Simulation of the Global Orbit Feedback System for Pohang Light Source

This paper describes the simulation of the global orbit feedback system using the singular value decomposition (SVD) method, the error minimization method, and the neural network method. Instead of facing unacceptable correction result raised occasionally in the matrix inversion, we choose the error minimization method for the global orbit feedback. This method provides minimum orbit errors while avoiding unacceptable corrections, and keeps the orbit within the dynamic aperture of the storage ring. The simulation shows that a selection of BPMs is very sensitive in the reduction of rms orbit distortions, and the random choice gives better results than any other cases. Especially, the most effective combination is the randomly selected BPMs and the equal number of correctors located in high βx region. In a good case, we can reduce the orbit distortion by an order of magnitude. For the correction of the orbit drift, the neural network method gives less fluctuated orbits than the error minimization method.