ANL, Argonne
Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source (APS) is a third-generation storage-ring-based x-ray source that has been operating for more than 11 years and is enjoying a long period of stable, reliable operation. While APS is presently providing state-of-the-art performance to its large user community, we must clearly plan for improvements and upgrades to stay at the forefront scientifically. Significant improvements should be possible through upgrades of beamline optics, detectors, and end-station equipment, along with local, evolutionary changes to the storage ring itself. However, major accelerator upgrades are also being investigated. One very promising option that has been the subject of considerable research is the use of an energy recovery linac. In this option, APS would transition from a source based on a stored electron beam to one based on a continuously generated high-brightness electron beam from a linac. Such a source promises dramatically improved brightness and transverse coherence compared to third-generation storage rings, as well as distinctly different temporal properties.
SINAP, Shanghai
The Shanghai Synchrotron Radiation Facility (SSRF) is an intermediate energy, third generation light source. In December 2007, electron beam was stored and accumulated in the SSRF storage ring. Since then the accelerator commissioning and beam line installation have continued toward the scheduled user operation from May 2009 onwards. This paper presents an overview of the SSRF status and preparations for user operations.
BINP SB RAS, Novosibirsk
The first stage of Novosibirsk high power free electron laser (FEL) is in operation since 2003. Now the FEL provides average power up to 500 W in the wavelength range 120 - 240 micron. One orbit for 11-MeV energy with terahertz FEL lies in 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 four times through accelerating RF cavities, obtaining 40-MeV energy. Then, (at fourth orbit) the beam is used in FEL, and then is decelerated four times. At the second orbit (20 MeV) we have bypass with third FEL. When magnets of bypass are switched on, the beam passes through this FEL. The length of bypass is chosen to provide the delay, which necessary to have deceleration instead of acceleration at the third passage through accelerating cavities. Now two of four horizontal orbits are assembled and commissioned. The electron beam was accelerated twice and then decelerated down to low injection energy. Project average current 9 mA was achieved. First multi-orbit ERL operation was demonstrated successfully.
CLASSE, Ithaca, New York
Fermilab, Batavia
Cornell University is planning to build an Energy-Recovery Linac (ERL) X-ray facility. In this ERL design, a 5 GeV superconducting linear accelerator extends the CESR ring which is currently used for the Cornell High Energy Synchrotron Source (CHESS). Here we describe some of the recent developments for this ERL, including linear and nonlinear optics, tracking studies, vacuum system design, gas and intra beam scattering computations, and collimator and radiation shielding calculations based on this optics, undulator developments, optimization of X-ray beams by electron beam manipulation, technical design of ERL cavities and cryomodules, and preparation of the accelerator site.
ANL, Argonne
HSRC, Higashi-Hiroshima
Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
In the selection of a new insertion device optimized for producing intense soft x-rays at the Advanced Photon Source, two different types of circular polarizing quasi-periodic undulators were studied. The magnetic structure of the undulators consists of pure permanent magnets for one of the undulators (an APPLE-II style undulator) and of electromagnets and pole pieces for the other type. The undulator period lengths were chosen so that the first harmonic energy occurs at 200 eV in linear horizontal polarization mode and at 400 eV in both linear vertical and circular polarization modes. Calculations of on-axis brilliance and on-axis flux spectra for both types of undulators and reductions of the spectral harmonics due to quasi-periodicity are presented. The introduction of quasi-periodicity of the magnetic fields shifts the higher spectral harmonics to a lower energy, hence reducing the so-called higher-order contamination dramatically. At the same time however, it reduces the first harmonic intensity by 20 40%. The non-sinusoidal shape of the horizontal and vertical magnetic fields of the electromagnetic undulator at high K values enhances the intensity of the first harmonic.
ANL, Argonne
Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
A superconducting planar undulator is under development at the Advanced Photon Source (APS). The initial R&D phase of the project includes intensive magnetic modeling performed with the Opera 2d and 3d software packages. This simulation addresses questions of magnetic design of the undulator including calculation of peak field on the undulator axis and maximum field in the conductor, superconductor load line optimization, and design of the undulator ends and correction coils. Results of the magnetic simulation are presented in the paper.
ANL, Argonne
Fermilab, Batavia
Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
An extensive R&D program is underway at the Advanced Photon Source (APS) with the aim of developing a technology capable of building a 2.4-m-long superconducting planar undulator for APS users. The initial phase of the project concentrates on using a NbTi superconductor and includes magnetic modeling, development of manufacturing techniques for the undulator magnet, and design and test of short prototypes. The current status of the R&D phase of the project is described in this paper.
ANL, Argonne
HSRC, Higashi-Hiroshima
Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
A request from the light source user community for insertion devices that provide only monochromatic light has led to development of quasi-periodic undulators (QPUs). These devices generate shifted harmonics in the photon energy spectrum, thus allowing suppression of higher harmonics by optical monochromator systems. Until now such undulators have been technically realized with pure permanent magnets or with hybrid structures. A concept for a superconducting quasi-periodic undulator (SCQPU) is suggested and described in this paper.
ANL, Argonne
Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under contract number DE-AC02-06CH11357.
Investigation into a circular polarizing quasi-periodic undulator is presented here. Electromagnets are used to generate the vertical field. Permanent magnets are used to generate the horizontal field. Calculated maximum effective vertical and horizontal magnetic fields on the undulator axis higher than 8.5 kGauss are achieved at a 10.5-mm gap for a 9-cm-period undulator. Fields of this magnitude are difficult to achieve in purely electromagnetic devices. Switching the sign of the current for the vertical field electromagnets allows for right- or left-handed circular polarization. A laminated core can be introduced to allow for fast helicity switching in order to utilize lock-in detection techniques. Quasi-periodicity can be introduced in the vertical electromagnet field by reducing the current at the quasi-periodic poles and can be turned on, off, or somewhere in between. Quasi-periodicity can be introduced in the horizontal permanent magnet field by inserting weakened magnets at the quasi-periodic poles. Since it is built into the magnet structure, this quasi-periodicity cannot be turned off.
ANL, Argonne
Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The baseline configuration of the proposed International Linear Collider includes superconducting helical undulators as a scheme to produce positrons. This paper presents a conceptual design of the magnetic field measurement system for helical undulators with the undulator axis in a horizontal direction at liquid helium temperature. The system consists of a cryomodule and a linear stage unit with a travel length of approximately 3.5 m. The linear stage unit provides the motion control for the Hall probe housing, which is connected to a small-diameter carbon fiber rod inside bellows-flange connections. Stainless steel bellows are at the same vacuum pressure as the cold mass in the cryomodule. A linear encoder is used for motion control of the stage, but precise position measurement of the Hall probe relies on the laser interferometer system.
CLASSE, Ithaca, New York
Funding: Work supported by National Science Foundation under contract DMR 0225180
The paper describes the design as well as short prototype and the prototype test result of undulator magnet planned for use in Cornell Energy Recovery Linac. The prototype has pure permanent magnet (PPM) structure with 24mm period, 5mm diameter round gap and is 30cm long. In comparison with conventional undulator magnets it has: a) full X-ray polarization control; b) 40% stronger magnetic field in linear and approximately 2 times stronger in circular polarization modes; c) compactness. These advantages were achieved through a number of non-conventional approaches. Among them is control of the magnetic field strength via longitudinal motion of the magnet arrays. The moving mechanism is also used for x-ray polarization control. The compactness is achieved using a recently developed permanent magnet soldering technique for fastening PM blocks. We call this device a "Delta" undulator after the shape of it's PM blocks.
ESRF, Grenoble
SOLEIL, Gif-sur-Yvette
Cryogenic Permanent Magnet Undulators (CPMU) are currently being developed in some Synchrotron Light Sources. Low Temperature NdFeB Permanent Magnets are used to achieve both a high remanence and a high coercive field. Low temperature magnetization hysteresis curves cannot be obtained by a simple transformation of ambient temperature curves; this requires a specific simulation tool. A Monte-Carlo based Permanent Magnet Simulator has been developed at the ESRF. In this simulator, the magnets can be described as a set of several magnetic grains. The model inputs are physical parameters such as anisotropy constants, easy-axis distribution and coercive field. The orientation of magnetic moments are calculated for each grain according to an analytical model and optimization methods are used for fast computations. Magnetization versus external field curves is calculated in a few seconds. This fits with low temperature NdFeB magnetization measurements. These curves have been efficiently used to obtain Radia material parameters for CPMU design.
FZK, Karlsruhe
INFN/LNF, Frascati (Roma)
Max-Planck Institute for Metal Research, Stuttgart
Recent investigations with the cold bore superconducting undulator installed at ANKA indicate that the main contribution to the beam heat load is caused by electron bombardment. For a quantitative understanding of the problem a cold vacuum chamber for diagnostics has been designed. Among other important parameters (heat load, pressure, etc) this device shall monitor the spectrum of the low energy electrons bombarding the wall. In this contribution we report on the measurements of the spectrum of the low energy electrons bombarding the wall of the cold vacuum chamber in a room temperature region of the ANKA storage ring performed using a in house developed retarding field analyzer (RFA). The calibration of the RFA performed at the national laboratories of Frascati is also described.
LBNL, Berkeley, California
Funding: This work is supported by the Director, Office of Science, U. S. Department of Energy under Contract No. DE-AC02-05CH11231.
In 2006, the 30mm period In-Vacuum Insertion Device (IVID) was operational for the femtosecond phenomena beamline at the Advanced Light Source (ALS) of Lawrence Berkeley National Laboratory. Since then the IVID has been demonstrating unexpected behaviors especially at small gaps (minimum gap = 5.5mm). The main observations related to these issues are partial or total beam losses as well as sudden pressure increases while operating the IVID gap. This paper is reporting these observations and describes the investigations and the repair attempt performed on this insertion device.
SLAC, Menlo Park, California
The LCLS project at SLAC requires 40 undulators be tuned, fiducialized, and a final data set taken. The techniques used to do this work are presented. In addition, the quadrupoles between the undulators must be accurately fiducialized. A description of the quadrupole magnetic measurements and fiducialization is also presented.
