Optimization of detector response simulations for multiple particles created by neutron-induced reactions

This research introduces the design of the optimized Pulsed Neutron Facility (PNF), which consists of a D-T neutron generator, a fueled graphite monolith, and a detection system, and studies the optimization of detector response simulations for multiple particles created by neutron-induced reactions. Neutron Activation Analysis (NAA) method was used to investigate the influence of the trace element, chlorine, in the biological system of the human body using the Monte Carlo simulation toolkits. Even though one of trace elements, chlorine, has a strong signal of the characteristic γ-rays by neutron capture reactions, it never has been used for in vivo detection of the cancer, previously. In this research, the possibility to detect some cancers by using the chlorine was discovered by comparing the concentration of the chlorine between normal and cancerous tissues. Based on the MCNPX simulations, the initial research focused on optimizing the yield of thermal neutrons in the PNF system, which can then be used as a source for the interactions with the biological sample while minimizing the background radiations. Moderating layer materials and fuel configurations of the graphite monolith, and the shielding configurations of the detection system were considered for the optimization. Through the GATE simulations, the detector responses by multiple particle interactions with biological sample were studied for the optimized concentration sensitivity of the chlorine between the normal and cancerous tissues considering various detector types, and thicknesses as well as different shielding configurations of the detection system. γ-ray spectra were analyzed, energy depositions by individual particle were calculated, and the normalized count ratio was defined for determining the optimized sensitivity of the chlorine isotope between normal and cancerous tissues. Three detector materials were considered: HPGe, CdTe, and NaI. At the peak of 8.58 MeV, the NaI detector has a better sensitivity of the chlorine than the other two detectors. Even though the HPGe detector has the best resolution, it has the worst sensitivity. Using the Monte Carlo simulation toolkits, the optimized PNF and detection system were proposed as a novel concept for strengthening the sensitivity of the characteristic γ-rays by neutron-material interactions