⁹Be(γ, n)⁸Be

Photonuclear reaction:

• overcome the binding energy of nucleus
  
• threshold at E=1.665 MeV for ⁹Be
  

1) Setup and source

Point source: γ-rays at 2614 keV for ²²⁸Th and 2204 keV, 2448 keV for ²²⁶Ra

2) Photonuclear cross-section

Cross-section of γ photons with the Be	γ-rays in the Be target

• photonuclear data library: ENDF7u https://nucleardata.lanl.gov/ace/endf7u
• comparison with the current data library https://www-nds.iaea.org/photonuclear/
• very small → biased technique and set a cut at 1.665 MeV to save the computation power
• A preliminary simulation using 10^9 γ photons at the 2614 keV is shown below,

Photoneutrons emitted from the surface of the Be target	The neutron energy spectrum in the GAGG crystal

3) A toy simulation

• 20 MeV uniformly injected on a cylindrical Be target (thickness 1 mm, diameter 1 cm)
• the target is surrounded by a sphere and the neutrons crossing the surface is accumulated.
• compare with the literature (https://www.sciencedirect.com/science/article/pii/S0168583X24000624) Fig.1.
• the spectra are similar, but the magnitude diverges, need more check
• change the γ energy to 2.614 MeV and the Be target thickness to 4 mm, 2.4 cm

Photoneutrons escaped from the surface of the Be target	Neutron spectra generated from 2.614 MeV γ photons with different Be thickness

Is there secondary interactions related to the setup?

• different configurations with the PE moderator
• neutron flux is calculated from a box volume surrounding the Be target (the y axis unit is different from the previous plot)

Photoneutrons escaped from the surface of the Be target

• varying the Be target thickness
• neutron flux is calculated from a box volume surrounding the Be target

Photoneutrons escaped from the Be target	Photoneutrons from the GAGG crystal

5) Simulation with the ²²⁶Ra source emitting γ-rays with 2448 keV and 2204 keV

With the corresponding emission probability of γ photons at the two energies, in total 10^9 particles are simulated. The results are seen below,

^ γ-rays in the Be target ^

Photoneutrons escaped from the surface of the Be target	Photoneutrons in the GAGG crystal
Photoneutrons escaped from the Be target	Photoneutrons in the GAGG crystal

6) Al plate

7) Source locations

 /home/yingjiechu/simulation/gagg/Ra_Be/about.txt
 /home/yingjiechu/simulation/gagg/Ra_Be/2614/about.txt