In quasi-steady fusion reactors partially ionized boundary layers are likely to be formed. The plasma density is then expected to be peaked close to the boundary. The possibility of large density gradients driving unstable drift modes in these layers is investigated. The expected magnetic shear, due to induced plasma currents in such systems, as well as minimum-average-B properties of the magnetic field, are probably insufficient to significantly influence the stability properties of these modes. However, effects associated with plasma-neutral gas interactions as well as with a finite Larmor radius and ion viscosity modify the behaviour of drift modes and introduce stabilizing effects.
This investigation concerns heating of a plasma being impermeable to neutral gas and situated in a magnetic bottle where the confining field is generated mainly by the current in a supported internal ring. The losses to the ring supports are considered in terms of a single-particle model. The reduction of these losses due to magnetic support shielding is investigated. Further, all transport processes are assumed to be of classical origin, but anomalous effects can be simulated by introducing certain numerical factors. The possibility of local concentration of the induced heating current resulting in a thermal instability is also investigated. Particular interest is focused on the relation between the heat loss to the supports and the threshold condition for this instability. The results of the present investigation have been derived from numerical solutions of a set of nonstationary macroscopic fluid equations.
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