[Ge, Kokeyama]

We looked at the PRM-PSD to align the PRM-reflected light to hit the beam dump in IFI again. Frist of all steering mirror for PSD was loose at the mount (now fixed), so there is a possibility the PSD setup slightly moved.

Since we don't believe the PSD anymore, we opended the 152 flange (+Y side, the camera viewport) of the IFI chamber and check the misaligned beam by an IR viewer and sensor card. The misaligned beam was hitting the rear (-Y side) of the beam dump which is not enough misalignement of PRM, even if we misaligned the PRM with maximum offset, -25000 cts yaw without tripping the analog watchdog. With -25000 cts, the spot was still on the -Y side of the dump and more offeset was necessary, otherwise some part of the spot hit the edges and it shines the beamdump (see, the screensthot).  It used be only -6000 cts yaw offset to hit the beam dump. With -8000 cts misalign in yaw, the reflected beam hit the heat sink of the beam dump on -Y side and it strongly sined.

Anyway the 152 flange was closed and put the gigE camera was put back.

After leaving the mine, we tried the same procedure above with gigE camera. This time, the scattered light shined very strongly with -17000 cts yaw offset. Something may be strange on the PRM?

Screenshot1: No beam at all. Exposure 1e6.
Screenshot2: MC locked, PRM is aligned (IM coil offsets [0, 0]). Exposure 5e5.
Screenshot3: MC locked, PRM is misaligned (IM coil offsets [-25000, -25000]). Exposure 5e5.