Pump limiters

The pump limiter is discussed as a device to remove particles from a tokamak. To this purpose, different pump limiter types have been developed. The removal of hydrogen from the TEXTOR tokamak with the ALT I pump limiter and related problems are discussed. It has been observed that the choice of the limiter material (graphite or TiC coated graphite) changes the performance. In tokamaks with pulse lengths of several seconds and even more in future experiments, the removal of particles is an important process, because by controlling particle inlet and removal the plasma density is regulated, and in fusion reactors the helium ash will have to be removed. Pump limiters are also called mechanical divertors. The basic idea was to combine a limiter-mushroom limiter or toroidal band limiter- with a strong pump, e.g. a titanium getter pump at the lateral wall, in order to remove part of the recycling gas at the limiter