HELIAS 5-B magnet system structure and maintenance concept

Work has been continued on the design study of a 5-fold symmetric HELIAS reactor with increased field. The coil shapes were slightly changed from the straightforwardly upscaled W7-X coils to a better suited reactor configuration providing improved plasma confinement and more space for the blanket. This reactor version is now called "HELIAS 5-B". The previously presented building block structure was adapted to the new shapes and forces, and was further optimized for better load distribution and reduced number of joints. Simplified panels with only one or two plates each are now used. In addition to the previously presented option to separate the whole torus for good access to the in-vessel components, a blanket maintenance concept based on exchange of 400 large blanket segments simultaneously through five vertical ports was devised. Even though this concept is still at an initial state it can be shown that also in a complex stellarator geometry it is possible to have robots running on rails inside the plasma vessel to transport heavy loads. (C) 2013 Elsevier B.V. All rights reserved.