Heliac parameter study

Helical axis stellarators (heliacs) with zero net current are found to possess very good stability properties. Helically symmetric or ‘‘straight’’ heliacs with bean-shaped cross sections have a first region of stability that reaches to 〈 β〉 of 30% or more. Those with circular cross sections have a second region of stability to Mercier modes. In addition, the stability properties of these plasma configurations as functions of pressure profile, helical aspect ratio, and helical period length are also reported.