Design of an explosive detection system using Monte Carlo method.

Regardless the motivation terrorism is the most important risk for the national security in many countries. Attacks with explosives are the most common method used by terrorists. Therefore several procedures to detect explosives are utilized; among these methods are the use of neutrons and photons. In this study the Monte Carlo method an explosive detection system using a 241AmBe neutron source was designed. In the design light water, paraffin, polyethylene, and graphite were used as moderators. In the work the explosive RDX was used and the induced gamma rays due to neutron capture in the explosive was estimated using NaI(Tl) and HPGe detectors. When light water is used as moderator and HPGe as the detector the system has the best performance allowing distinguishing between the explosive and urea. For the final design the Ambient dose equivalent for neutrons and photons were estimated along the radial and axial axis.

X-ray spectra and doses.

Using the Monte Carlo method the x-ray spectrum produced by 150keV electrons colliding with W, Rh and Mo targets were calculated. The x-ray spectra were calculated to 20, 50, and 100cm from the focal point. In order to analyze the effect of the filter, calculations were carried out with and without filter. The spectra were used to estimate the Kerma in air, the Ambient dose equivalent, and the Personal dose equivalent. The spectra were integrated in energy to obtain the total photon fluences. Calculated spectra depend on the type of target having the continuous spectrum due to bremsstrahlung and the characteristics x-rays. The Al filter eliminates the low-energy photons; however no effect is noticed when the photon energy is larger than 40keV. The largest effect of dose reduction due to the filter was noticed to 20cm for the Kerma in air.