Dear Muhammad

You need to define particle energy as distribution for 2 gamma rays (1.17 and 1.33 MeV).

MCNP input:

SDEF POS 0 0 0 ERG=d1 PAR=p

SI1 L 1.17 1.33

SP1 1 1

MCNP calculates scores per one source particle. So you need to multiply results with activity in terms of becquerel.

I recommend you to read this manual. There are examples for many situation.

https://www.mne.k-state.edu/~jks/MCNPprmr.pdf

Dear Muhammad;

You need to read UserGuide carefully. There you will find the source definition and "Point Isotropic Source with Discrete Energy Photons". You need to define the discrate energies of Co-60 in the definition as;

----- Source: point isotropic source with 4 discrete photon energies

SDEF POS 0 0 0 ERG=d1 PAR=2

SI1 L .3 .5 1. 2.5 $ the 4 discrete energies (MeV)

SP1 .2 .1 .3 .4 $ frequency of each energy

I think, it will help you.

Warmest Regards

Çağrı Yazgan Huseyin Ozan Tekin Thanks for answer

I agree with Yazgan' answer , although I use PAR=2 , not PAR=p, but probably this is equivalent.

If you wish high accuracy:

SI1 L 1.1732 1.3325

SP1 0.99974 0.99986

Regards

When the source dimension is negligible compared to the detector dimensions.