Long Lasting Bubble Detector

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Mark Rowley
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Long Lasting Bubble Detector

Post by Mark Rowley »

I took delivery of two BTI Bubble detectors on November 6th, 2019. Based on what others have said, I fully expected them to start failing after 4-5 months. Surprisingly, the first one to fail did so around Christmas 2020. The second one is still going strong....for how much longer is anyone’s guess. I’d suspect it’s on the cusp of demise but there’s no obvious signs of trouble. No leaks, no problems resetting, and the bubbles are of the proper size.

Fwiw, I always keep them sealed in the tubes when not in use. Additionally, when in use I only take them out to activate them and then back in the tubes during most fusor runs.

This is from last weeks run. Shown here is it’s reset / zero bubble state.
3C1455D5-E2F6-4622-BCBA-D946C32C8824.jpeg


Here it is after the run:
46621FAC-A5E4-4DA2-91EF-45C2EAEB5D8A.jpeg

This is it after being reset:
213A1CF7-3E8E-4D5A-BA8A-B0BEB95BAD33.jpeg

Buying disposable neutron detectors at such high prices was a very bitter pill to swallow. But this unusual longevity has definitely taken away any regret.

Mark Rowley
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Richard Hull
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Re: Long Lasting Bubble Detector

Post by Richard Hull »

Wow! You are a record holder!! I have bought about three BTI's over a period of 7 years 2004-2011 and one lasted 4 months (leaked). Another went about 8 months and the last one about 6 months. I did store the dosimeters in their tube, as recommended, and stored in my heated and air conditioned home. (no temp extremes) I think the previous record holder is Bob Reite at about 1 year.

The typical signs of impending BTI doom is slow to incomplete clearing and giant lopsided bubbles.

You got a goodun'........

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
Frank Sanns
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Re: Long Lasting Bubble Detector

Post by Frank Sanns »

I examined the couple of mine that failed in the several months window. I am not impressed with the design of the seal on these units. It is like a kids toy rather than a precision measuring device. For the price point, they are a scam.

Sure they look nice with the knurled black knobs but it is what is between the knobs and the gel is the problem. The seal is a tragic failure of engineering. I wonder how many tax dollars goes to buying these devices each year.

We all work with high vacuums and valves. Vacuum valves have bellows that are hermetically sealed at both end. The valve mechanism is completely outside of the vacuum circuit. In the case of the dosimeter, there is just an organic diaphragm that is friction fit or glued to the clear tube. Like I said, it is a terrible design and they got my money for two more out of curiosity than need.

I have multiple He3 tubes and instruments to count. To me redundancy with dissimilar everything is what I count on. Two different size tubes, two different types of meters, two length leads, two distances. If the proper ratio is not there for every single measurement then there is no confidence in the neutron counts. Asymmetry is my motto. RF and other pesky things get into places you may never know. Using asymmetrical devices and setups will show noise and artifacts in an instant.

And to think all of the years this setup has worked reliably, these poorly designed bubble detectors are not on my radar for anything that I can imagine in the future. Still, they are ultra valuable in the hands of both the unskilled and the skilled fusioneer. I do get that and I would own one, if only......... oops, there goes another one failing in the world............ and another. Pull out your checkbooks.
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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Richard Hull
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Re: Long Lasting Bubble Detector

Post by Richard Hull »

You are correct of course, however the killer is the equal cost of their outrageous shipping and minimum order quantity. As you note they are a Godsend to the "in it to win it" crowd to whom electronic detection is a bridge too far and activation is out of the question as they will never get the fusion numbers to do it. The BTI will sniff out fusors working well under 50K n/s easy. The parents usually foot the BTI bill.

We have not seen many of the in it to win it crowd of late. I think covid, tight money, and our more restrictive neutron and plasma club rules tend to dissuade what use to be a glut of DIY folks.

