Genevieve, Lance, Robert
To further understand the roughly 10Mpc lost to the HVAC (https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=72308), we made several focussed shutdowns today. These manipulations were made during observing (with times recorded) because such HVAC changes happen automatically during observing and also, we were reducing noise rather than increasing it. The times of these manipulations are given below.
One early outcome is that the peak at 52 Hz in DARM is produced by the chilled water pump at EX (see figure). We went out and looked to see if the vibration isolation was shorted, it was not, though there are design flaws (the water pipes arent isolated). We switched from CHWP-2 to CHWP-1 to see if the particular pump was extra noisy. CHWP-1 produced a similar peak in DARM at its own frequency. The peak in accelerometers is also similar in amplitude to the one from the water pump at EY. One possibility is that the coupling at EX is greater because of the undamped cryobaffle at EX.
Friday HVAC shutdowns; all times Aug. 18 UTC
15:26 CS SF1, 2, 3, 4 off
15:30:30 CS SF5 and 6 off
15:36 CS SF5 and 6 on
15:40 CS SF1, 2, 3, 4 back on
16:02 EY AH2 (only fan on) shut down
16:10 EY AH2 on
16:20 EY AH2 off
16:28 EY AH2 on
16:45 EY AH2 and chiller off
16:56:30 EY AH2 and chiller on
17:19:30 EX chiller only off, pump stays on
17:27 EXwater pump CHWP-2 goes off
17:32: EX CHWP-2 back on chiller back on right after
19:34:38 EX chiller off, CHWP-2 pump stays on for a while
19:45 EX chiller back on
20:20 EX started switch from chiller 2 to chiller 1 - slow going
21:00 EX Finally switched
21:03 EX Switched back to original, chiller 1 to chiller 2
Turning Roberts reference to LHO:72308 into a hyperlink for ease of navigation. Check out LHO:72297 for a bigger picture representation of how the 52 Hz peak in the broader DARM sensitivity, and from the Time Stamps in Elenna's plots, they were taken at 15:27 UTC, just after the corner station (CS) "SFs 1, 2, 3, 4" are off. SF stands for "Supply Fans" i.e. those air handler unit (AHU) fans that push the cool air in to the LVEA. Recall, there are two fans per air handler unit, for the two air handler units (AHU1 and AHU2) that feed the LVEA in the corner station. The channels that you can use to track the corner station's LVEA HVAC system are outlined more in LHO:70284, but in short, you can check the status of the supply fans via the channels H0:FMC-CS_LVA_AH_AIRFLOW_1 Supply Fan (SF) 1 H0:FMC-CS_LVA_AH_AIRFLOW_2 Supply Fan (SF) 2 H0:FMC-CS_LVA_AH_AIRFLOW_3 Supply Fan (SF) 3 H0:FMC-CS_LVA_AH_AIRFLOW_4 Supply Fan (SF) 4
My Bad: -- Elenna's aLOG is showing the sensitivity on 2023-Aug-17, and the Robert logging of times listed above are for 2023-Aug-18. Elenna's demonstration is during Robert's site-wide HVAC shut down 2023-Aug-17 -- see LHO:72308 (i.e. not just the corner as I'd errantly claimed above.).
For these 2023-Aug-18 times mentioned in this LHO aLOG 72331, check out the subsequent analysis of impact in LHO:72778.