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Time-delayed Feedback Control of Electron Beam Energy Using H_inf Optimal Fractional Delay


A. Rezaeizadeh, R. S. Smith

IEEE Transactions on Control Systems Technology, vol. 24, no. 6, pp. 2176-2181

In the two-bunch operation mode of the Swiss Free Electron Laser (SwissFEL) machine, two electron bunches, separated by 28 ns, are fired and accelerated every 10 milliseconds. The electron beam is passed through several accelerating cavities which are energized by high power Radio Frequency (RF) pulses. The RF voltage generates a specific time-dependant accelerating gradient profile which results in different energy gains for the two bunches. It is often required that the two electron beams experience the same accelerating gradient through the cavities. This can be achieved by shifting the RF pulse in time to change the relative energy of the two beams. However, in the digital RF system used here, the minimum shift is limited by the sampling time of the Digital-to-Analog Converters (DACs). In this paper, we develop a control scheme for the energy difference control which finely tunes the RF pulse timing by a fractional delay filter. The method has been successfully tested at the SwissFEL injector test facility.


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% Autogenerated BibTeX entry
@Article { RezSmi:2016:IFA_5406,
    author={A. Rezaeizadeh and R. S. Smith},
    title={{Time-delayed Feedback Control of Electron Beam Energy Using
	  H_inf Optimal Fractional Delay}},
    journal={IEEE Transactions on Control Systems Technology},
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