Blanket–plasma interaction in tokamaks: Implication from JT-60U, JFT-2M and reactor studies

Optimization of blanket–plasma interaction is one of important subjects of tokamak reactor design. This paper summarizes key physics R&D results of blanket–plasma interactions in tokamak system based on JT-60U, JFT-2M and DEMO studies at JAERI. Conflicting requirement between wall stabilization and disruption tolerance with respect to the electromagnetic coupling between plasma-structure seems to have a solution with somewhat distant wall location while minimization of the distance between plasma and stabilizing wall is critically important for high beta operation. Effect of ferromagnetism on plasma stability is well studied in JFT-2M and theoretically giving positive prospect for use of reduced activation ferritic steel as a first wall material. Enhancement of ion/neutral 1st wall interaction with 2nd SOL and saturated wall is discussed as an important R&D element for DEMO and existence of high-energy neutrals in JT-60U was mentioned.