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In the scope of the Future Circular electron positron Collider study (FCC-ee), the IDEA detector is developed. It comprises a superconducting solenoid with free bore of 4 m, 6 m long and a central magnetic field of 2 T. The positioning of the magnet between the inner tracker and the electronic calorimeter heavily constrains the magnet design, as it is required to have the lowest possible radiation length, so minimum thickness and lowest density material. With respect to the classical solution of a solenoid enclosing the calorimeters, a cost reduction of about 50% is expected due to size reduction. An optimization of the different components of the magnet system has been carried out, resulting in the development of a new composite high-strength conductor that can be used to build a 30 mm thin solenoid. The quench analysis of the solenoid will be presented as it is of critical importance given the high energy density in the magnet of 21 kJ/kg. A cryostat made of concentric aluminium shells would account for about 50% of the radiation length of the magnet and most of this material is used in the outer vacuum shell of the cryostat to prevent buckling. In order to further reduce the radiation length, two fundamentally different approaches are being analysed. The first method focuses on reducing drastically the outer shell thickness. This leads to use honeycomb composites, reinforcing bars and corrugated shells for the outer shell of the cryostat. The second approach consists of supporting very thin cryostat shells directly on the solenoid cold mass using proper support. This can be achieved by replacing the thick walls and MLI insulation by a material that can sustain 1 atm while having low radiation length and low thermal conductivity. Cryogel Z has shown promising properties and its suitability for this project is being analysed. This novel approach has never been used so far for superconducting magnets. [ABSTRACT FROM AUTHOR]

High temperature superconducting (HTS) generators could enable a lightweight and cost-effective direct drive (DD) wind turbines with large power ratings. The EU-funded EcoSwing project successfully demonstrated the world's first full-scale MW-class HTS generator on a commercial DD wind turbine. This paper focuses on the commissioning of the EcoSwing HTS generator on the wind turbine. The commissioning campaigns, including the rotor cool-down, excitation of the HTS field winding, and the power production of the generator, are presented in the paper. In the testing period, the generator was grid-connected for more than 650 hours and accumulatively produced more than 600 MWh to the grid. The target output power of the 3 MW class was reached. Throughout the real-life testing on the wind turbine, the generator performed well from the electromagnetic, thermal, and mechanical perspectives. Moreover, the generator even sustained three sudden short circuits in the converter system. The work reported has shown that HTS generators are technologically feasible for wind turbine applications, and the technology readiness level of HTS wind turbine generators has been improved to 6 $\sim$ 7 for the first time. [ABSTRACT FROM AUTHOR]

The EU-funded EcoSwing project addresses the world's first full-scale direct-drive (DD) high temperature superconducting (HTS) wind turbine generator. Before the generator was installed on a commercial wind turbine, the generator had been tested on the ground at the Dynamic Nacelle Testing Laboratory (DyNaLab) in Fraunhofer Institute for Wind Energy Systems (IWES), serving as an experimental validation of the generator design. This article is centered on the ground testing of the EcoSwing HTS generator, which includes corresponding tests for validating the generator's cryogenic design and electromagnetic performance. Despite one HTS coil with a defect limiting the operating current significantly, partial power production up to 1 MW at 14.5 rpm was reached. The critical auxiliary systems, i.e., vacuum system and rotary helium coupling, behaved as expected or even better than anticipated. The work reported in the article successfully validates the generator design, and also provides firsthand information prior to installing and testing the HTS generator on the wind turbine. [ABSTRACT FROM AUTHOR]

