International audienceAbstract:A key challenge for a future circular collider (FCC) with centre-of-mass energy of 100 TeV and a circumference in the range of 100 km is the development of high-field superconducting accelerator magnets, capable of providing a 16 T dipolar field of accelerator quality in a 50 mm aperture. This paper summarizes the strategy and actions being undertaken in the framework of the FCC 16 T Magnet Technology Program and the Work Package 5 of the EuroCirCol

The reversible axial strain dependence of the critical current of MgB2 conductors is shown to vary with the temperature and magnetic field. The measured critical temperature and irreversibility field are also found to change reversibly with the axial strain. Combining these effects, we show empirically how the strain dependence of the whole critical surface can be scaled with just three parameters: the strain dependences of its three corner points.

The main aim of the EU H2020 project EcoSwing was to demonstrate a technical readiness level of 6–7 for high-temperature superconducting (HTS) technology operating in a wind generator. To reach this goal, a full-scale synchronous HTS generator was successfully designed, built and field-tested in a 3.6 MW turbine. The generator has a rotor with 40 superconducting coils of 1.4 m long. The required >20 km of coated conductor was produced within the project’s time schedule. All coils were tested prior to assembly, with >90% of them behaving as expected. The technical readiness level of HTS coils was thus increased to level 7. Simultaneously, the maturing of cryogenic cooling technology over the last decade was illustrated by the several Gifford-McMahon cold-heads that were installed on-board the rotor and connected with the stationary compressors through a rotating coupling. The cryogenic system outperformed design expectations, enabling stable coil temperatures far below the design temperature of 30 K after only 14 d of cool-down. After ground-based testing at the IWES facility in Bremerhaven, Germany, the generator was installed on an existing turbine in Thyborøn, Denmark. Here, the generator reached the target power range and produced power for over 650 h of grid operation.

Numerous manufacturers and different strand processing techniques are involved with the production of the Nb 3 Sn strand material required for ITER. The superconducting transport properties of brittle Nb 3 Sn layers strongly depend on their strain state. Hence, the thermal compression and the substantial transverse load in combination with the key choice for the cabling pattern of the CICCs, will determine their performance. Knowledge of the influence of axial strain, periodic bending, and contact stress on the critical current ( c ) of the used Nb 3 Sn strands is inevitable to gain sufficient confidence in an economic design and a stable operation of ITER. We have measured the c and -value of Nb 3 Sn strands from various manufacturers in the TARSIS facility, when subjected to spatial periodic bending and contact stress. The c and -values have been determined for applied axial compressive and tensile strain varying from 0.8% up to +0.5%, between = 4 2 K and 10 K and = 6 T to 14 T. The strain sensitivity varies appreciably for different strand types. We present a selection of the results obtained so far.

High temperature superconducting (HTS) technologies are expected to be a key enabler for lightweight and costeffective direct-drive (DD) trains for large wind turbines. This paper reports the designing and basic experimental validation of the world's first full-scale DD HTS generator demonstrated on a commercial wind turbine. The HTS generator has its rotor with an HTS field winding working below 30 K, which is achieved by using off-the-shelf Gifford-McMahon cryocoolers. The stator of the generator is essentially conventional, except that the armature winding has four segments to limit fault torques in case of sudden short circuits due to converter failures. Compared to an existing DD permanent magnet generator on the turbine, the air gap shearing stress of the HTS generator is doubled, and the weight is reduced by 24%. The overall design requirements from the turbine integration perspective, as well as the topological considerations, are first described in this paper. The electromagnetic and cryogenic designs are then presented, followed by performance testing of HTS coils. The basic experimental validation shows that the cryogenic design