CEA-Saclay started the development of Metal-as-Insulation racetrack coils in as part of the High Field Magnet (HFM) CERN program. This winding method aims to significantly reduce the amount of High Temperature Superconductor material required to achieve relatively high magnetic induction and associated forces. CEA's objectives are to fabricate and test a small racetrack coil to benchmark numerical models with experimental data. The insulated coil counterpart, operating at lower current densities and targeting high fields, is studied by CERN as part of the HFM program. This paper focuses on the design, fabrication and quench tests at 4.2 K of two specific coils: a single racetrack coil and a double racetrack coil (DRT), each with 140 mm long straight part and 27 mm inner diameter. Both coils achieved very high overall current density (above 2300 A/mm(2)) and significant peak magnetic field on the conductor (8.5 T and 12.3 T respectively). A central magnetic field above 5 T was reached after a quench at 4.3 T in the DRT.

One of the goals of the High Field Magnet (HFM) Program at CERN is to explore High-Temperature Superconducting (HTS) magnet technology for accelerator applications that go beyond the limits of low-temperature superconductors such as Nb3Sn. This offers a pathway for the development of higher energy and more sustainable particle accelerators operating at temperatures above 1.9 K or even 4.5 K. As a stepping-stone to achieve these goals, CERN has launched the development of model coils in racetrack geometry that can be scaled up for use in common coil-type magnets. The model coils were used to validate winding tooling, a newly developed cable insulation application method, instrumentation placement, conductor performance, and other key design choices with a short iteration cycle that allows for rapid development. We detail the coil electromagnetic design, and several lessons learned during the progression from single-layer to double-layer coils with an internal layer jump that allows for a modular magnet design approach. Additionally, the results from liquid nitrogen tests and preliminary findings from liquid helium testing are discussed.

SHiP experiment, to be located at CERN in the ECN3 North Area cavern, aims at detecting feebly interacting particles, potentially shedding light on neutrino mass and dark matter. A key component of the detector is the Hidden Sector Spectrometer, potentially the first large-scale, energy-efficient experimental magnet relying on superconducting MgB2 cables. This technology, initially developed for the High Luminosity upgrade of the Large Hadron Collider (HL-LHC) at CERN, has been adapted for electromagnets, cooled by gaseous helium (GHe) at about 20 K. We present the current status of the proof-of-principle demonstrator, which features a coil from MgB2 cable wound onto an aluminum former and mounted inside a low-carbon steel yoke. The demonstrator has been successfully tested in GHe at 20 K. In the next development, the demonstrator will be upgraded to test indirect cooling of the MgB2 cables, while the yoke will remain at ambient temperature. This work represents a validation step toward the design of the spectrometer magnet for SHiP, with a focus on achieving good homogeneity at a magnetic integrated field of 0.65 T.m over a large aperture of 4m x 6m. The conceptual design of the magnet is outlined, along with the production challenges.

The decreasing cost and expanding production of REBCO tapes make them promising candidates for accelerator magnets operating at high current density and high magnetic field. Within the CHART program supporting accelerator-magnet development, we perform electromagnetic and thermal analyses of the first REBCO subscale (RS1) magnet developed in the MagDev Lab at PSI, designed to enable direct experimental comparison between HTS and LTS technologies. The RS1 magnet adopts the same configuration as a previously tested LTS SMCC common-coil magnet, in which the Nb3Sn cable is replaced by a straight, soldered REBCO tape-stack cable with comparable geometric parameters. The magnet comprises four racetrack winding layers, with two layers located on each side of the aperture.We present models of resistive and AC-loss induced heating in the REBCO stack under operating conditions relevant to superconducting magnets: liquid helium (4.5 K), gaseous helium (20 K), and liquid nitrogen (77 K). Magnetic-field harmonics and transient behavior in the REBCO cables are computed using an H–A formulation in FEM. The analysis further includes predictions for REBCO magnet protection using a dump resistor as well as alternative protection strategies. Numerical results are compared with experimental data from the two-layer configuration and the full magnet tested in liquid nitrogen, and predictions are provided for liquid- and gaseous-helium tests upcoming at CERN in 2026. These results support the development of accelerator magnets at higher magnetic fields where REBCO conductors offer significant potential.

