Fast orbit beam stabilisation for a synchrotron

Synchrotron light sources can produce very intense beams of X-rays and ultra violet light for a range of applications, including protein crystallography, materials characterization and high resolution imaging. The Diamond Light Source is a 3rd generation synchrotron that has recently been constructed near Oxford, United Kingdom, which produces a 3 GeV electron beam in a ring of circumference of over 560 m. A key requirement of the process is that the vertical and horizontal location of the beam should be controlled to within 10% of the beam size, which corresponds to the RMS variation being less than 12.3 μm in the horizontal direction and 0.6 μm in the vertical direction. The beam location is subjected to disturbances caused by the effects of Insertion Devices and the effect of ground motion, particularly between 16 Hz and 30 Hz, where the ground motion is amplified by the resonances of the girders supporting the ring magnets. To achieve the specification, a fast beam stabilization feedback system is used to regulate the horizontal and vertical position of the beam in the presence of disturbances in the range 1 Hz to 100 Hz, using 170 sensors and actuators in both planes, positioned around the ring at a sampling rate of 10 kHz. This paper describes the design of the controller for this system and the results from the implementation are shown.