Effects of dust particles on the dynamics of blobs in the scrape off layer

A numerical study is presented of the evolution of plasma blobs in the scrape-off layer of a tokamak, in the presence of dust. Appropriate fluid model equations for the nonlinear interchange mode in a dusty plasma are derived, accounting for the attachment of electrons and ions, as well as for their scattering by the dust particulates, and the symmetry breaking between the electron and ion densities due to the dust charging. The dust is shown to introduce three new dissipative mechanisms that determine the blob dynamics, namely the sink of electrons by the attachment to the dust, the sink of the ion momentum by the attachment to, and scattering by, the dust, and the modification of the current outflow to the conductive wall due to the asymmetry between the electron and ion flows to the wall introduced by the dust. A new method for the detection of dust in a scrape-off layer during tokamak discharges is suggested, based on the qualitative difference between the blob dynamics in collisionless and dusty plasmas.