Integrated modeling of DEMO scenarios by the CRONOS suite of codes

The CRONOS suite of codes, which is being developed at CEA-Cadarache and that includes self-consistent kinetic computation of the fusion-born alpha particle distribution, time evolution of the various current sources (bootstrap, rf-driven, NBI-driven) and precise calculation of radiation losses, is used to make a full analysis of the former general scenarios established by EFDA for the design of DEMO. Since high temperatures are expected in these plasmas, electron cyclotron (EC) radiation may be an important cooling mechanism, and therefore a model which takes into account the non-local effects of this radiation, i.e. emission and re-absorption by the plasma itself, has been used. Results show how the expected inductive scenario of DEMO is well simulated, leading to Te0 Ti0 = 50 keV with pedestal temperature Tped ∼ 10 keV. The fusion power obtained is of the order of 4 GW, leading to 1 GW net electrical power. In spite of the fact that in these scenarios the operating density is above Greenwald density, Ne/Ngw = 1.2, and that Bremsstrahlung radiation is enhanced in this regime owing to relativistic effects, EC radiation tends to be the main radiation cooling mechanism for the electrons in the plasma core, even when the optimistic reflection coefficient R=0.8 is used throughout the simulation. Therefore, the inclusion of a satisfactory model for the EC radiation is important for the correct analysis of DEMO scenarios. In fact, a local treatment of EC wave power losses based on Trubnikov formulae, as is generally adopted, does not correctly account for the EC radiation profile, underestimating the re-absorption of the outer part of the plasma, which may even lead to a net energy transfer from the core to the edge. (author)