HIDDEN-VARIABLES AFFECTING THE L-H TRANSITION

Recent progress in experimental investigations, related to the determi nant variables of the GH transition, is reviewed in this paper. In par ticular, it is put forward that the 'wall effect', which often produce s spurious contributions to the various parametric dependences of the H-mode threshold power, may be an embodiment of the atomic processes, involving the edge neutrals as a 'hidden' variable. In addition, relat ions between the edge plasma quantities and threshold scaling are emph asized, quoting the ostensibly different observations in various tokam aks.