Keyword: feedback
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MOC3O03 Automatic FEL Optimization at FERMI FEL, laser, electron, undulator 1
  • G. Gaio, M. Lonza
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  FERMI is a seeded Free Electron Laser (FEL) located in Trieste, Italy. The machine setup and optimization is a non-trivial problem due to the high sensitivity of the FEL process to several machine parameters. In particular, the electron bunch trajectory and its spatial overlap with the seed laser beam represent one of the key aspects to optimize and then preserve during machine operation. In order to ease the FEL tuning and to guarantee a long term stability of the photon beam, a software process integrated into the feedback systems performs automatic trajectory optimization of both the seed laser and the electron beams. The algorithm implementation, the results and the operational issues are presented.  
slides icon Slides MOC3O03 [8.957 MB]  
MOC3O04 System Identification and Robust Control for the LNLS UVX Fast Orbit Feedback controls, network, vacuum, power-supply 1
  • D.O. Tavares
    LNLS, Campinas, Brazil
  • D.R. Grossi
    Sao Paulo University, São Carlos Campus, São Carlos, Brazil
  This paper describes the optimization work carried out to improve the performance of the LNLS UVX fast orbit feedback system. Black-box system identification techniques were applied to model the dynamic behavior of BPM electronics, orbit correctors, communication networks and vacuum chamber eddy currents. Due to the heterogeneity on the dynamic responses among several units of those subsystems, as well as variations on the static response matrix due to accelerator optics changes during operation, robust control techniques were employed to achieve appropriate closed-loop performance and robustness.  
slides icon Slides MOC3O04 [3.792 MB]  
MOC3O05 NSLS-II Fast Orbit Feedback System injection, operation, storage-ring, FPGA 1
  • Y. Tian, W.X. Cheng, L.R. Dalesio, J.H. De Long, K. Ha, L. Yu
    BNL, Upton, Long Island, New York, USA
  • W.S. Levine
    UMD, College Park, Maryland, USA
  This paper presents the NSLS-II fast orbit feedback (FOFB) system, including the architecture, the algorithm and the commissioning results. A two-tier communication architecture is used to distribute the 10kHz beam position data (BPM) around the storage ring. The FOFB calculation is carried out in field programmable gate arrays (FPGA). An individual eigenmode compensation algorithm is applied to allow different eigenmodes to have different compensation parameters. The system is used as a regular tool to maintain the beam stability at NSLS-II.  
slides icon Slides MOC3O05 [10.087 MB]  
MOPGF002 Magnet Corrector Power Supply Controller for LCLS-I controls, interface, EPICS, power-supply 1
  • S. Babel, B. Lam, K. Luchini, J.J. Olsen, T. Straumann, E. Williams, C. Yee
    SLAC, Menlo Park, California, USA
  The MCOR-12[Magnet Corrector] is a 16-channel modular architecture, precision magnet driver, capable of providing bipolar output currents in the range from 12A to +12A. A single, unregulated bulk power supply provides the main DC power for the entire crate. Currently the MCORs have a 1000ppm regulation on the B-field. The MCOR controller card upgrades, existing LCLS-I and future LCLS-II needed, controls for Magnet Corrector Power Supplies. The project shifts the existing functionality of the VME based DAC and SAM and an Allen Bradley PLC into a new slot-0 card residing in the MCOR chassis. Elimination of the VME crate and the PLC will free up rack space to be used in future. The new interface card has a long term stability of 100 ppm and monitors ground fault currents and various other interlocks for the MCOR power supplies. The controller can interface to EPICS Channel Access and Fast Feedback system at SLAC using two Gigabit Ethernet ports and has an FPGA based EVR for getting 'time stamps' from the Event Generator system at SLAC. The EPICS control system along with embedded diagnostic features will allow for enhanced remote control and monitoring of the power supplies.
