An advanced pump limiter experiment of large toroidal extent - ALT II

Concepts for an advanced pump limiter experiment able to exhaust 5-10% of the plasma particle flux and remove 200 W/cm2 of heat flux on the limiter face are developed and analyzed. An axisymmetric toroidal belt limiter has a compound curvature blade with edges that extend one particle e-folding distance into the scrape-off layer plasma. Approximately 30% of the plasma efflux flows in a gap between the bottom of the limiter blade and the top of either a structural floor, a plenum box or a liner. Neutralizer/deflector plates are located in discrete pairs at each pumping duct and are designed to optimally scatter neutralized particles into the pump ducts. An alternative design consists of a central toroidal spine beneath the blade which scatters plasma as neutral gas into a plenum box. For application to the TEXTOR tokamak with 1.5 MW of ICRF heating and 2,6 MW of 50 keV neutral beam injection, detailed analysis shows that an average heat flux is approximately 200 W/cm2 and that the localized collector plate design is about five times more efficient than the spinal design for particle removal. (orig.)