A view of the dihedron can be seen on the first picture.
We have checked both angles of the dihedron using an autocollimator in CB clean rooms.
We have found that the "horizontal" angle is : 89 deg 58'53" 15" (the spec was 89 deg 58'58" 2").
This has to be compared with Ralf Ottow's measurement 89deg 58'54.5". This slight difference on the angle lead to a beam shift inside the dihedron of 2.4mm towards the IMC end mirror which is a priori not a problem. The beam alignment towards the Faraday isolator an dthe refrence cavity will be recovered by adjusting M13 and M12 mirrors.
We have also measured the "vertical" angle and we have found : 509 urad 73 urad which is compatible with R. Ottow's measurement of 430urad.
This is indeed much better than what we had with the currently installed dihedron: 2mrad.
As you can see on the second picture there are a few zones where the optical contact didn't happen. We think it should not be a problem
but we cannot check it before putting it under vacuum in IB tower.
The installation of this new dihedron is planned for next week.