University Erlangen-Nurnberg, Institute of Condensed Matter Physics, Erlangen
BNG, Würzburg
FZK, Karlsruhe
University Erlangen-Nuernberg, Institute of Condensed Matter Physics, Erlangen
A new 15 mm period, 1.5 m long planar undulator is being fabricated by Babcock Noell GmbH (BNG) for the ANKA synchrotron light source. In order to qualify the production process and to optimize both the quench protection scheme and the magnetic field correction system, a short prototype has been fabricated. The prototype has been tested in vertical configuration and liquid helium at 4.2K in the CASPER facility at ANKA. The magnetic field has been measured along the beam axis direction by Hall probes with a positioning precision of 3 μm. We report here on the field shimming scheme and the resulting performance of the coils.
ISSP/SRL, Chiba
JASRI/SPring-8, Hyogo-ken
RIKEN Spring-8 Harima, Hyogo
A 27-m polarization-controlled undulator that consists of four horizontal and four vertical figure-8 undulator segments and seven phase shifters will be installed at SPring-8 as the most highly brilliant soft x-ray source for the material science beamline of the University of Tokyo. Each phase shifter controls the radiation phase between undulator segments by giving a bump orbit to the electron beam with its magnetic field to generate horizontal, vertical and circular polarization states. High reproducibility and stability of the phase control and fast helicity switching of the circular polarization radiation are required for the phase shifter. We designed and fabricated a phase shifter prototype to satisfy these requirements. The phase shifter prototype consists of three H-type dipole magnets and the yokes are made of 0.1-mm-thick permalloy laminations united and insulated by varnish. Various field measurements of the prototype were performed to evaluate the performance. In this paper, we will present the phase shifter prototype for the 27-m polarization-controlled undulator and its performance.
ESRF, Grenoble
This paper outlines the present status and configuration of the ESRF vacuum system and its performance over the last years. A short overview of the installed vacuum devices is given as well as an outlook of future developments towards the planned ESRF upgrade. The storage ring down times caused by vacuum accidents have been dramatically improved due to a systematical survey using advanced vacuum diagnostic tools. Their use and drawbacks will also be discussed in this paper.
Durham University, Durham
Cockcroft Institute, Warrington, Cheshire
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
DESY Zeuthen, Zeuthen
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
The University of Liverpool, Liverpool
Energy deposition in the conversion targets of positron sources for future linear colliders will lead to thermal shock waves which could limit the targets' lifetimes. For the International Linear Collider baseline source, we have studied the energy deposition in a target taking the higher harmonics of the undulator radiation fully into account and applying hydrodynamical models for the resulting heat flow to determine the thermal stress in the target and to assess its survivability.
The University of Liverpool, Liverpool
Cockcroft Institute, Warrington, Cheshire
A model has been created in Geant4 to simulate the key elements of an undulator-based positron source for CLIC: the goal is to consider such a source as an alternative to the present baseline concept. The parameters of the undulator and capture device have been optimized for a range of operating scenarios. In each case we have calculated the rate of positron production, positron polarization and capture efficiency. We discuss the strengths and weaknesses of the undulator scheme in CLIC.
The University of Liverpool, Liverpool
Cockcroft Institute, Warrington, Cheshire
An undulator-based source has been chosen as a part of the baseline configuration for the International Linear Collider (ILC) to generate an intense beam of polarised positrons. A photon collimator placed between the undulator and the target can be used to adjust the size, intensity and polarisation of the photon beam impacting the target, and can also protect the target station and limit the activation of downstream components. In this paper, we calculate quantities such as the energy deposition, temperature change, activation and dose rate for different designs of the photon collimator, and consider the advantages and disadvantages for each case.
USTRAT/SUPA, Glasgow
Cockcroft Institute, Warrington, Cheshire
Pulsar Physics, Eindhoven
Funding: The U.K. EPSRC and the European Community - New and Emerging Science and Technology Activity under the FP6 “Structuring the European Research Area” programme (project EuroLEAP, contract number 028514)
The Advanced Laser-Plasma High-Energy Accelerators towards X-rays (ALPHA-X) programme* is developing laser-plasma accelerators for the production of ultra-short electron bunches as drivers of incoherent and coherent radiation sources from plasma and magnetic undulators. Focusing of ultra-short electron bunches from a laser-plasma wakefield accelerator into an undulator requires that particular attention be paid to the electron beam quality. We will discuss the design and implementation of an upgraded focusing system for the ALPHA-X beam line, which currently consists of a triplet of electromagnet quadrupoles. The upgrade will comprise the installation of additional compact permanent quadrupoles** very close to the accelerator exit. This will improve the matching of the beam into the undulator. The design has been carried out using the General Particle Tracer (GPT) code*** and TRANSPORT code, which consider space charge effects and allow a realistic estimate of electron beam properties inside the undulator to be obtained. We will present a study of the influence of beam transport on free-electron laser action in the undulator, paying particular attention to bunch dispersion.
* D. Jaroszynski et al., Phil. Trans. R. Soc. A 364, 689-710 (2006)
** T. Eichner et al., Phys. Rev. ST Accel. Beams 10, 082401 (2007)
*** S.B. Geer, M.J. Loos, Ph.D. thesis, TU/e, Eindhoven (2001)
SLAC, Menlo Park, California
ANL, Argonne
Funding: Work supported by U.S. Department of Energy under Contract Nos. DE-AC02-06CH11357 and DE-AC02-76SF00515.
We present the performance of the cavity beam position monitor (BPM) system for the LCLS undulator. The construction and installation phase of 34 BPMs for the undulator and 2 for the transport line have been completed. The X-band cavity BPM employs a TM010 monopole reference cavity and a TM110 dipole cavity designed to operate at a center frequency of 11.384 GHz. The signal processing electronics features a low-noise single-stage three-channel heterodyne receiver that has selectable gain and a phase locking local oscillator. The approximately 40 MHz IF is digitized by a 120M sample/second four-channel 16-bit digitizer. System requirements include sub-micron position resolution for a single-bunch beam charge of 200 pC. We discuss the system specifications and commissioning results.
RIKEN/SPring-8, Hyogo
JASRI/SPring-8, Hyogo-ken
We report the high power rf test results of C-band accelerator system for X-ray free electron laser (XFEL) in SPring-8. The C-band accelerator system is composed of two C-band accelerator of Choke-mode-type HOM damping structure, the rf pulse compressor, the 50 MW klystron, oil-filled modulator and solid state switching high voltage charger. It is designed to operate at rather high accelerating gradient as high as 35 MV/m, therefore it is crucial to evaluate high gradient performance and reject some component with defect or poor performance. In the 8 GeV main accelerator, 64 C-band systems will be used in total, whose components are under mass production at several industries in Japan. Some of these systems have been installed and tested in high-power test bunker since July 2008. We report on statistics of the high voltage breakdown, and related measurement; such as power calibration of klystron 50 MW, gain measurement on rf pulse compressor.
CLS, Saskatoon, Saskatchewan
Upgrades to the orbit control system at the Canadian Light Source (CLS) have resulted in increased beam stability and reproducibility. These upgrades include improving position information from the beam position monitors (BPMs) by modifying the data acquisition algorithm and switching to a real-time operating system. Beam motion has been reduced to an RMS deviation of less than 1 micron in both planes. Limiting the maximum corrector step has allowed the use of all singular values when inverting the BPM response matrix, resulting in much better orbit reproducibility. As well, improved lookup tables have been developed to compensate for the effects of changing undulator gaps and polarizations. Presently, work is underway to develop fast orbit correction with rates up to 100 Hz. Fast orbit correction will further reduce the residual perturbations caused by undulator activity and will allow fast ramping of superconducting wigglers.
CLASSE, Ithaca, New York
Funding: Funding support from the National Science Foundation
X-ray beam production from a linac beam is investigated, especially emphasizing the optical matching flexibility that is possible with an external beam but not with a storage ring. Compared to existing storage ring light sources, a high energy linac (with or without recirculation) can produce monochromatic hard x-ray beams having comparable flux density, and far higher brilliance, than are available with existing storage rings. Full coherence and the possibility of diffraction limited focusing are preserved by avoiding the need for x-ray focusing mirrors.
HZB, Berlin
The UE112 APPLE undulator operated at BESSY II covers the low photon energies down to the visible regime. Below 100eV the state of polarization is significantly modified by the optical components of the beamline. Moving independently three magnet rows of the APPLE undulator (universal mode) any state of polarization can be produced which permits the compensation of the beamline effects. Thus, circularly polarized light can be provided at the experiment. The dynamic multipoles of the universal mode can be compensated with flat wires which are glued onto the vacuum chamber. Simulations and first experiments with the electron beam related to the dynamic multipoles and their compensation are presented.
KEK, Ibaraki
Two synchrotron light sources of the Photon Factory storage ring (PF-ring) and the Photon Factory advanced ring (PF-AR) have been stably operated at KEK. PF-ring covers the photon-energy range from VUV to hard X-ray using a 2.5 GeV (sometimes 3.0 GeV) electron beam. PF-AR is mostly operated in a single-bunch mode of 6.5GeV to provide pulsed hard X-rays. Recently, the operation has progressed to realize a so-called top-up injection at PF-ring. In a single-bunch mode, the continuous injection to preserve a constant beam current of 51 mA has been carried out since February 2007. In addition, the injection with continuing the experiments has been successfully operated in a multi-bunch mode since October 2008. At PF-AR, sputter ion pumps have been extensively reinforced to prolong the beam lifetime and to reduce the frequency of sudden lifetime drops by substituting for distributed ion pumps, which are considered as one of the dust sources. In this conference, we present the recent progress of the operation at PF-ring and PF-AR including machine developments.
JASRI/SPring-8, Hyogo-ken
An ultra-low emittance storage ring with an energy of 6 GeV was proposed as a next generation synchrotron radiation source*. The storage ring has the same circumference as that of SPring-8 storage ring so as to be able to replace the existing storage ring, but has not four long straight sections. Accordingly, the storage ring beam line is slightly different from that of SPring-8 and the positions of photon beam lines are also different from the existing one. To avoid this, a storage ring with four long straight sections has been designed. The beam line position of the new storage ring is the same as the existing one. The storage ring consists of twenty ten-bend achromat cells, four five-bend achromat cells and four long straight sections. The long straight section length is 34.0 m and the short one is 6.6 m. The natural emittance is less than 100 pm-rad. In the paper, the dynamic aperture problem is discussed and the other ring characteristics are presented.
