Danny, Craig, Alexei, Dan
We did another SR3 test tonight and saw the same ~5 Mpc improvement. I did a very quick noise budget to see how it has changed from alog 47351, pictures attached. Looking at DARM the improvement is mostly coming from around 25Hz now, last night it seemed like the improvement was broader. Looking at the ASC breakdown it looks like DHARD_P/Y got reduced? CHARD_Y seems noisier now at low frequency. It might be worth remeasuring the ASCs before heating up SR3 again and seeing if it is actually them reducing in the same lock and not some other noise. I saved the DTT templates in the restructured noise budget section with the tag '_SR3HTR.xml'. I had to finangle the shot noise in the budget too.
With squeezer injected and no calibration lines we peaked about 105 Mpc with the new more accurate calibration.
Frequency noise was very high tonight, but that's for another log. We have switched the SR3 heater off at 5:00PST and left the squeezer on. If SR3 is helping DHARD Y/P then some common ITM TCS could also help so that would be worth trying next.
EDIT: fixing legend in second SR3 heater test plot
Jenne reduced the DHARD P gain the other day which is why I was seeing a change in the ASC noise projection: 47509
People were asking if the calibration changed much when the SR3 heater was turned on. We didn't do any pcal sweeps at the time but here is a plot showing the pcal line magnitude as the heater is switched on. I don't know if this is the best channel to use, H1:CAL-CS_TDEP_PCAL_LINE*_RELATIVE_MAG, someone please correct me if there is a better one to use.
Line frequencies are 37, 330, 1080, 8 for lines 1-4. The 37Hz line reduced by ~1% from this metric.