In this paper we report on a novel HTS coated conductor developed at the KIT-CERN Collaboration on Coated Conductors (KC4) facility at the Institute of Technical Physics (ITEP), Karlsruhe Institute of Technology (KIT), Germany, namely the first-ever 30 mm wide coated conductor on IBAD-MgO, which was provided by iBeam Materials. These samples are highly homogenous with self-field Jc values at 77 K and 30 K of 1.0 MA/cm2 and 6.6 MA/cm2 respectively. We will briefly introduce the KC4 facility, which is a pilot production coated conductor R&D laboratory, established for material development to bridge the gap between research and manufacturing and to transfer small-scale PLD research results to large-scale coated conductors (CCs). Since the completion of the deposition line in 2023, REBCO films have been deposited on long-length metal substrates with various buffer stacks, and reasonably good Ic values of 300 A/cm width at 77 K on 12 mm wide tapes were obtained with the potential for further improvement. Efforts are in progress to upscale the R&D to wider tapes that will open new avenues for the application of CCs in the high-field, low temperature region as well as for special applications.

The inner triplet (or low-beta) quadrupole magnets are among the components to be upgraded in LHC interaction regions for the HL-LHC project. The new quadrupole magnets, called MQXF, are based on Nb3Sn superconducting magnet technology, with a conductor peak field of 11.3 T. CERN is in charge of the fabrication of the MQXFB variant, the longest Nb3Sn accelerator magnets designed and manufactured up to now, with a magnetic length of 7.2 m. Two magnets, MQXFBP3 and MQXFB02, reached the HL-LHC project requirements. However, they still exhibited a limitation at 4.5 K with a phenomenology similar to the one observed on the first two prototypes. After improvements on the cold mass (longitudinal welding) and magnet assembly (elimination of overstress on the conductor during loading) procedures, a series of modifications were implemented in MQXFB03 at the level of the coil fabrication to address and/or reduce weaknesses in the coils. The magnet was tested and was the first to achieve performance requirements at both 1.9 K and 4.5 K, with no signs of conductor limitation at 4.5 K. MQXFB is now in the series production phase, with around 2/3 of the coils completed and half of the magnets assembled. We provide in this paper an overview of the MQXFB program, with a summary of the main recent achievements and an overall status of the fabrication.

In a report published in 2021 by the Bank of America Global Research entitled "To the Moonshots: Future Tech Primer", 14 technologies for the future were listed and analyzed. One item of this list is Oceantech, including harvesting the ocean energies to also produce electricity. The report forecasted that by 2030, the ocean global economy (obviously including much more aspects than solely energy production) will be equivalent to 2010 German GDP, existing a general consensus on the tremendous impact and activity that it may generate in ocean energy generation, including that required for activities associated to the blue economy.. The ocean electric power that can be converted from an ocean planar wave is proporcional to the wave period and to the square of the wave amplitude but, to extract the maximum available power from the wave, the system must be able to be tuned which means having the availability of producing high reactive forces (proportional to its displacement or to its acceleration) which can be even higher than the required active force for producing energy. Consequently, Power Take-Offs (PTO) have always been at the focus of the research, development and innovation in the wave energy sector and they have been one of the main priorities for wave energy during the last years. As a result, the European Commission has funded several projects in recent years addressing its development and optimization under the Horizon 2020 calls, such as OPERA, WaveBoost, WETFEET, IMAGINE and SEA TITAN. MARES is a recently granted Horizon Project proposing the development of a novel concept for a PTO able to produce the required big forces very efficiently and in a compact way (high energy density) and disregarding permanent magnets-based solutions requiring enormous quantities of rare.earth materials. The use of a simple generator topology (such as a cylindrical switched reluctance machine) and novel superconductors such as HTS or MgB2, make the proposal even more attractive not only for wave energy conversion but also for other applications where very high force density are required. This paper will first introduce the MARES Project to describe next the conceptual design of the superconducting generator prototype, a machine that will include both technologies of new superconductors and that will be also fabricated and tested by the MARES consortium. The project also includes the implementation analysis of this PTO into two real cases of Wave Energy Converters

