anthony.sanchez@LIGO.ORG - posted 08:00, Wednesday 16 October 2024 - last comment - 09:45, Wednesday 16 October 2024(80704)
Wednesday Ops Shift Start
TITLE: 10/16 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Corrective Maintenance
OUTGOING OPERATOR: TJ
CURRENT ENVIRONMENT:
SEI_ENV state: CALM
Wind: 4mph Gusts, 2mph 3min avg
Primary useism: 0.02 μm/s
Secondary useism: 0.27 μm/s
QUICK SUMMARY:
TJ was up all night damping Violin modes!
When I walked in IFO was Unlocked and struggling to lock green arms.
Relocking:
I've Requested Inintial Alignment.
Locking Notes:
Initial_Alignment went smooth, DRMI_1F locked quickly:
ISC_LOCK got past DHARD_WFS and immediately I_X Saturations started to happen.
We noticed that the Saturations were coming from the ITMX L2 stage.
Sheila spotted the fact that the Coil Drivers were in the wrong state.
H1:SUS-ITMX_BIO_L2_UL_STATEREQ = 3
H1:SUS-ITMX_BIO_L2_UR_STATEREQ = 3
H1:SUS-ITMX_BIO_L2_LL_STATEREQ = 3
H1:SUS-ITMX_BIO_L2_LR_STATEREQ = 3
But they needed to be in state 2 instead!
Sheila stopped me from just quickly changing that 3 to a 2, which would have broken the lock.
Apparently Shelia relieved one of the Coil Drivers from driving, and then changed the state of that Coild Driver while it was not driving. Then turned that coil driver back on and rotated it back into driving with the restof the Coil Drivers. The she would rotate another Coil Driver out of driving to update the state. Maintaining at least 3 coil Drivers at a time.
Apparently there is a matrix change from driving with all 4 Coils to driving with 3 coils.
Then change the ramp time and value from 3 to 2, then change the matrix to rotate through all 4 coild drivers to "free" a different coild driver from driving. is the procedure that kept our lock. Please see Sheila's alog.
We believe that there was a change to Prep_for_locking that is supposed to update the state of the coild drivers before locking.
P.S.
We turned the Softloops off to deal with the above, and we sat in POWER_25W but we only had 10Watts, because softloops were turned off and we forgot to turn them back on. But it gave Rahul time to Damp Violin modes, which is good because the violin modes do seem big red and mad.
Violin modes are now damping down nicely using the nominal settings for 2W. I have ramped-up the gains for few of the modes in all four optics which will enable to calm them down faster. Later will move to damp violins at full power.