The tokamak database indicates a trend that the electron heat conductivity in H-mode plasmas is less variable than the ion heat conductivity. This can be explained theoretically if we assume that the ion channel is laminarized on magnetic surfaces due to poloidal rotation but that the parallel electron dynamics remains turbulent due to asymmetries along the flux tube. Core H-mode density asymmetry data indicate that a poloidal shock is present with . This type of magnetic configuration leads to persistent anomalous electron heat transport as indicated earlier [1]. The magnetically trapped particle turbulence may be masked due to the existence of the above poloidal asymmetry along the flux tubes. In L-mode these flux tubes further deteriorate confinement due to associated electric braiding which increases the radial correlation scale. An H-mode regime electron heat conductivity formula is given for a flux tube turbulence limited plasma channel. Thus an H-mode factor may be computed for tokamaks relative to popular L-mode scaling laws.
Overview of physics results from the conclusive operation of the National Spherical Torus Experiment