Kiwamu reported in 22781 about a couple lock losses due to the drive to HEPI hitting the 250um limit. HEPI can handle more than this but should not need to if the PSL (likely Ref Cav) temperature does not trend off somewhere.
Attached are several PSL Temp channels for 14 days with the limit hit time noted on the run away Tidal Channel. Certainly many of the PSL Temp channels show a trend that correlates pretty well with the run away. In iLIGO we had tight temp control of the Ref Cav, do we have a temp of the Ref Cav now or is there another signal that would best represent that?
The Oct 11 near miss shows some trend as well but things are very suttle in this regard. We would be well served to tighten the ref cav temp.
The signal for the RefCav temp is H1:PSL-FSS_DINCO_REFCAV_TEMP. Unfortunately this channel is not calibrated to degrees, it just reads out in counts. I've attached a trend over the same time scale as Hugh's above (14 days) of the ETMx HEPI tidal channel and PSL laser room temperatures, and also including the RefCav temp.
At ~13:45 on 9/23 (~48 hours before ETMx HEPI hits its tidal limit) the RefCav temp seems to respond to a temperature rise in the PSL laser room; the temp in the laser room rose ~0.5 °F over the course of ~12 hours, leveling out at ~01:30 on 9/24. The RefCav shows a quick rise over the first ~45 minutes and then a slow rise and leveling off over the remaining 11 hours, also leveling out at ~01:30 on 9/24. And although the laser room temp continues to slowly increase over the next several days the RefCav temp remains steady.
