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| THB001 |
Beam-based Feedback for the Linac Coherent Light Source
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644 |
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- D. Fairley, S. Allison, S. Chevtsov, P. Chu, F.-J. Decker, P. Emma, J. C. Frisch, T. M. Himel, K. H. Kim, P. Krejcik, T. E. Lahey, H. Loos, P. Natampalli, S. Peng, D. Rogind, H. Shoaee, T. Straumann, G. R. White, E. Williams, J. Wu, S. Zelazny
SLAC, Menlo Park, California
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Funding: Work supported in part by the DOE Contract DE-AC02-76SF00515. This work was performed in support of the LCLS project at SLAC.
Beam-based feedback control loops are required by the Linac Coherent Light Source (LCLS) program in order to provide fast, single-pulse stabilization of beam parameters. Eight transverse feedback loops, a 6x6 longitudinal feedback loop, and a loop to maintain the electron bunch charge were successfully prototyped in MATLAB for the LCLS, and have been maintaining stability of the LCLS electron beam at beam rates up to 30Hz. In the final commissioning phase of LCLS the beam will be operating at up to 120Hz. In order to run the feedback loops at beam rate, the feedback loops will be implemented in EPICS IOCs with a dedicated ethernet multi-cast network. This paper will discuss the design of the beam-based Fast Feedback System for LCLS. Topics include MATLAB feedback prototyping, algorithm for 120Hz feedback, network design for fast data transport, actuator and sensor design for single-pulse control and sensor readback, and feedback configuration and runtime control.
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| THB002 |
Stabilization of Beam Extraction Timing in J-PARC RCS
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647 |
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- F. Tamura
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
- M. Yoshii
KEK/JAEA, Ibaraki-Ken
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The extracted beams from the rapid cycling synchrotron (RCS) of J-PARC are delivered to the Materials and Life Science Facility (MLF) and the MR. The repetition rate of the RCS is 25 Hz and four beam pulses are for the MR and the other 87 pulses are for the MLF. Stable beam timings are required for both of the destinations. In case of the MLF, the beam has to be synchronized to the Fermi chopper, which has a tolerance of a few 100 ns. In case of the MR, the beam must be injected to the proper RF bucket with a precise phase. To realize the stable beam timing, we employ the non AC-line synchronized timing system. Also the magnetic-alloy accelerating cavities and the full digital low-level RF control system are the keys for the precise beam phase control. We present the preliminary results of the beam stability measurement.
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Slides
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| THB003 |
Diamond Light Source Electron Beam Position Feedback: Design, Realization and Performance
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650 |
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- M. T. Heron, M. G. Abbott, J. A. Dobbing, G. Rehm, J. Rowland, I. Uzun
Diamond, Oxfordshire
- S. Duncan
University of Oxford, Oxford
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The electron beam in the Diamond Synchrotron Light Source is stabilised in two planes using the Fast Orbit Feedback system. This feedback system takes the beam position from 168 Libera electron beam position monitors, for both planes, and calculates offsets to 336 corrector power supplies at a sample rate of ~10 kHz. The design and realisation, together with system performance will be presented, and possible developments considered.
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| THB004 |
New Fast Orbit Feedback Architecture Based on Libera Brilliance Devices for the ESRF Storage Ring
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653 |
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- J. M. Koch, F. Epaud, G. Gautier, E. Plouviez, F. Uberto
ESRF, Grenoble
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In the frame of the upgrade of the ESRF, one important implementation regarding the source will be to improve the stability of the beam in the whole frequency range at which mechanical vibrations or electro-magnetic disturbances take place. The improvement of the existing orbit correction scheme based on separate slow and fast systems* will be achieved both by taking advantage of smart measurement thanks to the newly installed Libera Brilliance and by using more correctors than today. This new Fast Orbit Feedback will therefore rely only on the 96 correctors integrated inside the sextupole magnets to cover the full frequency range all around the ring. Following the successful implementation of such a scheme at the Swiss Light Source and, more recently, at Diamond Light Source, re-using as much as possible pieces of software and ideas on hardware both from DLS and from Soleil, we have defined the architecture for the ESRF scheme that will be developed in this paper.
* DIPAC 2009 ID: 1208 - TUPD05 Eric Plouviez (ESRF, Grenoble) Improvement of the Fast Orbit Correction on the ESRF Storage Ring
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| THB005 |
Primary and Secondary Beam Stabilization at the ELBE Accelerator Facility
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656 |
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- M. Justus, R. Jainsch, T. Kirschke, U. Lehnert, P. Michel, W. Seidel
FZD, Dresden
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Since 2003, ELBE operates as a user facility for fundamental research and life sciences, providing highly brilliant electromagnetic radiation in a broad spectral range, as well as particle beams. The driving source is a 40 MeV, 1 mA electron LINAC in c.w. mode, utilizing a 13 MHz pulsed thermionic gun and Tesla acceleration technology. Infrared light from two FELs between 3 and 280μm is the foremost secondary radiation used at ELBE. For its applications, different demands in power and wavelength stability are crucial for successful experiments. Therefore, a feedback system for the electron beam position and energy in combination with IR beam intensity feedback using FPGA technology is under development. It allows suppression of beam instabilities caused by thermal behaviour, microphonics and the 50 Hz mains frequency with harmonics. This contribution depicts hardware and software details of the measurement and feedback system and provides performance results as well.
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| THB006 |
New Automatic Bunch Current Sensitive Fast Attenuator for RF Front-end of Bunch-by-Bunch Feedback System at SPring-8
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659 |
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- K. Kobayashi, T. Nakamura
JASRI/SPring-8, Hyogo-ken
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We currently developing a new bunch current sensitive automatic attenuation system for the RF front-end of the bunch-by-bunch feedback system in the SPring-8 storage ring. It controls the attenuation of high current bunch signal to avoid the saturation of RF front-end and for equalization of the feedback gain for hybrid beam filling modes consist of few-mA singlet bunches and sub-mA bunch trains. We have already developed and installed a bunch current sensitive automatic attenuator with a simple mixer, a discriminator and FPGA based 1-turn delay with the attenuation level of 15 dB. However this attenuation level is not enough for hybrid filling modes with higher bunch current singlets and lower bunch current trains which are recently requested by users. To achieve more attenuation level and more flexible operation, we are now developing an attenuation system with a voltage variable attenuator controlled by a digital bunch current measurement device which is converted from a SPring-8 bunch-by-bunch feedback processor. This paper describes the new attenuation system and its test results.
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