High-β Disruption in Tokamaks

Three-dimensional magnetohydrodynamic simulations of high-{β} plasmas show that toroidally localized high- n ballooning modes can be driven unstable by the local pressure steepening that arises from the evolution of low- n modes. Nonlinearly, the high- n mode becomes even more localized and produces a strong local pressure bulge that destroys the flux surfaces resulting in a thermal quench. The flux surfaces then recover temporarily but now contain large magnetic islands. This scenario is supported by experimental data.