NOVICE 3-D TRANSPORT CODE SIMULATION OF DIRECTIONAL PHOTON SENSORS

This study describes simulations by an adjoint, Monte Carlo code (NOVI CE) of directional gamma ray and X-ray photon sensor responses in dete cting and locating radiation sources. Three types of sensor designs we re studied. Models of each detector type, Ionization Chamber (IC), Sci ntillation Counter (SC), and a new High-Sensitivity Scintillation Sens or (HSSS) were generated in the code and various radiation sources wer e detected and located by applying the program. Comparisons with exper imental results show that the code accurately simulates the responses of those sensors. The program includes the physics that control and de scribe the photo-Compton and pair interactions for incident angles of photons on the high/low-Z detector layers, ranging from 0 degrees to 9 0 degrees relative to I:he plane of the layers. The small grazing angl es of incidence (near zero degrees) must be accounted for in any theor etical simulation since the directional sensors' operating principle d epends on the emission of photo-Compton and pair electrons for small i ncident angles as a function of atomic number Z and energy. NOVICE con tains the necessary theory and also provides 3-D solutions for the sen sors, experimental geometries, and setups. The effects of detector hig h/low-Z materials, their dimensions, and geometry, were investigated. (C) 1998 Elsevier Science B.V. All rights reserved.