We worked on the beam path from MC to BS this evening.
After the beam spots on MC1 and MC3 were close to the actuation nodes (<1mm away) we checked the beam position on the Faraday Isolator (FI) to make sure that it is passing through both the input and output apertures without clipping. The beam is slightly displaced (by about half a beam diameter) downwards at the input of the FI. The picture below is a screen shot from the MC1 monitor while Kiwamu held an IR card in front of the FI.
We then proceeded to check the beam position on various optical elements downstream. But first we levelled the BS table and checked to see if the reflection from PJ1 (1st Piezo) is landing on the MMT1 properly. It was and we did not make any adjustment to PJ1. However the reflection from MMT1 was not centered on MMT2. We adjusted the MMT1 to center the beam on it. We then adjusted MMT2 to center the beam on PJ2. At this point we noticed that the spot on IPPO (pick off window) was off towards the right edge. When we centered the beam on this it missed the center of the PRM. In order to decide what needs to be moved, we adjusted PJ2 such that the beam hits the PR2, bounces back to PR3, and becomes co-incident with the green beam from X-arm on the BS. Under this condition the beam is not in the center of PRM and nor is it centered on IPPO. In fact it is being clipped at the edge of the IPPO.
It is clear that both IPPO and the PRM need to be moved. To be sure that the beam is centered on PR2 we plan to open the ITMX chamber tomorrow.