Joseph Ziegel Final Defense

Abstract: Successful operation of ITER and future magnetic confinement fusion power plants requires control of magnetic instabilities, including neoclassical tearing modes (NTM), that can degrade confinement and lead to disruption. They will rely on low latency NTM detection by an electron cyclotron emission (ECE) diagnostic, which will also provide the primary measurement of electron temperature profiles. This dissertation discusses the design and assessment of the ITER ECE diagnostic. Development of the ECE diagnostic for ITER poses additional physical challenges due to the more extreme operating conditions, particularly the higher plasma temperatures. Relativistic effects become considerable and must be accounted for to accurately assess diagnostic performance and therefore inform design. Additionally, the novel nature of ITER means benchmarking cannot be adequately performed using only contemporary devices. Development of a synthetic diagnostic for performance assessment and ECE prediction is required. This includes testing NTM detection, which requires a model to simulate NTM behavior in ITER plasmas. A novel helical flux displacement model has been developed to perturb ITER simulated plasma scenarios with NTMs, to allow simulated ECE signals associated with NTM development and growth to be tested by the synthetic diagnostic. Detection of the NTM has been demonstrated in real-time in both simulation and hardware tests. Radiometer optimization and smallest detectable island size have been explored, and results have informed the design of the ECE diagnostic prototype. The inclusion of the synthetic ECE diagnostic and NTM modeling into an ITER network compatible workflow has allowed self-consistent end-to-end testing of ITER IMAS database plasma scenarios. From ramp-up to ramp-down, the plasma NTM response and expected ECE is modeled, for scenarios spanning the ITER operational range. Additional concerns and techniques that were encountered and developed as part of the design of the ECE diagnostic are summarized, and the outlook for the ITER ECE diagnostic is discussed.