Analysis of neutron diagnostic systems in large tokamaksŠtancar, Žiga (Avtor) Snoj, Luka (Mentor) plasma transportneutron spectrumneutron transporttokamakJETMonte Carlo methodneutron sourceTRANSPDRESSMCNPPLANETModern fusion neutronics studies play a crucial role in the support of the development of fusion devices. Their contribution varies from the design of plasma diagnostics systems, fusion power measurements, tritium breeding studies, evaluation of radiation induced structural embrittlement to radiation protection of personnel. Present-day neutron calculations are almost in their entirety based on advanced stochastic neutron transport codes. One of the foundations of these programs is knowledge about the neutron source, in our case a hot plasma. Since uncertainties in basic simulation parameters are being propagated through the system together with the neutrons, there is an ongoing effort of trying to identify and study major uncertainty sources and improving existing physics models for describing the generation of neutrons in a tokamak. The dissertation focuses on the description of the plasma as a neutron source and begins with a study of the state-of-the-art modelling capabilities of neutron emission in tokamak plasmas. The core of the thesis is the description and application of a novel methodology for generation of realistic plasma neutron sources, called PLANET. The methodology is based on calculations of plasma transport with the TRANSP code and neutron spectra with the DRESS code, coupled to the MCNP stochastic neutron transport code. Diagnostic data and modelling results of two representative JET deuterium fuel discharges are used for neutron generation in computational JET models, analysing basic source parameters - emissivity profile, spectra shape, source anisotropy and synthetic detector response. By comparing the realistic source results with a thermal plasma, it is shown that discrepancies of integral neutron detector response, from which the total neutron rate and hence the fusion power is calculated, of up to several percent are computed, exhibiting relatively low sensitivity to changes in the neutron source. The analysis of neutron spectra shows distinct structural characteristics which arise due to the fact that plasma heating and fusion reaction anisotropy are modelled. Material activation studies show that certain threshold reactions yield results of orders of magnitude difference for different neutron source models. The developed plasma neutron source is shown to be applicable to detailed tokamak neutron source effect studies.20192019-06-13 07:45:02Doktorsko delo/naloga108043VisID: 96013COBISS_ID: 3318372sl