Characteristics of plasma flow profiles in a super-X-divertor-like configuration

Abstract

Plasma flow patterns in a super-X-divertor-like configuration are investigated by using a one-dimensional plasma fluid model with the anisotropic-ion pressure (AIP model). The AIP model enables to treat supersonic plasma flows self-consistently by describing the parallel plasma momentum transport with a hyperbolic equation keeping the finite effect of the parallel viscosity. A supersonic plasma flow in the diverging-magnetic-field divertor region is generated due to the magnetic nozzle effect. It is found that the sonic-transition point has bifurcation characteristics. A numerical solution from the AIP model agrees well with an analytical one. The Braginskii’s plasma fluid model, on the other hand, creates various unphysical profiles in the supersonic plasma flow region for different boundary conditions of the plasma flow at the sheath entrance. It is also found that a particle source/sink in front of the target brings about generations of subsonic/supersonic plasma flow profiles. Moving the target position, it is found that a discontinuous change in the sonic-transition point and corresponding profile of plasma flow can happen due to the bifurcating characteristics of the sonic-transition point. Keywords: Super-X divertor, Plasma fluid model, Anisotropic ion pressure, Magnetic nozzle effect, Supersonic plasma flows, Bohm criterion