Done at 10:47 AM

The maintenance is completed.

These 2 statements seem contradictory:

"At the highest point, I had readings which would hover between 1500-2500 counts of 0.5um particles.  [At the lowest point ...]  So, it would seem the purge air is relatively clean."

Maybe can John elaborate at where he thinks the high counts are "coming from" if not the purge?  Is it just that the air is turbulent in chamber and stirring up the 1500-2500 counts already in the chamber?

Corey saw high background levels in the beam manifold but was able to drive the particle counts to zero by moving the detector close to the purge port at the floor of the beam manifold. I walked around the VEA sampling and found low levels throughout. Counts inside cleanrooms were close to or equal to zero except at the open BSC door. There was activity here as well as equipment staged. Corey was inside and Keita was outside at the BSC entrance. The overhead work platform reduces the effectiveness of the clean room in this location.  Inside, the arm cavity baffle obstructs access to the beam manifold so any work in the beam manifold requires a person to laydown and slide under the baffle. This may very well abrade clothing. I recommend we establish a horzontal clean flow as we have while working in HAM chambers.

A reminder that the purge air can only provide 25--50 cfm of air flow into the chamber. In a 6 foot diameter tube (beam manifold) this translates to air velocities of only 0.6 to 1.2 feet per MINUTE. Think how far you walk in a minute.

My impression is we have a reservoir of particulate in the vacuum chamber from the series of operations which have taken place - for example there have been two cartridge installs and one removal. Also this cartridge is an early assembly - probably assembled prior to some of the "in process" cleaning steps we have adopted.

Yes, I should elaborate a little (was quickly entering alog during Morning Meeting).  So we did measure counts while I was in BSC10.  And seemed like we had steading counts in the several thousands [for 0.5um counts with continuous sampling].  When I took measurements along the Purge Air plume, I would get up to 2500 at the most at the top of the plume (6' high).  As I went closer and closer down to the Purge air inlet, the counts started to drop.  And it was zero right at the inlet.

So the picture looked as though we have a baseline of particles floating in the chamber.  And in the turbulent air above the Purge Air inlet the counts waiver a bit, but counts decrease the closer you are to the inlet.  So above the purge we have particles moving around more (vs further away from purge these particles are more "statically" floating...perhaps they are more on the floor when someone like me isn't shuffling them into the air).

Basically we have particles all over the surfaces in the chamber/tube.  They may be gently floating around or resting on the floor.   They get rustled around when we work in-chamber & also get blown around and away from the Purge Air inlet.  We need to remove these particles...which I know is obvious and daunting. 

We're going to coninue wiping these particles on the floor toward door, but not sure what that does.  Hopefully, particles get attached to our wet wipes, but I wonder if particles just get pushed to the edge of the floor and then fall over the edge of the temporary floor and then rain down to the bottom of the chamber.  Sad sad.

Are these raw or normalized counts?

Here're the promised, associated spectra. I attach an annotated version of the BLRMS too, with vertical lines demarcating the UTC time in the same colors as the traces on the spectra.

As indicated by the legend, I chose representative times that reflected the variety of ground motion:
2014-03-16 15:45 UTC - High micro-seism
2014-03-16 18:05 UTC - High micro-seism + Gusty Wind
2014-03-16 21:45 UTC - High micro-seism + Large Earthquake, in Chile + Gusty Wind
2014-03-17 05:50 UTC - Medium micro-seism + Cluster of Small Earthquakes (Chile, Again in Chile, Philippines, Puerto Rico, and Mexico, at magnitudes 6.2, 5.0, 5.1, 3.0, and 2.8 respectively).
2014-03-17 18:45 UTC - Low micro-seism + Gusty Wind

Notes:
- While we don't necessarily expect to be able to stay up during large earthquakes, it's good to see a sort of upper bound, and the contrasting color of the ground motion as it fills in the 30 to 100 [mHz] band. 
- It's interesting to see that during periods of high microseism, the peak at 55 [mHz] seems to be present regardless of whether the winds are gusting or not (comparing BLUE and RED) .
- Further, there exists times (i.e. MAGENTA) where there is lots of gusting winds, but the microseism is relatively low.
- Most importantly we see that ground is sort of oscillating between requiring more isolation in the 30 to 100 [mHz] band and in the 1 to 10 [Hz] band.
- The variations in the 30 to 100 [mHz] band can be as much as a factor of 100 during earthquakes, but not too much change between windy and not windy, maybe at most a factor 5 in a small range between 40 and 80 [mHz].
- There's very little to no change in the region of the lowest SUS resonances between 0.2 and 0.6 [Hz] between all of these seismic bad times
- Naturally, gusty wind times are the worst at high frequency, but again the variation is only a factor of 3 to 4. We should be able to ride this out.

Let's see what the HEPI L4Cs say, maybe the gusts have an interesting affect playing with the pier flag poles.

J. Kissel

Here're the HEPI L4Cs for each of the times described above. While they show the same sort of variety at the microseism and below (where they can sense the ground motion above their self-noise), the most interesting is how much more varied the tilt spectra are (in this case RY) in the 0.3 to 1 [Hz] band -- exactly where the translation degrees of freedom claim there's very little difference. And naturally the ITM reacts differently than the ETM, just to make things difficult.

For ITMX, both high microseism conditions and gusty wind show elevated tilt in the 0.3-1 [Hz] band, by about a factor of 10. Only the during the medium microseism + small earthquakes did the L4C hit it's (tilt) noise floor.

For ETMX, there's quite a variety, with gusty winds alone being the worst-case scenario.

But the moral of the story is that, where translation degrees of freedom get tossed around by an order of magnitude between 0.03-0.3 [Hz] and 1-10 [Hz] during these excurisions, the tilt fills in the 0.3-1 [Hz] gap with its own order of magnitude variation, and as we know *both* tilt and translation of the table affects the optics just about equally. 

So -- if we want to operate the isolation systems during these 90th percentile times, we're gunna have a lot of automation and blend tailoring to do, but just increasing the blend frequency won't necessarily win. Further, when we *do* #movetheblendup, the green still can't handle the loss in performance.

The data for the above measurements can be found in the following templates:
/ligo/svncommon/SeiSVN/seismic/BSC-ISI/H1/Common/Data/
2014-03-16to17_GroundMotion_ASDs.xml
2014-03-16to17_HEPIPierMotion_ASDs.xml

There's way to many curves for me to export, but all curves shown are stored as references so you can export them at your leisure and use them in any models.
                          Ground Motion           Pier Motion
2014-03-16 15:45 UTC       Ref.   0-11            Ref.  0-23
2014-03-16 18:05 UTC       Ref.  12-23            Ref. 24-47
2014-03-16 21:45 UTC       Ref.  24-35            Ref. 48-71
2014-03-17 05:50 UTC       Ref.  36-47            Ref. 72-95
2014-03-17 18:45 UTC       Ref.  48-59            Ref. 96-119

All plots and templates are committed to the repository as of this entry.