New design of inter-layer splice joint for the TF coils of the DEMO- EUROfusion tokamak

Abstract

Since the year 2013, the Swiss Plasma Center (SPC) has proposed a Toroidal Field (TF) layout for the DEMO- EUROfusion tokamak, based on a graded winding pack made of layers of Nb3Sn (react-and-wind) conductors. In summer 2015, a new reference baseline is issued for the DEMO- EUROfusion tokamak, leading to an update of the TF coil requirements, e.g. the operating current has been reduced from 80 kA to 63kA. Consequently, the conductor layouts for every graded layer of the TF coil winding pack is re-designed in order to match the new requirements.Each layer of TF coil winding pack has to be connected electrically in series to form the coil. The inter-layer Nb3Sn splice joint design which does not exceed the conductor dimensions is proposed in this paper for the updated 63kA Nb3Sn TF conductor. This proposed joint design allows a continuous winding of TF coil winding pack from layer to layer, housing the joint at the zone of inter-layer transition. Ultimately, the all inter-layer joints should be arranged within the winding pack at the low-field and low mechanically stressed region of D-shaped TF coil.