The required diameter for the baffle if it sits on the cage at 1.77" from the test masses: the current baffle (dia. 40mm) centered along the beamline, will allow ~8.6mm visibility from the center of the test mass (in case of ETMY).
*assuming the pick off mirror is placed at the edge of the tunnel
Estimations of the visibility region (r1 on the test mass) with baffle (aperture size 40mm).
The baffle is installed on the cage at 1.125" from the test mass (distance changed from the previous elog after a double check).
The 40mm aperture is in no way going to help get clear view of the ITMs;
Required baffle diameter to have a visibility region r1 = 3 times the beam diameter