*K. Tsumaki and N. Kumagai, EPAC’06, 3362.
ANL, Argonne
Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
An x-ray radiation source based on a free-electron laser (FEL) oscillator was recently proposed as a complementary facility to those based on self-amplified spontaneous emission*. Such a source uses narrow-bandwidth Bragg mirrors and a low-emittance, high-brightness electron beam to produce coherent, intense pulses of hard x-ray radiation. We present a study of the FEL oscillator performance and radiation characteristics at several potential wavelengths using a variety of electron beam and undulator parameters. Our simulations include realistic complex mirror reflectivities calculated from dynamical diffraction theory, and highlight additional constraints imposed by a four-mirror cavity that can provide tunable FEL radiation. We comment on how this concept may be extended to soft x-rays using dielectric multilayer mirrors.
*K.-J. Kim, Y. Shvyd'ko, S. Reiche, Phys. Rev. Lett. 100, 244802 (2008)
BNL, Upton, Long Island, New York
Icarus Research, Inc., Bethesda, Maryland
NRL, Washington, DC
The NSLS Source Development Laboratory (SDL) has been a world leader in the development of laser seeded free electron lasers (FEL). Recently we initiated an experimental program to investigate a Self-Amplified Spontaneous Emission (SASE) FEL in both the exponential gain and the saturation regimes. We have experimentally demonstrated the saturation of a SASE FEL in the visible to near IR. The experimental characterization of the transverse and spectral properties of the SASE FEL along the undulator for a uniformed and tapered undulator will be presented. In addition, an efficiency enhancement concept for a SASE FEL, which involves a step wiggler taper in the exponential gain regime prior to trapping, will be presented. Simulations of the SASE FEL processes will employ the GENESIS FEL code.
BNL, Upton, Long Island, New York
SAIC, McLean
Funding: This work is supported in part by the Office of Naval Research (ONR), the Joint Technology Office, and U.S. Department of Energy (DOE) under contract No. DE-AC02-98CH1-886.
We report the first experimental characterization of efficiency and spectrum enhancement in a laser-seeded free-electron laser (FEL) using a tapered undulator. Output and spectra in the fundamental and 3rd harmonic were measured versus distance for uniform and tapered undulators. With a 4% field taper over 3 m, a 300% (50%) increase in the fundamental (3rd harmonic) output was observed. A significant improvement in the spectra with the elimination of side-bands was observed for the first time using a tapered undulator. The experiment is in good agreement with predictions using the MEDUSA simulation code.
CANDLE, Yerevan
PSI, Villigen
The study of radiation saturation length and saturation power sensitivity to beam main parameters (emittance, energy spread and peak current) at the entrance of the undulator section of PSI-XFEL project is presented. The comparative analysis of the SASE FEL performance with external and natural focusing in undulator section is given.
DESY, Hamburg
Uni HH, Hamburg
The free-electron laser user facility FLASH at DESY, Germany is the world-wide leading SASE-FEL operating in the VUV and the soft X-ray wavelengths range. At present, FLASH provides fully coherent femtosecond laser radiation from 47 nm down to 6.5 nm and higher harmonics. Late 2009, FLASH will be upgraded with an additional superconducting TESLA type accelerating module boosting its beam energy to 1.2 GeV. This will allow lasing with a wavelength below 5 nm. In addition, a 3rd harmonic accelerating cavity will be installed. It allows to flatten and to a certain extend shape the longitudinal phase space improving the overall performance of the facility.
DESY, Hamburg
The European XFEL contains hundreds of sources of the coupled impedances. To have an overview of them an impedance budget database is developed. It contains wake functions of the point charge (Green functions) and allows to calculate the wake potentials for arbitrary bunch shapes.
Diamond, Oxfordshire
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Several new light source projects aim at the production of X-ray photons with high repetition rate (1kHz or above). We present here the results of the start-to-end simulations of a 2.2 GeV superconducting LINAC based on L-band SC Tesla-type RF cavities and the corresponding optimisation of the FEL dynamics at 1 keV photon energy.
Uni HH, Hamburg
DESY, Hamburg
PSI, Villigen
DELTA, Dortmund
BESSY GmbH, Berlin
Funding: This work is supported by the Bundesministerium für Bildung und Forschung under contract 05 ES7GU1
A seeded free-electron laser operating in the soft X-ray (XUV) spectral range will be added to the SASE FEL facility FLASH. For this purpose, a 40 m long section upstream of the existing SASE undulator will be rebuilt during the shutdown in fall 2009. This includes the injection of the seed beam into a new 10 m variable-gap undulator, the out-coupling of the seeded FEL radiation and all diagnostics for photon- and electron beams. The XUV seed pulse is generated by high harmonics (HHG) from a near-infrared laser, optically synchronized with FLASH. After amplification within the undulators the XUV light will be guided towards diagnostic stations. Besides a proof-of-principle demonstration for seeding at short wavelength the purpose of this development is to provide future pump-probe experiments with a more stable FEL source in terms of spectral properties and timing.
HUST, Wuhan
A primary design of a compact THz FEL oscillator is presented, which is consisted of an independently tunable cell thermionic rf gun (ITC-RF Gun), a rf linac, a planar undulator and an near concentric optical cavity composed of symmetrical spherical mirrors with an on-axis outcouple hole. Without α-magnet and other bunch compressor, the size of this machine is decreased sharply. The effect of the electron beam parameters on THz radiation is discussed. It is found that the influence of energy spread is pronounced and the influence of emittance is neglectable. Large current is required to got saturation in several us. Then the optimized beam parameters and basic design parameters are summarized.
INFN/LNF, Frascati (Roma)
The SPARX-FEL project aims at producing ultra high peak brightness electron beams in the 1.5 - 2.4 GeV range with the goal of generating FEL radiation in the 0.6-40 nm range. The construction is planned in two steps ,starting with a 1.5 GeV Linac. The project layout includes both RF-compression and magnetic chicane techniques, in order to provide the suitable electron beam to each one of three undulator systems which will generate VUV-EUV, Soft X-Rays and Hard X-rays radiation respectively This will be distributed in dedicated beamlines suitable for applications in basic science and technology: time resolved X-ray diffraction with pump and probe experiments, nanolithography processes, biological proteins, nano-particles and clusters, coherent diffraction and holographic X-ray techniques, nano-imaging. The project was funded by the Italian Department of Research, MIUR, and by the local regional government, Regione Lazio; The associated test-facility, SPARC, located at LNF, has been successfully commissioned: the SPARX-FEL project foresees the construction of a user facility inside the Tor Vergata campus by a collaboration among CNR, ENEA, INFN and the Università di Tor Vergata itself.
INFN/LNF, Frascati (Roma)
ENEA C.R. Frascati, Frascati (Roma)
ISM-CNR, Rome
The SPARX-FEL project consists in an X-ray-FEL facility which aim is the generation of electron beams characterized by ultra-high peak brightness at the energy of 1.5 and 2.4 GeV. This facility will be built in the Tor Vergata University area in Rome. The paper describe the engineering aspects of the mechanical design of the accelerator, photo-injector, LINACs, bunch compressors, beam distribution, undulators and experimental stations. Morover the integration of accelerator with the civil infrastractures is discussed.
INFN/LNF, Frascati (Roma)
ENEA C.R. Frascati, Frascati (Roma)
Rome University La Sapienza, Roma
LBNL, Berkeley, California
The modeling of the microbunching instability has been carried out for the SPARX FEL accelerator, two configurations have been considered and compared: hybrid compression scheme (velocity bunching plus magnetic compressor) and purely magnetic. The effectiveness of a laser heather in reducing this instability drawbacks on the electron beam quality has also been exploited. Analytical predictions and start to end simulation results are reported in this paper.
Kyoto IAE, Kyoto
KAERI, Daejon
UVSOR, Okazaki
The first laser amplification at a 12 micrometre mid-infrared free-electron laser (MIR-FEL) was observed at the Institute of Advanced Energy (IAE), Kyoto University in March 2008. A 25 MeV electron beam of 17 A peak current was used for the lasing experiment. FEL gain was estimated to be 16% from the exponential growth of the laser output signal. A beam loading compensation method with an RF amplitude control both in the thermionic RF gun and in the accelerator tube was used to extend the macropulse duration against the back bombardment effect in the gun. We also developed a feedforward RF phase control to stabilize the RF phase shifts which were originated with RF amplitude control. As a result FEL saturation was observed in May 2008. The estimated FEL gain was 33% with the electron beam of 5.5 microsecond macropulse duration by use of peak current of 33 A which was deduced from GENESIS simulation. A user beamline was designed and constructed. The laser characterization at the user station will be reported in the conference. Applications of the MIR-FEL at Kyoto University in the chemistry energy research will be presented as well.
ANL, Argonne
Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Circular Polarizing Undulator (CPU) had been used for about 10 years at the APS to generate X-rays with variable polarization (circular and linear) switching at rates up to 10 Hz. The CPU consists of two main coils with maximal currents 1600A (about 30kW power) and 400A (4kW power) and seven additional correcting coils. Aging and obsolescence of some of the CPU PS critical components resulted in deterioration of its performance and elevated maintenance. To resolve the issue and to comply with the new requirements for the beam stability at the APS storage ring, the new PS and control electronics for the CPU have been proposed. The new 8-channel Arbitrary Function Generator generating unique complex waveforms for the correctors to minimize orbit distortion during the main coils PS switching will also be discussed in this paper.
NSRRC, Hsinchu
Bending Magnet, linear undulator, elliptical polarized undulator and wiggler are all regular synchrotron radiation power profile that accelerator engineers would encounter while they are designing the high heat load components. Due to their characteristic type of power distribution, some temperature solutions are available and can be used as a parametric study, as well as optimized tool applicable on the thermomechanical design such as mask absorber, photon absorber, mirror or other heat load subsystems. The analytical solutions and some interrelation studies are also presented in this paper.
