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The upgraded magnet assembly of the EDIPO test facility aims at generating 15 T at 4.2 K and 85% of short sample limit in a large rectangular aperture and over a uniform field length of 1000 mm. During 2020 the design studies have concentrated on two flared-end block-coil design options with four double-pancake coils, two per pole. The coils are planned to be produced using Nb3Sn Rutherford cable with 44 × 1.1 mm diameter strands, which results in significantly larger dimensions compared to the typical cables used in accelerator magnets. Two sections of dummy superconducting cable have been produced, and dedicated tooling was developed to study the wind-ability of such high aspect ratio cable and provide input to define the geometrical parameters of the coil flared ends. This paper describes two magnet designs proposed for EDIPO focusing on the magnetic and the mechanical design. [ABSTRACT FROM AUTHOR]

The EUROfusion DEMO machine is at its pre-conceptual stage. The design of the magnet system for this machine is being developed in collaboration with several European research centers. The Poloidal Field (PF) coils proposed by the Swiss Plasma Center (SPC) use a multiple-in-hand Pancake winding technique. A design based on updated plasma scenarios (2018) was recently proposed. The Winding Pack (WP) aspect ratio was kept close to one, similar to the baseline design in the EUROfusion 2018 DEMO baseline document. In this publication, we study the effects of changing WP aspect ratio. A vertically elongated WP cross-section is beneficial in the reduction of the peak magnetic field at WP cross-section, the machine radial extent, and the hydraulic lengths. However, it increases the bending stress on the WP. An updated PF design is presented. The dimensioning and allocation of materials is based on 3-dimensional electromagnetic calculations. Mechanical performance is evaluated against both dynamic fatigue stress and static stresses. The static stresses are evaluated through 3-dimensional finite element simulations to take into account also the ripple effect of TF coils and increase in bending stresses due to the elongation of the WP cross-section. The thermal-hydraulic analysis verifies a temperature margin of 1.5 K and confirms sufficient coolant flow for the prescribed pressure drop. The quench analysis determines the hot-spot temperatures during various quench scenarios. [ABSTRACT FROM AUTHOR]

Future high-field accelerator magnets foresee the extensive use of Nb3Sn, more expensive than the Nb-Ti of LHC. For projects involving the series production of magnets, conductor grading is mandatory in order to reduce the cost. To allow grading, a splice between higher and lower grade cables must be implemented. The internal splice option, i.e., embedded in the winding pack, is the one considered in this manuscript. The magnet technology is Wind&React (W&R). The target resistance is 1 nΩ at a background field of B≈10 T and ratio between operational and critical current I/Ic≈1/3, the one at which such Nb3Sn dipoles are expected to work. This manuscript reports progress on ultrasonically welded, soldered and diffusion-bonded splices. The feasibility studies on ultrasonic welding between Nb3Sn Rutherford cables and strands is presented. The potential corrosive effect of fluxing agents of impregnated soldered samples is examined. In the end, the design and test in SULTAN of bent diffusion-bonded splices is reported. [ABSTRACT FROM AUTHOR]

Previous studies indicated that the use of hightemperature superconductors (HTS) in the highest field allows us achieving the required magnetic flux in the central solenoid (CS) of the European DEMO at a reduced outer diameter, which would enable a reduced overall size and cost of DEMO. The proposed winding pack design of the CS1 module is based on ten layerwound subcoils using an HTS, react and wind Nb3 Sn, and NbTi conductors in the high, medium, and low field sections, respectively. The design utilizes a stainless steel and a superconductor grading leading to different overall current densities in each of the ten subcoils. Both, the hoop stress and the vertical loads are taken into consideration for determination of the required stainless steel cross-section in the winding pack. The stainless steel grading has been found to have an even more pronounced effect on the overall subcoil current densities than the superconductor grading. A preliminary estimation of the space required for the precompression structure is also reported. [ABSTRACT FROM AUTHOR]

The ITER magnet system contains 18 toroidal field (TF) coils and each TF winding pack is enclosed in a stainless steel coil case. During operation, the coil case will be subjected to eddy current and nuclear heating, in addition to the static heat loads (thermal conduction and radiation). In order to minimize the heat transfer to the superconducting winding pack, the coil case is cooled by a flow of helium at 4.5 K circulating through an array of cooling pipes. In the baseline design, the thermal contact between the cooling pipes and the coil case is made by a resin bond. A series of samples has been prepared reproducing the geometry of the grooves where the cooling pipes are embedded. The samples explore the baseline design as well as an alternative design based on the contact between metallic surfaces. The effective thermal conductivity has been measured in the SULTAN facility by circulating a constant flow of helium at 4.5 K and applying a steady state heat load. The measurements show no indication of cracks or delamination decreasing significantly the overall heat conductivity of the samples after cool-down, even after a four-point bending process representative of the assembly process. [ABSTRACT FROM AUTHOR]

The React&Wind (RW) method for the large Nb3Sn magnets of theEUROfusionDEMOdevice was proposed in 2013 by the Swiss Plasma Center. A first short-length prototype conductor for the toroidal field (TF) coils, named RW1, was tested in the EDIPO test facility during 2015-2016 up to 82 kA at 13 T, with an effective strain matching the expected thermal strain of ≈ -0.30%. After the baseline of the DEMO device was updated in 2015, the new requirements led to an updated conductor design, for 63 kA at 12.2 T. Themanufacturing experience of the first prototype, named RW1, is exploited in a second short-length prototype conductor, named RW2, assembled and tested in 2017: The conductor aspect ratio is reduced, and the segregated copper wires are replaced by a solid block of mixedmatrix stabilizer. Although designed for theTF coils, with dc operation, the moderate ac loss of the flat cable makes the RW2 a good candidate also for the central solenoid conductor. The Nb3Sn strand for RW2 is supplied by WST (PRC), and the flat cable is made at TRATOS (Italy). The rationale of the design, the conductor manufacture, the sample assembly, and the test results in SULTAN are reported. [ABSTRACT FROM AUTHOR]