Gold 198 and Radiacode 101

[MikeD99]

Hi,
I'm new to the forum.

I have an Amstat NucleSpot and a sheet of Beryllium as a Neutron source. I have the combination inside a mountain of Polyethylene plastic blocks and can detect about 65 Neutrons per second with a Neutron detector SI19N tube and a Schmitt trigger from Steven. I have 'baked' some gold foil for four days, as Carl Willis puts it. I notice an increase of gamma activity before vs after with a GC Electronics GMC 600+.

My question is: Why don't I see a signature from Au198 on my Radiacode 101? Is there a way for me to specifically detect the decay of the radioactive Gold?

Will I get more Neutrons from a thicker piece of Be than a thin pc?

Thanks,
Mike Driscoll
Leesburg, Va USA

[MikeD99]

I re-read my post again and noticed that I meant to say 65 Neutrons per Minute, not per second.

Sorry,
It seems like no matter how hard I try I cannot avoid making mistakes!

Mike Driscoll
Leesburg, Va USA

[Sesselmann]

Mike,

I dont have hands on experience with this experiment, but from the table it looks like the activation half life is around 2.7 days and the main gamma around 411 keV.

http://nucleardata.nuclear.lu.se/toi/nu ... iZA=790198

Could it be that the 411 keV is drowned out by something else?

What shielding do you have for the spectrum analysis ?

Steven

[Rob Tayloe]

When I taught at the Ohio State Univ Nuclear Reactor Lab we had access to a much higher thermal neutron flux and often activated small gold foils. Alas, with a neutron source emitting only about 1 neutron per second it is unlikely that a measurable activity will be produced in a gold foil. Below are some results using an on-line calculator for neutron activation. I assumed a 50 mg Au foil placed in close contact with the source for 4 days. Results indicate activities well below 1 dis / sec (Bq) are expected. -

Point source neutron emission rate = 1 per s
Distance from point source = .01 m
Neutron flux = 79.58e-3 per cm2s
Irradiation = 4 d; Delay = 15 s

Original Reaction Activation (->) Half-
Nuclide & Decay (~>) Life
Products


50.00 mg Au-197 (n,G) -> 771.1 µBq Au-198 (2.696 d)

We found the results from the on-line calculator to be pretty accurate for thermal neutrons. It was a useful tool for planning experiments. The calculator can be found at the link below -

https://www.wise-uranium.org/rnac.html

[Rob Tayloe]

As I recall from one of Carl Willis' videos, he used a Po-210 alpha source (available commercially for use in static control) with a Be foil. I don't recall the strength of the resultant neutron source, but he did get some measurable activation. If one is going to experiment with more intense sources it is advisable to have access to (and use!) appropriate dosimetry, lab safety procedures, and shielding.

[Rob Tayloe]

Below is a link to Carl Willis' YouTube video of his Au-197 neutron activation experiment. His estimate of his neutron source strength was around 10^3 neutrons per second.

https://www.youtube.com/watch?v=RKyIm-o30GE

Another Carl Willis YouTube video on making neutron sources -

https://www.youtube.com/watch?v=uQ8vwevCq8Q

[Rob Tayloe]

I ended up watching (or re-watching) a number of Carl Willis' videos. These are pretty interesting. One looks at the light emission from various scintillators when exposed to radiation. Link is below -

https://www.youtube.com/watch?v=Gza6Cc8XOCA

[MikeD99]

Hi, all,
Thanks for answering. I have a Po/Be neutron source like Carl's. Mine is nice and fresh so I estimate 1500 neutrons per second. I am only measuring 112 per minute with a different tube. I am pretty sure that I really am seeing neutrons. So I have it in polyethylene blocks about 6 inches all around. I just rested the radiacode 101 on the gold foil after taking it out of the poly blocks. Do I need shielding with that? I had hoped to just ignore the non-gold spikes.

I appreciate your help as I really have little idea what I'm doing. I like Carl's videos. I am re-creating many of them.

Does a thicker Be metal make more or fewer Neutrons whem placed upon the NucleSpot?

I have some 1/16 or 20 ga lead sheet. should I make a little cage for the gold foil and Radiacode 101? Some people seem to favor hundreds of pounds of lead blocks.

Thanks you again,
Mike Driscoll

[MikeD99]

I just got some lead blocks 'delivered.' My mailman is a woman who does not like to lift heavy packages so I had to go to the post offe 30 minutes each way to pick them up because they were "too heavy." I guess I should get the postage back then right? Oh, no the guy at the loading dock 'accidentally' checked that they were dropped off at my house. Eight times (accidentally).

So I soon will be able to isolate my radiacode 101 to try to detect Gold activation. Do you have any tips?

Thanks,
Mike D. Leesburg, Va USA

[Phouly]

Hi Mike, I think once you have a good lead shield around the foil and detector you will have a lot better chance of seeing the 411kev gammas, since 2000 n/s is quite low you are going to have to remove most of the background radiation to see it.