The heavy-fermion superconductor UTe2 is unique in that, at ambient pressure, it exhibits three distinct superconducting phases, two of which are induced by magnetic field. When the field is applied along the crystallographic b axis in the orthorhombic structure, the field-induced phase SC2 develops above approximately 20 T and persists up to the metamagnetic transition at Hm about 34 T. When the magnetic field is tilted towards the c axis, another superconducting phase, SC3, emerges at very high fields above about 40 T over a certain angular range. The origin of this exotic phase remains under debate. One of the key open questions regarding the origin of SC3 is whether it is confined to the spin-polarized state above Hm, or whether it already develops at lower fields. Here, we report magnetoresistance measurements performed on a high-quality single crystal of UTe2 in static magnetic fields up to 42 T applied in the (bc) plane at temperatures down to 0.35 K. At this temperature, we find that the SC3 phase first appears at an angle of 20 deg from the b axis. At larger angles, the onset of the SC3 phase, defined by a maximum in resistivity, occurs below Hm. However, zero resistivity is reached only above Hm throughout the entire angular range investigated. These results are summarized in the resulting field-angle phase diagram. Furthermore, we find that at 21 deg the SC3 phase is rapidly suppressed with increasing temperature, whereas at 24 deg it becomes considerably more robust and persists up to about 1 K. Finally, we observe Shubnikov de Haas (SdH) oscillations in the vicinity of the c axis. The observed oscillation frequencies are in good agreement with our previous results. The field dependence of the strongest SdH frequency and of the effective mass is discussed.

REBCO double pancake (DP) coils were fabricated using HTS tapes from four manufacturers: 1) THEVA (TV), 2) Shanghai Superconductor Technology (SST), 3) Faraday Factory Japan (FFJ) and 4) Fujikura (FJK). The three first tapes represent improved versions addressing issues highlighted in our prior study. During coil winding, the physical properties of each tape-specifically delamination strength and windability-were evaluated. To assess practical electrical performances and mechanical robustness, three mock-up magnets were assembled using pairs of metal-as-insulation (MI) DP coils: TV, SST, and FJK. A mock-up magnet could not be fabricated with FFJ tape due to severe coil deformation. All magnets were pre-tested in liquid nitrogen at 77 K under self-field conditions to measure coil and time constants, and joint resistances. Quench currents were evaluated under various external magnetic fields and temperatures. Additionally, the time constant before and after quench events were measured to investigate changes in contact and surface resistance.

We seek the conditions in which Alfvén waves (AW) can be produced in laboratory-scale liquid metal experiments, i.e. at low magnetic Reynolds Number ( $Rm$ ). Alfvén waves are incompressible waves propagating along magnetic fields typically found in geophysical and astrophysical systems. Despite the high values of $Rm$ in these flows, AW can undergo high dissipation in thin regions, for example in the solar corona where anomalous heating occurs (Davila, Astrophys. J., vol. 317, 1987, p. 514; Singh & Subramanian, Sol. Phys., vol. 243, 2007, pp. 163–169). Understanding how AW dissipate energy and studying their nonlinear regime in controlled laboratory conditions may thus offer a convenient alternative to observations to understand these mechanisms at a fundamental level. Until now, however, only linear waves have been experimentally produced in liquid metals because of the large magnetic dissipation they undergo when $Rm\ll 1$ and the conditions of their existence at low $Rm$ are not understood. To address these questions, we force AW with an alternating electric current in a liquid metal in a transverse magnetic field. We provide the first mathematical derivation of a wave-bearing extension of the usual low- $Rm$ magnetohydrodynamics (MHD) approximation to identify two linear regimes: the purely diffusive regime exists when $N_{\omega }$ , the ratio of the oscillation period to the time scale of diffusive two-dimensionalisation by the Lorentz force, is small; the propagative regime is governed by the ratio of the forcing period to the AW propagation time scale, which we call the Jameson number $Ja$ after (Jameson, J. Fluid Mech., vol. 19, issue 4, 1964, pp. 513–527). In this regime, AW are dissipative and dispersive as they propagate more slowly where transverse velocity gradients are higher. Both regimes are recovered in the FlowCube experiment (Pothérat & Klein, J. Fluid Mech., vol. 761, 2014, pp. 168–205), in excellent agreement with the model up to $Ja \lesssim 0.85$ but near the $Ja=1$ resonance, high amplitude waves become clearly nonlinear. Hence, in electrically driving AW, we identified the purely diffusive MHD regime, the regime where linear, dispersive AW propagate, and the regime of nonlinear propagation.

