Comparison of energetic particles effects on $m/n=3/2$ and $m/n=2/1$ modes in DIII-D

Experimental tokamak discharges commonly include an evolving $m/n=3/2$ mode before a $2/1$ mode onset, leading to termination of the discharge. The ideal limit of $n=2$ is generally higher than the $n=1$ in $\beta _{N}$, though the $3/2$ mode typically onsets when the rational surface comes into existence off axis in reversed shear, and then evolves in a nonlinear state. All the while energetic particles are affecting both modes differently. Using an experimental equilibrium reconstruction from a hybrid DIII-D discharge with $q_{min}>\sim $1, a linear resistive stability analysis is presented in this stage. The 3-D resistive MHD code NIMROD coupled to a $\delta f$ PIC model for the energetic particles is used to study the kinetic effects of the particles on the \textit{n=1 and n=2} modes. The linear growth is calculated at various $q_{min}$ and $\beta _{N}$ ranging from the resistive unstable to the ideal unstable regime. Results show the interaction of the particles with the non-resonant response on axis causes destabilization of modes as opposed to a damping effect previously reported in the higher $q_{min}$ cases.