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
Lancaster University, Lancaster
STFC/RAL, Chilton, Didcot, Oxon
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
ANL, Argonne
Durham University, Durham
University of Bristol, Bristol
The ILC positron source relies upon a ~200 m long superconducting helical undulator in order to generate the huge flux of gamma photons required. The period is only 11.5 mm but the field strength is ~1 T. The UK is building and testing a full scale 4 m long ILC cryomodule at the moment. It will be completed in 2008 and the results used to demonstrate the feasibility of the full (200 m long) system.
RIKEN/SPring-8, Hyogo
JASRI/SPring-8, Hyogo-ken
Several labs are pursuing the concept of cooling permanent magnet undulators down to cryogenic temperatures in order to increase the remnant field of the material and so the on-axis field strength. This talk will review the progress made in this field, experimental magnet field data will be available to show the real performance of such a device and show whether they can be built and shimmed at room temperature and operated at cryotemperatures.
SLAC, Menlo Park, California
Funding: Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515
SLAC National Accelerator Laboratory is studying an option of building a high brightness synchrotron light source machine, PEP-X, in the existing PEP-II tunnel*,**. By replacing 6 arcs of FODO cells of PEPII High Energy Ring (HER) with two arcs of DBA and four arcs of TME and installation of 89.3 m long damping wiggler an ultra low beam emittance of 0.14 nm-rad (including intra-beam scattering) at 4.5 GeV is achieved. In this paper we study the possibility to further reduce the beam emittance by releasing the constraint of the dispersion free in the DBA straight. The QBA (Quadruple Bend Achromat) cell is used to replace the DBA. The ratio of outer and inner bending angle is optimized. The dispersion function in the non-dispersion straight is controlled to compromise with lower emittance and beam size at the dispersion straight. An undulator of period length 23 mm, maximum magnetic field of 1.053 T, and total periods of 150 is used to put in the 30 straights to simulate the effects of these IDs on the beam emittance and energy spread. The brightness including all the ID effects is calculated and compared to the original PEP-X design.
*R. Hettel et al., “Ideas for a Future PEP-X Light Source”, EPAC08, p.2031(2008).
**M-H Wang et al., “Lattice Design of PEP-X as a Light Source Machine at SLAC”, EPAC08, p.2127(2008).
SOLEIL, Gif-sur-Yvette
After two years of operation, the SOLEIL 3rd generation synchrotron light source is delivering photons to 20 beamlines with a current of 250mA in multibunch or hybrid modes, and 60 mA in 8 bunch mode. The radiation control of the beamline hutches is performed at 300 mA, but recently a 455mA current was stored during machine tests following the installation of the second RF cryomodule. It is foreseen to reach the maximum current of 500mA in the early 2009 and to operate in top-up mode from then on. The new transverse feedback loop has enabled to improve the performance of the single bunch and multibunch beams. The beam position stability is in the range of few micrometers thanks to the efficiency of the fast orbit feedback. Fifteen insertion devices are now installed in the storage ring, ten others are under construction, and a cryogenic undulator is under development. A big effort is being taken in order to compensate the effects of these insertion devices on the machine performance. The good operation performance achieved in 2007 (first year) has been improved in 2008 during which ~4 000 hours will have been delivered to the users with a 95.5% availability and a 30 hours MTBF.
UVSOR, Okazaki
Nagoya University, Nagoya
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. The test run of the top up injection has been started. The latest result will be reported. By utilizing a part of the existing FEL system and an ultra-short laser system, coherent synchrotron radiation and coherent harmonic generation have been extensively studied, under international collaborations. A new program on the coherent light source developments has been started, which includes upgrades of the undulator and the laser system and a construction of dedicated beam-lines.
LBNL, Berkeley, California
Funding: This work was supported under the auspices of the Office of Science, U.S. DOE under Contract No. DE-AC02-05CH11231.
Recently* it has been pointed out that numerical simulation of some systems containing charged particles with highly relativistic directed motion can by speeded up by orders of magnitude by choice of the proper Lorentz boosted frame. A particularly good example is that of short wavelength free-electron lasers (FELs) in which a high energy electron beam interacts with a static magnetic undulator. In the optimal boost frame with Lorentz factor gammaF, the red-shifted FEL radiation and blue shifted undulator have identical wavelengths and the number of required time-steps (presuming the Courant condition applies) decreases by a factor of gammaF-squared for fully electromagnetic simulation. We have adapted the WARP code** to apply this method to several FEL problems including coherent spontaneous emission (CSE) from pre-bunched e-beams, radiation in multi-wavelength undulators, and the effective lengths of undulators with entrance and exit matching ramps. We also discuss some preliminary results from applying the boosted-frame method to Coherent Synchrotron Radiation calculations.
*J.-L Vay Phys. Rev. Lett. 98, 130405 (2007)
**D.P. Grote, A. Friedman, J.-L. Vay, and I. Haber, AIP Conf. Proc., 749, 55 (2005).
MIT, Cambridge, Massachusetts
UW-Madison/SRC, Madison, Wisconsin
The seeded FEL performance of a number of Wisconsin FEL (WiFEL) undulator lines is described. The experimental design requirements include coverage of a broad wavelength range, rapid wavelength tuning, variable polarization, and variable pulse energy. The beam parameters allow experiments ranging from those requiring low peak power with high average spectral flux to those that need high peak power and short pulse lengths in the femtosecond range. The FELs must also be stable in timing, power, and energy while satisfying constraints on electron beam quality and fluctuations, undulator technologies, and seed laser capabilities. Modeling results are presented that illustrate the design performance over the full wavelength range of the facility.
NTHU, Hsinchu
NSRRC, Hsinchu
Funding: The authors gratefully acknowledge funding supports from National Synchrotron Radiation Research Center, National Tsinghua University, and National Science Council.
We study the generation of THz electron pulse trains from a 6 MeV photocathode electron gun driven by a beat-wave laser with a variable beat frequency [1]. We numerically inject the electrons into a single-pass FEL undulator. Owing to the prebunched electron pulse train, the quick shoot-up of the FEL power overcomes the space-charge debunching force in the 6 MeV beam. With nominal beam parameters and an initial bunching factor >5%, the FEL can reach 20-MW saturation power at 6 THz in a half meter long undulator. The length of this 20MW THz FEL, from the beginning of the electron gun to the end of the wiggler, is less than a meter. We will report our experimental progress of this work in the conference.
[1] Yen-Chieh Huang, “Laser-beat-wave bunched beam for compact superradiance sources,” International Journal of Modern Physics B, Vol. 21 Issue 3/4, p277-286 (2007).
PKU/IHIP, Beijing
The PKU Terahertz facility (PTF) is planned as a compact, high power Terahertz user facility based on the coherent undulator radiation concept and the superconducting radiofrequency technology for the linear accelerator. By utilizing a 3.5-cell DC-SC (DC-Superconducting) photoinjector, the PTF will provide high average power, coherent terahertz radiation with quasi-monochromaticity and wavelength tunable between 400um ~ 1200um, serving as a powerful tool for frontier researches and practical applications in the THz realm. Key components of the 3.5-cell DC-SC photoinjector have been prepared and the beamline is under construction. In this paper, the technical layout of the injector and the conceptual design of the PTF will be presented.
SLAC, Menlo Park, California
Funding: Work supported by Department of Energy contract DE-AC03-76SF00515.
The beam stability for the Linac Coherent Light Source (LCLS) at SLAC is important for good X-Ray operation. Although most of the jitter tolerances are met, there is always room for improvement. Besides the short term pulse-to-pulse jitter, we will also discuss oscillation sources of longer time cycles from seconds (feedbacks), to minutes (cooling systems), and up to the 24 hours caused by the day-night temperature variations.
SLAC, Menlo Park, California
UCLA, Los Angeles, California
The Linac Coherent Light Source (LCLS) is an x-ray Free-electron Laser (FEL) being commissioned at SLAC. Recent beam measurements have shown that, using the LCLS injector-linac-compressors, the beam emittance is very small at 20 pC*. A similar low charge operation mode was also suggested and studied**. In this paper we perform start-to-end simulations of the entire accelerator including the FEL undulator and study the FEL performance versus the bunch charge. At 20 pC charge, these calculations associated with the measured beam parameters suggest the possibility of generating a longitudinally coherent single x-ray spike with 2-femtosecond duration at a wavelength of 1.5 nm. At ~100 pC charge level, our simulations show an x-ray pulse with 20 femtosecond duration and up to 1012 photons at a wavelength of 1.5 Å. These results open exciting possibilities for ultrafast science and single shot molecular imaging.
*A. Brachmann et. al., to be published.
**J. Rosenzweig et al., Nuclear Instr. and Meth. A 593, 39-44 (2008); S. Reiche et al., Nucl. Instr. And Meth. A 593, 45-48 (2008).
SLAC, Menlo Park, California
ELETTRA, Basovizza
Funding: Work supported by the U.S. Dept. of Energy contract #DE-AC02-76SF00515.
The Linac Coherent Light Source (LCLS) is an x-ray Free-Electron Laser (FEL) project presently in a commissioning phase at SLAC. The very bright electron beam required for the FEL is also susceptible to a micro-bunching instability* in the magnetic bunch compressors, prior to the FEL undulator. The uncorrelated electron energy spread can be increased by an order of magnitude to provide strong Landau damping against the instability without degrading the free-electron laser performance. To this end, a ‘laser-heater’ system has been installed in the LCLS injector, which modulates the energy of a 135-MeV electron bunch with an IR laser beam in a short undulator, enclosed within a four-dipole chicane. The last half of the chicane time-smears the energy modulation leaving an effective thermal energy spread increase. We present the first commissioning results of this system, its operational issues, and its impact on the micro-bunching instability.
*Z. Huang et. al., Phys. Rev. ST Accel. Beams 7, 074401 (2004).
SLAC, Menlo Park, California
USTC/NSRL, Hefei, Anhui
There is a growing interest in producing intense, coherent x-ray radiation with an adjustable and arbitrary polarization state. The crossed-planar undulator* was first proposed by Kim for rapid polarization control in synchrotron radiation and free electron laser (FEL). Recently, a statistical analysis shows a degree of polarization over 80% is obtainable for a SASE FEL near saturation**. In such a scheme, nonlinear harmonic radiation is generated in each undulator and its polarization is controllable in the same manner. In this paper, we study the degree of polarization for the nonlinear harmonic radiation. We also discuss methods to reduce the FEL power fluctuations by operating the crossed undulator in the saturation regime.
