Gamma spectrometry: Calibration using X-ray emissions

[Oliver-BfS]

I have just done an efficiency calibration measurement for the HPGe detector of a whole-body counter. Ba-133 and Eu-152 were the calibration nuclides. For a calibration at low energies I thought of using the X-ray emissions of both nuclides as well. However, the result looks quite bad - see the attachment.

The peak at 45.6 keV originating from Eu-152 is far too small compared to the X-ray peaks at 30.8 and 35.2 (Ba-133) and at 39.9 (Eu-152). A difference between the emissions of Eu-152 and Ba-133 is possible because of a slightly different distribution of the sources within the phantom. (I used a brick phantom with rod sources.) However, what might be the reason for the difference between the two emissions of Eu-152? The problem occurs also in repeated calibrations so the small number of counts at 45.6 keV is not a random event. The abundance of the X-ray emissions at 45 keV was entered as 14.82%, that at 39.9 keV as 58.5% - values that I found both on nucleide.org and on nucleonica.net. Thank you for your help!

 

[mfb]

How did you estimate your count rates?

The abundance of the X-ray emissions at 45 keV was entered as 14.82%, that at 39.9 keV as 58.5%

Do they both refer to the same base value?

 

[Oliver-BfS]

The count rates were estimated by fitting Gaussian functions to the peaks. This is done automatically by the software (Canberra's Genie 2000). Summing up the numbers of counts per channel and subtracting the continuum background yields a similar number of counts.

Nucleide.org (PDF-File, page 8) reports the abundance as emitted photons per 100 disintegrations.