A possible neutron detector tube (scintillation)

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Dennis P Brown
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A possible neutron detector tube (scintillation)

Post by Dennis P Brown »

For those thinking about a possible neutron detector, a scintillation tube the seller claims is "sensitive" to neutrons is for sale (there are three left) - the price for a complete and wired "head" isn't bad and if it does work on neutrons, is a possible detector. It is designed to connect directly into a Ludlum scintillation meter (if you have one of those this is ideal.)

Here is the e-bay site: http://www.ebay.com/itm/332143368927?_t ... EBIDX%3AIT

I ordered one but to be on the safe side, I also ordered some neutron sensitive plastic (for scintillation detectors.) This tube is pre-wired but is NOT in any manner turn key if you do not own an operational Ludlum unit designed for these high voltages! For this reason, I have ordered a High voltage capable pre-amp/amp and a discriminator board. Once I get my ST-360 working I will have a counter (a counter display of some type is also required if one wants to measure radiation.) I have a fully adjustable high voltage DC power supply since these devices require 1200 volts or so. These items are needed to make one of these tubes work (and all these items are needed for a He-3 or a BF3 tube as well.)

Aside: scintillation tubes require a higher neutron flux than a He-3 or BF3 tube.
Rex Allers
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Re: A possible neutron detector tube (scintillation)

Post by Rex Allers »

The seller's price for an assembled probe with a good 2" PMT doesn't seem unreasonable, however, I'm not sure how useful this would be for neutron detection.

He says the detection "crystal" is BC-408 which is a plastic material. I just looked on the St Gobain site for data on the BC-408. I found a page comparing the appropriateness between several of their plastic materials, here:
http://www.crystals.saint-gobain.com/si ... -sheet.pdf
BC-408 doesn't have a check mark for neutrons. Also it does indicate sensitivity to X-rays, which might complicate things in the fusor environment.

If it had something like the BC-720 on this page:
http://www.crystals.saint-gobain.com/pr ... -detectors
it might make a decent neutron detector but finding a detector crystal like that in this price range would probably be a great find.

I can't say that one of these is of no use for neutrons but from this quick look it doesn't look very good to me.
Rex Allers
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Richard Hull
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Re: A possible neutron detector tube (scintillation)

Post by Richard Hull »

My first neutron detector was a 2 inch PMT with a mounted BC-720 neutron detector. I bought the plastic scintillator at full list price from St. Gobains for $350.00 and slapped in on to a nice EMI PMT. I used it for 2 years and a number of others on songs and the intranet fusor board, back then, used it as well. There was a flurry of activity around the BC-720 and at least two folks custom made their own work-alike BC-720 knock-offs. It works, but at about 1.5% efficiency, coupled with the weakness of all first fusion efforts, it is a bear to give crisp data under 10,000n/s. I did a lot of long runs and used a statisical approach to ferret out my early numbers. I abandoned it for a BF3 based eberline rem ball which was marginally better. Scintillation systems will forever be sensitive to large flux gamma signals.

I, typically, give no credence to any use of a scintillion system trying to count neutrons. This is most true when a scintillator is in the hands of a neophyte user working his first pass as fusion.

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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