The IPP team operated the W7-X superconducting magnet system at 1.8 T on the plasma axis in the last quarter of 2024. In contradiction to the standard 2.5 T operation the operating current in the conductors was significantly lower (11.027 kA vs. 15.32 kA). Both the lower magnetic field and the lower current affect the hotspot temperature in case of a fast discharge of the coils. Quench...
In 2024, EUROfusion consortium released a new DEMO baseline with a slightly reduced aspect ratio (A=2.8 instead of 3.1), major radius (8.6 m instead of 9.1 m) and magnetic field (4.4 T instead of 5.2 T on the plasma axis) compared to the previous 2018 baseline. The fusion power is targeted to 1.65 GW. The design of all DEMO magnets have been updated in 2025. In this study, we present the...
This work presents a numerical modeling framework for quench protection in the non-planar superconducting magnets of the GIGA stellarator reactor (Gauss Fusion), which store energies on the order of 100 GJ. The study focuses on the development and application of a predictive multi-physics model for an innovative active protection concept that eliminates external dump resistors by using the...
Bringing back the substantial idea of hybrid contact discontinuity (A. Shajii and J. P. Freidberg, 1996), thermally coupled 1-d fuild-solid system is carefully repriced on the fundamental question what is the best approach to the quench propagation model of superconducting CICC (cable-in-conduit conductor). By means of a mode analysis with the exact dispersion relation, the simple equations of...
The KSTAR superconducting magnet system has been operated for over a decade under repeated thermal cycles and diverse plasma scenarios. This study investigates the evolution of key operational characteristics of the Nb₃Sn coils, with specific emphasis on low dI/dt conditions. Due to the absence of a low-frequency filter in the power-supply system, low-frequency components of the current...
Conventional fusion magnet system typically discharges the stored energy by external discharge resistors as a quench protection with a relatively short time constant, such as < 15 s for ITER magnets [1]. However, the resulting coil voltage to ground can exceed several kV, increasing the risk of accidental Paschen discharge or arcing. In addition, quench protection relying on the external...
The ITER project represents a cornerstone of the global effort to achieve controlled thermonuclear fusion, with the objective of demonstrating the feasibility of sustaining a burning plasma and paving the way for future fusion power plants. Among its most critical subsystems are the Toroidal Field (TF) magnets, massive superconducting coils responsible for generating the strong and steady...
To achieve the realization of a 10 TeV Muon Collider facility and reduce the ring dimension to minimize muon decay, the main bending dipole magnets must generate high magnetic fields up to 16 T. Additionally, the superconducting coil aperture must accommodate thick tungsten shielding to protect the magnet from muon decay products. These challenging requirements motivate the investigation of...
The Coated Conductor (CC) tapes appear to be promising for the production of magnets and cables due to their high critical magnetic field and temperature, as well as competitive critical current density, in combination with good mechanical properties. On the other hand, the superconducting layer may exhibit high energy dissipation in an external magnetic field due to the relatively large...
Within the French exploratory program SupraFusion, we investigate fast and reliable quench detection and protection strategies for insulated REBCO coated-conductor stacks intended for fusion-relevant, high-field magnet systems. Because these insulated windings show very slow normal-zone propagation and hold large magnetic energies, conventional voltage-tap detection often reacts too late,...
Fast and reliable quench detection is one of the key challenges in the development of HTS magnets with large stored energy, in the range of MJ and higher. Several temperature-based detection methods are under study at EPFL Swiss Plasma Center, including twisted-pair superconducting wires (SQD), shielded thermocouple chains (TCC) and fiber-optics sensing (FOS). Integrating them into the winding...
The central solenoid (CS) of a tokamak is engineered to withstand significant fluctuations in operating currents and rapid changes in magnetic fields. These capabilities are essential for initiating plasma breakdown and ensuring subsequent plasma shaping and control. A novel design has recently been introduced for the CS system designated for the next-generation experimental fusion device....
Different magnetic confinement fusion projects, as SPARC, STEP, and EU DEMO among others, will (or are considering to) employ High Temperature Superconductors (HTS) in their magnet system, due to the possibility to generate an higher magnetic field if compared to Low Temperature Superconductors (LTS), which are considered the state of the art in superconductors.
Even if HTS would increase...
The DEMO (Demonstrator Power Plant) project is a magnetic-confinement demonstrator for a fusion power plant. Since the cryo-magnetic system is expected to represent a major cost, it must be carefully considered, particularly from the perspective of the superconducting material inventory and the associated cooling facility. In this paper, we explore the main cost factors of the cryo-magnetic...
Following the CHART/PSI roadmap toward insulated REBCO-based high-field magnets, and after the completion of the first REBCO Subscale magnet (RS1), we aim to design a subscale demonstrator for a double-aperture high-field magnet featuring field alignment between the wide face of the cable and the magnetic field. The objective of this development is a reduction of field errors and ramp losses,...
Fusion magnets experience sharp dB/dt excursions, especially during plasma breakdown and current ramp-up. Calculating the instantaneous power dissipation is therefore essential for quantifying, through thermal-hydraulic simulations, the local heat load that must be handled. Toward this purpose, we have developed a modelling framework, combining analytical formulations with finite-element...
The design of superconducting magnets demands a multi-phase, multi-scale and multi-physics approach which can be more or less challenging according to the complexity of the requirements. According to the different schools, the design effort is usually performed in three or four phases: we can identify them starting from the simplest to the most complex as feasibility design, conceptual design,...
The design of superconducting magnet for a high-energy Muon Collider continues to push the limits of present magnet technology, requiring new ideas that go beyond those encountered in conventional LTS systems. In this context, we are exploring a block-coil dipole concept specifically tailored to the unconventional boundary conditions imposed by muon physics: intense radiation from muon decay,...
A Muon Collider is one of the most promising options for the post-LHC era, offering leptonic precision without the limitations of synchrotron radiation that affect electron machines. Its feasibility, however, is strongly constrained by the short muon lifetime (2.2 μs), which demands extremely rapid production, acceleration, cooling, and collision—posing severe technological challenges.
Among...
High-temperature Rare-Earth Barium Copper Oxide superconductor tapes are considered for devices with time-varying magnetic fields, which means they will be affected by cyclic mechanical loading and AC losses. A recent trend for lowering the AC loss of REBCO tapes is filamentization. The influence of filamentization on the mechanical strength of REBCO tapes is being actively investigated – both...
Over almost a decade, the ‘Little Big Coil (LBC)’ program at the Applied Superconductivity Center (ASC) of the National High Magnetic Field Laboratory (NHMFL) has focused on investigating the various limitations of rare-earth barium copper oxide coated conductors (REBCO CCs) in high-field (>40 T) and high-stress (>800 MPa) environments. Under the key philosophy of “no magnets are better than...
A large range of HTS cable and magnet design for high field accelerators is currently being studied and modelled, while the validation of models by experimental results is still rather limited. At the SM18 magnet test facility at CERN various types of HTS magnets have been tested, including insulated, metal insulated and non-insulated coils, with a range of instrumentation including high...
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...
During operation, the Cable in Conduit Conductors (CICC) of the ITER Toroidal Field (TF) coils are exposed to severe electromagnetic forces [1]. These forces are in part hoop load and in part crushing load on the strands pressed by the Lorentz-force against the inner wall of the jacket. In addition, the differential thermal contraction between the steel jacket and the superconducting strands...
