Today we managed to realign the cameras on HAM6 which show OMC TRANS and AS AIR. At first we could not see any response from the AS AIR camera so there were some cable swapping back and forth, reseating of cables and a few reboots by Dave B/control room. At some point it started working again.
In any case, beams are now on these cameras.
Vicky, Jennie, Swadha,
After the camera was aligned we realised the 1mA mode Vicky and I were locking the OMC to on Friday was a 1/0 mode. This explains why we were having problems getting the yaw ASC on the OMC to converge as the cavity alignment was off in yaw.
We then scanned the PZT2 until we saw TM00 on the camera and could see error signals on the input to the LSC servo then tweaked the OM1 and OM Sus alignment until the mode height was maximised at 2mA.
We were not sure if ASC was working - even with a nice TM00 mode and all the offsets on the QPDs altered so the outputs of each ASC_QPD_{A,B}_{PIT,YAW}_{OUTPUT} were 0. We also tried gain flips and we found a stable situation for ASC, but didn't check if it was really locked. The stable situation (ASC not railing) was sign flips on both yaw gains for the OMC-ASC_{POS,ANG}_X_GAIN and OMC-ASC_{ANG}_Y_GAIN. We reverted the changes we made except for OMC-ASC_{POS,ANG}_X_GAIN.
Attached is a nice lock stretch as an example of how good a mode we could get after Swadha tried to tweak up the alignment of OMC and OM3 (the nominal for earlier mode scans was a locked level of 3mA on the DCPD_SUM_OUPUT).
Below are the reference values for calculating the loss
Locked 1.3659 mW at 1:29:18 UTC for OMC_REFL_A_LF_OUTPUT
Unlocked at 4.25555 mW 1:40:47 UTC for OMC_REFL_A_LF_OUTPUT
2.16955 mA at 1:30:07 UTC for same lock stretch on DCPD_SUM_OUTPUT
(REFL channels are noted as calibrated in mW on OMC.adl screen, think DCPD_SUM is calibrated in mA).
Scan starts 2:05:27 UTC 200s. Using tamplate Feb26_2024_PSL_OMC_scan_coldOM2.xml in /userapps/sqz/h1/Templates/dtt/OMC_SCANS
Second image is the scan we took.
Screenshot of OMC LSC locking and relevant signals attached. The OMC LSC capture range is quite small, so likely last week we were trying to lock LSC while not being in range of the LSC error signal. Scanning OMC PZT2 in step sizes of 0.1, looking for the LSC_I error signal into the OMC LSC servo, then locking the LSC servo loop, worked.
Just to clarify scan started at 2:05:27 UTC on 2024-02-27 and template runs two 100s scans up in voltage.