Advances in fusion reactors -- Science in TPX

Advanced reactor studies like the ARIES series of designs have identified ways in which physics performance advances can improve the outlook and cost of fusion reactors. Supercode studies have quantified the cost reductions that various parameter improvements can make in reactors. High bootstrap fraction operation makes steady state operation significantly more efficient. Heat dispersal in divertors has been demonstrated in DIII-D by gas puffing (hydrogenic or impurities). And, enhanced performance in DIII-D, as measured by higher normalized beta (βN) and confinement enhancement (H-factor), has been achieved by controlling plasma profiles. These physics ingredients are combined in the Tokamak Physics Experiment (TPX) design for the purpose of exploring physics issues that will lead to more compact, economical reactors that operate continuously. TPX is designed for long-pulse (1,000 sec) operation in its initial phase, and the tokamak itself is designed to be inherently steady state. By operating in modes like the reversed shear mode (the PEP mode in JET, and the 2nd stable core mode in DIII-D) the author expects to demonstrate steady state operation at performance levels characterized by H up to 4 and βN up to 5. This paper describes the physics features of TPX, with emphasis on the control and physics integration features that lead to the expectation of advanced performance in the device