SLAC, Menlo Park, California
The Linac Coherent Light Source free-electron laser was commissioned on 10 April 2009. The facility has begun operating for atomic/molecular/optical science experiments. Commissioning results have been presented*. Performance of the facility in its first user run (1 October - 21 December) and current machine development activities will be presented.
*P. Emma, et al., "Lasing and saturation of the LCLS and future development", Proceedings of the 2009 Free Electron Laser Conference, 23-28 August 2009, Liverpool, UK
RIKEN/SPring-8, Hyogo
SASE based X-ray free-electron laser is now under construction at the SPring-8 site. This project is aiming at realization of SASE FEL of 1 angstrom initially and approaches to seeded XFEL in the second stage. For this future extension, a very unique system was adopted, composed of a low emittance SHB-based injector with CeB6 cathode thermionic gun, normal conducting high gradient C-band acceleration system and high performance in-vacuum undulators. This presentation will provide a comprehensive project review and recent project progress.
DESY, Hamburg
Uni HH, Hamburg
The free-electron laser user facility FLASH at DESY, Germany has been upgraded. The upgrade started in autumn 2009 after almost 2 years of a very successful second user period. The beam energy is increased to 1.2 GeV by installing a 7th superconducting accelerating module. The new module is a prototype for the European XFEL. Among many other upgrades, 3rd harmonic superconducting RF cavities are installed in the injector. The main purpose is to flatten and - to a certain extend - to shape the longitudinal electron beam phase space improving the dynamics behavior of the beam. The seeding experiment sFLASH is being commissioned, an important step forward to establish seeded FEL radiation for user experiments. After the ongoing commissioning, the 3rd user period will start this summer. In many aspects FLASH will be an FEL with a new quality of performance: a wavelength approaching the carbon edge and the water window, tunable pulse width, and with thousands of pulses per second. This report summarizes the recently finished upgrade of FLASH and reports on the results of the ongoing commissioning and the expected performance as a free electron laser user facility.
ELETTRA, Basovizza
Uni LJ, Ljubljana
The FERMI@Elettra injector, comprised of a high-gradient, s-band, photo-cathode rf gun, the PC gun driven laser, the first two accelerating sections, controls, and suite of diagnostics has been commissioned in 2009. The electron beam has been characterized in terms of charge, energy, energy spread and transverse emittance, and results are provided in this paper. In early 2010 linac commissioning up to 250MeV continued, and by using the RF deflecting cavity, the slice parameters of the beam have been measured. Moreover, studies on the laser pulse shaping and the relative optimization of the longitudinal ramp profile required by the nominal bunch configuration are presented in this paper.
INFN/LNF, Frascati (Roma)
Istituto Nazionale di Fisica Nucleare, Milano
Università di Roma I La Sapienza, Roma
INFN-Roma II, Roma
Università di Roma II Tor Vergata, Roma
University of Rome La Sapienza, Rome
Rome University La Sapienza, Roma
ENEA C.R. Frascati, Frascati (Roma)
The region of the spectrum from 0.3 to 5 THz is of great interest for several experiments in different areas of research. A THz radiation source can be produced at SPARC as coherent transition radiation emitted by either a compressed or longitudinally modulated beam intercepting a metal foil placed at 45° with respect to the beam propagation. Results on the characterization of the THz source at SPARC are described in the paper.
SLAC, Menlo Park, California
We discuss the feasibility of an application of an implicit finite-difference approximation to calculate the fields of a bunch moving with no restriction inside the vacuum chamber.
INFN/LNF, Frascati (Roma)
ENEA C.R. Frascati, Frascati (Roma)
Rome University La Sapienza, Roma
LBNL, Berkeley, California
The effects of microbunching instability for the SPARX accelerator have been analyzed by means of different numerical simulation codes and analytical approach. The laser heater counteracting action has been also addressed in order to optimize the parameters of the compression system, either hybrid RF plus magnetic chicane or only magnetic, and possibly enhance the FEL performance.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Cockcroft Institute, Warrington, Cheshire
JAI, Oxford
Diamond, Oxfordshire
We present progress in the design of the recirculating linac option for the UK New Light Source. Improvements in all accelerator sections have been made such that the output meets the required specifications to drive the seeded NLS FELs. Full start-to-end simulations and tolerance studies are presented together with a comparison to the baseline, single pass linac design.
Northern Illinois University, DeKalb, Illinois
Tech-X, Boulder, Colorado
Terahertz (THz) radiation has generated much recent interest due to its ability to penetrate deep into many organic materials without the damage associated with ionizing radiations. The generation of copious amounts of narrow-band THz radiation using a Smith-Purcell FEL operating as a backward wave oscillator is being pursued by several groups. In this paper we present start-to-end simulations of a Smith-Purcell FEL operating in the superradiant regime. Our concept incorporates a double grating configuration to efficiently bunch the electron beam, followed by a single grating to produce Smith-Purcell radiation. We demonstrate the capabilities and performances of the device, including initial beam properties (emittance and energy spread), with the help of numerical simulations using the conformal finite-difference time-domain electromagnetic solver VORPAL.
CANDLE, Yerevan
DESY, Hamburg
The options for an extremely low bunch charge regime (20 pC) of the European XFEL project are studied. The parameter study (saturation length and power) is performed for a wide range of the beam normalized emittance, bunch length and energy spread. The study is based both on analytical scaling of the SASE FEL performance and numerical simulations.
YerPhI, Yerevan
We consider generation of diffusive radiation by a charged particle passing through a random stack of plates in the infrared region. Diffusive radiation originates due to multiple scattering of pseudophotons on the plates. To enhance the radiation intensity one needs to make the scattering more effective. For this goal we suggest to use materials with negative dielectric constant .