The High-Luminosity upgrade of the Large Hadron Collider (HL-LHC) is underway at CERN. The upgrade will rely, among other magnets, on the inner triplet quadrupoles (MQXF). The coils of these magnets are wound from Nb3Sn Rutherford cables experiencing magnetic fields of up to 12 T. High performance and precise control of cable dimensions (within a few mu m) are of primary importance for these accelerator magnets. The paper reviews the main characteristics of these cables and addresses the critical points of the design with respect to their use in HL-LHC. Then the status of the production of the superconducting cables is reported, with particular emphasis on the QA/QC procedures and data. Those procedures are performed to ensure that the series production cables conform to the tight technical requirements. Non-conformities identified during cable production are also presented and discussed.

Iron-based superconducting (IBS) wires fabricated through the powder-in-tube (PIT) method are prospective candidate materials for high magnetic field applications. In order to meet the requirements of such applications, it is important to obtain practical conductors with high transport critical currents at a competitive cost. Among the several IBS families, the (Ba,K)Fe2As2 (Ba-122) phase has the best potential to become a cost-effective high-field superconductor. However, two aspects of the fabrication procedure present issues which still hinder the development towards the affirmation of such superconductor in the industrial applications field: on one side the powder purity, especially when developing a route for the fabrication of large amounts, and on the other side the application of techniques scalable to obtain long length conductors with the same transport properties of the short samples. We here focus on an innovative and scalable fabrication process we have developed to fabricate pure Ba1-xKxFe2As2 powders in batches up to the order of 25 g, a quantity which allows us to fabricate at least 20 meters of monfilamentary conductor.

In this article, we investigate the influence of powder granulometry on the superconducting properties of (Ba0.6K0.4)Fe2As2 tapes manufactured using the Powder-In-Tube (PIT) technique. Variations in particle size distribution, which we successfully modulated through planetary ball milling and meticulous powder synthesis process, can affect the packing of the powders inside the metallic sheath and the mechanical deformation process of the samples, impacting their transport properties, as known for other practical conductors. The comparison among PIT tapes realized with a consistent fabrication route made with powders with different granulometries is reported, highlighting the effects on the transport property performances.

The magnets of the High Luminosity Upgrade of the Large Hadron collider (HL-LHC) will be electrically connected through Cold Powering Systems incorporating superconducting, 100 kA class, power transmission lines to direct current power converters in service galleries. These transmission lines or 'Superconducting Links' are based on multi-circuit magnesium diboride (MgB2) cables in 74.5-120 m long flexible cryostats. In the LHC tunnel, the Superconducting Links are electrically connected via niobium-titanium to the HL-LHC magnets and in the service galleries through flexible, round, rare-earth-barium-copper-oxide (REBCO) cables to current leads. We have established at CERN the cabling and quality control capabilities required to produce the REBCO cables of the HL-LHC Cold Powering Systems. In Q1 2024, we have successfully completed the assembly and the electrical and cryogenic cold testing of the 1st full system transporting combined currents of 94 kA while cooled with a helium gas flow rate flow of <= 5 g/s. In this manuscript we report on the cabling of the REBCO cables, the quality control process and results as well as on the splice performance during the cold test of the Cold Powering System.

The powering of the High Luminosity magnets of the Large Hadron Collider relies on Cold Powering Systems incorporating direct current superconducting lines, called Superconducting Links, based on magnesium diboride cables. A Cold Powering System interconnects the magnets in the accelerator existing tunnel to the power converters in newly excavated galleries that are about 8 m higher than the accelerator tunnel and up to about 100 m distant from the magnets. It feeds circuits rated at different currents and is designed to transfer a total current of up to |117| kA with magnesium diboride and Rare-Earth-Barium-Copper-Oxide technologies. After about ten years of development, the first Cold Powering System was successfully constructed and tested at CERN. The Superconducting Link was measured in a geometrical configuration that included a vertical path simulating the final routing in the accelerator underground. The test campaign validated the mechanical, cryogenic and electrical performance of the system both in steady state conditions and under various transient scenarios. This paper reports on the results of the tests and details the performance of the first ever built magnesium diboride and Rare-Earth-Barium-Copper-Oxide 100 kA class superconducting system.

