Temperature differences on the PSL table are of interest because of the potential for producing beam jitter through thermally driven air currents (https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=31190, https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=31263)

During PEM injections, Anamaria and I measured temperatures on the PSL table at LLO to compare to LHO temperatures, measured previously. The table below compares hot spots that were several degrees warmer than the PSL table, at least at one site, and close to the beam path.  The PMC, for example, is not included because the outer surface of the tank was not several degrees warmer than the PSL table at either site.

Starting CP3 fill. LLCV enabled. LLCV set to manual control. LLCV set to 50% open. Fill completed in 23 seconds. LLCV set back to 18.0% open.
Starting CP4 fill. LLCV enabled. LLCV set to manual control. LLCV set to 70% open. Fill completed in 369 seconds. LLCV set back to 34.0% open.

Since there looks to have been some EQs last night, I'm going to attempt remote login to reset things.

-Betsy (and JKissel consult)

1120 - 1125 hrs. local -> Kyle in and out of the LVEA 
1135 - 1140 hrs. local -> Kyle in and out of the LVEA 

Valved-in locally mounted turbo to PT180. Should know in a day or two if the indicated pressure value will "drift" up while the gauge is pumped by the turbo and not exposed to the site vacuum volume.  

Also, I witnessed the truck driver decouple and store the transfer line following the LN2 delivery to CP3.  He installed a plug to, at least, one end of the transfer line before storing it - I assume the other end was also plugged.  

Cylinder pressure of UHP N2 bottle holding pressure to CP4's clogged sensing line is @ 1500 psi while the flow meter indicates no flow.  The regulator output is set for 20 psi and the flow meter is limited to 0.4 LPM.  

Starting CP3 fill. LLCV enabled. LLCV set to manual control. LLCV set to 50% open. Fill completed in 20 seconds. LLCV set back to 20.0% open.
Starting CP4 fill. LLCV enabled. LLCV set to manual control. LLCV set to 70% open. Fill completed in 29 seconds. LLCV set back to 34.0% open.

1220 - 1230 hrs. local -> Kyle in and out of LVEA  

Will resume pumping the isolated PT180 gauge soon to continue our long-term "gauge drift" data collecting.  Found LVEA lights on and, thus, turned them off when leaving for "sustainability" reasons ;)  

Also, manually confirmed that CP3 and CP4 had been filled via script -> they are full.   

hand-off run of the CP3,4 autofill scripts completed quickly. Now waiting for robo-alog report at 12:10

Starting CP3 fill. LLCV enabled. LLCV set to manual control. LLCV set to 50% open. Fill completed in 20 seconds. LLCV set back to 20.0% open.

Starting CP4 fill. LLCV enabled. LLCV set to manual control. LLCV set to 70% open. Fill completed in 29 seconds. LLCV set back to 34.0% open.

The PSL tripped off this morning, interlocks indicated a loss of flow in the laser head water circuit.  After restarting the laser from home, I drove out to the site to check a chiller alarm (that turned out to be a low water level alarm), and ended up having to reset the noise eater as I recovered the PMC/FSS/ISS (as usual when recovering from a trip).  The laser is now back up and running in the same state it was left in on Thursday.

The whole valve stem was covered with ice, see photo, so I moved the light from CP6 to CP5 and left it on.

h1tw0 (secondary minute trend writer) started having RAID issues again beginning at 05:35 PST this morning. Its been in a start-stop-restart cycle ever since. I've turned off monit on h1tw0 to stop it respawning. We'll rely on h1tw1 for the rest of the holidays.

It appears as if CP6 LLCV valve stem is frozen again, I'm at the site looking into it.

As noted previously, alternating between pressurization of the clogged line followed by applying a rough vacuum, results in gas generation on the atmospheric side (gauge side when connected to the gauge) of the obstruction results.  My initial, optimistic, interpretation was that the ice plug was getting "drawn" slowly up the sensing tube and making contact with relatively warm surfaces, thus melting the leading portion of the plug.  Considering the repeatable phenomenon of watching the gas pressure build up on the gauge only to have it fluctuate as if the accumulated gas was being released via some unknown path, I now have a new, more pessimistic, picture in my head (see attached sketch).   Maybe the ice plug is irregular in shape and not it complete contact with the large diameter aluminum tube wall such that it gets rocked, cocked, tilted etc. by the pushing and pulling of applying pressurized UHP N2 followed by vacuum pumping.  If this is happening then small amounts of LN2 can leak past and turn to gas and this is the source of the gas not the vanishing ice plug.  Since the gauge end of the sensing tube is closed, the pressure build up of GN2 can then escape past the ice obstruction back to the LN2 side.  This is consistent with the observations.  Note in the sketch that water ice is denser that LN2 and would be expected to concentrate at the bottom of the pump.  Also, once formed, it has no place to go.  It is too big to enter into the small I.D. of the SS sensing tube or make it past the "hard" 90 degree aluminum tube elbow.  

My wife thinks I'm Christmas shopping!

Starting CP3 fill. LLCV enabled. LLCV set to manual control. LLCV set to 50% open. Fill completed in 21 seconds. TC B did not register fill. LLCV set back to 20.0% open.
Starting CP4 fill. LLCV enabled. LLCV set to manual control. LLCV set to 70% open. Fill completed in 18 seconds. LLCV set back to 34.0% open.