Some more numbers we found while working in/around the chamber today:
Particle counts
| Area |
0.3 micron count (per cfm) |
0.5 micron count (per cfm) |
| Vacuum chamber (vented) ITMY |
~5000 |
~600 |
| HEPA enclosure on ITMY door |
<100 |
0 |
| Lab |
~100,000 |
~6000 |
These numbers were measured using our particle counter, which has a pump rate of 0.1 cfm, so the numbers above are 10x the numbers shown on the instrument after a measurement to account for this.
Essentially, the chamber is pretty dirty. Peeling the F.C with hard to reach optics like the ITM installed in place is not really feasible, and after peeling the F.C, we are looking at a best case of an additional 1-2 weeks in air to align the IFO, during which the optic is apparently exposed to quite a lot of particulates. In fact, with the high intensity flashlight left on, I actually saw some flecks of dust occassionally floating around inside the chamber while I was working on the optic. But this is just something we have to accept I guess. |