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| RPAE001 | On the Issue of Phasing of Undulators at the Advanced Photon Source | 764 |
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Funding: Work supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38. Placing two collinear undulators in the 5.6-m-long straight sections at the Advanced Photon Source (APS) can answer the demand for increased brilliance. Whether longitudinal phasing needs to be taken into account for optimum spectral performance has been investigated. A comprehensive computer simulation study was completed to study the effect of the electron beam emittance, the magnetic field quality of the undulators, and the magnetic field strength (K value) on the spectral performance. For a zero-emittance beam, the radiation spectra exhibit strong interference that depends sensitively on the phase between the undulators. For a realistic APS-emittance beam and beam energy spread, the strong and phase-sensitive interference is substantially smoothed. A summary of the key findings including intensity losses due to unphased undulators is reported in this paper. |
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| RPAE002 | Coupling Correction of a Circularly Polarizing Undulator at the Advanced Photon Source | 805 |
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Funding: This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38. The electromagnetic Circularly Polarizing Undulator (CPU) installed at the Advanced Photon Source (APS) storage ring produces skew quadrupole field errors, which were initially corrected by a small skew quadrupole magnet at one end of the device. Because the storage ring is operated at 1% coupling or less, a correction not located at the source inside the CPU is insufficient, as we have confirmed in simulation. Adding a skew coil at the other end of the CPU allows us to make a complete correction of the coupling source in the undulator. Correction setpoints are determined by APS's general optimizing software with the vertical beam size of a x-ray pinhole image as a readback. |
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| RPAE003 | Optimization and Modeling Studies for Obtaining High Injection Efficiency at the Advanced Photon Source | 871 |
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Funding: This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38. In recent years, the optics of the Advanced Photon Source storage ring has changed to lower equilibrium emittance (2.5 nm-rad) but at the cost of stronger sextupoles and stronger nonlinearities, which have reduced the injection efficiency from 100% in the high emittance mode. Over the years we have developed a series of optimization, measurement and modeling studies of the injection process, which allows us to obtain or maintain low injection losses. For example, the trajectory in the storage ring is optimized with trajectory knobs for maximum injection efficiency. This can be followed by collecting first-turn trajectory data, from which we can fit the initial phase-space coordinates. The model of the "optimized" trajectory would show whether the beam comes too close to a physical aperture in the injection magnets. Another modeling step is the fit and correction of the transfer line optics, which has a significant impact on phase-space matching. |
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| RPAE004 | Parametric Mechanical Design of New Insertion Devices at the APS | 889 |
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Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences under Contract No. W-31-109-ENG-38. Three permanent-magnet, planar, hybrid ID designs have recently been completed at the APS. The periods of the devices are 2.7 cm, 3.0 cm and 3.5 cm with nominal lengths of 2.4 m. Several design studies were performed for the initial 2.7 cm period device to investigate the utility of various design features. Then a parametric solid model for the initial device was developed and value engineered to minimize manufacturing, assembly and tuning costs. The model allowed the very rapid design of subsequent devices of similar periods and allowed commonality of several components of the IDs. This design family incorporates a low-cost method of pole retention and registration. Poles are secured by screws in two holes tapped into each pole. Pole location is registered by means of two small dowel pins for each pole in mating holes reamed into each pole and a base plate common to the poles and magnets. This base plate is flexible in bending along its length so shimming behind it can be used to accurately change the height of a pair of poles for tuning. Another feature of the design is modular construction to allow each device to be used full-length or shortened to a nominal 2.1 m length for use in APS "canted undulator" sectors. |
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| RPAE005 | The possibility for a Short-Period Hybrid Staggered Undulator | 982 |
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Funding: Work supported by the U.S. Dept. of Energy under Contract No. W-31-109-ENG-38. Much work is underway to develop superconducting undulators in order to generate brilliant hard x-ray radiation at many synchrotron radiation facilities. However, in spite of many R&D efforts, it might take several years to reach this goal. On the other hand, the possibilities of cryogenic permanent magnet undulators are being investigated in order to provide an interim solution for hard x-ray users’ needs at Spring-8 and other facilities. However, although the in-vacuum undulator technology is well established, the in-vacuum gap-motion mechanism at a low temperature might cause major concerns regarding reliability and cost effectiveness. In this paper, the possibility for a cryogenic short-period staggered undulator was investigated. A simple model calculation by RADIA* shows that the effective undulator field is 0.825 T for a 15-mm-period staggered undulator at 6 mm gap with 1.36 T solenoid field. The pole material was assumed to be dysprosium, which has a saturation magnetization of 3.3 T at 77 K. The achievable maximum field of this simply structured device is close to that of a cryogenic permanent magnet undulator. We present calculated performances of cryogenic staggered undulators at various periods and gaps. *O. Chubar, P. Elleaume, J. Chavanne, J. Synchrotron Radiat. 5, 481 (1998). |
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| RPAE006 | Feasibility Study on Introducing a Superconducting Wiggler to Saga Light Source | 1021 |
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| Saga light source (SAGA-LS) is the synchrotron radiation facility, which consists of 250 MeV electron linac and 1.4 GeV storage ring. We have a plan to introduce an existing superconducting wiggler, which has been developed for other project by National Institute of Radiological Sciences. The superconducting wiggler consists of a main pole of 7T and two side poles of 4T. Each pole is composed of a racetrack-shaped coil and an iron core. We have examined the effects of the wiggler on the beam optics when it is introduced into SAGA-LS. The distribution of multipole components in the planes perpendicular to the electron orbit, which is deformed by the wiggler fields, have been calculated using magnetic field calculation code RADIA. Then the lattice function and the dynamic aperture of the ring have been calculated by the lattice calculation code SAD. The results show that the tune shift due to the quadrupole component of the wiggler field is as large as to make horizontal beam orbit unstable. The dynamic aperture after the tune correction becomes small by about 20%. These effects due to multipole field are considered to be tolerable for the SAGA-LS. | ||
| RPAE009 | Design Considerations for the Stability Improvement of Klystron-Modulator for PAL XFEL | 1165 |
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Funding: Supported by the POSCO and the MOST, Korea. The PAL linac is planed to be converted to a SASE-XFEL facility (PAL XFEL) that supplies coherent X-rays down to 0.3-nm wavelength. PAL XEL requires a 3-GeV driver linac and a 60-m long in-vacuum undulator to realize an X-ray SASE-FEL. The linac should supply highly bright beams with emittance of 1.2 mm-mrad, a peak current of 3.5 kA, and a low energy spread of 0.03%. The RF stability of 0.06% rms is required for both RF phase and amplitude for reasonably stable SASE output. This stability is mainly determined by a klystron-modulator. Therefore present stability level of the modulator has to be improved 10 times better to get the pulse stability of 0.05%. The regulation methods such as traditional de-Q’ing and precision inverter charging technology are reviewed. Design considerations for the stability improvement of klystron-modulator for PAL XFEL are presented. |
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| RPAE013 | Laser System for Photoelectron and X-Ray Production in the PLEIADES Compton Light Source | 1347 |
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Funding: This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48. The PLEIADES (Picosecond Laser-Electron Interaction for the Dynamic Evaluation of Structures) facility provides tunable short x-ray pulses with energies of 30-140 keV and pulse durations of 0.3 – 5 ps by scattering an intense, ultrashort laser pulse off a 35-75 MeV electron beam. Synchronization of the laser and electron beam is obtained by using a photoinjector gun, and using the same laser system to generate the electrons and the scattering laser. The Ti:Sapphire, chirped pulse amplification based 500 mJ, 50 fs, 810 nm scattering laser and the similar 300 μJ, 5 ps, 266 nm photoinjector laser systems are detailed. Additionally, an optical parametric chirped pulse amplification (OPCPA) system is studied as a replacement for part of the scattering laser front end. Such a change would significantly simplify the set-up the laser system by removing the need for active switching optics, as well as increase the pre-pulse contrast ratio which will be important when part of the scattering laser is used as a pump beam in pump-probe diffraction experiments using the ultrashort tunable x-rays generated as the probe. |
