KEK, Ibaraki
A few issues on the path of the luminosity upgrade of KEKB B-Factory is described, including coherent synchrotron radiation, design of the interaction region, crab crossing, and high current operation. These issues will raise more obstacles on the upgrade with the High-Current Scheme. As an alternative, {¥it Nano-Beam Scheme} should be considered as a possible option for the upgrade.
KEK, Ibaraki
SLAC, Menlo Park, California
It is well known that the beam-beam interaction has a focusing effect and therefore causes a dynamical beating of beta function around the rings. This effect becomes greatly enhanced when a collider, such as KEKB, is operated near half integer. The beating makes it difficult to interpret the measurement of horizontal beam size. We derived two coupled nonlinear equations and solved them analytically to obtain the beam sizes at the interaction points, taking into account of dynamical beta and emittance. It has been demonstrated its effectiveness using actual measured data at the synchrotron light monitors. It is expected that it will be implemented in the control room.
LNLS, Campinas
We present several alternative designs of hybrid bending magnets based on the use of ferrite blocks with steel pole pieces to be used in the new Brazilian storage ring - LNLS2. Their main magnetic and mechanical characteristics are presented. Such models are compared to electromagnet magnets, and some advantages and disadvantages are listed, as well as a cost estimate.
USTC/NSRL, Hefei, Anhui
HALS(Hefei Advanced Light Source) is the electron storage ring of ultra-low emittance in process of design. Under this design, the quadrupole magnet with sextupole component must be mounted on which the βη is much bigger, to use enough the effect of compersation chromaticity of sextupole magnet field and to use sparingly the space in the same time . So the combined quadrupole and sextupole magnet must be designed, and have more strong sextupole component and restrain the production of high harmonic field. In this paper, the chocie of design scheme is discussed, and the calculation of combined quadrupole and sextupole mangnet design is given.
AML, Palm Bay, Florida
Magnets for beam steering, focusing and optical corrections often have demanding requirements on field strength, field uniformity, mechanical robustness and high radiation strength. The achievable field strength in normal conducting magnets is limited by resistive heating of the conductor. A break-through magnet technology, called “Direct Double-HelixTM” allows operation at current densities in excess of 100 A/mm2 with conventional water cooling. The conductive path generating the magnetic field is machined out of conductive cylinders, which are arranged as concentric structures. Geometrical constraints of conventional conductors, based on wire manufacturing, are eliminated. The coolant, typically water or air, is in direct contact with the conductor and yields very high cooling efficiency. Based on Double-HelixTM technology the conductor path is optimized for high field uniformity for accelerator magnets with arbitrary multipole order or combined function magnets. Advanced machining technologies, enable unprecedented magnet miniaturization. These magnets can operate at temperatures of several hundred degrees Celsius and can sustain high radiation levels.
CERN, Geneva
Fermilab, Batavia
Prior to the re-start of the Large Hadron Collider LHC in 2009 the protection system for superconducting magnets and bus bars QPS will be submitted to a substantial upgrade. The foreseen modifications will enhance the capability of the system in detecting problems related to the electrical interconnections between superconducting magnets as well as the detection of so-called symmetric quenches in the LHC main magnets. The paper will describe the design and implementation of the new protection layers and report as well on the commissioning of the system and first operational results.
LBNL, Berkeley, California
Funding: This work is supported by the Office of Science, United States Department of Energy under DOE contract DE-AC02-05CH11231.
The Muon Ionization Cooling Experiment (MICE) is an international collaboration that will demonstrate ionization cooling in a section of a realistic cooling channel using a muon beam at Rutherford Appleton Laboratory (RAL) in the UK. At each end of the cooling channel a spectrometer solenoid magnet consisting of five superconducting coils will provide a 4 tesla uniform field region. The scintillating fiber tracker within the magnet bore tubes will measure the emittance of the muon beam as it enters and exits the cooling channel. The 400 mm diameter warm bore, 3 meter long magnets incorporate a cold mass consisting of two coil sections wound on a single aluminum mandrel: a three-coil spectrometer magnet and a two-coil section that matches the solenoid uniform field into the MICE cooling channel. The fabrication of the spectrometer solenoids has been completed, and preliminary testing and field mapping of the magnets is nearly complete. The key design features of the spectrometer solenoid magnets are presented along with a summary of the progress on the testing and magnetic measurements.
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.
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.
BNL, Upton, Long Island, New York
Funding: Work performed under the auspices of U.S. Department of Energy, under contract DE-AC02-98CH10886
National Synchrotron Light Source II is a 3-GeV, 792-meter circumference, high-flux and high-brightness synchrotron radiation facility being constructed at Brookhaven National Laboratory. The storage ring vacuum chambers are made of extruded aluminium and the bending magnet photons are intercepted at discrete photon absorbers. The design of the storage ring vacuum system will be presented, with emphasis on vacuum chamber design and fabrication, pumping arrangements, photon beam tracking and absorber positioning, and interface with other accelerator systems. The evaluation of the aluminium chamber prototypes and RF shielded bellows will also be described.
NSRRC, Hsinchu
National Synchrotron Radiation Research Center (NSRRC) will build a new 3GeV, 400mA synchrotron accelerator machine. Several different IDs have been proposed and the corresponding front ends are designed. Beam lines of IU20, IU28, SW48 and EPU70 will be the phase I requirement. Due to different power load and density flux, fixed masks, photon absorber, slits, photon absorber and photon beam position monitor will all be customized to meet the beam line user requirements as well as the thermomechanical limits. Overall front end layout, analysis results of the high heat load components are illustrated; experiments of photon beam position monitor, front end pressure distribution due to thermal and photon stimulated desorption outgassing analysis, are also presented in this paper.
NSRRC, Hsinchu
Front End (FE) is the first area shapes radiation power to suit the need not only for protection but also for the beam line uses. About 14m long FE vacuum system will connect the ultra high vacuum (UHV) storage ring and beam line in Taiwan Photon Source (TPS). The Fixed mask (FM), photon absorber (PAB) and slit are the major high gas load components, especially in insertion Devices (ID) front ends, because of the synchrotron radiation. From the P(pressure)=Q(outgas)/S(pump) formula, there are some issues will be concerned to get lower vacuum pressure: The low outgassing rate of the vacuum chamber (Qthermal), the localization of the the pumps (IP and NEG) to pump down the outgassing of the photon simulated desorption(Qpsd), and the arrangement of the aperture and gas load . The basic pressure distribution of the bending magnet (BM) and ID front ends will be discussed.
USTC/NSRL, Hefei, Anhui
IHEP Beijing, Beijing
Titanium-Zirconium-Vanadium (TiZrV) nonevaporable getter (NEG), which can be fully activated after 4 hours heating at 200°;C, has been applied in many accelerators owing to the outstanding vacuum performance. In our experiments, TiZrV films have been deposited onto the inner face of stainless steel pipes via DC sputtering using argon gas as the sputtering gas. Samples have been investigated by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX) and X-ray Photoelectron Spectroscopy (XPS) to determine film composition and thickness, and by X-ray diffraction (XRD) to determine film structure and morphology. Second Electron Yields (SEY) of the TiZrV film have also been measured.
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.
Technion, Haifa
Funding: This work was supported by the Israel Science Foundation and the Kidron Foundation
We present results of an analysis demonstrating that electrons oscillating in a Penning trap may drain the energy stored in an adjacent active medium. For this process to happen, the electrons must become bunched and the energy imparted to the electrons allows them to leave the trap resulting into a train of bunches. Their angular frequency corresponds to medium’s resonance.
SLAC, Menlo Park, California
Funding: Work supported by US DOE contract DE-AC02-76SF00515.
Single-pass free electron lasers require high peak currents from ultra-short electron bunches to reach saturation and an accurate measurement of bunch length and longitudinal bunch profile is necessary to control the bunch compression process from low to high beam energy. The various state-of-the-art diagnostics methods from ps to fs time scales using coherent radiation detection and RF deflection techniques are presented.
UMD, College Park, Maryland
Funding: Work sponsored by the Department of Defense Office of Naval Research and the Joint Technology Office
Recent theoretical and experimental results advancing the state of the art in OTR diagnostics are presented. In particular, new facilities are beginning to operate in regimes where coherent effects are being seen in OTR diagnostics. The state of the art in theory and beam diagnostic data are reviewed and implications for next-generation diagnostic opportunities are presented.
ANL, Argonne
IIT, Chicago, Illinois
Tech-X, Boulder, Colorado
Funding: DOE. OHEP
We are modeling breakdown arcs in rf structures with Particle in Cell, (OOPIC Pro and VORPAL), Molecular Dynamics (HyDyn, LAMMPS), and an integrated radiation-magnetohyrodynamic package (HEIGHTS) to evaluate the basic parameters and mechanisms of rf discharges. We are evaluating the size, density, species temperature, radiation levels and other properties, to determine how the breakdown trigger works, what the growth times of the discharge are, effects of strong magnetic fields and what happens to both the arc and cavity energy. The goal is to have a complete picture of the plasma and its interaction with the wall. While we expect that these calculations will help guide further experimental studies, we have recently benchmarked model predictions against available experimental data on rise times of x ray pulses, and found a reasonable agreement.
IIT, Chicago, Illinois
Fermilab, Batavia
LBNL, Berkeley, California
ANL, Argonne
Funding: The United States Department of Energy
The accelerating gradient in a RF cavity is limited by many factors such as the surface material properties, RF frequency, the external magnetic field and the gas pressure inside the cavity. In the MuCool Program, RF cavities are studied with the aim of understanding these basic mechanisms and improving their maximum stable accelerating gradient. These cavities are being developed for muon ionization cooling channel for a Neutrino Factory or Muon Collider. We report studies using the 805 MHz and 201 MHz RF cavities in the MuCool Test Area (MTA) at Fermilab. New results include data from buttons of different materials mounted in the 805 MHz cavity, study of the accelerating gradient in the 201 MHz cavity and X-ray background radiation from the cavities due to Bremsstrahlung. The 201 MHz cavity has been shown to be stable at 19 MV/m at zero magnetic field, well in excess of its 16 MV/m design gradient. We will also discuss results from the 201 MHz cavity study in magnetic field and introduce the test of E × B effects with the 805 MHz box cavity.
KEK, Ibaraki
ISSP/SRL, Chiba
TIPC, BeiJing
A new vertical test facility for L-band multi-cell cavities has been completed in support of development efforts of ILC (International Linear Collider) and ERL (Energy Recovery Linac) projects at STF (Superconducting rf Test Facility) of KEK. The facility possesses a clean booth for pre-tuning the cavities, four cavity stands to prepare the cavities prior to vertical testing, a half-underground pit which accommodates up to two vertical cryostats which can be pumped and operated separately under a movable iron shield. Vertical testing of the cavities, with a 400 W high-power amplifier and with a temperature-mapping (T-mapping) and additional monitoring systems, is supervised from a control room which overlooks the entire facility. This paper describes the specific details of the facility and results from its initial pilot operation that was conducted in Summer-Fall of 2008.
Ankara University, Faculty of Sciences, Tandogan/Ankara
The Turkish Accelerator Complex (TAC) is a project for accelerator based fundamental and applied researches supported by Turkish State Planning Organization (DPT). The proposed complex is consisted of 1 GeV electron linac and 3.56 GeV positron ring for a charm factory and a few GeV proton linac. Apart from the particle factory, it is also planned to produce synchrotron radiation from positron ring. In this study the lattice structure design of the positron storage ring is made to produce the third generation synchrotron light. The parameters of complementary undulators and wigglers are determined. It is shown that the insertion devices with the proposed parameter sets produce maximal spectral brightness to cover 10 eV - 100 keV photon energy range.
BNL, Upton, Long Island, New York
Funding: Work supported by U.S. DOE, Contract No.DE-AC02-98CH10886
Top-off injection will be adopted in NSLS-II. To ensure no injected beam can pass into experimental beamlines with open photon shutters during top-off injection, simulation studies for possible machine fault scenarios are required. We compare two available simulation methods, backward (H. Nishimura-LBL) and forward tracking (A. Terebilo-SLAC). We also discuss the tracking settings, fault scenarios, apertures and interlocks considered in our analysis.
CLS, Saskatoon, Saskatchewan
Coherent Synchrotron Radiation (CSR) is produced when short bunch lengths are set up in the Canadian Light Source storage ring. To achieve short bunches large negative dispersion is introduced into the straight regions of the lattice such that the momentum compaction can be made to approach zero. In this way CSR has been observed using a few single bunches with currents up to 10 mA per bunch at the nominal operating energy of 2.9 GeV. Attempts produce CSR with low bunch currents in many bunches were unsuccessful at 2.9 GeV. At 1.5 GeV, however, it is possible to achieve CSR with a total of 5 mA stored in over 70 bunches. CSR production is enhanced by operating at a horizontal tune where the chromaticity can be kept near zero. Tracking simulations in longitudinal phase space indicate enhanced stability at tunes lower than the nominal tune. The optimum tune does not depend on the fractional tune but rather there is a tune "window" at the center of which stable longitudinal motion can be maximized.
