We tried to diagnose the scattering or clipping or whatever that is visible inside the IFI output baffle aperture (alog 90536, especiall this video from that alog). It's not subtle, is always there even when the beam is blocked between PRM and IM4, and it's not just once in a while, it looks to be as frequent as strong flashes from IMC.

This is not the clipping of the forward propagating beam on the baffle as the beam height is pretty good (beamheight_dkdp_baffle.mp4) and YAW is also OK on dkdp baffle as well as IFI output baffle (dkdp_baffle_yaw.mp4, IFI_output_yaw.mp4).

We took a video of the back (i.e. -Y) side of the IFI output baffle through the output CWP by inserting a big dentist mirror between DKDP baffle and CWP and shooting from the +Y side. Video will be posted later (the raw video from IR sensitive camera exceeds 15Mb limit of alog and I don't have a good editor on my laptop).

Anyway, it seems like something is maybe hitting the bottom edge of the baffle from the back, Disha and Rahul think that there's something at the top too but I'm not sure.

We don't know what it is but we've done everything that could be done in situ without resorting to drastic measures (like temporarily removing all suspension baffles that block our view, which takes time despite that we don't know if that helps or not, or moving IFI to the lab which I won't do at this point in time). Since I'm pretty sure that this is NOT the clipping of the main beam as was noted above, my recommendation is to give it up at this point and move on, knowing that this thing does exist.

Together with alog 90536, we're done with HAM1/2/3 alignment today. Let's hope that the IM1 mystery motion won't return.

Fil already started ground check of suspensions, we'll do the ISS unit and the QPDs in HAM2/3 tomorrow.