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Reports until 20:43, Friday 04 November 2016
H1 ISC
jenne.driggers@LIGO.ORG - posted 20:43, Friday 04 November 2016 (31221)
IMC Pit offsets seem to help peaks a little bit, recycling gain also

[Sheila, Jenne]

We were interested to see if the scatter peaks could be significantly reduced by moving the IMC WFS offsets, and if they're repeatable lock-to-lock.  Sheila moved DOF1_P to +350 counts and DOF2_P to -100 counts.  The DOF1 move was significant, but the DOF2 and DOF3 moves that we tried weren't.  We advocate leaving in the DOF1 offset, but not bother with the other two.  In the attached screenshot, yellow is Sheila's reference from before changing offsets, and purple is with the offsets.  The spectrum looked pretty much the same with and without the DOF2 offset, but this spectrum had it in.  We note that the IMC trans power went down a bit with the DOF1 offset and the IMC REFL camera looked pretty non-symmetric, so maybe this isn't so ideal, but the recycling gain went up and some peaks went down.

In the attached spectra, the rectangle noise between 410-440 Hz is an injection on the input pointing PZT.  Sheila's offsets improved this by not quite a factor of 2.  The improvement at the 260Hz peak is a little over exaggerated - it was bouncing up and down and we happen to have caught it at a relatively low point.

I started trying the yaw offsets, but broke the lock.  For the next person who tries this, I had gone to -350 in DOF1 yaw.  -300 was stable, but we lost lock shortly after I went to -350.  I think negative was the wrong direction, although I wasn't seeing all that much effect.  It seems like it's worth trying this some more, although if the peaks are gone after Matt's efforts tonight on the PSL ILS loop then maybe it's not so critical. 

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