Sheila Craig Georgia Hang
This evening we continued trying to improve the CARM handover from ALS-COMM to LSC-TR, following on from last night's work (alog-43190).
We fixed an error where the LSC-RELFBIAS input matrix elements were left on, and now the the arm transmissions (LSC-TR_X and Y) are much quieter at the CARM_TO_TR step. We retook the TR_CARM open loop transfer function which looks better than yesterday. We tried skipping the step added yesterday which brought the arms to a 100Hz offset in the PREP_TR_CARM before handing over, but found this step was necessary to find the IR.
We went to the next guardian state: REDUCE_CARM_OFFSET, and could not maintain this for very long before losing lock (after ~1 minute).
We tried to get to the DARM_TO_RF state but found the ETMX HEPI tripped, it looks like there might be a timing error as the watchdog trips before the tidal monitor saturates. The sensor in this stage of locking is ASC-AS_A_RF45_Q_SUM_OUT16, which is not a DQ channel, it would be handy to store this channel so we can look back at the locklosses.
Here is a plot of some of the channels that caused HEPI to trip when we tried the transition to RF DARM. The second plot is zoomed in in time around the lockloss, and shows that the timing is confusing. It should be that the first thing that happens is the large impulse in DARM (because we tried to transition to an error signal that wasn't good), then a low passed version of this should show up in tidal channels, and an even more low passed version shoud show up in the HEPI channels. Instead it seems that the signal shows up in HEPI first.