J. Warner, K. Venkateswara
We have turned on sensor correction on Z and X at ETMX since noon today.
Z on ETMX had been switched to TBetter blend by an unknown person during the weekend. Jim switched it back to the 90 mHz blend(Ryan's LLO blend). We then also turned on the X sensor correction which is currently using the tilt-subtracted super sensor.
The first two pdfs show the before and after plots for the two configurations. Before was taken ~3 am this morning and after was at ~12 noon. Note that the improvements in Yaw/Pitch at low frequencies were largely due to going to the 90 mHz blend and then using Z sensor correction.
The third plot shows the improvement in X and Z transfer functions from the ground to Stage 1 before and after the configuration change.
It seems to be helping over a large frequency range above 10 mHz and not hurting anywhere, so we will leave it on for overnight monitoring. If it affects commissioning in any way, it is easy to turn off through the ISI screens.
edit: Z sensor correction is to HEPI_IPS and X is to Stage1_CPS
J. Kissel, J. Warner
In the "after" configuration, given that the coherent linear transfer function ("SCimprovement.pdf") only shows a factor of a few amplification at 50 [mHz], yet the ASD shows a factor of 20-30 amplification, I argue that this is even more evidence for re-injection of residual tilt noise of ST1. I haven't done the usual X_blend * RY * g/w^2, but I've suggested that Jim try to play around with the RY blend filter (i.e. just use one of the other blends we already have in the bank) and see if the change in performance of RY improves or worsens the X performance.
#weneedamodel
P.S. The optic looks like it was misaligned for the "after" measurement, or there was a laser glitch during the measurement, because the optical lever noise floor seems supremely high, and I'm confident does not reflect the displacement of the optic. The "before" looks OK.