Pressure profile shape constancy in L-mode stellarator plasmas

(I) In spite of large vaiety in the profiles of plasma electron temperature and density, theit product, electron pressure presents the feature of profile constancy in stellarator devises in onserved experiments with wide range of the plasma and heating parameters. (II) In the L-mode plasmas of the medium size stellarators, the pressure profiles show remarkable similarities between each other in low (TJ-II, W7-AS) and high (CHS, ATF) magnetic shear configurations. so, the universal profile, characterized by Po-1 dP/dp ∼ const = k, was found for L-mode plasmas and outside the ITB area. The other types of profile like in case of LHD [6] may take place for specific plasma conditions. (III) The obseration of the universal constant k in L-mode (e.g. in the absence of strong ExB effects) may suggests that tubulence and the associated transport reach some kind of saturation level, that does not depend on the absolute values of Te and ne, but alternative explanations (e.g. based on the role of atomic physics and links between magnetic configuration and gradient) can not be excluded. The validation of the transport-based hypothesis would require to characterized the link between local gradients and turbulent transport.