic Measurement Facility (MMF) has been built at Stanford Linear Accelerator Center (SLAC) to measure, tune and fiducialize undulators for Linac Coherent Light Source (LCLS) project. Climate controlled MMF utilizes two magnetic measurement benches and a large Coordinate Measurement Machine (CMM) and provides a throughput of one undulator segment a week. Magnetic measurement, tuning and fiducialization process is being presented and first tuning results are discussed.
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Slides
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| WEPPH003 |
Magnetic Measurements of the FLASH Infrared Undulator
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simulation, radiation, electron, power-supply |
318 |
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- A. Chesnov, E. A. Matushevsky, D. Petrov, E. Syresin, N. A. Morozov
JINR, Dubna, Moscow Region
- O. Grimm, Y. Holler
DESY, Hamburg
- J. Rossbach
Uni HH, Hamburg
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The FLASH free-electron laser at DESY, Hamburg, will be equipped with an infrared electromagnetic undulator during the current shut-down, providing radiation in the range 1-200 um. It will be used both for electron beam diagnostics purposes and as a powerful source synchronized to the VUV and soft X-ray pulses of the FEL. The undulator was constructed at the Joint Institute of Nuclear Research (JINR). This paper summarizes the extensive magnetic measurements that where performed both at JINR and DESY prior to installation of the undulator.
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| WEPPH004 |
Numerical Calculations of the Radiation Emitted from the FLASH Infrared Undulator
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radiation, photon, synchrotron, synchrotron-radiation |
322 |
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- V. Kocharyan, J. Rossbach, O. Grimm
DESY, Hamburg
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The results from the magnetic measurements with the FLASH infrared electromagnetic undulator reported in a companion paper where used as input for calculations of the expected radiation spectrum. Especially the behaviour of the device at small first harmonic wavelengths, i.e. small excitation currents, is important for beam diagnostics, as here the high intensity in a narrow band is a distinct advantage over broad-band sources to detect small bunch structures. The field quality is reduced at small currents due to imperfections in the yoke construction and limited compensation by correction windings. A determination of the lower limit for useful operation of the device follows from these calculations.
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| WEPPH005 |
Magnet Sorting for the European XFEL Hybrid Undulator - Comparing Study
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electron, controls, free-electron-laser, laser |
326 |
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- B. Faatz, J. Pflueger, Y. Li
DESY, Hamburg
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Current permanent magnet material quality is insufficient to obtain field qualities in undulators, which satisfy FEL requirements. Therefore position and orientation of magnets have to be carefully chosen in order to obtain mutual cancellation of field errors. In this paper we compare two different sorting schemes, simulated annealing and a straight forward paring method. They are applied to a 5m prototype structure built for the European XFEL facility. The algorithms of these two methods are described in detail and the sorting results and the expected field qualities are carefully compared.
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| WEPPH006 |
Study of Undulator Deformation Tolerance for the European XFEL
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simulation, radiation, electron, photon |
330 |
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- B. Faatz, J. Pflueger, Y. Li
DESY, Hamburg
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The undulators for the European XFEL use NdFeB type permanent magnets. Even for perfect magnet material, the undulator quality degrades due to mechanical limitations, such as girder deformation, and temperature variation. Since the beam orbit can always be corrected, the main effect will be a variation in slippage between electrons and photon beam along the undulator. A careful estimation of the error budget is needed to avoid cost driving hardware efforts. We modeled deformation, gap variation and temperature error and used GENESIS to simulate the effect on the performance of the European XFEL.
