jeffrey.bartlett@LIGO.ORG - posted 06:30, Thursday 02 March 2017 - last comment - 18:41, Saturday 04 March 2017(34526)
PSL Reporting Low Temp
At 14:19 (06:19) received alarm that PSL A/C was on or Low Temp in Laser Room. The PSL South temp is 69f, the PSL North temp is 70F. The PSL Table North is 73f. The PSL Table South is 71F. The Dust Monitor #101 under the table is reporting 69f.
Comments related to this report
jason.oberling@LIGO.ORG - 10:48, Thursday 02 March 2017 (34538)
Here's a couple of trends around the relevant time. The first attachment shows all 4 PSL Enclosure laser room temperature sensors. The channels labeled *_ACS_* and *_ACN_* are the sensors at the output of the enclosure AC units, which are turned off during normal operation; the channels labeled *_TBLN_* and *_TBLS_* are the sensors attached to either end of the PSL table. The second attachment shows the south AC sensor (*_ACS_*) and the TPD signal from the FSS RefCav; I used the RefCav TPD as this has shown to be one of the more temperature sensitive alignment in the enclosure. As can be seen, as soon as the temperature begins to dip, the TPD signal becomes more jagged and begins to drop. This is consistent with a real change in temperature in the PSL enclosure. We are currently mystified by this behavior, as the AC units were both off during this time.
Similar behavior was reported by Travis yesterday, and again both AC units were off during the temperature dip. At this time we have no explanation for this behavior. Investigations continue and will update as we know more.
Images attached to this comment
john.worden@LIGO.ORG - 14:42, Thursday 02 March 2017 (34549)
There is a fan in the LVEA return air plenum which continually pushes air into the PSL enclosure even when the AC units are off. This fan is behind the east wall next to the PSL. It would be worthwhile to find out what the temperatures are doing in that space. This return air space is much larger than the supply ducting to the LVEA and therefore the flow velocities are low and there may be air currents driven by convection. Also, winds will have the effect of pressurizing one side of our building with respect to the other side - this may also drive air currents in the return air plenum. Is there a correlation with wind conditions?
I do not know of any temperature sensors in the plenum.
jim.warner@LIGO.ORG - 18:41, Saturday 04 March 2017 (34579)
It looks like something was changed on March 1st at about 20:00 UTC. PSL-ENV temp trends show a marked difference in behavior since then, see attached trends. It would be good to figure out what has happened because the temperature dips correlate with extra motion in the IMC, and we have lock losses that follow the temperature dips. Maybe not causal, but it looks like something is not nominal.
Here's a couple of trends around the relevant time. The first attachment shows all 4 PSL Enclosure laser room temperature sensors. The channels labeled *_ACS_* and *_ACN_* are the sensors at the output of the enclosure AC units, which are turned off during normal operation; the channels labeled *_TBLN_* and *_TBLS_* are the sensors attached to either end of the PSL table. The second attachment shows the south AC sensor (*_ACS_*) and the TPD signal from the FSS RefCav; I used the RefCav TPD as this has shown to be one of the more temperature sensitive alignment in the enclosure. As can be seen, as soon as the temperature begins to dip, the TPD signal becomes more jagged and begins to drop. This is consistent with a real change in temperature in the PSL enclosure. We are currently mystified by this behavior, as the AC units were both off during this time.
Similar behavior was reported by Travis yesterday, and again both AC units were off during the temperature dip. At this time we have no explanation for this behavior. Investigations continue and will update as we know more.
There is a fan in the LVEA return air plenum which continually pushes air into the PSL enclosure even when the AC units are off. This fan is behind the east wall next to the PSL. It would be worthwhile to find out what the temperatures are doing in that space. This return air space is much larger than the supply ducting to the LVEA and therefore the flow velocities are low and there may be air currents driven by convection. Also, winds will have the effect of pressurizing one side of our building with respect to the other side - this may also drive air currents in the return air plenum. Is there a correlation with wind conditions?
I do not know of any temperature sensors in the plenum.
It looks like something was changed on March 1st at about 20:00 UTC. PSL-ENV temp trends show a marked difference in behavior since then, see attached trends. It would be good to figure out what has happened because the temperature dips correlate with extra motion in the IMC, and we have lock losses that follow the temperature dips. Maybe not causal, but it looks like something is not nominal.