Karavaeva N. Composite scintillators based on single-crystal grains.

The thesis is devoted to design the new scintillation material, namely composite scintillators on the base of grains of stilbene and p-terphenyl single crystal for detection of fast neutrons, alpha-particles and on the base of grains of Ce:GSO or Ce:GPS crystal for thermal neutrons detection. The proposed composite scintillators are obtained by the following basic stages: a choice of scintillation material, a method to grind it to obtain grains, a choice of the optimal size of grains, a technology of introduction the grains into silicone base that is not a scintillator, a choice of the optimal proportion of the components, a determination and an application of a light reflecting coating. For each the task the optimal composition of the composite scintillators with different type of grains, binding basis, relative concentration of crystalline grains in silicone matrix has been found. A combined detector for selective spectrometry of fast neutrons and detection of thermal neutrons in the presence of gamma-radiation has been proposed and investigated as well. It consists both of the composite scintillator containing grains of an organic stilbene single crystal and of the composite scintillator containing grains of an inorganic Gd-bearing crystal. To separate the signals from these two parts of the combined detector it was used that these signals are in different scintillation amplitude ranges (~ 104 and 102 - 103 scintillation photons respectively).