Jenne, Hang

We tried more WFS phasing with AS 90 as our centering loop today. 

## AS B 36 I:

We first looked at AS B 36 I and tried to use it for SRM sensing. We excited a length signal first and phased each segment s.t. the signal showed up in I phase, to fix the relative phase between the segments. We found that the demod phase of segs. 3 & 4 was 90 deg diff than that of segs. 1 & 2. Then we drive SRM in pitch (yaw) and rotated the demod phase for all quardrants together to optimize the angular signal in I phase. However, we could not close the SRC loop even after re-phasing. By applying a static misalignment to SRM, we found the AS 36 B I responsed only to one direction but not the other. No clue why this was the case yet.

## AS A 36:

We then decided to use only AS A 36, with Q phase for BS and I for SRM. The demod. phase was set by maximizing BS angluar signal in Q (w/ 90 centering, DRMI locked). 

The new (old) demod phase for the 4 quardrants were:

-165 (-140); -145 (-140); -145 (-140); -135 (-140)

At this config., for BS, the Q signal was factor ~ 10 of the I signal, and for SRM, the I signal was factor ~3 of Q.

## Difficulties w/ locking the IFO:

After that we tried to go further in the locking sequence, but kept losing lock at RF_DARM/DHARD_WFS. 

We first noticed that the DARM gain at RF_DARM was too large for the new config. We set it to 400 instead of increasing to 1000. Also the DHARD pit & yaw gains were too high. We decreased it by a factor of 10 and saw some oscillation at 15 Hz when offloading was almost done. Then we reverted all settings and handed the IFO to noise-hunting team. 

## Things to do:

Rephase the 90 centering WFS. The last time we did it we did not open the MICH ASC loop. Then recheck all other WFS' phasing again. If we still have trouble locking at the DHARD_WFS, stage, we may further decrease the DHARD pit/yaw gains by another factor of ~4ish. We may also just commented out the new offloading gains.