*S. Babel, S. Cohen, "Digital Control Interface for Bipolar Corrector Power, BiRa Systems, Albuquerque **G.E. Leyh, "A Multi-Channel Corrector Magnet Controller"
poster icon Poster MOPGF002 [1.646 MB]  
MOPGF024 Testing Framework for the LHC Beam-based Feedback System framework, software, hardware, real-time 1
  • S. Jackson, D. Alves, L. Di Giulio, K. Fuchsberger, B. Kolad, E. Pedersen
    CERN, Geneva, Switzerland
  During the first LHC shut-down period, software for the LHC Beam-based Feedback Controller (BFC) and Service Unit (BFSU) was migrated to new 64-bit multi-core hardware and to a new version of CERN's FESA3 real-time framework. This coincided with the transfer of responsibility to a new software team, charged with readying the systems for beam in 2015 as well as maintaining and improving the code-base in the future. In order to facilitate the comprehension of the system's 90'000+ existing lines of code, a new testing framework was developed which would not only serve to define the system's functional specification, but also provide acceptance tests for future releases. This paper presents how the BFC and BFSU systems were decoupled from each other as well as from the LHC plant's measurement and correction systems, thus allowing simulation-data driven instances to be deployed in a test environment. It also describes the resulting Java-based domain-specific language (DSL) which, when employed in JUnit, allows the formation of repeatable acceptance tests.  
MOPGF077 Drift Control Engines Stabilize Top-Up Operation at BESSY II controls, injection, operation, experiment 1
  • T. Birke, F. Falkenstern, R. Müller, A. Schälicke
    HZB, Berlin, Germany
  Funding: Work supported by BMBF and Land Berlin.
Full stability potential of orbit and bunch-by-bunch-feedback controlled top-up operation becomes available to the experimental users only if the remaining slow drifts of essential operational parameters are properly compensated. At the light source BESSY II these are the transversal tunes as well as the path length and energy. These compensations are realized using feedback control loops together with supervising state machines. Key to the tune control is a multi-source tune determination algorithm. For the path length correction empirical findings are utilized. All involved software systems and data-paths are sketched.
poster icon Poster MOPGF077 [2.003 MB]  
MOPGF097 Architecture of Transverse Multi-Bunch Feedback Processor at Diamond controls, FPGA, EPICS, experiment 1
  • M.G. Abbott, G. Rehm, I.S. Uzun
    DLS, Oxfordshire, United Kingdom
  We describe the detailed internal architecture of the Transverse Multi-Bunch Feedback processor used at Diamond for control of multi-bunch instabilities and measurement of betatron tunes. Bunch by bunch selectable control over feedback filters, gain and excitation allows fine control over feedback, allowing for example the single bunch in a hybrid or camshaft fill pattern to be controlled independently from the bunch train. It is also possible to excite all bunches at a single frequency while simultaneously sweeping the excitation for tune measurement of a few selected bunches. The single frequency excitation has been used for continuous measurement of the beta-function. A simple programmable event sequencer provides support for up to 7 steps of programmable sweeps and changes to feedback and excitation, allowing a variety of complex and precisely timed beam characterisation experiments including grow-damp measurements in unstable conditions and programmed bunch cleaning. Finally input and output compensation filters allow for correction of front end and amplifier phasing at higher frequencies.  
poster icon Poster MOPGF097 [0.247 MB]  
MOPGF175 A Unified Approach to the Design of Orbit Feedback with Fast and Slow Correctors controls, electron, storage-ring, simulation 1
  • S. Gayadeen, M.T. Heron, G. Rehm
    DLS, Oxfordshire, United Kingdom
  A unified control design is proposed to simultaneously determine control actions for both fast and slow arrays of correctors used for orbit feedback. By determining the interaction of the spatial subspaces of each array of correctors, spatial modes which require both fast and slow correctors can be identified. For these modes, a mid-ranging control technique is proposed to systematically allocate control action for each corrector. The mid-ranging control technique exploits the different dynamic characteristics of the correctors to ensure that the two arrays of actuators work together and avoid saturation of the fast correctors. Simulation results for the Diamond Storage Ring are presented.  
poster icon Poster MOPGF175 [0.995 MB]  
MOPGF177 Robust Stability Analysis of Orbit Feedback Controllers controls, electron 1
  • S. Gayadeen, M.T. Heron, G. Rehm
    DLS, Oxfordshire, United Kingdom
  Closed loop stability of electron orbit feedback controllers is affected by mismatches between the accelerator model and the real machine. In this paper, the small gain theorem is used to express analytical criteria for closed loop stability in the presence of spatial uncertainty. It is also demonstrated how the structure of the uncertainty models affects the conservativeness of the robust stability results. The robust stability criteria are applied to the Diamond Light Source electron orbit controller and bounds on the allowable size of spatial uncertainties which guarantee closed loop stability is determined.  
