[Gate-users] unexpected energy distribution

[Luca Pesce]

Dear Gate Users,

I'm simply trying to take the electron energy spectrum from a decay in a box of water, considering the above electromagnetic effects:
compton, photo electric, gamma conversion, electron ionization, bremsstrahlung, positron annihilation and multiple scattering.
To ensure that my final analysis is realistic, I try to test a monochromatic electrons source obtaining the obvious expected result.
Sure of this, I have changed the source with the unstable isotope 89-Sr, and I have obtained a strange result in the spectrum: there is a high peak in the low energy instead the electron energy spectrum of the beta decay. 

I don't understand why in the case of the non monochromatic source this fact happens.
Any idea of why?

Regards,
Luca Pesce,
Pisa University Student.