Impact of the Lambertson septum magnet on the photon beam flux in the PLS-II beam line experiment

The Pohang Light Source II (PLS-II) has been operating successfully since the completion on March 21, 2012 of the PLS-II project to upgrade the PLS. Because top-up injection is becoming a general operation mode in the 3 (rd) generation light source, top-up operation using full energy injection from the 3 GeV linear accelerator is one of the main goals of the PLS-II. In the PLS-II topup operation, small beam loss of the injected beam in the storage ring and stored beam oscillation during injection are two main issues to be solved. The top-up mode has been successfully operated since March 19, 2013, because the beam loss of injected beam in the storage ring was reduced. As a result, the flux stability, excepting injection time, in the beam line has been dramatically improved. During injection, a systematic dip pattern occurs in the photon beam flux due to oscillation of the vertical stored beam. The main source of the oscillation of the vertical stored beam is the leakage field of Lambertson septum magnet. In this paper, the impact of lambertson septum magnet on the stored beam oscillation will be described and an improvement plan will be presented.