Sheila, Kiwamu,

Yesterday, Keita suggested us looking for any obvious sign of clipping in the ISCTEX table or some TMS mirrors (alog 16923) just by eyes (of course with goggles). So, we went to the end X station and inspected various places.

There was one mirror which showed quite bright scattering. We think that this is the one clipping the green light.

If we are lucky, maneuvering the angles of TMS and input PZTs may be able to fix the issue. Otherwise this potentially would be one of the tasks for the next vent.

The pictures of the TMX mirrors can be found in ResourceSpace (https://ligoimages.mit.edu/?c=1568)

(Details)

We started from the optics on the table. We did not find a bright scattering although there were many dim scattering all over the place because it is green light. We fully opened up two irises that were in front of the HWS 2" mirror and the one after it just in case. Then we checked the mirrors on the periscope which were not easy to look at directly by eyes and sensor card. We used a camera to remotely peek these mirrors. The beam spot on each of these mirror looked fine and we did not see a bright scattering off of them.

We then tried looking for any bright mirrors on the transmission monitor table (TMS). We used a camera to peek the mirrors. According to the pictures we took, the first mirror on TMS (M8 in D1201457-v2) showed a bright scattering off of it. It is hard to say where exactly the incident beam hits, but it seems that the beam is too low. On the other hand, it is not easy to tell about the horizontal off-centering. Note that since there was a risk of accidentally block the beam and trip the PZT pointing control, we disabled the loops with the offsets held at the output. Also the ETM was miasligned at this momenet in order for Elli and Dave to do the signal-recycled Michelson test. The way we identified M8 is that we could see another mirror closely behind M8, which we think is M9. Also some pictures showed another mirror far left from M8 and we think it is M10 as the mirror holder is mounted in a opposite direction. Also, some pictures showed another bright spot which is a known scattering point from the vacuum view port.