FAQ - Bubble Fast Neutron Detector

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Starfire
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Re: FAQ - Bubble Fast Neutron Detector

Post by Starfire » Sat Oct 09, 2004 9:28 pm

Richard - checkout;-

Admin note 160322: it appears that the item previously linked here is no longer available. However, http://bubbletech.ca remains a viable domain, see if you can search for what you're looking for there.

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Richard Hull
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Re: FAQ - Bubble Fast Neutron Detector

Post by Richard Hull » Sat Oct 09, 2004 11:42 pm

I have talked with them about the defender...... 1000 bubbles/mrem!!!!!!

For only $500.00 and it goes bad in a year or two.

They note that its indicating bubbles are much smaller than the 33 bub/mrem unit and are therefore harder to count.

I'll stick with what I have. More reports soon.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Frank Sanns
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Re: FAQ - Bubble Fast Neutron Detector

Post by Frank Sanns » Sun Oct 10, 2004 1:00 am

This unit is also a good way to invision what the damage to your body would be like. That is the kind of damage that would be all through your body from the neutrons from a fusor at similar distance. In your brain, heart, liver, and in every cm^3 of your body. The good news is that the human body is very durable (but not indestructable).

Frank S.

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Richard Hull
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Re: FAQ - Bubble Fast Neutron Detector

Post by Richard Hull » Sun Oct 10, 2004 3:11 pm

Frank is 100% correct. We must not lose sight of the nature of the fast neutron. To get this dose, of course, you would have to lay on the fusor while it is running. Our fusors are very weak neutron producers even during the best runs. This is why we need sensitive instruments to detect and quantify them.

Nothing beats using the inverse square law to protect yourself. Distance, coupled with even moderate shielding makes exposure a non-issue for fusor operators.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Richard Hull
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Re: FAQ - Bubble Fast Neutron Detector

Post by Richard Hull » Tue Nov 16, 2004 9:19 pm

The more I use this 33 bub/mrem BTI bubble detector, the more I think ....ALL ......that is, 100% of all other detectors are just not worth owning.

The sole holdout that I would wish beyond the bubble detector is the super sensitive HE3 detector in its large tube iteration that I currently use with fusor IV.

Remember, I own virtually every form of electronic fast neutron detector that is out there and the above is a definitive statement by a long time user and fusioneer. Cold fusion work and the ultra low level neutron detection demands the He3 big tube units.

The average amateur fusioneer could never do any better than one of the BTI bubble detectors. With electronic noise, arc discharges, wiring running everywhere, coupled with haphazard and unstable operation, true neutron output can ONLY be followed with extreme accuracy by the bubble detector! All other detection methods suck to greater or lesser degrees compared to this low cost, no battery, no power, no noise solution.

Again the only way bubbles form in this puppy is in a real swarm of fast neutrons!!!! A deadly field of gamma radiation yield no bubbles. A reactor load of thermal neutrons yields no bubbles. Basically, no bubbles means........No fast neutrons and, thus,.....No fusion.

In a small flux of only 8n/sq cm/second you will see one bubble pop into existence every 110 seconds.

This is not to denegrate counters or systems used by others or myself in the past. It is rather a story of forgetting that noise ever existed, of forgetting about background counting and determination, forever, about saving approximately $500.00 over a rem ball, about not being fooled by balky instrumentation operated at the hands of an amateur.

I just removed the batteries from all the neutron instruments I own! I just won't be needing them in the immediate future now that I am armed with the NIM bin based He3 counter and the BTI bubble detector.

Bubble detectors used to be expensive, short lived, high flux only and messy to work with. Most of these disadvantages have disappeared. There are only two remaining issues.

First, and of the least concern, is the narrow temperature range of operation (~45 deg F to ~92 deg F) and the need to adjust readings based on ambient temp at time of exposure. (note - There are tempcompensated units avaialble...$$)

The big negative is that you need to spend about $120.00/year to keep a fully action ready BTI bubble device on hand. For those who work for a living and are not saddled with kids, a mortgage and two car payments, the $120.00 is chump change to be positive about neutron outputs in fusion devices. Admittedly, the guys at BTI said the time of valued usage varies from 10 months to 18 months based mostly on temperate storage.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Adam Szendrey
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Re: FAQ - Bubble Fast Neutron Detector

Post by Adam Szendrey » Tue Nov 16, 2004 11:02 pm

Right now, the only, and single, disadvantage i see is the limited lifetime, otherwise it's really great, and rather cheap, and indeed an extremely reliable indicator of fast neutrons. Thanks for the info you supplied Richard.

Adam

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Re: FAQ - Bubble Fast Neutron Detector

Post by Verp » Wed Nov 17, 2004 3:49 am

This thread has me thinking about if it would be possible to make this sort of detector on my own. I just need to watch my tendency to get quixotic and take this beyond the area of diminishing returns. I once thought it would make sense to build a low whistle one octave below the standard D pennywhistle, rather than spend too much on a new one. The project got out of hand and I now own a drill press (not to mention all the various plastic and metal tubing for the body of the whistle) that costs more than one good high quality low whistle!

I have worked with gels in the past, through cooking and having poured my own agar based media into petri dishes and culture tubes. (I was making clones of local wild edible mushrooms I had collected.) I think some experimentation with the right gel will be needed to find the right ratio of liquid to polymer that is strong enough to prevent the liquid from bubbling, but flexible enough to bubble at the increased vapor pressure of the liquid caused by a high-energy neutron hit.

