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| TUPMA014 | State of the SLS Multi-bunch Feedback | feedback, synchrotron, injection, storage-ring | 118 | ||||
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In order to control coupled bunch oscillations in the SLS storage ring, feedback systems for all three planes were forseen. The filters are realized as fully digital bunch by bunch systems. With the development of dedicated Analog to Digital and Digital to Analog Converter boards, the feedbacks could be commissioned. Important parts of the computations for the transverse planes could be implemented into the ADC FPGA, making the DSPs originally planned to be used obsolete and allowing for an extremely low latency time of 200 ns. The systems give a larger freedom in the choice of the beam optics and also lead to a better closure of the injection bump during top up mode.
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| TUPMA016 | Computation of Wakefields and Impedances for the PETRA III Longitudinal Feedback Cavity | feedback, impedance, simulation, scattering | 124 | ||||
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At DESY the existing PETRA II storage ring will be converted into a 3rd generation synchrotron radiation source, called PETRA III. The total beam current is limited by coupled bunch instabilities, which are mainly driven by the parasitic modes of the RF cavities. It is planned to use longitudinal and transverse feedback systems to achieve the design current of 100 mA. Eight single cell feedback cavities will be installed into the PETRA III ring to damp the coupled bunch longitudinal phase oscillations. It is important to know the contribution of the feedback cavity to the impedance budget of PETRA III. In this article, the wake and impedance computation results, using the loss and kick parameters, will be reported. The computer codes MAFIA and Microwave Studio have been used to compute the electromagnetic fields.
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| TUPMA053 | Injection Optimisation for INDUS-2 | injection, optics, septum, synchrotron | 184 | ||||
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In this paper commissioning experience of injection into INDUS-2, a 2.5 GeV synchrotron radiation source is discussed. In initial stage of commissioning, partial beam loss was observed. In this context effect of various injection errors such as mismatch between pulse widths, jitter and magnetic field stability of kickers on injected and stored beam are studied1. A brief summary of the results is presented. After reducing jitter and fine adjustments of timings of kicker power supplies, partial beam loss reduced significantly.
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| WEC3H101 | Multi-bunch Feedback Activities at Photon Factory Advanced Ring | feedback, injection, betatron, controls | 330 | ||||
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The photon factory advanced ring (PF-AR) is a dedicated single bunch light source at KEK, however, some users require multi-bunch operation for high intensity x-ray beams. The old transverse damping system can suppress only one (or two) bunches, while new multi-bunch feedback system has been successfully tested to a maximum of 64 bunches. Both analog and digital transverse feedback loop has been tested at AR to store multi-bunches. Long cables are used to delay the bunch position error signal from BPM buttons for analog feedback control loop. Betatron phase advance between stripline kicker and BPM are selected to be around 90 deg. For digital feedback loop, it based on a FPGA test board. Bunch position error signal sampled by ADC, filtered by 10-tap FIR filter implemented in FPGA and send to DAC output for correction. FIR filter is well designed to increase the system dynamic range. Digital delay can also be implemented inside FPGA instead of long cable delays. Maximum beam current of 97mA has been achieved for several bunches’ storage, betatron oscillation of the stored beam can be suppressed well.
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| WEPMA037 | Beam Coupling Impedance Studies of the CSNS Ring | impedance, coupling, space-charge, extraction | 372 | ||||
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The China Spallation Neutron Source (CSNS) is a high intensity proton accelerator with an injection energy of 80 MeV. The knowledge of impedance in the vacuum chamber is necessary for optimizing the accelerator performance. In this paper, the longitudinal and transverse coupling impedances of the CSNS Rapid Cycling Synchrotron (RCS) are estimated.
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| WEPMA049 | Design of a Stripline Kicker for Tune Measurement in SESAME Storage Ring | storage-ring, impedance, betatron, synchrotron | 390 | ||||
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Traveling wave electrodes are commonly used in synchrtorn light sources as a tool for both excitation and beam sensing for tune measurement. Noraml longitudinally symmetric stripline has a posivie sine wave response in the frequency domain. An exponentially taperd stripline has a constant coupling impedance versus frequency and better frequency response. In this paper the design of stripline kicker for the purpose of tune measurement in the SESAME storage ring is reported.
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| WEPMA058 | Tune and Lifetime Studies at the Australian Synchrotron | quadrupole, sextupole, synchrotron, injection | 401 | ||||
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The 3GeV Australian Synchrotron will begin operation in March 2007. This paper outlines the tune and lifetime measurement systems. It also provides a summary of a number of studies completed using these systems. Three different tune measurement systems have been tested. Lifetime measurements made using the DCCT were used to optimise the strengths of the harmonic sextupoles and the location of the tunes. The vertical aperture was determined using scrapers. Beta-function measurements have been completed by shunting individual quadrupoles and noting the resultant tune changes. Chromaticity measurements have been made by observing the change in tune as the RF frequency is varied.
