[Jenne, Georgia, Gabriele]

We found the PRMI locking from time to time, and managed to realign it on the fly and acquire a stable lock. Afterwards we aligned the SRM using SRY, and moved on to DRMI.

We can lock DRMI without major problems and tweaked the alignment. POPAIR_B_RF18_I_NORM was as high as ~19 counts, and POPAIR_B_RF90_I_NORM as high as ~7 counts.

We then tuned the MICH, PRCL and SRCL loop gains, by measuring the open loop gain and tuning so that the unity gain frequency is at the maximum phase margin:

• PRCL UGF was 90 Hz, moved to 60 Hz. Gain 28 > 18
• MICH UGF was 4.5 Hz, moved to 8 Hz, Gain 1.0 > 2.0
• SRCL UGF was 30 Hz, ok

Then we checked the phasing of the REFLAIR signals. We drove a PRCL line at 138 Hz, notched it in MICH and SRCL, and tuned REFLAIR_9 demodulation phase to minimize the line in Q. The phase was -17 (deocupling I/Q ~ 10) and we moved it to -17.5 (decoupling I/Q ~ 100).

Similarly we injected a 138 Hz line in SRCL (and notched in MICH and PRCL) and minimized the line in REFLAIR_45_Q. The phase was 80 (decoupling I/Q ~ 12) and we moved it to 84 (decoupling I/Q ~ 100).

Finally, we retuned the REFLAIR_9 element in the LSC matrix, by injecting a line in PRCL, measuring the ratio REFLAIR_9_I / REFLAIR_45_I and tuning the matrix element to cancel the PRCL contribution to the SRCL error signal. The previous value was -5.03, the new value is -5.508.