Plasma operation with high-Z environment

Abstract

High-Z materials appear to be the most realistic choice for reactor plasma facing components (PFCs) because they exhibit the lowest erosion and in the case of tungsten acceptable radiological properties. Results from present day devices and from laboratory experiments confirm the advantages of high-Z materials but also point to operational restrictions when using them as PFCs. They are associated with the central impurity concentration being crucial for central power losses, which is determined by the source, the penetration and the transport of the impurities within the confined plasma. In this respect, the compatibility of ion cyclotron frequency heating (ICRH) in a high-Z PFC environment has still to be proven and a high enough level of anomalous central transport compared to neoclassical transport is necessary to avoid central high-Z accumulation. Remedies are being developed to ameliorate the impact of the restrictions, mainly relying on reducing the source as far as possible and increasing anomalous impurity transport to keep the central high-Z plasma concentrations low. © 2008 IOP Publishing Ltd.