Benefits and Challenges of Advanced Divertor Configurations in DEMO

Abstract

The divertor design and configuration define the power exhaust capabilities of DEMO, and act as a major design driver. They set a number of requirements on the tokamak layout, including port sizes, poloidal field coil positions, and size of toroidal field coils. It also requires a corresponding configuration of plasma-facing components (PFCs) and a remote handling scheme to be able to handle the cassettes and associated in-vessel components the configuration requires.There is a risk that the baseline ITER-like single-null (SN) divertor configuration cannot meet the PFC technology limits regarding power exhaust while achieving the target plasma performance requirements of DEMO or a future fusion power plant. Alternative magnetic configurations (AMCs) – for example, double-null, snowflake, and super-X – exist and potentially offer mitigation solutions to these risks and a route to achievable power handling in DEMO. However, these options impose significant changes on machine architecture, increase the machine complexity and affect remote handling and plasma physics and so an integrated approach must be taken to assessing the feasibility of these options.This paper describes work carried out to define a set of design limitations that any alternative divertor configuration for DEMO must consider, and assesses the feasibility of integration of a set of potential AMCs for DEMO.