*K.-J. Kim, Nucl. Instrum. Methods A 445, 329 (2000)
**Y. Ding and Z. Huang, Phys. Rev. ST Accel. Beams 11, 030702 (2008)
SLAC, Menlo Park, California
Funding: This work is supported by the Department of Energy contract DE-AC02-76SF00515.
LCLS capabilities can be significantly extended with a second undulator aiming at the soft x-ray spectrum (1- 5 nm). To allow for simultaneous hard and soft x-ray operations, 14 GeV beams at the end of the LCLS accelerator can be intermittently switched into the SLAC A-line (the beam transport line to End Station A) where the second undulator may be located. In this paper, we discuss the A-line optics design for transporting the high-brightness LCLS beams using the existing tunnel. To preserve the high brightness of the LCLS beams, special attentions are paid to effects of incoherent and coherent synchrotron radiation. Start-to-end simulations using realistic LCLS beam distributions are carried out.
SLAC, Menlo Park, California
Funding: This work was supported by US DOE contracts DE-AC03-76SF00515
The echo-enabled harmonic generation free electron laser (EEHG FEL) holds great promise in generation of coherent soft x-ray directly from a UV seed laser within one stage. The density modulation in the harmonic generation process is affected by the smearing effect caused by the fluctuations of energy and current along the beam, as well as the field error of the dispersive elements. In this paper we study the tolerance of the EEHG FEL on beam quality and field quality.
SLAC, Menlo Park, California
ASCo, Clayton, Victoria
Funding: Work supported by Department of Energy contract DE-AC02-76SF00515. This work was performed in support of the LCLS project at SLAC
The Linac Coherent Light Source is an x-ray Free-Electron Laser (FEL) project being commissioned at SLAC. The very bright electron beam required for the FEL is subjected to various sources of jitter along the accelerator. The peak current, centroid energy, and trajectory of the electron bunch are controlled precisely at the highest repetition rate possible with feedback systems. We report commissioning experience for these systems. In particular, there is high frequency content in the electron bunch current spectrum, and we report its impact on the systems. Due to the coupling of the betatron motion and the dispersion component of the electron trajectory, a fast in-line model* is incorporated. For the longitudinal feedback, we report the performance of two different configurations: one with RF system as direct actuators, which are nonlinear, and the other with artificially formed linear energy and energy-chirp actuators. Since the electron bunch is compressed to a final peak current of 2 to 3 kA, coherent synchrotron radiation and other wakefields are included for precise control of the electron bunch parameters. Machine performance is compared to start-to-end simulations.
*P. Chu et al., these PAC09 proceedings
ELETTRA, Basovizza
University of Nova Gorica, Nova Gorica
In single-pass FELs, for the amplification process to be effective, it is necessary to compensate the phase advance of photons with respect to electrons in the break region between undulators. In fact, most of the FELs are based on the use of phase shifters between different undulator sections in order to allow the control of the relative phase advance. In this work we present different methods in which the use of phase shifters can be useful for a further improvement of the FEL performance.
RIKEN/SPring-8, Hyogo
The compact XFEL facility under construction in the SPring-8 campus aims at generation of SASE based XFEL at the wavelength of ~0.1 nm in 2010. Toward the smooth completion of the beam commissioning and achieving the reliable SASE XFEL operation, it is critically important to suppress the dark current upstream of the accelerator as much as possible. We thus investigated a removal scheme of the spatially diverged and energy deviated electrons forming the dark current by using sextupole magnets, which are installed over the C-band accelerating structures. The beam simulation showed that the combination of the distributed sextupole magnets with a small chicane, which locates in the adequate middle of the C-band accelerating structures, could efficiently remove the dark current emitted from the C-band acceleration structures. Here, we present the simulation results and the dark current suppression scheme designed for the compact XFEL facility at SPring-8.
Universita' degli Studi di Milano, Milano
Istituto Nazionale di Fisica Nucleare, Milano
INFN/LNF, Frascati (Roma)
ENEA C.R. Frascati, Frascati (Roma)
INFN-Roma, Roma
In this paper a possible experiment with the existing SPARC photoinjector is described to generate sub-picosecond high brightness electron bunches able to produce single spike radiation pulses at 500 nm with the SPARC self-amplified spontaneous emission free-electron laser (SASE-FEL). The main purpose of the experiment will be the production of short electron bunches as long as few SASE cooperation lengths, the determination of the shape of the radiation pulse and the validation of the single spike scaling law, in order to foresee operation at shorter wavelength in the future operation with SPARX. We present in this paper start to end simulations regarding the beam production and FEL performance, and discuss the layout of the machine. The experience, gained from this experiment, will help in the configuration of the VUV and X-ray FEL SPARX to obtain FEL pulses below 10 fs.
UCLA, Los Angeles, California
University of Tel-Aviv, Faculty of Engineering, Tel-Aviv
PSI, Villigen
The resonant harmonic interaction of an electron beam (e-beam) with an EM input field in a helical undulator is explored. The e-beam is coupled to the input radiation field at frequency harmonics through transverse gradients in the EM field, and helical micro-bunching of the e-beam is shown to occur naturally at the higher harmonics with the injection of a simple gaussian laser mode onto a cylindrically symmetric e-beam. This approach is under investigation as a method to generate a strongly pre-bunched e-beam seed for superradiant emission of light that carries orbital angular momentum in a downstream free-electron laser.
ANL, Argonne
Slovak Academy of Sciences, Institute of Electrical Engineering, Bratislava
Funding: * Work at Argonne supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract no. DE-AC02-06CH11357.
Hall probe is the best way to do tuning and measurements of insertion devices. Horizontal Hall probe magnetic field measurements in the presence of a strong vertical magnetic field were tested in 1997. The next step of this investigation was reported at the 2004 FEL Conference. Hall probe horizontal field measurements in the presence of a vertical magnetic field are complicated due to the influence of the Planar Hall probe effect on the resulting Hall voltage. 2-axis Sentron Hall probe was used for the Linear Coherent Light Source devices. By positioning the Hall probe accurately in the vertical direction, the probe could be used for fast measurements and tuning of FEL devices. To eliminate the high sensitivity to the positioning of the probe, a new type of Hall probe, consisting of two sensors combined so as to cancel the influence of the PHE, was developed at the Institute of Electrical Engineering, Slovak Academy of Sciences. The results of tests done at the APS showed that it is not sensitive to vertical position and is 60 times less sensitive than a Bell probe to the angle between the Hall sensor current and the in-plane component of the field direction.
ANL, Argonne
Funding: Work at Argonne was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No DE-AC02-06CH11357.
The Linac Coherent Light Source (LCLS), now being commissioned at the Stanford Linear Accelerator Center (SLAC) in California, and coming online for users in the very near future, will be the world’s first x-ray free-electron laser user facility. Design and production of the undulator system was the responsibility of a team from the Advanced Photon Source (APS) at Argonne National Laboratory (ANL). A sophisticated, five-axis, computer-controlled support and motion system positions and stabilizes all beamline components in the undulator system. The system also enables undulators to be retracted from the beam by 80 mm without disturbing the rest of the beamline components. An overview of the support and motion system performance, including achieved results with a production unit that was reserved at Argonne for this purpose, is presented.
BNG, Würzburg
KIT, Karlsruhe
FZK, Karlsruhe
University Erlangen-Nuernberg, Erlangen
Superconducting insertion devices (IDs) are very attractive for synchrotron light sources since they allow increasing the flux and/or the photon energy with respect to permanent magnet IDs. Babcock Noell GmbH (BNG) is completing the fabrication of a 1.5 m long unit for ANKA at FZK. The period length of the device is 15 mm for a total of 100.5 full periods plus an additional matching period at each end. The key specifications of the system are: a K value higher than 2 and the capability of withstanding a 4 W beam heat load and a phase error of 3.5 degrees. In addition, during the injection phase of the machine, the nominal gap of 5 mm can be increased up to 25 mm. The magnets have been tested with liquid helium in a vertical dewar and are now being installed in the cryostat. This paper describes the technical design concepts of the device and the status of the assembly process.
BNG, Würzburg
DESY, Hamburg
Babcock Noell GmbH manufactured for DESY 11 identical planar permanent magnet-undulators (8 for the PETRA III upgrade and 3 for FLASH). The positioning accuracy and the movement reproducibility of the two girders, defining the magnetic gap of an undulator, are of vital importance for the quality of the synchrotron light. To reach the desired performance a high quality standard was kept during the choice and procurement of the components, during the high precision machining of the parts and during the assembly phase. After the alignment, laser tracker-measurements were made and evaluated for all the 11 systems. Both, the means by which the accuracy and reproducibility were achieved, and the results of the measurements will be presented here.
ESRF, Grenoble
SOLEIL, Gif-sur-Yvette
A cryogenically cooled in-vacuum undulator was installed in the ID6 test beamline of the ESRF in January 2008. This 2 metre long hybrid undulator has a period of 18 mm. The magnetic assembly is based on NdFeB permanent magnets cooled at a temperature close to 150 K . A liquid nitrogen closed loop is used for the cooling of the undulator. This cooling system is well adapted for achieving a uniform temperature along the magnetic assembly. An important part of the study was focused on the heat budget of the undulator under beam in the different filling modes delivered at the ESRF. The impact of the undulator on the ultra high vacuum of the ring was investigated with several warming/cooling cycles. This paper presents the main outcomes from this first experience.
FZK, Karlsruhe
KIT, Karlsruhe
ESRF, Grenoble
ELETTRA, Basovizza
University Erlangen-Nurnberg, Institute of Condensed Matter Physics, Erlangen
MAX-lab, Lund
Within the framework of a joint research activity of the European project IA-SFS (RII3-CT2004-506008) four synchrotron facilities have jointly developed diagnostic systems for superconducting undulators. Four work packages have been successfully completed: Design and construction of a test cryostat for field measurements; design and construction of a mock-up coil; field measurement and field error compensation; diagnostics and measurement of the spectrum of low energy electrons responsible for beam heat load in a superconducting undulator. The development advanced the knowledge of magnetic field error compensation considerably and might be of help in understanding the different beam heat load sources. Based on the development a second generation planar superconducting undulator with 15 mm period length for the synchrotron light source ANKA has been specified and procured.
