Travis, Giles, Gary, Jason, Norna, Betsy
This afternoon, Travis, Gary, and Giles finished welding in fibers to the ITMy (ITM011) and it's glass PUM. At some point during the welding process on Wed a roll of the Test Mass was introduced. It was noticed this morning before the final destress/annealing took place. The team attempted a correction to alleviate ~1/2 of the roll error which was somewhat successful. After reevaluating the tolerance for roll with Dennis and Calum it was decided to leave the roll error as is. The Test Mass is now hanging from the fibers.
Note, the roll error observed this morning was +/- 1.2mm (~7mRad). We determined that this roll occured between welding the 2 sides of the suspension with the masses locked down the entire time. The PUM did not show this large roll error. After correcting and suspending the ITMy, the roll was found to be +/- 0.75mm (~4mRad). While the roll "tolerance" has never really been set, we attempt to get the roll error within +/- 0.2 mm because that is what we have found we are able to do in all of the previous other monolithic suspensions.
Email from Dennis regarding acceptable roll tolerances of an ITM:
To see if the residual roll was problematic, I prepared a case mark.barton/20140304TMproductionTMrollpert of the QuadLite2Lateral model with the latest monolithic parameters but with a perturbation to d4 (the height of the fibre attachment point above the optic COM) at each of the fibres, positive on one side and negative on the other. Even a perturbation of ±1.2 mm (the value reported to me before the extra de-stressing reduced it to 0.75 mm), there was no visible difference in any of the top mass force/torque to optic TFs and especially no extra peaks from cross coupling. This is to be expected because the optic is almost perfectly symmetrical in roll and the compliance of the fibres was not changed (the de-stressing did not touch the central section of the fibres so this was not changed in the model). So the performance of the suspension should not be degraded.
Final alignment numbers for the monolithic (all directions/rotations reported from the view of the IAS equipment, i.e. looking at the HR face of the ITMy):