jeffrey.garcia@LIGO.ORG - posted 16:15, Wednesday 25 January 2012 - last comment - 11:53, Friday 27 January 2012(2085)
X1 QUAD3 BLD3 TF comparison
X1 QUAD 03 BUILD 03 Attached are plots of the X1 QUAD 03 BUILD 03 M0 & R0 TF measurements from last night along with measurements from 01/06/2012. For the M0 mass, there is virtually no change in the resonances from the two measurements, which is expected. The R0 chain, however, is the chain where the cabling attaches between stages. On R0, all DoFs except Pitch appear to have not been affected by the cable lacing. The R0 Pitch plot (pg 5) indicates the second major pitch mode has stiffened quite a bit since the 01/06/12 measurement. The DC Pitch also decreased slightly for this measurement. Cabling between the stages may be the cause of the extra Pitch stiffening on R0, so a reassessment of the R0 cabling could prove useful.
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Comments related to this report
This sort of R0 Pitch stiffening is expected, and acceptable once cables are laced down the reaction chain. See discussion of similar before vs. after lacing on ITMY: LHO aLOG 1769. I'm actually more concerned about R0 Roll: The second mode (~0.85 Hz) seems to have split, or now has two couplings virtually right on top of each other. We should look into this further!