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Registered Member #358
Joined: Sat Apr 01 2006, 06:13AM
Location: UCSB
Posts: 28
Hey,
I'm working on designing some nonimaging light conentrators (winston cones and the like) for a physics lab at UCSB. I've been looking around for sources of high refractive index plastics (they've got them up to 1.74), but haven't had luck finding any. Have any of you guys messed with this stuff, or know where to get it?
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
I think you might have to make your own polymers though I'm surprised I can't find a supplier on the net. I take it you know that you are looking for things like polyvinylnaphthalene and such. Another thought that struck me was that you could (with, I accept, some difficulty) produce a fused quartz "cup" that would act as a mould for any polymerisation but could also be filled with a liquid with a high index. Much easier to experiment with than cutting and polishing polymers to shape. I think you would need to use the refractive index of the quartz as a "scaling factor" of some sort- quartz has a fairly low index, something like MgF2 would be better but more difficult to make. The top picture here is something like what I mean but you would need one machined to exactly the right shape.
Registered Member #358
Joined: Sat Apr 01 2006, 06:13AM
Location: UCSB
Posts: 28
Can you coat the sides with a silver or gold layer like a CD to help?
Yes, we can coat them with a reflective surface, but there are a couple reasons to avoid it. One is just the hassle of doing it, and the other is a 5-10% loss, depending on how good the coating is. We want a high index of refraction so that we can use total internal reflection, which is just about lossless, and because there is an n^2 term in the maximum possible concentration.
The big picture in the project is to quantify the number of high energy neutrons down 2000m in a mine, so people looking for dark matter know what kind of backround noise to expect. The light cone is a small subset, so we'd like to stay away from synthesizing our own polymers, and doing generally complicated stuff. Polycarbonate (n=1.58) may be our best bet.
I take it you know that you are looking for things like polyvinylnaphthalene and such.
No, I didn't. All I could find was trade names like "hyper index 1.74", which is kinda useless.
We've done some thinking about using liquids, but we'll see.
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High refractive index plastics and nonimaging light concentrators
