Disruption Research publication in Plasma Physics and Controlled Fusion
Probing linear stability of current profiles for tearing-free scenarios
Neoclassical tearing modes (NTMs) are one of the last remaining physics risks to the tokamak power plant. This is because the main destabilizing drive of NTMs is the pressure gradient, which is generally larger in higher-power tokamaks. The phenomena surrounding NTM formation remains difficult to predict as it lies at the intersection of many physics models spanning single fluid MHD, neoclassical transport, two-fluid dynamics and mode coupling. In a recent publication on Plasma Physics and Controlled Fusion – led by graduate student Stuart Benjamin – we investigated the potential stabilising effect that the current profile can have on NTMs. Monte-Carlo sampling was used to span the space of realistic tokamak current profiles, while the corresponding stability of each profile was quantified through the linear tearing stability parameter \(\Delta'\). In line with prior theory, we observed that a local bump in the current density stabilised the tearing mode, while a local dip in the current density destabilised the mode. However in the absence of these two cases, the tearing drive due to the current is linearly bounded by the local gradient in the current profile, with small enough gradients guaranteed to have a stabilising effect on the mode. These results were then replicated in resistive MHD simulations using the code M3D-C1. While more physics needs to be included to realistically model tearing stability, this paper is but the first in a series of studies attempting to quantify the intersection of NTM-stable operating scenarios with those that are economically viable for a tokamak power-plant.
Enjoy Reading This Article?
Here are some more articles you might like to read next: