Radial Profile of Plasma Flow Parameters Following Evolution of Electrothermal Polycarbonate Plasma into a Large Chamber Simulating Impurity Expansion in Fusion Reactor Vacuum Vessel

Abstract

The 2-D evolution of the plasma as it expands outside the capillary source, which simulates ablation of plasma-facing materials due to high-heat flux deposition, is of importance to investigate the plasma flow scaling laws with inclusion of radial variations. The flow continues from the source exit through a converging–diverging transition region and expands into a large expansion volume that simulates the vacuum chamber of a tokamak fusion reactor. This 2-D modeling resolves the problem of the 1-D steady state analysis of the plasma bulk flow that assumes the flow parameters to vary only in the axial direction with a uniform radial distribution. As the plasma expands towards the sidewalls of the diverging section in the transition region, the bulk plasma has a finite chance to lose energy primarily in the form of heat loss, which might cause readjustment in the profile for plasma bulk temperature giving rise to a decreasing trend in the radial direction. This change in bulk plasma temperature triggers further changes in other bulk flow parameters along the radial directions, away from the axis of the flow. In this work, different mathematical models have been proposed for radial correction in the bulk flow parameter profiles within the system size as a simulation for expansion into the vacuum vessel of a magnetic fusion reactor. Symmetry of the radial profiles over a cross-sectional area has been assumed to facilitate ease of computation and analysis.