DESY, Hamburg
The free-electron laser facility FLASH at DESY, Germany finished its second user period scheduled from November 2007 to August 2009. More than 300 days have been devoted for user operation, a large part of beamtime has been allocated for machine studies for further developments, including beamtime for XFEL and ILC R&D. FLASH provides trains of fully coherent 10 to 50 femtosecond long laser pulses in the wavelength range from 40 nm to 6.8 nm. The SASE radiation contains also higher harmonics; several experiments have successfully used the third and fifth harmonics. The smallest wavelength used was 1.59 nm. We will give a summary of the experience from two years of user operation at FLASH.
DESY, Hamburg
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
Uni HH, Hamburg
FLASH has been a user facility since 2005, delivering radiation in the wavelength range between 7 and 47 nm using the SASE principle. In order to increase user beam time and improve the radiation properties delivered to users, a major extension of the user facility called FLASH II has been proposed by DESY in collaboration with the HZB, which is a seeded FEL over the parameter range of FLASH. As logical continuation, the HHG development program started with sFLASH, will result in direct seeding. Because in the foreseeable future there will probably not be HHG seed lasers available at high repetition rates down to wavelengths of 4 nm, a cascaded HGHG scheme will be used to produce short wavelengths. After a first design report, the project now enters its preparation phase until the decision for funding will be taken. During this time, the FLASH beam parameters after the present upgrade 2009/2010 will be characterized and the present design will be re-evaluated and adjusted. In addition, complete start-to-end simulations will complete the simulations which have been performed so far, including a complete design of the extraction area.
DESY, Hamburg
Friedrich Schiller Universität, Jena
Uni HH, Hamburg
The performance of fourth generation light sources is of interest in many fields in nature science. Different seeding schemes for FELs are under investigation to improve timing stability, pulse shape and spectrum of the amplified XUV or X-ray pulses. One of the most promising schemes is direct seeding by high-harmonic generation (HHG) in gas. A seeded free electron laser with a tuneable wavelength range from 10 to 40nm and a bunch frequency of up to 100 kHz (1 MHz upgraded), as proposed for FLASH II (collaboration HZB/DESY), makes high demands on the HHG seed source concerning conversion efficiency and stability. However, the most challenging task is the conception of a laser system with a repetition rate of 100 kHz (1 MHz upgraded). The key parameters for this laser amplifier system are pulse energies of 1-2mJ and sub-10fs pulse duration. We report on the development status of the required laser system for the seed source and give an overview of first concepts for the HHG target setup which can comply with the requirements of a new seeded FEL at DESY.
Uni HH, Hamburg
DESY, Hamburg
PSI, Villigen
DELTA, Dortmund
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
Recently, the free-electron laser in Hamburg (FLASH) at DESY has been upgraded considerably. Besides increasing the maximum energy to about 1.2 GeV and installation of a third harmonic rf cavity linearizing the longitudinal phase space distribution of the electron bunch, an FEL seeding experiment at wavelengths of about 35 nm has been installed. The goal is to establish direct FEL seeding employing coherent VUV pulses produced from a powerful drive laser by high-harmonic generation (HHG) in a gas cell. The project, called sFLASH, includes generation of the required HHG pulses, transporting it to the undulator entrance of a newly installed FEL-amplifier, controlling spatial, temporal and energy overlap with the electron bunches and setting up a pump-probe pilot experiment. Sophisticated diagnostics is installed to characterize both HHG and seeded FEL pulses, both in time and frequency domain. Compared to SASE-FEL pulses, almost perfect longitudinal coherence and improved synchronization possibilities for the user experiments are expected. In this paper the status of the experiment is presented.
DESY Zeuthen, Zeuthen
DESY, Hamburg
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
Uni HH, Hamburg
The PITZ facility is established for the development and testing of electron sources for FELs like FLASH and the European XFEL. The facility has been upgraded during the shutdown starting in summer 2007 to extend the capability of the facility to produce and characterize low emittance electron beams. The upgraded setup mainly includes a photo cathode L-band RF gun with solenoid magnets for space charge compensation, a post acceleration booster cavity and several diagnostic systems. The diagnostic systems consist of charge and beam profile monitors, emittance measurement systems and spectrometers with related diagnostics in dispersive arms after the gun and the booster cavities. RF gun operation with an accelerating gradient of 60 MV/m at the cathode is realized with this setup. A new photo cathode laser system with broader spectral bandwidth was installed for optimizing the temporal distribution of the laser pulses regarding to electron beam properties. Experimental results with this setup demonstrated very high electron beam quality as required for the photoinjector source of the European XFEL. In this contribution, the PITZ facility setup in year 2008-2009 will be presented.
*for the PITZ Collaboration
DESY Zeuthen, Zeuthen
INRNE, Sofia
DESY, Hamburg
YerPhI, Yerevan
JINR, Dubna, Moscow Region
UCLA, Los Angeles, California
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
MEPhI, Moscow
NSC/KIPT, Kharkov
MBI, Berlin
At the Photo Injector Test facility at DESY, Zeuthen site (PITZ), high brightness electron sources for linac based Free Electron Lasers (FELs), like FLASH and the European XFEL are developed and characterized. The electrons are generated via the photoeffect at a cesium telluride (Cs2Te) cathode and are accelerated by a 1.6-cell L-band RF-gun cavity with an accelerating gradient at the cathode of about 60 MV/m. The profile of the cathode laser pulse has been optimized yielding small emittances using laser pulse shaping methods. The transverse projected emittance is measured by a single slit scan technique. The measurement program in the last run period at PITZ concentrated on emittance measurements for the nominal 1 nC beam and emittance optimization for lower bunch charges. The recent results show that normalized projected emittances of about 1 mm-mrad for 1 nC charge and below 0.5 mm-mrad for 250 pC bunch charges can be realized at PITZ. The facility setup and measurement results including the uncertainty of the measured values will be reported and discussed in this contribution.
