Kiwamu, Stefan

We noticed that in full lock (before power up) we again have questionable WFS. Indeed it seems to again be SRCL1 YAW that runs away - slowly at low power, but rapidly at high power. This is all a deja-vu, see elogs 18442, 18923, 18931.

More investigation suggested that it is actually the QPD loops that pull us into a regime where the other loops are not stable. So for now we changed the QPD loop offsets at low power to just keep us at the same location:
  New values: H1:ASC-X_TR_A_PIT_OFFSET H1:ASC-X_TR_B_PIT_OFFSET H1:ASC-X_TR_A_YAW_OFFSET H1:ASC-X_TR_B_YAW_OFFSET
   -0.084
   -0.212
   -0.023
    0.006
  Old values: H1:ASC-X_TR_A_PIT_OFFSET H1:ASC-X_TR_B_PIT_OFFSET H1:ASC-X_TR_A_YAW_OFFSET H1:ASC-X_TR_B_YAW_OFFSET
   -0.029
   -0.158
   -0.007
    0.105

However we still lost it on POWER UP. More work needed here.


We also reverted the changes from earlier today (alog 19511): ETMX ISCINF gain back to 1, and the L1 gain back to 0.28. This now gave us a lower peak-peak ESD drive and - unlike earlier today - ALS DIFF engaged just fine... (no idea why it acted up earlier...)