Neutron Scintillation Tube/Counter

This area is for discussions involving any fusion related radiation metrology issues. Neutrons are the key signature of fusion, but other radiations are of interest to the amateur fusioneer as well.
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Richard Hull
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Re: Neutron Scintillation Tube/Counter

Post by Richard Hull » Thu Nov 16, 2017 8:51 am

I have said it before. It is the devil's own work to use any bulk scintillator and PMT to successfully and honestly report neutron numbers.

My first neutron detection with fusor III in 1999 was with a Bicron special gamma insensitive, 2", ZnS:Ag ringed, lucite, fast neutron scintillator. This little marvel cost me $350.00. I carefully attached it to a Hamamatsu 10 stage PMT. It worked great! But at a manufacturer quoted efficiency of 0.1%. I struggled to get more than 15-20 counts over 5 minutes of fusor III operation. Background was forever 0-1 count over 5 minutes. Almost nothing lit this puppy up, though I am sure a lethal hail of fast neuts would have it humming right along. However, with such a blast, a GM tube held near your silver teeth fillings or wedding ring would be a cheaper solution.

I left that Bicron scintillating dud in the dust and used my rem ball, (BF3), for a year or two. With fusor IV, in 2004, I spent $250.00 with Don Orie at O.E technologies and picked up a Reuter and Stokes 24" long, P4, 3He tube and have never used anything other than that super detector ever since.

Scintillation, neutron counting is for the birds and I doubt I would favor granting neutron club membership based solely on a scintillation system.

Richard Hull
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Dennis P Brown
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Re: Neutron Scintillation Tube/Counter

Post by Dennis P Brown » Thu Nov 16, 2017 10:47 am

Richard, thanks on the insightful comments; I know they are based on years of practical experience and tend to prove prophetic ... especially for us "gotta see for our selves folks ..." .

Your points are all valid but since the neutron scintillation detector is finished, might as well test it this weekend. Besides, since my russian made Boron Trifluoride (BF3) tube based system is still in repair mode, I have some time on my hands to try this ...just wish it was more likely to work than not.

I do not really expect good results but will find out and I do enjoy doing the construction and research on these projects.

In sum, this is more a project of curiosity since I know I have neutrons. Yet, I want to try other detector systems to compare - most likely a wasted effort (been there, done that a lot lately.) Of course, repairing the issue with the ST-360 that is causing the problems reading my corona tubes will shift to a higher priority status after this is done. That is, creating a proper noise free signal is the next project after this PMT system. Just that since I already had the components for a PMT system on hand and I decided it was time to assemble and test such a detector.

I have a lull anyway while doing the repairs on the Van de Graaff - that is preventing me from doing any real testing on that front - so, just being busy in the home lab! Needless to say, this accelerator project is still the biggest windmill I am fighting ah-la Don Quixote ... lol.

Aside: after reading up on design of PMT's, I see that the caps on the last two or three dynodes is generally required if depletion of the charge occurs on these during heavy signal events ...maybe an irrelevant concern for a neutron scintillation tube assuming any gamma ray secondary showers should not create significant depletion cascades in a detector with such a small scintillation volume. Also, for anyone expecting a series of very fast signals in the unit, such caps would tend to cause discrimination issues, I would think; for a fusor, not a likely occurrence, I would suspect.
Last edited by Dennis P Brown on Thu Nov 16, 2017 2:47 pm, edited 4 times in total.

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Re: Neutron Scintillation Tube/Counter

Post by Silviu Tamasdan » Thu Nov 16, 2017 12:08 pm

Don't worry, in a sense we're all old Spaniards trying to get our horses to move along. Occasionally we end up giving each other's horses a nudge. It's all good.

This BC412 detector of mine was never intended for neutrons or for fine discrimination of gamma spectra. I bought it for background/safety checks. I hope that it may also be useful in future prospecting trips (it's just at the edge of what I would call too bulky for a portable detector).
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Re: Neutron Scintillation Tube/Counter

Post by Dennis P Brown » Thu Nov 16, 2017 12:14 pm

Et tu, Brute? First Richard and now you ... LOL

OK; so, I guess I will expect no results this weekend and will assign the unit to the self for my backup detectors for x-ray testing ...well, at least my project to add a digital counter to the GM unit is looking up since I will have a number of detector tubes to use with it. Also, learned a bit of useful information on these units as well as building skills. So, that is a minor plus coming out of this project.

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Re: Neutron Scintillation Tube/Counter

Post by Silviu Tamasdan » Thu Nov 16, 2017 2:00 pm

Seriously, I applaud your neutron scintillation effort... but I'm going another way. Especially since my current setup doesn't allow for advanced pulse shape manipulation. But I'll watch this thread with interest.

Knowing how to wire and bias a PMT is always useful. My latest build is a monster 3x3inch NaI(Tl) crystal with a 3" PMT (the parts including crystal cost less than $250). The gamma spectrum I posted above was done using it. Hoping to do some neutron activation experiments with it.
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Re: Neutron Scintillation Tube/Counter

Post by Richard Hull » Thu Nov 16, 2017 8:37 pm

When U hunting, absolutely nothing beats a scintillation counter. The world famous TSA scintillation counters are the absolute best. When in the high dessert of Utah, I left my GM counter back in the motel room and found the good stuff up to 1 foot underground! (always bring a shovel) A GM counter is only of value once back at the motel to figure out what to send home or toss out the next day at the next mine.

I attach two images of how to U hunt with a scintillator. Note my backpack which had a number of hot specimens in it, located right at my spine, a blood forming organ, soaking up the Beta and Gamma rays.

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Richard Scans.JPG
At the Home Stake mine, I scan with my TSA scintillator. Beautiful vista from the mine in late Ocotber 2009
Bill digs it.JPG
My pal Bill Kolb digs for a rich chunk of U rock after my scintillator sniffed it out.
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
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Silviu Tamasdan
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Re: Neutron Scintillation Tube/Counter

Post by Silviu Tamasdan » Thu Nov 16, 2017 9:49 pm

Nice application of strings there. I plan on a solid handle for the scintillator in the vein of my Geigerstik. With the ratemeter in a pocket of the backpack and headphones on.

BTW this is the Geigerstik.
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Re: Neutron Scintillation Tube/Counter

Post by Bruce Meagher » Thu Nov 16, 2017 11:25 pm

Dennis, Wrong person. I still have plans to do pulse shape descriminatiin with some of my bc-412 stockpile. Unfortunately, I have many plans, each one moving forward at a glacially slow pace.

Bruce

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Dennis P Brown
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Re: Neutron Scintillation Tube/Counter

Post by Dennis P Brown » Fri Nov 17, 2017 1:55 pm

LOL; oh, missed that! Didn't realize the relevance, there, Bruce! Thanks for pointing that one out!

Slow is fine - I built up required supplies/equipment for my scintillation effort for over a year. Like the self contained counter I acquired for another project, I will now have a use for that after all since I now have such a selection of tubes for the old analog GM unit; or my lead bricks (for yet another project), here again, I might have a use for them shielding the scintillation counter. Cosmic showers or no ... well, the corollary for that saying doesn't work here.

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Re: Neutron Scintillation Tube/Counter

Post by Silviu Tamasdan » Fri Nov 17, 2017 3:15 pm

LOL @slow. Look at my forum registration date. That was about 1 year after I had started making plans for a fusor and began gathering parts. :)
There _is_ madness to my method.

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