Model for particle transport in high-density plasmas

The density profiles that have been observed experimentally in magnetically confined plasmas, both in stationary and time-dependent conditions, suggest that they result from the balance of an outward particle diffusion and an inward plasma flux whose rates are higher than those predicted by the collisional transport theory. The outward particle diffusion is considered to be proportional to the effective electron thermal conductivity that has been shown in previous papers to be consistent with existing observations of the electron temperature profiles and the scaling for the electron energy confinement time. The adopted expression for the particle influx is proportional to the anomalous outward diffusion coefficient, and its dependence on the main plasma parameters that has been adopted makes it possible to reproduce both the time evolution and the steady state of the density profiles observed in a relatively large variety of experiments. (author)