[Jenne,Yuta]
We succeeded in locking PRMI in sideband and carrier.
Measured power recycling gain was ~60 power recycling gain was 4 (edited by YM on Feb 27; see elog #6947), but we have many things we cannot explain.
Snapshots:
Here you are, Jamie.
PRMI sideband locked
PRMI carrier locked

I centered POP camera and put attenuator to take these snapshots.
Compare with previous ones.
Aug 17, 2012 elog #7213
Jun 28, 2012 elog #6886
Mar 15, 2012 elog #6421
Locking details:
== MI only ==
MICH: AS55_Q_ERR, AS55_PHASE_R = -12 deg, MICH_GAIN = -7, feedback to BS
== PRMI sideband ==
MICH: AS55_Q_ERR, AS55_PHASE_R = 24.5 deg, MICH_GAIN = -0.05 (acquisition) -> -5 (UGF ~100 Hz), feedback to BS
PRCL: REFL33_I_ERR, REFL33_PHASE_R = -22.65 deg, PRCL_GAIN = 4 (UGF ~120 Hz), feedback to PRM
== PRMI carrier ==
MICH: AS55_Q_ERR, AS55_PHASE_R = 24.5 deg, MICH_GAIN = -0.08 (couldn't measure UGF), feedback to BS
PRCL: REFL33_I_ERR, REFL33_PHASE_R = -22.65 deg, PRCL_GAIN = -0.3 (couldn't measure UGF), feedback to PRM
Power recycling gain:
POPDC was 32 when PRM is misaligned, 25 when PRMI sideband locked, ~2000 when PRMI carrier locked.
This means, power recycling gain is ~60 power recycling gain is ~4 (=POPlocked/POPmis*T_PRM=2000/30*0.06). Expected power recycling gain for PRMI is ~45, when there's no loss (see elog #6947).
I reduced POPDC PD gain so that it doesn't saturate.
Issues:
- We optimized AS55_PHASE_R to -12 deg by looking at MI signal. But somehow, -12 deg didn't work for PRMI.
- Somehow, REFL11_I didn't work to lock PRCL.
- REFL11_Q didn't work to lock MI. SNR not enough?
- We saw POPDC flashing up to ~15000. What is this?
- Carrier lock was not stable, we couldn't hold for more than ~30 sec. It looks like PRM moves too much when PRMI is locked.
- Input pointing is drifting a lot in pitch. I had to re-align TT2/TT1 to the arms every ~1 hour to get good MI alignment. When I tweak TT2/TT1, both TRY and TRX gets better. I think this shows that input pointing is drifting, not the arms.
Next:
- redo PRM/BS coil balancing
- optimize REFL33 rotation phase
- stabilize carrier lock somehow
- measure PRC g-factor
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