Na-22 beta spectrum

We simulated Na-22 source using Geant4 10.4.2 (Livermore) for our calibration data with NaI(Tl) detector. We compared the simulated energy spectrum with our data and found that gamma peaks well describe the data. However, beta+ energy spectrum is not in good agreement with data.

  1. We are now wondering if it is validated not only for gamma but also betas(x-rays, Auger electron, conversion electrons).
  2. Or, there is any possibility to be wrong.
    Because we found that a non-Gaussian peak around 50keV originating from beta decays of Pb-210 was not simulated correctly with Geant4.9.6. Similarly, it may happen in the Na-22 simulation with the version of 10.4.2.

Thank you.


the story between 9.6 and 10.4 includes intensive development in this sector. Since 10.4 practically all data for isotopes, nuclear levels, transitions are updated according to recent versions of world DBs. There are limited number of transitions, which are under questions. Usually it is the case, when a user has better specific data then data in DBs.

Beta decay is a normal part of the radioactive decay module. If your see biased spectrum, you need to show it and to describe how it is obtained.


Thanks for your response.

We compared the simulated Na-22 beta+ spectrum with the measurements from reference (Nuclear Physics AI09 (1968) 561-576).

In the figure, black is simulation and blue and red lines are measurements; blue is measured in coincidence with the gamma sum (2.298MeV). As shown in the figure, they are not matched and I am worried about the simulation of Na-22.

I am wondering how Na-22 e+ energy is calculated in Geant4.10.

Here, beta spectrum as generated by Geant4.
jeon.mac.txt (256 Bytes)

What version of geant4 did you use?

Geant4 10.7

jeon.out.txt (2.3 KB)

We have tested it using 10.7.2 and got the result. We compared the new result(red) with that of 10.4.2(black).

We found the difference of in two different versions. That was caused by the sign of daugherZ value.

Thanks a lot, Maire!!