jenne.driggers@LIGO.ORG - posted 13:14, Tuesday 11 July 2017 - last comment - 13:32, Tuesday 11 July 2017(37451)
Spot positions now vs. 17 June
Per JimW's suggestion, I had a look at our beam spot positions on the test masses for now (last A2L measurement from this morning, before maintenence) versus a time on 17 June 2017 (16 June local) right after Sheila moved spots to drastically improve our range.
In the attached plot, the green squares are the old good times, and red circles are the latest measurement. Listed in the title for each optic is the total distance between the old and current spots. You can see that ETMY is basically in exactly the same place, both ITMs have moved a little bit, but ETMX has moved a lot.
So, one thing we should try today is moving the POP QPD and SOFT offsets such that we get closer to these old spots, and see if that improves our range.
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Is it not possible that the change in IMC alignment / spot positions after the Montana EQ (see LHO aLOG 37363) has also decreased (or at least changed) the PSL jitter suppression, and therefore also showing up as poor range? If so, we should try moving the IMC to its pre-EQ position as as well.