Effects of trapped particles on distribution of divertor flow in Heliotron-E

The big asymmetry of divertor flows to symmetrically located collectors was observed when divertor plasma flow distributions (DPFD) were measured in Heliotron-E device. Several possible reasons of DPF asymmetry were discussed in previous publications but no one was singled out. In the present work, to clear up the plasma heating effects on DPFD asymmetry, the difference of the DPFDs at plasma heating phase and at an ‘afterglow’ phase of plasma discharge is analyzed for different experimental conditions. During the afterglow phase the plasma is in the regime of Pfirsch–Schlüter diffusion when effects connected with locally trapped particles would be negligible. Besides, the inhomogeneity connected with the locality of plasma heating would disappear and all plasma parameters should be constant along the torus. Therefore, the asymmetry of DPFD observed at this phase of discharge was taken as a base for evaluation of the effects stipulated by the trapped particles.