keita.kawabe@LIGO.ORG - posted 11:36, Friday 04 September 2015 - last comment - 21:09, Tuesday 08 September 2015(21213)
Y IR QPD rails during 24W operation
Due to a crazy big offset of -0.5 in Y_TR_B_PIT (for SOFT modes sensing), Y IR QPDB is almost always railing a bit in 24W operation, and Y IR QPDA is not too far.
Next time IFO drops out of lock, somebody needs to lower the whitening gain by 3dB and set a new dark offset for each quadrant.
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These whitening gains are controlled by the ISC_LOCK guardian. We already lower them by 6 dB in the DRMI_ON_POP state (which produces the momentary fake jump in arm power that everyone asks about), so it sounds like we should be lowering them by 9 dB instead.
[Shamefully, we don't change the dark offsets when we change the whitening in this step.]
Shame.
DRMI_ON_POP now turns down whitening gain from 18 dB to 9 dB.