Betsy, Camilla, Sheila, Tony, Robert

After Wednesday’s discovery that the PUM-level inter-chain stops would prevent us from overlaping the ITMY AR optical lever beam and the arm-cavity side CPY beam (overlapping these beams gives the correct orientation of CPY), we decided to back off the adjustment just a little to reduce the chance of touching and leave the beams closer than prior to the vent, though not overlapping.  At the end of Wednesday, the beams that were supposed to be overlapped were about 0.18 of the ITMY HR - ITMY AR spot distance. They were still at 0.18 Thursday morning and, after backing off a little, were at 0.22 of the HR-AR distance (with the same 0,0 slider settings they started out at 0.32).

These measurements were made with the R0 sliders at 0 pitch and 0 yaw. We also found the slider settings for the closest approach (see figure). At this closest approach the spots only differ by 0.085 of the HR-AR distance (3.4e-4 radians).

I calibrated the CPY sliders assuming the ITMY HR - ITMY AR spots were 4e-3 radians apart, due to the 0.08 degree wedge with assumed 1.45 index of refraction (coatings not considered). I get 0.63 microradians per slider unit in pitch and 0.69 in yaw. The calculated separation of the HR-AR spots, 4e-3 radians, was approximately equal to the measured separation, 3.8 e-3 radians, assuming we were 32 meters from the test mass.