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Paper on neutron counting using ZnS(Ag) phosphors

Posted: Fri Sep 14, 2018 9:01 pm
by Jon Rosenstiel
Phosphor mixtures for neutron scintillation counting.
ZnS(Ag) for neutron detection.pdf
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Jon Rosenstiel

Re: Paper on neutron counting using ZnS(Ag) phosphors

Posted: Sat Sep 15, 2018 8:29 pm
by Roberto Ferrari
Jon,
It is an interesting paper but nothing is said about neutron fluxes.
The only neutron parameter reported is energy.
Do you think ZnS:Ag may be sensitive enough for the typical fusor production?
Roberto

Re: Paper on neutron counting using ZnS(Ag) phosphors

Posted: Mon Sep 17, 2018 9:31 am
by John Futter
roberto /Jon
I made a neutron scintillator setup a few yago and posted it here to how i did it. It used Zns Ag etc and worked well all but for the few seconds delay. So its not prompt but i tested it in our magnet room @ work while a 900kV deuteron beam was in use. Quite a few neuts run around the magnet / slits in the magnet room which is well shielded from the outside. I seem to remember copper and lead shielding to suppress gammas.

edit found the reference
did I really do this that long ago!!!1!!!!

viewtopic.php?f=13&t=6064

Re: Paper on neutron counting using ZnS(Ag) phosphors

Posted: Mon Sep 17, 2018 1:42 pm
by Roberto Ferrari
Hi John

Glad to know about your experiment.
I will give a try as soon as I get some ZnS:Ag film.
My neutron source will be an old vial with Ra paint (from old watch shop) and a small Be window from a damaged X-ray tube, just placing the Be in front of the open vial. The efficiency will be low but I don't want to mix the Ra paint with Be powder.
It is a rare piece in my collection of NORM and TENORM objects.

Re: Paper on neutron counting using ZnS(Ag) phosphors

Posted: Tue Sep 18, 2018 5:05 pm
by Jon Rosenstiel
Roberto,

ZnS(Ag) neutron detectors are notoriously poor performers (as I recall,efficiency is around 1%) so for the budding fusioneer this avenue is pretty-much a non-starter. But for someone that already has a neutron producing fusor and is looking for something to do with those neutrons this may make for an interesting project.

Jon Rosenstiel

Re: Paper on neutron counting using ZnS(Ag) phosphors

Posted: Tue Sep 18, 2018 6:27 pm
by Roberto Ferrari
Hi Jon

Understood!
Let's have enough neutrons and then...
Roberto

Re: Paper on neutron counting using ZnS(Ag) phosphors

Posted: Wed Sep 19, 2018 1:40 am
by Jim Kovalchick
I've had this paper in my pdf collection for years. Lot's of valuable info. I built the device and even used the same model Dumont pmt. I managed to find a source of boron powder highly enriched in B10. You dont need much. I got my phosphor from United Nuclear. Use the Ag doped kind, not Cu.

You need to wait a while for the phosphor to settle when you first get it light sealed.

You need to fiddle to distinguish between gammas and neutrons. I suspect using a Ra Be source will make it hard. Enough radium to produce neutrons makes tons of gamma. Better to use Am Be or proven fusor.

Re: Paper on neutron counting using ZnS(Ag) phosphors

Posted: Wed Sep 19, 2018 3:46 am
by Richard Hull
All of these issues came to the fore in 1999 on songs.com and later, the intranet fusor site. There were hornyak detectors, and I used the Bicron model with target rings of ZnS:Ag. I tried a 2" with PMT and found the .75% efficiency nearly worthless in my first fusion efforts. (It did work, but...). I then spent $450 of the Bicron 5" "target" neutron scintillator and used a large Dumont PMT with it. It was my first really useful neutron detector. Same efficiency but larger capture area. I quickly moved to a snoopy and then a PNC-1 using BF3..... Much better, but not by much.

Once I got my 3He tube, it was "The solution for fusor detection". I also bought 2 BTI bubble units a year and a half apart, but by this time I was doing well over 500K n/s, isotropic. The BTI's served over a year to gather data so that I could calibrate and obtain a "K" constant adjustment factor related to isotropic emission and counts on my 3He system.

The NE and most BC scintillators are indeed difficult to set up for neutron vs. gamma detection. The expensive Bicron scintillators had no such issues as they were tooled in a manner to effectively not respond to gammas, but again that efficiency was under 1%.

In general, outside of an expert hand with impressive instrumentation, equipped with a good source of neutrons, in hand, no scintillator will function for a newbie fusor working in the doldrums.

Been there....Done that...

Richard Hull

Re: Paper on neutron counting using ZnS(Ag) phosphors

Posted: Wed Sep 19, 2018 2:45 pm
by Roberto Ferrari
Hi Richard

Thanks for the comments.
I will rely most in Ag activation and the russian corona tubes.
Roberto