FAQ - Bubble Fast Neutron Detector

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Jon Rosenstiel
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Re: FAQ - Bubble Fast Neutron Detector

Post by Jon Rosenstiel »

I finally got some time this afternoon to try out my new bubble detector. This thing is SWEET! Watching the bubbles “pop” into existence is pretty cool. (Better than a lava lamp)! I got a few runs under my belt, but I still need time to sort out the best way count the bubbles. So far, the best method for me is to shine an LED flashlight into the end of the detector, then count the bubbles as I rotate the detector back and forth slightly. (To make sure I haven’t missed any hidden bubbles).

BTI recommends using a video camera with macro lens, then marking the location of the bubbles on the monitor face. (Similar to cell counting)

After Santa delivers the new high-zoot digital camera I asked him for I think I’ll try taking a photo of the detector and see if I can count the bubbles on my computer monitor.

For this afternoon's tests I used a temperature correction factor of 1.4, as my lab was a balmy 27C.

I’m not going to post any data until I become a little more familiar with this device and am more confident and consistent in my bubble counting ability.

FWIW: Roughly speaking, my Ludlum rem ball detector is giving a TIER (Total Isotropic Emission Rate) approximately 40% higher than the bubble detector gives. Not nearly as bad as the 65% I was expecting.

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Richard Hull
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Re: FAQ - Bubble Fast Neutron Detector

Post by Richard Hull »

Jon, you are experiencing about what I did. I was getting about 50,000- 70,000 isotropic with the BTI bubble device and was used to seeing about 125,000 using the normal BF3 route with my Eberline PNC-1. It is nice to know that we are in the same ball park.

According to the folks at BTI, the accuracy can be in the 5% region. Therefore, I think we need to look at wrong assumptions in the input part of our old neutron counting. The only thing I can think of is the efficiency of the BF3 is a bit higher than .5% and I think the 1% figure is also a bit low.

It all comes back to just how efficient the moderator is. A BF3 tube or He3 tube at a decent pressure could easily be 10%-25% efficient if you could warrant that every neutron entering it were truly at thermal energies. With the rem ball, this is sort of warranted to be the case.

Thus, the rem ball is averaging out dose much like the BTI. So if a rem ball is showing 10mr/hr, the center of the ball is saying that the entire ball is being bathed in a flux of 80n/s/sqcm. If the ball is 30 cm from the fusor then 11,309 X 80 or ~900,000 neutrons/sec is the isotropic emission rate. The tube efficiency is not a factor due to the mated meter ball combo, being calibrated. (the 30cm is center of fusor to center of rem ball). Given this set of circumstances, the BTI detector could supply a correction factor, (scientific term) or a "fudge factor", (real life term), if placed at the same range.

With the BTI, we should be able to establish a calibration factor for any BF3 or He3 system. Once we get the counters in agreement with the bubble detector by using this factor, we will not be so pressed to buy another bubble device when this one blinks out in a couple of years as our electronic numbers will then be good and reliable. This factor would be "counter specific" and would make weak tubes, funky electronics, variable moderation efficiency, oddball and varying geometries and other such variables found counter-to-counter a non-issue.

The BTI bubble device is just too cool as it is free of all the above CRAP!

Again, absolute counting is a bear. Certainly, I would carry a bubble detector to a friends house to check his neutron numbers long before I would ever grab an electronic counter.

I look forward to your future report. Please put it in its own separte posting with an easy search title like "bubble detector results" or something like that. Post a pix or two of the setup.

Richard Hull
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Fusion is the energy of the future....and it always will be
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Re: FAQ - Bubble Fast Neutron Detector

Post by Jon Rosenstiel »

Richard, got a question on counting the bubbles.

I've noticed that some of the neutron produced bubbles are quite small, but they do seem to be real neutron bubbles because they disappear when the compression screw is cranked down.

Seems to me that ALL bubbles should be counted if they are produced by neutrons, no matter how small. What are your thoughts on this?

About the high readings the rem ball is giving….. I recall reading somewhere, not sure if it was the Songs list, or Intranets.com, or this list, but it was mentioned that the various manufacturers of our rem ball devices tend to shove them out the door with a fairly conservative calibration. (They want to play it plenty safe, don’t want anyone “overdosing” on their watch).

