Hang, Dan

It's getting late so this is a quick post, more analysis to come tomorrow.

Today we powered up to 30W and did some fine tuning of the TCS to improve the CHARD sensing matrix rather than putting in a new one. I adjusted the CO2s to optimise the REFL9I, RF18, PRCG until they stopped improving anything, then I started increasing 0.4W common ITM RH and 0.2W ETM common RH. This made all the outputs much quieter and helped fix our CHARD/PRC2 sensing matrix coupling. We started to have a 3mHz oscillation in CHARD/PRC1/INP1 but it didn't cause too much of an issue. We went upto 33W and then we lost lock.

This lock loss was a bit messy as all the ring heater values had changed so the the DRMI thermal state was a bit mismatched. Even though the mismatch was very strong DRMI still locked in less than a minute, although RF18 build up was ~50 instead of ~80. After the RHs had settled and I had found a rough CO2 setting for 2W DRMI was locking ok, RF18~60.

We had issues getting through engaging full IFO ASC, though that was from changes we made in error today. Hang can comment on what we moved around.

Once we were back up and locked again we got all the way to 35W with little issue, and seemed stable enough that we could have stayed there. All the ASC loops were quiet. PRCL optical gain didn't drop as much as it used to with these TCS settings so we had to adjust the PRCL gain increments in ADJUST_POWER. However it still gets low at 38W where we had a fast lock lost almost straight away.

Going from 33W to 35W we increased the power by ~6% and the arm power increased by ~4% looking at TR photodiodes.

One odd thing we did see was that the input power was oscillating at 80mHz looking at MC2 trans, with corresponding oscillations in the arm powers, not sure why.