Beam based alignment of BPM and orbit stabilization at the Photon Factory storage ring

Beam orbit of the PF ring is adjusted to deliver the photon beams on the proper axes of all experimental beam lines. During the user time, the beam orbit is maintained at the reference orbit by an orbit feedback system. In the vertical direction, the feedback was performed at a high repetition rate as 10 ms. In order to improve the stability and reliability of the beam position measurement, we have continued the beam based alignment of BPM. The remnant errors in the BPM offsets were estimated at all BPMs. A systematic error was found out at a specific part of the ring. We could fix a BPM that had an offset drift depending on the beam current. The amount of the drift was determined by the beam-based measurement.