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| MOPC048 | Coherent Synchrotron Radiation Burst from Electron Storage Ring under External RF Modulation | radiation, synchrotron, electron, storage-ring | 178 | ||
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It is known that a high-peak-current beam in an electron storage ring emits a burst of coherent synchrotron radiation (CSR) in the THz region. This CSR is powerful and easily obtained with no special expense, but is not used by synchrotron radiation users. This is because the burst arises from a fine time structure in the bunch due to longitudinal beam instabilities, and is unstable. We quantitatively investigated its time structure to find out how unstable it is. The measurements of CSR from one bunch showed that with an average period of 10ms (comparable with the damping time, 12 ms) the fluctuation of averaged power was about 10%. This would be reduced to 1% with 100 bunches. The fluctuation ratio had small dependence on beam charge, rf acceleration voltage and momentum compaction factor. The successive bursts had a correlation because the beam had a memory of former bursts. This worked to reduce the fluctuation in long period. When the rf phase was modulated with 2fs (twice of the synchrotron oscillation frequency), the burst structure was modulated with 2fs and the long term fluctuation was reduced. This modulation can be used to eliminate background noise in user experiments.
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| MOPP038 | Optimizing the CLIC Beam Delivery System | luminosity, radiation, synchrotron, emittance | 631 | ||
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The optimization of the new CLIC Final Focus System (FFS) with L*=3.5m is presented for a collection of CLIC beam parameters. The final performance is computed for the full Beam Delivery System including the new diagnostics section. A comparison to previous designs is also presented.
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| TUPC008 | Beam Diagnostics with IR Light Emitted by Positron at DAΦNE | diagnostics, positron, radiation, synchrotron | 1056 | ||
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Real-time beam diagnostics is mandatory in accelerators and represents one of the most challenging issues of modern storage rings and future FEL's. Recently, compact mid-IR fast uncooled photo-detectors have been used at DAΦNE to monitor single e- bunches using the SINBAD IR beamline installed on the e- ring*. Electron bunches have a FWHM of 150-300 ps and are separated by 2.7 ns**. Detectors performances are then suitable for a compact and low cost bunch-by-bunch longitudinal diagnostic device. To improve the DAΦNE diagnostic a bending magnet SR port on the e+ ring has been set-up with a HV chamber, a gold-coated plane mirror and a ZnSe window. To collect the SR light and focus radiation on IR detectors allowing the diagnostic of e+ a compact optical system has been installed in air after the window. Here we will present the status of the apparatus, the source characteristics, the optical setup and the complete acquisition system. This IR port will allow comparison in the ns time domain between data collected on both rings, and could be also used to improve DAΦNE diagnostics, i.e., identify and characterize bunch instabilities and/or increase the current in the e+ ring.
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*M. Cestelli Guidi et al. J. Opt. Soc. Amer. A 22, 2810 (2005). |
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| TUPC031 | Longitudinal Beam Diagnostics Application of Synchrotron Radiation at FLASH | radiation, synchrotron, electron, monitoring | 1116 | ||
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For the operation of the FLASH free electron laser at DESY, Hamburg, tools to measure the longitudinal charge distribution and especially its stability over time are important for efficient machine running. Several techniques using both coherent far-infrared and incoherent visible synchrotron radiation from the two bunch compressor chicanes are summarized and compared in this paper. The experimental setups used are |
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| TUPC054 | Pulse-by-pulse Photon Beam Monitor with Microstripline Structure in NSRRC | photon, storage-ring, synchrotron, impedance | 1176 | ||
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In order to diagnostic pulse-by-pulse beam movement of photon beam, NSRRC(Taiwan) and SPring-8 (Japan) have worked together to develop a front end beam monitor with microstripline structure, which is designed to have specific impedance of 50 ohm. The detector head is composed of a metal line (copper), ceramic plates (aluminum nitride) and a cooling base (copper tungsten). The metal line functions as a photocathode. The metal line is directly connected to SMA feed-through connectors to have fast response time. The detector head has been fabricated in SPring-8, and mounted on the monitor chamber and installed in NSRRC Superconducting Wiggler (SW) front end. The beam monitor can be used to examine not only pulse-by-pulse photon beam, but also the storage ring intensity and the pulse timing. Unique feature of the monitor is to produce unipolar short pulses. The design, fabrication and the measurement will be presented in this paper.
