Parameter study of ICRH wave propagation in IShTAR

Abstract

A crude first assessment of how waves behave is commonly made relying on decoupled dispersion equation roots. In the low density, low temperature region behind the last closed flux surface in a tokamak – where the density decays exponentially and where the lower hybrid resonance is crossed but where the thermal velocity is small enough to justify dropping kinetic (hot plasma) effects – the study of the wave behaviour requires the roots of the full cold plasma dispersion equation. The IShTAR (Ion cyclotron Sheath Test ARrangement) device will be adopted in the coming years to shed light on the dynamics of wave–plasma interactions close to radio frequency (RF) launchers and in particular on the impact of the waves on the density and their role in the formation of RF sheaths close to metallic objects. As IShTAR is incapable of mimicking the actual conditions reigning close to launchers in tokamaks; a parameter range needs to be identified for the test stand to permit highlighting of the relevant wave physics. Studying the coupled dispersion equation roots allowed us to find a suitable operation domain for performing experiments.