cheryl.vorvick@LIGO.ORG - posted 17:47, Wednesday 02 January 2013 - last comment - 08:56, Monday 07 January 2013(5020)
IM3 on a EQ stop: all IMs undamped
I ran a quick test today on IM3, which now has the largest offsets of the 4 HAM AUXs. In the attached plot, red shows the pitch offset, black the yaw offset - blue shows very different behavior when each offset it removed - the damping of the oscillation when the pitch offset is removed shows the optic is touching an EQ stop. I left all HAM AUXs, IM1, IM2, IM3, and IM4, undamped overnight.
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Please keep in mind that the Eddy Current Dampers coupling with pitch is _much_ stronger than that with yaw, so I would't considere the different decay rates as evidence of rubbing.
If rubbing is indeed suspected, I would suggest to check by either running a full set of TF and looking for anomalies, or trying a (small) DC actuation of pitch and yaw in both direction and looking for asymmetries in the displacement measured by the OSEMs.