Modeling ECE spectra for ITER: assessing the oblique view’s role in resolving ECE/TS discrepancies

Discrepancies between electron temperatures measured by electron cyclotron emission (ECE) and Thomson scattering (TS) diagnostics have been attributed to non-Maxwellian features in the electron velocity distribution function (EVDF), particularly at high temperatures. To address this, the quasi-optical design of the ITER ECE diagnostics includes both radial and oblique views. This work presents simulations using the GENRAY 3D ray-tracing code for an ITER H-mode scenario to evaluate the diagnostic capability of the oblique view at 9.25°. The simulations show that second harmonic X-mode measurements via the oblique view are sensitive to electron energies up to ~50 keV. At higher harmonics, the spectra remain robust even with EVDF distortions, enabling accurate temperature profile reconstruction. Similar behavior is observed for O-mode measurements. Additionally, angle scans demonstrate that Doppler broadening dominating over relativistic effects at oblique angles, enhancing diagnostic reliability. These findings confirm that the current oblique configuration provides effective sensitivity to suprathermal electrons and supports ITER's goal of accurate, non-invasive core temperature measurements.