SLAC, Menlo Park, California
Prize lecture by the winner of the FEL prize 2009 for a significant contribution to the advancement of the field of Free-Electron Laser.
DESY, Hamburg
Recently the free-electron laser facility FLASH at DESY, Germany has been upgraded. An important feature of the update is the increase in electron beam energy from 1 to 1.2 GeV by adding a 7th superconducting accelerating module. Recently, FLASH met the upgrade goal and accelerated the beam just above 1.2 GeV. Shortly after, for the first time, lasing at 4.45 nm with a remarkably improved performance was obtained.
DESY, Hamburg
In Europe, several national FEL projects are in progress, the seeded FEL FERMI@Elettra at Sincrotrone Trieste is expecting first lasing by the end of 2010, and the capacity of the FLASH facility at DESY in Hamburg will be doubled by adding a second, seeded FEL in the next few years. These national FEL centres in Europe are currently preparing the foundation of a consortium called EuroFEL in order to be more efficient and to better coordinate their activities in research and development, training and other areas. This contribution will present the main ideas of EuroFEL and the current status of its preparatory phase.
NPS, Monterey, California
Thirty-four 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.
BNL, Upton, Long Island, New York
In this paper, we present an analytical three-dimensional theory of free electron lasers. Under several assumptions, we arrive at an integral equation similar to earlier work carried out by Ching, Kim and Xie, but using a formulation better suited for the initial value problem of Coherent Electron Cooling. We use this model in later papers to obtain analytical results for gain guiding, as well as to develop a complete model of Coherent Electron Cooling.
BNL, Upton, Long Island, New York
We present analytical results for the one-dimensional dispersion relation for high-gain FELs. Using kappa-n distributions, we obtain analytical relations between the dispersion relations for various order kappa distributions. Since an exact solution exists for the kappa-1 (Lorentzian) distribution, this provides some insight into the number of modes on the way to the Gaussian distribution.
AUT, Tehran
Three-Dimensional simulation of Free-Electron Laser amplifiers at the presence of helical wiggler and ion-channel has been reported. The electromagnetic field is assumed to express in terms of the TE modes of a cylindrical waveguide in the absence of the electron beam. The final form of dynamical equations for the evolution of the slowly varying amplitude and wavenumber of TE mode is obtained by substitution of the vector potentials in to Maxwell’s equations. A cold, uniform, axisymmetric electron beam with a flat-top density profile has been considered for modeling the initial injection of the electron beam. The three-dimensional Lorentz force equation in the presence of a realistic helical magnetostatic wiggler, ion-channel electrostatic field and electromagnetic fields describes the electron dynamics. A set of coupled nonlinear first order differential equations is derived and solved numerically by Runge-Kutta method. The 10th-order Gussian quaderature technique is used for calculation of averages in the field equations. Finally, evolution of the radiation power and growth rate of the TE11 mode is shown.
SLAC, Menlo Park, California
UW-Madison/SRC, Madison, Wisconsin
FEL/Duke University, Durham, North Carolina
DEEI, Trieste
A single-pass high-gain x-ray free electron laser (FEL) calls for a high quality electron bunch. In particular, for a seeded FEL amplifier and for a harmonic generation FEL, the electron bunch initial energy profile uniformity and peak current uniformity are crucial for generating an FEL with a narrow bandwidth. After the acceleration, compression, and transportation, the electron bunch energy profile entering the undulator can acquire temporal non-uniformity both in energy and local density. We study the effects of the electron bunch initial energy profile non-uniformity and local density variation on the FEL performance. Intrinsically, for a harmonic generation FEL, the harmonic generation starts with an electron bunch having energy modulation as well as density bunching at the previous stage FEL wavelength and its harmonics. Its effect on the harmonic generation FEL in the radiator is then studied.