FZK, Karlsruhe
Preliminary studies performed with the cold bore superconducting undulator installed in the ANKA storage ring suggest that the beam heat load is mainly due to the electron wall bombardment. Electron bombardment can both heat the cold vacuum chamber and induce an increase in the pressure because of gas desorption. In this contribution we compare the measurements of the pressure in a cold bore performed in the electron storage ring ANKA with the prediction obtained using the equations of gas dynamic balance in a cold vacuum chamber exposed to synchrotron radiation and electron bombardment. The balance results from two competitive effects: the photon and electron desorption of the gas contained in the oxide layer of the chamber wall and of the gas cryosorbed, and the cryopumping of the cold surface. We show that photodesorption alone cannot explain the pressure rise observed and that electron multipacting is needed.
Uni HH, Hamburg
DESY, Hamburg
A seeded free-electron laser experiment at VUV wavelengths, called sFLASH, is being prepared at the existing SASE FEL user facility FLASH. Seed pulses at wavelengths around 30 nm from high harmonic generation will interact with the electron beam in sFLASH undulators upstream of the existing SASE undulator section. In this paper, sFLASH undulators are described.
HSRC, Higashi-Hiroshima
After the first demonstration of original quasi-periodic undulator (QPU) at the NIJI-IV*, there have been many modifications for QPU structures. One of the first most productive improvements was introducing the quasi-periodicity by modifying the magnetic field in a periodic undulator instead of modifying the period length**. In addition to this practical improvement, a slight modification of creation theory of one-dimensional quasi-periodicity gave another advantage for building this type of device. As the result, many different types of QPUs for generating both linearly and elliptically polarized radiations have been installed in the synchrotron radiation (SR) facilities worldwide. Furthermore, some more SR facilities are considering to building such devices in order to improve their performance. In the presentation, we will discuss about limitations and possible improvements of performance of QPU on the basis of synchrotron radiation physics and mathematics of quasi-periodicity.
*Kawai, et al, Proc. EPAC96, p.2549.
**Diviacco, Walker, ELETTRA Technical Note ST/M-TN-97/11, 1997, Chavanne, et al, Proc. EPAC98, p.2213, Diviacco, et al, ibid., p.2216.
Hiroshima University, Graduate School of Science, Higashi-Hiroshima
KEK, Ibaraki
A fast local bump system for the helicity switching of a circular/linear polarized undulator (CPU) has been developed at the Photon Factory storage ring (PF-ring). The system consists of five identical bump magnets and tandem APPLE-2 type CPUs. In addition, fast correction magnets for a leakage of the bump were prepared. We designed the bump magnets with a core length of 0.15 m, a pole gap of 21 mm and the coils of 32 turns, which were excited by bipolar power supplies with a capacity of ±100 A and ±50 V since a switching frequency of more than 10 Hz and a bump angle of 0.3 mrad were required for user experiments. The bump magnets and one of CPUs were installed at PF-ring in March 2008, and the experiments for the machine development using a stored beam have been progressed. In this conference, we present the first experimental results with the bump system.
HUST, Wuhan
The design of compact terahertz (THz) radiation source based on free electron laser (FEL) has been implemented, whose concept machine is consisting of a thermionic RF gun (ITC-RF Gun), a LINAC, a hybrid undulator combined with an optical resonance cavity of hole-coupling mode. The aim of the project is to provide a stable coherent THz (1~3THz) source. The hybrid undulator system is the critical component for compact terahertz FEL. Emission wavelength is related to the period and the peak magnetic field of the hybrid undulator. In particular, the magnetic structure by adding side magnet blocks to each pole will increase the field strength, avoid too small gap, and make the system more compact. Simulations using RADIA are presented. The feature of designs, optimization of the magnetic parameters and field analysis will be discussed.
Kyoto IAE, Kyoto
UVSOR, Okazaki
A short period undulator with strong magnetic field will play an important role in future light source. We proposed a new type of staggered array undulator by use of bulk high-Tc superconductor*. We have constructed a prototype of the undulator using DyBaCuO bulk superconductors and a normal conducting solenoid. In the conference, we will present results of the magnetic field measurement and discuss on the feasibility of the new type bulk high-Tc staggered array undulator.
*R. Kinjo et al., Proceedings of the FEL2008, in press.
LBNL, Berkeley, California
Funding: This work was supported by the Director, Office of Science, U.S. Department of Energy, under contract No. DE-AC02-05CH11231.
Superconducting undulators are currently under development at a number of light sources to serve as the next generation of insertion devices, with higher fields providing enhanced spectral range for users. Most of these devices are designed with wire-based technologies appropriate for periods greater than ~10mm. New undulator concepts yielding very short-period, high-field devices with periods of a few millimeters and a K~1 have the potential to significantly reduce the cost and enhance the performance of FEL's. Here we describe a design using high temperature superconductor tapes that are commercially available, and that promise a cost-effective fabrication process using micromachining or lithography. Detailed magnetic and spectral performance analysis will be provided.
UCLA, Los Angeles
A helical undulator, utilizing permanent-magnet of cylindrically symmetric (Halbach) geometry has been developed at UCLA’s Neptune Facility. The initial prototype is a short 10 cm, 7 periods long helical undulator, designed to test the electron-photon coupling by observing the micro-bunching has been constructed and is currently being tested in the Neptune facility. An Open Iris-Loaded Waveguide Structure (OILS) scheme which conserves laser mode size and wave fronts throughout the undulator, is utilized to avoid Gouy phase shift caused by focusing of the drive laser. Coherent Transition Radiation and Coherent Cherenkov Radiation is used for micro-bunching diagnostic. Currently the undulator has been built, magnets were calibrated via pulsed wire method.
RadiaBeam, Marina del Rey
BNL, Upton, Long Island, New York
Funding: DOE
A High Temperature Superconducting Dysprosium Pole Undulator (HTS-DPU) is proposed to achieve an ultra-high peak field in a very short period undulator structure. This design utilizes the unique ferromagnetic properties of dysprosium (Dy) at liquid nitrogen temperature. The fabrication of textured Dy fabricated via economic and highly reproducible process is studied experimentally with the goal to achieve sufficient magnetic anisotropy and desired field saturation level at a practical cost. In addition, utilizing the latest capabilities of the 2G HTS wire is investigated. The practical implementation of HTS-DPU would enable the development of short period insertion devices with superior performance.
ELETTRA, Basovizza
CELLS-ALBA Synchrotron, Cerdanyola del Vallès
Two variable polarization undulators have been designed and constructed as a Collaboration between CELLS and Sincrotrone Trieste*. In this paper the main magnetic and mechanical feature are summarized. Field optimization techniques are described, showing the achieved performance in terms of phase, trajectory and field integral errors.
*D.Zangrando et al. Design of two variable polarization undulators for the ALBA project, EPAC 2008, Genova, Italy
SLRI, Nakhon Ratchasima
NSRRC, Hsinchu
Highest photon beam brightnesses are achieved in radiation from undulators. Very short period length and high fields, reached only in superconducting undulators, are desired to produce hard X-rays. In lower energy storage rings this is not enough, but radiation at higher harmonics(7th and up) are desirable. This is possible only if the undulator fields and periods are near perfect. Shimming methods as applied for room temperature permanent magnet undulators cannot be used for such superconducting magnets. The effect of field and period tolerances on higher harmonics photon beam brightnesses will be presented and limiting tolerances will be discussed. A variety of different field optimization techniques together with some measurements on test magnets will be discussed and evaluated to their usefulness as a high photon energy and high brightness radiation source.
SOLEIL, Gif-sur-Yvette
BNL, Upton, Long Island, New York
SOLEIL storage ring presents a very high fraction of the total circumference dedicated to accommodate insertion devices. Over the presently planned 25 insertion devices presenting a large variety of systems, 15 have been already installed and commissioned by the end of 2008. The UV-VUV region is covered with electromagnetic devices (one HU640 and 3 HU256), offering tuneable polarisations. An electromagnet/permanent magnet undulator using copper sheets as coils for fast switching of the helicity is under construction. 13 APPLE-II types undulators, with period ranging from 80 down to 36 mm, provide photons in the 0.1-10 keV region, some of them featuring tapering or quasi-periodicity. 5 U20 in-vacuum undulators cover the 3-30 keV range whereas an in-vacuum wiggler, with magnetic forces compensation via adequate springs is designed to cover the 10-50 keV spectral domain. R&D on cryogenic in-vacuum undulator has also been launched. A magnetic chicane using permanent magnet dipoles has also been designed in order to accommodate two canted undulators on the same straight section. The processes for optimizing the insertion devices and their achieved performances will be described.
SOLEIL, Gif-sur-Yvette
A new electromagnetic/permanent magnets helical undulator, with a 65 mm magnetic period is under development at SOLEIL for providing a rapid switching of the photon polarization required to perform dichroïsm experiments. The vertical field will be produced by coils fed by a fast switching power supply, with a maximum current of 350 A and a polarity switching time shorter than 100ms. The coils consist of copper sheets cut by water jet method. 26 layers of copper will be stacked together while 10 of them will be water cooled. The current-regulated power supply should be able to operate in the 4 quadrants with a 50 ppm current resolution over the full scale. The design of this home made power supply will be described. The horizontal field will be generated by NdFeB permanent magnets. The design vertical and horizontal peak field values in the helical configuration are 0.24 T at the minimum 15.5 mm gap. The magnetic design and the correction scheme will be described. A prototype was built to characterise and validate the technical choices, and the results will be discussed. The efficiency of the cooling system and the results of the magnetic measurements will be presented.
UCLA, Los Angeles, California
BESSY GmbH, Berlin
LMU, München
The fundamentals of insertion device physics demand that to have access to ever higher photon energies either the beam energy must increase or the undulator period must decrease. Recent advances in accelerator technology have increased beam energies and at the same time insertion device technology has developed creative ways of producing light of the desired energy, characteristics and quality. This paper describes the simulation work for the design of a 9 mm period in-vacuum planar undulator using a new rare-earth magnetic material.
