The effect of finite sheath conductivity on the interchange instability in the SOL
A linear analysis of magnetohydrodynamic (MHD) instabilities driven by the combined effects of unfavourable curvature and the pressure gradient is performed in the scrape-off layer of a limiter configuration. The dispersion relation of fast growing (electromagnetic) modes is derived by analytical and numerical techniques. The growth rate dependence on the sheath resistivity and the magnetic shear is investigated. Perturbations are not completely stabilized by conducting end walls due to finite sheath conductivity. Modes develop into ideal ballooning modes as the plasma beta increases. Comparison of their behaviour to resistive ballooning modes shows that in most cases of interest the plasma stability is determined by the electromagnetic modes. A new dependence of the instability growth rate on the plasma parameters is found, where the key parameter is the density close to the end plates. Results can be applied to a single-null divertor configuration.
Bibliographic Reference: Report: JET-P(96)43 EN (1996) 18pp.
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon, OX14 3EA (GB)
Record Number: 199611499 / Last updated on: 1997-01-16
Original language: en
Available languages: en