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| TUPC086 | Pinhole Camera Resolution and Emittance Measurement | emittance, synchrotron, coupling, radiation | 1254 | ||
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Third generation synchrotron light source are characterised by a low emittance and a low emittance coupling. Some light sources are already proposing to operate with extremely low coupling close to 0.1% and thus vertical emittance approaching 1pm. We derive the limits for the emittance coupling measurement due to the resolution of the X-ray pinhole camera. We also show that it is possible to design a pinhole camera in order to push the limit resolution beyond 0.1% emittance coupling. We then illustrate our calculations with the example of Diamond and compare them with experimental data.
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| TUPC127 | Utility Design for the 3GeV TPS Electron Storage Ring | storage-ring, synchrotron, booster, controls | 1365 | ||
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Having been running the Taiwan Light Source (TLS) for fourteen years since its opening in 1993, National Synchrotron Radiation Research Center (NSRRC), Taiwan, has been approved to build a photon source (TPS) last year. TPS is preliminarily designed with 3.0 GeV in energy, 518.4m in circumference and 24 Double-Bend Achromat (DBA). The utility system, including the electrical power, cooling water and air conditioning system of the TPS were designed to meet requirements of high reliability and stability. Because the power consumption of the TPS is estimated about three times that of TLS, energy saving is another consideration. This paper therefore discusses utility design concepts and presents partial design results, including capacity requirements, equipment and piping layouts.
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| TUPC132 | The Strategy between Optimal Control and Energy Saving about Utility System Operation | controls, synchrotron, radiation, simulation | 1380 | ||
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Previously, the Taiwan Light Source (TLS) at NSRRC has proven the good beam line quality depend on the utility system stability. Subsequently, several studies including the temperature control of cooling water and air conditioner was in progress for improving the system stability. Due to the importance of energy saving issue, the heavy power consumption of utility system are also discussed and intended to reduce extensively. The paper addresses some experience between optimal control and energy saving about operation of utility system in TLS. This provides a strategy between stability control and power reduction, including the flow balance, inverter usage, facility operation, control philosophy and so on.
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| TUPD028 | How to Stably Store Electron Beam in a Synchrotron Radiation Facility from the Point of View of an RF System Design | storage-ring, klystron, synchrotron, electron | 1485 | ||
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In any synchrotron radiation facilities, the users wish that electron beams are stably stored without beam abortion for as long as possible. It must be recognized that RF system is a main cause of beam abortions. In order to store beam stably, it is necessary for staffs in charge of RF system to foresee various beam instabilities and to take measures. Before discussing coupled-bunch instability problems, one should understand some trivial issues such as ion trapping and fundamental acceleration frequency modulated by high voltage ripple. The former causes transverse mode instability and the latter shakes stored electron beam longitudinally in RF cavities. In newly designed synchrotron radiation facilities, those issues mentioned above should be suppressed before beam commissioning. As for other issues relating with RF system, we would like to state the importance of a water-cooling system with stable temperature for cavities, and the electric earth problem of low level RF system and high voltage power equipment of a klystron. We describe how we have managed those issues in designing of SPring-8 RF system of the storage ring.
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| TUPP039 | Wake-field Compensation in Energy Recovery Linacs | linac, acceleration, radiation, synchrotron | 1628 | ||
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Problems created by the correlated energy spread that wake fields can produce are strongly enhanced in Energy Recovery Linacs (ERLs), as compared to conventional linacs. This is due to the fact that in ERLs the spent beam is decelerated by a potentially large factor, which increases the relative energy spread proportionally. We show how severe this problem is for the impedance budget of the x-ray ERL that Cornell plans to build, and we analyze several different possibilities to compensate the correlated energy spread involving de-phasing linac components, linear and nonlinear time-of-flight terms in different accelerator sections, or high frequency accelerating cavities. Because of the particular design, which has a turn-around loop between two sections of the linac, there are many options for these techniques which we compare and evaluate.
