Conceptual Design Studies of an HTS Insert for the DTT Central Solenoid

The “Divertor Tokamak Test” (DTT) facility is an experimental fusion reactor being built in Frascati (IT) in the framework of the European Fusion Roadmap. The DTT Central Solenoid comprises six independently energized modules, wound from Nb3Sn Cable-In-Conduit Conductors (CICC). The future addition of a High Temperature Superconductor (HTS) insert would enhance the CS performance, in terms of magnetic flux density and magnetic field produced in the machine and would represent a fundamental technology demonstration toward high-field fusion. Along with the LTS cables, the Central Solenoid complex aims to reach 18 Wb at the pre-magnetization phase, being 16.54 Wb with the LTS CS only. Each LTS module is internally divided into three sub-modules: High Field (HF), Medium Field (MF) and Low Field (LF), each with a dedicated CICC cable optimized for the intense electromagnetic loads during the plasma scenarios. The LTS cables adopt a 316LN steel jacket and a fiberglass-reinforced resin insulation layer. The conceptual design presented here concerns an HTS insert, to be possibly placed inside the CS bore in the machine, employing a Round-In-Square (RIS) configuration of the conductor with either aluminum alloy or steel jackets. The study carried out for the design of the HTS insert and its pre-compression structure, the main electromagnetic and structural analyses and the design solution are presented in this work.