Virgo Logbook

Summary:

Reduced the OMC PZT dither modulation in LN3
from 1e-2V to 3e-4V for OMC1, at 1e-5V started to see extra noise in the sensitivity
from 1e-V to 1e-4V for OMC1, at 1e-5V started to use most of the dynamic of the PZT with feedback noise
put the new levels in the automation, data below to be checked more carefully if this choice is really good
Did a small alignment correction on OMC1 (improved transmission by ~0.5%)
OMC2 alignment was difficult because of new B1 PDs, picomotor action was saturating the audio channel. Had to recommission control in reflection of OMC1 and OMC2
There is ~1.5% lost in a misalignment mode between OMC1 and OMC2, did not manage to reduce this

06:57 UTC (2min) OMC1 PZT 3e-3, OMC2 PZT 1e-2
07:01 UTC (2min) OMC1 PZT 1e-3, OMC2 PZT 1e-2
07:04 UTC (2min) OMC1 PZT 3e-4, OMC2 PZT 1e-2
07:07 UTC (2min) OMC1 PZT 1e-4, OMC2 PZT 1e-2
07:10 UTC (2min) OMC1 PZT 3e-5, OMC2 PZT 1e-2
07:13 UTC (2min) OMC1 PZT 1e-5, OMC2 PZT 1e-2 - PZT control correction is 2V peak-to-peak, some signs of extra noise in h(t) at 50-70Hz
07:16 UTC (2min) OMC1 PZT 3e-4, OMC2 PZT 1e-2

07:19 UTC (2min) OMC1 PZT 1e-3, OMC2 PZT 1e-3
07:22 UTC (2min) OMC1 PZT 1e-3, OMC2 PZT 3e-4
07:25 UTC (2min) OMC1 PZT 1e-3, OMC2 PZT 1e-4
07:28 UTC (2min) OMC1 PZT 1e-3, OMC2 PZT 3e-5
07:31 UTC (2min) OMC1 PZT 1e-3, OMC2 PZT 1e-5 - PZT correction is 4V peak-to-peak

07:34 UTC (2min) OMC1 PZT 3e-4, OMC2 PZT 1e-4
07:37 UTC (2min) OMC1 PZT 1e-5, OMC2 PZT 1e-4
07:40 UTC (2min) OMC1 PZT 3e-4, OMC2 PZT 1e-4 - this will be the new OMC modulation depth in LN3

08:11 UTC (4min) OMC1 scan upgoing (1% in TEM order 1 mode)
08:15:30 UTC (4min) OMC1 scan downgoing and lock (2% in TEM01 - vertical)

Figure 1 illustrates these scans (before re-alignment)

09:05 UTC OMC2 scan befor alignment

11:57 UTC (2min) OMC2 scan after alignment