CBS, Mumbai
BARC, Mumbai
The stability of free-electron laser (FEL) resonators differs from that of resonators of conventional lasers, because of the nature of the FEL interaction. Therefore the stability diagram is modified, and near-concentric configurations are preferred to near-confocal. We study the stability of FEL resonators (especially for g1 =/ g2) using simulations, as well as using a simple thin-lens model, and show that the near-concentric configuration is indeed preferable, while the confocal configuration becomes unstable. Also, since FELs can be widely tuned in wavelength, we investigate the stability of the resonator as a function of the wavelength.
ELETTRA, Basovizza
The single pass FEL facility FERMI@ELETTRA, in construction at the ELETTRA Synchrotron Radiation Laboratory in Trieste, requires very short electron bunches with a very high beam quality at the entrance of the undulator chain. To linearize the longitudinal phase space before the bunch compression, mitigating the effects of Coherent Synchrotron Radiation (CSR), a 4th harmonic accelerating section (12 GHz) will be installed before the first magnetic chicane. Here an overall description of the X-band system under development is reported.
ELETTRA, Basovizza
University of Nova Gorica, Nova Gorica
The commissioning of the first stage (FEL-1) of FERMI@Elettra has started in the summer 2009. During the first year of operation, the efforts will mainly concentrate on the optimization of the gun performance, as well as on electron-beam acceleration and transport through the LINAC. By fall 2010, it is planned to generate out of the LINAC an electron beam that may be injected into the FEL-1 undulator chain and used to get the first FEL light. In this paper, we present the requirements for FEL-1 commissioning, both in terms of hardware and electron beam properties.
ELETTRA, Basovizza
The electron beam transverse emittance and Twiss parameters have been measured during the commissioning of FERMI@elettra. Matching of the beam optics to the lattice transverse acceptance and beam transport was performed by means of the elegant particle tracking code; this was integrated with the Tango-server based high level software of FERMI@elettra. Matlab scripts were used as an intermediate layer between the code and the server to automate the matching procedure. The software environment, the experimental results and the comparison with the model are described in this paper.
INFN/LNF, Frascati (Roma)
Istituto Nazionale di Fisica Nucleare, Milano
UCLA, Los Angeles
JASRI/SPring-8, Hyogo-ken
Shining a photocathode at the same time with an UV laser able to extract electrons and an IR laser properly tuned could influence the way the electron beam is generated. Such a process is under investigation at SPARC, through direct measurements, as much as through computer codes assessment studies.
Rome University La Sapienza, Roma
INFN/LNF, Frascati (Roma)
The SPARX-FEL project is meant to provide ultra high peak brightness electron beams, with the energy ranging between 1.5 - 2.4 GeV, in order to generate FEL radiation in the 0.6-40 nm range. The construction will start with a 1.5 GeV Linac; besides the basic S-band technology the C-band option is also presently under study. Both RF-compression and magnetic chicane techniques are foreseen to provide the suitable electron beam to each one of the three undulator systems which will generate VUV-EUV, Soft X-Rays and Hard X-rays radiation respectively. Dedicated beamlines will distribute the beam to the downstream undulators for applications in basic science and technology. In this paper we present the status of the project funded by the Italian Department of Research, MIUR, and by the local regional government, Regione Lazio, that foresees the construction of a user facility inside the Tor Vergata campus by collaboration among CNR, ENEA, INFN and the Università di Tor Vergata itself.
Tokyo University of Science, IR FEL Research Center, Chiba
MELCO SC, Tsukuba
KEK, Ibaraki
IR-FEL research center of Tokyo University of Science (FEL-TUS) is a facility for aiming at the development of high performance FEL device and promotion of photo-science using it. The main part of FEL-TUS is a mid-infrared FEL (MIR FEL) which consists of an S-band linac and an undulator combined with an optical resonance cavity. MIR-FEL provides continuously tunable radiation in the range of 5-14 micron and a variety of experiments are by the use of this photon energy corresponding to the various vibrational modes of molecules are now underway. We also develop far-infrared FEL (FIR FEL) installed an RF-gun with Disk-and-Washer accelerating cavity for high quality electron beam. The current status of FEL-TUS will be presented.
RIKEN/SPring-8, Hyogo
University of electro-communications, Tokyo
The intensity of SASE generated by undulators is sensitive to the peak intensity fluctuation of an electron bunch. The bunch is formed by velocity bunching in an injector and magnetic bunching in bunch compressors (BC). The peak intensity is sensitive to rf phase and amplitude of off-crest acceleration at injector cavities and 5712 MHz cavities before the BCs. Thus, demanded stabilities of the rf phase and amplitude for stable SASE generation are very tight. These are 0.6 degree (p-p) and 0.06 % (p-p) at the 5712 MHz cavities, respectively. We are constructing a low-level rf (LLRF) system comprising a master oscillator, an optical rf signal transmission system, and a digital rf control system using IQ modulator/demodulator to drive klystrons. To realize the demands, much attention was paid to temperature stabilization for the system. A water-cooled 19-inch rack and a water-cooled cable ducts are employed for almost all part of the system. Temperature stability of the rack was 0.4 K (p-p) even though outside was 4 K (p-p). The phase and amplitude stabilities of the LLRF modules were measured to be 0.30 degree (p-p) and 0.56 % (p-p). These stabilities are sufficient for our demands.
