Particle and energy unloading from a Tokamak using scrape-off limiters combined with helical islands

Following proposals for the scrape-off limiter, the helical divertor and their combination, this paper describes the construction of the vacuum and limiter part of a magnetically shielded scrape-off limiter. The dimensions in the particular construction given are chosen to fit a q = 4 magnetic island suitable for a helical divertor at the TEXTOR boundary. Based on recent experiments and computer simulations the energy flux density striking the limiter is estimated. From this we derive the temperature distribution within the limiter and the permissible power loading. The particle unloading capability is calculated using a Monte Carlo simulation. (author)