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| RPAE014 | High-Energy Compton Scattering Light Sources | |
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Funding: This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48. No monochromatic, high-brightness, tunable light sources currently exist above 100 keV. Important applications that would benefit from such new hard x-ray sources include: nuclear resonance fluorescence spectroscopy, time-resolved positron annihilation spectroscopy, and MeV flash radiography. The peak brightness of Compton scattering light sources is derived for head-on collisions and found to scale with the electron beam brightness and the drive laser pulse energy. This gamma2-scaling shows that for low emittance electron beams (1 nC, 1 mm.mrad, < 1 ps, > 100 MeV), and tabletop laser systems (1-10 J, 5 ps) the x-ray peak brightness can exceed 1023 photons / mm2 x mrad2 x s x 0.1% bandwidth near 1 MeV; this is confirmed by 3D codes that have been benchmarked against Compton scattering experiments performed at LLNL. Important nonlinear effects, including spectral broadening, are also taken into account in our analysis; they show that there is an optimum laser pulse duration in this geometry, of the order of a few picoseconds, in sharp contrast with the initial approach to laser-driven Compton scattering sources where femtosecond laser systems were thought to be mandatory. |
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| RPAE015 | High Energy, High Brightness X-Rays Produced by Compton Back Scattering at the Livermore PLEIADES facility | 1464 |
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Funding: This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract no. W-7405-Eng-48. PLEIADES (Picosecond Laser Electron Interaction for the Dynamic Evaluation of Structures) produces tunable 30-140 keV x-rays with 0.3-5 ps pulse lengths and 107 photons/pulse by colliding a high brightness electron beam with a high power laser. The electron beam is created by an rf photo-injector system, accelerated by a 120 MeV linac, and focused to 20 mm with novel permanent magnet quadrupoles. To produce Compton back scattered x-rays, the electron bunch is overlapped with a Ti:Sapphire laser that delivers 500 mJ, 80 fs, pulses to the interaction point. K-edge radiography at 115 keV on Uranium has verified the angle correlated energy spectrum inherent in Compton scattering and high-energy tunability of the Livermore source. Current upgrades to the facility will allow laser pumping of targets synchronized to the x-ray source enabling dynamic diffraction and time-resolved studies of high Z materials. Near future plans include extending the radiation energies to >400 keV, allowing for nuclear fluorescence studies of materials. |
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| RPAE016 | Smith-Purcell Radiation from a Charge Moving Above a Finite-Length Grating | 1496 |
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Funding: This work was supported by the Department of Energy, High Energy Physics, under contract DE-FG02-91ER40648. Smith-Purcell radiation (SPR), emitted when a bunch is passing above a periodic structure, is characterized by a broadband radiation spectrum in which the wavelength depends on the observation angle. While various theoretical models agree on this dependence, a significant difference is introduced for the calculated radiated energy by the different approaches. We present two theoretical calculations of the SPR from a 2D bunch of relativistic electrons passing above a finite length grating. The first one uses the finite-difference time-domain approach and the second one uses an electric-field integral equation (EFIE) method. Good agreement is obtained between these two calculations. The results of these calculations are then compared with a formalism based on an infinite length grating in which a periodic boundary condition is rigorously applied. For gratings with less than approximately 50 periods, a significant error in the strength of the radiated field is introduced by the infinite grating approximation. This error disappears asymptotically as the number of periods increases. We are currently working on extending the EFIE model to the case of a three dimensional bunch moving above a finite-length grating. |
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| RPAE017 | Radially Polarized Ion Channel Laser | 1526 |
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| Radially polarized radiation is amplified by a free electron laser (FEL) in which the undulator is an ion channel with uniform density. For long betatron wavelengths and low gain per pass, the gain at a given distance from the axis is three-eighths the gain of a periodic ion channel laser with the same wiggler parameter. For amplification of short wavelengths by an ultrarelativistic electron beam, a uniform-density ion channel requires a much higher ion density than a periodic ion channel laser. | ||
| RPAE018 | Calculation of Reflection Matrix Elements of a Grating for Growing Evanescent Waves | 1616 |
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Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38. Reflection matrix elements of a grating play an important role in the study of Smith-Purcell (SP) free-electron lasers (FELs). Especially, the matrix element e00, which couples the incident co-propagating evanescent wave to the outgoing co-propagating evanescent wave, is important for the evaluation of the gain of an SP FEL system.* We use the modal expansion method as well as the integral method and extend them to the case of growing evanescent waves. We present the results of numerical calculations for rectangular and sinusoidal gratings. We study the singularity of e00 and find that it is possible to get a simple formula for the location of singularity for the case of rectangular grating if we chose the eigenmodes of the groove as the basis set as done by Andrews et. al.** *K.-J. Kim and S. B. Song, Nucl. Instrum. Methods Phys. Res. A 475, 158 (2001). **H. L. Andrews and C. A. Brau, Phys. Rev. ST Accel. Beams 7, 07070 (2004). |
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| RPAE019 | Positron Source from Betatron X-Rays Emitted in a Plasma Wiggler | 1625 |
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| In the E-167 plasma wakefield accelerator (PWFA) experiments in the Final Focus Test Beam (FFTB) at the Stanford Linear Accelerator Center (SLAC), an ultra-short, 28.5 GeV electron beam field ionizes a neutral column of Lithium vapor. In the underdense regime, all plasma electrons are expelled creating an ion column. The beam electrons undergo multiple betatron oscillations leading to a large flux of broadband synchrotron radiation. With a plasma density of 3x1017 cm-3, the effective focusing gradient is near 9 MT/m with critical photon energies exceeding 50 MeV for on-axis radiation. A positron source is the initial application being explored for these X-rays, as photo-production of positrons eliminates many of the thermal stress and shock wave issues associated with traditional Bremsstrahlung sources. Photo-production of positrons has been well-studied; however, the brightness of plasma X-ray sources provides certain advantages. In this paper, we present results of the simulated radiation spectra for the E-167 experiments, and compute the expected positron yield. | ||
| RPAE020 | Production of High Harmonic X-Ray Radiation from Non-linear Thomson at LLNL PLEIADES | 1673 |
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Funding: US-DOE under contract no. DE-FG-98ER45693 and DE-FG03-92ER40693, and by LLNL under contract no. W-7405-Eng-48 and the LLNL ILSA program under contract LS04-001-B. We describe an experiment for production of high harmonic x-ray radiation from Thomson backscattering of an ultra-short high power density laser by a relativistic electron beam at the PLEIADES facility at LLNL. In this scenario, electrons execute a “figure-8” motion under the influence of the high-intensity laser field, where the constant characterizing the field strength is expected to exceed unity: $aL=e*EL/m*c*ωL ≥ 1$. With large $aL$ this motion produces high harmonic x-ray radiation and significant broadening of the spectral peaks. This paper is intended to give a layout of the PLEIADES experiment, along with progress towards experimental goals. |
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| RPAE021 | Feasibility Study of a Laser Beat-Wave Seeded THz FEL at the Neptune Laboratory | 1721 |
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Funding: The work was supported by the DOE Contract No. DE-FG03-92ER40727. Free-Electron Laser in the THz range can be used to generate high output power radiation or to modulate the electron beam longitudinally on the radiation wavelength scale. Microbunching on the scale of 1-5 THz is of particular importance for potential phase-locking of a modulated electron beam to a laser-driven plasma accelerating structure. However the lack of a seeding source for the FEL at this spectral range limits operation to a SASE FEL only, which denies a subpicosecond synchronization of the current modulation or radiation with an external laser source. One possibility to overcome this problem is to seed the FEL with two external laser beams, which difference (beat-wave) frequency is matched to the resonant FEL frequency in the THz range. In this presentation we study feasibility of an experiment on laser beat-wave injection in the THz FEL considered at the UCLA Neptune Laboratory, where both a high brightness photoinjector and a two-wavelength, TW-class CO2 laser system exist. By incorporating the energy modulation of the electron beam by the ponderomotive force of the beat-wave in a modified version of the time-dependent FEL code Genesis 1.3, the performance of a FEL at Neptune is simulated and analyzed. |
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| RPAE022 | Improved Long Radius of Curvature Measurement System for FEL Mirrors | 1787 |
