TITLE: 03/05 Eve Shift: 0030-0600 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Preventive Maintenance
INCOMING OPERATOR: Oli
SHIFT SUMMARY:
IFO is in PREVENTATIVE_MAINTENANCE and LOCKING at DARM_TO_DC_READOUT
We have been unable to lock since conclusion of maintenance. The issue concerns PRMI's ASC not improvign POP counts sufficiently for DRMI to maintain lock.
While wind and microseism was the early culprit and assumption of locking issues, both have calmed down and revealed PRMI_ASC as the problem. Since ~20:30 PT, we have been in a cycle of PRMI and DRMI where PRMI is able to lock and stay locked to move to DRMI, but then DRMI is unable to lock. When we stay at PRMI_ASC, it can stay locked indefinitely.
Elenna, Sheila and I troubleshot this quite exentsively, by moving all relevant suspensions (PRM, BS, PR2). We also ran initial alignment now a total of 3 times without needing to change anything. At the end, Sheila suggested increasing the gain of of LSC_POPAIR_B_RF18 from G = 2 to G = 4. This allowed DRMI triggering to activate a tad earlier than it usually would, which (excitingly) locked DRMI.
Relevant alog: alog 83178. The gain change fix has been commented out. It is on line 564 and 565 on ISC_LOCK.py. The plan is that it will be reverted tomorrow given a solution to the underlying PRMI_ASC not improving.
Other:
LOG:
None.
Ibrahim increased H1:LSC-POPAIR_B_RF18_I_GAIN which is normally 2 during lock acquisition to 4 to get DRMI to lock, as he says. Normally the guardian then adjusts this gain to 3.991 when the 9 MHz modulation depth is reduced, then it gets reset to 2 in PREP_FOR_LOCKING. We commented out the lines in prep for locking that do this reset, but then I remembered that this is also in SDF revert, so I accepted 3.991 in the safe.snap file. And I uncommented the change to ISC_LOCK so that we won't have two places to remember to undo this.
Edited to add one more comment: We also turned off SRC2 P in DRMI ASC to stop a large oscillation. This isn't in the guardian.