École Nationale Supérieure de
Techniques Avancées

Abstract

I have developed a Monte-Carlo simulation for the eight coaxial detectors of the ANNRI setup at MLF, J-PARC. I have generated the geometry of the detectors using the Geant4 toolkit and I have used experimental data acquired in December 2014 (one active coaxial detector) and in June 2018 (6 active coaxial detectors) in order to validate the simulation. I have used data from three different radioactive sources namely Cs 137, Co 60 and Eu 152 as well as data from the Cl 35 (n,gamma) reaction. For the validation, I compared the efficiency of the detectors to the simulated efficiency using 10 distinct gamma-ray peaks from the sources ranging from 662 keV to 8578 keV. I also compared the energy distribution from ANNRI's data with my simulation for both Cs 137 and Co 60. Finally, I simulated and compared the hit classification pattern of ANNRI with the actual data. The simulation has a maximum deviation from data of up to 10 %. The simulation was then used to implement the ANNRI-Gd model for the Gd 157 (n , gamma) reaction with good general agreement. The coaxial detectors of ANNRI play an important role in measuring angular correlation in successive gamma-ray emission from nuclei.