My first thought was to use agar, as that is readily available gelling agent, or other polysaccharide (sugar polymer) used to make growth media, but I realized even gelatin would work with a small bit of preservative that doesn’t mess up its ability to gel. If the vapor pressure of water isn’t high enough, another possible gelling agent is polyacryamide, which can handle many solvents that the natural gelling agents can’t and is available as an electrophoresis gel. It is polymerized in situ when the gels are made, but acryamide is a carcinogen and neurotoxin, complicating things.

The only reason my first thought was to use agar is that it is the gel I’m familiar with using at many different concentrations. The only reason it is preferred to gelatin is that microbes don’t eat it up as quickly. As I don’t want to grow things in the first place, I would use inexpensive gelatin in water with a bit of preservative if I was to make a very large detector. If a higher vapor pressure solvent were needed, I would make a small detector using polyacryamide. The gel used to make transparent candles might work, also. The liquid, I believe is kerosene or some other petroleum distillate, would probably be easier on the roughing pump than say water, if the pump was used to reduce the pressure in the detector.

Speaking of getting quixotic and going overboard, I was thinking of using a large gelatin or candle gel detector as the neutron shield of a high output reactor. The pattern of the bubbles around the fusor might give clues to the pattern of neutron emission. A concern might be if the detector were too deep, would the weight of the gel make the detector less sensitive toward the bottom? I might get around that by using less of the gelling agent at lower levels in the detector, but that might involve a lot of experimentation and may not work. I could just make the detector as discrete layers too thin to be strongly effected by the depth of the gel.

As far as figuring out the proper pressure to run the detector at, I would guess that an absolute pressure gauge that reads up to ambient air pressure could be used to find the pressure at which the gel starts to bubble. I would then use ambient air pressure to collapse the bubbles, and finally bring the pressure down to just above the pressure it bubbles at without high-energy neutron hits.

Rod

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Frank Sanns
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Re: FAQ - Bubble Fast Neutron Detector

Post by Frank Sanns » Wed Nov 17, 2004 4:26 am

Rod,

You might try to use poly vinyl alcohol in distilled water to bring the viscosity up to a desired level. A little fumed silica (Cabosil) could be added to keep the gel in place after the bubble forms. It is a thixotropic agent that will gell fluids that are not moving. Once they move a little, the visocity drops only to jump up again when the movement stops. A little benzalkonium chloride (Bactine) can be added to stop microbial growth. For the low boiling solvent that will vaporize to form the bubble, I think butane was the choice in the early tubes.

Frank S.

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Re: FAQ - Bubble Fast Neutron Detector

Post by Verp » Wed Nov 17, 2004 6:04 am

Frank,

Thanks for the input. I am familiar with benzalkonium chloride as quaternary ammonium detergent or “quat” as the active ingredient in sanitizing cleaners (as well as in Bactine) so price and availability are not issues. I am familiar with polyvinyl alcohol as an ingredient in some insect specimen mounting media. I remember it was a real pain to get into solution, but seemed to have no real toxicity issues. If gelatin is cheaper than polyvinyl alcohol and works well, I will try that with the weakest solution of quat recommend as a biocide, probably the concentration used as an algaecide in lab water baths. I’m not trying to kill tough spores and viruses, just keep organisms from starting families in my detector.

If a low enough pressure will make the detector work with just a water based gel, I won’t worry about how much butane or other low vapor pressure fluid to introduce, getting rid of another variable.

My understanding is that a good roughing pump tends to remove material with a higher vapor pressure than the oil, especially with a good sorbent to keep the oil clean, so careful use of valves should keep water contamination of the vacuum system low when I pump down the detector. I could just use a large bellows or piston to reduce the pressure in the detector and simply make sure there is no air space when I first fill the detector.

Perhaps the right amount of fumed silica would be the maximum amount that doesn’t make the water too cloudy, then add just enough gelling agent to keep bubbles from rising and the silica from settling. I’ve seen Carbosil for sale as a thixotropic agent for use with fiberglass resins as a filler, so it shouldn’t be a big issue to get it for a reasonable price.

Fumed silica got me thinking about sodium silicate and silica gel as gelling agents, but I am just brainstorming. An inorganic gel would not support or be broken down by microbes, though.

I will work on this some more, maybe after getting closer to actually making neutrons.

Rod

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Re: FAQ - Bubble Fast Neutron Detector

Post by Alex Aitken » Wed Nov 17, 2004 8:38 pm

"I think some experimentation with the right gel will be needed to find the right ratio of liquid to polymer that is strong enough to prevent the liquid from bubbling, but flexible enough to bubble at the increased vapor pressure of the liquid caused by a high-energy neutron hit."

Hmm. This was not my understanding of how the device worked. I was under the impression it was a suspension of droplets above the boiling point and under no extra pressure from the matrix. What's stopping the droplets from expanding is the lack of a surface to nucleate on. I was furthur under the impression that the point of the matrix was to keep the droplets seperate from eachother, seperate from the walls they could nucleate on and prevent the nucleation effect when it happens from spreading to the other droplets.

I suspect the chemicals need to be exceedingly pure from dust and solids.

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