ULTRA-LOW ASPECT RATIO STELLARATOR OR HYBRID CONFIGURATIONS

Novel concepts of an ultra-low-aspect-ratio stellarator system, called a Spherical Stellarator (SS), or a stellarator-tokamak hybrid system, called SMARTH (Small Aspect Ratio Toroidal Hybrid) are discussed for high-beta regimes of operation. Self-consistent analysis of the three- dimensional MHD equilibria with inductively driven plasma current or b ootstrap current is presented. It is stressed that the bootstrap curre nt in SS can be large and is flowing in such a direction that the rota tional transform produced enhances the vacuum rotational transform. Th is feature increases the equilibrium beta-limit The high-beta equilibr ia in SS and SMARTH (beta(0) > 30%, beta approximate to 8-9%) are demo nstrated, correspondingly, with the bootstrap current and the ohmic cu rrent. Possible experiments and scalings, including those for reactor parameters, are outlined.