Author: Rehm, G.
Paper Title Page
MOPP032 Fast Feedback Using Electron Beam Steering to Maintain the X-Ray Beam Position at a Monochromatic X-Ray Diagnostic at Diamond Light Source 171
 
  • C. Bloomer, G. Rehm, A. Tipper
    DLS, Harwell, United Kingdom
 
  A new feedback system is being developed at Diamond Light Source, applying a modulation to the position of the electron beam to keep the synchrotron X-ray beam fixed at the sample-point. Beamline detectors operating in the 100-1000Hz regime are becoming common, and the X-ray beam stability demanded by beamlines is thus of comparable bandwidths. In this paper we present a feedback system operating at these bandwidths, using a diagnostic instrument permanently installed in the X-ray beam path to measure the error in beam position at the sample point, and fast air-cored magnets to apply a small modulation to the electron beam to compensate. Four magnets are used to generate electron beam bumps through an ID straight. This modulation of the beam away from the nominal orbit is small, less than 10 microns, but should be sufficient to compensate for the bulk of the X-ray motion observed at the sample. It is small enough that the impact on the machine will be negligible. This system aims to maintain X-ray beam stability to within 3% of a beam size, at bandwidths of up to 500Hz.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2019-MOPP032  
About • paper received ※ 09 September 2019       paper accepted ※ 10 September 2019       issue date ※ 10 November 2019  
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TUPP038 Spatial Resolution of an X-ray Pinhole Camera using a Multi-layer Monochromator 412
 
  • L. Bobb, G. Rehm
    DLS, Oxfordshire, United Kingdom
 
  X-ray pinhole cameras are widely used for beam emittance monitoring at synchrotron light sources. Due to the reduction in beam emittance expected for the many fourth generation machine upgrades, the spatial resolution of the pinhole camera must be improved accordingly. It is well known that there are many contributions to the point spread function. However, a significant contribution arises from diffraction by the pinhole aperture. Given that diffraction is dependent on the spectral distribution of the incident synchrotron radiation, the spatial resolution can be improved by using a monochromatic beam. For optimal performance, the photon energy should be matched to the pinhole aperture size. Here we investigate the spatial resolution of the pinhole camera as a function of photon energy using a multi-layer monochromator.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2019-TUPP038  
About • paper received ※ 04 September 2019       paper accepted ※ 09 September 2019       issue date ※ 10 November 2019  
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WECO01
Characterisation of Closed Orbit Feedback Systems  
 
  • G. Rehm
    DLS, Oxfordshire, United Kingdom
 
  Closed orbit feedback is applied at nearly all synchrotrons. Detailed investigations continue to be performed on the mathematical modelling of the spatial part (i.e. related to Orbit Response Matrix) and the dynamic part (i.e. the controller). This talk will serve as a summary of the ARIES workshop on closed orbit feedback organized by ALBA in November 2018. Benefits of recent advances compared to the traditional implementations will be highlighted.  
slides icon Slides WECO01 [4.912 MB]  
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WECO03 Tune Computation via Model Fitting to Swept Machine Response Measurement 482
 
  • M.G. Abbott, G. Rehm
    DLS, Oxfordshire, United Kingdom
 
  At Diamond Light Source we compute the horizontal and vertical tunes by fitting a simple multi-pole resonator model to the measured electron beam frequency response. The transverse (and longitudinal) tune response is measured by sweeping an excitation across the range of possible tune frequencies and synchronously measuring the IQ response. The multi-pole resonator model is a good fit to the measured behaviour, but the fitting process is surprisingly challenging. Problems include noisy measurements, very complex beam responses in the presence of increasing chromaticity, poor data when the beam is close to instability, and a number of challenges with the stability of the algorithm. The tune fitting algorithm now in use at Diamond has been developed and refined over many years. It is finally stable enough to work reliably throughout most beam operating conditions. The algorithm involves alternating peak finding and non-linear fitting, with a fairly naive mathematical approach; the main focus is on providing reliable results.  
slides icon Slides WECO03 [1.059 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2019-WECO03  
About • paper received ※ 04 September 2019       paper accepted ※ 09 September 2019       issue date ※ 10 November 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)