An ablation rate model for time-dependent pellet ablation studies at Max-Planck-Institute

The ablation cloud of a pellet injected into a plasma consists of two fairly distinct regions: (1) a cold, dense, weakly ionized core region, whose expansion is spherically symmetric and (2) a warm plasma outer region which forms an elongated channel parallel to B vector. The core region is transonic; The pellet mass ablation rate depends only on the attenuation by the total ∫ ndl in the outer region. The quasi-steady 'fast' core region provides a particle source for the more slowly evolving outer region, described using a time-dependent model under development at IPP-Garching. By joining the two regions a self-consistent ablation model can be constructed for refuelling studies on fusion grade plasmas. (orig.)