Yuta, Stefan, Kiwamu

Our goal in this morning was to get the PRMI locked with the 3f signals and test the stability. However we didn't get there yet.

A good news is that the initial dither alignment worked well, so that the alignment became less painful. Once PRX and PRY were aligned by the dither system, we could get a decent alignment in PRMI.

What we did in this morning:

• We ran the dither system on PRX and PRY via the guardian
  • This worked well.
  • We still need to make the whole processes sequential. Also the PRM suspension model needs to be updated to get the newly separated dither excitation via IPC blocks as was done in the PR2 model.
• We adjusted REFLAIR_A_RF45 demod such that there is less cross coupling in the two loops.
  • We empirically ended up with a phase of 142.7 deg.
  • This gave a less funny dip in the PRCL open loop transfer function.
• We increased the PRCL gain from -0.4 to -1.3 to have a stable PRC loop.
• We found that the ITMY ring heater had been off
  • This probably explains why we had to gain up the PRCL loop.
  • The cavity build up in POPAIR_B_RF18 was measured to be about 18000 counts with the whitening gain set at the maximum of 45 dB.
  • This is certainly smaller than before. We used to see it reaching 30000 counts with 4 W of the power in the ITMY ring heater.
• We let the PRMI be locked for a long enough time so that we can make an noise budget attempt for the first time.
  • Yuta is working on making a NB plot
• We are leaving the ITMY ring heater with a bit higher power of 7 W (i.e. 3.5 W in upper and lower heaters). See the attached.