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Funding: This work is supported by the U.S. AFOSR MFEL grant F49620-001-0370. The 53.73 meter long Duke free electron laser (FEL) cavity consists of two concave mirrors with radius of curvature longer than 27 meters. A proper radius of curvature is designed to achieve an optimal and stable operation of the FEL. This requires accurate measurements of the cavity mirror's radius of curvature before its initial installation. Subsequent radius of curvature measurements are performed to ensure no significant deformation of the mirror occurs after a period of extensive use. A direct measurement based upon the geometric optics principles has been used at DFELL for years. Recently, we have significantly upgraded this measurement apparatus by utilizing a HeNe laser as the light source and a straight wire with a proper size as the object. In this paper we describe the details of the measurement setup and report the benefits of the recent upgrades. In addition, we report the improved data analysis technique and results of recent long radius of curvature measurements. |
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| RPAE027 | Linear Optics Measurements in the ESRF Booster | 1973 |
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| A series of experiments has been conducted in the ESRF booster in order to measure its linear optics. A steerer response matrix was developed and used to optimise the orbit correction at injection by developing a refined model. This matrix was also used to measure the beta functions along the accelerating cycle and the steerer calibration. Dispersion was also measured with classical RF scans and compared to theory. Finally, chromaticity measurements were performed for different sextupole settings enabling their calibration and optimisation. | ||
| RPAE028 | Lattice Upgrade Options for the ESRF Storage Ring | 2047 |
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| Several scenarios of lattice upgrade for the ESRF storage ring are under study. In order to minimise the cost, their design is based on the length constraints of the existing tunnel with the ID beamlines kept in place. The goal is to shrink the emittance in order to increase the undulator brilliance. The two main options are a double bend achromat structure with non-uniform field dipoles and a triple bend achromat lattice. The two scenarios are detailed and compared with respect to their linear optics solutions, correction of chromatic effects and non-linear dynamics. An attempt to reveal the horizontal effective emittance dependence on important design parameters, such as optics functions maxima, chromaticity and dynamic aperture, is also undertaken. Technological challenges concerning magnet design with small physical aperture in a reduced space are also addressed. | ||
| RPAE029 | Analytical Considerations for Reducing the Effective Emittance with Variable Dipole Field Strengths | 2086 |
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| The basic optics design scope in lepton rings is to match the sections in either side of the bending magnets in order to minimise the equilibrium emittance. A further important emittance reduction can be achieved by incorporating dipoles for which the deflecting field varies along the electron beam path in the magnet. The figure of merit for such lattices when used in a synchrotron light source is the minimization of the so-called effective emittance. The effective emittance is computed in the middle of the undulator straight section as the product of the rms size and divergence and therefore includes contributions from the betatron emittance and from the electron energy spread. In this paper, analytical formulas are obtained for the minimum betatron and effective emittance in arbitrary dipole fields and the associated optics function at the dipole entrance. Examples are given for specific dipole field functions and their properties with respect to the effective emittance minimisation. Finally, the effective emittance is parameterised with respect to standard cell optics properties, such as the phase advance, the maximum beta and dispersion functions and the focusing element strengths. | ||
| RPAE030 | Status of the SOLEIL Booster Synchrotron | 2155 |
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Funding: SOLEIL. SOLEIL is a 2.75 GeV third generation synchrotron radiation facility under construction near Paris. The injection system is composed of a 100 MeV electron Linac pre-accelerator followed by a full energy (2.75 GeV) booster synchrotron. The booster lattice is based on a FODO structure with missing magnet. With a circumference of 157 m and low field magnets (0.74 T), the emittance is of 150 nm.rad at 2.75 GeV. A flexible and economic ramping switched mode procedure for the main supply cycled up to 3 Hz and a 35 kW-352 MHz solid state amplifier powering the RF system are used. At present time, all the magnets, supports and vacuum have been received and tested. Half of the ring is already assembled and installation is the tunnel will begin in January 05. The pulsed elements and their pulser will be received and tested from January to April. The four main magnet power supplies will be received in February and tested in Marsh. We plan the booster commissioning with beam in May 2005. |
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| RPAE031 | Progress Report on the Construction of SOLEIL | 2203 |
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Funding: SOLEIL This paper reports the progress achieved in the construction of the accelerators of SOLEIL. Started in January 2002, the construction comes near to its end and the installation of the equipment on the site has begun from September 2004 and shall be completed within one year. The progress on the LINAC and Booster are reported separately, therefore this paper will focus more particularly on the Storage Ring: Dedicated measuring benches have been built to perform the magnetic measurements on all the magnets and the results of measurements have been analysed in term of particle dynamics behaviour in order to prepare the operating point for the commissioning. The status of innovative developments engaged from the beginning as super-conducting RF cavities, NEG coated vacuum chambers and BPMs digital electronics will be described. The construction of the first 6 insertion devices is also well advanced and will be reported. Finally, the machine impedance budget was further evaluated with consequently, still some modifications to the design of some components. |
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| RPAE032 | Femtosecond Laser-Electron Interaction in a Storage Ring Studied by Terahertz Radiation | 2239 |
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Funding: This work was supported by the german Bundesministerium für Bildung und Forschung (BMBF). The laser-induced energy modulation of relativistic electrons in the BESSY II storage ring was studied by temporal and spectral characterization of femtosecond far infrared (THz) pulses being emitted due to the fact that dispersive elements convert the energy modulation into a longitudinal density modulation. Bunch shapes down to 3 ps and phase noise effects as well as the length of the femtosecond density modulation and its temporal decay were measured. The THz diagnostics is crucial for the operation of the recently commissioned undulator based "femtosecond slicing" source at BESSY. |
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| RPAE033 | Commissioning Results from the BESSY II Femtoslicing Source | 2309 |
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Funding: Funded by the Bundesministerium für Bildung und Forschung and by the Land Berlin. At the BESSY II storage ring, a source of sub-100 fs x-ray pulses with tunable polarization and excellent signal-to-background ratio has been constructed in 2004. This source is based on laser-induced energy modulation ("femtoslicing") and subsequent angular separation of the short-pulse x-rays emitted by an elliptical undulator. The paper reviews the layout of the source and reports on new insights and experimental results obtained while commissioning the source for user operation. |
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| RPAE034 | Storage Ring Fill Patterns for Femtoslicing Applications | 2327 |
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Funding: Funded by the Bundesministerium für Bildung und Forschung and by the Land Berlin. The generation of laser-induced ultrashort synchrotron radiation pulses ("femtoslicing") during user operation at the BESSY II storage ring requires to add several bunches with enhanced charge to the routinely used multibunch fill. The paper addresses these specialized fill patterns in view of beam stability against multibunch oscillations and ion effects, beam lifetime, and the effect of beam loading on the synchronous phase angles. |
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| RPAE035 | Orbit Stability at BESSY | 2366 |
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Funding: Funded by the Bundesministerium für Bildung und Forschung and by the Land Berlin. Traditionally intrinsic component stability as well as perturbation source identification and suppression (like set-up modifications or feed-forward compensations) have been the preferred methods used to guarantee beam orbit stability for user operation at BESSY. Second focus of activity is the reliability of slow drift control and the high degree of beam position reproducibility maintained under frequently changed operation conditions. Along these lines an overview of the measures taken, the available diagnostic means as well as the achievements and shortcomings of the existing slow orbit feedback is given. Diagnostic capabilities of a fast BPM read-out and data distribution system give insight into the demands on a fast orbit feedback that could provide better operation flexibility and improved performance. |
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| RPAE036 | Damping Wigglers for the PETRA III Light Source | 2446 |