JASRI/SPring-8, Hyogo-ken
RIKEN/SPring-8, Hyogo
XFEL/SPring-8 is under construction, which is aiming at generating coherent, high brilliance, ultra-short femto-second X-ray pulse at wavelength of 1Å or shorter. The injector consists of a 500kV thermionic gun (CeB6), a beam deflecting system, multi-stage RF structures and ten magnetic lenses. The multi-stage RF structures (238MHz, 476MHz, 1428MHz) are used for bunching and accelerating the beam gradually to maintain the initial beam emittance. In addition, in order to realize linearizing the energy chirp of the beam bunch at three magnetic bunch compression systems after the injector system, we prepared extra RF structures of 1428MHz and 5712MHz. It is important to stabilize the gap voltage of those RF structures because the intensity of X-ray pulse is more sensitive for a slight variation of the RF system in the injector. We developed some stable amplifiers for those RF structures, and confirmed the amplitude and phase stability of an RF signal outputted from the amplifiers. The measurement results achieved nearly the requirement of design parameters. In this paper, we describe the development status and the achieved performances of RF equipment of the injector section.
Kanazawa University, Kanazawa
In the Cherenkov free electron laser, the interacted electron with the electromagnetic (EM) wave can be represented as a point particle or as a spatially spreading electron wave in the classical or quantum mechanical framework, respectively. In our previous theoretical analysis for the optical region, the electron is described by a plane wave with finite spreading length. This electron wave model was successfully implied for the optical region whereas the spreading length of the electron wave is greater than the wavelength of the optical wave. In this work, when the EM wavelength is sufficiently greater than the spreading length of the electron wave, such as in the microwave region, the electron is assumed to be a spatially localized point particle. This classical analysis is performed using same parameters used in the quantum electron wave model, such as a coupling coefficient between the electron beam and the EM field and the electron relaxation time. Also, we present analytical expressions to describe the stimulated and spontaneous emissions. We show that the classical treatment is consistent with the quantum analysis applied in the optical regime.
JAEA/Kansai, Kyoto
Kyoto Univeristy, Kyoto
Interactions of x-ray free electron laser (XFEL) light with a single cluster target are numerically investigated. The irradiation of XFEL light onto material leads to the ionization of the target by photo-ionization and generation of high energy electrons. This results in the further ionization via Auger effect, collisional ionization, and field ionization. The ionization rate or time scale of each process depends on the condition of XFEL (intensity, duration, photon energy) and target size. In order to understand the ionization dynamics, we used a three-dimensional Particle-in-Cell code which includes the plasma dynamics as well as relevant atomic processes such as photo-ionization, the Auger effect, collisional ionization/relaxation, and field ionization. It is found that as the XFEL intensity increases to as high as roughly 1021 photons/pulse/mm2, the field ionization, which is the dominant ionization process over the other atomic processes, leads to rapid target ionization. The target damage due to the irradiation by XFEL light is numerically evaluated, which gives an estimation of the XFEL intensity so as to suppress the target damage within a tolerable range for imaging.
* T. Nakamura, et al., Phys. Rev. A, vol. 80, 053202 (2009)
Kyoto IAE, Kyoto
A mid-infrared free electron laser (MIR FEL) facility has been constructed for the basic research on energy materials in the Institute of Advanced Energy, Kyoto University. The MIR FEL saturation at 13.2 μm was observed in May 2008, and the construction of the FEL delivery system from accelerator room to the optical diagnostic station and experimental stations has been finished in Dec. 2009. In the conference, optical properties of the MIR FEL and research program using MIR-FEL will be introduced.
Sokendai - Okazaki, Okazaki, Aichi
UVSOR, Okazaki
Nagoya University, Nagoya
Light source technologies based on laser seeding are under development at the UVSOR-II electron storage ring. In the past experiments, we have succeeded in generating coherent DUV (Deep Ultra-Violet) harmonics with various polarizations. A spectrum measurement experiment of CHG (Coherent Harmonic Generation) was carried out by using a spectrometer of from visible to DUV range. In order to diagnose spectra of shorter-wavelength CHG, a spectrometer for VUV (Vacuum Ultra-Violet) has been constructed and the VUV CHG was measured. In addition, we try to use a seeding light source based on not only fundamental of Ti: Sapphire laser and the harmonics generated from non-linear crystals but also HHG (High Harmonic Generation) in a gas for the CHG experiment. Now the HHG system is under development. In this presentation, we introduce the VUV spectral measurement system and the HHG system and also report about comparison between the results of the current CHG experiments and design studies of numerical calculation for them.
ISIR, Osaka
KEK, Ibaraki
We have been developing a Terahertz free electron laser (FEL) based on the 40 MeV, 1.3 GHz L-band electron linac at the Institute of Scientific and Industrial Research (ISIR), Osaka University. After the FEL lasing at the wavelength of 70 um (4.3 THz)*, next targets of the FEL development are to extend the available laser wavelength, to increase the FEL power, and to evaluate characteristics of FEL. Since the lowest energy of the linac was restricted by a fixed-ratio power divider between the acceleration tube and the buncher, we have prepared the new one with a different ratio to extend the wavelength longer side. As a result, the wavelength region is able to be extended to 25 - 147 um (12.5 - 2 THz). The maximum output energy of the FEL macropulse so far obtained is 3.6 mJ at 66 um. The peak macropulse power available to user experiments is estimated to be 1 kW or less, given that the pulse duration is 3 us. Three users groups have begun experiments using the FEL. We will report these recent activities on the Terahertz FEL.
* G. Isoyama, R. Kato, S. Kashiwagi, T. Igo, Y. Morio, Infrared Physics & Technology 51 (2008) 371-374.