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| WEPPH007 |
MCP-based Photon Detector with Extended Wavelength Range for FLASH
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radiation, target, photon, background |
334 |
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- O. I. Brovko, D. Kharlamov, E. A. Matyushevskiy, A. V. Shabunov
JINR/LHE, Moscow
- J. Feldhaus, U. Hahn, M. Hesse, U. Jastrow, V. Kocharyan, P. Radcliffe, E. Saldin, E. Schneidmiller, K. I. Tiedtke, R. Treusch, M. V. Yurkov, N. von Bargen, L. Bittner
DESY, Hamburg
- V. I. Lokhmatov, E. Syresin
JINR, Dubna, Moscow Region
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Experimental experience gained at the extreme ultraviolet SASE FEL FLASH (DESY, Hamburg) has shown that successful operation of the facility strongly depends on the quality of the radiation detectors. Here key issues are: wide wavelength range (6 to 100 nm for FLASH), wide dynamic range (from the level of spontaneous emission to the saturation level), and high relative accuracy of measurements which is crucial for detection of a signature of amplification and characterization of statistical properties of the radiation. In this report we describe MCP-based radiation detector for FLASH which meets these requirements. Key element of the detector is wide dynamic range micro-channel plate (MCP) which detects scattered radiation from a target. With five different targets and MCPs in combination with optical attenuators present detector covers operating wavelength range from 6 to 100 nm, and dynamic range of the radiation intensities, from the level of spontaneous emission up to the saturation level of SASE FEL.
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| WEPPH008 |
Measurements of Projected Emittances at FLASH
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emittance, electron, linac, lattice |
338 |
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- F. Loehl, E. Prat
DESY, Hamburg
- K. Honkavaara
Uni HH, Hamburg
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FLASH is a SASE FEL user facility at DESY (Hamburg) operating with photon wavelengths in the range from vacuum ultraviolet to soft x-rays. Although the slice emittance is a more appropriate parameter to characterize the SASE process, the projected emittance provides a useful measure of the electron beam quality. At FLASH the projected emittance is measured at three location along the linac: in the injector (130 MeV), after the collimator (full electron beam energy), and in the undulator section. The transverse beam shape is measured with OTR monitors and wire scanners. The multi-monitor method is used to determine the emittance. In this paper we describe the measurement set-up and procedure and report recent results and planned upgrades.
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| WEPPH015 |
Modeling of a Laser Heater for Fermi@Elettra
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laser, electron, linac, emittance |
362 |
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| WEPPH019 |
Determination of the Wakefield Budget for the FERMI FEL Undulator System
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vacuum, impedance, electron, coupling |
374 |
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- C. Bontoiu, P. Craievich, L. Rumiz
ELETTRA, Basovizza, Trieste
- M. Castronovo
Università degli Studi di Trieste, Trieste
- R. Vescovo, A. A.G. Lutman
DEEI, Trieste
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The FERMI project aims to achieve very high-brightness photon beam pulses of minimum bandwidth. These goals can be marred by the presence of large wakefields generated along the length of the undulator small-gap vacuum chamber. Estimations of the induced energy-spread caused by the resistive wall and surface roughness wakefields along the length of the vacuum chamber of the FERMI FEL undulator are presented. The energy spread and losses induced by the resistive wall wakefield are determined for three possible transverse geometries of the vacuum chamber, namely circular, rectangular and elliptical cross-section, while the energy spread and losses induced by the surface roughness wakefields are obtained for the circular cross-section case. In this last case in-house surface profile measurements are used to provide realistic estimates.
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| WEPPH021 |
Wide Band Seeding and Wavelength Compression
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laser, electron, radiation, cathode |
378 |
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- T. Shintake
RIKEN Spring-8 Harima, Hyogo
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Seeding with optical laser and compressing wavelength in chicane bunch compressor has been studied theoretically. Overlapping laser beam with in comming electron beam in free space, with oblique crossing, we may apply energy modulation on relativisitic electron beam. When we use forth harmonic YAG-laser, 255 nm, and compressing 20 times, we have 13 nm density modulation period. Passing in undulator, which resonates to the compressed wavelength, the super-radiation mode beam will be generated. In contrast with SASE-FEL, this type of radiation source does not require high quality beam, ease to operate and coherent.