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| Within the reconstruction of the PETRA booster ring at DESY towards a third generation light source after 2007, damping wigglers will be installed to reduce the emittance to a value of 1 nmrad. Two damping sections in the long straights of PETRA have been assigned to accommodate 20 wigglers in total. The wigglers will be permanent magnet devices with a fixed gap which are surrounded by an iron enclosure to reduce the leakage flux. Each wiggler will provide a damping integral of 4 T2m per segment and generate a synchrotron radiation power of 42 kW. A short one period long prototype has recently been built to prove the magnetic design and study the correction scheme for tuning the pole strength. The wiggler segments will be followed by an SR absorber shading the downstream quadrupole and successive wiggler segment, the accumulated on-axis power of about 200 kW will be taken up by the final absorber at the damping section end. | ||
| RPAE037 | Operation with a Low Emittance Optics at ANKA | 2467 |
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| ANKA is a synchrotron light source operating in an energy range from 0.5 to 2.5 GeV. The electron storage ring at ANKA is designed as a variation of an eightfold Double Bend Achromat structure. Since its commissioning the facility has been operated with zero dispersion in the long straight sections resulting in an emittance of about 100 nmrad. Since mid 2004 ANKA is operated with dispersion distributed over the complete ring thus reducing the emittance to 40 nmrad. In the course of the re-design of the storage ring optics a compensation of higher order field components leads to a visibly increased momentum acceptance. Optics calculations and measurements as well as operational experience will be discussed. | ||
| RPAE038 | Far Infrared Coherent Synchrotron Edge Radiation at ANKA | 2518 |
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| A synchrotron radiation source emits coherent infrared (IR) radiation when the electron bunch length is comparable to the wavelength of the emitted radiation. To generate coherent radiation in the far IR (THz) region, a "low alpha mode" has been devised at the ANKA storage ring operating at 1.3 GeV. The corresponding lattice has a significantly reduced momentum compaction factor. The spectral dependence of the emitted radiation is recorded at the ANKA-IR beamline, where the synchrotron light is produced in the fringe field of a bending magnet. This edge radiation has the advantage of being more collimated than constant field radiation. This allows the observation of frequencies down to 1 cm-1 through a modest vertical aperture, which would not be possible with classical constant field emission due to the increasing beam divergence with decreasing frequency. The onset of coherent emission is found at a synchrotron frequency of about 10 kHz. At 5 kHz, an intensity enhancement of up to 5 orders of magnitude, with respect to the incoherent emission, is observed in the spectral range between 1 and 65 cm-1. | ||
| RPAE039 | Operation of the ANKA Synchrotron Light Source with Superconductive Undulators | 2559 |
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| The synchrotron light source ANKA (2.5 GeV, 200 mA) is a versatile multi-purpose storage ring with beam lines for coherent IR and THz radiation (IR-laser), LIGA applications and high brilliance X-rays. It is now plannned to install in addition several superconductive undulators for a wide range of applications: fast tunable X-rays for material research, imaging applications and an undulator with variable polarization direction for a dichroism beamline. This development of ANKA is the result of successful research on superconductive undulators which surpass the performance of permanent undulators by far (collaboration between ANKA, the University of Karlsruhe and the University of Erlangen-Nürnberg). The basic layout of the undulators and the required changes to a storage ring to accommodate the superconductive undulators is described in this paper. | ||
| RPAE040 | COD Correction at the PF and PF-AR by New Orbit Feedback Scheme | 2613 |
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| The eigen-vector method with a constraint condition is a new COD correction method that enables us to combine the local orbit correction at the insertion devices with the global COD correction by integrating the local one into the global one as the constraint condition using the Lagrange’s undetermined multiplier method. In order to achieve this method, we only use the new contrived response matrix for the global COD correction where the local correction is involved and done simultaneously. We have tested this correction scheme at the PF ring and the PF-AR. In the machine studies, the new orbit correction method is successfully demonstrated. The RMS COD of the constraint BPMs are sufficiently suppressed and, on the other hand, there is almost no large difference in the RMS COD of all the other BPMs between the new and ordinary methods. | ||
| RPAE041 | Reconstruction of Photon Factory Storage Ring for the Straight-Sections Upgrade Project | 2678 |
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| The Photon Factory (PF) storage ring is a 2.5-GeV synchrotron light source at KEK. In 1997, we have accomplished a large reconstruction of the ring in order to reduce the beam emittance from 130 nm rad to 36 nm rad. After the reconstruction, the PF ring has continued a stable operation over 5000 hours a year. Now we are proceeding with another upgrade project to create four new straight sections and to largely lengthen the existing 10 straight sections. The shutdown for the upgrade project is scheduled for the period March-September 2005. The lattice configuration around the straight sections will be modified by replacing quadrupole magnets with new shorter ones and by placing them closer to the near-by bending magnets. Simultaneously the beam duct in two thirds of the storage ring will be replaced. Due to this modification of the lattice, the practical emittance will be reduced to 27 nm rad. The new straight sections will have low beta functions and suitable for housing short-period narrow-gap undulators. The in-vacuum undulators, which have a sufficiently high brilliance within a spectral range from 8 to 16 keV, are being developed now. | ||
| RPAE042 | Optimization of Kicker Pulse Bump by Using a SR Monitor at the Photon Factory | 2717 |
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| We plan to operate the Photon Factory storage ring by top-up injection mode from 2006. To realize this operation mode, remaining coherent oscillation of the stored beam due to error in the injection pulse bump is one of most serious problem. To reducing the error in the injection pulse bump, we calibrated kicking angles of the injection kicker magnets by means of the term by term instantaneous observation of beam profile. We have a SR monitor inside of injection pulse bump. By measureing the tern by tern beam position after the excitation of kicker magnet, we can calibrate the kick angle of the kicker magnet. By using this calibration, we optimized injection pulse bump. As a result, we reduced amplitude of remaining coherent oscillation less than 1/4 of the 1??of the beam size. | ||
| RPAE043 | Beam Position Monitor for Undulator by Using SR Monitor Technique | 2789 |
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| A beam position monitor for the undulator by using the optical SR monitor technique has been tested in the Photon Factory. A visible SR in far tail of the undurater spectrum is extracted by a water-cooled beryllium mirror. The extraction mirror has a hole in the center for passing through the central peak of the undulator radiation which has an opening angle of 1/gamma. Extracted visible light in large opening angle has exactly same optical axis of the undulator radiation, because of it’s a far tail of the spectrum of same radiation. We applied focusing system to observe the beam position in the undulator through the optical image of beam. The results show us this method is applicable to monitor a position of beam in the undulator, and gap change of undulator has no effect of beam position monitoring. We can easily measure the angle of visible ray, this method is applicable not only beam position monitor but also monitoring the angular deviation of undulator radiation. | ||
| RPAE044 | Operation and Recent Developments of the Photon Factory Advanced Ring | 2845 |
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| The Photon Factory Advanced Ring (PF-AR) is a synchrotron light source dedicated to X-ray research. The PF-AR is usually operated at a beam energy of 6.5 GeV, but a 5.0 GeV mode is also available for medical application. In 6.5 GeV mode the typical lifetime of 15 hrs and the beam current of 60 mA with a single-bunch have been archived. Almost full-time single-bunch operation for pulse X-ray characterize the PF-AR. However, single-bunch high-current caused several problems to be solved, including the temperature rise of the some of the vacuum component, a pressure increase in the ring, and a sudden drop in lifetime. In order to avoid these issues the developments of new methods have been continued. In this paper, the status and the recent developments of the PF-AR will be presented. It concerns: the successful operation with two-bunch high-current in 5.0 GeV mode; varying the vertical beam size for the medical application; modulating the RF acceleration phase in order to elongate the length of bunch; stabilizing temperature in the ring tunnel; the study for medium emittance operation with 160 nmrad; moving the RF cavities in order to install a new insertion device; an innovative injection scheme using a pulsed quadrupole magnet. | ||
| RPAE045 | Production of Short Electron Bunches by Slow and Fast Excitations of Longitudinal Bunch-Shape Oscillations | 2887 |
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In the Brookhaven Alternating Gradient Synchrotron (AGS), adiabatic excitation of longitudinal bunch-shape oscillations has been successfully used for extracting shortened proton bunches.* We applied this technique to the electron storage ring. In case of electron machines, growth time of bunch-shape oscillations should be shorter than the radiation damping time for preventing radiation excitation. We demonstrated in the 2.5-GeV Photon Factory storage ring that electron bunches could be shortened by a factor of about two from its natural length using this technique. We show that non-adiabatic excitation of oscillations is also very useful for obtaining shorter bunches.
