cheryl.vorvick@LIGO.ORG - posted 15:51, Thursday 15 December 2016 - last comment - 17:35, Thursday 15 December 2016(32609)
Ops Day Summary:
TITLE: 12/15 Day Shift: 16:00-00:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Observing at 70.0775Mpc
INCOMING OPERATOR: Patrick
SHIFT SUMMARY:
Activities:
- earthquake: event time: 22:23:29UTC: alog 32611
- earthquake: event time 22:53:03UTC: no alog, 0.05um/s on DMT
- EY gltich at 23:23:09 and 23:23:17UTC
- range drop 23:24UTC, L1 lost lock
- DUST ALARM: 23:25:11UTC: PSL: 0.3um, 220PCF, cleared: 23:36:11UTC
additional activity before I arrived:
Just FYI.
The problem of big violin (or any big high-Q resonances) is mostly the saturation of ADC (OMC DCPD) or DAC (mostly ESD).
To tell if whatever peak is too big or not, measure the OMC DCPD A IN1 and one of the EY ESD output as shown in the attached.
First of all, you see the time series and OMC DCPD is still very far from its ADC ceiling of +-32k, and ESD output is also very far from its ceiling of +-131k, so you don't need to worry about saturations. Note that you need to set the resolution of dataviewer 16384 and observe for at least 10 seconds before making your judgement.
If these things approach the ceiling you need to damp the worst offender, which you identify by looking at the DARM spectrum, or better, by measuring the DCPD_A_IN1 and ESDOUTF_LL_OUT spectrum (second attachment). In this case, even though we already know that it's still safe, you can see that the 4.7kHz mode is the biggest offender. In DCPD it's about 100 cts RMS or 2*sqrt(2)*100 ~300 cts pp, which is totally negligible compared with DC. In ESDOUTF_LL_OUT, it's about 10k cts RMS or ~30k pp.