corey.gray@LIGO.ORG - posted 17:11, Sunday 26 May 2019 - last comment - 18:18, Sunday 26 May 2019(49457)
H1 Lockloss after 7+hrs: Restoring IMs & Investigating Why ALS Doesn't Look Good
IM Shift & Restoring Pre-EQ
After antoher SQZ unlocking followed by a close H1 Lockloss, took this opportunity to take the IMs to their pre-Peru-EQ values (Cheryl did this...most notable change was Pitch for IM2 & IM3)---this is mainly because the last lock was not great & we're hoping that fixing the IM shifts will help H1.
ALS PDH Errors
On a seperate note, after H1 lost lock, noticed that we do not have any light for ALS x & y (green). On the ALS Overview both X & Y have "ERROR 4 PDH" errors.
This is is what I'm going to look into next. Once through ALS issue, will run a new INITIAL ALIGNMENT to the new IM pointing & see how H1 likes that.
ALS PDH issue is being traced down to GREEN Refl A for both arms having "Power To Low".
So at this point, I'm guessing this is alignment-related. So with Cheryl's help, I'm going to check alignment for TMS', ETMs', ITMs for their alignment pre-EQ.
Earlier today Cheryl and I noted that the ref cav tranmission PD has dropped since the earthquake (now sitting at 1.9V).
Maybe, since the ALS problems are in both arms, this is related? I can start looking into it remotely.
ALS Issue Solved!
My dumb mistake. For some reason both Shutters were closed for ISCTEX/Y green beams---OPENing this gave us light! So, now waiting for signals to converge so I can OFFLOAD and then move on with INITIAL_ALIGNMENT. (Thanks, Georgia & Cheryl for helping!)