*M. Bai et al., Phys. Rev. ST Accel. Beams 3, 064001 (2000). |
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| RPAE046 | Operational Status at the PLS: Recent Improvements and Changes | 2923 |
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| PLS has been operated 10 years since 1994. A few improvements has been made to stabilize the reference orbit drifts caused by insertion devices and other sources: The control system has been upgraded to 20 bit capability from 12 bit. The slow global orbit feedback is employed routinely in the user run times. These improvements and the operational status changes will be presented in this report. | ||
| RPAE047 | Lattice Study for the Taiwan Photon Source | 2989 |
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| The feasibility study for the new 3.0~3.3 GeV Taiwan synchrotron light source, dubbed Taiwan Photon Source, was initiated in July, 2004. The goal is to construct a high performance light source with extremely bright X-ray in complementary to the existing 1.5 GeV light source in Taiwan. The ring circumference is 518.4 m and a 24-cell DBA lattice structure is chosen. The natural emittance with distributed dispersion is less than 2 nm-rad. A large booster ring of 499.2 m sharing the storage ring tunnel will be adopted. | ||
| RPAE048 | Design Consideration of a Booster for Taiwan Photon Source | 2992 |
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| After more than 10 years' operation and expansion, the Taiwan Light Source (TLS) of National Synchrotron Radiation Research Center (NSRRC) reaches very stable operation condition. The storage ring has better than 96% of beam availability annually with 6 Insertion Devices (ID) in a six-folds symmetry over-crowded machine. Two superconducting IDs and one superconducting RF cavity were installed in recent year, which intend to push the photon energy to hard x-ray regime and double the photon flux with better beam quality. Beamlines and experimental stations occupied all over the experimental area. The uproar for more beamlines in higher photon energy with higher brightness was frequently transpired from users' community. The Board of Trustee of NSRRC gave a green light to a new design and construction of median-energy light source, Taiwan Photon Source (TPS) in the coming decade. This paper will present two draft designs of booster and the consideration of the design criteria for new booster to work with a top-up injected and very low-emittance storage ring. | ||
| RPAE049 | Revision of Booster to Storage Ring Transport Line Design and Injection Scheme for Top-Up Operation at NSRRC | 3085 |
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| In order to help the operation of constant current, the optics of booster to storage ring transport line (BTS) design is reinvestigated. The initial twiss parameters are derived by measurement. The optics of the transport line is readjusted according to the measured initial beam parameters. The design of pulse width of the injection kicker is also changed from 1.2μsecond to 2.0μsecond. The injection scheme is reviewed and the effects of the kicker error on both injected beam and stored beam are investigated and shown in this report. | ||
| RPAE050 | Status of the CAMD Light Source | 3103 |
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| With the increasing diversity of its research program, the CAMD Light Source has improved its beam brightness and quality. Using a well calibrated model of the lattice, the ring optic has been refined to generate a lower beam emittance of 150 nm.rad and this has been confirmed by measuring the beta values with the modulated quadrupole shunt system. The beam sizes have also been measured with an X-ray pinhole camera and compared to the calculated emittance. The beam orbit is corrected to a standard position referenced to the quadrupole centers to a precision better than 0.5 mm, using a suite of well localized bumps which can also flexibly steer the user photon beams to their requirements. Beam reliability has been improved by bringing into use a VME control system for the energy ramp. | ||
| RPAE051 | Multipole Design for CAMD Storage Ring | 3161 |
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| The CAMD storage ring has been in operation more than 12 years with only sextupole elements in the lattice for correction of nonlinear beam dynamics. To compensate for coupling arising from the integrated effect of skewed elements around the ring, and to improve beam lifetime, a multipole element is required which can be operated in active mode. The design of a magnetic multipole is presented as well as power and control systems designs. The strength and effect and of this element are calculated. | ||
| RPAE052 | Overview of Accelerator Physics Studies and High Level Software for the Diamond Light Source | 3188 |
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| DIAMOND is a 3 GeV synchrotron light source under construction at Rutherford Appleton Laboratory in Oxfordshire (UK). The accelerators complex consists of a 100 MeV LINAC, a full energy booster and a 3GeV storage ring with 22 straight sections available for IDs. Installation of all three accelerators has begun, and LINAC commissioning is due to start in Spring 2005. This paper will give an overview of the accelerator physics activity to produce final layouts and prepare for the commissioning of the accelerator complex. The DIAMOND facility is expected to be operational for users in 2007 | ||
| RPAE053 | Transient Generation of Short Pulses in the APS Storage Ring | 3247 |
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Funding: This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38. A method for obtaining very short pulses using modulation of the accelerating voltage gradient is described and simulation results given. The idea is to operate the two rf stations with a phase separation adjusted so that the synchronous particle resides on the crest of one of the sources. Phase modulation of the on-crest system at twice the synchrotron frequency induces a longitudinal bunch shape oscillation with significantly reduced bunch length occurring twice each synchrotron period. Pulsed and steady-state operation will be discussed using various accelerator parameters. |
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| RPAE054 | Beam Stability at the Advanced Photon Source | 3268 |
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Funding: This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38. The Advanced Photon Source has been in operation since 1996. Since that time, extensive incremental improvements to orbit stabilization systems have been made. This includes the addition of 80 channels of narrowband rf beam position monitors (bpm's), 40 channels of bending magnet photon bpm's, and most recently the inclusion of 36 insertion device photon bpm's into the orbit correction response matrix. In addition, considerable improvements have been made in the area of power supply regulation, both for the main multipole magnets and the steering corrector magnets. The present status of overall performance will be discussed, including long term pointing stability, reproducibility, and AC beam motion. |
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| RPAE055 | Results of Preliminary Tests of PAR Bunch Cleaning | 3307 |
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Funding: This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38. A particle accumulator ring (PAR) is used at the Advanced Photon Source (APS) to collect multiple linac bunches and compress them into a 0.3-ns (rms) single bunch for booster injection. A 9.77-MHz fundamental rf system and a 117.3-MHz harmonic rf system are employed for initial beam capture and bunch length compression. Satellite bunches with very low charge form due to rf phase drifts or beam loading change. These satellites, when injected into the booster and then into the storage ring (SR), cause bunch impurity at three buckets from the target bucket. Storage ring and booster bunch cleaning was tried but proved to be difficult due to the top-up mode of operation in the storage ring and tune drift in the booster synchrotron. Recently we implemented a PAR bunch-cleaning system with tune-modulated harmonic rf knockout. Preliminary tests gave a measured SR bunch purity of better than 10-6, which shows that the cleaning method is feasible and could achieve a bunch purity goal of 10-8. This report describes the system configuration, test results, and system performance. |
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| RPAE056 | NSLS II: The Future of the NSLS | 3345 |
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Funding: Under Contract with the United States Department of Energy Contract Number DE-AC02-98CH10886 The National Synchrotron Light Source at BNL was the first dedicated light source facility and it has now operated for more than 20 years. During this time the user community has grown to more than 2400 users annually. To insure that this vibrant user community has access to the highest quality photon beams, the NSLS is pursuing the design of a new ultra-high brightness (~10E21) electron storage ring, tailored to the 0.3-20 KeV photon energy range. We present our preliminary design and review the critical accelerator physics design issues. |
