Three types of pressure crash in the low magnetic shear tokamaks

Numerical investigations on the pressure crash with a low magnetic shear profile in Tokamaks are carried out through the three-dimensional, toroidal, and nonlinear MHD code CLT. We find that there exist at least three different kinds of pressure crashes. The first type is that one cold bubble forms and merges into the hot core, which is the standard case for the nonlinear evolution of the quasi-interchange mode. The second type is two cold bubbles forming and squeezing the hot core, leading to fast pressure crashes. The third one is similar to that caused by the resistive-kink mode, i.e., an m/n = 1/1 magnetic island grows up and fills up the whole central region. The thresholds for these kinds of pressure crashes are systematically discussed. Published under an exclusive license by AIP Publishing.

Automated summary

Numerical investigations have been conducted on pressure crashes with a low magnetic shear profile in Tokamaks using a three-dimensional, toroidal, and nonlinear MHD code CLT. Three different types of pressure crashes have been identified, including the formation and merging of cold bubbles into the hot core, the formation of two cold bubbles squeezing the hot core, and the growth of a magnetic island filling up the central region. The thresholds for these pressure crashes are systematically discussed.