NSRRC, Hsinchu
An in-vacuum undulator with a room-temperature permanent magnet and a superconducting wiggler has become a mature technology and is widely used; it can adopt a short-period length in a medium-energy facility to provide an enhanced photon flux in the hard x-ray region. A cryogenic permanent magnet is applicable for an in-vacuum undulator to enhance the remanence field (Br) and the coercivity force. In future, a cryogenic permanent-magnet undulator and a superconducting wiggler will become mainstream to fulfill a user's requirement of a discrete and a continuous spectrum, respectively, but superconducting technology with HTS wires will have the best potential for the development of insertion devices after the next decade. HTS bulk magnets with magnet flux density 17 T are applicable even for a superconducting undulator; such an undulator can decrease the period length to about 10 mm. A small magnet gap with an extremely- short-period length (about 5 mm) has been studied with a stacked-layer of thin HTS tapes for a superconducting undulator. This report is a review to describe the current and future developments of insertion devices for a medium-energy storage ring and FEL facility.
GUAS, Kanagawa
KEK, Ibaraki
Tsukuba University of Technology, Kasuga Campus, Tsukuba, Ibaraki
Japanese research to build accelerators for high energy physics started with Electron Synchrotron at Institute of Nuclear Study, Tokyo (INS). The development was slow in the beginning, in particular before the construction of KEK-PS. After the experience of TRISTAN, KEKB, one of the best colliders in the world, was eventually constructed. We will review the history of high energy accelerators in Japan from physics, technological and particularly social points of view referring to documents at KEK and other archives. This is the first of a series of papers and will outline the over-all view.
BNL, Upton, Long Island, New York
We report recent progresses on analytical studies of Coherent Electron Cooling. The phase space electron beam distribution obtained from the 1D FEL amplifier is applied to an infinite electron plasma model and the electron density evolution inside the kicker is derived. We also investigate the velocity modulation in the modulator and obtain a closed form solution for the current density evolution for infinite homogeneous electron plasma.
DESY, Hamburg
The problem of errors, arising due to finite BPM resolution in the reconstructed orbit parameters, is one of the standard problems of the accelerator physics. Even so for the case of uncoupled motion the covariance matrix of reconstruction errors can be calculated "by hand", the usage of the obtained solution, as a tool for designing of a "good measurement system", is not straightforward. A better understanding of this problem is still desirable. We make a step in this direction by introducing dynamics into this problem, which seems to be static. We consider a virtual beam obtained as a result of the application of a reconstruction procedure to ‘‘all possible values'' of BPM reading errors. This beam propagates along the beam line according to the same rules as any real beam and has all beam dynamical characteristics, such as emittances, dispersions, betatron functions, and all these values describe the properties of the BPM measurement system. As an application we formulate requirements for the BPM measurement system of high-energy intra-bunch-train feedback system of the European XFEL Facility in terms of the introduced concepts of error emittance and error Twiss parameters.
DESY, Hamburg
Università di Roma I La Sapienza, Roma
The control and stabilization of RF systems for accelerators has a considerable importance. In case of high-gain free-electron lasers (FEL) with magnetic bunch compressors, the RF phases determine the attainable bunch peak current, which is a relevant parameter for driving the FEL process. In order to measure the bunch peak current in a simple and fast but indirect way, both bunch compressors at FLASH are equipped with compression monitors (BCM) based on pyroelectrical detectors and diffraction radiators (CDR). They provide substantial information to tune the bunch compression and are used for beam-based feedback to stabilize RF phases. This monitor system becomes more important and more challenging after the installation of a third-harmonic RF system for longitudinal phase space linearization in front of the first bunch compressor. In this paper, we describe the hardware upgrade of the bunch compression monitor and show the expected performance by simulations of the CDR source and the radiation transport optics. Particle tracking simulations are used for generation of the simulated BCM-signal for various compression schemes. Comparison with experimental data will be presented.
ELETTRA, Basovizza
DEEI, Trieste
FERMI@Elettra is a soft X-ray fourth generation light source under construction at the ELETTRA laboratory. To characterize the beam phase space by means of measurements of the bunch length and of the transverse slice emittance two deflecting cavities will be positioned at two points in the linac. One will be placed at 250 MeV (low energy), after the first bunch compressor (BC1); the second at 1.2 GeV (high energy), just before the FEL process starts. The Low-Energy RF Deflector consists in a 5 cells, standing wave, normal conducting, RF copper cavity. A single ANSYS model has been developed to perform all of the calculations in a multi-step process. In this paper we discuss and report on results of electromagnetic, thermal, and structural analysis.
JASRI/SPring-8, Hyogo-ken
RIKEN/SPring-8, Hyogo
The University of Tokyo, Nuclear Professional School, Ibaraki-ken
We are developing a single-shot and non-destructive 3D bunch charge distribution (BCD) monitor based on Electro-Optical (EO) sampling with a manner of spectral decoding for XFEL/SPring-8. For fine beam tuning, 3D-BCD is often required to measure in real-time. The main function of this bunch monitor can be divided into longitudinal and transverse detection. For the transverse detection, eight EO-crystals surround the beam axis azimuthally, and a linear-chirped probe laser pulse with a hollow shape passes thorough the crystal. The polarization axis of the probe laser should be radially distributed as well as the Coulomb field of the electron bunches. Since the signal intensity encoded at each crystal depends on the strength of the Coulomb field at each point, we can detect the transverse BCD. In the longitudinal detection, we utilize a broadband square spectrum (> 400 nm at 800 nm of a central wavelength) so that the temporal resolution is < 30 fs if the pulse width of probe laser is 500 fs. In order to achieve 30-fs temporal resolution, we use an organic EO material, DAST crystal, which is transparent up to 30 THz. We report the first experimental results of this 3D-BCD monitor.
SINAP, Shanghai
A new beam profile diagnostic system based on industrial Ethernet has been installed in Shanghai Deep Ultraviolet Free Electron Laser (SDUV-FEL) facility recently. By choosing GigE Vision cameras, the system provides better image quality over a long distance than before. Beam images are captured from the beam profile monitors which are controlled by air cylinders or step motors. In order to fit for the system expansibility and curtail the cables, all devices are operated through the Ethernet and distributed along the FEL facility. The approach to the design of the hardware and software will be described in this paper. Applications and experiment results will be shown in this paper as well.
Diamond, Oxfordshire
University of Oxford, Clarendon Laboratory, Oxford
JAI, Oxford
Single shot emittance measurement is essential to assess the performance of new generation light sources such as linac based X-ray FELs or laser plasma wakefield accelerators. To this aim, we have developed a single shot emittance measurement using at least 3 screens inserted in the beam at the same time, measuring the beam size at different positions in a drift space in one shot. We present here test measurements performed at Diamond in the transfer line from the Booster to the Storage Ring, using thin OTR and also YAG screens. We also compare these measurements with results from the more conventional quadrupole scan method and also measurements using an OTR screen and an assembly of two cameras imaging the beam size and the beam divergence at a point near the waist of the beam. The validity and limits of the new method are discussed in the paper.
SLAC, Menlo Park, California
The talk will provide an overview of required feedback systems to guarantee stable and successful SASE operation as well as successful experiments. Recent developments and examples of various systems (including feedbacks for long bunch trains) will be discussed.
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.
LBNL, Berkeley, California
Stabilized optical fiber links have been under development for several years for high precision transmission of timing signals for remote synchronization of accelerator and laser systems. In our approach, a master clock signal is modulated on an optical carrier over a fiber link. The optical carrier is also used as the reference in a heterodyne interferometer which is used to precisely measure variations, mainly thermal, in the fiber length. The measured variations are used to correct the phase of the transmitted clock signal. We present experimental results showing sub-10 fsec relative stability of a 200 m link a sub-20 fsec stability of a 2.2 km link.
USTC/NSRL, Hefei, Anhui
A Photo-Cathode RF Gun is under development at NSRL. In this paper, the drive laser system is introduced and performance parameters are presented. We adopt a BNL type gun with laser illuminating the cathode at oblique incidence. To orrect 'time slew' and 'elliptical spot' problems arisen on the cathode, an adjustable optical transport line is designed.
I-Tech, Solkan
In this article we are presenting tests and development of digital low level RF control system Libera LLRF. Libera LLRF is a digital system small in size but powerful in terms of performance as tests revealed. Size of unit matches industrial standards and is in 19" 2U sustainable metal box that fits into racks. Development of the Libera LLRF reflects needs of accelerator's and their operators. With its capabilities it is a system that is able to control RF at 4th generation light sources. Concept of the Libera LLRF system also enables implementation of operator's own solutions in controlling RF. During preparations for testing Libera LLRF's features proved to be useful since little time was needed to install and operate the system. In some cases its features and capability enabled operators to identify and quickly resolve problems that were accelerator's components related.
INFN-Ferrara, Ferrara
UNIFE, Ferrara
IHEP Protvino, Protvino, Moscow Region
We present an analytical model to calculate the physical quantities of interest experienced by relativistic particles in their motion aligned with periodic complex atomic structures. Classical physics equations and the expansion of periodic functions as a Fourier series have been used for the calculation. This method allows calculating the contribution from all the planes and axes inside the crystal, in contrast to other simulation codes for which the motion is evaluated only on nearest neighbors atomic strings. Based on the calculation technique we have developed the "ECHARM" program, which allows calculating one- and two- dimensional averaged physical quantities of interest. The calculation holds for the main axes of any orthorhombic and tetragonal structures and for any orientation in the cubic structure. To underline the capability of the program, complex structures such as zeolites have been worked out. Based on the "ECHARM" code, simulation of the relativistic particle motion within complex structures has been developed. With this code it is possible to simulate the motion in bent crystal to study planar and axial channeling volume reflection.
RRCAT, Indore (M.P.)
BARC, Mumbai
Four and eight cell Plane Wave Transformer (PWT) linac structures have been developed as part of the injector development for the Compact Ultrafast Terahertz Free Electron Laser (CUTE-FEL) at RRCAT. In this paper, we discuss the tuning of resonant frequency and waveguide-cavity coupling coefficient for these structures, and compare results obtained from cold tests with those predicted by RF simulations. We also compare energy gain and RF properties of these structures, determined from transient and steady state behavior of the structure during recent high power tests, with those predicted by cold tests.
RRCAT, Indore (M.P.)
BARC, Mumbai
The injector system for the Compact Ultrafast Terahertz Free Electron Laser (CUTE-FEL) consists of a 1 ns, 90 kV pulsed thermionic electron gun, a 476 MHz sub-harmonic prebuncher, and a standing wave, S-band Plane Wave Transformer (PWT) linac capable of accelerating beam to 10 MeV. Beam from this injector will be transported to the entrance of the undulator through a beam transport line, with the required diagnostic elements, that has been designed, developed and commissioned. The control system and the low and high power microwave lines have also been commissioned. In this paper, we discuss salient features of the injector system and results from recent commissioning trials of the injector.
