Development of an imaging neutral particle analyzer for MAST Upgrade (plasma strand project)

Supervisor/s – M. Cecconello (Durham University)

In fusion plasmas, fast ions have energies much higher than the thermal plasma background. Fast ions are generated by external auxiliary heating such as Neutral Beam Injection (NBI) and Ion Cyclotron Resonance Heating (ICRH) or by the fusion reactions themselves. In the former cases, fast ions are hydrogen isotopes with energies in the range from tens of keVs up to a few MeVs. Fusion reactions produce, in addition to hydrogen isotopes, alpha particles with energies in the MeV range.

Fast ions play an important role in heating the plasma, maintaining the high temperatures necessary to sustain the fusion reactions and crucial in achieving a burning plasma. NBI heating is also important for current drive, that is for long pulse operation of tokamaks beyond the inductive regime and therefore for the realization of a fusion reactor.

Confining fast ions in the plasma for time long enough so that they can transfer their energy to the background plasma is therefore crucial for achieving the goal of a power plant based on thermonuclear fusion reactions. However, fast ion confinement is degraded by plasma instabilities some of which are triggered by the fast ion themselves. In this case, energy exchange between the fast ions and the instabilities result in the redistribution and loss of fast ions, ultimately reducing the performances of fusion reactors. Furthermore, the loss of fast ions in the plasma can result in the damage of the reactor first wall, an issue particularly for the very energetic alpha particles that will be produced in ITER and DEMO.

MAST Upgrade unique capabilities provide the opportunity to study the interplay between fast ions and plasma instabilities in a wide range of plasma scenarios that are not achievable in other present day conventional tokamaks. The combination of broader NBI power deposition profiles and low magnetic field allows the study of the behavior and confinement properties of super-Alfvénic fast ions. MAST Upgrade is equipped with a wide range of diagnostics dedicated to the study of lost fast ions (a fast ion loss detector, a fast ion D-alpha monitor) and of confined fast ions (a collimated neutron flux monitor array, a fast ion D-alpha monitor and a compact neutral particle analyzer).

The aim of this project is to design, develop, construct, install and commission an Imaging Neutral Particle Analyzer diagnostic for MAST Upgrade. The INPA combines the advantages of the compact NPAS and FIDA to measure confined fast ion phase space with its excellent energy, spatial and temporal resolution. Combined, these diagnostic will provide the most exhaustive description of fast ion confinement in spherical tokamak to date and will enable the benchmarking and development of the simulations codes that are used to design fusion reactor operating scenarios extrapolating from present day devices. This project involves both modelling and experimental work and will be based at Durham University. The later phases of the project will require on -site presence at MAST Upgrade (CCFE) and will be concluded with first experimental observations. International travel and participation to international conference and workshops are foreseen.

The project will be mainly based at Durham with long stays at CCFE.

This project is offered by Durham University. For further information please contact: M. Cecconello (marco.cecconello@physics.uu.se)

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