Islamic Azad University, Sabzevar Branch, Sabzevar
University of Tehran, Tehran
pnum, Mashhad
PPRC, Tehran
The effects of temperature on the growth rate of a two-stream free electron laser (TSFEL) with planar wiggler magnetic pump have been investigated. The dispersion equation has been derived through the use of continuity, momentum transfer, and Maxwell's equations. In the analysis, only the longitudinal component of the pressure tensor is considered in the electron equation of motion. The characteristics of the dispersion relation along with the growth rate are analyzed numerically. The results show that the growth rate in this system (TSFEL) is relatively higher than the conventional FEL; finally, we compare our results with other cases, like without beam temperature, and conventional FEL.
ELETTRA, Basovizza
CNR - IMIP, Trieste
University of Nova Gorica, Nova Gorica
Università degli Studi di Trieste, Trieste
European XFEL GmbH, Hamburg
The paper will report about the last achievements of the Elettra storage-ring FEL. The latter include: a) a noticeable improvement of the source performance (generation of coherent radiation at 87 nm, attainment of a very good shot-to-shot stability); b) general FEL studies, relevant to single-pass devices (characterization of the angular distribution of harmonic emission, analysis of the frequency pulling effect), and c) first user experiments (pump-probe on gas phase and solid-state samples).
FZD, Dresden
Two free-electron lasers (FELBE; 4-21 μm and 18-250 μm, respectively) have been in routine user operation for a wide range of IR experiments at the radiation source ELBE in the Forschungszentrum Dresden-Rossendorf for several years. The lasers are driven by a superconducting RF linac that permits the generation of a cw-beam with a repetition rate of 13 MHz and a high average beam power. In addition, operation in a macropulse modus (pulse duration >100 μs, repetition rate ≤ 25 Hz) is possible. A few important experiments using the cw-operation are discussed. Furthermore, an outlook is given on the experiments which use the beam of FELBE in the High Magnetic Field Laboratory Dresden (HLD). The HLD provides pulsed magnetic fields up to 60 T. It operates as a user facility since 2007.
JLAB, Newport News, Virginia
ATF, Boulder
Mesa+, Enschede
We report on the design, and broadly tunable operation, of a high average power free-electron laser using edge-outcoupling. For this type of outcoupling, the cavity mode has a larger area than the mirror diameter, and the mode ‘spills” around it. While used in positive branch unstable resonators, in this case, the resonator was in a stable configuration. Using an edge-outcoupler composed of an aluminum-coated sapphire substrate, the IR Upgrade FEL at Jefferson Lab achieved a maximum power of 260W at 3.87 microns, with an output power of 20 W or higher from 0.8 to 4.2 microns. Measurements of gain, loss, and output mode are compared with our models.
SOLEIL, Gif-sur-Yvette
PhLAM/CERCLA, Villeneuve d'Ascq Cedex
LAL, Orsay
University of Erlangen-Nuremberg, Erlangen-Nuremberg
We investigate a dynamical behaviors occurring in single-pass free electron lasers (FELs), depending on the electron beam, undulator and seed laser parameters. We put in evidence a complex spatiotemporal deformation of the amplified pulse, leading ultimately to a pulse splitting effect with two sub-pulses. This phenomenon has been first observed in PERSEO simulations in the case of ARC-EN-CIEL project studies, and then been analyzed more in details with the Colson-Bonifacio FEL equations. This studies reveal that slippage length as well as the seed laser pulse wings are the main ingredients of this dynamics [1]. We show that the splitting results from the nonhomogeneous saturation of the gain by the optical field copropagating with the electron beam.
M.Labat et al. “Pulse-splitting in short wavelength seeded free electron laser,” Phys. Rev. Lett. {10}3, 264801 (2009)
ANL, Argonne
X-ray free electron lasers (FELs) are well suited to pursue a long-standing goal of studying matter in a transient state that is far from equilibrium. This state often determines the functions of materials and, thus, holds a key to understanding how to control them. The natural time scale for most of the dynamic processes involving atoms is of the order of 100 femtoseconds, and existing x-ray FELs have already surpassed this mark. The natural time scale for dynamic processes driven by electrons is of the order of 100 attoseconds, and this is the next Rubicon for FELs. In this talk I will review the state of the art in generation of femtosecond x-ray pulses using FELs and will discuss a number of new ideas en route to sub-femtosecond x-ray pulses.