ASCo, Clayton, Victoria
ELETTRA, Basovizza
Monash University, Faculty of Science, Victoria
We report the development of an artificial intelligent system for the optimisation of electron beam parameters at the Australian Synchrotron Linac. The system is based on state of the art developments in Artificial Intelligence techniques for video games and is adapted here to beam parameters optimisation problems. It consists of a genetically evolved neural network that mimics an operator's decisions to perform an optimisation task when no prior knowledge other than constraints on the actuators is available. The system's decisions are based on the actuators positions, the past performance of close points in the search space and the probability of reaching a better performance in the local region of the search space.
Rome University La Sapienza, Roma
INFN/LNF, Frascati (Roma)
ENEA C.R. Frascati, Frascati (Roma)
LBNL, Berkeley, California
Velocity bunching (or RF compression) represents a promising technique complementary to magnetic compression to achieve the high peak current required in the linac drivers for FELs. Here we report on recent progress aimed at characterizing the RF compression from the point of view of the microbunching instability. We emphasize the development of a linear theory for the gain function of the instability and its validation against macroparticle simulations that represents a useful tool in the evaluation of the compression schemes for FEL sources.
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.
Kyoto IAE, Kyoto
UVSOR, Okazaki
RF gun has been chosen as injector for Kyoto University free electron laser because it can potentially produce an electron beam with high energy, small emittance, moreover inexpensive and compact configuration in comparison with other injectors. As for the RF gun cathode, thermionic cathode is simpler, easier to treat and reliable than photocathode. On the other hand, backbombardment electrons make cathode surface temperature and current density increase within the macropulse, as a result, beam energy and macropulse duration decrease, which means, it is difficult to generate stable FEL. The heating property of cathode not only depends on physical properties of the cathode material such as work function, but also backbombardment electrons energy. We investigated the heating property of six hexaboride materials against the backbombarding electrons by numerical calculation of the range and stopping power. In this investigation, the emission property of the cathode was also taken into account, since high electron emission is required for generation of high brightness electron beam. The results will be discussed.
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.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Cockcroft Institute, Warrington, Cheshire
JAI, Oxford
The design of free electron laser (FEL) driver needs careful beam transport design to pass very short bunches through the switchyard/spreader to switch the beam to different FEL lines. The spreader design which allows flexibility in operation has been adapted following the LBNL design*. In order to measure the slice properties of the bunches two beam diagnostics lines are proposed, a straight one for beam commissioning purposes and a branch of the spreader similar to the FEL lines to measure the adverse effects that may arise due to passing the short bunches through the kicker and septum magnets. As a part of machine protection, post linac collimation system collimates the halo particles in transverse and energy planes. The design of the collimation, beam spreader and beam diagnostics lines is discussed.
* Zholents A.A. et al, CBP Tech Note 401, 2009
SLAC, Menlo Park, California
LBNL, Berkeley, California
BNL, Upton, Long Island, New York
There are many simulation codes for accelerator modeling. Each one has some strength but not all. Collaboration is formed for the effort of providing a platform to host multiple modeling tools. In order to achieve such a platform, a set of common physics data structure has to be set. Application Programming Interface (API) for physics applications should also be defined within a model data provider. A preliminary platform design and prototype will be presented.
ELETTRA, Basovizza
PSI, Villigen
CERN, Geneva
FERMI@ELETTRA and PSI-XFEL are 4th Generation Light Sources that require high quality electron beam at the entrance of the undulator chains. In this context, a specially developed X-band structure with integrated alignment monitors will be used to mitigate the nonlinearities in the longitudinal phase space due to the second order RF time curvature and the second order momentum compaction term of chicane compressor. The knowledge of the transverse and longitudinal short range wakefields in the X-band structure is essential to evaluate the beam quality in terms of longitudinal energy spread and transverse kick spread. We have used the ABCI code to numerically evaluate the transverse and longitudinal wake potentials for short bunches in this structure.
ELETTRA, Basovizza
FERMI@ELETTRA is a single pass FEL Facility in construction at the ELETTRA Laboratory in Trieste. To linearize the beam longitudinal phase space, it is planned to use a short X-band accelerating structure installed before the first bunch compressor. Since both the end tubes of the structure have a reduced radius of 5.0 mm, much smaller than the 13.5 mm radius of the beam pipes before and after the structure, a transition, either stepped or tapered, will be necessary between the two components. Using the ABCI code, we have investigated the short range wake fields at the step-out and taper-out transitions and we have compared them with some conventional analytical models. We have developed specific ABCI-based analytical models that simulate accurately the short range wake field for a wide range of rms bunch lengths (σ: 100 - 1000μm).
ELETTRA, Basovizza
In most of the Linac based 4th Generation Light Sources now under development (e.g. FERMI@ELETTRA [1]), a short accelerating structure operating at higher harmonics (i.e. X-band, 12 GHz), is adopted to linearize the beam's longitudinal phase space [2]. This structure could be either travelling wave (TW) or standing wave (SW) type. As it is well known, each one of such structures has its own advantages and drawbacks in terms of RF properties but there is a lack of information about the wake fields of each type compared to the other. In this paper an overall comparison, from the wakefields point of view, of two different X-band structures will be carried out. The purpose is to evaluate quantitatively the longitudinal and transverse wake functions of the structures, determining their relevant wake integrals, such as the average value of energy loss, rms energy spread, kick factor and kick spread.
