Author: Rehm, G.
Paper Title Page
MOPGF097 Architecture of Transverse Multi-Bunch Feedback Processor at Diamond 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 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 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 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]