The High Field Magnet (HFM) program foresees, among others, the systematic measurement and assessment of mechanical, thermal, and electrical properties of high temperature superconductors (HTS) cables. These measurements are a key factor to characterize the conductor, verify its performance and control the production quality. These values are also necessary inputs to size the prototype magnets that will use HTS windings. Cable and coil properties must be measured at room temperature, in liquid nitrogen, in helium gas at 20 K – 30 K, and in liquid helium at about 5 K. Cable samples and small coils are tested at different temperatures, and under a given force or deformation. The mechanical and electrical loads can be applied simultaneously or in different combinations. The output data span over a large range of signals: strain measured by strain gauges, optical fibers, or digital correlation techniques, critical currents, displacements, and structural deformations. At the moment, any cable property can be measured individually. The proposed multipurpose test facility is a testing station capable of simultaneous measurements to facilitate the development of correlation laws: for example, by powering a small HTS coil at 20 K while measuring its deformation via digital image correlation; or measuring the critical current in a sample under a given mechanical pressure or after a certain amount of load cycles. Another important requirement is the flexibility and the short turnaround time to test samples. This note describes the multipurpose test facility designed at CERN and under construction. Some examples of possible measurements are given as well.

The HL-LHC IT String, a test facility for the major components of the HL-LHC Inner Triplet, is currently in its construction and commissioning phases in a surface building at CERN. The primary motivation of the HL-LHC IT String is to study and validate the collective behaviour of its different subsystems which include mainly: the inner triplet superconducting magnets and their correctors, a novel superconducting link, the cryogenics infrastructure for the cooling and quench recovery, the powering and quench protection systems, and the remote alignment system. The HL-LHC IT String is a multi-disciplinary project that integrates novel superconducting technologies and requires the contribution of multiple stakeholders. Throughout the construction and commissioning, it involves a significant number of co-activities that must be safely managed, considering the safety and operational requirements of neighbouring testing facilities located in the same buiding. During its operation, multiple failure modes can occur for which a detailed risk assessment has been conducted to address and mitigate them. The safety aspects of the HL-LHC IT String are of key importance and have been duly addressed. In this paper we will first introduce the HL-LHC IT String facility. Then we will focus on methodologies employed for safety assessments and explore how safety measures are implemented during the different phases of design, construction, commissioning, and operation of the cryogenic and superconducting systems.

Much information is lacking at present on the electrical properties of commercial REBCO tapes. This work, which builds on a previous paper of the same authors, presents the results of an experimental campaign aimed at deriving the critical current of tapes from SuperPower, Fujikura, Faraday Factory, and Shanghai Superconductor Technology. The campaign was conducted by applying both the transport method at 4.2 K, in perpendicular background magnetic fields of up to 15 T, and the magnetization method from 4.2 K up to the critical temperature in fields of up to 10 T. This latter method was adopted to determining the so-called crossover field, B0, at which the transition from single vortex pinning to collective pinning takes place. B0 is challenging to determine by the transport method because of the high currents involved (at 4.2 K, B0 is roughly 1 T, which corresponds to currents above 1500 A, for a 4 mm tape). Magnetization measurements corroborate transport measurements at 4.2 K both below B0 and up to 10 T. Further magnetization measurements above 4.2 K allow the temperature dependence of the scaling parameters to be derived, for correlation with the methodology of flux pinning enhancement by different manufacturers. This provides insights about the effectiveness and interplay of pinning mechanisms.