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| TUPP041 | CSR Shielding in the Beam Dynamics Code BMAD | radiation, shielding, synchrotron, simulation | 1634 | ||
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Short bunches radiate coherently at wavelengths that are longer than their bunch length. This radiation can catch up with the bunch in bends and the electromagnetic fields can become large enough to significantly damage longitudinal and transverse bunch properties. This is relevant for many accelerators that relies on bunch compression. It is also important for Energy Recovery Linacs, where spent beams are decelerated by a potentially large factor. Because this deceleration increases the relative energy spread, all sources of wake fields, especially Coherent Synchrotron Radiation (CSR), become much more important. In this paper we show how the beam dynamics code BMAD computes the effect of CSR and how the shielding effect of vacuum chambers is included by the method of image charges. We compare the results to established codes: to Elegant for cases without shielding and to a numerical solution of simplified Maxwell equations as well as to analytical csr-wake formulas. Good agreement is generally found, and in cases where numerical solutions of the simplified Maxwell equations do not agree with the csr-wake formulas, we show that BMAD agrees with these analytic formulas.
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| TUPP054 | A Model of an Electrical Discharge in the Flange Contacts with Omega Seals at High Currents in PEP-II | radiation, vacuum, resonance, synchrotron | 1667 | ||
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During operation with high currents at HER (High Energy Ring), high temperature elevation was found at almost every location of the vacuum chamber flange contacts. Omega RF seals were strongly damaged or even evaporated by sparks and electrical discharge. We suggest a physical model, which may explain this effect.
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| TUPP055 | Loss Factor of the PEP-II Rings | radiation, synchrotron, resonance, luminosity | 1670 | ||
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RF power balance method is used to measure the synchrotron radiation losses and the wake field losses. We present the history of the loss factor during the last several runs, which reveals many interesting correlations with vacuum chamber improvement and processing.
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| TUPP162 | High Heat Load Components in TPS Front Ends | synchrotron, undulator, radiation, photon | 1890 | ||
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National Synchrotron Radiation Research Center (NSRRC) will build a new synchrotron accelerator (TPS, Taiwan Photon Source) with a great heat-load power. Various IDs have been proposed. For instance, at 3.3 GeV, 350 mA, superconductivity wiggler SW4.8 may generate 5.8mrad wide, 57 kW/mrad2 power whereas undulator CU1.8 will be 0.7 mrad, 148 kW/mrad2. The function of the fixed mask in TPS front ends not only to protect the downstream vacuum from being hit by the radiation during miss-steering, but also shadow the unwanted power. More than one fixed masks are introduced in some high heat load front ends. High conductivity, high thermomechaical strength GlidCop® is used; design and thermomechanical analysis is also presented in this paper.
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| WEPC027 | Coherent THz Radiation at ELETTRA | radiation, electron, synchrotron, single-bunch | 2043 | ||
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Coherent infra red radiation (CIR) has been observed since some time at ELETTRA under several machine parameter settings in the beam-line SISSI. Effort has been made to produce a “stable” THz signal for experimental use. The description of the machine settings to that end and the measurements performed are presented and discussed.
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| WEPC033 | Coherent Synchrotron Radiation at the Metrology Light Source of the PTB | radiation, electron, synchrotron, storage-ring | 2058 | ||
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The Physikalisch-Technische Bundesanstalt (PTB), the German national metrology institute, has set up a low-energy electron storage ring in Berlin-Adlershof in close cooperation with the BESSY GmbH. The new storage ring, named Metrology Light Source (MLS), is mainly dedicated to metrology and technological developments in the EUV, VUV, and IR spectral range. Additionally, the MLS is the first machine designed and prepared for a special machine optics mode (low-alpha operation mode) based on an octupole correction scheme, for the production of coherent synchrotron radiation in the FIR and THz region. Two beamlines dedicated to the use of IR synchrotron radiation are now under commissioning: an IR bending magnet beamline optimized for the MIR to FIR and an IR edge radiation beamline. We report the status of the MLS operated in the low alpha mode and present first results from the commissioning.
