Numerical investigations of linear and nonlinear stages of quasi-interchange instability in a cylindrical tokamak geometry with a flat q-profile in the core region are conducted using eigenvalue and initial value codes, respectively. It is found that there exists a dependent relationship between the central plasma pressure (of the initial pressure profile) and the dominant harmonic of the quasi-interchange instability. As increases, m = n > 1 mode would be dominant in the linear stage and even in the nonlinear stage, where m and n are the poloidal and toroidal mode number, respectively. In addition, with increasing, the fast growth of other harmonics is inevitable and will deeply affect the evolution of dominant quasi-interchange instability.
This paper investigates the relationship between central plasma pressure and the dominant harmonic of the quasi-interchange instability in a tokamak. It finds that as the central pressure increases, higher-order modes become dominant, affecting the evolution of the instability.
Pressure-driven relaxation instability in a current-free high-shear helical system