Entwicklung hocheffizienter, #gamma#-insensitiver Detektormaterialien und Bildplatten fuer Neutronen

Neutron image plates provide the means for two-dimensional, position-sensitive detection of neutrons. Commercially available neutron image plates consist of a mixture of a neutron converter and storage phosphor dispersed in an organic binder supported by a flexible sheet. The aim of this dissertation was to find a system of converter and storage phosphor which shows a high efficiency for the detection of neutrons while at the same time features a low #gamma#-sensitivity. Additionally, the technology to fabricate neutron image plates based on this system with a spatial resolution of #<=# 1 mm"2 was to be developed. In order to reach this aim, first, the storage phosphors had to be optimised. Investigations on BaFBr:Eu"2"+ have shown that its sensitivity can be raised significantly by doping it with 1 mol% calcium. Additionally, the calcium doping increased the stimulability of the phosphor at the wavelength of 635 nm, which is important for practical applications. It was demonstrated that this increased stimulability is due to a calcium-induced formation of disturbed colour centres, i.e. F_A(Br"-, Ca"2"+), whose stimulation maxima are shifted by about 80 nm towards longer wavelengths compared to undisturbed colour centres. Furthermore, the method of linearly modulated photostimulated luminescence (LM-PSL) was used for the first time on BaFBr:Eu"2"+. With this method, which is using a linearly increasing intensity of the stimulating light, it was possible to determine the optical cross-sections of the centres responsible for the photostimulated luminescence (PSL). Additionally, the two storage phosphors KCl:Eu"2"+ and KBr:Eu"2"+ were investigated. It was found that the optimum activator concentration for highest photostimulated luminescence output is 0.05 mol% Eu"2"+. Doping experiments analogous to BaFBr:Eu"2"+ were performed on KCl:Eu"2"+ for the purpose of shifting the stimulation maximum to a longer wavelength and a linear correlation between the maximum and the bromine content was found. (orig.)Available from TIB Hannover: RA 831(4076) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman