On the stabilization of ion temperature gradient modes by finite beta in noncircular toroidal devices

The stability of electromagnetic ion temperature gradient driven (ITG) modes is investigated using an advanced fluid model allowing for arbitrary elongation (κ) and finite beta effects and Shafranov shift. The ITG eigenvalue equation is solved numerically and the stability properties are discussed and compared in both the circular and noncircular geometry. It is found that elongation and finite beta effects reduce the growth rates and that the ITG mode is stabilized for large beta values as elongation is increased. Elongation increases the beta threshold of the ITG mode with larger growth rates as compared with circular geometry.