SINAP, Shanghai
A novel approach to producing coherent hard x-ray based on the echo-enabled staged harmonic generation (EESHG) scheme is proposed. This scheme is not a simple cascaded EEHG, but consists of an EEHG, a beam shifter and a conventional HGHG like configuration, which also works in the EEHG principle. In the first stage, all over the whole electron beam is energy modulated by a laser beam in the first modulator and then converts into separate energy bands by a very strong dispersion section. In the second modulator, the seed laser is adjusted so that only the tail half part of the e-beam is energy modulated, then this beam is sent through the second dispersion section which converts the energy modulated part into a density modulation. The radiation from the first stage serves as the seed laser of the second stage, the beam shifter is so tuned that the head part of the electron beam can exactly interact with the radiation from the first stage in the modulator of the second stage, so the total harmonic number will be hundreds. It is possible to do the proof-of-principle experiment of EESHG on the SDUV-FEL.
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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
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).
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.
JLAB, Newport News, Virginia
Jefferson Laboratory (JLab) is currently developing a new 500kV DC electron gun for future use with the FEL. The design consists of two inverted ceramics which support a central cathode electrode. This layout allows for a load-lock system to be located behind the gun chamber. The electrostatic geometry of the gun has been designed to minimize surface electric field gradients and also to provide some transverse focusing to the electron beam during transit between the cathode and anode. This paper discusses the electrode design philosophy and presents the results of electrostatic simulations. The electric field information obtained through modeling was used with particle tracking codes to predict the effects on the electron beam.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
STFC/DL, Daresbury, Warrington, Cheshire
ISP, Novosibirsk
ALICE is an Energy Recovery Linac built at STFC Daresbury Laboratory to investigate the process of energy recovery. The project is an accelerator research facility intended to develop the technology and expertise required to build a New Light Source (NLS) in the UK based on a suite of Free-Electron Lasers. Currently the ALICE gun accommodates only a single photocathode at any one time, and the system must be vented to atmospheric pressure for photocathode replacement. To meet the stringent vacuum demands for good photocathode lifetime, the system then requires baking for up to three weeks. A new load-lock cathode preparation system has been designed as an upgrade to the ALICE gun. The load-lock can accommodate up to six photocathodes, and permits rapid transfer of photocathodes between the load-lock activation chamber and the gun, thus maintaining the vacuum. The photocathode preparation facility was successfully commissioned in spring 2009, and has since permitted a quantum yield of 15% to be achieved at a wavelength of 635 nm. Presently, a new gun vessel and photocathode transport system is under manufacture, with a view to this being fully-installed on ALICE in Spring 2012.
DESY, Hamburg
CLASSE, Ithaca, New York
Uni HH, Hamburg
At FLASH an optical synchronisation system with femtosecond stability is now being installed and commissioned. The system is based on pulses from a passively modelocked fibre laser which are distributed in length-stabilised fibres to various end-stations. Several modifications and improvements with respect to the original layout, especially concerning permanent operation and reliability, are already incorporated at this stage. The electron bunch arrival-time monitors (BAM), based on electro-optical modulation, are an integral part of the system. Built on the experiences with first prototypes, the most recent version of the BAM, installed prior to the first bunch compressor, includes essential changes affecting the optical layout, the mechanical and thermal stability as well as the electronics for read-out and controls. The revised BAM showed improved performance and will be complemented by a second congenerous BAM after the first bunch compressor during the present FLASH upgrade. The experiences with installation as well as the scope of improvements as to simplification and long-term stability will be presented.
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).
BINP SB RAS, Novosibirsk
NSU, Novosibirsk
The Novosibirsk ERL has rather complicated magnetic system. One orbit (11-MeV) for terahertz FEL lies in the vertical plane. Other four orbits lie in the horizontal plane. The beam is directed to these orbits by switching on of two round magnets. In this case electrons pass through RF cavities four times, obtaining 40-MeV. At the 4th orbit the beam is used in FEL, and then is decelerated four times. At the 2nd orbit (20 MeV) we have a bypass with another FEL. When bypass magnets are switched on, the beam passes through this FEL. The length of bypass is chosen to provide the delay necessary to realize deceleration at the3rd pass through accelerating cavities. In 2008 two of four horizontal orbits were assembled and commissioned. The electron beam was accelerated twice and then decelerated down to low injection energy. First multi-orbit ERL operation was demonstrated successfully. In 2009 the first lasing at the second FEL, installed on the bypass of the second track, was achieved. The wavelength tunability range is 40 - 80 micron. Energy recovery of a high energy spread used electron beam was optimized. Third and fourth orbit assembly is in progress.
UVSOR, Okazaki
Nagoya University, Nagoya
KURRI, Osaka
Sokendai - Okazaki, Okazaki, Aichi
UVSOR, a 750 MeV synchrotron light source of 53m circumference had been operated for more than 20 years. After a major upgrade in 2003, this machine was renamed to UVSOR-II. The ring is now routinely operated with low emittance of 27 nm-rad and with four undulators. By utilizing a part of the existing FEL system and an ultra-short laser system, coherent synchrotron radiation in THz range and coherent harmonic generation in VUV range have been extensively studied under international collaborations. Based on results obtained from previous coherent light source developments, a new five-year research program on the coherent light source developments has been started from FY2008, which includes creation of a new 4-m long straight section by moving the injection point, upgrades of the undulator and the laser system and construction of dedicated beam-lines for these coherent light sources. Present status and upgrade plan on these coherent light sources at UVSOR-II will be presented at the conference.
