# Fraction of OPT-PROD

Dear FLUKA expert,
I simulate n+p–n’+p’ and generate optical photon.At OPT-PROD,the fraction is generated photons’ energy divide incident particle’s energy,but neutron can not generate optical photon as we know,so I want to get optical photon’s fluence by secondary proton,How should I do?

Another same question is I want to simulate the influence of mixture ratio(LiF:ZnS) to photon production,if I set the fraction as a constant,the consequent photon number seems only related to the ratio and can not get the result,How should I do?

Dear Xiong,

1. The fraction of the optical photons is the ratio between the generated optical photons’ energy and the energy deposited in the region. This means, if a neutron deposited energy in the region (even through secondary interactions), it is contributing to the production of optical photons.

2. The change in material composition only influences the energy deposition in the region producing the optical photons. If the change in the material mixture is minimal, then the energy deposition won’t change much also. However, this change in the material could cause a significant change in the optical photon production in reality, which FLUKA cannot calculate. Thus, it is the user’s responsibility to provide the appropriate optical production fraction for the specific material composition.

Cheers,
David

Dear@horvathd ,
I want to calculate how the material mixture ratio influence optical photons’ production,so I get a idea and please help me to see if it right:
I use one USRBIN to score energy, and another USRBIN and AUXSCORE(optiphot) to score photons’ energy,then the ratio of them is the fraction.

Dear Xiong,

unfortunately this is not possible to do with FLUKA.

FLUKA is only capable to simulate photon production via interactions down to 100 eV energies, while the optical photons are in the 2-3 eV energy range.

Thus, the treatment of optical photons in FLUKA is a completely separate process, which is dependent on the user provided production fraction.

Cheers,
David

Dear@horvathd ,
I have just tried it,if I want to do any simulation relate to optical photon,the fraction is inevitable,but to some extent, the fraction is exactly the value I want to get.That is to say I can not do this simulation? Is there any way to circumvent this problem？

Dear Xiong,

yes, the FLUKA simulation you describe will only give you the same fraction that you provided.

You need to use other method / simulation software to get the optical photon yield of different material compositions.

Cheers,
David

Dear@horvathd ,
Thank you for your help,by the way, any method / simulation software recommend?

Dear Xiong,

personally, I’m not aware anything capable for this kind of calculation.

Cheers,
David

Dear@horvathd ,
That’s OK,thank you!