Divertors with strong re-cycling in the layer near the wall

A narrow divertor layer is considered under the assumption of anomalous (Bohm) coefficients of plasma transport across the magnetic field. It is established that the plasma parameters in such a divertor are affected significantly by the recycling of matter from the wall in the form of neutral atoms and by the anomalous plasma viscosity. Account is taken of the cooling effect of the secondary processes occurring on the collector plates. The system of hydrodynamic equations describing the plasma is solved analytically and numerically, and the plasma density and temperature distributions in the divertor are found. The behavior of impurities sputtered from the first wall is discussed. It is shown that at high specific thermal fluxes to the wall, which are necessary for the economic feasibility of a tokamak reactor, a narrow divertor is capable of maintaining a sufficiently low impurity concentration in the working volume and would enable the unburnt fuel and helium to be removed from the reactor.