Neutron captures

Dear professors,
I’m searching for all possible neutron captures on nucleus. My logic is to go through all low-energy neutron reactions (IFLAG = 3 in mdstck.f) with JTRACK = 8 and without KPART(IP) = 8 and record relative information. The problem occurs when I compare my result with G4 simulation. The number of neutron captures is ten times larger than that of G4. So, I’m wondering if my code is wrong or incomplete. I noticed that some of above generate gammas as secondaries and some don’t. Are neutron captures necessarily accompanied by gamma generation?
By the way, as I have included in mdstck.f, I want to confirm that ICRES and IBRES are the properties of the nuclei after reaction?
Best regards,
Hechong Han
mdstck.f (2.3 KB)
muon.txt (166.4 KB)
newsource.f (7.3 KB)
Te-LS.inp (3.4 KB)

Dear @hanhechong,

Thanks for your queries.

  1. Why are you only applying the point wise treatment to the Tellurium?.

Remember that, as it’s said in the note 3 of the manual:

Mixed materials can co-exist where some elements are treated point wise and some multi-group wise. This can be fine-tuned by the user mainly for computational speed purposes. Despite that is not really necessary since the new pointwise treatment adds some penalty in CPU time however with superior physics results.

I would recommend you to leave the LOW-PWXS empty to apply this treatment to all the materials

  1. Are you interested only in the neutron captures in the “LS” region?

If this is the case, be careful because your neutrons are interacting also with the the other regions.

  1. Regarding your question:

             Are neutron captures necessarily accompanied by gamma generation?

Yes, in general you should observe the gamma emission + the nucleus recoil. In your problem you can observe in many cases the following
Screenshot from 2023-06-02 11-32-31

What is it? A neutron captured, and the generation of a gamma and a deuteron as secondaries.
It seems that the mdstck routine considers also the elastic cases, this is the reason why you can also observe these cases:
Screenshot from 2023-06-02 11-36-35
Where you have the recoil of a carbon nucleus.

        I want to confirm that ICRES and IBRES are the properties of the nuclei after reaction?

I confirm you, and the FLUKA documentation in as well:

Screenshot from 2023-06-02 11-48-55

  1. I would say that if you just filter the cases where there is a gamma generation and a nucleus recoil, you can estimate the number of neutron captures.

  2. Related to the comparison with G4, first try to check if you observe any difference with this considerations, and if you still have this factor 10. Multiple reasons could generate this discrepancy , but that’s a topic to discuss later.

Have a nice weekend,

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