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UV Transparent Boiling Flask Search

  1. May 30, 2014 #1
    Hello! First post here, so hopefully I'm not doing anything wrong.

    I've hit a dead end with an experiment and could use some additional perspective. I'm in need of material for a 100 mL round boiling flask that has good transparency down to about 140 -180 nm. I originally considered Type 214 Fused Quartz, but I need a material that will not fluoresce. Pyrex won't fluoresce, but it's only transparent down to about 340 nm. I also cannot afford to purchase the material in bulk, meaning it will likely have to be a material someone has in stock and not made to order.

    Essentially, I need a material...
    • Transparent down to ~140 nm
    • Non-fluorescing
    • Small quantity

    Any ideas for a material (and/or supplier)?

    Thank you in advance.
  2. jcsd
  3. May 30, 2014 #2

    Vanadium 50

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    Will MgF2 work for you?
  4. May 31, 2014 #3


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    What compound does one plan to boil? At what temperature?
  5. Jun 3, 2014 #4


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  6. Jun 5, 2014 #5
    @Vanadium50 I'll look more into it. At first glance it seems like a good candidate, reliant on costs/processability, etc.

    @Astronuc Flask is used to contain single-bubble sonoluminescence at about 4*C, solution variable (generally water)

    @Baluncore We've considered optical fiber, but the one available was only transparent to about 300 nm. I haven't seen optical fibers transparent down far enough for our uses, but one mentioned on that site may work out. I'll look into it.

    Thank you all!
  7. Jun 6, 2014 #6


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  8. Jun 6, 2014 #7
    I don't believe the optical fiber is going to end up working out... would need to fabricate a better mechanism for transmission without messing up the resonances of the system (and without allowing outside materials into the flask, though this is more easily done).

    Fabricating the flask out of ice is very fascinating idea (I'd actually love to try it) but it wouldn't likely be feasible as much of the preparation must be done at room temperature (well, not must be, but I'd rather not move the entire setup to a large freezer). Also, solid ice containing liquid water at 4*C... Not sure what the outcome would be. Melting?

    Sapphire is another great suggestion, and I'll add that to the MgF2 idea. MgF2 also led me to CaF2, which is very similar (not as good, but perhaps cheaper?). The difficulty now is finding someone who is willing to fabricate a flask out of optical lens material... have contacted a number of companies and suppose we'll see (not even sure if it is possible).

    Thanks again for all the help, definitely pointed (shoved) me in the right direction.
  9. Jun 6, 2014 #8


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  10. Jun 6, 2014 #9


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    I imagine a sapphire meniscus lens, as a window, fitted in the wall of a spherical flask. Ground and polished from sapphire, with the concave inner surface having the same radius as the inside of the spherical flask. That will interfere least with an internal acoustic resonance.

    The convex outer curvature might help to focus UV from the spherical flask centre into an external optical system. The bigger the window/lens the more UV will be captured.

    If a second sapphire lens, (with positive curvature), is needed to get a focus outside the flask window, some water from inside the flask, between the two sapphire lenses, might help.

    Rocky Mountain Instrument Co. make sapphire lenses and windows for UV. http://rmico.com/
    Also Crystaltechno; http://www.crystaltechno.com/All_menisk_en.htm
    And there are many others, along with sapphire eyeglass manufacturers.
  11. Jun 9, 2014 #10
    @Astronuc: The UV grade fused silica has a beautiful transmission spectrum. I've asked around quite a bit and maybe something will come of using that. Apparently "exotic glasses" are pretty difficult to find in small quantities, though. Also, we are currently using a photomultiplier, so great minds think alike, eh? We're still looking to push the barrier lower, though--a photon every few cycles is adequate for long term data taking, but we're still missing out where the quartz glass refuses to transmit.

    @Baluncore: I love the idea, since all my leads on making an entire flask out of these crystal materials have been shot down. MgF2 or Sapphire window in a Pyrex, non-fluorescing flask might do the trick. Lots of companies willing to machine different lens shapes--would just have to get them to cooperate with a flask manufacturer (most probably won't want to bother). I also randomly stumbled into a glass that's specifically described as "suitable to sealing to sapphire." Going to look into this more after I get denied my request for small quantity UV grade fused silica.
  12. Jun 9, 2014 #11


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    I see no reason why the flask manufacturer needs to be involved. You can cut a hole in a Pyrex flask with abrasive paste on a tubular trepan cutter. Fit a circular sapphire lens/window into the hole. Seal it with something chemically compatible, maybe silicon rubber, hot melt glue or a flexible epoxy.

    What material is used for the window of your PM tube?
    You might just glue the PM tube into the hole you cut in the flask.

    Alternatively, a dead UV PM tube would provide a low cost UV window.
    Attached is an extract from page 18 of the "Photomultiplier Handbook", Burle.

    Attached Files:

  13. Jun 10, 2014 #12
    We're using a monochromator infront of the photomultiplier, so attaching the PM itself to the flask wouldn't work out. I love the idea of fitting a lens into the flask as a window (dead PM tube lens is a good idea, but probably need something to fit the flask curvature)... I'll put it past some acoustics people and see whether it'll work out.

    Got a quote on a UV grade fused silica flask... low low price of $1600. Going to keep asking around about that... someone's got to have some laying around.
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