About the choice of material for protecting vacuum chamber of ''Uragan-2 M'' stellarator

One of peculiarities of the stellarator type device ''Uragan-2 M'' (U-2 M) is the possibility for a plasma to be in direct contact with some part of the vacuum chamber wall. This part of the wall surface will play the role of an original limiter and it is required the facing by special materials. As main characteristics for face material selections we use the outgassing rate in vacuum, hydrogen permeability, atomic number and erosion rate. It is desirable to have the latter value at the level (or even lower) which is typical for stainless steel (i.e. 10-2...10-3 at./ion) and the outgassing rate at the level 10-10 Torr · 1/cm2 · s. Comparative analysis of characteristics of several perspective materials and investigation of their outgassing rates showed good prospects to use for U-2 M vacuum chamber protection the materials made on the basis of carbon, silicon and boron carbide using technology of hot-pressing in a vacuum