Optimization of the cooling capacity of the cryo-magnetic system for EU DEMO at the pre-conceptual design phase

Abstract The cryo-magnetic system of the future tokamak EU DEMO includes the superconducting magnets cooled by a forced flow of supercritical helium at about 4.5 K, the cryo-distribution lines and valve boxes, and the cryogenic system with several cold boxes. The DEMO cryogenic system is at the pre-conceptional design phase, with the identification of the heat loads requirements of the main cryogenic users. The analysis will focus on the cooling capacity of the superconducting magnets, with the application on a toroidal field coil conductor based on a CEA design. Simcryogenics, a dynamic modelling tool developed by CEA, has been used to model a supercritical helium loop for cooling one conductor pancake. An algorithm has been developed to optimize the cold source temperature and the supercritical helium mass flow, in order to minimize the refrigeration power. At this pre-conceptional design phase, the interest of such analysis is to contribute to the optimization of both the cryogenic system and the superconducting magnets to minimize the refrigeration power, one of the important investment and operation costs for the future tokamak.