Ibrahim, Betsy, Anamaria
Upon first in-chamber BBS01 inspection, we found 3 large clumps of spots approximately 100mm from the edge. We're consulting GariLynn at CIT for steps on how to clean.
Acetone swab: We tried to go over the spots with a cotton swab with acetone, but the spots remained.
First contact: We then tried to first contact a small portion with one thin layer, but the spots remained.
While there's no evidence that the beamsplitter was contacted, dinked, touched or scratched in anyway, this might be a cause for the damage. There is texture to the spots upon brushing them with a swab and while it seems more likely that these are above the surface, we are not totally sure.
Hypotheses (and their problems)
1. Peek In-Vac cable scratch: maybe an in-vac cable fell on that area but they would have had to imprint multiple times with some force to show something like this.
2. Falling foil: maybe a piece of foil fell onto the surface and scratched it that way? No foil was used or wrapped at height during BBS and again, the foil would have had to fall with some heft.
3. There-the-whole-time: Maybe the spots were there the whole time and are invisible to non-chamber conditions. Because this is on the AR side, there is no good scatter plot of the surface. Since we did not see this in normal light conditions, but immediately saw this in chamber (dark) conditions, this may have been there all along. The spots are quite large (as attachments show), so this makes that less likely.
4. Dry first contact: Maybe it's dry first contact? We went over some of the spot with acetone but it stayed. We also first contacted a thin layer on one part but it stayed. The nature of the spots do look like they're small first contact bubbles. We found the first contact sheet that we used on that side and indeed, there are some similar streaks in size but nothing conclusive. We're looking at matching the spot with the first contact to see if there is a streak in this region. Problem is - first contact wouldve come off quick with the acetone treatment. So this is also not likely it.
What to do next:
- Analyze with Dino-Lite: We're going to zoom in on the spots with our DinoLite mount to get a better look. This could tell us if they are truly scratches or stuck particulate.
- Match first contact sheet with spots: Seeing if these spots were visible during FC (done on May 6) - alog 90149. Nothing visible.
- Anamaria suggested at any rate shining a gaussian beam at it to analyze the damage in a short experiment to characterize.
Ibrahim, Betsy
First, we imaged the spot, which yeilded these attached pictures of what look like... specks. No idea what these may be.
We then went over the spot with some thicker first contact, which did not remove any of the specks.
We recieved the procedure for spot-water cleaning which is the only last thing that we're thinking of trying.
In the attachment, the thinner lines are dry acetone and can be removed. Focus on the brighter dots instead.
Also adding a "map" of our AR side features thus far. I will digitize it and add this as an alog/DCC of its own once we're done with optic inspection.