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| WEPMA070 | Control of the Multi-Bunch Instabilities at TLS | feedback, controls, synchrotron, synchrotron-radiation | 419 | ||||
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To increase stored beam current and provide stable beam for users, RF is upgraded to superconducting and top-up mode injection is operated recently at the TLS. To take advantage of these upgrade, suppress multi-bunch instabilities due to resistive wall of the vacuum chamber, cavity-like structures and ions related instability are essential. FPGA based transverse bunch-by-bunch feedback system and longitudinal feedback system was deployed. Multi-bunch instabilities was successfully suppressed when stored beam current is more than 400 mA. Lower chromaticity operation is possible with the help of transverse feedback system that is essential for injection efficiency improvement in top-up operation mode. Status of the feedback systems and analysis of the behavior of multi-bunch instability will be presented.
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| THYMA01 | Kickers for Injection and Extraction in Damping, Combiner and Storage Rings | injection, impedance, extraction, damping | 539 | ||||
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Injection and extraction kickers play a fundamental role in all the projects of new major accelerators at present under study. The feasibility of these accelerators depends also on the possibility to realize kickers based on unconventional design and new technologies. This paper describes the R&D carried out at LNF on two different types of deflecting devices. The first are the kickers for the Damping Ring (DR) of the International Linear Collider (ILC) and the Storage Rings (SR) of colliders like DAFNE. They require very low impedance, good field uniformity in a wide region around the beam axis and very short pulse duration for limiting the length and consequently the cost of the DR and for reducing the perturbation of the stored bunches in SRs. The tests made on stripline prototypes, fast high voltage pulsers and vacuum feedthroughs are presented. The second are the RF kickers for the CLIC Test Facility 3 (CTF3) for which an original SW structure has been designed and realized for the Delay Loop (DL) while a more conventional TW deflector allows the multiplication of bunch current and frequency in the Combiner Ring (CR). Results of their performances are described.
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| THPMA013 | Effect of Eddy Current in Magnetic Lamination on Pulsed Septum Magnet Response | septum, injection, storage-ring, vacuum | 643 | ||||
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Indus-2 Pulsed septum magnets have been developed using 0.1 mm thick Ni-Fe laminations, which were electrically insulated from each other. These laminations were annealed in Hydrogen furnace & then oxidized in a Air controlled furnace. A process has been optimized to get 10-micron oxidization thickness on both sides of lamination. A pulse test set up has been built to characterize the laminations at high magnetization rates (‘~ 1 T/us). Electromagnetic simulation of the main field in the gap & field free region ' leakage/stray field for Septum magnets were performed using Flux 2D. A stray field (~1G-m) was stringent so as not to distort circulating beam. Magnetic screen has been optimized to minimize the stray fields. A pulsed thin & thick septum magnets were excited using 50 ms half sine wave, the field homogeneity in the order of 100 PPM & Integrated stray field 0.7 G-m has been obtained. This paper focus on Eddy current effect in lamination on pulse magnetic response, attenuation, phase shift & resonance in lamination due to pulse frequency. Modeling of magnetic circuit, shielding of septum & pulse response of NiFe lamination at high magnetic amplitudes(1.2T ) is also presented.
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R. K. Mishra, P. Pareek, M. M.Pandey, V. Gaud, S. Senthil kumar |
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| THPMA078 | Wideband Current Transformers for the Surveillance of the Beam Extraction Kicker System of the Large Hadron Collider | extraction, collider, beam-losses, shielding | 746 | ||||
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The LHC beam dumping system must protect the LHC machine from damage by reliably and safely extracting and absorbing the circulating beams when requested. Two sets of 15 extraction kicker magnets form the main active part of this system. A separate high voltage pulse generator powers each magnet. Because many failures are deemed catastrophic, the magnets and generators are continuously surveyed in order to generate a failsafe beam abort as soon as an internal fault is detected. Amongst these surveillance systems, wideband current transformers have been designed to detect any erratic starts in one of the generators. The current transformers were developed in collaboration with industry. To minimize losses, high-resistivity cobalt alloy was chosen for the cores. The annealing techniques originally developed for LEP beam current measurement in collaboration between CERN and industry allowed to extend the frequency response beyond that of traditional core materials. The paper shows the results obtained, exposes the problems encountered with shielding, conductor position sensitivity, load resistor technology and their solutions.
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| FRXMA03 | Achievement of ATF and its Future Plans | damping, emittance, coupling, extraction | 837 | ||||
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The ATF (Accelerator Test Facility at KEK) International collaboration has been launched formally under the MoU (Memorandum of Understanding) from August 1, 2005, so as to maximally contribute to the world design and development efforts in the areas of particle sources, damping rings, beam focusing and beam instrumentation towards the International Linear Collider (ILC) project. I will give a talk on the recent achievement at ATF and its future plans, especially ATF2 project.
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