Base level source - Radioactive isotope sources

Links to primary sources of hardware and other materials for the amateur scientist for assembly and operation of a fusion system. General useful supplies for the experimenter are also allowed. Make title specific to the URL supplied with any needed information.
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Richard Hull
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Base level source - Radioactive isotope sources

Post by Richard Hull » Mon Apr 26, 2021 4:35 am

The main source for license free sources for all of us (general license holders - American citizens) are the NRC special license free limited quantity sealed sources. These are most often needed to calibrate instruments, especially Gamma spectrometers which a number of us possess. Note: these are in the $75.00 each and up sources and are not calibrated as to precise activity! This is not important at all for calibration of gamma spectrometers. If, however, you demand precisely 1uCi of Cs137, be prepared to dig deep into your stash of loot. I have ordered many times from Spectrum Techniques. They are the pro's in this area.
I remember when $35 would get you a 10uCi source of Cs137 (1970's), but times change. You will pay real money, but get a pure source for sure. They can cook up special amounts within the NCR maximum license free amount. C14 can go to 100uCi the last time I checked, but that was 4 years ago and cost nearly $400. The listed isotopes on their site are quantities they can instantly supply. You can request more or less as I note within the NCR limits. Drag down the current NRC list of isotopes with the max amount listed. Sr90 is limited to 0.1uCi....I think C14 is one of the max limits at 100uCi

http://www.spectrumtechniques.com/products/sources/

To save you wandering about their site here is their URL to the only isotopes they offer. Contact them about the specific amounts and prices of what they can or will supply.

https://www.spectrumtechniques.com/supp ... formation/

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: Base level source - Radioactive isotope sources

Post by Mark Rowley » Mon Apr 26, 2021 8:54 am

These are the three which I find most useful for gamma spec calibration. Eu152 works really well due to its wide range of photopeaks.


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Richard Hull
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Re: Base level source - Radioactive isotope sources

Post by Richard Hull » Mon Apr 26, 2021 2:50 pm

It is tough to beat good old Ra226 due to its many daughter peaks. (Goldie locks and the 3 bears among them.) The same goes at the high end for Thorium ore, monazite sand, or 40 year old plus lantern mantles. I have about 6 different sealed disk sources from Spec Tech. Co60 and Cs137 are among my favorites. Thallium 204 is a great beta source. I also have a 1lb bag of KCl for its high end gamma line. With a gamma spec, one can pick and choose among many easy to obtain gamma emitters in the public domain. If I were limited to just one cal source, I would go with Ra226. It easy to get by anyone and at a very low cost. Old watches, clocks, toggle switches, mil surplus aircraft meters, etc., abound. I use my mom's really large old 1940's Wesclox "Big Ben" for my Ra226 cal source. It's effectively sealed. But a nice monster chunk of hot U ore is just as good. The Big Ben just boasts pure Ra226, so it is my reference.

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: Base level source - Radioactive isotope sources

Post by Mark Rowley » Mon Apr 26, 2021 5:31 pm

Ra226 is great and it’s commonly used over here for calibration as well. Hobby MCA’s like PRA, Theremino, and Becqmoni seem to be more susceptible to calibration inaccuracies over a long energy span than what’s seen in the professional systems. For example, if you calibrate from 50-600KeV, obtaining accuracy in the Co60 range is typically unlikely. Even if you use two sources (Ra226 and K40) for calibration, the zone from 700KeV to about 1200KeV is still out of whack. To a smaller degree this is even seen in the 500KeV range. That oddity was the main reason I purchased a Co60 source from ST. Using multiple sources simultaneously or the Eu152 seems to greatly assist when calibrating for the entire range of the spectrometer.

Realistically, the need for such a wide range of calibration is uncommon. Usually one generally knows what they’re looking for and can choose a source to calibrate for that region. And most of what we do on an amateur level falls within the Ra226 spectrum.

My ST sources are usually locked up but the spectrometer always has a vintage Ra226 test disc from a PRI 111B gamma scintillator at the ready.

Mark Rowley

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Richard Hull
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Re: Base level source - Radioactive isotope sources

Post by Richard Hull » Tue Apr 27, 2021 5:47 pm

Agreed. The key thing is to have an idea of what you are dealing with or looking for and calibrate around it. Even pro machines like Canberra's can have some non-linearity over vast spans. Oddly, the most linear Canberra I ever owned was an old 8100 that I bought off of my pal Bill Kolb. I later bought a more modern Canberra as did Bill. Bill now owns the modern Spec Tech 30. Both of us agree that we never owned a more linear gamma spec than that old 8100. Was it just a lucky draw, made on a Wednesday? Odd how most all classical pro gamma specs vary in linearity, even the more modern ones. I guess that is why the need for cal sources. Tune for minimum slop around what you are looking for.

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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