About the yield of 58Co

Dear experts:

I am calculating the yied of Cu-61 through proton bombardment of the Ni-61 target. Due to the reaction of (p,A), Co-58 will produced. Radiation time and cooling time are set as 2 hours. During the cooling process, the yield of Co-58 should be decreased due to the B+ decay. However, the results shows more Co-58 is produced. When the cooling time is 0,1,2 hours, the yield of Co-58 are 3.18, 3.38, 3.57 MBq.
So, the problem is, where is these growing Co-58 coming from?

Here is the input card.
NI64.inp (4.5 KB)

Best Regards
Xiaohe Wang

Dear Xiaohe Wang,

The reaction produces both Co-58 and Co-58m. Co-58m is shorter lived isomer which decays to Co-58, which has a longer half life. So while the isomer is decaying it will increase the activity of the ground state Co-58.
You can see this in the sum.lis output files. The activity of the isomer is decreasing, while - as you have observed - the Co-58 activity increases.

Kind regards,