The Grenoble Hybrid magnet is a modular user platform based on resistive and superconducting technologies. It will produce various high DC magnetic field and flux configurations ranging from 43 T in 34 mm diameter with 24 MW of electrical power to 9 T in 810 mm diameter, when the superconducting coil is used alone. Thanks to the ongoing upgrade of the electrical power installation at LNCMI-Grenoble to 30 MW, the opportunity to increase the total field significantly above 45 T was anticipated for the superconducting part and will require an optimization of the resistive inserts. The large-bore “outsert” coil of the Grenoble hybrid magnet is based on a specifically developed Nb-Ti/Cu superconducting conductor. The magnet cryostat with its support structure includes an eddy-current shield and is connected via a cryogenic line to a cryogenic satellite, fed by a fully dedicated 150 l/h He liquefaction plant. All parts have been built, tested and delivered to LNCMI-Grenoble, where integration and final assembly were successfully completed. The commissioning tests of the overall system started in 2022. Progress is reported together with the main problems encountered and solved, such as successful cooling of the superconducting coil down to 1.85 K with pressurized superfluid He. The first powering cycles and tests of the magnet safety systems are described with gradual current increases in the superconducting coil alone and then combined with the powering of resistive inserts as well as the initial precise magnetic characterizations using a 1 H NMR probe.

Tangent cylinders (TCs) have shaped our understanding of planetary dynamos and liquid cores. The Taylor-Proudman constraint creates these imaginary surfaces because of planetary rotation, separating polar and equatorial regions, but cannot explain the flows meandering through them. Here, we establish and verify experimentally that magnetic fields aligned with rotation drive flows into TCs, linked to the flows along TCs by a magnetic Taylor-Proudman constraint. This constraint explains and quantifies how magnetic fields reshape rotating flows in planetary interiors and magnetorotating flows in general.

High-strength, high-conductivity copper/silver-alloyed materials were prepared by cold-spray (CS) manufacturing. For DC high-field application at room temperature, bulk Cu/Ag (5% vol. Ag) alloys with high mechanical properties and high electrical conductivity can be obtained by CS and post-heat treatments. For pulsed-field application at liquid nitrogen temperature, bulk Cu/Ag (5% vol. Ag) alloys serve as precursors for room-temperature wire drawing. The Cu/Ag-alloyed bulk CS deposit presents a high yield strength of about 510 MPa with a corresponding electrical resistivity of 1.92 µΩ·cm (at 293 K). The Cu/Ag-alloyed wires show a very high ultimate tensile strength (1660 MPa at 77 K or 1370 MPa at 293 K) and low electrical resistivity (1.05 µΩ·cm at 77 K or 2.56 µΩ·cm at 293 K). Microstructural studies via STEM allow us to understand this very high level of mechanical strength. The results evidence that materials developed by CS exhibit very high mechanical properties compared to materials prepared by other routes, due to the high velocity of the deposited particles, which leads to high initial deformation rates and specific microstructural features.