I wouldn’t think that what we’re seeing can be totally attributed to the manufacturers “playing it safe”, but it may be at least a part of it.


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Richard Hull
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Re: FAQ - Bubble Fast Neutron Detector

Post by Richard Hull »

Jon,

Count all bubbles just don't count "Fizz" bubbles which are truly very small. The small bubbles might be one third the size of the largest bubbles. Take another good look at the photos in the original post above. You will see some small bubbles there too. Basically, any bubbles not there when you started are neutron induced.

The conservative ratings on the REM balls might just be the answer. We need the fudge factor that the BTI device will supply.

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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Re: FAQ - Bubble Fast Neutron Detector

Post by badflash »

I've been e-mailing Rob Noulty, Ph.D of Bubble Tech (good people) and asked about the shelf life of the detectors. I've attached a paper he sent me that give the conclusion that you can use these detectors for 2 years if they are not temperature compensated and you close them up when you are done. Once the bubbles don't go away, it is time for a new detector.

Another cool note is that the bubble count should be done 2 hours after the detection is done. The bubbles continue to grow.

I was going to put off ordering until after I got my deuterium, but there is no longer any reason to wait. I'm not putting this project off that far, and the deadline may help.

Thanks to those that came before me, as they are willing to support us. Normally they won't sell just one detector, but for us they make an exception.
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Richard Hull
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Re: FAQ - Bubble Fast Neutron Detector

Post by Richard Hull »

Rob was a big help to me in the beginning, as well.

He also informed me that when the bubbles won't go away, you can still use the detector as it will still record perfectly!! You just need to subtract the pre-existing bubbles. Naturally, the item is totally shot when the initial bubbles are so numerous that the counting effort is a lose-lose proposition.

As the device gets older, the bubbles will naturally take longer, after recompression to go away, but all bubbles should be gone within 10 minutes. Those that remain are more or less permanent.

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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Re: FAQ - Bubble Fast Neutron Detector

Post by Alex Aitken »

I dont think direct links on espacenet work, but pick an archive and have a read of US 4,143,274.
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Richard Hull
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Re: FAQ - Bubble Fast Neutron Detector

Post by Richard Hull »

Additional BTI bubble detector data based on a paper study of the expected life span of the buble detector. A synopsis follows....

1. Always keep the detector stored in its shipping tube.
2. Always store the tube near its median temp range and never at extremes
3. The absolute calibration of the device is only warranted for about 6 months.
4. in the sensitive models under high flux or lots of bubbles per use, the device sensitivity increases.

For longest life...1 to 2 years.... obey all of the above plus........
Try to use the detector a minimum of monthly, but preferably weekly to count neutrons and preferably not a high flux. The detector likes to be used frequently to count low bubble numbers and get depressurized and repressurized.

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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Re: FAQ - Bubble Fast Neutron Detector

Post by badflash »

Just ordered mine. It shouldn't be long now before I can try it out...
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Richard Hull
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Re: FAQ - Bubble Fast Neutron Detector

Post by Richard Hull »

************* UPDATE 2006 ***********************

BTI now has a minimum order of $300.00 of their product!

The BTI model BD100R (33 bubble/mrem) detector is still $75.00 each meaning you must order 4 or more.

In addition the shipping and US/CANADA boarder transport fee and handling fee is on the order of $150.00 (this is for one or four dosimeters). What the hell ever happened to the joy and promise of NAFTA that Clinton pushed through? Seems like that little short dude Ross Perot was right........ Nafta would ultimately only allow jobs and massed units of cheap products to go over the boarders unfettered, but not personal american one off goods. (screwed again).

In future, unless you can bring four guys in with you, figure on dumping about $450.00 for a bubble detector dosimeter.

More sadness as no one wants to be saddled with only making $225.00 per order!

These still remain the best, most sensitive and cheapest fast neutron detectors out there, in spite of the new "ream your butt" pricing.

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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Re: FAQ - Bubble Fast Neutron Detector

Post by longstreet »

Oh, the graphics of that post! :)
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Re: FAQ - Bubble Fast Neutron Detector

Post by DaveC »

That is a shame about the minimum order and all the extra cost handling charges. Do you think there is any likelihood thesecould be made by amateurs?? The simplicity of measurement is especially attractive.... just the price is "off-putting".


