Measuring Electron Temperature Profiles and Detecting NTMs in ITER Using ECE*

This poster describes the effects of physics issues on interpreting electron cyclotron emission (ECE) diagnostics, and shows how simulated ITER plasma scenarios that are perturbed with magnetic islands can be used to test ECE detection of neoclassical tearing modes (NTMs). These areas of focus help determine the design of the ECE system. ECE diagnostics are planned for ITER as a tool to measure plasma electron temperature with high spatial and temporal resolution, and to detect NTMs. Physical limitations including frequency cut-offs and harmonic overlap can hinder the ability to interpret ECE [1]. In high temperature plasmas, relativistic shift and broadening of the ECE must be considered to accurately reconstruct electron temperature spatial profiles [2]. Accounting for these effects allows ECE diagnostics to be used for accurate measurement of the equilibrium electron temperature profile, and fluctuations about this equilibrium. One such fluctuation is caused by fast radial transport of heat across magnetic islands [3]. ECE diagnostics can detect periodic fluctuations in electron temperature due to rotating magnetic islands to determine the existence and location of NTMs [4]. Fast and accurate detection of NTMs is necessary for avoidance of disruptions.

[1] M. Bornatici, et al, Nucl. Fusion 23 1153 (1983)

[2] M. Bornatici, Plasma Physics 24 629 (1982)

[3] Richard Fitzpatrick, Phys. Plasmas 2, 825-838 (1995)

[4] A. O. Nelson, et al, Fusion Eng. Des. 141, 25–29 (2019)