A refurbished metal-as-insulation (MI) HTS insert comprised of DP coils with replaced inner joints was charged under various magnetic field ( B ext ) from 0 to 18 T at 4.2 K for testing. However, the refurbished insert could not be charged up to its maximum field, because the cryogenic condition tended to be unstable with a high helium boiling rate above 28 T. Therefore, to investigate the cooling issue, four Cernox sensors were installed in refurbished insert. The temperature of each position while powering the insert was measured under various B ext . In addition, we qualified a new simplified protection scheme without the usual detection and dump circuit during a quench at B ext = 9 T of the insert. Detailed experimental results about charging and quenching tests of the insert are presented and discussed in this paper.

We describe the magnet challenges for a Muon Collider, an exciting option considered for the future of particle physics at the energy frontier. Starting from the comprehensive work performed by the US Muon Accelerator Program, we have reviewed the performance specifications dictated by beam physics and the operating conditions to satisfy the accelerator needs. Among the many magnets that make up a muon collider, we have identified four systems that represent well the envelope of challenges: the target and capture solenoid, the final cooling solenoid, the accelerator dipoles and the collider dipoles. These systems provide focus for the development of novel concepts, largely based on HTS for reasons of performance, cost and sustainability. After giving a consolidated overview of the needs for the magnet systems, we describe here the basic technology options considered, and the plan for design and development activities.

The electrodeposition of copper (Cu), silver (Ag), and their alloys has been a subject of interest since the 19th century. Primarily due to their exceptional features such as good mechanical hardness and electrical conductivity, high resistance to corrosion, and electromigration, Cu–Ag electrodeposits continue to be investigated and developed to improve their properties for different applications. This paper reviews the state of the art in the field of electroplated Cu–Ag alloys in an aqueous solution, with particular emphasis on the observed properties and variety of electrochemical processes used to produce high-quality materials. Moreover, this review paper focuses on the experimental conditions employed for Cu–Ag electrodeposition, intending to understand the basis and manipulate the processes to obtain coatings with superior characteristics and for attractive usage. Finally, the most trending applications of these coatings are discussed depending on different parameters of electrodeposition to provide prospects for potential research.

The physical and electrical properties of four recent REBCO CC were assessed: 1) THEVA; 2) Shanghai Supercond. Technology; 3) Faraday Factory Japan; and 4) Fujikura. For estimating their physical properties, the delamination strength of each tape was checked by removing a polyimide ribbon sticked on the tape and by cutting the tape after pre-tinning. Their windability and the uniformity of their thickness were also investigated through our metal-as-insulation winding process. For evaluating their electrical properties, their critical current was measured at 4.2 K under various external magnetic fields perpendicular to their ab-plane. Joint samples of each tape were fabricated and tested in a bath of liquid nitrogen at 77 K in self-field. The results are described in this paper for the four tapes.

This study is a sequel to our previous study on a 38 mm diameter cold bore metal-as-insulation (MI) HTS insert that reached 32.5 T in a 18 T background magnetic field. For refurbishing, 7 MI double-pancake (DP) coils were re-wound with used REBCO tapes to just replace the damaged HTS pieces by new ones at inner junctions. 2 DP coils were fully fabricated using new REBCO tapes. The new assembled insert was then tested under various background magnetic fields at 4.2 K. The key focuses of this paper are: 1) the damages in the DP coils; 2) their repair; 3) the characteristics resistance change of the insert; 4) the resistance value of each DP coil; 5) the maximum field of the HTS-resistive hybrid magnet; and 6) the field stability estimation of the hybrid by NMR characterization.

