# The primary particle about Cs137 Isotope source

Dear FLUKA experts,
I try to define an isotope source(Cs137). As we know ,Cs137 decays and emitting 0.512MeV (94.7%) and 1.174MeV(5.3%) electrons into the excited and ground states of Ba136, and then Ba136m transitions back to 136Ba by emitting γ photons(0.661MeV).
So when I use the DETECT Card to get the spectrum, Is there an element of electrons β negative decay emission?

Dear Qinqing,

yes, the electrons from \beta^- decays are simulated, in addition to the photons.

Also, since FLUKA 4-2.0, the alpha particles are also generated and transported when alpha decaying isotope is used.

Cheers,
David