AIST, Tsukuba, Ibaraki
Recently, an FEL in the near-infrared (IR) region was oscillated at a compact storage ring NIJI-IV whose circumference was 29.6 m. We have been developed a device for the storage ring FEL in the IR region with a 3.6-m optical klystron ETLOK-III, and the first lasing at a wavelength of around 1450 nm was achieved at February 2009. The maximum power of the FEL was 0.3 mW per vacuum window and the relative linewidth was 3·10-4.* Moreover, gamma-ray beam was also produced in the long straight section of NIJI-IV by Compton backscattering of the intra-cavity IR FEL and the stored electron beam with an energy of 310MeV. After the first lasing experiment, we have successfully performed to extend the lasing wavelength region and increase FEL power, and this recent progress will be presented.
* N. Sei, H. Ogawa, K.Yamada, Opt. Lett. 34 (2009) 1843.
TUB, Beijing
Smith-Purcell radiation (SPR) is emitted when an electron passes near the surface of a periodic metallic grating. The radiation wavelength λ observed at the angle θ measured from a direction of surface grating is determined by λ=D/|n|(1/β cosθ), Where D is the grating period, βc is the electron velocity, c is the speed of light, and the integer n is the spectral order. This radiation mechanism is widely applicated to THz radiation source, for which can be developed into tunable and compact one. In this paper, the radiation characteristics of terahertz (THz) SPR generated from the ultrashort electron beam are analyzed with the three-dimensional particle-in-cell simulation. For obtaining the intense THz radiation, the grating parameters and that of ultrashort electron beam are optimum. The radiation power and energy are obtained by the PIC simulation. The band width of train bunches is compared with that of single bunch. The formation factors including the longitudinal and transverse are calculated. Through this study, we observe that the radiation power is enhanced and the band width can be adjusted.
TUB, Beijing
Tsinghua University Thomson X-ray source ( TTX ) has been proposed at Tsinghua University. With the nominal electron beam parameters ( beam energy of 50MeV, slice energy spread of 5keV, peak current of 600A, rms normalized emittance of 2 mm mrad ) of the TTX linac , the design of Free Electron Laser ( FEL ) by the Echo-Enabled Harmonic Generation ( EEHG ) scheme is presented in this paper. High harmonics of the seeding laser is generated by the EEHG scheme. Parameters of the undulators and seeding lasers are optimized. Simulation results using the GENESIS code are also presented in this paper.
USTC/NSRL, Hefei, Anhui
An easy-to-implement scheme called Enhanced High Gain Harmonic Generation has been proposed and shown to be able to significantly enhance the performance of traditional HGHG-FEL. In this paper we investigate the effects of the system parameters in EHGHG scheme, such as the electron energy tuning, the energy spread, the dispersive strength, amount of the phase shift, and the power of seed laser. The numerical results are presented, and shown that: the EHGHG scheme has acceptable the parameters tolerance requirements and is not more or even less sensitive to the system parameters than that of the existing scheme.
PAL, Pohang, Kyungbuk
POSTECH, Pohang, Kyungbuk
Due the field asymmetry in RF gun due the holes in full cell cavity, the emittance of electron beam can be increased. To generate the low emittance electron beam for XFEL, the elimination of the each field components is very important. The RF field can be decomposed as dipole and quadrupole components. The effect on the emittance increase of each component is studied in this presentation by numerical method. The 3D field map is constructed by MATLAB code as input of PARMELA code with each component distribution of the RF field. In this paper the emittance increase of electron beam by the each component of the RF field will be presented.
INFLPR, Bucharest - Magurele
Valahia University, Faculty of Sciences, Targoviste
Bucharest University, Faculty of Physics, Bucharest-Magurele
This paper is a presentation of a parameter study for FEL Project at INFLPR considering recent advances of technologies in the domain of accelerators, lasers, undulators and seeded operation with HHG which in their turn allow the construction of a national user facility based on an intense FEL at VUV wavelengths. The calculations also considered the possibilities for the facility to be upgraded for EUV regime, in a second stage. In the first stage, results were obtained for the FEL subsystem parameters starting from the 1 GeV beam electron energy, a 500 A electron current, a single stage HGHG FEL and VUV regime. Also, the status of the project is briefly sketched herein. On behalf of the RO FEL Design Team.
JINR, Dubna, Moscow Region
JINR/LHE, Moscow
Different methods for diagnostic of ultrashort electron bunches are developed at JINR-DESY collaboration within the framework of the FLASH and XFEL projects. Photon diagnostics developed at JINR-DESY collaboration for ultrashort bunches are based on calorimetric measurements and detection of undulator radiation. The MCP based radiation detectors are effectively used at FLASH for pulse energy measurements. The infrared undulator constructed at JINR and installed at FLASH is used for longitudinal bunch shape measurements and for two-color lasing provided by the FIR and VUV undulators. The JINR also participates in development and construction of Hybrid Pixel Array Detector on the basis of GaAs sensors. The special laser source for the KEK photo-cathode gun is developed within the frame of the JINR-IAP-KEK collaboration.
PSI, Villigen
In the framework of the SwissFEL project, an alternative electron source to an RF photo-gun was investigated. It consists of a high voltage (up to 500 kV), high gradient pulsed diode system followed by single stage RF acceleration at 1.5 GHz. The electrons are produced from photo-cathodes or from field emitter arrays. The final goal of this accelerator is to produce a 200 pC electron beam with a projected normalized emittance below 0.4 mm.mrad and a bunch length of less than 10 ps. We present comparisons between beam dynamic simulations and measurements, as well as thermal emittance and quantum efficiency (QE) measurements obtained by producing photo-electrons from various metal cathodes.
