The Spherical tokamak, a type of fusion power device, had its design simplified into a "compact tokamak" which allowed its toroidal vacuum to be replaced with a cylinder.
A spherical tokamak is a type of fusion power device based on the tokamak principle. One attempt to improve the reactor geometry was attempted by a class of designs known as the "compact tokamak", typified by the Alcator C-Mod (operational since 1991), the Riggatron (conceptual, unbuilt) and IGNITOR (construction in progress as of 2016-02). The later two of these designs dispensed with the first wall and placed the magnets in direct contact with the plasma; in a production design the blanket would be outside the magnets. This greatly simplifies the physical design as well, as the toroidal vacuum vessel can be replaced with a cylinder. 