UVSOR, Okazaki
Sokendai - Okazaki, Okazaki, Aichi
Nagoya University, Nagoya
UVSOR-II is a low emittance, 750 MeV synchrotron light source. Low emittance and low energy synchrotron light sources naturally suffered from short electron lifetime due to Touschek effect. Top-up operation is a solution for overcoming the effect. In the UVSOR-II, trials of multi-bunch top-up operation at the full energy were started from 2008. In the trials, we have succeeded in keeping the stored beam current around 300 mA for 12 hours. From this fiscal year, single bunch injection was started for single bunch user operations and for experiments on advanced light source development such as Free Electron Laser (FEL), Coherent Synchrotron Radiation (CSR), Coherent Harmonic Generation (CHG), which require single bunch or 2-bunch filling operation. We have already performed single bunch top-up operation in user time with the stored beam current of 50 mA. And FEL lasing with top-up operation was also achieved at the laser wavelength of 215 nm with the stored beam current of 130 mA / 2-bunch. In the FEL lasing experiment, we succeeded in keeping the average power of FEL around 130 mW for three hours.
Diamond, Oxfordshire
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
We present the progress with the design of the 2.25 GeV superconducting linac for the NLS project. We discuss the performance achieved, the optimisation strategies, the relevance of microbunching instability and the analysis of the effect of various jitter sources
LBNL, Berkeley, California
UCB, Berkeley, California
Recent reports have identified the scientific requirements for a future soft x-ray light source and a high-repetition-rate FEL facility responsive to them is being studied at LBNL. The facility is based on a CW superconducting linear accelerator with beam supplied by a high-brightness, high-repetition-rate photocathode electron gun, and on an array of FELs to which the beam is distributed, each operating at high repetition rate and with even pulse spacing. Dependent on the experimental requirements, the individual FELs may be configured for either SASE, HGHG, EEHG, or oscillator mode of operation, and will produce high peak and average brightness x-rays with a flexible pulse format ranging from sub-femtoseconds to hundreds of femtoseconds. We are developing a design concept for a 10‐beamline, coherent, soft x‐ray FEL array powered by a 2.5 GeV superconducting accelerator operating with a 1 MHz bunch repetition rate. Electron bunches are fanned out through a spreader, distributing beams to an array of 10 independently configurable FEL beamlines with nominal bunch rates up to 100 kHz. Additionally, one beamline could be configured to operate at higher repetition rate.
FEL/Duke University, Durham, North Carolina
The light source research program at the Duke Free-Electron Laser Laboratory (DFELL) is focused on the development of accelerator-driven light sources, including storage ring based free-electron lasers (FELs) and Compton gamma-ray source, the High Intensity Gamma-ray Source (HIGS). The HIGS is the most intense Compton gamma-ray source currently available with an energy tuning range from 1 to 100 MeV. The accelerator physics program at the DFELL covers a wide range of activities, from nonlinear dynamics research, to the study of beam instability with advanced feedback systems, to FEL research and development. In this paper, we will report our recent progress in accelerator physics research and light source development to meet new challenges of today's and future accelerators.
JASRI/SPring-8, Hyogo-ken
RIKEN/SPring-8, Hyogo
Fiber-based beam loss monitors (BLM) have attracted much attention in recent years. Among them, systems using the detection of the Cerenkov light generated by the secondary charged particles hitting an optical fiber set along the vacuum chamber, offer the possibility to detect beam losses with a very fast response time (less than a few ms) over long distances, good position accuracy and sensitivity at a reasonable cost. For the undulator section of the SPring-8 X-FEL, radiation safety considerations set the desirable detection limit at 1 pC (corresponding to a 0.1% beam loss of the initial 1 nC/pulse) over more than a hundred meter. We report on a the test operation of a fiber-based BLM carried out at the 250 MeV SPring-8 Compact SASE Source (SCSS), a 1/16th model of the future X-FEL. The expected detection limit of the BLM based on a large (400 μm) core multimode fiber is below 2 pC over 120 m (for a corresponding 10 mV signal) while the position accuracy is expected to be better than one meter.
RIKEN/SPring-8, Hyogo
JASRI/SPring-8, Hyogo-ken
A fiber-based beam loss monitors (BLM) is under development for the undulator section of the SPring-8 X-FEL: the system is based on the detection of the Cerenkov light generated by the secondary charged particles hitting an optical fiber set along the vacuum chamber. Various parameters come into account in the final performance of the system, such as the impact angle and energy of the lost electrons, the fiber position (angular and radial) with respect to the point of impact, fiber characteristics (numerical aperture, index, diameter), etc. Thorough numerical studies have been carried out to investigate the performances of the system. Comparison with the experimental results obtained at the SPring-8 Compact SASE Source (SCSS), a 1/16th model of the future X-FEL are also given.
University of Ljubljana, Faculty of Electrical Engineering, Ljubljana
I-Tech, Solkan
The new generation of accelerators requires timing distribution and RF synchronization with femtosecond precision in terms of jitter and long-term stability. The proposed electro-optical synchronization system makes use of commercial telecom single-mode optical fibre operating at 1550 nm.. It operates on over 300 m distance. It consists of a transmitter, located near a low-jitter master oscillator, and receiver, located at the remote location. The field experiments have been done in the accelerator environment with the fibre pair in the tunnel. The prototype units were installed at the same location to make phase difference measurement simple. Temperature in various installation points, phase difference and both units internal operational parameters were continuously monitored and stored. Data was post-analysed and conclusions were used for hardware changes and mostly the long-term stability improvement. A dedicated phase detector was designed to monitor less than 20 fs changes. Results are showing 80 fs RMS and 30 fs stability over 20 and 8 hours respectively. The prototype is being redesigned for manufacturing with some new features for improved long-term stability.