NTHU, Hsinchu
NSRRC, Hsinchu
A THz-pulse-train photoinjector is under construction at the High-energy OPtics and Electronics (HOPE) Lab. 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 1nC 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. The authors gratefully acknowledge funding supports from National Scienc Council under Contract NSC 97-2112-M-007-018 -MY2, National Synchrotron Radiation Research Center under Project 955LRF01N, and National Tsinghua University under Project 98N2534·101.
NTHU, Hsinchu
We study a desktop MW superradiance free-electron laser (FEL) at THz frequencies. By using some nominal beam parameters from a THz-pulse-train electron gun, we show in theory and simulation that 10-MW-level radiation power at THz frequencies is achievable from a meter long undulator in one single electron transit through the undulator. The proposed THz superradiance FEL is directly attached to the emittance compensating coil of the photoinjector without using any additional beam-fucusing element in between. This compact design allows the construction of a 10-MW FEL at THz frequencies on an ordinary desk. We will also show the usefulness of a tapered undulator for a superradiance FEL. With a 20% linearly tapered undulator, the FEL radiation power can be increased by more than 30%. This FEL is being constructed at the High-energy OPtics and Electronics (HOPE) Laboratory, National Tsinghua University, Taiwan. Experimental progress of this ultracompact, high-power single-pass superradiance FEL will be reported in the conference.
Ankara University, Faculty of Engineering, Tandogan, Ankara
N.U, Nigde
Gazi University, Faculty of Arts and Sciences, Teknikokullar, Ankara
Dumlupinar University, Faculty of Science and Arts, Kutahya
Ankara University, Faculty of Sciences, Tandogan/Ankara
SDU, Isparta
UU, Bursa
Turkish Accelerator Center Infrared Free Electron Laser and Bremsstrahlung (TAC IR FEL&Brems.) project aims to produce cw mode FEL in 2.5-250 microns range and to produce bremsstrahlung photons using 15-40 MeV electron beam. The project is supported by State Planning Organization (SPO) of Turkey and is proceeded with inter university collaboration under the coordination of Ankara University. This facility is now called Turkish Accelerator and Radiation Laboratory at Ankara (TARLA) since its building located at Golbasi town 30 km south of Ankara, Turkey It is proposed that the facility will consist of 300 keV thermionic DC gun, two superconducting RF module and two optical resonator systems with 25 and 90 mm period lengths. In this study, the status and road map of the project is presented including some technical details on accelerator and FEL. In addition the research potential of facility is summarized.
NSC/KIPT, Kharkov
Simulation results of subpicosecond bunch formation due to phase motion of electrons in traveling wave are presented. It has been shown that at satisfying phase conditions of electron injection that are necessary for velocity bunching, relative phase velocity of the total wave excited both by RF generator and particles becomes different from unit increasing bunch compression. Simulation of transportation of obtained 8.5 MeV bunches through undulator with a period of 90.6 mm and estimation of bunch form-factor at 446 harmonic of bunch repetition rate of 2797.15 MHz also was carried out. The data obtained allow to expect coherent radiation from undulator at wave-length of 240 um.
National Taras Shevchenko University of Kyiv, Radiophysical Faculty, Kiev
In the report the possibilities of FEL optimization and creation of tandem laser are considered. One of the optimal ways of coherent hard radiation generation is connected with the creation of FEL on channeling relativistic particles in perfect crystals [1]. The main role in solution of such problem plays the full Doppler effect [2]. The possibility of creation of tandem FEL, where one particle can radiate multiple times on one transition, is predicted for the first time. For such laser the intensive process of consecutive generation of two types of photons with different frequencies on the same radiating transition is possible and this double photon generation leads to the restoration of the initial state of quantum system. This effect allows to predict the possibility of multiple repeat of radiation cycle. The pumping source for such laser is the kinetic energy of moving particles. In such systems there is no need for inversion and absorption on radiation frequency is totally absent. The main problem of realization of tandem FEL is connected with the need of mediums with positive susceptibility in high frequency range, possible ways to solve this problem are also regarded.
1. Vysotskii V.I., Kuzmin R.N. Gamma-Ray Lasers, MSU Publ. House, Moscow, 1989.
2. Vysotskyy M.V., Vysotskii V.I. // Nuclear Instr. and Methods in Physics Research B, 2006, V. 252, P. 75-80
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
The superconducting LINAC for the proposed New Light Source (NLS) project in the UK, will consist of 18 cryomodules operating at 1.8 K, each having 8, 1.3 GHz cavities operating in CW mode. The cryomodule design and cryogenic distribution scheme will be one of the key elements to achieve the desired performance from the superconducting RF (SRF) linac. Around the world, several large scale facilities (based on SRF linacs) are already operating (for example: CEBAF, SNS, FLASH) and several more have been proposed (XFEL, ILC, Cornell ERL, etc.). In this paper we define the requirements for an appropriate cryomodule, adopting proven L-band technology systems and also describe the cryogenic distribution scheme, in order to develop an effective and economic solution for the NLS.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
JAI, Oxford
SLAC, Menlo Park, California
USTRAT/SUPA, Glasgow
Optimisation studies of an HHG-seeded harmonic cascade FEL design for the UK's proposed New Light Source (NLS) facility are presented. Three separate FELs are planned to meet the requirements for continuous coverage of the photon energy range 50-1000 eV with variable polarisation, 20 fs pulse widths and good temporal coherence. The design uses an HHG seed source tuneable from 50-100 eV to provide direct FEL seeding in this range, and one or two stage harmonic cascades to reach the higher photon energies. Studies have been carried out to optimise a harmonic cascade FEL operating at 1 keV; topics investigated include modulator configuration, seed power level and effects of the HHG seed structure. FEL simulations using realistic electron beam distributions are presented and tolerance to increased emittance has been considered.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
USTRAT/SUPA, Glasgow
Cockcroft Institute, Warrington, Cheshire
A scheme for the generation of attosecond pulse trains in FEL amplifiers was recently proposed*. The method uses repeated equal temporal delays between the electron bunch and co-propagating radiation to generate a modal structure in the radiation field. The modes may be phase-locked via an energy modulation in the electron beam. As a consequence of the radiation /electron delays, the relative radiation /electron slippage during the interaction is increased and leads to a longer cooperation length with the effect of improving the temporal coherence. In this paper we present simulations demonstrating this effect. In particular, we show that the average spacing between the temporal spikes in a SASE FEL is increased in proportion to the increase in the cooperation length. It may therefore be possible to operate a SASE FEL in single-spike mode with longer, higher charge, electron bunches than previously thought possible.