DELTA, Dortmund
DELTA is a 1.5-GeV synchrotron radiation source at the TU Dortmund University (Germany) comprising a superconducting wiggler and a storage-ring FEL. Among other activities, it is planned to generate ultrashort and coherent VUV pulses by seeding the FEL in an optical-clystron configuration with femtosecond laser pulses and by producing higher harmonics. In addition to enabling laser-pump/VUV-probe experiments in material sciences with unprecedented time resolution, the seeding process gives rise to coherent and short radiation pulses in the THz regime. The paper reviews the status of DELTA and describes its new projects.
FZK, Karlsruhe
CAP Konstanz, Konstanz
Max-Planck Institute for Metal Research, Stuttgart
In a synchrotron radiation source coherent synchrotron radiation is emitted when the bunch length is comparable to the wavelength of the emitted radiation. To generate coherent THz (far IR) radiation, the ANKA storage ring is operated regularly with a dedicated low-alpha optics. Typical effective pulse lengths are of the order of 1 ps and below. In order to characterize the THz emission and beam oscillations in this mode a femtosecond laser system has been set up. This allows resolving the Terahertz electrical field by electro-optical sampling in a ZnTe crystal. The laser system consists of a 500 MHz repetition rate oscillator that can be phase locked to the repetition rate of the synchrotron. First results are presented. In contrast to previous approaches the high repetition rate is used in conjunction with a high frequency detection scheme in order to significantly increase the sensitivity of the detection. The discussion will concentrate on the limits in synchronization by locking the laser to either the bunch clock, a stripline signal in the ring or the visible light emission co-propagating with the THz radiation. The observations are compared to calculated pulse shapes.
FZK, Karlsruhe
Ruhr-Universität Bochum, Bochum
KIT, Karlsruhe
HZB, Berlin
DLR, Berlin
PTB, Berlin
BESSY GmbH, Berlin
Funding: This work has partly been supported by the Initiative and Networking Fund of the Helmholtz Association under contract number VH-NG-320.
In synchrotron radiation sources coherent radiation is emitted when the bunch length is comparable to or shorter than the wavelength of the emitted radiation. A detector system based on a superconducting NbN ultra-fast bolometer with an intrinsic response time of about 100 ps jointly developed by the University of Karlsruhe (Institute of micro- and nanoelectronic systems) and German Aerospace Center (Berlin) was used to resolve the radiation emitted from single bunches. This paper reports the observations made during measurements at the MLS and ANKA storage rings.
FZK, Karlsruhe
Ruhr-Universität Bochum, Bochum
KIT, Karlsruhe
A linac based coherent radiation source in the THz to mid-IR range is proposed. The TBONE machine will deliver pulses of radiation as short as a few fs in the frequency range from 0.1 to 150 THz with up to MW peak power. This combination of parameters will open up unprecedented opportunities in THz and infrared applications, such as e.g. microscopy or spectroscopy. This paper presents the main parameters and design considerations. Special emphasis is put on the study of suitable bunch compression and beam transport schemes.
INFN/LNF, Frascati (Roma)
Università di Roma I La Sapienza, Roma
INFN-Roma II, Roma
ELETTRA, Basovizza
Universita' degli Studi di Milano, Milano
Istituto Nazionale di Fisica Nucleare, Milano
A feasibility study for a dedicated beamline for a THz radiation source at SPARC is discussed. A radiofrequency electron gun followed by a compressor can generate trains of THz sub-picosecond electron pulses by illuminating the photocathode with a comb laser pulse. This structure of the beam can be used to produce coherent radiation. The quality of the coherent spectrum emitted by a comb beam is tightly connected to the electron micro-bunches lengths and to micro-pulses inter-distance. Beam dynamics studies are summarized here and compared to a conventional single bunch case, optimized for the THz radiation generation. The dynamics is studied within the SPARC system with the PARMELA code and with the RETAR code for the evaluation of the radiation.
JASRI/SPring-8, Hyogo-ken
SES, Hyogo-pref.
We have developed a kicker magnet system including a compact power supply to generate short pulse synchrotron radiation in the SPring-8 storage ring. One method to generate the short pulse synchrotron radiation is cutting out a synchrotron radiation coming from an tilted electron bunch with a slit. For this purpose, we induced a head-tail oscillation of an electron bunch due to non-zero vertical chromaticity excited by using a pulsed magnetic field. By using this scheme, the required specification to the magnet system is relaxed which leads to reduction of construction cost. Developed kicker magnet system can generate a short pulsed vertical field of about 3.6 mT within the 3 us to an electron bunch at 1 Hz repeat. With the kicker magnet system, we successfully observed a bunch profile which leans about 2 mm between head and tail position by a streak camera. We will report the detail setup of the kicker magnet system including compact power supply and the measurement system of beam profile, then discuss the comparisons between real beam motion and simulation results.
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.
The upgrade of the Advanced Light Source to enable top-off operation has been ongoing for the last four years. Activities over the last year have centered around radiation safety aspects, culminating in a systematic proof that top-off operation is equally safe as decaying beam operation, followed by commissioning and full user operations. Top-off operation at the ALS provides a very large increase in time-averaged brightness to ALS users (by about a factor of 10) as well as improvements in beam stability. The presentation will provide an overview of the radiation safety rationale, commissioning results, as well as experience in user operations.
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)
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.
ENEA C.R. Frascati, Frascati (Roma)
We explore the possibility of using free-electron laser (FEL) triggered cathodes to produce high quality e-beams. We propose a scheme which foresees cathodes operating either as thermionic and photo-cathodes, which can be exploited in devices using the same e-beam to drive the laser and the cathode. We discuss different modes of operation, in particular we consider oscillator FELs, in which the light from higher order harmonics, generated in the oscillator cavity, is used to light the cathode. The dynamics of the system is explored along with the technical solutions, necessary for the stability of the system. The Master Oscillator Power Amplifier FEL scheme is explored too. The use of the same e-beam, driving the photocathode and the FEL, makes the system naturally free of any synchronization problem, arising when an external laser is used. The device is a kind of regenerative amplifier in which the growth of the optical power can be controlled by using a proper detuning or misalignment of the optical cavity. Specific examples are reported. The use of this technique for an ab-initio control the Coherent Radiation Synchrotron instability is finally discussed too.
FEL/Duke University, Durham, North Carolina
PKU/IHIP, Beijing
Funding: Work supported by US Air Force Office of Scientific Research medical FEL grant FA9550-04-01-0086.
The storage ring based free electron laser (FEL) oscillator serves as a photon driver for the High Intensity Gamma-Ray Source (HIGS) at Duke University. The FEL cavity consists of two concave mirrors with a large radius of curvature of more than 27 m. Both cavity mirrors see very high intensity intracavity FEL power; the downstream mirror also receives higher harmonic spontaneous UV-VUV radiation of wigglers. The large heat load by various types of radiation can deform the mirror surface, causing FEL mode distortion. The FEL mirror can also be damaged by intense UV-VUV wiggler harmonic radiation. To mitigate these problems, a pair of water-cooled, in-vacuum apertures have been installed inside the FEL cavity. These apertures are ideal for manipulating the FEL transverse profile. This paper reports our study on the FEL transverse mode shaping using these apertures, including the characterization of the transverse mode structure of the FEL beam under a variety of operation conditions. These studies allow us to minimize the diffraction loss of the fundamental mode of the FEL while effectively reducing the impact of off-axis UV-VUV wiggler radiation on the FEL mirrors.
FEL/Duke University, Durham, North Carolina
Funding: This work is supported by US Air Force Office of Scientific Research medical FEL grant FA9550-04-01-0086.
The paper presents a novel technique of measuring the gain of a storage ring based FEL oscillator. As opposed to the conventional technique of measuring the FEL gain from its macro-pulse envelope, this new technique is based upon the measurement of pass-by-pass FELμpulses. To record the growth of the optical energy in the FEL micro-pulse train, we use fast photo-diodes and photo-multiplier tubes (PMTs). PMTs are usually employed at the very beginning of the FEL lasing development, while the photodiodes are used at the latter stages when the FEL power is fully developed and saturated. This new gain measurement technique provides a powerful tool to study the details of the FEL gain process starting from spontaneous radiation to saturation. It allows us to investigate five to seven orders of magnitude of the FEL energy growth. As fast photo-detectors with a sub-nanosecond time response become available, this new technique can be adopted for many oscillator FELs, including those driven by super-conducting linacs. Special attention is paid to the dynamic non-linearity issues of the photodiodes and PMTs associated with short length of FEL pulses.
FEL/Duke University, Durham, North Carolina
Funding: This work was supported by US Department of Defense Medical FEL Program as administered by the AROSR under contract number FA9550- 04-01-0086 and US Department of Energy grant DE-FG05-91ER40665.
Accurate simultaneous measurements of storage ring free-electron laser (SRFEL) average power output and electron beam energy spread has been achieved at the Duke FEL Laboratory. It is well known that the SRFEL power is limited by the electron beam synchrotron radiation power and the induced energy spread of the electron beam. The two-wiggler spectrum of an optical klystron can be used to determine the energy spread of the electron beam. Measuring the interference pattern of the modulated spontaneous spectrum with the FEL turned on, we are able to study the FEL power output as a function of electron beam energy spread. As the energy spread increases, the modulation in the two-wiggler spectrum reduces, resulting in a smaller FEL gain. During this process, the operation of an optical klystron degrades back to that of a conventional FEL. This paper reports our recent experiment study of transition of the FEL operation from an optical klystron to a conventional FEL.
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.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
STFC/DL, Daresbury, Warrington, Cheshire
UMAN, Manchester
FZD, Dresden
DESY, Hamburg
JLAB, Newport News, Virginia
KEK, Ibaraki
The University of Liverpool, Liverpool
STFC/DL/SRD, Daresbury, Warrington, Cheshire
STFC/RAL, Chilton, Didcot, Oxon
ACCEL, Bergisch Gladbach
ALICE (Accelerators and Lasers in Combined Experiments) is a 35 MeV energy recovery linac based light source. ALICE is being developed as an experimental test-bed for a broad suite of science and technology activities that make use of electron acceleration and ultra-short pulse laser techniques. This paper reports the progress made in accelerator commissioning and includes the results of measurement made on the commissioning beam. The steps taken to prepare the beam for short pulse operation as a driver for a Compton Back Scattered source and in preparation for the commissioning of the free electron laser are reported.
USTC/NSRL, Hefei, Anhui
In china, polymer radiation processing has become one of the most important processing industries. Electron beam accelerator or radioactive source is usually used as radiation processing source. For radiation crosslinking application, physical design, construction and testing of a electron beam facility is introduced because of it’s much higher dose rate and efficiency. Main part of this facility is a 10MeV traveling wave electron linac with constant impedance accelerating structure. It is the first electron beam facility designed for polymer radiation processing by National Synchrotron Radiation Laboratory (NSRL) in China. In the paper, a start to end simulation is finished to optimize electron beam dynamics in the linac. Measurement results of some subassemblies are presented. The linac construction has been finished just now. Testing experiments prove that the facility can work well for radiation crosslinking application.
KAERI, Daejon
Samsung SDI Co. Ltd., Gyeonggi-do
Kyungpook National University, Daegu
SAMSUNG SDI CO. LTD, Gyeonggi-do
Funding: This work was performed as a part of the Proton Engineering Frontier Project supported by the Ministry of Education, Science and Technology of Korea.
The sample activation during proton beam irradiation sometimes interrupt the measurement and investigation of the instant changes of the samples after irradiation. During the experiments for nano particle fabrications with ~35MeV and ~20uA, we found that the samples was highly activated after the proton beam irradiation. To investigate the source of the rdadiation from the samples, we measured the energy spectrum of gamma ray using HPGe spectroscopy. The results was compared to the calculated results by the MCNP code simulation. The sample was small amount of heavy metal dispersed in enthanol in the beaker made of quartz.
The University of Tokyo, Nuclear Professional School, Ibaraki-ken
AIST, Tsukuba, Ibaraki
University of Tokyo, Tokyo
Tohoku University, Graduate School of Engineering, Sendai
In X-ray Drug Delivery System, anticancer drugs containing Pt, such as cisplatin and dachplatin, and Au colloid contrast agent are surrounded by polymers (micelle, PEG (polyethylene glycol), etc.).Ttheir sizes are controlled to be 20-100 nm. Since holes of capillary to organ are as large as 100 nm in only cancer, those large particles can be accumulated in cancer effectively. That is called as EPR (Extended Penetration and Retention effect). We have observed the distribution of Pt of dachplatin-micelle in cancer of mouse’s pancreas by X-ray fluorescence analysis using 10 μm pinpoint 15 keV X-ray by SPring8. Further, in-vitro- and in-vivo-experiments of Au colloid PEG are under way. It is expected to be used as contrast agent for dynamic tracking treatment for moving cancer. Imaging properties for polychromatic X-rays from X-ray tube and monochromatic Compton source are numerically analyzed and discussed. We continue to analyze radiation enhancement by Auger electrons and successive characteristic X-rays and its toxic effect to cancer.