MgB2 wires and tapes were prepared by the powder in tube method using different processing technologies and thoroughly characterized for their superconducting properties. Either prereacted MgB2 (ex situ) or a mixture of Mg+2B (in situ) was used as the precursor powder. In some wires the precursor powder was mixed with SiC. The critical current density (Jc) of these wires was found to differ by orders of magnitude, the highest Jc being 104 A cm-2 at 10.5 T and 4.2 K. The microstructure of these wires was investigated using quantitative electron microscopy and spectroscopy methods [B. Birajdar, N. Peranio, and O. Eibl, Supercond. Sci. Technol. 21, 073001 (2008)]: combined scanning electron microscopy, electron probe microanalysis, and transmission electron microscopy analysis with artifact-free sample preparation, elemental mapping, and advanced chemical quantification. Wires with prereacted MgB2 (ex situ) show oxygen-poor MgB2 colonies (a colony is a dense arrangement of several MgB2 grains) embedded in a porous oxygen-rich matrix introducing structural granularity. Wires with elemental precursors (in situ) are generally more dense but show inhibited MgB2 phase formation with significantly higher fraction of B-rich secondary phases in comparison to the ex situ wires. SiC in the in situ wires results in the formation of Mg2Si secondary phases. In situ and mechanically alloyed samples show smaller (20–100 nm) MgB2 grains, the grain size being slightly larger than the coherence length. All samples show Mg oxide. SiC added samples annealed beyond 950 °C yield formation of Si oxide compounds, whereas Mg2Si is found for annealing temperatures of less than 650 °C. The critical current is limited due to the anisotropy but also due to structural granularity. A microstructure–critical current density model is given to explain the large, orders of magnitude, differences in the Jc of MgB2 wires and tapes. The model contains the following microstructure parameters: (1) MgB2 grain size, (2) colony size, (3) volume fraction of B-rich secondary phases, and (4) oxygen mole fraction. The logarithmic critical current densities as a function of magnetic field were parametrized and the decay field and the critical current density at zero field (Jc0) was quantitatively correlated with the parameters of the microstructure. The MgB2 grain size is negatively correlated with the decay field and the three other microstructure parameters show correlation with Jc0. Sample preparation influencing the microstructure parameters is discussed. A detailed analysis is given to correlate the microstructural data with respect to fundamental parameters of a flux-line pinning model established for anisotropic superconductors. [ABSTRACT FROM AUTHOR]

High temperature superconducting (HTS) technologies are expected to be a key enabler for lightweight and cost-effective 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 is satisfactory and the measured no-load voltage matches the finite element calculation very well. [ABSTRACT FROM AUTHOR]

A next step of energy increase of hadron colliders beyond the LHC requires high-field superconducting magnets capable of providing a dipolar field in the range of 16 T in a 50-mm aperture with accelerator quality. These characteristics could meet the requirements for an upgrade of the LHC to twice the present beam energy or for a 100-TeV center of mass energy future circular collider. This paper summarizes the activities and plans for the development of these magnets, in particular within the 16 T Magnet Technology Program, the WP5 of the EuroCirCol, and the U.S. Magnet Development Program. [ABSTRACT FROM AUTHOR]

Properties of BSSCO/Ag tapes transporting AC current were studied by the Fourier analysis of the accompanying voltage signal. Particularly, the electrical signal in the measurement loop that is used in the standard AC loss measurement has been investigated. BSSCO/Ag tapes were studied starting from the characterization of the filament configuration, Jc(B) dependence and inhomogeneity of Jc distribution. These data were used as the input parameters for the numerical simulations. Initial simulations showed the necessity of replacing the simplified geometry model with detailed mutlifilamentary structure. Consequently, the higher harmonics turned out to be extremely sensitive on characterization parameters. After such refinement, the results of simulations give good agreement with measured higher harmonics of the voltage signal. This means that the analysis of higher harmonics could provide relevant information about the structure and other basic properties of the measured tape. [ABSTRACT FROM AUTHOR]

We report on the preparation of dense monofilamentary MgB[sub 2]/Ni and MgB[sub 2]/Fe tapes with high critical current densities. In annealed MgB[sub 2]/Ni tapes, we obtained transport critical current densities as high as 2.3×10[sup 5] A/cm[sup 2] at 4.2 K and 1.5 T, and for MgB[sub 2]/Fe tapes 10[sup 4] A/cm[sup 2] at 4.2 K and 6.5 T. An extrapolation to zero field of the MgB[sub 2]/Fe data gives a critical current value of ∼1 MA/cm[sup 2], corresponding to a critical current value well above 1000 A. The high j[sub c] values obtained after annealing are a consequence of sintering densification and grain reconnection. Fe does not react with MgB[sub 2] and is thus an excellent sheath material candidate for tapes with self-field j[sub c] values at 4.2 K in excess of 1 MA/cm[sup 2]. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]