A method to detect multiple error sources and suppression of periodic beam motion with feedforward correction

A high electron beam stability at the source points of synchrotron radiation is required for the preservation of the low emittance to generate highly brilliant photon beams to users. To improve beam stability, a method based on the response matrix between corrector magnets and beam orbit distortion at beam position monitors (BPMs) is used to detect multiple error sources at a particular frequency or a malfunction of power supplies after a beam trip. Horizontal beam motions with dispersion-like patterns, can be dealt with separately. This method has been used at the Taiwan Photon Source (TPS) to detect different types of error sources and to obtain simultaneously their relative phases and amplitudes. By employing a predefined current waveform obtained from error induced beam position variations in a feedforward correction method, a 3 Hz beam motion caused by booster stray fields could be reduced to one fifth. Furthermore, a 60 Hz beam motion due to stray fields from electric devices powered by the mains could be reduced to one-third compared to applying fast orbit feedback only.