Evaluation of feasibility and costs of alternative magnetic divertor configurations for DEMO

The European roadmap to the realisation of fusion energy has identified a number of technological and scientific challenges towards the development of a DEMO reactor. Mission 2 'Heat-exhaust systems' includes the investigation of alternative divertor configurations such as the snowflake, X and super-X divertors as a reliable solution for the power exhaust problem. This paper, starting from the geometrical description of a conventional European DEMO scenario with an aspect ratio of 3.1 and a reference Single Null configuration, firstly illustrates the objectives, the figure of merits and the constraints considered in the design of alternative configurations. DEMO descriptions for Double Null, Snowflake, X-divertor and Super-X configurations optimizing the plasma shape, the machine geometry and the PF coil system will be proposed. A comparison of costs and benefits of the various configurations is given, with particular reference to the power exhaust issues.