Simulation of burn control for DEMO using ASTRA coupled with Simulink

DEMO is a proposed demonstration fusion power plant which is currently being designed. Fusion power, P-fus, has to be controlled to stay above a minimum level to produce sufficient net electricity. However, this has an impact on the power through the separatrix, P-sep, and thus can produce excessive heat flux to the divertor which can lead to damage. This gives a limit for the maximum allowable P-sep. The aim of this work is to develop a framework which will give the possibility to design and to test controllers by simulating DEMO plasma transport. Therefore, we coupled the ASTRA transport modelling code for fusion devices with the Simulink simulation framework. ASTRA is equipped with equilibrium, transport, fuelling, heating and current drive modules. Simulink is a powerful tool to model and to simulate different dynamic systems. It allows fast and simple development of controllers using its built-in blocks. Therefore, coupling of ASTRA with Simulink gives the advantage of fast development of controllers for the power plant modelled with sophisticated physics based on the transport codes. This coupling was used to run the first basic simulations, where we simulated feedback control of fusion power, power through separatrix and pedestal top Greenwald density fraction, n(GW)(ped) (top). n(GW)(ped) (top) is controlled via the pellet frequency to keep it below one. Fusion power is controlled with external heating (NBI). To prevent increasing P-sep and heat load on the divertor while increasing P-fus, xenon gas can be puffed into the vessel. However, P-sep has to be kept above a threshold to stay in H-mode. Therefore, feedback control of the xenon gas puff is modelled. These controllers were used to control fusion power, power through separatrix and pedestal top Greenwald density fraction with two different external disturbances. In the first one, we mimicked changes of the H-factor and in the second one we mimicked the fall of a tungsten flake. Results show that we can control these parameters already with a combination of simple controllers. (C) 2017 The Author(s). Published by Elsevier B.V.