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| WEPC046 | Characterizing THz Coherent Synchrotron Radiation at the ANKA Storage Ring | radiation, synchrotron, single-bunch, storage-ring | 2091 | ||
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In a synchrotron radiation source coherent infrared (IR) 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 in a dedicated low-alpha optics. Different bunch lengths, corresponding to different spectral ranges of the THz spectrum and various electron beam energies can be offered, depending on user demand. The radiation emitted in the fringe field of a dipole magnet, the so-called edge radiation, is detected at the ANKA-IR beamline. This paper presents radiation properties like THz beam profiles and power measurements in the framework of characterising the coherent THz radiation to optimise the power, frequency and spatial output of the ANKA storage ring. First experiments showed a time averaged power of up to 0.2 mW suggesting a THz pulse peak power of at least several tens of mW.
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| WEPC047 | Modeling the Shape of Coherent THz Pulses Emitted by Short Bunches in an Electron Storage Ring | radiation, synchrotron, storage-ring, electron | 2094 | ||
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A sufficiently short electron bunch will emit coherent synchrotron radiation of wavelengths equal to or larger than the bunch length. The shape of the emitted THz pulse depends amongst other things on the original shape and length of the bunch’s charge distribution. A Michelson interferogram of the THz signal therefore contains information on the generating bunch. However, systematic effects make a bunch length measurement based on that technique non-trivial. In order to understand the variables involved, an analytical model of the pulse generation is needed. In this paper, a derivation of the THz pulse shape form first principles with special emphasis in the time domain is presented. The impact of charge distribution parameters on the Michelson interferogram is discussed.
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| WEPC058 | Operational Performance of the Taiwan Light Source | photon, feedback, injection, synchrotron | 2124 | ||
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The Taiwan light source (TLS) is a 1.5 GeV third generation light source at the National Synchrotron Radiation Research Center (NSRRC) in Taiwan. It has been routinely operated since its opening in 1993. Several major machine upgrade projects have been undertaken and successfully completed in last 5 years, including implementing of digital bunch-by-bunch feedbacks, superconducting accelerating RF cavity, top-up mode injection, etc. The light source now moves forward to its era of mature operation. It delivers more than 5000 hours user time in 2007 with an up-time of more than 98% and a mean time between failures better than 80 hours. Here, we review its annual operational performance with detailed statistics and discuss the possible improvement directions of machine performance.
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| WEPC063 | The Concept of Hefei Advanced Light Source (HALS) | emittance, radiation, storage-ring, synchrotron | 2136 | ||
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The Hefei Light Source is a dedicated VUV and soft X-ray light source. The layout of magnet lattice limits the achievalbe beam emittance and available straight section for insertion device. To enhance competitiveness of National Synchrotron Radiation Laboratory in synchrotron radiation application research region, a concept of new dedicated VUV and soft X-ray synchrotron radiation light source was put forward, which is named Hefei Advanced Light Source. Comparing the advantages, difficulties and performance/foundation of energy recovery linac, linac-based free electron laser and storage ring based light source, the scheme of a 1.5GeV storage ring with very low beam emittance was adopted as the baseline design. At same time, a low emittance 1.5 GeV linac would be as its full-energy injector, which can provide ultra-short radiation pulse. The HALS would provide more brilliant and transverse coherent synchrotron radiation in the VUV and soft X-ray range to various users.
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| WEPC064 | The Possibility of Conversion of Hefei Light Source Storage Ring Into a Dedicated THz Radiation Source | radiation, synchrotron, storage-ring, collective-effects | 2139 | ||
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In the future of National Synchrotron Radiation Laboratory, a new advanced VUV and soft X-ray light source would be contructed and provide synchrotron radiation with high brilliance and transverse coherence. At that time, the current HLS storage ring would be replaced by the new one. Instead of retire of the old ring, there is another case, that is upgrading current low energy storage ring as a dedicated THz light source. In this paper, the possibility of lattice upgrading were evaluated. And its performance was estimated according to exist theoretical model.
