Description
In this work, we revisit an ITER pre-fusion-power-operation plasma scenario (PFPO-2, IMAS shot 101006) with half-field and half-current conditions (7.5~MA). A multiscale analysis was previously reported in [{\it T. Hayward-Schneider et al., Nuclear Fusion, 62, 112007, 2022}]. Weakly damped toroidal and elliptical Alfv\'en eigenmodes were observed for moderately low toroidal mode numbers ($10 < n < 35$). At higher mode numbers ($40 < n < 70$), unstable Alfv\'enic modes are found near rational surfaces and are identified as beta-induced Alfv\'en eigenmodes (BAEs) or Alfv\'enic ion temperature gradient modes. At even higher toroidal mode numbers ($n \simeq 200$), low-frequency microscale instabilities emerged, but they were only briefly discussed in that work. Here, we conduct a detailed investigation of these microinstabilities using different electron models within the gyrokinetic code \textsc{ORB5}. Our results show that in the outer plasma region, the dominant instability is a Trapped Electron Mode (TEM), while near the plasma center ($r/a < 0.5$), the dominant mode is the Ion Temperature Gradient (ITG) instability. Furthermore, we highlight the critical role of the ion-to-electron mass ratio in drift-kinetic electron simulations.