Effect of central plasma pressure on high-order harmonics of 1/1 quasi-interchange instability in a central weak magnetic shear tokamak configuration

Abstract 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mi>p</mml:mi> <mml:mn>0</mml:mn> </mml:msub> </mml:mrow> </mml:mrow> </mml:math> (of the initial pressure profile) and the dominant harmonic of the quasi-interchange instability. As <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mi>p</mml:mi> <mml:mn>0</mml:mn> </mml:msub> </mml:mrow> </mml:mrow> </mml:math> increases, m = n &gt; 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mi>p</mml:mi> <mml:mn>0</mml:mn> </mml:msub> </mml:mrow> </mml:mrow> </mml:math> increasing, the fast growth of other harmonics is inevitable and will deeply affect the evolution of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>m</mml:mi> <mml:mo>=</mml:mo> <mml:mi>n</mml:mi> </mml:mrow> </mml:math> dominant quasi-interchange instability.