The binning of bubble detectors

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Finn Hammer
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The binning of bubble detectors

Post by Finn Hammer »

I have been in contact with Bubbletec, and to my surprise, the detectors are binned in 3 classes, 1-2 bubs/mrem, 10-19 bubs/mrem and 20-40 bubs/mrem.
Buying 2 detectors from the 20-40 bin could very well secure me with detectors that deliver results that are 100% apart. One could show, say 100 bubbles in a given neutron field, the other would show 200 bubbles under the same condition. That is a bigger spread than I find acceptable.
They offer narrower binning, 20- 25 bubs/mrem at a 30% premium, and I assume this is the right thing to do,if any degree of accuracy is expected.
To those of you that have purchased these detectors in the past, which accuracy have you been used to in the past.
I had gained the impression that the bubble detector was the last word in neutron detection, even when it came to recording absolute numbers, now I am not so sure.
Opinion are welcomed.

Cheers, Finn Hammer
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Liam David
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Re: The binning of bubble detectors

Post by Liam David »

I'm pretty sure they have a calibration marked on the side accurate to 2 sig figs, like 33 bubs/mrem for the 20-40 option. I think by binning they mean manufacturing tolerance and uncertainty in what exact value you get.
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Joe Gayo
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Re: The binning of bubble detectors

Post by Joe Gayo »

Each dosimeter is labeled with its specific response. For calibration, you only need to know the response of the specific tube. It doesn't matter the difference between seperate tubes.
However, I've never received dosimeters that are more than 1 bub/mrem apart even when purchasing in quantities of 4.
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Bob Reite
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Re: The binning of bubble detectors

Post by Bob Reite »

The time that I bought a lot of two, they were 23 and 25.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.
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Richard Hull
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Re: The binning of bubble detectors

Post by Richard Hull »

When I bought back in the early 2000s, I ordered 33 bubs/mrem on two separate buys 3 years apart! They were rather precision binned to that one response. Those were the days of low neutron TIER results. they were binned to that level with specific and narrow temp ranges and a graph chart for correction based on a narrow range of temps. I bought from bubble technologies of Canada.

Everyone needs to let it soak in that +/-10% is a goal to shoot for in any form of neutron measurement. In rank amateur hands +/-20% is the norm without great care. As I have constantly re-iterated most measurement schemes can report run to run improvements or differential easily to within +/-5% or better! Absolute, one-off measurements of neutrons by most any method is a crap shoot to +/- 20%

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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Dennis P Brown
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Re: The binning of bubble detectors

Post by Dennis P Brown »

I scanned the FAQ's on Bubble detector's and except for the Mathematics " didn't see anything like this thread here. This is a rather useful thread and wonder if it could be tagged in the FAQ's for everyone - it is rather valuable for understanding these devices and what to order and why as well as understanding their specific calibration issues.
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Finn Hammer
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Re: The binning of bubble detectors

Post by Finn Hammer »

All,

Great feedback from you all who bought detectors, and could point out the labelling of each individual item. Somehow, I couldn't get that point through to the representative, due to lacking proficiency with the english language, I got sensitivity and accuracy all mixed up, you see.

So it was with great relief, that I received this message from Robert at BTI:

-------quote:

Hi Finn,

That is correct. We still label each individual bubble detector with its specific sensitivity.

I will send you a quote shortly.

-----end quote.

He also sent me this app note, which may be old news, but not to me.

Udklip.JPG

Cheers, Finn Hammer
Frank Sanns
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Re: The binning of bubble detectors

Post by Frank Sanns »

That attachment sums it up very well. Bubbles, bubbles, bubbles. The more the better.

In an earlier post I emphasized that more measurements are needed for good statistics. People are splitting hairs here for the accuracy of the individual units when that is not the limiting factor. It comes back to statistics again. You need more measurements no matter what the calibration is. Produce more neutrons, count longer, move closer to the source, or buy more detectors. This last point is probably the most practical.

Having more than just one detector gives more bubbles hence more samples to use statistics on. They can be combined into one overall number by simply using the weighted calibration average of each. This is true with any range or any calibration. The total number though will give a better estimate of the actual neutron output that greatly exceeds just one bubble or any other detector.
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
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Joe Gayo
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Re: The binning of bubble detectors

Post by Joe Gayo »

Personally, I find more than 50 bubbles hard to count. I end up counting 6-7 times and using the number most often repeated (as long it was at least 3 times).

There are other ways to count. I've set up a lightbox and a Raspberry Pi camera and wrote some code using the OpenCV library to count bubbles, but the accuracy hasn't been great. I've tried analyzing pictures from multiple orientations, but the lighting and camera lens are critical. BTI sells a machine to do this but it's $10k (dumb).

Another way I am investigating is acoustic. When each bubble forms it makes a characteristic noise. Two microphones and anticoincidence detection and this has actually been done for professional detectors used with accelerators (for example, Framework Scientific ABC 1260). See attached papers -

https://www.sciencedirect.com/science/a ... 8796001564
ACOUSTIC DETECTION OF NEUTRONS BY BUBBLE DETECTORS.pdf
(209.94 KiB) Downloaded 205 times
ELECTRONIC NEUTRON PERSONAL DOSIMETRY.pdf
(186.43 KiB) Downloaded 193 times
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Richard Hull
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Re: The binning of bubble detectors

Post by Richard Hull »

I owned a formal BTI manufactured counting box with associated light, camera and rotating system with electronics! Found it at a hamfest for $10! The guy did not know what it was. I used it while I had BTI working dosimeters. Once done with those type detectors and I had my "calibration factor" in hand, I sold it to someone that was once here but never made a fusor for $100. The 33 bubs/mrem created plenty of bubbles.

Since Covid hit, hamfests have been a rare thing. I use to go to 13 hamfests each year from Maryland, Virginia and North Carolina. In 2020 there was one. In 2021 there were 3 that were held, 2 of them were muted due to "fraidy cats" and perhaps deaths of ancient old farts like me, getting covid in 2020 or 2021. Only one great, large, outdoor fest in 2021 August (Berryville, VA). Richmond's February, 2022 "Frostfest" is already cancelled! #@$!%@.....

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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Bob Reite
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Re: The binning of bubble detectors

Post by Bob Reite »

[topic drift]
In 2021 I went to the Murgas Hamfest and Kimberton. At that time, they seemed to be at their pre COVID level. The Hamvention in Ohio is "ON" for this year, I plan to go.
[/topic drift]
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.
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