Monte Carlo method simulation of the instrumental function of a device for observing angular correlation of annihilational γ-quanta

The program of Monte Carlo method simulation of the 70 keV-10 MeV γ-quantum recording process by a scintillation detector with light collecting account in the scintillator and statistic model of multiplication process in a photomultiplier. On the basis of using the Monte Carlo method analogue flowsheets for determining annihilational γ-quantum escape from the investigated sample and the program of process simulation of their recording by a scintillation detector the effect of geometric dimensions of positron annihilation zone in the sample on the instrumental function of the experimental device for observing angular correlation of annihilational γ-quanta. Using the algorithm described the calculations of the light collection coefficient (LCC) have been performed for the NaJ(Tl) cylindrical scintillator without reflecting coating application. It is pointed out that the value of the LCC calculated using the Monte Carlo method is much lower than at numerical integration. This difference is explained by the absence in numerical integration of account of scintillator absorption coefficient dependence on light flash wavelength. The instrumental function calculations carried out give the possibility to determine optimum geometric dimensions of samples investigated by the positron annihilation method. The instrumental function account at the reconstruction of the angular correlation curve derivative of the two-quanta annihilation of e+e- pairs provides the possibility to essentially specify the angular curve form and to determine positively the Fermi pulse value. On the base of a good agreement between the calculated and experimentally measured function of scintillator detector response the conclusion is drawn on the applicability of the suggested algorithm and programs for simulation of γ-quanta recording processes by a scintillation detector