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| WEPC076 | Remote Tilt-control System of Injection Bump Magnet in the SPring-8 Storage Ring | injection, synchrotron, coupling, radiation | 2172 | ||
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The SPring-8 storage ring has four pulse-bump magnets to generate bump orbit for beam injection. Rotational error of the bump magnets around a beam-axis (tilt) induces the stored-beam oscillation in vertical direction due to horizontal error field. In the top-up operation, vertical perturbation of the stored-beam during beam injection is mainly produced by the tilt. We evaluated the tilt angle by measuring of the perturbation turn-by-turn using a single-pass BPM system and realigned bump magnets manually inside the accelerator tunnel. It was required to repeat the measurement and realignment processes two or three times for convergence. To correct the tilts smoothly, we developed a remote tilt-control system. The system consists of two fixed and one movable supports in vertical direction under each bump magnets. The movable support is driven by a stepper motor through 1/30 worm gear in the range of ±4 mrad with the accuracy of less than 0.1 mrad. By using this system, we succeeded complete on-beam reduction of the perturbation.
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| WEPC113 | Heat Load Issues of Superconducting Undulator Operated at TPS Storage Ring | radiation, undulator, storage-ring, synchrotron | 2267 | ||
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The superconducting undulator with periodic length of 1.5 cm and magnet gap of 5.6 mm has been studied. The magnetic flux density of 1.4 T has been achieved. However, the heat loads from image current of the electron in the storage ring and the synchrotron radiation from bending magnet are the critical issues. The calculated power from the image current and the synchrotron radiation of bending magnet are about 3.5 W/m and 1.7 W, respectively. The superconducting undulator will be operated at the 3 GeV TPS storage ring that the operation current and the magnet flux density of dipole magnet is 400 mA and 1.19 T, respectively. The superconducting RF cavity will be installed in the TPS such that the bunch length is only 2.8 mm. Hence, the superconducting Landau cavity is necessary to extend the bunch length for reducing the heat load on the beam duct. In addition, some strategies are needed to be studied to avoid the synchrotron radiation heating on the 4.2 K vacuum chamber. The soft-end dipole design and the chicane mechanism are studied to solve the issue herein.
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| WEPC114 | Improved Winding of Superconducting Undulator and Measurement of Quenching Tolerance | radiation, undulator, synchrotron, storage-ring | 2270 | ||
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The superconducting (SC) wire windings of the mini-pole superconducting undulator at National Synchrotron Radiation Research Center (NSRRC) have an improved performance. A precise measurement of the magnetic field was undertaken to examine the quality of the wire winding. We improved the insulation between wires and the iron pole to avoid SC wire degradation when the coil was trained up to high current. A Teflon coating (layer thickness 0.035-0.045 mm) on the iron pole is capable of providing insulation to 0.5 kV. We pasted extra Teflon tape (thickness 0.12 mm) on the coating layer; this Teflon tape serves as a buffer that avoids the SC wires scraping the Teflon coating layer during adjustment of the position of the SC wire during winding. A quenching experiment was also performed to detect the heat tolerance of the SC wires during extra heating of the beam duct; a heating tape (Ni80Cr20) simulated the heating of the beam duct by synchrotron radiation. The SC wires and heater are separated by the stainless steel (SS) beam duct (thickness 0.3 mm) and an epoxy layer (thickness 0.1 mm). This result is an important issue in cryostat design.
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| WEPC128 | SPUR: A New Code for the Calculation of Synchrotron Radiation from Very Long Undulator Systems | undulator, radiation, electron, synchrotron | 2305 | ||
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The accurate calculation of synchrotron radiation from an undulator is a common problem and numerous codes have been developed that describe analytic and measured fields. However, for very long undulator systems, comprising of many individual modules and total lengths in excess of 100s of meters, for example as found in the LCLS, X-FEL, the ILC positron source undulator systems, there is not a suitable code that can handle the amount of data in a convenient manner and which runs in a practically realisable time limit. The development of a new code, SPontaneous Undulator Radiation, SPUR, is presented which computes the spontaneous radiation from electron beams passing through a system of undulators. The code supports parallel architecture, and uses the HDF5 technology to efficiently handle the multi-dimensional data. The latest results developments and benchmarking are presented.
