Monte Carlo simulation of nuclear logging detection systems

Abstract

The utmost challenge in nuclear logs interpretations and spectroscopy comes from the complex and dynamic structure of the radiation detectors response function. To interpret accurately such logs, the energy spectra for several dimensions of nuclear logging detectors must be satisfactorily known. In this work, different incident photon track and energies owing to events occurring into the gamma ray detector are simulated by the Monte Carlo method. The life of a particle within a NaI(Tl) scintillator crystal is computed by simulating the position, direction and energy of electrons and gamma-ray photons interaction by interaction. Four types of photon interactions are computed, namely, photoelectric absorption, pair production, and Rayleigh and Compton scattering. The specific energy loss due to ionization and excitation for electron are also computed. These pulse high spectra are determined by collecting the radiation and transforming it into current pulses. The spectral distribution of these pulses results in a matrix of detector normalized response functions for multiple and complicated source geometry linked with all gamma ray incidence normally required on borehole environment. These data are displayed in such a way that they can be readily carried out into all nuclear log modeling processes with relevant detection effects.Key words: Monte Carlo Method; Na I (Tl) detector; Nuclear logging. SIMULAÇÃO MONTE CARLO DOS SISTEMAS DE DETECÇÃO DE PERFILAGEM NU-CLEAR -O grande desafio da interpretação e espectroscopia dos perfis nucleares resulta da estrutura complexa e dinâmica da função resposta dos detectores de radiação. Para interpretar adequadamente tais perfis, os espectros, para várias dimensões de detectores de sistemas