* Physical Review Letters 100, (203901) 2008.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
A design optimisation has been performed for an L-band, SRF linac adopting cryomodule technology developed as part of the TESLA Technology Collaboration (TTC). A conventional XFEL cryomodule has been adopted as a baseline design and modified to allow for CW operation at a nominally high Qo level. An assessment of appropriate operating gradient, based upon expected sub-system component costs and SRF linac operating costs, has been performed. The associated cryomodule modifications to accommodate such a large dynamic load are also highlighted, along with identifying an appropriate RF control architecture which can achieve the stringent phase and amplitude stability requirements for NLS.
USTRAT/SUPA, Glasgow
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Pulsar Physics, Eindhoven
Recent progress in developing laser-plasma accelerators is raising the possibility of a compact coherent radiation source that could be housed in a medium sized university department. Furthermore, since the duration of electron bunches from laser-plasma wakefield accelerators is determined by the relativistic plasma wavelength, radiation sources based on these accelerators can produce pulses with femtosecond durations. Beam properties from laser-plasma accelerators have been traditionally thought of as not being of sufficient quality to produce amplification. Our work shows that this is not the case. Here we present a study of the beam characteristics of a laser-plasma accelerator and the compact ALPHA-X (Advanced Laser Plasma High-energy Accelerators towards X-rays) FEL. We discuss the implementation of a focussing system consisting of a triplet of permanent magnet quadrupoles and a triplet of electromagnetic quadrupoles*. We will present a study of the influence of beam transport on FEL action in the undulator, paying particular attention to bunch dispersion in the undulator. This is an important step for developing a compact synchrotron source or a SASE free-electron laser.
*The design of these devices has been carried out using the GPT code, which considers space charge effects and allows a realistic estimate of electron beam properties along the beam line.
Diamond, Oxfordshire
JAI, Oxford
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
The New Light Source project aims to construct a suite of seeded free-electron lasers driven by a 2.25GeV cw super conducting linac. As part of the upgrade path, a number of options are being considered for generating ultra short (<1fs) soft x-ray pulses, with low-charge 'single-spike' operation and bunch slicing like approaches of particular interest, including as a possible extension to echo-enhanced harmonic generation. In this paper we present the status of this work, including recent results from fully start to end simulations.
Diamond, Oxfordshire
Considerable progress has been made in recent months with the design of the UK's proposed New Light Source facility. This includes further optimisation of the injector, linac and FEL performance and operating parameters, and full start-to-end tolerance and jitter studies. More detailed engineering considerations for key components such as the cw linac cryomodules, undulator and vacuum chamber have been undertaken, as well as overall layout and outline design of the buildings. In this report we summarise progress in all these areas, the current status and future plans for the project.
* on behalf of the NLS project team.
IUCF, Bloomington, Indiana
At the Indiana University Cyclotron Facility (IUCF), we are developing a new XFEL concept, which is based on the Compton scattering and the laser undulator instead of the conventional magnetic undulator. Since the period of the laser undulator is only about 500 nm, the coherent hard X-rays can be generated by using a compact electron accelerator with a beam energy of about 50 MeV. In this paper, we report an estimation of the energy spread growths due to the Compton scattering itself and their impacts on the XFEL lasing in the laser undulator based XFEL concept.
FEL/Duke University, Durham, North Carolina
The Duke FEL and High Intensity Gamma-ray Source (HIγS) are operated with a wide range of electron beam energies (0.24 - 1.2 GeV) and photon beam wavelengths (190 - 1060 nm). Currently, the HIγS provides users with the gamma beams in the energy range from 1 to about 65 MeV, with a near future extension to about 100 MeV. The maximum total gamma-flux produced at the HIγS facility is up to 1010 gammas per second. Production of high level gamma-ray flux, requiring a very high average FEL intra-cavity power and high electron beam current, can cause significant degradation of the FEL mirrors. To ensure the predictability and stability of the HIγS operation for user research program, we have developed a comprehensive program to continuously monitor the performance of the FEL mirrors. This program has enabled us to use a particular set of FEL mirrors for a few hundreds hours of high gamma-flux operation with predictable performance. In this work, we discuss sources and consequences of the mirror degradation for a variety of wavelengths and present our estimates of the mirror life time as a function of the FEL wavelength, gamma-ray polarization, and total gamma-flux.
UCLA, Los Angeles
A simple scheme to generate intense light with orbital angular momentum in an FEL is described. The light is generated from a helically pre-bunched beam created in an upstream modulator. The beam energy is tuned to maximize gain in the higher-order mode which reaches saturation well before the spontaneous modes driven by noise are amplified.
