Fusor Forums

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

I dont think direct links on espacenet work, but pick an archive and have a read of US 4,143,274.

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

Just ordered mine. It shouldn't be long now before I can try it out...

************* 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

Oh, the graphics of that post!

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".


Dave Cooper

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

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


Steven

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?

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.

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.

-Carl

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.

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.

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?

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

Richard Hull

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.