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| RPAE057 | Dynamic Aperture Optimization for Low Emittance Light Sources | 3378 |
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Funding: Under Contract with the United States Department of Energy Contract Number DE-AC02-98CH10886. State of the art low emittance light source lattices, require small bend angle dipole magnets and strong quadrupoles. This in turn creates large chromaticity and small value of dispersion in the lattice. To counter the high chromaticity strong sextupoles are required which limit the dynamic aperture. Traditional methods for expanding the dynamic aperture use harmonic sextupoles to counter the tune shift with amplitude. This has been successful up to now, but is non-deterministic and limited as the sextupole strength increases, driving higher order nonlinearities. We have taken a different approach that makes use of the tune flexibility of a TBA lattice to minimize the lowest order nonlinearities, freeing the harmonic sextupoles to counter the higher order nonlinearities. This procedure is being used to improve the nonlinear dynamics of the NSLS-II lattice. |
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| RPAE058 | NSLS-II Injection Concept | 3408 |
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| Currently the facility upgrade project is under progress at the NSLS (Brookhaven National Laboratory). The goal of NSLS-II is a 3 GeV ultra-low emittance storage ring that will provide three orders of magnitude increase in brightness over the present NSLS X-ray beamlines. The low emittance of the high brightness ring lattice results in quite short lifetimes, which makes operation in top-off injection mode a necessity. The NSLS-II injection system must be able to provide an electron beam at the high repetition rate and with good injection efficiency. In this paper we present a concept of the NSLS-II injection system and discuss conditions and constraints for the injector design. Various injection system parameters are estimated from the point of view of SR user demand. | ||
| RPAE059 | Design of 3 GeV Booster for NSLS-II | 3473 |
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| We present preliminary design of full energy booster for NSLS-II. In the paper we analyze single- and multi-bunch modes of the booster operations. The booster lattice consists of 24 TME cells with two dispersion suppressors. Initial design of the magnets, power supply specifications, Eddy current contribution to the booster chromaticity are discussed. | ||
| RPAE060 | Simulation and Automation of the EEBI Test at ALS | 3485 |
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Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. The Errant Electron Beam Interlock (EEBI) is a system that protects the vacuum chamber of the Advanced Light Source (ALS) from synchrotron light damage should the orbit, through a superconducting bend magnet (superbend), become distorted. The EEBI system monitors the vertical beam position on two BPMs, one upstream and the other downstream, of the superbend and dumps the stored beam if the orbit exceeds preset limits in either offset or angle. Discussed are the modeling studies carried out to determine how to create a large vertical bump, both for performing the test and implementing the automated test software. |
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| RPAE061 | Beam Loss Simulation Studies for ALS Top-Off Operation | 3532 |
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Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. The ALS is planning to operate with top-off injection at higher beam currents and smaller vertical beam size. As part of a radiation safety study for top-off, we carried out two kinds of tracking studies: (1) to confirm that the injected beam cannot go into users’ photon beam lines, and (2) to control the location of beam dump when the storage ring RF is tripped. (1) is done by tracking electrons from a photon beam line to the injection sector inversely by including the magnetic field profiles, varying the field strength with geometric aperture limits to conclude that it is impossible. (2) is done by tracking an electron with radiation in the 6-dim space for different combinations of vertical scrapers for the realistic lattice with errors. |
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| RPAE062 | Estimation of the Effective Magnet Misalignments of the ALS Storage Ring | 3559 |
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Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC03-76SF00098 New storage ring lattices have traditionally been commissioned using a trial-and-error approach, where the number of turns circulated is slowly built up until enough beam is stored to correct the orbit. We have found that by combining the calculated response matrix of magnet misalignments from a linear model of a new lattice with the measured steering magnet response matrix used during normal operations, it is possible to make an educated guess for the steering magnet settings that will immediately allow beam circulation in the new lattice. “Effective” magnet misalignments are simply those that are sufficiently close to the real misalignments to make the first guess good enough to circulate beam; the relationship between effective and real magnet misalignments is also discussed in the paper. This predictive steering method makes the process of establishing enough circulating beam for SVD-based orbit correction in a new lattice very efficient. |
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| RPAE065 | Generation of Picosecond X-Ray Pulses in the ALS Using RF Orbit Deflection | 3659 |
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Funding: This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Materials Sciences Division of the U.S. Department of Energy, under Contract No. DE-AC03-76SF00098. A scheme is studied for producing ps length pulses of x-ray radiation from the Advanced Light Source (ALS) using two RF deflecting cavities. The cavities create vertical displacements of electrons correlated with their longitudinal position in the bunch. The two cavities separated by 180 degrees of vertical phase advance. This allows the vertical kick from one cavity to be compensated by the vertical kick of the other. The location of the cavities corresponds to the end of one straight section and the beginning of the following straight section. Halfway between the cavities a bending magnet source is located. The radiation from the bend can be compressed to ~1 ps in duration. |
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| RPAE066 | Terahertz Coherent Synchrotron Radiation from Femtosecond Laser Modulation of the Electron Beam at the Advanced Light Source | 3682 |
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Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. At the Advanced Light Source (ALS), the "femtoslicing" beamline is in operation since 1999 for the production of x-ray synchrotron radiation pulses with femtosecond duration. The mechanism used for generating the short x-ray pulses induces at the same time temporary structures in the electron bunch longitudinal distribution with very short characteristic length. Such structures emit intense coherent synchrotron radiation (CSR) in the terahertz frequency range. This CSR, whose measured intensity is routinely used as a diagnostics for the tune-up of the femtoslicing experiments, represents a potential source of terahertz radiation with very interesting features. Several measurements have been performed for its characterization and in this paper an updated description of the experimental results and of their interpretation is presented. |
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| RPAE067 | Investigations, Experiments, and Implications for Using Existing Pulse Magnets for 'topoff' Operation at the Advanced Light Source | 3727 |
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Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. ALS top-off mode of operation will require injection of the electron beam from the Booster Ring into the Storage Ring at the full ALS energy level of 1.9GeV. Currently the Booster delivers a beam at 1.5GeV to the Storage Ring where it is then ramped to the full energy and stored for the user operation. The higher Booster beam energy will require the pulse magnets in the Booster and Storage Rings to operate at proportionally higher magnetic gap fields. Our group studied and tested the possible design and installation modifications required to operate the magnets and drivers at "top-off" levels. Our results and experiments show that with minor electrical modifications all the existing pulse magnet systems can be used at the higher energy levels, and the increased operational stresses should have a negligible impact on magnet reliability. Furthermore, simple electrical modifications to the storage ring thick septum will greatly reduce the present level of septum stray leakage fields into the storage ring beam. |
