sheila.dwyer@LIGO.ORG - posted 20:10, Saturday 28 February 2015 - last comment - 20:23, Sunday 01 March 2015(17007)
attempt to engage BS ISI ST2 loops
We made a few attempts to turn on the BS stage 2 loops after DRMI acquired lock this afternoon, both times DRMI became misalinged and we loct the lock. We reset the CPS offsets and saw that the residual was small before turning on the loops, but still things became misalinged when we turned the loops on.
As far as I can tell, this yaw misalignment is a transient which happens when Rz is turned on. In the attachment, you can see that the BS gets misaligned by about 0.3 μrad, and then settles back to its old value after about 30 s. 0.3 µrad is too much misalignment to maintain DRMI lock; probably 0.1 µrad or less is required.
So perhaps we just need to find a gentler way to engage the stage 2 Rz loop.
Turning on x, y, and z of stage 2 seem fine as far as the BS pitch and yaw are concerned.