Fusor Forums

Hi Guys,

I have been playing around with some gamma spectroscopy, and after taking spectrums of all my known sources, I got desperate, and took this overnight spectrum from the tiny check source on the side of my Leni geiger counter.

There are clearly some identifiable bumps there, but what is the substance?

I have drawn in some approximate values, based on my check sources.

Steven

Here is a link of some common check sources used on survey instruments that could be of some help.

http://www.orau.org/ptp/collection/civi ... ources.htm

Just a guess, decay products from radium would have some peaks aroud 240, 295 and 350 from Pb214. This would also have Bi214 around 660. I would guess the peak at the far right (about 1400?) to be K40 from background? But it does look weak indeed. It is also difficult to tell how linear your scale is.

Just a guess, others on this site are much more qualified than me for this!!!

have fun!

Yes Potassium K40, (prob)
Try it again on the salt
Steve.

Hi Steven,

Those CDV sources are usually either DU metal chips or a so-called "Radium D-E" source (Pb-Bi-Po-210).

Your spectrum is a bit difficult to interpret because of a heavy continuum of counts drowning any real distinct peaks.. If you can get a single-isotope, single-energy test source (e.g. Cs-137) to aid in setting up your audio pulse-shape processing, you will get much better results out of this apparatus. It's possible to do quite well with it as I have found, but it's not exactly "plug and play" for scintillators.

-Carl

Carl,

I already have three check sources, Am241, Ba133, and Cs137, and with my new USB bias, it really is plug and play. See pdf spectra below, I am getting really good definition.

I might send you one of these plug and play USB modules, they would be great on your fossicking trips

Steven

Wow - Jon you need to watch out - the apprentice may challenge the master


Congrats Steven - a great effort

I think you have a weak natural uranium or radium source. Lotsa' bumps usually mean radium or natural U ore.

Based on your collection time, I think you are looking at background and there is not a real sorce there at all.


Richard Hull

If it's anything like the ENI's that I have then it has a that the check source is most likely what they call a "Radium DEF" source. According to my research it's actually just a generic radium266 source with a number of radium daughters and various contaminants. Pretty much just a mix of radioactive debris, the quality control was miserable on these things.

The DU check sources that I have are several times more active than the sources on my ENI's which makes it very easy to discriminate between the two.

I'm wondering if the 230k peak is actually the Bi & Po K x-rays around 200k:
http://www.radiochemistry.org/periodict ... /ra226.pdf

If you want to really dig into it knock yourself out here:
http://ie.lbl.gov/decay.html

I am in the background radiation or weak shielded source camp here too. Check out for a relalvent experment. viewtopic.php?f=18&t=7754#p55713

Mild shielding from dirt, walls or any other Z including air will affect the lower energy peaks the most and can turn them into a continuum. Higher energy peaks will be less affected and could explain why you see higher energy bumps but a big undefinded mass of lower energy photons.

Frank Sanns