Linear interaction and relative role of the ion temperature gradient and trapped electron modes in the reactor-relevant finite beta plasma condition

Focusing on the reactor-relevant plasma condition, where electrons and ions are expected to have a similar temperature profile, an estimate is given on the relative role of the ion temperature gradient (ITG) and trapped electron mode (TEM). A local kinetic code, which takes into account the collisional and electromagnetic effects, is utilized for the linear stability comparison between the two modes. It is shown that, when we limit our consideration to the ion-scale wavelength regime, the TEM, usually driven by the electron temperature gradient, is sub-dominant compared to the ITG in the most parameter regime, including plasma beta. The asymmetric interaction between the ITG and the TEM, in addition to the smaller fraction of trapped electrons and the collisional effect, is found to play a central role in producing this result. When we include the density gradient driven TEM, a strong interaction is also observed, with the mode being rapidly stabilized or transited to the electron temperature gradient driven TEM (ITG) as the electron (ion) temperature gradient increases. Based on these results on the linear interaction and relative role of the ITG and the two types of TEM, a brief discussion is presented on the possible evolution of temperature and density profiles in reactor-relevant conditions. Published by AIP Publishing.