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| WEPC152 | Magnet Block Optimization of the APPLE-II Elliptically Polarized Undulator | polarization, undulator, radiation, synchrotron | 2362 | ||
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The uniform field region of elliptically polarized undulator (EPU) of APPLE-II type is very short especially in the horizonta axis. The magnet block arrangements with a approximately parabolic pole face or of APPLE-II undulator can enlarge the horizontal field roll-off and shorten the vertical field roll-off. We studied the dfferent shapes to expect a optimizaed horizotal and vertical field roll-off.
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| WEPP001 | Energy Loss of Coasting Gold Ions and Deutrons in RHIC | synchrotron, radiation, ion, impedance | 2518 | ||
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The total energy loss of coasting gold ion beams was measured at RHIC at two energies, corresponding to a gamma of 75.2 and 107.4. We describe the experiment and observations and compare the measured total energy loss with expectations from ionization losses at the residual gas, the energy loss due to impedance and synchrotron radiation. We find that the measured energy losses are below what is expected from free space synchrotron radiation. We believe that this shows evidence for suppression of synchrotron radiation which is cut off at long wavelength by the presence of the conducting beam pipe.
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| WEPP158 | Simulation of beam Halo in CLIC Collimation Systems | simulation, collimation, synchrotron, radiation | 2859 | ||
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Full simulation of the CLIC and ILC collimation systems are performed to take account of collimator wakefield effects from the core beam on the halo. In addition full simulation of the interaction of the halo with the collimator material is performed to study the effect of multiple scattering and also the production of neutrons in the electromagnetic showers. The effect of beam-gas scattering downstream of the collimators is also included.
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| THPC044 | Accurate Calculation of Higher Order Momentum Compaction Factor in a Small Ring | storage-ring, sextupole, radiation, synchrotron | 3074 | ||
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The key issues to obtain short beam bunch in storage ring is to lowering momentum compaction factor. When the linear momentum compaction factor is small, higher order momentum compaction factor can produce significant effects in the longitudinal beam dynamics. In the small storage ring, higher order momentum comaction factor is determined not only by sextupoles, and also by the fringe field of main magnets. In this paper, the higher order momentum factor formula including the effects of fringe field is deduced. As a example, the momentum compaction factor of HLS storage ring was calculated.
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| THPC058 | High Order Super-periodic Structural Resonances | resonance, lattice, storage-ring, synchrotron | 3116 | ||
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High order super-periodic structural resonances, which arise from the study of SSRF lattice optimization, are found to have large effects on beam dynamics. The mechanism and feature of this kind of resonances are described in the text. The limit to beam dynamics of other light sources are also found from these resonances.
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| THPP139 | Stainless Steel Vacuum Chambers for the SSRF Storage Ring | vacuum, storage-ring, synchrotron, radiation | 3688 | ||
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Stainless steel 316LN plate was adopted as main material for SSRF storage ring vacuum chambers and ante-chamber structure was used just as other 3rd light source. The analysis for the deformation of the chambers under atmospheric pressure and the thermal situation under synchrotron radiation were done with ANASYS program. Many problems on the structure design and fabrication technique were revealed and suitable solving methods were found in the process of development and manufacture of nine chamber prototypes. Deep draw die was used to form the chambers’ figuration. Wire cutting and CNC machining were used to manufacture the main components. The flatness tolerance, straightness tolerance and the deformation of the chambers under atmospheric pressure were all less than 1mm. After annealed in the vacuum furnace at 850℃, the magnetic permeability of welding seal was reduced from 2.5 to 1.02, the residual stress was deleted, and the vacuum performance was improved. Now SSRF vacuum system is being operated very well. The average pressure without beam is about 2.5×10-8 Pa and the average pressure with beam of 3GeV/100mA is about 8×10-7 Pa.
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