LBNL, Berkeley, California
Funding: This work was supported by DOE and NSA.
The integration of scanning probes with ion beams enables non-destructive, nanometer scale imaging and alignment of ion beams to regions of interest in to be implanted device structures. We describe our basic approach which uses piezo-resistive force sensors and pierced cantilvers as dynamic shadow masks, integtrated with low current (<1 mA), low energy (<1 MeV) ion beams from a series of ion sources (ECR and EBIT). Single ion sensing strategies based on charge transients induced in devices and detection of secondary electrons are discussed. We will show results form our studies of single ion doping of 50 nm scale transistors in tests of radiation response mapping of transistors with this technique.
RISE, Tokyo
ISIR, Osaka
AIST, Tsukuba, Ibaraki
RIKEN, Saitama
A pulse radiolysis method is very useful in clarifying primary processes of radiation chemistry. At Waseda University, compact pico-second and nano-second pulse radiolysis systems have been developing. A pico-second system is based on pump-probe method. IR and UV pico-second laser pulses are generated from Nd:YLF mode-locked laser and used for generating of white light continuum as analyzing light and irradiating to photo-cathode RF gun, respectively. Recently, we have installed a new photo-cathode RF gun with Cs-Te cathode which has high quantum efficiency, so we have succeeded in improving optical density and S/N ratio of our pulse radiolysis system. We are now developing a new nano-second system which can get time profile with only one-shot and follow up wider time region than pico-second system. In the past, this system has been used He-Ne laser as analyzing light, but it can measure only 633nm. Instead of He-Ne laser, this system adopts Xe flush lamp which has broad spectrum as analyzing light. As system evaluation experiments, we tried to get time profile of some species. In this conference, present status and future plans of our pulse radiolysis systems will be reported.
TUB, Beijing
The preliminary experiments and three-dimensional (3D) particle-in-cell (PIC) simulations of terahertz (THz) coherent transition radiation (CTR) performed at the Accelerator Laboratory of Tsinghua University are reported in this paper. THz radiation is generated from the interactions of Titanium foil with the ultrashort electron beam produced by the photocathode RF gun. The frequency and power of radiation are measured with the Martin-Pupllet interferometer and Gollay Cell detector, respectively. The radiation characteristics depending on the foil properties are preliminarily studied with the experiments and PIC simulations. On the other hand, the distribution of radiation field pattern and energy are studied by numerical calculated, and those results are in agreement with the PIC simulations.
NSRRC, Hsinchu
A low run-out rotating sample stage is under development to realize a precise resolution within 30 nm on the horizontal plane for the end-station of transmission X-ray microscope (TXM) at NSRRC. The main assembly consists of a commercial rotation stage with run-out less than 1 μm, six capacitive sensors, one master ball, one flat and a horizontal adjusting stage. Error sources (including the profile of the master ball, run-out of the master ball in horizontal and vertical directions, flat plate) are separated from stage and the sensor readings can be down to the nanometer level. A feedback method is proposed to compensate the systematic errors and keeps the samples with little run-out and axial motion in the level of several tens nanometer. The details and tests of the rotation stage are presented in this paper.
UCLA, Los Angeles, California
BNL, Upton, Long Island, New York
Coherent radiation emitted by relativistic electron bunches traversing the edge regions of dipole magnets in a chicane bunch compressor was extracted and transported for measurement, using a dedicated terahertz beamline at the Accelerator Test Facility (ATF) at Brookhaven National Laboratory (BNL). Measurements include frequency spectrum and polarization of the radiation. The measurements are compared to predictions from QUINDI, a new simulation code developed at UCLA to model radiation emitted by charged particles in bending systems. Simulations and measurements indicate that because of interference of radiation from the two magnet edges, the edge radiation is suppressed at long wavelengths. In addition to being a source of broadband terahertz radiation, the system is also used as a non-invasive, single-shot, relative bunch length diagnostic to monitor compression in the chicane.
CERN, Geneva
IN2P3 IPNL, Villeurbanne
INFN/LNL, Legnaro (PD)
Istituto Nazionale di Fisica Nucleare, Milano
The CNGS facility (CERN Neutrinos to Gran Sasso) aims at directly detecting muon-neutrino to tau-neutrino oscillations. An intense muon-neutrino beam (1017 muon-neutrino per day) is generated at CERN and directed over 732 km towards the Gran Sasso National Laboratory, LNGS, in Italy, where two large and complex detectors, OPERA and ICARUS, are located. After a brief overview of the facility, the major events since its commissioning in 2006 will be discussed. Emphasis will be given on the design challenges and operation constraints coupled to such a high-intensity facility summarizing the acquired experience. Highlights of the 2008 operations, which was the first complete year of physics in CNGS with 1.78·1019 protons delivered on target, will be presented.
JLAB, Newport News, Virginia
PKU/IHIP, Beijing
Funding: DOE Contract DE-AC05-060R23177; China Scholarship Council
This paper introduces a single lens laser beam shaper which is capable of redistributing a beam with a Gaussian profile to a super-Gaussian profile. Both geometrical and diffractive optical modelings are performed on a typical single lens shaper that shows significant reduction of destructive effects on the beam uniformity over those with sharp-edges.
KEK, Ibaraki
Thick carbon foils (>300 ug/cm2)has been used for stripping of H- ion beam at the 3GeV Rapid Cycling Synchrotron (3GeV-RCS) of J-PARC, where foils with long lifetime against high temperature >1800 °K are strongly required for efficient accelerator operations. The key parameter to the foil lifetime is foil temperature attained during irradiation. We have recently developed a new irradiation system for lifetime measurement using the KEK 650 keV Cockcroft-Walton accelerator with high current pulsed and dc H- beam, which can simulate the high-energy depositions upon foils in the RCS. During irradiation tests by this system, the temperature of foil is measured by a thermometer in a dc mode, and by using a photo-transistor in a pulsed mode. This paper describes the pulsed measurements with 5-10 mApeak, 0.1-0.5 msec duration and 25 Hz repetition.
JAEA, Ibaraki-ken
RIST, Ibaraki
NSCL, East Lansing, Michigan
Funding: The funding information for R.M. Ronningen is U.S. Department of Energy Grant Number DE-FG02-08ER41548.
The Particle and Heavy Ion Transport Code (PHITS)* has been typically used to predict radiation levels around high-energy (above 100 MeV/u) heavy-ion accelerator facilities. However, predictions of radiation levels around low-energy (around 10 MeV/u) heavy-ion facilities are also desirable, but the reliability of PHITS at low energies has not been investigated. In this work, neutron energy spectra from 10 MeV/u 12C and 16O ions incident on C and Cu targets have been calculated using the quantum molecular dynamics (QMD) model coupled to the generalized evaporation model (GEM) in PHITS. In particular, the influence of the “switching time”, defined as the time when the QMD calculation is stopped and the calculation switches to the GEM model, was studied. The calculated neutron energy spectra obtained using a value of 100 fm/c for the switching time agree well with the experimental data. We have also used PHITS to simulate an experimental study by Ohnesorge et al.**, by calculating neutron dose equivalent rates, for 3-16 MeV/u 12C, 16O and 20Ne beams incident on Fe, Ni and Cu targets. The calculated neutron dose equivalent rates agree well with the data.
*H. Iwase, K. Niita and T. Nakamura, J. Nucl. Sci. Technol. 39, 1142 (2002).
**W.F. Ohnesorge, H.M.Butler, C.B.Fulmer and S.W.Mosko, Health Physics 39, 633 (1980).
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.
USTC/NSRL, Hefei, Anhui
Funding: Work supported by National Natural Science Foundation of China (No.10175062 & 10575100).
The light pulse interval adjustment at Hefei Light Source (HLS) can be realized by using pulsed orbit bump technique, which requires for high-frequency repetitive, high magnetic flux density, short pulse kicker magnet system of which the power supply modulator should be specially designed. The technique of solid state modulator based on MOSFET is being developed in National synchrotron Radiation Laboratory (NSRL). In this paper, the design of a prototype of solid-state modulator with 20 MOSFETs in parallel is introduced, including triggering system, drive circuit, transformer configuration. The oscillation induced by parasitic capacitance and inductance is discussed. This prototype with four stage adder can achieve 100ns width power pulse output with 112A, 2.4 kV to the kicker.
NSRRC, Hsinchu
The correction power supplies are working in the storage ring of NSRRC. They are required to output high quality and high performance current that is long-term stability and output current ripple are required to be under 100ppm. The storage ring consists of more than one hundred units of independence power supplies working together when beam current in 1.5GeV status. The power supplies also are all working under current mode. We just build a new conduction EMI (Electromagnetic Interference) and EMC (Electromagnetic Compatibility) measurement laboratory to measure and test the switching power supplies. That is AC to DC voltage bus source to supply for the switching correction power supply. Using the LISN to obtain conduction noise, it is high frequency voltage noise generated by the switching mode of power supply conduction noise. The current signal pass AC source impendence stabilize network LISN and spectrum analyzer will obtain the conduction noise. We can use a noise separator to separate common EMI noise and difference-mode EMI noise for EMI filtering design. The measurement result will be illustrated in the paper.
CERN, Geneva
The modification of microwave signals passing through an electron cloud can be used as a diagnostic tool for detecting its presence and as a measure for its effective density. This observation method was demonstrated in pioneering measurements at the CERN SPS in 2003 with protons and at PEP-II in 2006 with positron beams in the particle accelerator field. Results and applications of this technique are discussed as well as limitations and possible difficulties. A strong enhancement of the electron related signals due to cyclotron resonance is theoretically predicted and has been observed in different machines. The application of this method can also be extended for space applications and plasma physics where microwave diagnostics is known and used since many years. The question whether suitably chosen microwaves might also be employed for electron-cloud suppression will be addressed. An electron cloud may also emit microwaves itself and the intensity of this emission depends on external parameters such as the electrical bias field and resonator frequencies related to trapped mode resonances in a beam-pipe.
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.
LBNL, Berkeley, California
Funding: Supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
ALS has been upgraded by adding Top-Off Mode, a new mode of operation to the existing modes of Fill and Stored Beam. The Top-Off Mode permits injection of 1.9GeV electron beam into the Storage Ring, with the safety shutters open, once certain strict conditions are met and maintained. Top-Off Mode enables User operation without an interruption caused by mode switching between the Stored Beam Mode when safety shutters are open, to the Fill Mode with the safety shutters closed and back. The conditions necessary to permit Top-Off Mode are; stored beam is present, the energies are matched between the injector and storage ring, a select set of storage ring lattice magnets are operating at the correct current levels, and radiation losses are minimized. If certain combinations of these conditions are not met, a potentially dangerous condition of injecting electrons down a users beam line can exist. Therefore a system of mode control, energy match, lattice match and stored beam interlocks are needed to control the injected beam prohibiting potentially dangerous conditions. In this paper we will present the Top-Off Mode Beam Interlock system requirements, design, and operational parameters.
Omega-P, Inc., New Haven, Connecticut
KEK, Ibaraki
Fermilab, Batavia
Measurements are reported for a one-third version of a L-band high-power ferroelectric phase shifter. The device is designed to allow fast adjustments of cavity coupling in an accelerator where microphonics, RF source fluctuations, or another uncontrolled fluctuations could cause undesired emittance growth. Experimental measurements of switching speed, phase shift and insertion loss vs. externally-applied voltage are presented. An average switching rate of 0.5 ns or better for each degree of RF phase has been observed.
PSI, Villigen
CANDLE, Yerevan
Recently tentative top-up operation of the Swiss Light Source (SLS) storage ring at low momentum compaction factor has been started. We will present an analysis of the longitudinal dynamics and simulations of the injection process, and explain our method to ensure closed orbit stability. First experimental results will be shown and compared to the model predictions.
PTB, Berlin
HZB, Berlin
The Physikalisch-Technische Bundesanstalt (PTB), the German national metrology institute is operating the low-energy electron storage ring Metrology Light Source (MLS) in Berlin-Adlershof in close cooperation with the BESSY GmbH. The MLS is designed and prepared for a special machine optics mode (low-alpha operation mode) based on a sextupole and octupole correction scheme, for the production of coherent synchrotron radiation in the FIR and THz region. At the MLS two bending magnet beamlines dedicated to the use of IR and THz synchrotron radiation were built. An IR beamline optimized for the MIR to FIR is now in operation. First measurements at this beamline showed the potential of the MLS as a source of THz radiation*. However, the propagation of sub-terahertz electromagnetic waves from the source point to the experiment through such a typical IR beamline is strongly affected by diffraction. This is why we decided to build a dedicated THz beamline with larger extraction optics. We present first results from the commissioning of the dedicated THz beamline.