JLAB, Newport News, Virginia
JLab has designed and fabricated several prototype SRF cavities with cell shapes optimized for high current beams and with strong damping of unwanted higher order modes. We report on the latest test results of these cavities and on developments of concepts for new variants optimized for particular applications such as light sources and high-power proton accelerators, including betas less than one. We also report on progress towards a first beam test of this design in the recirculation loop of the JLab ERL based FEL. With growing interest worldwide in applications of SRF for high-average power electron and hadron machines, a practical test of these concepts is highly desirable. We plan to package two prototype cavities in a de-mountable cryomodule for temporary installation into the JLab FEL for testing with RF and beam. This will allow verification of all critical design and operational parameters paving the way to a full-scale prototype cryomodule.
Uni HH, Hamburg
DESY, Hamburg
ANL, Argonne
A seeded free-electron laser (FEL) experiment at VUV wavelengths, called sFLASH, is being prepared at the existing SASE FEL user facility FLASH. Seed pulses at wavelengths around 35 nm from high harmonic generation (HHG) will interact with the electron beam in sFLASH undulators upstream of the existing SASE undulator section. In this paper the tuning results and performance of the sFLASH undulators are presented.
ELETTRA, Basovizza
RIAL VACUUM S.p.A, Parma
The FERMI@Elettra project at the ELETTRA Laboratory of Sincrotrone Trieste (ST), currently under construction, will be comprised of a linear accelerator and two Free-Electron-Laser beamlines (FEL1, FEL2). In order to deliver high-intensity VUV and soft X-ray pulses, permanent magnet undulators with 9 mm minimum variable gap will be used. The adopted vacuum chambers will have a 7 by 25 mm2 elliptical internal cross-section. While manufacturing the vacuum chamber in aluminum helps reducing the resistive wall wakefield effects, the chamber inner wall surface quality is strongly correlated to the surface roughness wakefield component. We report on the results of the study to improve the wall surface finish and lower the roughness periodicity. The chamber manufacturing status and its alignment mechanism is also presented.
Kyoto IAE, Kyoto
Aiming at realizing a short period undulator with strong magnetic field, we have proposed a Bulk HTSC (high temperature superconductor) Staggered Array Undulator which consists of bulk high temperature superconductor magnets with a staggered array configuration. The experiment with the prototype undulator at 77 K shows this configuration can be applicable to real undulator. We also estimated the magnetic performance of real device by calculations with a loop current model based on Bean model of superconductor. Although end field termination is required for practical use, traditional methods are not applicable for the bulk HTSCs. We found that the end field termination can be realized by controlling the shape and size of bulk HTSCs at the end section by numerical calculation using the loop current model. In the conference, the calculation and experimental result of end field termination will be presented.
ISIR, Osaka
KEK, Ibaraki
The edge-focusing (EF) wiggler has been fabricated to evaluate its performance rigorously with the magnetic field measurement. It is a 5-period planar wiggler with an edge angle of 2° and a period length of 60 mm. The magnetic field is measured using Hall probes at four different wiggler gaps. It is experimentally confirmed that a high field gradient of 1.0 T/m is realized, as designed, along the beam axis. The magnetic field gradient of the EF wiggler is derived as a function of the magnetic gap. The field gradient decreases with increasing magnet gap more slowly than the peak magnetic field does for the present experimental model. An analytic formula for the field gradient of the EF wiggler is derived and it is shown that the slope of the field gradient with the magnet gap can be changed by varying the magnet width of the EF wiggler. We analyzed the relation between the orientation errors of the measurement system and the measured magnetic field or field gradient using a model magnetic field of the EF wiggle. We corrected the measurement magnetic field based on this analysis and evaluated the performance of the EF wiggler.
USTC/NSRL, Hefei, Anhui
The enhancement of arbitrary odd harmonic field is analyzed for pure permanent magnet undulator. The two dimensional analytical formula of the magnetic field is given for a modified Harbch type undulator, in which the magnet blocks have different size. It is shown that the odd harmonic field can be enhanced by optimal the length ratio of the vertical magnetized magnet blocks and the horizontal magnetized magnet blocks, the 3rd harmonic field can exceeded 20% of the fundamental field and 7th harmonic field can exceeded 3 % of the fundamental field for magnet gap-period ratio equal to 0.1.
BNL, Upton, Long Island, New York
Various magnet sorting strategies have been used to minimize trajectory and phase errors in undulators, ranging from intuitive pairing of stronger and weaker magnets, to full 3D FEM simulation with actual Helmholtz coil magnet data. We present a simpler approach, first deriving trajectory displacement, kick angle and phase error signatures of each component of magnetization error from a 3D Radia* undulator model. Then, for a given sequence of magnets, the trajectory and phase profiles are computed by cumulatively summing the scaled displacements and phase errors. The rms error is then minimized by swapping magnets according to one's favorite optimization method. A fast, simple magnet swapping algorithm, implemented in Mathematica, is described. 100,000 iterations take only minutes, so dozens of solutions can be compared. This approach was applied recently at NSLS to a short in-vacuum undulator, which required no trajectory or phase shimming. We also obtain trajectory and phase error signatures of some mechanical errors, to guide "virtual shimming" and specifying mechanical tolerances. Finally, multipole signatures of some simple inhomogeneities are modeled.
* O. Chubar, P. Elleaume, J. Chavanne, "A 3D Magnetostatics Computer Code for Insertion Devices", SRI97 Conference August 1997, J. Synchrotron Rad. (1998). 5, 481-484
RadiaBeam, Santa Monica
Purdue University, West Lafayette, Indiana
Of particular interest to X-ray FEL light source facilities is Enhanced Self-Amplified Spontaneous Emission (ESASE) technique. Such a technique requires an ultrafast (20-50 fs) high peak power, high repetition rate reliable laser systems working in the mid-IR range of spectrum (2μm or more). The approach of this proposed work is to design a novel Ultrafast Mid-IR Laser System based on optical parametric chirped-pulse amplification (OPCPA). OPCPA is a technique ideally suited for production of ultrashort laser pulses at the center wavelength of 2 μm. Some of the key features of OPCPA are the wavelength agility, broad spectral bandwidth and negligible thermal load.