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Re: FAQ - Bubble Fast Neutron Detector

Post by Richard Hull »

I understand the principle of operation of the devices, but the minutia of their composition and calibration is key to the success and replication effort.

Even they can't manufacture precisely as they expend no little effort in "binning", (their term), the dosimeters following careful exposure to a fixed and well known fast neutron field. Each dosimeter responds differently and a bubble count will determine each one's characteristics, (bubbles/mrem), which seems to be stable over about two years, once properly exposed and binned.

Their defender model is ultra senstive and provides up to 1000 bubbles/mrem! Their latest catalog even details an ultra-defender that looks like a small dry chemical fire extinquisher in size and can sniff out miniscule fast neuts in seconds!!! (didn't enquire as to price.)

Their bizz is really geared up 300% with the war on terror as they offer a multitude of new products geared at detecting bomb grade materials in 1/10 gram quantities!

This surely makes onesie-twosie dosimeter orders a trival matter outside their scope of profit taking.

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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Steven Sesselmann
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Re: FAQ - Bubble Fast Neutron Detector

Post by Steven Sesselmann »

I was reading further up this thread, that some of you are thinking how a
bubble dosimeter could be made. Does anyone know for sure what is in
them? What is the gel and more importantly what is the supercritical gas in
the gel? Could it be carbon dioxide?
Have you guys noticed extra fizz in your Coke while operating your fusor
:-)

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Re: FAQ - Bubble Fast Neutron Detector

Post by Robot_Maker20 »

I gather there have been attempts to avoid the visual counting nightmare by detecting each bubble formation accoustically, with some kind of vibration detector attached to the gel container. Anyone here tried this?
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Re: FAQ - Bubble Fast Neutron Detector

Post by Robot_Maker20 »

From what literature I've managed to scrounge, the supercritical liquid is commonly one of the dreaded chlorofluourocarbons (saw one paper where they used R-12), although I've seen references to hydrocarbons as simple as butane being used.
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Re: FAQ - Bubble Fast Neutron Detector

Post by Carl Willis »

The idea's been brought up a couple times, and Rob Noulty at Bubble-Tech can point to some literature. I don't think anyone's done acoustic detection yet with the little PND dosimeters.

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Re: FAQ - Bubble Fast Neutron Detector

Post by rcysa »

I am a student at the community college. I and our classmates are doing
a project about neutron. We don't have a lot of budget, so we can't
buy whatever we want. We need a bubble neutron detector, but we know the
company in Canada has a minimun order of $300. So, could you sell a
bubble neutron detector to us? We really need to finish the project.
Without that, we can't do anything.
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Monroe Lee King Jr
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Re: FAQ - Bubble Fast Neutron Detector

Post by Monroe Lee King Jr »

Hummmmm very interesting indeed. I guess now I'll be purchasing different types of polymer gels and doing some testing. I think we can bust the formula and if not exactly even being able to get a rough neutron bubble formula would be worthwhile. If other are interested please include your interest. I don't yet have a neutron source but I can make up gels and sent them to Richard or someone else with a working source for testing. The more folks involved the more test we can run. I'd like to start with a list of possible polymers to try.

Monroe

If there is interest I'll start a need thread to keep it off the FAQ.
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Monroe Lee King Jr
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Re: FAQ - Bubble Fast Neutron Detector

Post by Monroe Lee King Jr »

A bit more on the polymer gels

http://www.mkozicki.iat.p.lodz.pl/projectspgd.html

and

https://web.archive.org/web/20050225090 ... z/results/


Monroe

It may be as simple as silica gel super saturated with heavy water. The neutron strikes producing tritium gas bubbles.

Question: How hard is this "GEL" ? Someone have any idea? Is it really soft or is it hard like silica gel?
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Re: FAQ - Bubble Fast Neutron Detector

Post by Richard Hull »

Updated original posting text and replaced missing images 11/27/2019

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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Cade Neely
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Re: FAQ - Bubble Fast Neutron Detector

Post by Cade Neely »

Thought I'd give an update on the pricing of the bubble detectors sold by bubbletech. There is a minimum order of two at a price of $158 each. It costs an additional $56 in shipping/handling/border processing. All this comes down to a grand total of $372. Nice. Pretty steep price if you ask me.
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