On the different physical mechanisms for accessing hybrid scenarios on JET

摘要

The physical mechanisms for access to hybrid scenarios on JET are analysed by exploiting the role of the poloidal current density profile, which has been identified as critical for the transition to stationary advanced regimes in tokamaks. It is found that the low and high triangularity JET discharges access hybrid regimes via different physical mechanisms, involving the pressure in the core region for the low triangularity case and the pedestal pressure for high triangularity. However, these two regions, apparently different, are linked by a fixed point condition at zero poloidal current, which in the end is related to the particular pressure and q profiles characteristic of these regimes. These features are used, by means of a computational example, to show how to prepare and extrapolate hybrid regimes to other plasma conditions and devices.