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| RPAE068 | Very Short Bunches in MIT-Bates South Hall Ring | 3768 |
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Funding: Department of Energy The study of ultra-short bunches in MIT SHR storage ring with very small momentum compactions is carried out. The ultra-short bunches are to greatly enhence the coherent radiation by many orders of magnitude. The ring lattice is resigned to reach very small momentum compaction factor down to 1·10-5 levels. The measurement is performed with the streak camera. The various associated issues are discussed. |
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| RPAE069 | Terahertz Coherent Synchrotron Radiation in the MIT-Bates South Hall Ring | 3783 |
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| We investigate the terahertz coherent synchrotron radiation (CSR) potential of the South Hall Ring (SHR) at MIT-Bates Linear Accelerator Center. The SHR is equipped with a unique single cavity, 2.856 GHz RF system. The high RF frequency is advantageous for producing short bunch length and for having higher bunch current threshold to generate stable CSR. Combining with other techniques such as external pulse stacking cavity, femtosecond laser slicing, the potential for generating ultra-stable, high power, broadband terahertz CSR is very attractive. Beam dynamics issues related to short bunch length operation, and may associated with the high frequency RF system, such as multi-bunch instability are concerned. They could affect bunch length, bunch intensity and beam stability. The SHR is ideal for experimental exploration of these problems. Results of initial test of low momentum compaction lattice and bunch length measurements are presented and compared to expectations. | ||
| RPAE070 | Recent Developments at Aladdin | 3813 |
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Funding: Work supported by the U.S. NSF under Award No. DMR-0084402. Following on the success of lower emittance operation at 800 MeV, SRC is pursuing a number of additional enhancements to the performance of the Aladdin storage ring. Work on Aladdin has included development of low emittance lattices at 1 GeV, which will maximize the capabilities of a recently installed spectromicroscopy beamline and a proposed high-resolution keV beamline. Installation of one-meter long insertion devices in the short straight sections within the quadrant arcs of the four sided storage ring is being considered to increase the number of undulator beamlines from four to possibly eight. Studies have been made to determine what is the minimum insertion device gap that does not interfere with nominal ring operation (injection, ramping, and lifetime at full energy), and indicate that smaller-gapped devices for higher photon energy are reasonable. Lifetime increases or further emittance reductions appear possible with modest aperture increases at a small number of points on the ring. Finally, planning is under way for long term projects such as a new injector or a next generation VUV/soft-xray source for the Midwest. Details will be presented. |
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| RPAE071 | Touschek Lifetime and Undulator Damage in the Advanced Photon Source | 3835 |
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Funding: Work supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38. The Advanced Photon Source (APS) has two insertion devices (IDs) with small-aperture vacuum chambers. The full vertical aperture in these chambers is 5 mm, while the inboard horizontal aperture is 15 mm. These devices suffer significant radiation damage, requiring frequent retuning. We recently hypothesized that the damage resulted from loss of Touschek-scattered particles on the horizontal aperture of the chambers. This results partly from the smallness of the aperture and partly from the pattern of the dispersion and beta functions in the low-emittance APS lattice. The horizontal scrapers were originally at a high-dispersion location, but, in the low-emittance lattice, they are at a fairly low-dispersion location. Similarly, the dispersion at the IDs was originally zero but is now close to the maximum for the lattice. In this paper, we summarize simulations and experiments that support our hypothesis and discuss plans to remedy the problem. |
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| RPAE072 | Simulations of X-Ray Slicing and Compression Using Crab Cavities in the Advanced Photon Source | 3886 |
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Funding: Work supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38. Recently, Zholents et al. proposed applying to the Advanced Photon Source an x-ray compression scheme based on a pair of crab cavities and asymmetric cut crystals. We have explored the feasibility and potential performance of this scheme through simulation. We used the code elegant to perform 6-D tracking, allowing us to characterize the emittance growth, which is mostly a result of sextupoles between the cavities. We also explored tolerances on alignment, phase, and voltage of the cavities; lifetime effects; tradeoffs between cavity frequency and voltage; and performance with slicing alone instead of compression. Our conclusion is that sub-picosecond rms x-ray pulse lengths should be feasible. |
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| RPAE073 | Generating Picosecond X-Ray Pulses with Beam Manipulation in Synchrotron Light Sources | 3898 |
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Funding: Work supported by U. S. Department of Energy, Office of Basic Energy Sciences under Contract No. W-31-109-ENG-38. The length of x-ray pulses generated by storage ring light sources is usually tens of picoseconds. For example, the value is 40 ps rms at the Advanced Photon Source (APS). Methods of x-ray pulse compression are of great interest at the APS. One possible method, per Zholents et al., is to tilt the electron bunch with deflecting rf cavities.* Alternately, we found that the electron bunch can develop a tilt after application of a vertical kick in the presence of nonzero chromaticity. After slicing, the x-ray pulse length is determined by the tilt angle and the vertical beam size. In principal, sub-picosecond pulses can be obtained at APS. To date we have observed 6 ps rms visible light pulses with a streak camera. Efforts are underway to attempt further compression of the x-ray pulse and to increase the brilliance. This method can be easily applied to any storage ring light sources to generate x-ray pulses up to two orders of magnitude shorter than the electron bunch length. In this paper, we will present the theory of bunch tilt, particularly the synchrobetatron coupling and decoherence beam dynamics, and the simulation and the experimental results will also be shown as verification. *A. Zholents et al., NIM A 425, 385(1999). |
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| RPAE074 | Recommissioning of Duke Storage Ring with a HOM-Damped RF Cavity and a New Straight Section Lattice for FELs | 3934 |
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Funding: This work is supported by the U.S. AFOSR MFEL grant F49620-001-0370 and by U.S. DoE grant DE-FG02-01ER41175. The Duke FEL lab operates a unique UV/VUV storage ring FEL and an FEL driven, nearly monochromatic, highly polarized, high intensity Compton gamma-ray source. The Duke storage ring light source is undergoing several phases of upgrade in order to significantly improve light source capabilities and performance. The 2004 phase included an upgrade of the RF system with a high-order mode damped RF cavity and a new 34 meter long straight section lattice to host new FEL wigglers in the next phase. This upgrade was completed in August 2004 and storage ring and light source commissioning were completed in November 2004. This paper will provide an overview of this upgrade project and report our commissioning experience of the storage ring and light sources. |
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| RPAE076 | The Commission of Hefei Light Source After Reconstruction | 3967 |
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| After the new four-kicker injection bump system was mounted, it was found that the magnetic field of four–kicker magnet through the same pulse current is different each other, the reason is which the width of pulse magnet fields is not same, so the four-kickers can not form completely local bump, and produce large global orbit distortion,and lead to beam loss. At last we found that the films of ceramic chambers were not plated evenly. The new rf system have two low level control circle circuits, which are the frequency and amplitude automatic adjustment systems. Because the energy of injection electron beam is 200MeV, and radiation damping is weak, so the gain of amplitude circuit was adjusted to the small value not to disturb beam.The beam load is large,and Robinson instability happen easily, so the small detune angle is preset. The Octupoles were inserted in ring for damping instability, and over compensated chromaticity was adjusted.Superconductor wiggler bring the variation of beta function, and the beam life time decreased from 8 hours to about 3 hours. By adjusting the beta functions close to situation ago, the beam lifetime was improved. | ||