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| WEPPH024 |
Numerical Evaluation of Oscillator FEL with Multi-Bunch Photo-Cathode RF-gun in Kyoto University
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electron, gun, laser, emittance |
390 |
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- Y. Kamiya, M. Washio
RISE, Tokyo
- T. Kii, K. Masuda, S. Sasaki, T. Shiiyama, H. Zen, H. Ohgaki
Kyoto IAE, Kyoto
- M. Kuriki, N. Terunuma, J. Urakawa
KEK, Ibaraki
- R. Kuroda
AIST, Tsukuba, Ibaraki
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An infrared FEL (4-13 micro-m) facility to develop new energy materials is constructed in Institute of Advanced Energy, Kyoto University. The electron beam of 40 MeV has been successfully accelerated by a linac system which consists of a 4.5-cell thermionic RF gun*. However, due to severe back-bombardment effect, there still needs several efforts to extend the macro-pulse duration to obtain a stable FEL. Upgrade from the present thermionic RF gun to a photocathode RF gun has been planned in KU-FEL**, because a photocathode RF gun is free from the back-bombardment and can generate a high brightness electron beam. A multi-bunch photo-cathode RF gun system has been developed*** and will be installed into the KU-FEL linac. Thus a design work on the new linac system from the gun to the FEL has been performed by using PARMELA and GENESIS. The evaluated peak current is about 4 times and the expected FEL gain is about 10 times as high as those with the present system. The required laser system will be discussed in this conference, as well.
* H. Ohgaki, et al., NIM A, vol.528, pp.366-370 (2004).** H. Ohgaki, et al., Proc. of the FEL 2004, pp.454-457 (2004).*** K. Hirano, et al., NIM A, vol. 560, pp.233-239 (2006).
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| WEPPH025 |
Progress in the FEL Lasing in Kyoto University
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electron, cathode, gun, alignment |
394 |
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- T. Kii, K. Masuda, H. Ohgaki, T. Shiiyama, H. Zen, S. Sasaki
Kyoto IAE, Kyoto
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We have constructed an infrared (4～13μm) FEL facility for advanced energy researches in Kyoto University. The numerical studies on the expected FEL gain, which was based on the experimental measurements both of the undulator and of the electron beam parameters, were carried out*. However, g-parameter of the mirror cavity was located close to the unstable region. In order to obtain a stable FEL, we calculated the FEL gain taking into account the duct shape, the tilt angle, and the offset of the mirror, then for the first lasing the mirror parameter was optimized. At the present stage, we have installed the undulator and the mirror cavity. A spectrum of the spontaneous emission was measured, which was consistent with the result of spectrum calculation obtained with measured magnetic field of the undulator. In this conference, we will present the result of the mirror optimization, and measurement of the spontaneous emission. The status of the experiment on FEL lasing will also be addressed.
* M. Nakano, et al., Proceedings of the 2006 FEL conference, (2006)
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| WEPPH027 |
Beam Diagnostics for the First Lasing of the KU-FEL
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gun, electron, emittance, simulation |
402 |
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- T. Kii, K. Masuda, H. Ohgaki, S. Sasaki, T. Shiiyama, H. Zen
Kyoto IAE, Kyoto
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Mid-IR FEL (4-13μm) device for energy science has been constructed in Institute of Advanced Energy, Kyoto University and the electron beam of 40MeV has been successfully accelerated*. The transverse phase space distribution and the corresponding emittance of the electron beam were measured by using a tomographic method**. As the result, normalized emittance was around 3 pi mm mrad. An FEL gain calculation*** shows that the peak current of 10A is the minimum value for the FEL amplification, and that of 40A is required to achieve the FEL saturation. Therefore the bunch compression experiment has been carried out to shorten the micro-bunch length by 2 ps in KU-FEL. The 180 deg. arc section was used for the bunch compression. We will report the result of the emittance measurement and of the bunch compression experiment in the conference.
* H. Ohgaki, et al., NIM A, vol.528, pp.366-370 (2004).** H. Zen, et al., Proc. of the FEL 2006, pp.592-595(2006)*** M. Nakano, et al., Proc. of the FEL 2006, pp.660-664 (2006).
