Influence of plasma shaping on the parity of core-localized toroidal Alfv\'{e}n eigenmode in an advanced tokamak configuration

TL;DR

This study investigates how plasma shaping influences the parity of core-localized toroidal Alfvén eigenmodes in advanced tokamaks, revealing a transition from odd to even parity with increased circularity.

Contribution

It demonstrates the impact of plasma shaping on TAE/EPM mode parity using a hybrid kinetic-MHD model in an advanced tokamak with reversed shear.

Findings

Dominant TAE/EPM exhibits odd parity with elongated shaping.

Mode parity transitions to even as plasma becomes more circular.

Results explain observed parity differences in various tokamak configurations.

Abstract

Toroidal Alfv\'{e}n eigenmodes (TAEs) and energetic particle modes (EPMs) can both be excited by energetic particles from auxiliary heating and fusion-born alpha particles in a tokamak. Using the hybrid kinetic-MHD model implemented in the NIMROD code, the excitation of these modes and their properties are investigated in an advanced tokamak configuration with reversed magnetic shear in the core region. The dominant TAE/EPM is found to exhibit odd parity with an anti-ballooning structure when the plasma has elongated, non-circular two-dimensional shaping. As the plasma shaping becomes more circular with reduced elongation, the mode parity undergoes a transition to even parity accompanied by a ballooning structure. These results may help explain the dominant parity of TAE/EPMs observed in advanced tokamak configurations with different plasma shaping.