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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Mark Rowley
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Real name: Mark Rowley
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Re: Long Lasting Bubble Detector

Post by Mark Rowley »

Richard,
From this side of the country it just seems like an overall decline of interest in DIY science projects. Since about 2010-11 it’s really taken a nose dive. During that time my kids were in high school. The schools stopped all involvement in the traditional type science fair. No hands-on at all. Everything has converted into virtual experiments or builds on a computer. It’s really shocking and sad. And I believe this is why we’re not seeing much activity. Yes, COVID has an impact but I just don’t see the flurry of activity we had (2000-2011) returning anytime soon.

Both of my kids are separated in age by 5 years so I got to participate in and observe the high school curriculum for practically a decade (Bay Area Ca). As of now, there is literally no instruction to get kids involved in anything remotely resembling a fusor, Tesla coil, VDG, anything plasma related, etc etc. And God forbid you even mention nuclear science, radiation, or even a Geiger counter. At best you may see an AA cell connected to an LED....no joke!

My youngest is now in college and the same hands-off mindset prevails among his instructors.

I understand there are some scholastic exceptions to this phenomenon, but what I’m seeing is becoming the norm and hands-on being the rare exception.

Back to the BTI’s....
I think I’m destined to make one more purchase in a year or so. I see no alternative (yet) for low yield pulse work.

Mark Rowley
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Richard Hull
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Re: Long Lasting Bubble Detector

Post by Richard Hull »

Thanks for the update on CA education direction. I know a teacher in our local school system. The kids are back in class and being taught now, finally, but it is exactly as you say. No hands on and the death of any cursive writing, no history in many cases, STEM stuff is dumbed down and I was stunned to learn that the school system has lowered the grading scale and are substituting "incomplete" for "F". No student is to be told he or she failed!!! What! There will be no SOL testing in the city for 2020 or 2021. In short, the schools are turning out a lot of "incompletes" into the world of tomorrow. Who says the US isn't headed into a caste system, if not by decree, then by allowing many "incompletes" to roam among us. The colleges are little better. Only those colleges hard into the STEM courses remain proof against graduating people who can't "do".
It all goes back to parent involvement or most often the total lack of it.

I understand the critical need for BTI product in low output and infrequent neutron fields. The BTI's gift is complete immunity to intense EM pulse systems. I found it very interesting that you shielded your BTI against UV pulse flash. I will remember that one. Like I say, we are all here to contribute and learn. If one can't contribute, one can do, but if one isn't in the mood to read, discuss and learn then why even bother to be alive?!

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
Frank Sanns
Site Admin
Posts: 2119
Joined: Fri Jun 14, 2002 2:26 pm
Real name: Frank Sanns

Re: Long Lasting Bubble Detector

Post by Frank Sanns »

Self discovery and thinking for yourself is a thing of the past. We, as a society in the US have devolved into tearing people down for the minutia. Where even minor imperfection is cause to destroy a person's life or career. Safe zones just produce gatherings of the weak, self absorbed, blinder wearing hyenas that are waiting en mass for the next easy prey.

The entire educational system is screwed up and graduates do not even recognize it. Technical professions are now grouped with non professions. Is there computer science? Is that the same as physical science? We have become a service industry country and not innovators and producers. We have farmed that out to the other countries of the world because it is cheaper and more convenient. Why teach a student how to discover when you can just get it off the shelf from China or India?

It is a dangerous spiral this country is in and the closed schools and the hands off learning environment will have an impact into the decades to come. And we all sit around watching and are unable to convince those to be how tragic this approach really is.

Sorry to take a diversion in the thread. Back to the BTI. Yes the minimums and shipping are ridiculous. But as Mark has pointed out, there are not many easy ways to measure neutrons in a pulsed fusion schema. With that said, the UoW at Madison was working on some secondary detection after a pulse. Blanking the detector during the ms of the pulse but then acquiring data on fissionable material in the ms following. This eliminates all of the RF hash during the pulse but is listening in the ms after the RF oscillations are damped out. A little more fiddling with electronics but another good approach.
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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