Fuel-ion studies in high-performance JET deuterium-tritium experiments – Plasma Strand Project

Supervisors: Marco Cecconello (Durham University), Jacob Ericsson (Uppsala University)

The Joint European Torus (JET) is currently the largest tokamak in the world, as well as the only tokamak capable of operating with a deuterium-tritium (DT) fuel, which is the fuel mix that will be used in future fusion power plants. During the last two years, an extensive set of DT experiments have been carried out at JET. The experiments have explored and developed reactor-relevant operational regimes and resulted in, among other things, a world record in produced fusion energy (59 MJ produced over 5 s).

Many different diagnostics were used to measure various properties of the fusion plasma during these experiments. One important class of diagnostics is the one based on measuring the neutron emission from the plasma. Each DT fusion reaction results in the emission of a neutron, which escapes the confining magnetic field of the tokamak and can thus be measured with non-intrusive instrumentation outside the plasma. Several important properties of the fusion plasma can be determined from neutron measurements, such as the produced fusion power, the D/T density ratio and the plasma temperature. Furthermore, neutron measurements can also contribute to studies of more subtle effects involving the fuel ions, such as their behaviour during various plasma instabilities or during the application of different plasma heating methods.

This PhD project aims to make in-depth analysis of the large amount of neutron measurements available from the recent JET DT experiments. Particular focus will be on analysing data from the Magnetic Proton Recoil (MPR) neutron spectrometer, which is developed and maintained by the neutron diagnostics group at Uppsala University, but also other diagnostics, such as the JET neutron profile monitor, will be included. A large part of the analysis will be devoted to studying how the ions in the plasma respond to the application of various kinds of plasma heating, in particular neutral beam injection and radio-frequency heating. The studies will start from numerical simulations (using state-of-the-art modelling tools such as TRANSP, ASCOT and PION) of what plasma ion distributions that are expected in a given heating scenario. Based on the model, the expected neutron emission, as seen by the relevant diagnostics, can be calculated using dedicated “synthetic diagnostics” codes. The calculated neutron emission can then be compared with the corresponding measurements. If the simulations and measurement disagree, it is a sign that some physical processes are not accurately accounted for in the modelling. It is then possible to use so-called velocity-space tomography methods to infer what the ion distributions should look like in order to obtain agreement with the measured data. This information can then be fed back to the modelling stage and provide clues about what parts of the modelling that needs improvement. This procedure can thus be used to constrain and validate the plasma modelling and, ultimately, provide better understanding of the plasma scenarios of relevance for a future fusion reactor. This PhD project will do this kind of analysis extensively, for a large number of high-performance JET DT discharges.

The project will provide in-depth knowledge of plasma diagnostics, data analysis and plasma modelling. Furthermore, the student will also develop skills in scientific writing and communication, through the publication of results in scientific journals and participation in international conferences.

The project will be mainly based at Durham University but with extended visits to Uppsala University (Sweden).

This project is offered by Durham University. For further information please contact: Marco Cecconello, marco.cecconello@durham.ac.uk

This project may be compatible with part time study, please contact the project supervisors if you are interested in exploring this.