Suggestions for 200-600 nm range transmitting polymers/materials

I am a student of physics who is doing research related to Cherenkov measurements. For that purpose, I need suggestions for some materials that have the following properties:


* $80\%$ transparency in the range of $200$-$600$ $\mathrm{nm}$
* Low scintillation light produced from electrons
* Relatively lower density
* A high refractive index


Some materials in this regard that I have tested are PMMA, TPX, NAS, LURAN, TOPAX, and Plexiglass. I want to test more materials to see if something does better; what polymers or other materials might I try to achieve these properties?




**No plastic of any practically useful thickness$^\dagger$ has $80\%$ transparency down to $200~\mathrm{nm}$. Period.**


Below is a UV transmission chart for various materials from a marketing brochure published by [BrandTech](https://www.brandtech.com/), a manufacturer of disposable UV/Vis cuvettes (click image to enlarge):


[![cuvette plastic transmittance curves](https://i.stack.imgur.com/VSUTTm.png)](https://i.stack.imgur.com/VSUTT.png)


The chart only goes down to $210~\mathrm{nm}$; extrapolating the trend, not even *quartz* is $80\%$ transparent at $200~\mathrm{nm}$, but it's probably a decent choice for your purposes as long as it sufficiently meets your other criteria.


Beyond that, [fluorite](https://en.wikipedia.org/wiki/Fluorite) $\left(\ce{CaF2}\right)$ is the only specific material I know of with better UV transparency; it appears to have better than $90\%$ transparency down to around $200~\mathrm{nm}$ (figure is from [ThorLabs online catalog](https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=3978)):


[![CaF2 transmission curve](https://i.stack.imgur.com/RdrOF.png)](https://i.stack.imgur.com/RdrOF.png)


A chart at that ThorLabs link indicates two additional candidate materials: [$\ce{MgF2}$](https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=5582) and [sapphire](https://www.thorlabs.com/NewGroupPage9.cfm?ObjectGroup_ID=3982). As with quartz, the choice among these will boil down to how well they meet your other criteria.




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**$^\dagger$ As a caveat to the above:** If a very thin plastic film ($\leq 100~\mu \mathrm{m}$ or so) is acceptable, a specialty material might give sufficient transmittance. You would have to convince the manufacturer of such a material to make it for you, however, which would probably not be trivial, or cheap.


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