Why is a 59keV Am241 needed to see the Cs137 32keV?

[keuleeule]

Hi all,
I really dont understand.
If I do a Cs137 Scan, I cant see the 32keV peak, thats why I wonder how to calibrate with only a prominent 662keV peak.
If I place to that source as well a Am241 source, the 32keV peak is visible left to the 59keV Am241 peak, why not if I only have my Cs137 in?

Same parameters, same calibration. The "y" of the Pulseheight Histogramm is different, as the Am241 peak is much higher, so which knop I need to adjust to see the 32keV peak in the "only Cs137 spectrum"?

hope to get some clarification... Kolja

[Sesselmann]

Kolja,

This seems like a strange problem, but i am sure it has a simple answer.

I have seen a missing 32 keV peak before, where it turned out that the count rate was too high, so just moving the source a bit further away fixed it, but that doesn't appear to be your problem.

I see you have the advanced filter switched on, is it possible that your tolerance is set too tight in the advanced filter?

Typically the 32 keV peak will disappear first when you tighten the tolerance, this is simply because the signal to noise ratio is higher at the low end.

Last, is it possible your Cs-137 source is inside something that might shield the x-ray?

I'm not convinced that the little peak on the left is Cs x-ray, because Am also has this bump.

Steven

[keuleeule]

good point Steven,
maybe the source is the problem...
It is a professional calibration source, and it seems to be aluminum capsuled. Maybe enough that the 32keV cant pass through.

And I double checked your statement, correct if I only measure the Am241 source, I do have a left peak beside the 59keV peak.

Ok, So I will use a mixture of Cs137 and Am241 and select only the known 59keV from Am241 and the 662keV from Cs137 for calibration.
Thanks for the help!
Kolja

[Peter-1]

Hi Kolja,

i have tested my Cs probe to see what happens with aluminium filter.Hope you can see that the aluminium dosen't eliminate the 31.8 keV peak.

Cs137-Alu.jpg

Peter