Matt, Camilla

While looking into a reason that we needed to continually increase EY RH over the last 6 months to avoid PIs, we've attached some trends.

In the past ~6 months there there was a 2% decrease in circulating power corresponding with a kappa_c decrease, Sheila and Dana found the same in 2023 75193. Plot here. Sheila and Dana thought this was as the OMC throughput has degraded since installation but we haven't re-checked that the balance of the two OMC DCPDs.

There is two distinct changes in PRG over the last 6 months: 10th Dec 2024 and 1st Feb 2025, I initially though they were conveniently a week or so before the EY RH increase, however they are when IM4 trans was centered 81735 / re-calibrated 82260 which probably cannot cause a physical change.

Interestingly the OM2 temperature is an interesting measure of the in change in temperature and that does change over the last 6 months, it's not clearly correlated with the circulating power change. Bottom trend of attached plot.