Two states of periferal plasma in tokamaks

A new effect, being called MARFE (Multifaceted Asymmetric Radiation from the Edge), is discovered in some large tokamaks. It consists in occurring in near-the-wall region poloidal asymmetric plasma formations with high density and low temperature, which are the source of strong radiation of neutral hydrogen and light impurities. It has been supposed that one of the reasons for MARFE formation can be the development of peripheral plasma instability in a tokamak, leading to transition into the state with strong re-cycling of plasma on the surfaces restricting it - diaphragms, divertor plates, regions of the first wall contact. The model, explaining the experimental data, which give evidence that impurity introduction decreases the average plasma density, being a threshold for MARFE occurrence, is considered. The possible connection between the states with various degree of re-cycling under H- and L-modes of plasma confinement in divertor configurations is considered