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| WEPPH039 |
The Optical Replica Synthesizer in FLASH
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laser, electron, simulation, vacuum |
438 |
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- G. Angelova, V. G. Ziemann
UU/ISV, Uppsala
- J. Boedewadt, S. Khan, A. Winter
Uni HH, Hamburg
- A. Meseck
BESSY GmbH, Berlin
- E. Saldin, H. Schlarb, B. Schmidt, E. Schneidmiller, M. V. Yurkov
DESY, Hamburg
- P. M. Salen, P. van der Meulen
FYSIKUM, AlbaNova, Stockholm University, Stockholm
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During the shutdown in spring 2007 the optical replica synthesizer, a novel device to diagnose ultra-short electron bunches, is assembled in the FLASH accelerator. We report on the status of the construction work with emphasis on the two electro-magnetic undulators needed for micro-bunching and replica-pulse generation.
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| WEPPH041 |
7th Harmonic Buncher Experiment at Neptune Laboratory
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laser, electron, coupling, bunching |
441 |
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- R. Tikhoplav, S. Tochitsky, P. Musumeci
UCLA, Los Angeles, California
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Since typically FEL undulator magnets have period length in the cm range, and the normalized magnetic field strength K is maintained close to unity to guarantee a good coupling, a very high energy electron beam is needed to access the far UV and x-ray region of the electromagnetic spectrum. One way to reduce the beam energy necessary for short wavelength light sources consists of exploiting the FEL harmonic interaction. An experiment aimed at demonstrating the efficiency of harmonically coupled schemes is proposed for the Neptune Laboratory at UCLA. We plan to inject the 12.4 MeV beam from the split photoinjector in an already available undulator with period = 3.3 cm and K = 1.8. The FEL resonant wavelength with these parameters is 74.2 um. A copropagating high power 10.6 um CO2 laser bunches the beam via 7th harmonic FEL/IFEL interaction. Preliminary calculations show that even though the interaction is weakened by the high harmonic number, it is required to use only 5 -10 MW of power in order to induce full bunching on the beam in the 10 period long undulator.
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| WEPPH049 |
Test of a Wiresanner in the Diagnostic Section of PITZ
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electron, diagnostics, cathode, background |
461 |
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- G. Asova, J. W. Baehr, J. H. Han, S. Khodyachykh, S. A. Korepanov, M. Krasilnikov, V. Miltchev, A. Oppelt, B. Petrosyan, M. Sachwitz, L. Staykov, F. Stephan, H.-J. Grabosch
DESY Zeuthen, Zeuthen
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The Photo Injector Test facility at Zeuthen (PITZ) has been established to optimize electron beams of high brilliance needed for short wavelength FELs. In a first step one wire scanner station, developed and used in the undulator section of FLASH at DESY, was tested in the diagnostic section of PITZ. Measurements of the beam-profile and the beam-position were performed to test the useability of such type of wire scanner at PITZ. The obtained results are presented and discussed. The test has shown that wire scanners of this type can be used successfully as complementary measurement device for beam-profile measurements at PITZ. In the final state of extension of PITZ , two wire scanners are foreseen as standard diagnostic tools.
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| WEPPH052 |
In-situ Undulator Field Measurement with the SAFALI System
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laser, feedback, vacuum, electron |
468 |
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- H. Kitamura, T. Tanaka
RIKEN Spring-8 Harima, Hyogo
- T. Seike
JASRI/SPring-8, Hyogo-ken
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Although the in-vacuum undulators (IVUs) have many advantages over out-vacuum undulators, magnetic measurement after assembling vacuum components, i.e., final verification of magnetic performance, is not an easy task. In addition, remeasurement after installation in the accelerator beamline is not trivial. The situation is more severe for cryogenic permanent magnet undulators (CPMUs), an extension of IVUs. We have recently developed a magnetic measurement system to measure the field inside the vacuum chamber. With optical laser beams introduced into the vacuum chamber, the alignment of the Hall probe positions is dynamically carried out, which ensures a high stability and accuracy of the measurement. This system is called SAFALI for Self-Aligned Field Analyzer with Laser Instrumentation. The SAFALI system has been applied to field measurement of two different undulators. One is an IVU installed in Swiss Light Source in 2001 and had been operated for about 3 years. The other is a CPMU prototype to demonstrate the principle of CPMU. The purpose of the measurement of the former is to investigate the radiation damage during operation, while that of the latter is to check the performance variation according to the temperature change of magnets. In the conference, details of the SAFALI system are given together with the results of the field measurements.
