The edge transport barrier (ETB) produced by the L–H transition was measured by a triple Langmuir probe (LP) at two toroidal sections of the compact helical system (CHS), of which diagnostic method has good time and spatial resolutions. The radial profiles of electron density (ne), electron temperature (Te) and space potential (Vs) in the ETB region have different shapes at two different toroidal sections. These profiles are deformed inside the ETB region at one location and are formed with rather smooth variations at the other. These deformations gradually disappear in the deep H-phase (after ∼15 ms from the transition) and the profiles inside the ETB become similar at both sections. The deformation seems linked to the presence of a non-rotating magnetic island at the rational surface of the rotational transform ι/2π = 1.
Flow generation, bifurcation, and transport barrier in CCT