In magnetically confined fusion plasmas, a transport barrier forms when heating exceeds a threshold.
Directly within the separatrix, turbulence and the associated transport are reduced, resulting in steep gradients in density and temperature. As a result, plasma density and temperature increase in the confined plasma, which is of critical importance to achieve economic power generation. This mode of operation of a tokamak is called High Confinement mode (H-mode), in contrast to the operating mode without a without a transport barrier, the so-called Low confinement mode (L-mode). It is assumed that the H-mode is maintained by turbulence suppression by a strong pressure gradient E×B shear flows. The critical heating power to achieve the H-mode is lower when the ∇B drift of the ions points to the active magnetic X-point. If it is directed away from it, the L-H power threshold is higher and another enhanced confinement regime, called the improved L-mode ( I-mode), can be achieved below H-mode power threshold can be achieved.

In particular, our research focuses on the transition from L- to H-mode and the physics of the I-mode.