| RPAE077 | A Magnetic Field Model for the Undulator in HLS | 3994 |
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| It is important to understand the influence of wigglers and undulators on the beam dynamics in design and optimization of a storage ring, especially when the storage ring runs on a low emittance mode. We present an analytic model of the undulator field in HLS, which can be used in the tracking study to evaluate the effects of it. Coefficients needed by the model are generated by fitting to the results of a numerical field caculation. Fringe fields are included in this model. Then we use three different methods to track particles through the undulator, and compare the results. | ||
| RPAE078 | Commissioning of SAGA Light Source | 4021 |
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| The SAGA Light Source (SAGA-LS) consists of a 250-MeV electron linac injector and an eight-hold symmetry 1.4-GeV storage ring with eight double-bend (DB) cell and eight 2.93-m long straight sections. The DB cell structure with a distributed dispersion system was chosen to produce a compact ring of 75.6-m long circumference. The machine construction begun September 29, 2003. The ring magnets of steel laminated structure, vacuum chambers made of aluminum alloy, pumping systems and four temperature controlled cooling water systems for the linac accelerating wave guides etc. were installed in March, 2004. The injector, a 500-MHz ring rf damped cavity, rf klystrons, beam transport systems for injection and their controlled systems were installed in July, 2004. The commissioning begun August 25, 2004. A 250-MeV beam was accelerated on September 29. The beam size is 1-mm in diameter and the energy spread is 0.8 % (FWHM). The first revolution of 250-MeV beam around the ring took place October 22. Beam was stored on November 12. The commissioning continues for beam storage and ramping to 1.4-GeV. We report a brief description of SAGA light source and early commissioning activities. | ||
| RPAE080 | Diagnostic Systems Plan for the Advanced Light Source Top-Off Upgrade | 4066 |
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Funding: This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Materials Science Division, of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. The Advanced Light Source (ALS) will soon be upgraded to enable top-off operation,* in which electrons are quasi-continuously injected to produce constant stored beam current. We will upgrade our injector from 1.5GeV to full-energy 1.9GeV, and top-off operation will also require more precise injector beam characterization and control than we are capable of using our current diagnostics system. Therefore, a diagnostics upgrade will be crucial for the success of top-off, and our plan for it is described in this paper. Among the improvements will be the integration of all existing beam current monitors along the accelerator chain into an injection efficiency monitoring application. New booster ring diagnostics will include a tune kick and monitoring system, updated beam position monitor electronics, and a new scraper. Two new synchrotron light monitors and a beam stop will be added to the booster-to-storage ring transfer line, and a dedicated bunch purity monitoring system will be installed in the storage ring. Together, these important diagnostic upgrades will enable smooth commissioning of the full energy injector and a quick transition to high quality top-off operation at the ALS. *Please see the ALS Top-off Upgrade presentation at this conference. |
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| RPAE082 | The New Undulator Based fs-Slicing Beamline at the ALS | 4096 |
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Funding: This work was supported by the U.S. Department of Energy, under Contract No. DE-AC03-76SF00098. The existing Femtoslicing beamline at the ALS employs a femtosecond laser beam interacting resonantly with the electron beam in a wiggler (modulator). The induced energy spread over the femtosecond duration is converted to a transverse displacement by exploiting the storage ring dispersion. The displaced femtosecond pulse radiates and produces femtosecond synchrotron radiation. Up to now a regular bending magnet was used as radiator. To improve the flux, a significant upgrade was implemented, replacing the modulator, installing an in-vacuum undulator as new radiator, and installing a higher repeptition rate laser system. The new beamline will provide 100-200 fs long pulses of soft and hard x-rays with moderate flux and with a repetion rate of 10-40 kHz for experiments concerning ultrafast dynamics in solid state physics, chemistry and biology. To achieve the necessary spatial separation of the energy modulated slice from the rest of the bunch, a sizeable local vertical dispersion bump in the radiator is required. All accelerator physics aspects of the upgrade including challenging issues like the impact on the transverse single particle dynamics will be discussed together with initial results of the commissioning. |
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| RPAE084 | Beam Dynamics Aspects of the ASP Booster | 4150 |
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| In the present contribution, beam dynamics aspects of the 3 GeV ASP booster designed and produced by Danfysik A/S are presented. The booster synchrotron, based on a lattice with combined-function magnets, will have a very small emittance of around 30 nm. The dynamical aperture (and admittance) of the booster has been investigated with tracking, and results for different tunes and chromaticities will be presented. Also the reduction in admittance caused by alignment errors of the magnets will be discussed. The nominal tunes and chromaticities are mainly determined by the combined-function magnets to (9.20, 3.25) and (1,1), respectively. Using the trim quadrupoles and sextupoles, the tunes can be adjusted in the ranges (9.05-9.45, 3.05-3.45) and the chromaticities in the range (0-2, 0-2). | ||
| RPAE085 | ELETTRA Present and Future Upgrades | 4170 |
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| During the last year, the 3rd generation synchrotron light source ELETTRA has benefitted from several upgrades which have been implemented in the frame of a project to enhance the quality of the light source. The superconducting 3rd harmonic cavity, the feedbacks, the realignment of the whole ring and other improved devices have allowed to further, significantly optimize the beam stability and lifetime, as well as the operability and uptime of the facility. At the same time two large scale projects are underway that will change the perspectives of the whole laboratory, namely the full energy booster injector and the single pass X-ray FEL FERMI@Elettra, based on the existing linac. Their status will be presented here together with the overview of the existing light source. | ||
| RPAE086 | Observation of Coherent Synchrotron Radiation at NewSUBARU | 4188 |
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| Coherent Synchrotron Radiation from a short electron bunch in a storage ring was observed at NewSUBARU. The energy of electron was 1GeV. The ring was operated with quasi-isochronous mode. The linear momentum compaction factor was smaller than 2 X 10-5 and the bunch length was shorter than 5ps (FWHM). We observed an extremely strong radiation from the weak electron beam, 1μA per bunch. | ||
| RPAE087 | Progress of the Synchrotron Light Source ALBA | 4203 |
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| ALBA will be a third generation synchrotron light source built in Spain near Barcelona. Commissioning of the storage ring is foreseen to start at the end of 2008. The design phase of ALBA is almost completed and the first components are ready to be ordered. A 100 MeV LINAC will inject electrons into a nominal energy booster synchrotron of similar circumference as the storage ring, so that both accelerators will share the same tunnel. The storage ring, working at 3 GeV with a circumference of 268.8 m, has been designed for a maximum current of 400 mA. The lattice is based on an extended DBA structure and has a nominal emittance of 4 nm.rad.The machine has a four fold symmetry with 4 long straight sections (8 m), 12 medium (4.2 m) and 8 short (2.6 m). This report concentrates on recent design developments, component choices and current status. Another paper at this conference deals with accelerator physics issues. |