During our commissioning window today I re-ran the noise budget template for frequency noise coupling to DARM, to check if anything changed when we increased the input power from 35W to 37W (and also increased the CO2X power from 0.7W to 0.8W last week).
The first attachment shows a REFL_A to DARM TF, comparable to the purple trace in Sheila's comment here. These transfer functions look the same which is good.
The second attachment shows DARM, REFL_B and REFL_A spectra during the noise budget injection, the traces currently used in the noise budget currently are shown in black (data taken in early May). Note squeezing was not being injected during these times. Today I ran two sets of frequency noise injections:
- with REFL_A and REFL_B sensors both in the CARM loop (mint green and blue traces)
- with REFL_A only in loop, so that REFL_B can be used as an out-of-loop frequency noise sensor (pink, and brown traces) - this is what we actually use in the noise budget.
The DARM BLRMS suggest that I caught a low-frequency glitch at the end of my injection with REFL_A only in loop, hence the extra noise below 80Hz in the pink trace. So I won't put this data in the noise budget but we should re-do this measurement, since the frequency noise coupling looks much better above ~300Hz now compared to what we measured in May.
