TMS Work (Corey, Jax, Keita, Margot)
Apollo roughly positioned the ISCT-EY Table (via floor markings).
Chamber Floor was first cleaned upon entry for work (did not do an exit floor wipe). Margot then entered the chamber to remove First Contact from inside surface of pair of TMS Viewports (then went out and removed First Contact off outer surfaces). She mentioned "finger prints" on the outside surface of one of the TMS viewports; Margot will document in the DCC.
By eye, we checked position of the table, we ended up pushing the table about 3" west. We then attached ducting between the chamber and the table. Then we went in to check our line of sight from the TMS Table to the Table Periscope. This required us to move the GREEN periscope an inch east, and also the top periscope mirror down 4-6". At this point the laser wasn't quite making it down the ductThis is about where we ended things last evening.
Dust Monitor Check Of Purge Air For BSC10 (Corey, John, Keita)
John whether there was dust coming from the purge air. So I, with handheld Dust Monitor in hand, crawled under the ACB, and took a few measurements from the Dust Monitor (which was running continuously). I took measurements at four spots above the input of the purge air. At the highest point, I had readings which would hover between 1500-2500 counts of 0.5um particles. At the lowest point (with sensor of Dust Monitor right at the input), the 0.5um counts could be kept at basically 0-counts (with flashes of a few hundred possibly. So, it would seem the purge air is relatively clean.
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.