I had another look at the slow drop in sideband powers that consistently breaks lock within 20 minutes of powering up to 50 Watts.
This time I changed the soft loops to X,Y degrees of freedom (first I made the pitch filters for dsoft match csoft, this worked fine but isn't in the guardian). I ran dither lines on the test masses and tried to move offsets in the soft loops to keep the spot positions stable, but this didn't help the tanking sideband powers at all. I tried moving PR2/SR3/POP offsets. SR3 can help improve the AS90 build up after a PR2 move that helps POP18 but walking these together didn't work out well. I tried locking at 40 Watts where we have more time to move offsetsm but didn't find any alignments that could help the sideband build ups. We might have to look at some lensing. I tried using offsets in the POPX to PR3 loop, but as we expect these only made things worse.
The fastshutter lockloss checker seemed to think that the shutter had not fired in one lockloss today, but as shown in the attached screenshot, it did fire. Leaving the IFO with Kiwamu for the night.
On the fast shutter script:
I forgot to mention that I fixed a typo inthe LOCKLOSS_SHUTTER_CHECK yesterday. The arm power check looked at the x-arm power twice (instead of both arms, i.e. I changed line 26 from
if circ_power_x >=arm_power_upper_thresh or circ_power_x >=arm_power_upper_thresh:
to
if circ_power_x >=arm_power_upper_thresh or circ_power_y >=arm_power_upper_thresh:
and line 34 from
if circ_power_x < arm_power_lower_thresh or circ_power_x < arm_power_lower_thresh:
to
if circ_power_x < arm_power_lower_thresh or circ_power_y < arm_power_lower_thresh:
It looks like the checking script now sometimes triggers without the interferometer actually dropping lock - the Guardian time stamp on Sheila's plot does not agree with the actual lock-loss.
This probably happened because during the transition the Y arm fulfilled the HIGH_ARM_POWER criteria, while the X arm fulfilled the LOW_ARM_POWER criteria.
Thus I changed line 26 from an 'or' to and 'and'. This hsould properly latch the transition.
if circ_power_x >=arm_power_upper_thresh and circ_power_y >=arm_power_upper_thresh:
return 'HIGH_ARM_POWER'
The last 4 lock-losses (two from Sheila's two locks in INCREASE_POWER, and two of Stefan's lock in COIL_DRIVER_SLOW