PSI, Villigen
In accelerator applications, high precision high speed power supplies (PSs) for magnets are needed to guarantee the high beam quality. These PSs are the main purpose of the presented second generation of a Digital Power Electronic Control System (DPC) which has been designed and successfully applied at the Paul Scherrer Institute PSI. The main components of the DPC are the controller board (DPC_CC) and the high precision analogue to digital converter board (DPC_AD). Compared to the first generation the properties such as precision, acquisition rate, processing power and functionality have been improved considerably. This allows faster control cycles and/or more complex control algorithms. The controller board now features 12 standard precision (16 bit) ADC channels and allows the simultaneous control of multiple power supplies. High precision requirements are met by adding the DPC_AD to the system. In conclusion, the modular and flexible design allows well-matched solutions for the typically heterogeneous accelerator power supplies.
LBNL, Berkeley, California
The Next Generation Light Source (NGLS) at Lawrence Berkeley Laboratory is a 2.4 GeV linear accelerator with up to ten FELs. Each of the FELs require a fast kicker, with the exception of the final one which can use a normal bend magnet. The requirements for the kickers are to deflect the linac beam by an angle of 3 mrad with a magnetic length of 2 m, and an aperture size of 17 by 17 mm. A strip line magnet with an impedance of 50 Ohms being feed from the opposite direction as the beam has been selected for prototyping. The modulator requirements to drive such a magnet are ±15 kV and ±300 A, with rise and fall times of 5 ns and a flat top of 10 ns. The pulse to pulse stability must be better than 0.01% of the peak value. The design of the modulator is an inductive adder with 20 cells, each driven by 12 power MOSFETs. This paper describes details of the design as well as present preliminary test data.
RRCAT, Indore (M.P.)
BARC, Mumbai
Tuning of a photocathode gun for desired RF properties of the pi mode, such as FB ~1, fpi = 2856 MHz, and beta ~1, requires precise tuning of the resonant frequency and beta of its independent cells. In this paper, we present a parametric and analytical formulation to predict geometrical dimensions of independent cells and the coupling slot on the full cell to obtain the desired pi mode RF parameters during operation, taking into account the effect of brazing and vacuum. We also compare results obtained from low power RF measurements on a photocathode gun with those predicted by the above formulation.
INFN/LNF, Frascati (Roma)
Istituto Nazionale di Fisica Nucleare, Milano
Rome University La Sapienza, Roma
ENEA C.R. Frascati, Frascati (Roma)
In the frame of the SPARC-X project, the energy of the Photo-Injector SPARC, in operation at INFN-LNF, will be upgraded from 180 to 250 MeV by replacing a low gradient S-band traveling wave accelerating section with two C-band units, designed and developed at LNF. The new system will consist of a 50 MW klystron, supplied by a pulsed modulator, to feed the high gradient C-band structures through a RF pulse compressor. This paper deals with the design of the full system, the C-band R&D activity and study of the related beam dynamics.
Rome University La Sapienza, Roma
RadiaBeam, Marina del Rey
UCLA, Los Angeles, California
INFN/LNF, Frascati (Roma)
The quest for high brightness beams is a crucial key for the SPARX-FEL Project. In this paper, we present the design (including RF modeling, cooling, thermal and stress analyses as well as frequency detuning) of a single feed S-Band RF Gun capable of running near 500 Hz. An alternative design with dual feed has already been designed. Also, experimental results from the RF characterization of the prototype, including field measurements, are presented. The RF design follows the guidelines of the LCLS Gun, but the approach diverges significantly as far as the management of the cooling and mechanical stress is concerned. Finally, we examine the new proprietary approach of RadiaBeam Technologies for fabricating copper structures with intricate internal cooling geometries that may enable very high repetition rate.
* C.Limborg et al., "RF Design of the LCLS Gun".
** P. Frigola et al., "Development of solid freeform fabrication (SFF) for the production of RF Photoinjectors".
DESY, Hamburg
Building an accelerator facility brings together civil construction and mechanical engineering, two trades with very different working cultures, practices and tool sets: While construction sites are traditionally paper-based and 2D oriented, the accelerator and its infrastructure are completely modeled in 3D. At the European XFEL, methods and tools known from plant construction were introduced to civil construction to enable efficient collaboration of all trades. Integrated 3D models encompass design models of all technical subsystems. An electronic "XFEL room book" captures requirements and manages assignments of space, infrastructure and equipments in the buildings. The DESY Engineering Data Management System (EDMS) manages and links the information with additional documentation. Electronic workflows coordinate e.g. reviews and change management. 3D models, room book and documentation databases together constitute the so-called "Building Information Model" (BIM). The BIM addresses the entire building lifecycle and is a basis for later facility operation. The poster describes information management procedures, tools and experience in the civil construction of the European XFEL.
