Magnetized sheaths exist at the material walls of fusion devices (divertors, limiters, etc) and determine particle and energy fluxes to the walls influencing the overall operation of the fusion devices. Detail investigations of the helical divertor operation and erosion/deposition at target surfaces in LHD (Large Helical Device; NIFS, Japan) shown that dust particles with size of 3-15 μm were sampling in various regions of LHD. It can be expected a remarkable influence of the dust particles on the magnetized sheaths of LHD due to a continuous selective collection of background electrons and ions by the dust particles. The collection can cause an essential change of both electron and ion energy distribution functions as well as an ion flux in sheaths so that spatial distributions of plasma parameters in sheaths can be essentially changed. Therefore the aim of the work is the computer simulation of magnetized dusty sheaths for conditions close to the LHD edge plasma.
Using PIC/MCC method in the work, a temporal evolution is simulated of one-dimensional slab plasma with given parameters due to a collection of electrons and ions by plane electrode and dust particles immersed into plasma initially. It is assumed that the collisionless slab quasi-neutral plasma is uniform initially and consist of motionless spherical neutral dust particles of given radius and the magnetic field with given initial distributions.
Obtained results show that spatial distributions of plasma parameters in magnetized dusty sheaths can be essentially differed from the distributions in usual sheaths, in particular the distributions indicate a possibility to create in dusty plasmas the double sheaths separated by a quasi-neutral plasma. Spatial distributions of a dust particle charge are non-trivial due to a non-equilibrium of an electron energy distribution function caused by a selective collection of electrons and ions by dust particles and intensive mixing of fast electrons in non-uniform quasi-neutral dusty plasmas. The spatial distributions of a dust particle charge show that charged dust particles can protect walls from an intensive ion sputtering decreasing the ion energy.