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| WEPPH054 |
Coherent THz Light Source Using Very Short Electron Bunches from a Thermionic RF Gun
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gun, electron, radiation, simulation |
476 |
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- K. Akiyama, H. Hama, F. Hinode, K. Kasamsook, M. Kawai, K. Nanbu, T. Tanaka, M. Yasuda, T. Muto
Tohoku University, School of Scinece, Sendai
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To develop a narrowband coherent Terahertz (THz) light source, a project for producing very short electron bunch has been progressed at Laboratory of Nuclear Science, Tohoku University. Coherent synchrotron radiation is another promising source for generation of high-power THz light. Passing through a conventional undulator with a field period length of ~ 10 cm, the very short electron bunch at the energy around 15 MeV can produce coherent THz radiation. The electron beams of which the bunch length is less than 100 femto-second will be generated by a combined injector system of a thermionic RF gun and a bunch compressor. We have developed an independently-tunable-cells (ITC) RF gun consisted with two uncoupled cavities in order to manipulate the longitudinal phase space. It was found out that the ITC-RF gun is possibly quite suitable to produce such a very short bunch employing a magnetic bunch compressor. In theoretical investigation at the moment, a bunch length of less than 50 fs has been achieved in the numerical tracking simulation. Employing Lienard-Weichert potential, we have performed a 3-D simulation of the coherent THz radiation. The paper will describes the latest status of development of the ITC RF gun and tracking simulations for the bunch compressor as well. Characteristics of the coherent THz radiation resulted from the simulation will be also reported
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| FRAAU01 |
Source of Radiation on ARC-EN-CIEL Proposal
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radiation, electron, laser, cryogenics |
505 |
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- O. V. Chubar, M. Labat, G. Lambert, O. Marcouillé, M.-E. Couprie
SOLEIL, Gif-sur-Yvette
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The ARC-EN-CIEL project proposes a panoply of light sources for the scientific community. The phase 1 (220 MeV superconducting Linac, down to 30 nm) and phase 2 (1 GeV, down to 1 nm) choice to provide 30-100 fs HGHG radiation and their Non Linear Harmonics seeded with the High order Harmonics generated in Gas is further confirmed with the suceesfull demonstration experiment of such a scheme at SPA. New optimizations of the undulatros lead to in vacuum undulators of period 26 mm for the modulator, and APPLE-type radiators of period 30 mm, close to the standard SOLEIL insertion devices. New calculations have been carried out using PERSEO TD and GENESIS coupled to SRW for further propagation of the FEL wavefront to the beamlines. In addition, THz radiation from the magnets of the compression chicanes will be provided and has been calculated using SRW. ARC-EN-CIEL Phase 3 incorporates ERL loops, for hard X ray spontaneous emission above 10 keV from short period in vacuum undulators (20 mm period typically), one Soft-X ray spontaneous emission beamline using an variable polarisation undulator, and an FEL oscillator in the 10-60 nm spectral range. Recent calculations and optimisations will be presented.
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Slides
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| FRAAU03 |
Compact Ring FEL as a Source of High Power Infrared Radiation
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radiation, electron, bunching, simulation |
517 |
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- A. N. Matveenko, N. Vinokurov, O. A. Shevchenko
BINP SB RAS, Novosibirsk
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Ring FELs* were proposed mainly to improve the quality of radiation of x-ray FELs. Their main advantage is the absence of mirrors. It appears that this advantage is also useful for high power FELs. Another reason to build infrared ring FEL is the proof-of-principle for shorter wavelength FELs. Therefore we considered the scheme of infrared ring FEL which requires ERL with beam energy 50 MeV. Using extensive simulations we developed requirements for electron beam parameters and magnetic system of ring FEL. In spite of rather compact design such FEL may provide more than 10 kW average power.
* N. A. Vinokurov, O. A. Shevchenko, NIM A528 (2004) 491-496
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Slides
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