Essentially, this master thesis represents the experimental facet of the evaluation of a reactor neutron spectrum. In the course of the work conducted, neutron activation analysis measurements were performed at the TRIGA Mark II reactor at the Atominstitut of the Vienna University of Technology. The data obtained was used for an ongoing research project at the Atominstitut related to the neutron flux characterisation for the new core. The work included the selection of activation foils that would meet the requirements, the design of sample holders for different irradiation positions - in particular a horizontal beam tube and the central irradiation channel - as well as the planning and performing of irradiations and gamma spectroscopy measurements of activated foils. The activation foils that were used in the course of this work were chosen with regard to the pureness of the material and geometry considerations. The materials were gold, copper, indium, nickel, iron and aluminium. The reactions that were essential for covering the entire neutron energy spectrum included (n,g), (n,n') and (n,p) reactions, some of which exhibited threshold behaviour. The half-lives of the activation products were quite diverse, ranging from a few minutes, in the case of Mg-27, to almost a year in the case of Mn-54. The gamma spectroscopy measurements were performed in such a way as to minimize the statistical and systematic uncertainties. The irradiations were planned in order to achieve an optimal activation of the foils but within reasonable limitations such as radiological protection and time constraints. In the horizontal beam tube, irradiations were performed in three different positions along the horizontal axis of the tube. The collimator had been removed before these measurements. For irradiations in the central irradiation channel, a special sample holder, which allowed the irradiation of foils in eleven positions along the vertical axis, was designed. Since the irradiations were performed at different times and under varying circumstances, there was also on extra reference position for flux monitoring in the sample holder. The irradiations and measurements that were performed were overall very satisfying and provided useful data, which could subsequently be used for further research.