[Gate-users] Cannot get characteristic photons, gamma-rays from Gadolinium/Boron neutron cross section.

[Kurt V]

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Yes, the process requires a significant neutron fluence but, suppose I change the proton beam to a neutron beam that is heavily weighted to lower energies.

I aim the neutron beam on a Gadolinium based phantom. I still do not receive the prompt gamma rays and characteristic x-rays that should be represented from the interactions.

Gadolinium has an enormous cross section for thermal neutrons approximately 48890 barns. Soft tissue is approximately 0.1 b.
The main spectral signature for Gd neutron capture reactions for X-rays at 43 keV (Gd Ka) and 49 keV (Gd Kb), and gamma-rays at 79.5 keV and 181.9 keV.

Either a proton beam or especially a neutron beam on Gadolinium should produce photons with these spectral energies.
I am using around 1 million particles incident on a Gd Phantom with a NaI detector.

I have tried these physics builders: QGSP_BIC_HP, QGSP_BERT_HP, FTFP_BERT_HP. I have seen no capture reactions as a result.

I am starting to wonder if I do need an entire modified physics list.
Also, the modified physics list might require very specific physics models for this to work.
i.e. Protons -> Neutron Fluence -> thermal n + Gd Capture reaction -> gamma-rays + characteristic photons.

I am using the EnergySpectrumActor and can measure counts as a function of energy seen at the NaI detector. The only problem is that I am not seeing a representation of those neutron capture reaction energies measured at the detector. They should be clearly defined.

The primary problem is not seeing these capture reactions.

I’ll post an example of my macro, to provide greater insight.


As always, thank you for all the help, and all suggestions are greatly appreciated.
Thank you,
Kurt Van Delinder

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