*R. Müller et al., Proc. of EPAC08, 2058 (2008)
SLAC, Menlo Park, California
Funding: Work sponsored by U.S. Department of Energy Contract DE-AC03-76SF00515 and Office of Basic Energy Sciences, Division of Chemical Sciences.
Recent experimental results and advances in the theory of short-bunch dynamics have lead to an improved understanding of the parameters and limitations of short-bunch operation in storage rings. In this paper the measurement and analysis of short bunches under a variety of operational parameters is reported for SPEAR3.
SLAC, Menlo Park, California
A preliminary plan for an infrared or terahertz beamline at SSRL is studied. Using chicane in a straight section allows us to redesign a section of the vacuum chamber and extract infrared/terahertz beam with a large acceptance. Under the low alpha operational mode, the terahertz beam power can be greatly enhanced by the coherent synchrotron radiation (CSR) effect. Calculations of photon beam flux and brightness and the shielding and CSR effects are presented.
USTC/NSRL, Hefei, Anhui
Hefei Light Source is a second generation VUV light source, whose performance cannot meet the requirements of synchrotron radiation users at the present time. One year ago, the concept of the Hefei Advanced Light Source, whose main features are ultra low beam emittance and high brilliance in VUV and soft X-ray range, was brought forward. In the preliminary design study, a medium scale storage ring and multi bend achromat focusing structure were adopted to achieve beam emittance lower than 0.2 nm.rad. Linear and nonlinear parameter optimizations were performed to obtain large on-momentum and off-momentum dynamic aperture. The design status will be introduced briefly in the presentation.
SLAC, Menlo Park, California
LBNL, Berkeley, California
Funding: This work was supported by U.S. DOE contracts DE-AC03-76SF00515 and under the auspices of the Office of Science, U.S. DOE under Contract No. DE-AC02-05CH11231.
Recently Stupakov* has suggested a scheme entitled echo-enabled harmonic generation (EEHG) for producing short wavelength FEL radiation that allows far higher harmonic numbers to be accessed as compared with the normal limit arising from incoherent energy spread. We have studied the feasibility of a single EEHG stage to generate coherent radiation in the "water window" (2- 4 nm wavelength) directly from a UV seed laser at ~200-nm wavelength. By adjusting the temporal overlap region of the two lasers producing energy modulation in the EEHG scheme, we find it may be possible to vary the duration of the output coherent soft x-ray pulse. We present time-dependent simulation results which explore these ideas and also examine the sensitivity of the scheme to various input electron beam parameters.
*G. Stupakov, Preprint SLAC-PUB-13445
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).
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
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)
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.
Tohoku University, School of Scinece, Sendai
To develop a coherent Terahertz (THz) light sources, producing very short electron bunch has been progressed at Laboratory of Nuclear Science, Tohoku University. We have developed an independently-tunable-cells (ITC) RF gun consisted with two cavities and thermionic cathode in order to produce bunch length around a hundred femto-second. Possibility of pre-bunched FEL is investigated by numerical simulations. In case of the bunch length shorter than wavelength, the FEL interaction seems to be different from conventional way. High intensity and short FEL pulse is possibly obtained *. In a broad band regime, coherent spontaneous THz radiation has been developed. A ring type source consisted with isochronous arcs can provide the coherent THz pulses from every bending magnets. The project has aimed multi-user facility **. In addition, a compact DC gun is also under development. Measured normalized emittance is less than 1μrad for a beam energy of 50 keV and a beam current of 300 mA. This low emittance beam is quite suitable for driving Smith-Purcell Backward Wave Oscillator FEL in THz region. Detail of the DC gun and prospect will be presented ***.
*M. Yasuda et al., Proc. FEL08, (2008) in press.
**H. Hama et al., New J. Phys. 8 (2006) 292.
***K. Kasamsook et al., Proc. FEL07, (2007) 417 - 420.
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.
YerPhI, Yerevan
Diffusive Radiation is originated by the passage of charged particles through a randomly inhomogeneous medium. DR appears when the conditions for multiple scattering of pseudophotons are fulfilled in the medium. Such a situation can be realized when a charged particle slides over a rough surface. One of the important properties of DR is that the maximum of emission lies at large angles from particle velocity direction. Therefore it can be used for detection of beam touch to the accelerators vacuum chamber wall in case when generated photons will be observed on the opposite side of vacuum chamber. Such a diagnostics can be especially useful for observation of storage rings beam halo.
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.
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.
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.
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.
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
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.
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.
BNL, Upton, Long Island, New York
Funding: Work performed under the auspices of the US DOE.
A staged approach towards the development of a high energy RHIC-based electron-ion collider has been proposed in BNL*. In the first stage, a medium-energy electron-ion collider (MEeIC) would be constructed. It would utilize a high energy ion beam, accelerated in one of the two existing rings of the RHIC facility, colliding with a medium energy (4GeV) electron beam, generated by a proposed energy-recovery linac. As a part of the design and investigation of the interaction region, it is necessary to estimate the level of background radiation in the physics experiment detector. The primary radiation distribution can be readily calculated by employing electromagnetic theory. However, the secondary radiation is due to a diffuse scattering of soft X-ray off rough surfaces. In this paper, we first calculate the primary radiation spectrum and apply the kinematic Born approximation deduced from the scattering dynamics. Next, the diffuse scattering cross section is calculated as a function of the material and surface properties of the MEeIC vacuum system. Finally, the minimization of the radiation background level by the choices of the material and surface properties is discussed.
*V. Ptitsyn et al., “MEeIC - staging approach to eRHIC”, these proceedings.
BNL, Upton, Long Island, New York
As first step in a staged approach towards a RHIC-based electron-ion collider, installation of a 4 GeV energy-recovery linac in one of the RHIC interaction regions is currently under investigation. To minimize costs, the interaction region of this collider has to utilize the present RHIC magnets for focussing of the high-energy ion beam. Meanwhile, electron low-beta focussing needs to be added in the limited space available between the existing separator dipoles. We discuss the challenges we are facing and present the current design status of this e-A interaction region.
SLAC, Menlo Park, California
DESY, Hamburg
OXFORDphysics, Oxford, Oxon
ISU, Ames
CLASSE, Ithaca, New York
BNL, Upton, Long Island, New York
KEK, Ibaraki
Funding: Work supported in part by US DOE contract DE-AC02-76-SF00515.
The Interaction Region of the International Linear Collider* is based on two experimental detectors working in a push-pull mode. A time efficient implementation of this model sets specific requirements and challenges for many detector and machine systems, in particular the IR magnets, the cryogenics and the alignment system, the beamline shielding, the detector design and the overall integration. This paper attempts to separate the functional requirements of a push pull interaction region and machine detector interface from the conceptual and technical solutions being proposed by the ILC Beam Delivery Group and the three detector concepts**. As such, we hope that it provides a set of ground rules for interpreting and evaluation the MDI parts of the proposed detector concept’s Letters of Intent, due March 2009. The authors of the present paper are the leaders of the IR Integration Working Group within Global Design Effort Beam Delivery System and the representatives from each detector concept submitting the Letters Of Intent.
*ILC Reference Design Report, ILC-Report-2007-01.
**Materials of IR Engineering Design Workshop, 2007, http://www-conf.slac.stanford.edu/ireng07
KIT, Karlsruhe
CERN, Geneva
NCP, Islamabad
Fermilab, Batavia
We report about generic halo and tail simulations and estimates. Previous studies were mainly focused on very high energies as relevant for the beam delivery systems of linear colliders. We have now studied, applied and extended these simulations to lower energies as relevant for the CLIC drive beam.
ORNL, Oak Ridge, Tennessee
CERN, Geneva
BNL, Upton, Long Island, New York
PU, Princeton, New Jersey
Funding: U.S. Department of Energy contract DE-AC05-00OR22725
Operation of a mercury jet delivery system is presented. The delivery system is part of the Mercury Intense Target (MERIT) Experiment, a proof-of-principle experiment conducted at CERN in 2007 which demonstrated the feasibility of using an unconstrained jet of mercury as a target for a future Neutrino Factory or Muon Collider. The Hg system was designed to produce a 1-cm-diameter, 20 m/s Hg jet inside a high-field (15 Tesla), 15-cm-bore solenoid magnet. A high-speed optical diagnostic system allowed observation of the interaction of the jet with both 14- and 24-GeV proton beams. Performance of the Hg system during the in-beam experiment will be presented.
KEK, Ibaraki
Fermilab, Batavia
INFN/LASA, Segrate (MI)
DESY, Hamburg
In an attempt at demonstrating an average field gradient of 31.5 MV/m as per the design accelerating gradient for ILC, a program called S1-Global is in progress as an international research collaboration among KEK, INFN, FNAL, DESY and SLAC. The S1-Global cryomodule will contain eight superconducting cavities from FNAL, DESY and KEK. The cryomodule will be constructed by joining two half-size cryomodules, each 6 m in length. The module containing four cavities from FNAL and DESY will be constructed by INFN. The design of this module is based on an improved 3rd generation TTF design. KEK will modify the 6-meter STF cryomodule to contain four KEK cavities. The designs of the cryomodules are ongoing between these laboratories, and the operation of the system is scheduled at the KEK-STF from June 2010. In this paper, the S1-Global cryomodule plan and the module design will be presented. ‘S1-Global collaboration’ as a co-author.
TIPC, BeiJing
IHEP Beijing, Beijing
IHEP Beiing, Beijing
Technical Institute of Physics and Chemistry, Beijing
Graduate School of the Chinese Academy of Sciences, Beijing
Funding: Work supported by NSFC 10525525
In order to obtain the design, manufacture and operational experiences on the SRF cryomodule toward ILC, a test cryomodule for 1.3GHz single 9-cell SC cavity was designed by IHEP (Institute of High Energy Physics) and TIPC (Technical Institute of Physics and Chemistry) jointly. This cryomodule will be used as a 1.3GHz 9 cell SC cavity horizontal test facility. The cryogenic system for the cryomodule is designed and will be operated at 2.0K, with the saturated superfluid helium. The major requirements, design, simulation results of the cryomodule are reported in the paper. This key component of a superconducting accelerator test unit will be built in the near future at IHEP.
Bruce Technologies Inc., North Billerica, MA
D-Pace, Nelson, British Columbia
Many of today’s PET cyclotrons are delivered from the factory for fully-automated “black box” operation in a hospital-based clinical program. Simplicity and ease of operation by non-specialists is desired, and this is achieved in-part through relatively low current targets bolted directly to the PET cyclotron’s main vacuum tank. However, commercial-scale production of short-lived radiopharmaceuticals is becoming increasingly prevalent where substantially higher-current target operation* requiring greater optimization of beam parameters through compact external beamlines**,*** is necessary to meet ever-more demanding production schedules and delivery commitments. This paper describes a system which incorporates the highest current and highest power PET water targets and a short well-instrumented beamline for beam centring/focusing and maximum productivity.
*M. Stokely et al, WTTC11, Cambridge, 2006, p.{10}2.
**M.P. Dehnel et al, NIM B 261, 2007, p. 809.
***J.E. Theroux et al, CYC2007, Giardini Naxos, Italy, 2007, p. 361.
CERN, Geneva
Phase I collimators, equipped with Carbon-Carbon jaws, effectively met specifications for the early phase of LHC operation. However, the choice of carbon-based materials is expected to limit the nominal beam intensity mainly because of the high RF impedance and limited efficiency of the collimators. Moreover, C/C may be degraded by high radiation doses. To overcome these limitations, new Phase II secondary collimators will complement the existing system. Their extremely challenging requirements impose a thorough material investigation effort aiming at identifying novel materials combining very diverse properties. Relevant figures of merit have been identified to classify materials: Metal-diamonds composites look a promising choice as they combine good thermal, structural and stability properties. Molybdenum is interesting for its good thermal stability. Ceramics with non-conventional RF performances are also being evaluated. The challenges posed by the development and industrialization of these materials are addressed in a collaboration program, involving academic and industrial partners and complementing material research with an innovative design.
Fermilab, Batavia
Funding: Work supported by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
The Fermilab Main Injector is moving toward providing 400 kW of 120 GeV proton beams using slip stacking injection of eleven Booster batches. Loss of 5% of the beam at or near injection energy results in 1.5 kW of beam loss. A collimation system has been implemented to localize this loss with the design emphasis on beam not captured in the accelerating rf buckets. More than 90% of these losses are captured in the collimation region. We will report on the construction, commissioning and operation of this collimation system. Commissioning studies and loss measurement tools will be discussed. Residual radiation monitoring of the Main Injector machine components since 2004 will be used to demonstrate the effectiveness and limitations of these efforts.