KIT, Karlsruhe
University of Erlangen-Nürnberg, Physikalisches Institut II, Erlangen
FZK, Karlsruhe
The ANKA superconductive undulator (SCU14) is continously operated since 2005. The main objetive of this operation was to investigate the interactions between the undulator and the stored electron beam and to characterise the undulator radiation. The characterisation of the undulator radiation was done with a short test beamline designed for spacially and spectrally resolved measurements of the undulator radiation intensity. This contribution summarises the results of these measurements. The spectra are cross-correlated with the magnetic field measurements carried out earlier.
KIT, Karlsruhe
FZK, Karlsruhe
IMFD, Freiberg
The next step towards introducing superconductive undulators as the new generation of insertion devices is to understand the impact of dynamic effects in the superconducting coils on the accelerator beam. These effects are seen as a temporal drift of the beam orbit, originating from transients of the magnetic field. The first systematic time resolved measurements of such drifts have been performed ANKA. Orbit displacement during several different ramping cycles, for different ramp rates and relaxation times, has been investigated. This contribution summarises the results of the measurements. The persistent current effects in the superconducting wires, as well as eddy currents in the yoke are discussed as possible sources for the transients.
KIT, Karlsruhe
CERN, Geneva
FZ Karlsruhe, Karlsruhe
NbTi wires are relatively easy to handle and are therefore up to now the preferred material for superconductive insertion devices. Yet other materials, like Nb3Sn, MgB2 or high temperature superconductors, are less sensitive to beam heat load and/or are able to produce higher magnetic fields. In this paper the different superconducting materials and their advantages and challenges are discussed. Additionally this paper describes new designs for special insertion devices like damping wigglers and undulators for laser wakefield accelerators.
KIT, Karlsruhe
FZK, Karlsruhe
University Erlangen-Nuernberg, Erlangen
Recently a new concept for automatically reducing magnetic field errors in superconductive undulators was proposed. According to this proposal the field errors are compensated by an array of coupled high temperature superconductor loops attached to the surface of the superconductive undulator. The field errors induce currents in the coupled type II-superconducting loops and, as a result, the magnetic field generated by these currents minimizes the field errors. In this paper the results of a first successful experimental test of this concept are described.
USTC/NSRL, Hefei, Anhui
For planar undulator, the expression of electron trajectory including harmonic motion has been deduced. It were shown that the electrons oscillate at odd harmonics in the transverse direction, and at even harmonics in the axial direction; the amplitude of nth harmonic oscillation is proportional to the nth power of ratio of undulator deflection parameter to the electron energy.
ANL, Argonne
SLAC, Menlo Park, California
Funding: This work was supported by the US Department of Energy Office of Science under Contract No. DE-AC02-06CH11357.
The effect of ILC positron source’s helical undulator to the drive electron beam is of great interest. People have been looking into the effect of wakefield, quad misalignment and also the effect of radiation. In this paper we’ll report an emittance damping effect of the ILC positron source undulator to the drive electron beam and our QUAD-BPM error simulation results. For 100m RDR undulator, the emittance of drive electron beam will be damped down by about 1% instead of growing as the damping is stronger than quantum excitation for this RDR undulator with the RDR drive electron beam. Quad-BPM misalignment simulations show that a 20um rms misalignment error in a 250m long undulator beamline can cause about 5% emittance growth in drive electron beam. Taking into consider the damping effect of undulator, the net emittance growth will be smaller.
CLASSE, Ithaca, New York
We are analyzing ILC positron source for best polarization and efficiency. 70% polarization looks feasible for 170 m undulator at 150 GeV. Conversion efficiency and polarization at 500 GeV considered also. We are making suggestions for reaching 80% positron polarization AT ILC as well.
CLASSE, Ithaca, New York
N.U, Nigde
We consider a scheme for gamma-gamma collisions at ILC. In our scheme the electron beam from 5 GeV injector-Linacs, present in ILC scheme, used in FEL amplifier. The laser radiation from solid-state laser amplified in this FEL and directed to nearby IP point for further Compton back scattering. Two additional ~50 m helical undulators and master laser system of intermediate power required for this scheme at ILC.
ELETTRA, Basovizza
Funding: The work was supported in part by the Italian Ministry of University and Research under grant FIRB-RBAP045JF2.
To avoid damages on permanent magnets by the electrons, collimators will be installed in FERMI@elettra. Their dimensions and shape are defined through the beam optics and the induced wake fields while GEANT simulations are performed to determine their absorption efficiency and thermal load for both normal operating conditions and in case of miss-steering. The design, the simulations and the expected performance of the collimators are presented and discussed.
LBNL, Berkeley, California
Funding: US Department of Energy contract No. DE-AC02-05CH11231, and NSF Grant 0614001
We discuss the design and current status of experiments to couple the THUNDER undulator to the Lawrence Berkeley National Laboratory (LBNL) laser wakefield accelerator (LWFA). Currently the LWFA has achieved quasi-monoenergetic electron beams with energies up to 1 GeV*. These ultra-short, high-peak-current, electron beams are ideal for driving a compact XUV free electron laser (FEL)**. Understanding the electron beam properties such as the energy spread and emittance is critical for achieving high quality light sources with high brightness. By using an insertion device such as an undulator and observing changes in the spontaneous emission spectrum, the electron beam energy spread and emittance can be measured with high precision. The initial experiments will use spontaneous emission from 1.5 m of undulator. Later experiments will use up to 5 m of undulator with a goal of a high gain, XUV FEL.
*W.P. Leemans et al., Nature Physics, Volume 2, Issue 10, pp. 696-699 (2006).
**C.B. Schroeder et al., Proceedings AAC08 Conference (2008).
SLAC, Menlo Park, California
Funding: Work supported by the U.S. Dept. of Energy contract #DE-AC02-76SF00515.
The Linac Coherent Light Source (LCLS) is a SASE 1.5-15 Å x-ray Free-Electron Laser (FEL) facility under construction at SLAC, and presently in an advanced phase of commissioning. The injector, linac, and new bunch compressors were commissioned in 2007 and 2008, establishing the necessary electron beam brightness at 14 GeV. The final phase of commissioning, including the FEL undulator and the long transport line from the linac, began in November 2008, with first 1.5-Å FEL light and saturation observed in mid-April 2009. We report on the accelerator, undulator, and FEL operations, although prior to the availability of the full x-ray diagnostics suite, which will not be ready until June 2009.
RIKEN/SPring-8, Hyogo
JASRI/SPring-8, Hyogo-ken
The SPring-8 compact SASE source (SCSS) test accelerator was constructed in FY2005 to demonstrate a new concept for X-ray free electron lasers composed of a low-emittance thermionic electron injector, a high-gradient normal conducting C-band accelerator, and a short-period in-vacuum undulator. With a 250 MeV electron beam, continuous SASE saturation can generate intense and stable FEL beams at the wavelength range from 50 to 60 nm with the maximum pulse energy of 30 micro-J and the intensity fluctuation of ~10%. Analysis of the SASE saturation data with a 3D-FEL simulation code suggests negligible degradation of the electron beam emittance during the high bunch compression process. We also succeeded in operating the C-band accelerator with a high accelerating gradient of 37 MV/m and a repetition rate of 60 pps. Now, the FEL beam is routinely delivered for user experiments. At this conference we will present the machine performance and recent progress of the SCSS test accelerator together with the anticipated performance of the 8 GeV XFEL under construction.
DESY, Hamburg
The free-electron laser facility FLASH at DESY, Germany is the world-wide unique SASE-FEL operating in the VUV and the soft X-ray wavelengths range. Since Summer 2005, FLASH operates as a user facility providing fully coherent 10 to 50 femtosecond long laser radiation in the wavelength range from 47 nm to 6.5 nm and with an unprecedented brilliance - many orders of magnitude higher than any other facility. The SASE radiation contains also higher harmonics. Several experiments have successfully used the third and fifth harmonics, in the latter case with a wavelength down to 1.59 nm. In addition, FLASH serves as a pilot facility for the European XFEL. Part of the beam time is reserved for general accelerator studies which also includes ILC related studies.
UCLA, Los Angeles, California
Funding: This work was supported by DOE grants DE-FG03-92ER40727 and DE-FG03-92ER40693
Many proposals and ongoing national projects exist worldwide to build a single-pass X-ray FEL amplifier in which a high-brightness, multi-GeV electron beam has a resonant energy exchange with radiation in an undulator. Because of the practical limit on the undulator period, the electron beam energy represents one of constraints on the shortest reachable wavelength. Recently the high-order harmonic FEL/IFEL interactions were considered theoretically as a technique that would allow the reduction of the beam energy without corresponding decrease in the undulator period and the magnetic field strength. We demonstrate microbunching of the 12.3 MeV electrons in a 7th order IFEL interaction, where the seed radiation frequency is seven times higher then the fundamental frequency. Strong longitudinal modulation of the beam is inferred from the observation of the first, second and third harmonics of the seed radiation in a Coherent Transition Radiation spectrum. The level of seed power is comparable to that required for microbunching at the fundamental frequency of the ten-period-long undulator. The implications of these results for the next generation of FELs will be explored.
Diamond, Oxfordshire
Diamond Light Source, the UK's 3rd generation synchrotron light facility, became operational in 2007. We report here on a number of important recent developments, aimed at increasing its operational performance. In particular, we present our initial experience with regular top-up injection, which began at the end of October 2008, including its reliability and effect on beam stability. We also discuss the issues that have been faced in increasing the beam current to its design value of 300 mA. Diamond currently operates with 10 in-vacuum undulators with a specified initial minimum operating gap of 7 mm. We report on our efforts to understand and control the distribution of beam losses in the ring, in order to allow operation with gaps as small as the target value of 5 mm.
On behalf of the Diamond Machine Staff
INFN/LNF, Frascati (Roma)
Istituto Nazionale di Fisica Nucleare, Milano
CEA, Gif-sur-Yvette
INFN-Roma II, Roma
ENEA C.R. Frascati, Frascati (Roma)
SOLEIL, Gif-sur-Yvette
INFN-Roma, Roma
University of Tehran, Tehran
UCLA, Los Angeles, California
The SPARC project foresees the realization of a high brightness photo-injector to produce a 150-200 MeV electron beam to drive 500 nm FEL experiments in SASE, Seeding and Single Spike configurations. The SPARC photoinjector is also the test facility for the recently approved VUV FEL project named SPARX. The second stage of the commissioning, that is currently underway, foresees a detailed analysis of the beam matching with the linac in order to confirm the theoretically prediction of emittance compensation based on the “invariant envelope” matching , the demonstration of the “velocity bunching” technique in the linac and the characterisation of the spontaneous and stimulated radiation in the SPARC undulators. In this paper we report the experimental results obtained so far. The possible future energy upgrade of the SPARC facility to produce UV radiation and its possible applications will also be discussed.