UCLA, Los Angeles, California
SLAC, Menlo Park, California
INFN/LNF, Frascati (Roma)
Penn State University, University Park, Pennsylvania
USC, Los Angeles, California
Recent initiatives at UCLA concerning ultra-short, GeV electron beam generation have been aimed at achieving sub-fs pulses capable of driving X-ray free-electron lasers (FELs) in single-spike mode. This uses of very low charge beams, which may allow existing FEL injectors to produce few-100 attosecond pulses, with very high brightness. Towards this end, recent experiments at the Stanford X-ray FEL (LCLS, first of its kind, built with essential UCLA leadership) have produced ~2 fs, 20 pC electron pulses. We discuss here extensions of this work, in which we seek to exploit the beam brightness in FELs, in tandem with new developments at UCLA in cryogenic undulator technology, to create compact accelerator/undulator systems that can lase below 0.15 Angstroms, or be used to permit 1.5 Angstrom operation at 4.5 GeV. In addition, we are now developing experiments which use the present LCLS fs pulses to excite plasma wakefields exceeding 1 TV/m, permitting a table-top TeV accelerator for frontier high energy physics applications.
DESY, Hamburg
Fermilab, Batavia
Uni HH, Hamburg
Ultra short bunches with high peak current are required for efficient creation of high brilliance coherent light at the free electron laser FLASH. They are obtained by a two stage transverse magnetic chicane bunch compression scheme based on acceleration of the beam off the rf field crest. The deviation of the rf field's sine shape from a straight line leads to long bunch tails and reduces the peak current. This effect will be eliminated by adding the Fermilab-built third harmonic superconducting accelerating module operating at 3.9 GHz to linearize the rf field. The third harmonic module also allows for the creation of uniform intensity bunches of adjustable length that is needed for seeded operation. This paper summarizes the results from the first complete rf system test at the crymodule test bench at DESY and the first experience gained operating the system with beam in FLASH.
SDU, Isparta
Ankara University, Faculty of Engineering, Tandogan, Ankara
Gazi University, Faculty of Arts and Sciences, Teknikokullar, Ankara
Ankara University, Faculty of Sciences, Tandogan/Ankara
Dumlupinar University, Faculty of Science and Arts, Kutahya
The status and road map of Turkish Accelerator Center (TAC) project is explained. TAC project is in third phase after feasibility and conceptual design phases with support of State Planning Organisation (SPO) of Turkey that the main aim of this phase is to complete of technical design report of TAC and to establish the first (test) facility. The first facility is planned as superconducting electron linac based IR FEL and bremsstrahlung facility. Third phase will be completed in 2013. It is planned that TAC will include a linac on ring type electron positron collider as a super charm factory, third and fourth generation light sources (SR and SASE FEL) and a proton facility. TAC collaboration is an inter-university collaboration of ten Turkish Universities under the coordination of Ankara University and TAC is a national project with international collaboration. In this study, the status of the project and the road map is explained with some results from design and construction studies.
DESY, Hamburg
A straight drift-quadrupole system, though not being an achromat, can transport certain incoming beam ellipses without introducing first-order chromatic distortions. Several examples of such apochromatic beam transport are available in the literature. In this paper we show that the possibility of apochromatic focusing is a general property: For every drift-quadrupole system there exist an unique set of Twiss parameters (apochromatic Twiss parameters), which will be transported through that system without first order chromatic distortions. Moreover, we prove that at the same time the apochromatic Twiss parameters bring the second order effect of the betatron oscillations on the shift of the average bunch path length to the minimal possible value and also minimize the effect of betatron oscillations on bunch lengthening for Gaussian beam. As an example we consider the application of the apochromatic focusing concept to the design of matching sections and phase shifter of the post-linac collimation section of the European XFEL Facility.
DESY, Hamburg
An achromat is a focusing system, in which as large a number of higher order aberrations as possible is canceled by symmetries of the linear optics and the rest is corrected by the usage of third and higher order multipoles. The first achromats ever considered were repetitive achromats, in which the cancellation of higher order aberrations relies on appropriate selection of cell tunes. Later on achromats, employing mirror symmetry, were also developed. In this paper we remove one superfluous constraint on the linear optics in the theory of four cell mirror symmetric achromats, make an accurate consideration of two cell repetitive achromats, and compare the number of multipoles required for each of those achromats. Moreover, we contribute a point of view, from which both approaches to the achromat design become identical. As a practical application we consider the design of the arcs of the post-linac collimation section of the European XFEL Facility.
ELETTRA, Basovizza
The 4th Generation Light Source FERMI@ELETTRA, in construction at the ELETTRA Laboratory in Trieste, requires very short electron bunches at the entrance of the undulator chain. To linearize the longitudinal phase space in the presence of the compression process, a 4th harmonic decelerating section (11992 MHz) will be installed before the first magnetic chicane. An X-band structure, with integrated alignment monitors [1], is currently under development in the framework of collaboration between CERN-PSI-ELETTRA. In this paper we will present a full longitudinal and transversal beam dynamics of the electron beam along the X-band structure during linearization process using 3D space charge code TStep [2]. Beam dynamics simulations will also be continued along the whole FERMI linac using elegant code [3].
NSC/KIPT, Kharkov
In a 1956 article* Panofsky and Wenzel derived the relation for the net transverse kick experienced by a fast charge particle crossing a closed cavity excited in a single rf mode. Later on this relation, usually referred to the Panofsky-Wenzel theorem, was generalized for cavity containing wake field induced by a driving charge. This theorem has played very important role in the accelerator physics. One well-known conclusion of this paper was that in a TE mode the deflecting impulse of the electric field always cancels the impulse of the magnetic fields. In our presentation we more exactly rederive Panofsky and Wenzel's result and obtain correction terms to the transverse kick. We show that in a TE mode the net transverse kick does not zero but is determined by a ponderomotive force. Using the given approach we find correction terms to wake potentials which are inversely proportional to the relativistic factor. Practical implications of our results are discussed.
* W.K.H. Panofsky and W.A. Wenzel, Rev. Sci. Instrum. 27, 967 (1956).