STFC/RAL, Chilton, Didcot, Oxon
Kyoto University, Kyoto
KEK, Ibaraki
Funding: Science and Technology Facilities Council
The T2K experiment will utilise the highest pulsed power proton beam ever built to generate an intense beam of neutrinos. This uses the conventional technique of colliding the 0.75 MW 30 GeV proton beam with a graphite target and using a magnetic horn system to collect pions of one charge and focus them into a decay volume where the neutrino beam is produced. The target is a two interaction length (900 mm long) graphite target supported directly within the bore of the first magnetic horn which generates the required field with a pulsed current of 300 kA. This paper describes the design and development of the target system required to meet the demanding requirements of the T2K facility. Challenges include radiation damage, shock waves resulting from a 100 K temperature rise in the graphite material during each beam spill, design and optimisation of the helium coolant flow, and integration with the pulsed magnetic horn. Conceptual and detailed engineering studies were required to develop a target system that could satisfy these requirements and could also be replaced remotely in the event of a target failure.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
JAI, Oxford
The postlinac energy collimation system of the Compact Linear Collider (CLIC) protects the machine by intercepting mis-steered beams due to possible failure modes in the linac. The collimation is based in a spoiler-absorber scheme. The mission of the spoiler is to protect the main downstream absorber by dispersing the beam, via multiple Coulomb scattering, in case of a direct hit. We present the design of energy spoilers for CLIC, considering the following requirements: spoiler survival to the deep impact of an entire bunch train, and minimisation of spoiler wakefield effects during normal operation. Different configurations of the spoiler are studied in order to achieve an optimum performance.
CERN, Geneva
Personnel access to the LHC tunnel will be restricted to varying extents during the life of the machine due to radiation and cryogenic hazards. For this reason a remotely operated modular inspection train, (TIM) running on the LHC tunnel’s overhead monorail has been developed. In order to be compatible with the LHC personnel access system, a small section train that can pass through small openings at the top of sector doors has now been produced. The basic train can be used for remote visual inspection; additional modules give the capability of carrying out remote measurement of radiation levels, environmental conditions around the tunnel, and even remote measurement of the precise position of machine elements such as collimators. The paper outlines the design, development and operation of the equipment including preparation of the infrastructure. Key features of the trains are described along with future developments and intervention scenarios.
CERN, Geneva
Beam losses in high-energy particle accelerators are responsible for beam lifetime degradation. In the LHC beam losses will create a shower of particles while interacting with materials from the beam pipes and surroundings, resulting in a partial activation of material in the tunnel. Efforts have been made during the accelerator design to monitor and to reduce the activation induced by beam losses. Traceability for all vacuum components has been established providing a tool to follow-up individually each component or subcomponents installed in the tunnel, regardless of their future destination e.g. recycling or disposal. In the latter case, the history of vacuum components will allow calculating the beam-induced activation and permit comparisons with in-situ and ex-situ measurements. This zoning will also help to reduce collective and individual radiation doses to personnel during interventions. The paper presents the vacuum system layout and describes the LHC vacuum zoning and its implementation using an ORACLE© database.
NSRRC, Hsinchu
The air conditioning system for the 3.0 GeV Taiwan Photon Source (TPS) is currently under the design phase. This paper presents the latest design of the air conditioning system for the TPS. The capacity of the air handling unit (AHU), the dimension and layout of the wind duct were specified. Numerical analysis was applied to simulate the air flow and temperature distribution in one of 24 sections storage ring. A 1/12 experimental hall was also modelled. The air flow of this area was simulated.
NSRRC, Hsinchu
To cope with increasing power cost and to confront huge power consumption of the Taiwan Photon Source (TPS) in the future, we have been conducting several power saving schemes since 2006 in the National Synchrotron Radiation Research Center (NSRRC). Those power saving schemes include optimization of chiller operation, air conditioning system improvement, power factor improvement and the lighting system improvement.
Georgetown University, Washington
NRL, Washington, DC
Icarus Research, Inc., Bethesda, Maryland
Funding: This work is supported by the Office of Naval Research and the Department of Energy
Theoretical work* on electro-optic shock produced from the interaction of intense laser radiation with ~1% critical plasma suggests that second harmonic radiation will be emitted at the Cherenkov angle. This radiation pattern is produced under similar conditions as when off-axis electrons** were observed. These electrons are of particular interest since they are well suited for external injection into a laser wakefield acceleration structure. Recent experimental results at the U.S. Naval Research Laboratory, using a 10 TW, 50 fs, Ti-Sapphire laser, have shown the existence of such a second harmonic ring. Characterization of this optical radiation and its relationship to off-axis electrons will be presented.
*D. F. Gordon et al., Phys. Rev. Lett. {10}1, 45004 (2008).
**D. Kaganovich et al. Phys. Rev. Lett. {10}0, 215002 (2008).
Instituto Superior Tecnico, Lisbon
UCLA, Los Angeles, California
Funding: F.C.Gulbenkian, F.C.T. [SFRH/BD/35749/2007, SFRH/BD/39523/2007, PTDC/FIS/66823/2006 (Portugal)], and European Community (project EuroLeap, contract #028514)
It is now accepted that self-trapped electrons in a laser wakefield accelerator operating in the "bubble" regime undergo strong periodic oscillations about the wakefield axis because of the focusing force provided by the ions. This betatron motion of the off-axis electrons results in the emission of x-ray radiation strongly peaked in the forward direction. Even though the x-rays are broadband with a synchrotron-like spectrum, their brightness can be quite high because of their short pulse duration and strong collimation. We employ particle tracking in particle in cell simulations with OSIRIS*, combined with a post-processing radiation diagnostic, to evaluate the features of the radiation mechanisms of accelerated electrons in LWFA experiments. We show and discuss results for a 1.5 GeV laser wakefield accelerator stage. A study of the angular dependence of the radiated power is also presented and compared with theoretical models. This analysis also allows for the direct calculation of the radiation losses of the self-injected bunch.
*R. A. Fonseca et al, LNCS 2329, III-342, Springer-Verlag, (2002)
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).
UCLA, Los Angeles, California
Funding: Work supported by DOE.
We report experimental observation of narrow-bandwidth pulses of coherent Cherenkov radiation produced when a sub-picosecond electron bunch travels along the axis of a hollow circular cylindrical dielectric-loaded waveguide. For an appropriate choice of dielectric structure properties and driving electron beam parameters, the device operates in a single-mode regime, producing radiation in the THz range. We present measurements showing the emission of a narrowly-peaked spectrum from a fused silica tube 1 centimeter long with sub-millimeter transverse dimensions. We discuss the agreement of this data with theoretical and computational predictions, as well as possibilities for future study and application.
USTRAT/SUPA, Glasgow
Instituto Superior Tecnico, Lisbon
University of Oxford, Oxford
STFC/RAL, Chilton, Didcot, Oxon
University of Oxford, Clarendon Laboratory, Oxford
University of Glasgow, Glasgow
Funding: EPSRC and EU Euroleap
Advances in laser-plasma wake field accelerators (LWFA) have now reached the point where they can be considered as drivers of compact radiation sources covering an large spectral range. We present recent results from the Advanced Laser Plasma High-energy Accelerators towards X-rays (ALPHA-X) project. These include the first ultra-compact gamma ray source producing brilliant 10fs pulses of x-ray photons > 150keV. We present new opportunities for harnessing laser-driven plasma waves to accelerate electrons to high energies and use these as a basis for ultra-compact radiation sources with unprecedented peak brilliance and pulse duration. We have demonstrated a brilliant tabletop gamma ray source based on enhanced betatron emission in a plasma channel which produces > 109 photons per pulse in a bandwidth of 10-20%. We present results of a compact synchrotron source based on a LWFA and undulator and discuss the potential of developing an FEL based this technology. Finally we discuss the plans for the Scottish Centre for the Application of Plasma-based Accelerator (SCAPA), which is being set up to develop and apply compact radiation sources, laser-driven ion sources and LWFAs.
BNL, Upton, Long Island, New York
UCLA, Los Angeles, California
Trains of subpicosecond electron bunches are essential to reach high transformer ratio and high efficiency in compact, beam-driven, plasma-based accelerators. These trains with a correlated energy chirp can also be used in pump-probe experiments driven by FELs. We demonstrate experimentally for the first time that such trains with controllable bunch-to-bunch spacing, bunch length, and charge can be produced using a mask technique. With this simple mask technique, the stability of the bunch train in energy and time is guaranteed by the beam feedback system.
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.
Instituto Superior Tecnico, Lisbon
UCLA, Los Angeles, California
Funding: F.C.Gulbenkian, F.C.T. [SFRH/BD/35749/2007, PTDC/FIS/66823/2006 (Portugal)], and European Community - New and Emerging Science and Technology Activity, FP6 program (project EuroLeap, contract #028514)
We address full particle-in-cell simulations of the next generation of Laser Wakefield Accelerators with energy gains > 10 GeV. The distances involved in these numerical experiments are very demanding in terms of computational resources and are not yet possible to (easily) accomplish. Following the work on simulations of particle beam-plasma interaction scenarios in optimized Lorentz frames by J.-L. Vay*, the Lorentz transformation for a boosted frame was implemented in OSIRIS**, leading to a dramatic change in the computational resources required to model LWFA. The critical implementation details will be presented, and the main difficulties discussed. Quantitative comparisons between lab/boost frame results with OSIRIS, QuickPIC***, and experiment will be given. Finally, the results of a three-dimensional PIC simulation of a > 10 GeV accelerator stage will be presented, including a discussion on radiation emission.
* J.-L. Vay, PRL 98, 130405 (2007)
** R.A. Fonseca et al., LNCS 2329, III-342 (Springer-Verlag, 2002)
*** C. Huang, et al., JCP 217, Issue 2, 20 (2006)
LNLS, Campinas
We present an overview of a new synchrotron radiation source currently being designed at the Brazilian Synchrotron Light Laboratory (LNLS) in Campinas. The LNLS-1 light source, based on a 1.37 GeV storage ring, has been in routine operation since 1997. The LNLS-2 light source will consist of an injector system and a low emittance 2.5 GeV electron storage ring capable of delivering undulator radiation with average brightness in excess of 1020 photons/sec/0.1%/mm2/mrad2 in the few hundred eV to several tens of keV photon energy range. High flux radiation up to 100 keV will also be available with the use of superconduting wigglers. In this work, we present the basic design considerations and parameters for a proposed magnetic lattice for LNLS-2, with special attention to providing solutions for the realization of low emittance which are cost effective regarding both the construction investment as well as the operation of the facility. In particular, the possibility of the large scale use of permanent magnet technology for the storage ring lattice magnets is discussed.
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.
CERN, Geneva
Collimation and halo cleaning for the LHC beams are performed separately for betatron and momentum losses, requiring two dedicated insertions for collimation. Betatron cleaning is performed in IR7 while momentum cleaning is performed in IR3. A study has been performed to evaluate the performance reach for a combined betatron and momentum cleaning system in IR3. The results are presented.
ANL, Argonne
Transition radiation is frequently used to determine the time profile of a bunched relativistic particle beam. Emphasis is usually given to diagnostics sensitive to wavelengths in the infrared-to-optical portion of the spectrum. In this study, CST Particle Studio simulations are used to make quantitative statements regarding the low-frequency (DC to microwave) behavior of coherent transition radiation from a mirror inclined at 45 degrees relative to the particle beam trajectory. A moving Gaussian bunch confined within a cylindrical beam pipe is modeled. Simulation results are presented.
CLASSE, Ithaca, New York
Funding: NSF PHY-0131508
The forces from Coherent Synchrotron Radiation (CSR) on the particle bunch can be computed exactly for a line charge. Modeling a finite bunch by a line charge often produces a very good model of the CSR forces, and the full bunch can then be propagated under these forces. This 1-D model of CSR has often been used with a small angle approximation, an ultra relativistic approximation, and the approximation that radiation originating in one dipole can be neglected in the next dipole. Here we use Jefimenko's forms of Maxwell's equations, without such approximations, to calculate the wake-fields due to the longitudinal CSR force in multiple bends and drifts. Several interesting observations are presented, including multiple bend effects, shielding by conducting parallel plates, and bunch compression.
SLAC, Menlo Park, California
BINP SB RAS, Novosibirsk
Funding: Work supported by US DOE contracts DE-AC03-76SF00515
We study the impedance due to coherent synchrotron radiation (CSR) generated by a short bunch of charged particles passing through a bend magnet of finite length in a vacuum chamber of a given cross section. Our method represents a further development of the previous papers*. In this method we decompose the electromagnetic field of the beam into the eigenmodes of the toroidal chamber. We derive a system of equations for the expansion coefficients in the series, and develop a numerical algorithm for practical calculations. We illustrate our general method by calculating the CSR impedance of a beam moving in a vacuum chamber of rectangular cross section.
