Assessing the Role of the ITER ECE’s Oblique View in Resolving Nonthermal Emissions

Systematic discrepancies between electron temperature Te measurements from radially viewing electron cyclotron emission (ECE) and Thomson scattering diagnostics have been observed in multiple tokamaks and are widely attributed to non-Maxwellian features in the electron velocity distribution function (EVDF). As ITER is expected to operate at much higher core temperatures than present devices, accurate Te measurements from the ECEs become increasingly critical, particularly in the presence of non-Maxwellian EVDFs.This work presents ECE spectra simulations performed to assess the diagnostic capability of the ITER oblique view under ITER conditions where non-Maxwellian distributions are present. The results show that above a critical oblique angle, Doppler broadening becomes the dominant effect, masking fine-scale spectral signatures of nonthermal distortions across a wide range of conditions. Furthermore, at higher electron cyclotron harmonics in either polarization, the spectra remain largely unaffected by nonthermal emissions, enabling the reliable reconstruction of Te profiles.These findings demonstrate that the ITER oblique ECE view retains sufficient sensitivity to nonthermal electrons while providing robust Te profile measurements with reduced sensitivity to nonthermal emission contamination under reactor-relevant conditions. The results presented here also have direct implications for ITER ECE system operation and channel selection, particularly in the presence of non-Maxwellian electron populations.