Stable profiles of plasma pressure in a stellarator

The concept of the ''critical'' plasma pressure profile, which corresponds to the neutral stability, is discussed. An explicit expression for such a profile is obtained in low-β approximation from the Mercier criterion for conventional stellarators. It is shown that for stellarators with a shear, with parameters typical of modern devices (like Heliotron E, Advanced Toroidal Facility, Compact Helical System, and Large Helical Device), stability conditions at low β can be easily satisfied even in the presence of a ''magnetic hill''. (author)