*G. V. Stupakov and I. A. Kotelnikov, PRST-AB 6, 034401 (2003); T. Agoh, K.Yokoya, PRST-AB, 7, 054403 (2004)
ANL, Argonne
Euclid TechLabs, LLC, Solon, Ohio
PSU, University Park, Pennsylvania
Saint-Petersburg State University, Saint-Petersburg
Funding: DOE
Metamaterials (MTMs) are periodic artificially constructed electromagnetic structures. The periodicity of the MTM is much smaller than the wavelength of the radiation being transported. With this condition satisfied, MTMs can be assigned an effective permittivity and permeability. Areas of possible application of MTMs in accelerator science are Cherenkov detectors and wakefield devices. MTMs can be designed to be anisotropic and dispersive. The combination of engineered anisotropy and dispersion can produce a Cherenkov radiation spectrum with a different dependence on particle energy than conventional materials. This can be a basis for novel non-invasive beam energy measurements. We report on progress in the development of these media for a proof-of-principle demonstration of a metamaterial-based beam diagnostic.
ANL, Argonne
Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract number DE-AC02-06CH11357.
An array of fused-silica, fiber optic bundles has been built to spatially monitor e-beam loss in the APS storage ring (SR). A prototype beam loss position monitor (BLPM) has been installed on unoccupied undulator straight sections. The BLPM allows for 6 fiber bundles, 3 above and 3 below the beam. The center bundles are aligned with the beam axis. Presently, 4 bundles are used, 3 above and one in the center position below the beam. Each bundle is 3 m in length and composed of 61 220-micron-diameter fibers for a total aperture of 2 mm. The first 30 cm of each bundle are aligned parallel to the beam in contact with the vacuum chamber. Light generated by fast electrons within the fibers is thought to come primarily from Cerenkov radiation. The rest of the fiber acts as a light pipe to transmit photons to shielded PMTs. Tests show good signal strength during stored-beam mode from Touschek scattering and deterministic losses that occur during top-up injection and beam dumps. Post-injection loss signals show spatial and temporal dynamics. Simulation work is expected to provide calibration for integrated losses that can be compared with progressive undulator demagnetization.
BNL, Upton, Long Island, New York
Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract DE-AC02-98CH10886.
With growth of circulating current in the storage rings the heating of the beam position monitor (BPM) buttons due to the induced trapped modes is drastically increasing. Excessive heating can lead to the errors in the measuring of beam position or even catastrophic failures of pick-up assembly. In this paper we present calculations of heat generated in the button for different geometries and materials. The obtained results are used for the optimization of the BPM design for the NSLS-II project.
BNL, Upton, Long Island, New York
Fermilab, Batavia
Funding: Work performed under the auspices of the US Department of Energy
SiO2 quartz fibers of the LHC ATLAS 0-degree calorimeter (ZDC) anticipated to experience integrated doses of a few Grad at their closest position were exposed to 200 MeV protons and neutrons at the BNL Linac. Specifically, 1mm- and 2mm- diameter quartz (GE 124) rods were exposed to direct 200 MeV protons during the first phase of exposure leading to peak integrated dose of ~28 Grad. Exposure to a primarily neutron flux of 1mm-diameter SiO2 fibers was also achieved with a special neutron source arrangement. In a post-irradiation analysis the quartz fiber transmittance was evaluated as a function of the absorbed dose. Dramatic degradation of the transmittance property was observed with increased radiation damage. In addition, detailed evaluation of the fibers under the microscope revealed interesting micro-structural damage features and irradiation-induced defects. This paper presents the results of the irradiation damage study.
BNL, Upton, Long Island, New York
The effects of high fluences of energetic charged particles on CdZnTe detectors have been studied and are reported in this paper. Specifically, 200 MeV protons of the Brookhaven National Laboratory LINAC were used to bombard a set of CdZnTe detector crystals to fluences as high as 2.6x1016 protons/cm2. Following exposure a set of past-irradiation analyses were conducted to quantify the effects. These include (a) gamma-ray spectra analysis using a high-purity germanium detector in an effort to assess both the peak position shifting as a function of fluence and the spectral content, (a) resistivity and leakage current measurements, and (c) manifestation of radiation damage in the crystal microstructure. In addition, and based on the irradiation parameters used, a numerical prediction model was formulated aiming to benchmark the observed isotopes.
Fermilab, Batavia
KAERI, Daejon
BINP SB RAS, Novosibirsk
Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-07CH11359.
Noninvasive bunch duration monitoring has a crucial importance for modern accelerators intended for short wavelength FEL’s, colliders and in some beam dynamics experiments. Monitoring of the bunch compression in the Emittance Exchange Experiment at the A0 Photoinjector was done using a parametric presentation of the bunch duration via Coherent Synchrotron Radiation (CSR) emitted in a dipole magnet and measured with a wide-band quasi-optical Schottky Barrier Detector (SBD). The monitoring resulted in a mapping of the quadrupole parameters allowing a determination of the region of highest compression of the bunch in the sub-picosecond range. The obtained data were compared with those measured using the streak camera. A description of the technique and the results of simulations and measurements are presented and discussed in this report.
Fermilab, Batavia
ANL, Argonne
Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
The challenge of mitigating the strong enhancements of the optical transition radiation (OTR) signal observed after bunch compression in the Advanced Photon Source (APS) linac chicane and at the Linac Coherent Light Source (LCLS) has recently been addressed. We have demonstrated a technique to mitigate the intensity of the coherent OTR (COTR) relative to the OTR signals on the APS beams at 325 MeV. Since the previously reported spectral content of the COTR at LCLS after the first compression stage is similar, the concepts should also apply to LCLS. We utilized the stronger violet content at 400 nm of the OTR compared to the observed gain factors of the COTR in the blue to NIR regime. We also demonstrated the use of an LSO:Ce scintillator that emits violet light to support lower-charge imaging. Spectral-dependence measurements of the COTR were done initially at the 325-MeV station using a series of band pass filters inserted before the CCD camera, but recent tests with an Oriel spectrometer with ICCD readout have extended those studies and confirmed the concepts. These techniques are complementary to the proposed use of a laser heater to mitigate the microbunching itself at LCLS.
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.
INFN/LNF, Frascati (Roma)
USTC/NSRL, Hefei, Anhui
VIGO System S.A., Ozarow Maz.
Real time diagnostics is a fundamental tool for accelerator physics, particularly important to improve performances of existing synchrotron radiation sources, colliders and a key issue for 4th generation sources and FELs. We report the first measurements in the time and frequency domain performed at Hefei Light Source (HLS), the SR facility of the National Synchrotron Radiation Laboratory (NSRL), of the longitudinal bunch lengths. A fast uncooled HgCdTe photodiode optimized in the mid-IR range has been used to record at the IR port the length of the e- bunches. IR devices are compact and low cost detectors suitable for a bunch-by-bunch longitudinal diagnostics. The data are useful to investigate longitudinal oscillations and characterize the bunch length. The IR signal has been used to measure the synchrotron oscillation frequency, its harmonics in the multi-bunch mode and the bunch lengths in multi-bunch mode at different beam currents. For the first time, simultaneously, data have been collected at visible wavelengths using a fast photodiode at the diagnostics beamline of HLS. A comparison between IR data and diagnostics realized in the visible will be presented and discussed.
INFN/LNF, Frascati (Roma)
Università degli Studi di Firenze, Firenze
INOA, Firenze
VIGO System S.A., Ozarow Maz.
At the LNF (Laboratori Nazionali di Frascati) of the INFN a novel diagnostics experiment has been set-up to monitor the real time bunch behavior in the positron ring of the DAΦNE collider. The experiment has been installed on a bending magnet exit port of the e+ ring. The front-end consists of a UHV chamber where a gold-coated plane mirror deflects the radiation through a ZnSe window. After the window, a compact optical layout in air focuses the radiation on an IR detector. Compact mid-IR fast uncooled HgCdTe photodiodes are used to measure the bunch by bunch emission. A preliminary alignment of the mirrors and a first characterization of the radiation emitted have been performed. Longitudinal measurements of the bunch behavior, both in time and in frequency domain, obtained with fast IR detectors are presented. This novel diagnostics now available is ready to allow monitoring in real time of the bunch-by-bunch positron emission. It has been designed to improve the DAΦNE diagnostics with the main aim to identify and characterize positron bunch instabilities in the longitudinal plane. Developments for extending detection capability in the transverse planes are in progress.
JAI, Egham, Surrey
CERN, Geneva
The diagnostics of a 6D phase space distribution is a crucial and a challenging task, which is required for modern and future installations such as light sources or linear colliders, like CLIC. The longitudinal profile is one of the parameters which needs to be monitored. A setup for the investigation of coherent diffraction radiation from a conducting screen as a tool for non-invasive longitudinal electron beam profile diagnostics has been designed and installed in the CRM line of the CLIC Test Facility (CTF3) at CERN. This setup also allows the measurements of Coherent Synchrotron Radiation from the last bending magnet. In this report we present the status of the experiment and show some preliminary results on coherent synchrotron radiation and coherent diffraction radiation studies. The plans for interferometric measurements of coherent radiation are also presented.
LBNL, Berkeley, California
Y.Y. Labs, Inc., Fremont, California
Funding: Work supported by the U.S. Department of Energy under Contract No.
By coupling the emitted synchrotron light into an optical fiber, it is possible to transmit the signal at substantial distances from the light port, without the need to use expensive beamlines. This would be especially beneficial in all those cases when the synchrotron is situated in areas not easily access because of their location, or due to high radiation levels. Furthermore, the fiber output can be easily switched, or even shared, between different diagnostic instruments. We present the latest results on the coupling and dispersion measurements performed at the Advanced Light Source in Berkeley.
Muons, Inc, Batavia
Enrico Fermi Institute, University of Chicago, Chicago, Illinois
Many measurements in particle and accelerator physics are limited by the time resolution with which individual particles can be detected. This includes particle identification via time-of-flight in major experiments like CDF at Fermilab and Atlas and CMS at the LHC, as well as the measurement of longitudinal variables in accelerator physics experiments. Large-scale systems, such as neutrino detectors, could be significantly improved by inexpensive, large-area photo detectors with resolutions of a few millimeters in space and a few picoseconds in time. Recent innovations make inexpensive, large-area detectors possible, with only minor compromises in spatial and time resolution. The G4beamline program [1] is one of the appropriate tools for simulation of low-energy physics processes. The set of specialized tools - MCPS [2], POISSON-2 [3] and Monte Carlo Simulator was used for numerical study of different photo multipliers.
ANL, Argonne
Funding: This work is supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
A Cf-252 fission source yields neutron-rich fission fragments. The CAlifornium Rare Ion Breeder Upgrade (CARIBU) project is an upgrade to the Argonne Tandem Linear Accelerator System (ATLAS) that provides a 37 GBq (1 Ci) source of these radioactive ions for acceleration. Fission fragments stop in a gas catcher, are extracted into an ECR ion source to increase the charge state, and then accelerated in ATLAS. The radiation fields produced by an unshielded 1 Ci 252Cf source are 46 rem/hr (neutron) and 4 R/hr (gamma) at 30 cm. A shielding system has been constructed that reduces the radiation fields to ≤ 1 mrem/hr at 30 cm from all accessible surfaces. The MCNPX code was used to model the transport of the spontaneous fission neutrons and gamma radiation, and the gamma radiation induced in the shielding materials by the neutrons. The primary neutron shielding material chosen was 5% borated polyethylene, enclosed in steel. Calculations are made for emissions of radioactive effluents, primarily noble gases, using the EPA CAP-88 computer program. The maximum credible incident scenario releases a small quantity of Cf-252. Calculated dose results and mitigation methods are presented.
BNL, Upton, Long Island, New York
Funding: Work supported by U.S. DOE, Contract No.DE-AC02-98CH10886
Beam loss monitors have been used for more than a decade in the VUV ring at the NSLS. These have proved useful for optimizing injection and operation of the ring. Recently similar monitors have been installed in the Xray ring and are being used to better understand injection as well as operation of the ring. These units have been compared with the Bergoz Beam Loss Monitors, which have been mostly useful for operating beam losses. The experience with these units have led to an improved detector that is being considered by NSLS-II as a beam containment verification monitor, as well as diagnostic for optimization of injection efficiency.
JAEA/J-PARC, Tokai-mura
KEK, Ibaraki
JAEA/LINAC, Ibaraki-ken
JAEA, Ibaraki-ken
Over hundred beam loss monitors (BLM) in the J-PARC LINAC have been used to measure the beam loss observed during the accelerator operation. Dose rates distributed in LINAC area were compared with beam loss records taken by the BLMs. This paper describes the results of the operational data and their comparisons with the dose rates of LINAC area.
