Vacuum chamber wall erosion by unipolar arcs in stellarators

Results of comparison of topography peculiarities of magnetic field and character of chamber wall damage by unipolar arcs are presented using as examples ''Sirius'' and ''Uragan-2'' stellarator. Microphotographies of chamber wall surface in erosion places and data on the number of metal impurity atoms, falling on the wall, are given. On the basis of the data presented the following conclusions can be made: 1) region and area of vacuum chamber wall damage by unipolar arcs in the stellarator to a considerable degree are determined by magnetic field topography; 2) the trace of unipolar arc presents a sequence of overlapping craters; 3) successive arc formation on heterogeneities of wall surface car result in a considerable local ejection of its material mass; 4) entrance of metal impurities to plasma at the expense of the chamber surface erosion by unipolar arcs can be considerably decreased in the modification of stellarator system of torsatron type with a divertor