poster icon Poster MOPGF177 [1.023 MB]  
MOPGF178 Uncertainty Modelling of Response Matrix controls, electron, storage-ring, closed-orbit 1
  • S. Gayadeen, M.T. Heron, G. Rehm
    DLS, Oxfordshire, United Kingdom
  Electron orbit feedback controllers are based on the inversion of the response matrix of the storage ring and as a result, mismatches between the accelerator model and the real machine can limit controller performance or cause the controller to become unstable. In order to perform stability analysis tests of the controller, accurate uncertainty descriptions are required. In this paper, BPM scaling errors, actuator scaling errors and drifts in tune are considered as the main sources of spatial uncertainties and because most electron orbit feedback systems use Singular Value Decomposition (SVD) to decouple the inputs and outputs of the system, the uncertainty can be expressed in terms of this decomposition. However SVD does not allow the main sources of uncertainty to be decoupled so instead, a Fourier-based decomposition of the response matrix is used to decouple and model the uncertainties. In this paper, both Fourier and SVD uncertainty modelling methods are applied to the Diamond Light Source storage ring and compared.  
poster icon Poster MOPGF178 [1.465 MB]  
WEPGF089 CERN Open Hardware Experience: Upgrading the Diamond Fast Archiver hardware, FPGA, network, interface 1
  • I.S. Uzun, M.G. Abbott
    DLS, Oxfordshire, United Kingdom
  Diamond Light Source developed and integrated the Fast Archiver into its Fast Orbit Feedback communication network in 2009. It enabled synchronous capture and archive of the entire position data in real-time from all Electron Beam Position Monitors (BPMs) and X-RAY BPMs . The FA Archiver solution has also been adopted by SOLEIL and ESRF. However, the obsolescence of the existing PCI Express based FPGA board from Xilinx and continuing interest from community forced us to look for a new hardware platform while keeping the back compatibility with the existing Linux kernel driver and application software. This paper reports our experience with using the PCIe SPEC board from CERN Open Hardware initiative as the new FA Archiver platform. Implementation of the SPEC-based FA Archiver has been successfully completed and recently deployed at ALBA in Spain.  
poster icon Poster WEPGF089 [0.576 MB]  
WEPGF117 HIGH LEVEL APPLICATIONS FOR HLS-II controls, lattice, storage-ring, operation 1
  • K. Xuan, C. Li, J.Y. Li, G. Liu, J.G. Wang, L. Wang
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  The Hefei light source was overhauled beginning from 2010 and completed in the end of 2013. The new light source is renamed as HLS-II. A set of high level application tools, including physical quantity based control IOC, lattice calibration tools, orbit feedback, etc., were developed for the light source commissioning and operation. These tools have been playing important roles in the commissioning and operation of the light source. This paper reports some critical applications.  
poster icon Poster WEPGF117 [0.679 MB]  
THHA3O02 Status of the Continuous Mode Scan for Undulator Beamlines at BESSY II undulator, controls, diagnostics, EPICS 1
  • A.F. Balzer, E. Schierle, E. Suljoti, M. Witt
    HZB, Berlin, Germany
  • R. Follath
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  At the synchrotron light source BESSY II monochromator (MONO) and insertion device (ID) scans can be done synchronized in two different modes. In step mode MONO and ID move independently to intermediate target positions of an energy scan. In continuous mode (CM) MONO and ID cover the whole range of the scan nonstop in a coupled motion. Data acquisition is done continuously at the speed provided by the CM scan and is available in regular user operation. Currently CM is in operation at 11 undulator beamlines at BESSY II. 3 new beamlines requesting CM are under construction. During CM the MONO EPICS IOC acts as a controller forcing the MONO optics to follow the movement of the ID. A non-linear predictive control scheme is used to implement this dynamic coupling. The controller task utilizes polynomial regression to extrapolate the ID motion. Calculation of the trajectories for MONO grating and mirror is based on bijective gap to energy lookup tables and the grating equation. In this paper the technical implementation, limitations, recently developed diagnostic methods, and future plans for improvements are presented.  
slides icon Slides THHA3O02 [0.898 MB]