CERN, Geneva
The maximum intensity the CERN PS has to deliver is continuously increasing. In particular, during the next years, one of the most intense beam ever produced in the PS, with up to 3000·1010 proton per pulse, should be delivered on a regular basis for the CNGS physics program. It is now known that the existing radiation shielding of the PS in some places is too weak and constitutes a major limitation due to large beam losses in specific locations of the machine. This is the case for the injection region: losses appear on the injection septum when the beam is injected in the ring and during the first turn, due also to an optical mismatch between the injection line and the PS. This paper presents the experimental studies and the simulations which have been made to understand the loss pattern in the injection region. Possible solutions to reduce the beam losses will be described, including the computation of a new injection optics.
CERN, Geneva
The LHC phase II collimation project requires beam shock and impact tests of materials used for beam intercepting devices. Similar tests are also of great interest for other accelerator components such as beam entrance/exit windows and protection devices. For this purpose a dedicated High Radiation Material test facility (HiRadMat) is under study. This facility may be installed at CERN at the location of a former beam line. This paper describes the associated beam line which is foreseen to deliver a 450 GeV proton beam from SPS with an intensity of up to 3·1013 protons per shot. Different beam line designs will be compared and the choice of the beam steering and diagnostic elements will be discussed, as well as operational issues.
CERN, Geneva
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
The emission of Synchrotron Radiation in the CLIC BDS is one of the major limitations of the machine performance. An extensive revision of this phenomenon is presented with special emphasis on the IP solenoid.
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
The status of longitudinal and transverse Schottky observation systems for the synchrotron light source ANKA is presented. ANKA regularly operates in a dedicated low alpha mode with short bunches for the generation of coherent THz radiation. The Schottky measurement results are shown and compared with theoretical predictions for the regular as well as the different stages of the low alpha mode of operation. Special care had to be taken to control and mitigate the impact from strong coherent lines of the short bunches on the signal processing chain. The system setup is shown, expected and unexpected observations as well as applications are discussed.
The University of Liverpool, Liverpool
Cockcroft Institute, Warrington, Cheshire
Analytic descriptions of arbitrary magnetic fields can be calculated from the generalised gradients* of the on-axis field. Using magnetic field data, measured or computed on the surface of a cylinder, the generalised gradients can be calculated by solving Laplace's equation to find the three-dimensional multipole expansion of the field within the cylinder. After a suitable transformation, this description can be combined with a symplectic integrator allowing the transfer map to be calculated. A new tracking code is under development in C++, which makes use of a differential algebra class to calculate the transfer map. The code has been heavily optimised to give a fast, accurate calculation of the transfer map for an arbitrary field. The multipole nature of the field description gives additional insights into fringe-field and pseudo-multipole effects and allows a deeper understanding of the beam dynamics.
*Venturini M. and Dragt A., NIM Phys. Res. Sect. A, 427, 387 (1999)
ORNL, Oak Ridge, Tennessee
BINP SB RAS, Novosibirsk
Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
Conversion of BLM readings into number of lost particles is a challenging task. Any insertion device is a good mean to obtain a localized loss and obtain such conversion factor with direct measurement. Such a measurement serves as a good benchmark for Monte-Carlo simulation of radiation transport. We used wire scanners and scraper induced losses to perform analysis of BLM response to local loss. The paper also provides a technique to measure 0.1% of full beam charge being intercepted by scraper during 650kW production run extracting the useful signal from high noise (20 times higher than signal) environment
PKU/IHIP, Beijing
JLAB, Newport News, Virginia
Fermilab, Batavia
Funding: DOE Contract DE-AC05-060R23177 China Scholarship Council
Beam size measurement with near-field optical diffraction radiation (ODR) has been carried out successfully at CEBAF. The ODR station is installed on the Hall-A beam line after eight bending magnets. The ODR images were affected by an unexpected radiation. Some calculations for analyzing the source of the radiation will be presented. Furthermore, two schemes will be proposed to alleviate the contamination.
PAL, Pohang, Kyungbuk
A photon-beam-position-monitor (PBPM) is installed in a diagnostic beamline of the Pohang Light Source (PLS). From experience of existing PBPMs, we enriched our understanding of the synchrotron radiation and this understanding is fully considered for physical design of the new PBPM. The newly built PBPM is tested by using a high-power ultraviolet laser and its performance is checked before installation. Measurement results of beam position shows that the current (thermal) effect is reduced significantly and they also shows good agreement with results from a beam position monitor inside the PLS storage ring.
RadiaBeam, Marina del Rey
Spectrum Detector, Lake Oswego, Oregon
UGA, Athens, Georgia
UCLA, Los Angeles, California
Funding: Work supported by U.S. DOE Grant Number DE-FG02-07ER84814.
The generation of high peak current, high brightness beams routinely requires compression methods (e.g. four-bend chicane), which produce coherent radiation as a by-product. The sensing of this radiation, coupled with interferometric methods, yields crucial longitudinal bunch length and bunch profile information. This paper discusses the progress of the development of a real-time terahertz interferometer used for longitudinal beam profile diagnosis.
RadiaBeam, Marina del Rey
UCLA, Los Angeles, California
A Coherent Optical Transition Radiation (COTR) arising from the photo-injector electron beams spontaneous microbunching at optical frequencies has been recently observed in a number of experiments. This effect can lead to an undesirable optical background for OTR beam profile measurements at these facilities. A method to resolve this problem is proposed, based on selectively suppressing the back-scattered COTR using multiple scattering in the insertion foil. An analytical treatment of COTR dependence on the angular divergence in the radiating beam is presented, and the efficacy of the approach is illustrated with the numerical examples.
SLAC, Menlo Park, California
KEK, Ibaraki
Life Imaging Technology, Palo Alto, California
Funding: Work sponsored by U.S. Department of Energy Contract DE-AC03-76SF00515 and Office of Basic Energy Sciences, Division of Chemical Sciences.
A two-slit interferometer has been installed in the SPEAR3 diagnostic beam line to measure vertical beam size at a dipole source point. The diagnostic beam line accepts unfocused, visible light in a 3.5 x 6.0 mrad aperture so that at the slit location 17 m from the source, the vertical extent of the beam is 100mm. For typical source sizes of sigy~15 um (0.1% emittance coupling) a slit separation of 80 mm produces fringe visibility of order V=0.5. Hence a significant plot of fringe visibility vs. slit separation can be generated to infer source size via Fourier transformation. In this paper we report on the interferometer construction, beam size measurement and potential deficiencies of the system, and compare with theoretical results.
Saint-Petersburg State University, Saint-Petersburg
Funding: Physical Faculty of St.Petersburg State University (14.10.08); SBIR DOE (DE-FG02-08ER85031)
Radiation of a charge crossing the boundary between vacuum and left-handed medium is analyzed. The medium is characterized by permittivity and permeability with frequency dispersion of “plasmatic” type. Such properties can be realized in some modern metamaterials with a relatively simple structure. Both the case of unbounded medium and the case of circular waveguide are considered. Analytical expressions for field components are obtained and algorithm of their computation is developed. The main attention is given to the analysis of radiation in vacuum region. In particular, it is shown that two types of radiation can be generated in this region. One of them is an ordinary transition radiation having relatively large magnitude. Another type of radiation can be named the “Cherenkov-transition” radiation. Conditions of generating this type of radiation are obtained. This effect and some another properties of radiation can be used for diagnostics of beams. For example, the detector with two energy thresholds can be designed.
Saint-Petersburg State University, Saint-Petersburg
ANL, Argonne
Euclid TechLabs, LLC, Solon, Ohio
Funding: SBIR DOE (DE-FG02-08ER85031); Russian Foundation for Basic Research (06-02-16442-a); Physical Faculty of St.Petersburg State University (Russia) (14.10.08)
We consider microwave Cherenkov radiation in a waveguide containing an engineered medium, and show that the properties of the radiation can be used to determine the energy of charged particle beams. These properties can form the basis of a new technique for bunch diagnostics in accelerators. We propose to use a material characterized by a diagonal permittivity tensor with components depending on frequency as in the case of a plasma but with the constant terms not equal to unity. These properties can be realized in a metamaterial with a relatively simple structure. In contrast to previous work in the present paper a vacuum channel in the waveguide is taken into account. The particle energy can be determined by measurement of mode frequencies. It is shown that a strong dependence of mode frequencies on particle energy for some predetermined narrow range can be obtained by appropriate choice of the metamaterial parameters and radius of the channel. It is also possible to obtain energy measurements over a wider range at the cost of a weaker frequency dependence.
*A.V.Tyukhtin, S.P.Antipov, A.Kanareykin, P.Schoessow, PAC07, p.4156.
**A.V.Tyukhtin, EPAC08, p.1302.
***A.V.Tyukhtin, Technical Physics Letters, v.34, p.884 (2008); v.35 (2009), in press.
USP/LAL, Sao Paulo
Funding: FAPESP, CNPq
In this work we describe the design of the OTR monitors that will be used to measure beam parameters of the IFUSP Microtron electron beam. The OTR monitor design must allow for efficiency in the entire energy range (from 5 MeV up to 38 MeV in steps of 0.9 MeV), and the devices are planed to monitor charge distribution, beam energy and divergence. An exception is made for the OTR monitor to the 1.7 MeV beam line, which is to be used to monitor only the beam charge distribution at the exit of the linac injector. The image acquisition system is also presented.
USP/LAL, Sao Paulo
Funding: FAPESP, CNPq
In this work we describe a model to study the effect of charge saturation in phosphor screens in the determination of electron beam profiles. It is shown that the charge saturation introduces systematic errors in the beam diameter determination, since it tends to increase the observed beam diameter. The study is made supposing a Gaussian beam profile and a saturation model to the charge response of the phosphor material. The induced errors increase for higher currents and/or narrow beams. A possible correction algorithm that can be applied to some measurements is presented, together with a brief discussion about the consequences of these systematic errors in emittance measurements.
The University of Liverpool, Liverpool
Cockcroft Institute, Warrington, Cheshire
Funding: Supported by the EU under contract PITN-GA-2008-215080
Beam diagnostics is a rich field in which a great variety of physical effects are made use of and consequently provides a wide and solid base for the training of young researchers. Moreover, the principles that are used in any beam monitor or detector enter readily into industrial applications or the medical sector which guarantees that training of young researchers in this field is of relevance far beyond the pure field of particle accelerators. DITANET- "DIagnostic Techniques for particle Accelerators a European NETwork" - covers the development of advanced beam diagnostic methods for a wide range of existing or future accelerators, both for electrons and ions. DITANET is the largest ever coordinated EU education action for PhD students in the field of beam diagnostic techniques for future particle accelerators with a total budget of 4.2 M. This contribution gives an overview of the network’s activities and outlines selected research results from the consortium.
JLAB, Newport News, Virginia
Receivers designed for diagnostic applications range from those having moderate sensitivity to those possessing large dynamic range. Digital receivers have a dynamic range which are a function of the number of bits represented by the ADC and subsequent processing. If some of this range is sacrificed for extreme sensitivity, noise power can then be used to perform two-point load calibrations. Since load temperatures can be precisely determined, the receiver can be quickly and accurately characterized; minute changes in system gain can then be detected, and systematic errors corrected. In addition, using receiver pairs in a balanced approach to measuring X+, X-, Y+, Y-, eliminates systematic offset errors from non-identical system gains, and changes in system performance. This paper describes and demonstrates a balanced BPM-style diagnostic receiver, employing Dicke-switching to establish and maintain real-time system calibration. Benefits of such a receiver include wide bandwidth, solid absolute accuracy, improved position accuracy, and phase-sensitive measurements. System description, static and dynamic modeling, and measurement data are presented.
UCLA, Los Angeles, California
RadiaBeam, Marina del Rey
BNL, Upton, Long Island, New York
Funding: NSF grant # IIP-0724505
We describe our effort in the development of a low cost, wide-band detector/camera for generation of spatially resolved images of radiation beams in a multi-spectral range of wavelengths, from IR (infrared) to THz (terahertz). The detector (T-camera) utilizes a TLC (thermochromic liquid crystal) film as the sensitive element in a temperature controlled chamber and a CCD detector array and can be used as a powerful diagnostic for terahertz sources such as a synchrotron or an FEL
UMD, College Park, Maryland
ANL, Argonne
Funding: This work is funded by the US Dept. of Energy Offices of High Energy Physics and High Energy Density Physics, and by the US Dept. of Defense Office of Naval Research and Joint Technology Office.
