Ballooning Modes Instabilities in Outward LHD Configurations

The aim of this 3D ballooning mode growth rates study is to point out the existence of ballooning activity in outward LHD configurations near the edge, and to find out how these instabilities are triggered in equilibria that simulate plasmas of high density core operations with internal transport barrier. 3D ballooning mode growth rates and Mercier stability were studied for several magnetic configurations with different beta values, and the research reveals an intense activity in outward configurations near the plasma edge, where Mercier criterion predicts stability for interchange modes and experimental data situates the density collapse events [S. Ohdachi et al., Contrib. Plasma Phys. 50, 552 (2010)].