Dependence of Operation Density on the Density Profile Shape in DEMO Plasmas with Ar Injection for Divertor Heat Load Reduction

Abstract

The feasibility of operation with high plasma density assumed in DEMO conceptual designs is one of the major concerns. Although the operation density would be reduced if peaked density profiles are realized, accumulation of impurity ions injected for divertor heat load reduction may be a problem. We analyzed the argon (Ar) ion transport in the core plasma with various density profile shapes, under the condition of the given fusion power maintained by the feedback control of injection frequency of deuterium-tritium pellets, using the TOTAL code. The ratio of the Ar density to the electron density was fixed at 0.5%, the expected value in JA DEMO, on the plasma surface. For the peaked density profiles, Ar was accumulated in the central region, which caused larger increment in the electron density, but the increment was smaller than the reduction of operation density by peaking the fuel density profile in moderately peaked cases. As a result, the line-averaged electron density and the pedestal electron density were in the feasible ranges reported in the previous experimental study, for moderately peaked density profiles. It was revealed that making the peaked density profiles can improve the feasibility of the DEMO operation density.