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Thread: Bagel mode

  1. #1
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    Default Bagel mode

    Bagel Mode is where there is no power in the core of the beam and is made by mixing Tem10 and Tem01. Does anyone know a way to do this without mixing modes? I need to do this with acoustics as a set of standing waves for a particle trap in a moving fluid system. I want sizes not desired to pass through the core but those in the size fraction select to get trapped. I then plan to slightly change the beat and move them down the fluid to a collection pick off. I know how to do this in a static system but need it in a flowing system. Still low Reynolds numbers relatively slow flow. A sort of modified stokes trap. I am aware of the cell sorter methods. That’s not what I’m after. Looking at around 2-10mhz ultrasonics. Thinking to do this by setting up a standing wave interference between two or more sources. Just not sure how to make the 3d structure with superposition. Think of a bagel rolling inside out like a solid rubber tire making a zone of pressure that selects and traps particles. Now that moves like a belt through the system. Just how to make such a construct? The math for the selective trapping I already know regarding shear and induced drag. That’s sound physics and in use in many industries. Just how to form the standing wave in bagel mode and move it spatially is unknown. I’m only trying to do this in a 1/4” dia pipe so the system need not be very powerful. If I can make it work I might try other modes for mixing. Application at moment is sla resin cleaning. Having issues regular filtering can’t seem to solve with partially cured resin that spoils the parts. Want to actively filter the resin and keep it mixed while sitting in the tray. Physical particles removal won’t work as there is a desired particle and an undesired. Might also apply to dye lasers.

  2. #2
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    ... if the beam has a Gauss profile, then send it through a short fiber, focus it, and check the profile before and after the focus distance - have seen something like your "bagel" with some setups ...

    Viktor

  3. #3
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    Sounds like you need something like an acousic axicon. Don’t know if they exist for your application, but this paper might have some useful info on a possible approach using metasurfaces:

    https://www.nature.com/articles/srep02546#f5

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    Quote Originally Posted by CountFunkula View Post
    Sounds like you need something like an acousic axicon. Don’t know if they exist for your application, but this paper might have some useful info on a possible approach using metasurfaces:

    https://www.nature.com/articles/srep02546#f5
    That looks very promising thank you. I needed a method for control and this might be it.
    ok read it. The function I need is the exact reciprocal of that. I want to confine the power so that looking at a cross secti9n it’s zero at the wall rises to a max and the falls to zero at the center. It should make a rotating bagel of fluid. This is then a standing wave series that by phase or frequency shift can be moved spatially in the pipe.
    Last edited by kecked; 08-26-2018 at 13:13.

  5. #5
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    Lightbulb

    Beam-shaping optics? (See attached)

    Adam

  6. #6
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    Acoustic Axicons do exist. In fact there is an even easier method. I'm under an partially expired NDA for parts of this topic not related to particle capture, so I'll reply to my friend in private. Kecked, I'm on the road the later half of the week and will call to discuss your application within what I can tell you. CDA is the way to go and is a well known phenomena n physics and acoustics , well, except to Google.

    Steve
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