jeffrey.bartlett@LIGO.ORG - posted 12:08, Wednesday 04 November 2015 - last comment - 17:06, Wednesday 04 November 2015(23108)
Ops Day Mid-Shift Summary
Not a generally good morning.
IFO broke lock at 16:16 (08:16). After running initial alignment; relocked the IFO and went into Observing mode at 18:25 (10:25). Shortly after relocking started seeing a lot of RF45 noise events at a rate of several per minute. It was decided to have Evan & Filiberto to go into the LVEA to check the RF cabling.
While Evan & Filiberto were in the LVEA working on the cabling, the IFO dropped lock. Waiting for them to come out before relocking.
RE lockloss at 8:16.
Bubba and I were turning on a few heaters and one of these feeds the output arm (HAM5-6).
The plots show duct temperature near the heater, zone temperature near the floor, and 10 days of zone temperatures.
I have multiplied the Observation_Ready bit by 70 to get it on the same scale as the temperature.
Coincidence?
Robert suggested that looking at the OpLevs could give an idea as to if this lockloss could be caused by the temperature. I trended the OpLevs and compared their motion with the LVEA temperatures, and there is definitely some correlation seen on the SR3 OpLev movements and the temp of the LVEA. You could probably make an argument for ITMY and PR3 OpLevs as well, but it is not as clear as the SR3.
So was this temperature excusion the cause of the lockloss? Well, the ASC signals didn't seem to be showing any signs of a problem before lockloss, seismic activity was low to minimal, winds low to minimal, and I didn't see any other obvious culprits.
I attached a trend of some of the CS OpLevs and LVEA temp in a 6 hour window, as well as a group of Lockloss plots with ASC signals and such.
If air temperature was a factor in this lockloss I would be suspicious of electronics outside the vacuum near HAM5 or 6. I would not expect in-vacuum hardware to respond so promptly.
[JeffB, Jenne]
After some closer looking, we don't think that the temperature was a direct cause of the locklosss. By the time the lock was lost, the temperature in FMC-ZONE4 had only changed by a few tenths of a degree - well within our regular diurnal temperature changes. About 16 seconds before the lockloss, SRC2 Pitch and Yaw both started walking away. I don't know why they started walking away, but there's probably nothing to so about this, other than eventually move the SRC ASC from AS36 to some other signal, as we're planning to do after O1 anyway.