Single foil OTR and two foil OTR interferometry have been successfully used to measure the size and divergence of electron beams with a wide range of energies. To measure rms emittance, two cameras are employed: one focused on the foil to obtain the spatial distribution of the beam, the other focused to infinity to obtain the angular distribution. The beam is first magnetically focused to a minimum size in directions which are orthogonal to the propagation axis, using a pair of quadrupoles. Then simultaneous measurements of the rms size (x,y) and divergence (x’,y’) of the beam are made. However, in the process of a quadrupole scan, the beam can go through a spot size minimum, a divergence minimum and a waist, i.e. the position where the cross-correlation term is zero. In general, the beam size, divergence and focusing strength for each of these conditions are different. We present new algorithms that relate the beam and magnetic parameters to the rms emittance for each of these three cases. We also compare the emittances, obtained using our algorithms and measurements made at the ANL AWA facility, with those produced by computer simulation.
USTC/NSRL, Hefei, Anhui
The stability of synchrotron radiation source is of great significance for users, and an accurate and reliable photon beam position monitor (PBPM) is essential for success of synchrotron radiation experiments. Recently, we development a new PBPM called staggered pair photon beam position monitor for photon beam position measurement in Hefei Light Source (HLS). Its main advantage is to reduce the influence of bunch size. Usually, difference over sum (Δ/Σ) method is used to process the photon beam signal. Two new methods are put forward, which are a ratio method and a log-ratio method. For photon beam with Gaussian distribution, differences among methods of Δ/Σ, ratio and log-ratio are introduced. Some calculating results are given for three signal processing methods. Comparing those three methods of position signal processing, log-ratio method is found to have the widest range of linearity, and can obtain identical beam position with different bunch size. Based on that, we also compare staggered pair monitor with double-blade monitor. The staggered pair monitor is found to have higher sensitivity, as well it can ignore the influence of bunch size.
UW-Madison/SRC, Madison, Wisconsin
The betatron tunes of an electron storage ring may be measured by driving transverse oscillations with an excitation electrode and measuring the resonant beam response with a pickup electrode. We model the damping of coherent betatron oscillations from the tune spread and radiation damping, finding that the tune signal is proportional to the square root of the product of the betatron functions at the excitation and pickup locations. The signal is independent of the betatron phase advance between the two locations. Our results are applied to the Aladdin 800-MeV electron storage ring.
JLAB, Newport News, Virginia
Funding: This work is supported under U.S. DOE Contract No. DE-AC05-06OR23177.
When an electron bunch with initial linear energy chirp traversing a bunch compression chicane, the bunch interacts with itself via coherent synchrotron radiation (CSR) and space charge force. The effective longitudinal CSR force for a 2D energy-chirped gaussian bunch on a circular orbit has been analyzed earlier*. In this paper, we present our analytical results of the effective longitudinal CSR force for such a bunch going through a general orbit, which includes the entrance and exit of a circular orbit.
*R. Li, Phys. Rev. ST Accel. Beams 11, 024401 (2008).
RadiaBeam, Marina del Rey
UCLA, Los Angeles, California
The accelerator community has many codes that model beams and emitted radiation. Many of these codes are specialized and often, as in start-to-end simulations, multiple codes are employed in subsequent fashion. One of the most important goals of simulations is to accurately model beam parameters and compare results to those obtained from real laboratory diagnostics. This paper describes the development of a user-friendly code that models the coherent radiation of high brightness beams, with a heavy emphasis on simulation of observables via laboratory diagnostics.
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)
UCLA, Los Angeles, California
PSI, Villigen
QUINDI has been developed to address the numerical challenge of calculating the radiation spectra from electron bunches in bending magnet systems. Since the introduction of QUINDI, many improvements and features have been added. QUINDI now supports a 3D model for bending magnets which includes fringing fields. A more modular approach has been achieved which allows better interoperability with other tracking and radiation codes. There have been many updates to the electric field calculation and spectrum processing, as well as to the post-processor, SpecGUI.
RadiaBeam, Marina del Rey
UCLA, Los Angeles, California
Manhattanville College, Purchase, NY
Funding: This project is supported by DOE SBIR Grant DE-FG02-08ER85038.
Laser-powered dielectric accelerating structures, which have attracted attention in recent years, trade fabrication challenges and extremely small beam apertures for the promise of high gradients and new bunch formats. The slab-symmetric, periodically-coupledμAccelerator Platform (MAP) is one such dielectric accelerator, and has been under development through a RadiaBeam-UCLA collaboration for several years. Intended applications of the structure include the production of radiation for medical treatments, imaging, and industrial uses. Prototype MAP structures are now being fabricated, and a program has been undertaken to test this device using externally injected electron beams. Plans are underway to install structures in the E163 facility at SLAC. In this paper we describe the testing methods, diagnostics and expectations. Progress and results to date are also presented.
UCLA, Los Angeles, California
BNL, Upton, Long Island, New York
Funding: Work supported by US Department of Energy.
At the BNL-ATF we have recently demonstrated the generation of trains of electron with sub-picosecond spacing*. These trains of equidistant bunches can be used to resonantly excite large amplitude wakefields in plasmas. The resonance is reached when the plasma wavelength is equal to the drive bunch train spacing. However, in order accelerate an electron bunch with a narrow energy spread, a trailing witness bunch must be generated. The witness bunch must be separated from the last drive bunch by one and a half time the distance between drive bunches. We show that such a drive/witness bunch train can be generated. The mask can also be designed to produce witness bunches trailing the drive bunch train by 2.5,3. 5, times the drive bunch spacing in order to probe the coherence of the plasma wake in subsequent wave bucket. Resonantly driving plasma wakes with trains of bunches could lead to multiplication of the trailing bunch energy by up to the number of bunches in the drive train with high efficiency in a single stage. Experimental results will be presented.
* P. Muggli et al., Phys. Rev. Lett. {10}1, 054801, 2008
BNL, Upton, Long Island, New York
The short- and long-range wakepotentials have been studied for the design of the infrared (IR) extraction chamber with large full aperture: 67mm vertical and 134mm horizontal. The IR-chamber will be installed within a 2.6m long wide-gap bending magnet with 25m bend radius. Due to the large bend radius it is difficult to separate the light from the electron trajectory. The required parameters of the collected IR radiation in location of the extraction mirror are ~50mrad horizontal and ~25mrad vertical (full radiation opening angles). If the extraction mirror is seen by the beam, resonant modes are generated in the chamber. In this paper, we present the detailed calculated impedance for the design of the far-IR chamber, and show that placing the extraction mirror in the proper position eliminates the resonances. In this case, the impedance reduces to that of a simple tapered structure, which is acceptable in regard to its impact on the electron beam.
BNL, Upton, Long Island, New York
Single large angle Coulomb scattering is referred to as Touschek scattering. In addition to causing particle loss when the scattered particles are outside the momentum aperture, the process also results in a non-Gaussian tail, which is an equilibrium between the Touschek scattering and radiation damping. Here we present an analytical calculation for this equilibrium distribution.
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.
HZB, Berlin
Bursts of coherent synchrotron radiation (CSR) in the far IR and down to the μ-wave region have been observed in many synchrotron light sources. At BESSY II the temporal structure of these pulses in the THz-region was observed as a function of the bunch length which was varied by changing the momentum compaction factor and as a function of the number of electrons in the single bunch. It was found, that for a bunch length between 3 and 15 ps the first signs of time dependent CSR occur at a frequency which is a multiple of the zero current synchrotron frequency. This frequency increases with the bunch length and indicates that higher azimuthal modes become unstable first. Slower bursts, with repetition rates on the time scale of mill seconds and much slower than the synchrotron period, show up slightly above this threshold. These bursts possess the much faster initial temporal structure and are probably the result of longitudinal mode mixing. The experimental observations are presented and compared to calculations.
JAI, Oxford
Diamond, Oxfordshire
Diamond is a third generation synchrotron light source built to generate infra-red, ultraviolet and X-ray synchrotron radiation (SR) of exceptional brightness. The operation of the Diamond storage ring with short electron bunches for generation of Coherent THz radiation and short X-ray pulses for time-resolved experiments is limited by the onset of microbunch instabilities. We have started a project to investigate the longitudinal electron beam dynamics and microbunch instabilities in the Diamond storage ring. In the first experiment we used an ultra-fast (time response is about 250 ps) Schottky Barrier Diode sensitive to the radiation within the 3.33-5 mm wavelength range. When the single bunch current exceeded 1.9 mA we observed a set of sub-THz bursts appearing quasi-periodically while the beam was circulating in the ring. The fast response allowed us to detect the signal turn-by-turn, which gives us an opportunity to study the bursts’ structure and evolution. It also allows us to study the effect in a multi-bunch mode when bunches are only 2 ns apart. In this report we will present our first preliminary results and also discuss future plans.
KIT, Karlsruhe
FZK, Karlsruhe
Funding: This work has been supported by the Initiative and Networking Fund of the Helmholtz Association under contract number VH-NG-320.
In synchrotron light sources, coherent synchrotron radiation (CSR) is emitted at wavelengths comparable to and longer than the bunch length. One effect of the CSR wake field is the distortion of the bunch distribution, which increases with higher currents. In the theoretical calculations, a threshold exists beyond which the solutions begin to diverge. On the other hand, the CSR wake can also excite a micorbunching instability which prevents stable emission of CSR for high currents and leads to highly intense bursts of radiation. In this paper the development of the calculated bunch shapes and the corresponding moments of the current distribution for varying bunch currents are studied. It can be shown that the numerical threshold beyond which the solutions diverge, does not coincide with the observed bursting-stable-threshold at the ANKA storage ring, which agrees well with theory.
USC, Los Angeles, California
UCLA, Los Angeles, California
Duke University, Durham, North Carolina
BNL, Upton, Long Island, New York
Funding: Work supported by US Department of Energy.
Current Filamentation Instability, CFI, (or Weibel instability) is of central importance for relativistic beams in plasmas for the laboratory, ex. fast-igniter concept for inertial confinement fusion, and astrophysics, ex. cosmic jets. Simulations, with the particle-in-cell code QuickPic, with a beam produced by an RF accelerator show the appearance and effects of CFI. The instability is investigated as a function of electron beam parameters (including charge, transverse size and length) and plasma parameters (density and length) by evaluating the filament currents and magnetic fields. We present simulation results, discuss further simulation refinements, suggest criteria and threshold parameters for observing the presence of CFI and outline a potential future experiment.
ORNL, Oak Ridge, Tennessee
RAS/INR, Moscow
Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
SNS is a high intensity hadron beam facility; so the Beam Loss Monitor (BLM) system is a crucial part of Machine Protection System and an important tool for beam tuning. The paper presents the current status of installed detectors and experimental data obtained during SNS operations. We compare several different types of BLMs and show advantages and disadvantages of each type. The electronic parts obsolescence became a real issue since the original electronics was designed about 10 years ago. The first test of our next generation BLM system is expected to be done by summer 2009. The new system will contribute to significant noise reduction and will follow a modular concept of Smart Device to achieve a higher degree of reliability and maintainability.
BNL, Upton, Long Island, New York
In this paper we report the current status of the studies of a phenomenon of microbunching at NSLS Source Development Laboratory (SDL). We observed the microbunching inside 70MeV electron bunches even for subpicosecond beams of 10pC charge. Additional microbunching is formed when the beam is compressed in the bunch compressor utilizing the 4-magnet chicane. We study the mechanisms of microbunching in an electron beam generated by a 100fs laser pulse. It allows reducing the possibility of having beam structures induced by photo-injector laser, eliminating effects of RF curvature, and enhancing the longitudinal space charge (LSC) and the coherent synchrotron radiation (CSR) effects.
CIAE, Beijing
TRIUMF, Vancouver
Department of Physics, Central China Normal University, Wuhan
There is increasing interest in high current compact H- cyclotrons for RIB, isotope production or as injectors for sub-critical reactor testing facilities. For compact cyclotrons, a practical limit on the output energy, to prevent significant Lorentz stripping and resulting activation, is ~100 MeV. Vacuum dissociation is another critical problem, because a compact structure and small parts inside the tank make high vacuum challenging. This paper describes how Lorentz stripping and vacuum dissociation were calculated for our “CYCIAE-100” under construction. In order to take into account non uniform magnetic fields and vacuum, losses were calculated by numerically integrating loss equations along tracked orbits, as these were being calculated by the beam dynamics code. To verify the code, losses derived with field and vacuum data from the TRIUMF 500 MeV cyclotron were compared with measurements. For the CYCIAE-100 cyclotron we predict that electromagnetic losses will account for less then 0.3% of total beam, vacuum losses for less than 0.58%, with peak magnetic fields up to 1.35T and average vacuum up to 5·10-8 Torr.
TU Darmstadt, Darmstadt
CERN, Geneva
The REX-ISOLDE radioactive ion beam facility at CERN makes great demands also on the experimentalists due to its specific duty cycle and the time structure with short beam pulses and large intensities. This paper describes the experimentalist's point of view, how to obtain sufficient and correct statistics under the special circumstances arising from the beam time structure. In particular, the case of Coulomb excitation experiments, where a large total cross section is ultimately desired, is studied in greater detail.