Present: BobT, Erik, Don, Sasha (in the room). Manny (on the phone)
VVS prototype We finally got engenneers to work on drafting of veto prototype. Erik is pushing to buy scintillator and fibers ASAP. Dan brought a quote from Bicron: 18"x27"x5mm sheet cost $495. We need 55 of them or 27k$. We need to know length of fibers to purchase them as well (we want to buy straight pieces).
Fiber routing It's a serious problem, Erik spent 15 minutes near the whiteboard trying to explain how the fibers would go. It's really pushing my 3d imagination beyond the limits. Fibers cross and it is not clear how to organize them. Don sugested a "wooden" prototype.
Minicookies There was an
interesting suggestion from Don to organize fibers from each tile into
mini-cookie in hexagonal shape. Interestingly enough you need 19
entries to make hexagon and we may have 18 fibers in the tile. So
then you don't have to fight with this mess of hundreds of independent
fibers but pick minicookies and stack them together. It correlates
nicely with ideas of splitting cookies into subcookies suggested by
Manny on his last visit.
Plastic thickness tolerances Plastics sheets have different thickness. The tile can be for example thinner on the outer radius. That would lead to "splay" of tiles. We want to require that the splay would be less than thiickness of 1 layer for all 80 layers.
For cast scintillator errors add randomly, so tolerance 0.2mm*sqrt(80) = 1.8 mm seems to be adequate. (Tolerance 0.2mm is a quote from bicron - Dan)
For molded scintillator errors add linearly , so tolerance 0.02mm*80 = 1.6 mm seems to be adequate. It is probably achievable (0.001") but we have to confirm that.