Analysis of the Bohm Criterion for Two-Ion-Species Plasmas Using PARASOL

Abstract

In SOL-divertor plasmas, a condition on the plasma flow velocity, called the Bohm criterion, is required for the formation of a stable sheath in front of a divertor plate. While, for a single-ion species, the usual analytical procedure gives the criterion as a unique solution for the incident ion flow velocity, for two-ion-species plasmas the procedure results in a relation between the ion flow velocities. We carried out full particle simulations with a one-dimensional particle code PARASOL, and clarified in detail the dependence of the condition for two-ion-species plasmas on collisionality and ions mass. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.