CELLS-ALBA Synchrotron, Cerdanyola del Vallès
FZK, Karlsruhe
CERN, Geneva
One of the key issues for the developments of superconducting insertion devices is the understanding of the beam heat load in the vacuum chamber. The beam heat load observed in the superconducting cold bore undulator installed in the ANKA storage ring is higher than the one predicted by the synchrotron radiation and resistive wall heating. A non linear increase of the dynamic pressure with the beam current is also observed in the cold bore. In order to investigate whether the nature of these effects is due to an electron cloud formation, we have performed several simulations using the ECLOUD code.
ANL, Argonne
SLAC, Menlo Park, California
Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract number DE-AC02-06CH11357.
Simulations of the beam loss monitor (BLM) system built at the Advanced Photon Source (APS) for the Linear Coherent Light Source (LCLS) have been carried out using the Monte Carlo particle tracking code MARS. Cerenkov radiation generated by fast electrons in the quartz radiator of the BLM produces the signal used to estimate beam loss and dose in the LCLS undulator magnets. The calibration of the BLM signal with radiation components that cause undulator damage is the goal of the simulation effort. Beam loss has been simulated for several scenarios including undulator magnets in the normal operating position, “rolled-out” 80 mm from the beamline, and absent altogether. Beam loss is generated when an electron bunch strikes one of two targets: Al foil or carbon wire. In the former case, the foil is placed at OTR33, 85.8 m upstream of the FEL; in the latter, the first undulator beam finder wire (BFW01) position is used just upstream of the first magnet. The LCLS MARS model includes quadrupole focusing between OTR33 and the end of the FEL. The FODO lattice leads to complex loss patterns in the undulators consistent with betatron envelope maximums in both transverse planes.
FZK, Karlsruhe
CERN, Geneva
KIT, Karlsruhe
Max-Planck Institute for Metal Research, Stuttgart
Funding: This work has partly been supported by the Initiative and Networking Fund of the Helmholtz Association under contract number VH-NG-320.
A superconducting undulator is installed in the ANKA electron storage ring. Electron clouds could potentially contribute to the heat load of this device. A microwave transmission type electron cloud diagnostic has been installed for the undulator section of the ANKA machine. We present the system layout with particular emphasis on the electron machine aspects. Hardware transfer function results and e-cloud data for different machine settings are discussed. Special care has been taken for front end filter design both on the microwave injection and pick-up side.
MSL, Stockholm
DESY, Hamburg
The undulators of the European free-electron laser (XFEL) are 128 to 226 meters in length and divided into five meter long segments. Each segment ends with a quadrupole magnet to focus the electron beam and to maintain optimum spatial overlap between the electron and photon beams. At the Manne Siegbahn Laboratory a rotating coil instrument has been built to characterize these quadrupoles and to measure the position of the magnetic center. In combination with a coordinate measurement machine the magnetic center can be measured with respect to fiducials on the magnet. The aim is to measure the position of the magnetic center within 0.050 mm. In this work the experimental setup is presented together with fiducialization of test magnets.
DESY, Hamburg
The aim of the FLASH facility linac is to create electron bunches of small transverse emittance and high current for the FLASH free-electron laser at DESY. Available operational experience indicates that in order to optimize SASE signal at different wavelengths or to fine-tune the FEL wavelength, empirical adjustment of the machine parameters is required and, therefore, the sensitivity of the beamline to small changes in the beam energy and in the magnet settings becomes one of the important issues which affects the final performance. In this article the transverse optics of the FLASH beamline with low sensitivity to changes in beam energy and quadrupole settings is presented. This optics is in operation since spring 2006 and has shown a superior performance with respect to the previous setup of the transverse focusing.
Diamond, Oxfordshire
JAI, Oxford
A proposal has been developed to modify a long insertion straight (~11.4 m long) of the DIAMOND storage ring. Additional quadrupoles provide two sections with small vertical beta-function values, in order to accommodate two canted in-vacuum undulators for the imaging and coherence branches of the I13 beam line. A further requirement was to provide a horizontal focussing of the emitted undulator radiation by means of a positive alpha-x in the second section. This optic is obtained using a small relaxation in the “pitrick”, approximately preserving the on-momentum nonlinear dynamics of the ring. The effects of the optic on beam dynamics (i.e. beam lifetime, injection etc.) and possible compensation schemes are presented.
CERN, Geneva
SOLEIL, Gif-sur-Yvette
The successful correction of non-linear resonances in DIAMOND using the BPM turn-by-turn data has motivated testing this approach in SOLEIL in collaboration with CERN. We report on the first experiences towards the correction of non-linear resonances in SOLEIL.
SLAC, Menlo Park, California
Funding: Work supported by U.S. Department of Energy under Contract Nos. DE-AC02-06CH11357 and DE-AC02-76SF00515.
The Linac Coherent Light Source (LCLS) project at SLAC uses a dense 15 GeV electron beam passing through a 131m undulator to generate extremely bright xrays. The project requires electron bunches with a bunch charge of 20pC to 1nC and bunch lengths of 0.020mm (70fs).To measure the beam resolution to 1 micron (rms) for bunch charge > 20 pC in the undulator, a cavity BPM system was chosen. This system can measure the beam position to within a micron. The LCLS Cavity BPM local oscillator subsystem consists of a second order phase-locked loop (PLL) to synchronize with LCLS timing system and injector system. The output of the PLL is distributed to 36 Cavity BPM receivers and 36 high speed digitizers while maintaining good phase noise and low jitter. This paper describes the design of the PLL and how it met the design specifications of 0.1 degree of phase noise at 119MHz and 1 ns of rms jitter.
The University of Liverpool, Liverpool
Cockcroft Institute, Warrington, Cheshire
An analytic tracking code has been developed to describe an arbitrary magnetic field in terms of its generalised gradients* and multipole expansion, which is used with a 2nd-order symplectic integrator** to calculate dynamical maps for particle tracking. The modular nature of the code permits a high degree of flexibility and allows customised modules to be integrated within the code framework. Several different applications are presented, and the speed, accuracy and flexibility of the algorithms are demonstrated. A module to simulate synchrotron emission is described and its application to an 'ILC-type' undulator system is demonstrated.
*Venturini M. and Dragt A., NIM Phys. Res. Sect. A, 427, 387 (1999)
**Wu Y., Forest E., Robin D.S., Physical Review E,68, 4, Part 2, 046502 (2003)
BNL, Upton, Long Island, New York
For the NSLS-II storage ring with damping wigglers but without a Landau cavity, the low-current bunch length is 4.5mm. We have studied bunch lengthening and estimated the microwave instability threshold using the multi-particle tracking code TRANFT. An estimate of the pseudo-Green’s function for a 0.5mm driving bunch was obtained for most components of the vacuum system by using the 3D code GdfidL. With our present computer resources, certain components were too large and had too complex geometry to allow the wake for such a short bunch to be computed using GdFidL. In these cases, the actual 3D geometry was approximated by a structure having circular cross-section, and the pseudo-Green’s function was computed using the 2D code ABCI. It was found that the dominant geometric wake is due to the tapers for the in-vacuum undulators. The resistive wall wake is also important. The effect of pseudo-Green’s functions corresponding to an even shorter driving bunch (0.05mm) was investigated using the program ECHO to compute the wake of tapers with circular cross-section. Our results suggest that the microwave threshold will occur at an average single-bunch current greater than 5mA.
CANDLE, Yerevan
PSI, Villigen
The longitudinal and transverse impedances of CPMU (cryogenic permanent magnet undulators) of the SLS storage ring are evaluated. The study takes into account the walls frequency dependent conductivity and the electrical and magnetic properties of the material at low temperature.
CANDLE, Yerevan
PSI, Villigen
YSU, Yerevan
The resistive longitudinal and transverse wakefields, longitudinal loss and transverse kick factors excited by the electron bunch in undulator section of the PSI-XFEL are given. The ordinary and in vacuum undulators are considered. For in vacuum undulator the modified technique for impedance calculation is developed.
CLASSE, Ithaca, New York
Wake fields arising from the discontinuities in the vacuum chamber produce energy spread. In an energy recovery linac (ERL), a spent beam is decelerated before it is dumped in order to use its energy for the acceleration of new beam. While the energy spread accumulated from wakes before deceleration does not increase during deceleration, it becomes more important relative to the beam's decreasing energy. Therefore, in an ERL, wakes can produce very significant energy spread in the beam as it is decelerated to the energy of the beam dump so that beam transport to the dump may become impractical. This effect can place a limit either on the maximum charge per bunch or on the wake field-budget for the ERL. As an example of these wake field effects, this paper discusses their impact for the present design of the Cornell ERL and estimates the effects for typical vacuum chamber components being considered.
SLAC, Menlo Park, California
Funding: SLAC/DOE Contract DE-AC02-76-SF00515
A state-of-the-art Machine Protection System for the SLAC Linac Coherent Light Source has been designed and built to shut off the beam within one pulse during 120 Hz operation to protect the facility from damage due to beam losses. Inputs from beam loss monitors, BPMs, toroids and position switches of insertable beam line devices are connected to a number of Link Node chassis placed along the beam line. Link Nodes are connected with a central Link Processor in a star topology on a dedicated gigabit Ethernet fiber network. The Link Processor, a Motorola MVME 6100, processes fault data at 360 Hz. After processing, rate limit commands are sent to mitigation devices at the injector and just upstream of the entrance of the sensitive undulator beam line. The beam's repetition rate is lowered according to the fault severity. The SLAC designed Link Nodes support up to 96 digital inputs and 8 digital outputs each. Analog signals are handled via standard IndustryPack (IP) cards placed on the Link Node motherboards with optional transition boards for signal conditioning. A database driven algorithm running on the Link Processor provides runtime loadable and swappable machine protection logic.