BTI Detector / Ultraviolet Interference

This area is for discussions involving any fusion related radiation metrology issues. Neutrons are the key signature of fusion, but other radiations are of interest to the amateur fusioneer as well.
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Mark Rowley
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BTI Detector / Ultraviolet Interference

Post by Mark Rowley »

Following a bunch of test shots with the linear pinch tube I began to notice some inconsistencies with the BTI dosimeter. This led me to call the company and speak to their resident expert about my arrangement, system, and potential false positives with their product. I was assured there was no interference.

Throughout the following week I conducted a few more shots only to find the same issues constantly repeating themselves. Those issues being a very large difference between what I was detecting near the quartz tube and that of the copper return conductor. After contacting Tim Koeth and Jake Hecla, it was suggested that intense UV shining through the quartz discharge tube may be responsible for the high bubble count. A few days later I applied common black electrical tape to the dosimeter and conducted a host of test shots. The tape was completely effective at stopping the formation of false bubble readings.

To be clear to those new to the forum, this issue is only specific to bright flashes coming off a pinch device and doesn’t have much relevance to a Fusor.

For pinch tube neutron detection using a BTI dosimeter, a simple application of thin foil or lead over the dosimeter should suffice and restore accurate neutron detection.

The below pic is primarily UV / intense light interference with the dosimeter. No neutrons were present when this detector was exposed to the discharge flash. This is 100% reproducible as long as the detector portion is unshielded to the flash.

Mark Rowley
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Richard Hull
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Re: BTI Detector / Ultraviolet Interference

Post by Richard Hull »

Mark thanks for the update and I hope with the tube shielded you can indeed get some neutrons down the road. As you say, this is not an issue with the common fusor here as there is no intense UV flash in the multi-megawatt PIP (peak impulse power), seen in your device.

Did BTI say they knew about this? They may have taken Boxing Day off and not be back at work until Monday.

Richard Hull
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Re: BTI Detector / Ultraviolet Interference

Post by Frank Sanns »

Yet another "fool proof" device has a flaw. Many rely on the BTI detectors as they are lead to believe, mainly from the factory, that they are infallible to environmental factors like RF, pulse, gamma radiation, and the like. They are sensitive to heat and now to UV.

Mark has been on the hunt for the inconsistent reason for the bubbles. Glad you found it Mark.

As stated many times, neutron activation and the corresponding decay spectrum of silver or indium is the most fool proof of all the methods. While others work, they need to be in the skilled hands of a critical thinking researcher as pitfalls are all around.

The number of people report neutrons on this site is relatively high. The number of people actually producing neutrons is actually quite low.
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
Jon Rosenstiel
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Re: BTI Detector / Ultraviolet Interference

Post by Jon Rosenstiel »

Relevant thread from 2006.

viewtopic.php?t=5715

Jon Rosenstiel
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Mark Rowley
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Re: BTI Detector / Ultraviolet Interference

Post by Mark Rowley »

That’s a great thread Jon. After seeing it I vaguely recall reading it when first posted 13+ years ago.

I may try a brief exposure to UV from a carbon arc lamp in the next day or so. My main concern when doing so is to keep any thermal influence from skewing the test.

Mark Rowley.
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