The design and operation of resistive high field magnets require research and development in materials science, power supply engineering and instrumentation. Recently, their energy efficiency has become a very important concern. In our contribution we report on recent advances on an energy efficient use of the 24 MW resistive magnets at the French National High Magnetic Field Laboratory at Grenoble (LNCMI) that can reduce their energy consumption by up to 20%, for a given user experiment. This saving is possible due to a special architecture of the LNCMI high field magnets. Namely, the total magnetic field is provided by two independent concentric sub magnets exhibiting different field characteristics, i.e., absolute field values for a given current and spatial field distributions. As both sub-magnets can be powered in an independent way, their currents can be tuned to minimize the total electrical power for a target magnetic field requested by the user. This enables energy efficient operation. However, the consequences of strain enhancement on magnet safety and life time due to higher current densities in the inner sub magnet have to be considered. LNCMI magnet design, power supply and instrumentation teams have recently implemented this innovative operation mode in a collaborative project. We will present its technical realization including electrical power modelling, magnet load estimations as well as first benchmark experiments including NMR. Finally, we will discuss the perspectives of this operation mode for innovative user experiments.

L. Bottura1, D. Aguglia1, B. Auchmann2, T. Arndt3, J. Beard4, A. Bersani5, F. Boattini1, M. Breschi6, B. Caiffi5, X. Chaud7, M. Dam8, F. Debray7, E. De Matteis8, A. Dudarev1, S. Farinon5, A. Kario9, R. Losito1, S. Mariotto8,10, R. Musenich5, T. Ogitsu11, M. Prioli8, L. Quettier12, L. Rossi8,10, D. Schulte1, C. Senatore13, M. Sorbi8,10, M. Statera8, H. Ten Kate9, R.U. Valente8, A. Yamamoto1,11, Y. Yang14

The French National Laboratory for High Magnetic Fields (LNCMI) provides high magnetic fields for an international community of users. On the site of Grenoble DC electricity is used to feed dedicated high power electro-magnets to produce steady magnetic fields. The magnets electrical consumption is fully dissipated as heat at variable temperatures. An ongoing project for the LNCMI electro-intensive installation analyses the opportunities for waste heat recovery into the nearby district heating network. Recent studies have pointed out energy recoveries of the order of 20% considering waste heat at 35 °C heat pumped to 85 °C and a thermal storage. One of the main reasons for this low recovery rate is the temporal mismatch between the LNCMI's activities and the district's residential heat needs. From 2020, the LNCMI has signed a new electricity contract that provides more flexibility to the high field experiment planning. Two strategies are explored to improve the waste heat recovery energy and exergy rates. Firstly, the rescheduling of the LNCMI planning of experiments in order to mitigate the temporal mismatch. Secondly, management of the cooling loops of the process to adjust waste heat at relevant temperatures. The energy analysis accounts for recovered heat quantity, while the exergy analysis accounts for the major sources of irreversibility within the LNCMI's processes. MILP optimisation problem formulation and solving proved these two strategies to be energy and exergy efficient for the LNCMI waste heat recovery. This work offers promising research and operational perspectives for flexible energy systems optimal management with both energy and exergy criteria.

In this paper we elaborate on the nature and challenges for the magnet systems of a muon collider as presently considered within the scope of the International Muon Collider Collaboration (IMCC). We outline the structure of the work proposed over the coming period of five years to study and demonstrate relevant magnet technology. The proposal, which is part of the overall work planned to establish feasibility of a muon collider, is in direct response to the recent recommendations received from the Laboratories Directors Group (LDG). The plan is to profit from joint activities, within the scope of the IMCC and beyond, implemented through direct and EU-funded contributions.

SEISM is a unique ECR ion source operating at a frequency of 60 GHz. The prototype is based on a simple magnetic geometry, the cusp, allowing the use of polyhelix coils (developed with LNCMI, Grenoble) to generate the closed ECR surface at 2.14 T. The plasma is sustained by a high intensity HF pulse (up to 300kW). Previous experiments at LNCMI have successfully demonstrated the establishment of the nominal magnetic field and the extraction of ion beams with a current density up to 1 A cm(-2). The presence of afterglow peaks was also observed, proving the existence of ion confinement in a CUSP ECR source. An experimental campaign is carried out in 2021 using a new transport line designed to improve the transmission of the beam to the new detectors. Short and long-term research plans are presented to transform this high current density into a high intensity ion beam that can be used for accelerators of the future.