SLAC, Menlo Park, California
There is a growing interest in the generation and characterization of femtosecond and sub-femtosecond pulses from linac-based free-electron lasers (FELs). In this paper we study a simple longitudinal transformation* for measuring a very short electron bunch. We show that this method can be applied in a straightforward manner at x-ray FEL facilities such as the Linac Coherent Light Source by slightly adjusting the second bunch compressor followed by running the bunch on an rf zero-crossing phase of the final linac. After taking into account the linac wakefield, we find the condition under which the final beam energy spread corresponds directly to the compressed bunch length. When used in conjunction with a high-resolution electron spectrometer, this method potentially reveals temporal information of femtosecond and sub-femtosecond electron bunches used by such FELs.
* K. Ricci and T. Smith, Phys. Rev. ST-AB 3, 032801 (2000).
Tech-X, Boulder, Colorado
TXUK, Warrington
Multipacting is a potential limit on the power one can deliver to different components of an FEL source, including the power couplers and the electron source cathode. Simulation is a main tool in helping to understand and mitigate multipacting. We present recent work on benchmarking multipacting simulation, including comparison with other codes and with rectangular waveguide experiment.
DESY, Hamburg
Electron bunches at the free electron laser FLASH at DESY have a duration of 10 fs to 150 fs and an arrival-time jitter of about 150 fs (rms). It is anticipated that the newly installed optical synchronisation system will stabilize the seed and pump-probe lasers to within ~10 fs. In order to perform reliable and stable seeding, the electron bunch timing jitter needs to be reduced. Bunch arrival-time monitors measure the arrival-time fluctuations at different locations and are used in a beam-based feedback loop to correct the amplitude of the accelerator RF. In order to provide reliable operation and high availability of the bunch arrival-time feedback, intensive efforts have been undertaken in system automation and exception handling. This will be discussed along with the latest results and limitations on the stability of the arrival-times at FLASH.
Belarussian State University, Scientific Research Institute of Nuclear Problems, Minsk
Volume Free Electron Laser (VFEL) is a peculiar kind of radiation generators using volume multi-wave distributed feedback*. Recent years applications of a “grid” photonic crystal (crystal-like artificial periodic structure) as a volume resonator for VFEL operation are intensively studied. Theoretical analysis** shows that a periodic metal grid does not absorb electromagnetic radiation and the ''grid'' photonic crystal, made of metal threads, is almost transparent for electromagnetic waves within the frequency range from GHz to THz. Operation of Volume Free Electron Laser with a photonic crystal formed by thin metallic threads periodically strained inside a waveguide*** confirmed the above conclusions. In the present paper operation of Volume Free Electron Laser with the photonic crystal built from brass foils strained inside a cylindrical waveguide is discussed. Dependence of radiation yield on the crystal length is studied in the range up to 8 GHz. Experimental results are compared with those obtained for the photonic crystal formed by threads.
* V.Baryshevsky, NIM A445 (2000) 281; LANL e-print archive physics/9806039.
** V.Baryshevsky, A.Gurinovich, NIM B252(2006)92.
*** V.Baryshevsky, N.Belous, A.Gurinovich et al,FEL'06,TUPPH012,p.331
SLAC, Menlo Park, California
Free Electron Lasers require a variety of beam diagnostics for tuning and feedback. This tutorial will cover radio frequency analog and digital signal processing as used in a variety of instrumentation including beam position, bunch length and arrival time monitors. It will also cover beam profile monitors including wire scanners, fluorescent screens, and optical transition radiation foils, including the issues with coherent emission from high brightness beams. In addition, it will discuss the unique requirements for X-ray instrumentation for existing and future XFELs.