** <sup>9</sup>Be(γ, n)<sup>8</sup>Be  ** 

Photonuclear reaction:
  * overcome the binding energy of nucleus  \\
  * threshold at E=1.665 MeV for <sup>9</sup>Be  \\


** 1) Setup and source **


^ Setup for the γ-n reaction, and the viewpoint from x-y and x-z  ^

| {{:gagg-nd:setup_foto.png?250|}} | {{:gagg-nd:setup_xy.png?450|}} | {{:gagg-nd:setup_xz.png?480|}} |


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

** 2) Photonuclear cross-section **

^  Cross-section of γ photons with the Be  ^  γ-rays in the Be target  ^
|  {{:gagg-nd:xs_mt_4.png?600|}}  | {{:gagg-nd:2614_gamma_be.png?600|}}  |
  

 
  * 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 ^
|  {{:gagg-nd:2614_photoneutron_be.png?600|}}  | {{:gagg-nd:2614_photoneutron_crystal.png?600|}}  |     

   
** 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 ^
|  {{:gagg-nd:toy_20mev.png?600|}}  | {{:gagg-nd:toy_be_configure_new.png?600|}}  | 
  
   
** 4) Simulation with the <sup>232</sup>Th source emitting γ-rays of 2614 keV **

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  ^
|  {{:gagg-nd:2614_pe_configure.png?600|}}  |    
 
  
  * 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 ^
|  {{:gagg-nd:2614_be_configure.png?600|}}  | {{:gagg-nd:2614_be_configure_neutron.png?600|}}  |     
   

** 5) Simulation with the <sup>226</sup>Ra 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  ^
|  {{:gagg-nd:ra_gammas.png?600|}}  |  

^  Photoneutrons escaped from the surface of the Be target ^ Photoneutrons in the GAGG crystal ^
|  {{:gagg-nd:ra_photoneutron_be.png?600|}}  |  {{:gagg-nd:ra_photoneutron_crystal.png?600|}}  |  
   
  * varying the Be target thickness 
  * neutron flux is calculated from a box volume surrounding the Be target  

^  Photoneutrons escaped from the Be target ^ Photoneutrons in the GAGG crystal ^
|  {{:gagg-nd:ra_be_configure.png?600|}}  |  {{:gagg-nd:ra_be_configure_crystal.png?600|}}  | 

** 6) Al plate **
  
  
** 7) Source locations **
   /home/yingjiechu/simulation/gagg/Ra_Be/about.txt
   /home/yingjiechu/simulation/gagg/Ra_Be/2614/about.txt