[Carl, Ushiba, Oshino, Haoyu]

This morning we replaced the REFL PDA2 for 3f locking as it was not working properly. The beam is re-aligned to the new PD. We found 3 beams reflected from the PD which cannot be fully dumped with the original beam dump (Fig1). We changed the height of the original dump to block the lowest beam and the middle beam (Fig2). Another beam dump is added to dump the higher larger ghost beam spot (Fig3). We found there is a lot of scattering light from the beam shutter when it is closed. The situation should be better when the shutter is open for PRFPMI lock. Fig4 shows the position the PDA2 and two beam dumps for it, the new one is indicated.