Neutron Irradiated Dime REDUX

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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Mark Rowley
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Neutron Irradiated Dime REDUX

Post by Mark Rowley » Tue Oct 27, 2020 5:11 am

Just for fun I reactivated a vintage Neutron Activated Dime from the Museum of Atomic Energy at Oak Ridge National Laboratory. Using Fusor 2020, the dime was exposed to a roughly estimated TIER of 1,300,000 (1.3E+6) neutrons per second for 5 minutes. The end result was a 350cpm peak of mostly beta radiation emanating from the Ag110 decay. Within 5 minutes any readily identifiable trace of activation was gone. I used a pancake paired up to a Ludlum Model 3 for detection.

Due to the reduced physical size of the activation surface and the lessened purity of the silver, it was hardly a blazing result as I normally get with 1.5x1.5” pure silver foil. But I’m not complaining as the results were still pretty decent.

Here’s the complete video:
https://youtu.be/UK8RIJn88Y0

The Oak Ridge National Lab website has a really good write-up on the old dimes.
https://www.orau.org/PTP/collection/med ... /dimes.htm

Mark Rowley
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Richard Hull
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Re: Neutron Irradiated Dime REDUX

Post by Richard Hull » Tue Oct 27, 2020 7:24 am

Yes that was when money was real money and carried its own weight in real value. 90% is a good activator for near mega mark fusors if one can't obtain 999 or better Ag foil.

Whether a blazing result or not, it alone, is enough to prove fusion. It is a pity so many first pass, DIY fusors, as so poorly powered and not operated well that activation is, often, just not possible.

On my Arduino box, to read beta activation within my moderator, I chose a 10 minute (60 10-sec counts). This tracks the full decay over time. In general, in a given flux, 5 half-lives period must be suffered by that which is to be activated to rather fully activate it. the Ag108 is a bit over 2 minutes, thus the 10 minute exposure. As seen in my Xcel spread sheets, I can capture the stepped decay of both the rapid 110 and the tapering off of the more leisurely 108.

The world's fare item, I have 4, and if you visited the atomic energy museum prior to 1964 you got a smaller, aluminum metal cased, plastic domed button with your dime in it. I have several of those as well. I see you have both of them in your fine video... They are (were) common on E-bay in the 90's.

Good work Mark! That was a great video with a clear explanation of your effort! The ORAU nuclear history museum is a great site to visit. Both Bill Kolb and I have contributed data to Paul Frame's effort to fully catalog much of the fine details related to our nuclear history and instrumentation.

I am struggling to obtain some rhodium, (the ultimate metal to activate), but it is now about $11,800 per troy ounce. Even a 1X1-inch ultra thin foil might cost $400! For those activating........ The easiest materials to activate are those with produced isotopes which are heavy beta emitters like silver, rhodium and indium. As Mark notes, he uses his 2" pancake GM counter, you can easily use a GM counter to detect betas. GM counters are cheap, so try and activate the easy ones that are principally beta emitters. Many worthy and nice materials are very low or non-beta emitters, but do produce copious gammas. A GM counter is of little use here, for the most part. A good Gamma ray spectrometer is needed to show off what might be a lot of nice gamma activation energies.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Mark Rowley
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Re: Neutron Irradiated Dime REDUX

Post by Mark Rowley » Tue Oct 27, 2020 7:37 am

Rhodium would be great. Anyway you could get a small piece of foil on loan? Couldn’t imagine paying that much.

Mark Rowley

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Richard Hull
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Re: Neutron Irradiated Dime REDUX

Post by Richard Hull » Tue Oct 27, 2020 8:36 am

Unfortunately, I can easily imagine my paying that much for the "ultimate" activation material. I haven't found that source yet, but I do have a number of "feelers" out there working at it for me.
Rhodium is a bastard to deal with, it is a hard and brittle metal at room temps. It doesn't like to be rolled unless at very high temps. So the typical 1/10 ounce bar is of little value for activation beyond its outrageous price. The ideal is a 2 X 2 inch ultra thin foil.

As noted before, 100% of rhodium is composed of only one single isotope, so 100% of it fully activates into only one single isotope in any given thermal neutron field within only 5 minutes! (55 sec half life). Its activated isotope is a heavy beta emitter.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

Dan Knapp
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Re: Neutron Irradiated Dime REDUX

Post by Dan Knapp » Tue Oct 27, 2020 12:26 pm

Richard, Have you considered a thin layer of rhodium plating? There are various rhodium plating services available for jewelry at affordable prices.

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Jim Kovalchick
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Re: Neutron Irradiated Dime REDUX

Post by Jim Kovalchick » Tue Oct 27, 2020 1:33 pm

Regarding rhodium, dental mirrors are plated with it. I once tried irradiating a larger palate one. I didn't get much output to speak of, but I never determined if it was just too little Rh or too few neutrons.

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Re: Neutron Irradiated Dime REDUX

Post by Richard Hull » Tue Oct 27, 2020 7:25 pm

You do need some atomic thickness of the stuff. The ideal is a thickness that warrants significant internal capture and a beta release from the surface to be detected and not absorbed in the metal's volume. Kinda' tricky, but doable. I would think, .005 - inch would be nice.

Until Rhodium is obtained, .999 Silver remains the ideal metal for activation, regardless of your neutron flux. Indium is a bit better for the guy with a good gamma spec, if you are looking for a great gamma image of your activation. This, provided you have the flux and can run at that level for a bit longer than doing silver for betas.

I kind of envy the guys who have their fusor and a good gamma spec in their uniformly heated and cooled spaces. (room temp) I would have to get mine set up in the upstairs lab, then extract the activated material, race into the house and up the stairs to place the gamma emitter under the gamma spec. One doesn't operate a NaI:Tl crystal over a range of freezing temps to sweltering heat. Such cycling will kill it.

Again, I love Mark's video!

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Mark Rowley
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Re: Neutron Irradiated Dime REDUX

Post by Mark Rowley » Tue Oct 27, 2020 9:43 pm

Thanks Richard. I’ve totally caught the activation bug and I doubt there’s a cure!

I gotta add Manganese as a good activation material. The 850keV Mn56 photopeak is big! Reminds me of Cs137.

Mark Rowley

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Richard Hull
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Re: Neutron Irradiated Dime REDUX

Post by Richard Hull » Wed Oct 28, 2020 4:46 am

Manganese is a medium tough one to get. I did it following the instructions of Carl Willis. Super saturate a gallon of water with manganese sulfate....Irradiatethe jug. The water is the moderator for the saturated manganese sulfate. Put up to your gamma spec.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Bob Reite
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Re: Neutron Irradiated Dime REDUX

Post by Bob Reite » Wed Oct 28, 2020 10:41 pm

Silver foil is the best for someone on a tight budget. You can get a "book" of 20 2.5" X 2.5" sheets of 0.999 silver foil for around 25 USD.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.

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