The High Luminosity-Large Hadron Collider (HL-LHC) project at CERN aims to increase the integrated luminosity of the Large Hadron Collider by an order of magnitude compared to the LHC original design performance. To achieve this, the existing magnets surrounding the CMS and ATLAS experiments will be replaced with next-generation, high-performance superconducting magnets featuring larger apertures and higher magnetic fields than those currently used in the LHC. These magnets will be powered using a novel superconducting link and state-of-the-art power converters. Upgraded quench detection and protection systems will protect the magnet circuits. This work provides a comprehensive overview of the HL-LHC magnet circuits and their associated complexities. The commissioning methodology for the HL-LHC magnet circuits is outlined, detailing its validation within the HL-LHC Inner Triplet String test facility, currently under construction, prior to deployment within the CERN accelerator complex. These procedures ensure the reliability and operational readiness of the upgraded systems, paving the way for a successful magnet circuits operation in the HL-LHC era.

The shift from fossil fuel to electric based propulsion in the waterborne transport sector has been sped up by recent policies aiming to reduce the sector emissions. This trend creates highly electrified vessels, with needs for energy storage systems (ESS) to satisfy the power demand affordably and to increase the on-board grid reliability and efficiency. Initial industry efforts have been put in the study and integration of high energy density ESS solutions, mainly electrochemical batteries. However, other innovative ESS, with different capabilities, have not been yet fully addressed. It is the case of Fast Response Energy Storage Systems (FRESS), such as Supercapacitors, Flywheels, or Superconducting Magnetic Energy Storage (SMES) devices. The EU granted project, POwer StoragE IN D OceaN (POSEIDON) will undertake the necessary activities for the marinization of the three mentioned FRESS. This study presents the design process followed in the POSEIDON project for the definition of an SMES suitable for maritime operation. First, the boundary conditions imposed by the marine environment, and the potential on-board applications of the SMES will be established. Next, the technological options: superconducting material, cooling system, coil fabrication and magnet topology which have been selected for this specific system will be presented.

Future high-field magnets for particle accelerators hinge on the crucial development of advanced Nb3Sn wires engineered to withstand the large stresses generated during magnet assembly and operation. The superconducting properties of Nb3Sn enable the design of compact accelerator-quality magnets above 10 T, but at the same time the brittleness and strain sensitivity of the material impose careful consideration of the mechanical limits. In addition, accelerator magnets are wound using Rutherford cables and the cabling process generates deformations in the wire that can affect its electro-mechanical performance. This paper reports on the impact of the rolling deformation on the transverse stress tolerance of high-performance restacked-rod-process (RRP (R)) and powder-in-tube (PIT) Nb3Sn wires. Rolling deformation was used to mimic the effect of cabling on the wire shape. Deformed samples were compared to reference round wires in term of stress dependence and irreversible limit (sigma(irr)) of the critical current (I-c) under transverse compressive loads up to 240 MPa. Experiments were performed at 4.2 K, 19 T, on resin-impregnated single wires that imitate the operating conditions in a Rutherford cable of an accelerator magnet. The results show that rolling deformation has a detrimental effect on the initial I-c of PIT wires, but it does not influence the behavior of the wire under stresses above 70 MPa. On the other hand, the deformation of RRP (R) wires leads to an improved sigma(irr) without affecting the initial I-c. Additionally, a 2D-mechanical finite element method model of the RRP (R) wire was developed to investigate the impact of the wire geometry on the plastic deformation of the copper matrix, which induces residual stresses on Nb3Sn and is the main cause for the permanent reduction of I-c. Based on the model results, an alternative layout of the wire was proposed that improves its stress tolerance without affecting its electrical transport properties.

A number of physics experiments call for the use of iron-dominated, normal-conducting electromagnets to produce moderate fields (2 T range) in a large gap or over a large volume. Although robust and reliable, these magnets require significant electrical power, in the MW range, and can thus be costly to operate, especially in DC mode. We report on the design and test of a superconducting, proof-of-principle demonstrator that makes use of technological developments carried out for the High Luminosity upgrade of the Large Hadron Collider at CERN (HL-LHC). The demonstrator includes a superconducting coil, wound from a MgB 2 cable, and mounted inside an iron yoke with a 62 mm gap. As a first phase, the demonstrator was successfully tested in liquid helium at 4.5 K, generating a magnetic flux density of 1.95 T at a current of 5 kA. In a second phase, currently under preparation, the demonstrator will be tested in gaseous helium at 20 K. The design concepts of the demonstrator can be scaled up to large, iron-dominated electromagnets.