SLAC, Menlo Park, California
Simulations of ion migration in the LCLS RF gun and injector A. Brachmann On behalf of the LCLS commissioning team The motivation for this work was the observed surface contamination of the first LCLS RF gun copper cathode. We will present the results of simulations in regards to ion migration in the LCLS gun. Ions of residual gases will be created by interaction of molecular gas species with the UV drive laser beam and by the electron beam itself. The larger part of those ionized molecules remain in the vicinity of creation, are transported towards beam line walls or away from the cathode. However a significant fraction gains enough kinetic energy to be focused by RF and magnetic fields, reaching the cathode and producing an undesirable increase of the cathode's surface work function. Although this fraction is small, during long term operation, this effect becomes a significant factor limiting the source performance.
SLAC, Menlo Park, California
Surface characterization of the LCLS RF gun cathode A. Brachmann On behalf of the LCLS commissioning team The first copper cathode installed in the LCLS RF gun was used during LCLS commissioning for more than a year. However, after high charge operation (~ 500 pC), the cathode showed a decline of quantum efficiency due to surface contamination caused by residual ionized gas species present in the vacuum system. We report results of SEM, XPS and XAS studies that were carried out on this cathode after it was removed from the gun. X-ray absorption and X-ray photoelectron spectroscopy reveal surface contamination by various hydrocarbon compounds. In addition we report on the performance of the second installed cathode with emphasis on the spatial distribution of electron emission.
SLAC, Menlo Park, California
LBNL, Berkeley, California
In addition to its normal operation at 250pC, the LCLS has operated with 20pC bunches delivering X-ray beams to users with energies between 800eV and 2 keV and with bunch lengths below 10 fs FWHM. A bunch arrival time monitor and timing transmission system provide users with sub 100 fs synchronization between a laser and the X-rays for pump / probe experiments. We describe the performance and operational experience of the LCLS for short bunch experiments.
SLAC, Menlo Park, California
Diamond, Oxfordshire
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
The crossed-planar undulator is a promising scheme for full polarization control in an x-ray FEL*. For SASE FELs, it has been shown a maximum degree of circular polarization of about 80% is achievable**. In this paper, we study the effectiveness of a cross undulator for a seeded x-ray FEL. The degree of circular polarization for both the fundamental and the harmonic radiation are considered.
* K.-J. Kim, Nucl. Instrum. Methods A445, 329 (2000).
** Y. Ding, Z. Huang, Phys. Rev. ST-AB 11, 030702 (2008).
SLAC, Menlo Park, California
LBNL, Berkeley, California
EPFL, Lausanne
In this paper we describe the technical design of an on-going proof-of-principle echo-enabled harmonic generation (EEHG) FEL experiment in the Next Linear Collider Test Accelerator (NLCTA) at SLAC. The experiment was designed through late 2009 and built and installed between October 2009 and January 2010. We present the design considerations, the technical realization and the expected performances of the EEHG experiment.
SLAC, Menlo Park, California
The Linac Coherent Light Source (LCLS) at SLAC is an x-ray Free Electron Laser with wavelengths of 0.15 nm to 1.5 nm. The electron beam stability is important for good lasing. While the transverse jitter of the beam is about 10-20% of the rms beam sizes, the jitter in the longitudinal phase space is a multiple of the energy spread and bunch length. At the lower energy of 4.3 GeV (corresponding to the longest wavelength of 1.5 nm) the relative energy jitter can be 0.125%, while the rms energy spread is with 0.025% five times smaller. An even bigger ratio exists for the arrival time jitter of 50 fs and the bunch duration of about 5 fs (rms) in the low charge (20 pC) operating mode. Although the impact to the experiments is reduced by providing pulse-by-pulse data of the measured energy and arrival time, it would be nice to understand and mitigate the root causes of this jitter. The thyratron of the high power supply of the RF klystrons is one of the main contributors. Another suspect is the multi-pacting in the RF loads. Phase measurements down to 0.01 degree (equals 10 fs) along the RF pulse were achieved, giving hints to the impact of the different sources.
SLAC, Menlo Park, California
LBNL, Berkeley, California
EPFL, Lausanne
ECHO-7 is a proof-of-principle echo-enabled harmonic generation* FEL experiment in the Next Linear Collider Test Accelerator (NLCTA) at SLAC. The experiment aims to generate coherent radiation at 318 nm and 227 nm, which is the 5th and 7th harmonic of the infrared seed laser. In this paper we present the preliminary results from the commissioning run of the completed experimental setup which started in April 2010.
* G. Stupakov, PRL, 102, 074801 (2009); D. Xiang and G. Stupakov, PRST-AB, 12, 030702 (2009).
JLAB, Newport News, Virginia
Jefferson Lab (JLab) is proposing JLAMP (JLab AMPlifier), a 4th generation light source covering the 10-100 eV range in the fundamental mode with harmonics stretching towards the oxygen k-edge. The new photon science user facility will feature a two-pass superconducting linac to accelerate the electron beam to 600MeV at repetition rates of 4.68MHz continuous wave. The average brightness from a seeded amplifier free electron laser (FEL) will substantially exceed existing light sources in this device's wavelength range, extended by harmonics towards 2 nm. Multiple photon sources will be made available for pump-probe dynamical studies. The status of the machine design and technical challenges associated with the development of the JLAMP are presented here.
SLAC, Menlo Park, California
Recently a new concept*, ** for FEL seeding has been proposed that should allow generation of much higher harmonics of the laser modulation than previously envisioned. The Echo-enabled Harmonic Generation (EEHG) FEL uses two modulators in combination with two dispersion sections to generate in the beam a high-harmonic density modulation starting with a relatively small initial energy modulation of the beam. The EEHG seeding technique makes feasible a one stage seeding of soft x-ray FELs. An experimental installation is now being constructed at SLAC to demonstrate the EEHG in the NLCTA facility.
*G. Stupakov, PRL, 102, 074801 (2009).
**D. Xiang and G. Stupakov, PRSTAB, 030702 (2009).