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Reports until 22:16, Sunday 16 December 2012
H1 General
robert.schofield@LIGO.ORG - posted 22:16, Sunday 16 December 2012 (4946)
Particulate From New MC Beam Tube Segments

Summary: Fine particulate is visible in all nozzles of the H2 IMC tube, but not in the nozzles of the HAMs near it, suggesting that the particulate came with the beam tube. I measured dust counts during activity in the H2 IMC tube and they were low, about like cleaned chambers. I also looked for particulate that might have moved from the H1 IMC tube into HAM3 and did not find any clear examples. So I think the particulate is fairly stable and it is safe to pump the H1 IO chambers.

A fine particulate was noticed in the LLO IMC tube nozzles (here). Mike L. asked Jodi and I to go into H2 HAM9 and the new H2 IMC tube because there has been very little activity in there and we might be able to find if the particulate came from the IMC tube. The H2 input optics area has not been pumped down since the new tube was installed. Figure 1 contains photos comparing nozzles in the H2 IMC tube and HAM3. The top left photo is of particulate in the 4th vertical nozzle from HAM9. I have drawn a face in the particulate with my finger. I found this particulate in every nozzle of the new MC tube that I examined. I inspected every nozzle of HAM9 and 8 and found none of this type (there were a few isolated  big pieces). Thus this particulate seems to have come in with the IMC tube.

To see how much particulate would be stirred up by activity, I did my scuffing walk test. The level in the MC tube averaged 140 0.5um particle counts per cubic foot, comparable to the cleaned chambers and much better than the ~1000 count levels from walking in the Y-Manifold (here).

Mike also asked me to go in and examine HAM3 to see if the vacuum cycling for leak checking had spread this fine particulate into the HAMs. The photo at the bottom of Figure 1 is a photo of a HAM3 nozzle, showing that there is very little dust compared to the H2 IMC Tube nozzle above it. Also, the few particles seem larger. I sampled the particulate at the HAM3-spool junction for elemental analysis to compare to the samples I took in the H2 IMC tube. I think it is safe to cycle the IO chambers because the particulate does not seem to have spread much – the burden of larger dust particles and especially silver metal particles near optics in HAM3 appears to be worse. 

Robert S., Jodi F.

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