BTI-PND dosimeter microbubble formation when overheated

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Andrew Seltzman
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BTI-PND dosimeter microbubble formation when overheated

Post by Andrew Seltzman »

Zan has recently observed an effect (viewtopic.php?f=18&t=10763&start=20) where localized micro bubbles form when a dosimeter is overheated, this effect has been confirmed. An old BTI-PND was heated with a heat gun causing localized formation of microbubbles in the heated area. Surprisingly you can hear the bubbles forming with an audible snapping/popping noise. The dosimeter has to get pretty hot to the touch for this to happen.

Video of bubble formation
https://www.youtube.com/watch?v=LXZgcVG ... e=youtu.be


Dosimeter before heating
SAM_5334.JPG
Dosimeter after heating
SAM_5339.JPG
SAM_5342.JPG
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Dennis P Brown
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Re: BTI-PND dosimeter microbubble formation when overheated

Post by Dennis P Brown »

Wow, good post; I understand those things are very expensive and knowing this can save many people from having this happen to their detectors. Shielding is important; a standoff piece of aluminum foil might do a good job as a thermal shield. Also, keeping the detector protected from thermal convection would be important, too. Those pics really drive home those issues rather dramatically.
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Re: BTI-PND dosimeter microbubble formation when overheated

Post by Andrew Seltzman »

Note that this was with a high temperature heat gun for heat shrink tubing and was probably a much higher heat flux and delivered at a higher rate then Zan experienced(~13min). Also the big bubbles were already there and the dosimeter was depresurized due to a torn compression membrane.
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Richard Hull
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Re: BTI-PND dosimeter microbubble formation when overheated

Post by Richard Hull »

BTI dosimeters are incredibly expensive, true. They are rather short "half life" devices. Again, true. They have two strategic advantages for the amateur scientist and fusioneer.

1. They can be used to calibrate a correctly functioning, homemade, electronic neutron counter.
2. They can help a one pass, "do it" and "forget it" fusor fusion effort. (DIY types)

In the first application, the money is well repaid. When the device dies, you are left with a viable and long term calibrated electronic neutron counter which can serve for years into the future.

In the second application, money is just thrown at a problem that must be over come due to lack of verve and will to stick with the fusor, in the longer term. It is a DIY person's dream come true. Use it....Win the laurels.....leave forever. A perfect solution for those determined to win and who will pay this price to win.

Many of us have one of those big bubbled, long dead, BTI's as curios. Some of us got a lasting value out of them. I am still reaping the value of my money spent in 2004 on my BTI, continuing to obtain decent neutron readings based on that long dead device.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Zan_Chaudhry
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Re: BTI-PND dosimeter microbubble formation when overheated

Post by Zan_Chaudhry »

Interestingly, I just looked back at the pictures I took of my heated dosimeter after different amounts of time, and I noticed that the micro bubbles from the heat do not appear to grow the same way neutron bubbles do. There was very minimal growth if any.
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