The DEMO magnet system – Status and future challenges

We present the pre-concept design of European DEMO Magnet System, which has successfully passed plant-level gate review in 2020. The main input parameters originate from so-called 2018 baseline, was produced using PROCESS systems code. It defines a major and minor radius 9.1 m 2.9 m, respectively, an on-axis magnetic field 5.3 T resulting peak on toroidal (TF) conductor 12.0 T. Four variants, all based low-temperature superconductors (LTS), have been designed for 16 TF coils. Two these concepts were selected to be further pursued during Concept Design Phase (CDP): first having many similarities ITER coil concept second being most innovative one, react-and-wind (RW) Nb3Sn technology winding coils layers. variants five Central Solenoid (CS) modules investigated: LTS-only resembling CS hybrid configuration, innermost layers are made high-temperature (HTS), allows either increase flux or reduce outer coil. Issues related fatigue lifetime emerged mechanical analyses will addressed CDP. Both proposed six poloidal lower level risk future development. All magnet studies included thermal-hydraulic analyses, accompanied by experimental tests both LTS HTS prototype samples (i.e. DC AC measurements, stability tests, quench evolution etc.). In addition, structures auxiliary systems, e.g. cryogenics feeders, at level. Important lessons learnt this phase project fed into planning Key aspects concern demonstration validation critical technologies (e.g. industrial manufacturing RW long conductors, insulation penetrations joints), as well detailed overall System structures.