NOVICE 3-D transport code simulation of directional photon sensors

This study describes simulations by an adjoint, Monte Carlo code (NOVICE) of directional gamma ray and X-ray photon sensor responses in detecting and locating radiation sources. Three types of sensor designs were studied. Models of each detector type, ionization chamber (IC), scintillation counter (SC), and a new high-sensitivity scintillation sensor (HSSS) were generated in the code and various radiation sources were detected and located by applying the program. Comparisons with experimental results show that the code accurately simulates the responses of those sensors. The program includes the physics that control and describe the photo-Compton and pair interactions for incident angles of photons on the high/low-Z detector layers, ranging from 0 to 90 relative to the plane of the layers. The small grazing angles of incidence (near zero degrees) must be accounted for in any theoretical simulation since the directional sensors' operating principle depends on the emission of photo-Compton and pair electrons for small incident angles as a function of atomic number Z and energy. NOVICE contains the necessary theory and also provides 3-D solutions for the sensors, experimental geometries, and setups. The effects of detector high/low-Z materials, their dimensions, and geometry, were investigated. (orig.)