In recent decades, a pioneering field of research has been investigating to reproduce the enormous power of the sun nuclear fusion reactions in a relatively small apparatus, i.e. a tokamak. This machine generates a closed magnetic field configuration able to supply and control an ionised plasma. The magnetic system is made by three main components: the Toroidal Field (TF) Coils for the primary...
The Divertor Tokamak Test (DTT) facility is being built at ENEA Frascati (Italy), to address the development of a power exhaust system capable to handle the large heat fluxes expected to be deposited in fusion reactors on the plasma facing components.
DTT will be a compact and flexible fusion experiment relying on low-temperature superconducting magnets for the plasma confinement. The magnets...
The magnet feeders are critical systems of fusion reactors since they represent the interface between the in-cryostat components and the external environment. By realising the required electrical, cryogenic and mechanical connections, as well as hosting instrumentation cables, the feeders ensure the safe operation of the superconducting magnets. Therefore, the design and integration study of...
High-current superconducting switches can simplify the energy extraction in large magnet systems. For example, they can replace mechanical and vacuum breakers in the conventional electrical circuit of TF coils for fusion magnets, thus mitigate the risk of arcing. Vast majority of current leads to room temperature can be eliminated, and the cryogenic power consumption can be substantially...
In collaboration with CERN and CNAO, INFN is developing a demonstrator of a curved dipole as a key element of a superconducting gantry for hadron-therapy cancer treatments. The baseline project includes a cos-theta NbTi 4 T dipole with a radius of curvature of 1.65 m, an aperture of 80 mm and ramp rates up to 0.4 T/s. Considering the inherent difficulty of winding a curved coil, in parallel we...
Facility for Antiproton and Ion Research (FAIR) is the particle accelerator facility currently being under construction by at GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany.
The SIS100 ring accelerator has a circumference of 1,100 meters and can accelerate the ions of all the natural elements in the periodic table to speeds as high as 99% of the speed of light. The SIS 100...
Since dependable conductor models can be based on 1-D thermal-hydraulic problems, coupled simulation scheme has established itself as a practical approach to evaluate the design of large-scale superconducting magnets. By integrating well-established numerical models around the core of superconducting magnet, i.e. the conductors, such a concept of coupled solution, known as co-simulation...
The Central Solenoid (CS) of the EU DEMO is under design within the EUROfusion Consortium. Two different design options are under investigation. One option is based on Low Temperature Superconducting (LTS) Cable-In-Conduit Conductors (CICCs), following an ITER-like design approach. The other option is to employ both High Temperature Superconducting (HTS) and LTS materials to build an hybrid...
Abstract
High Temperature Superconductors (HTS) are very promising materials to be applied in future fusion magnets. HTS conductors are already considered as a possible option for some components of the superconducting magnet system of the EU DEMO tokamak, which are being designed by the EUROfusion consortium, e.g. for the innermost subcoil of the Central Solenoid coils developed by the...
In the EU DEMO reactor, currently in its pre-conceptual design phase, power exhaust represents a major challenge, asking for a new, robust design of the divertor. To address this issue, the Divertor Tokamak Test (DTT) facility is being built in Italy. It will be a compact and flexible tokamak, allowing the implementation of several plasma configurations as test bed of DEMO-relevant divertor...
In the context of the High Luminosity upgrade of the Large Hadron Collider (HL-LHC) at CERN, a numerical framework has been developed to systematically assess the temperature distribution in complex He II-cooled magnet geometries using open-source software. The precise knowledge of the magnet's thermal characteristics and heat extraction performance is essential in determining safe operating...
An assembly of coated conductors wound spirally on a copper core such as a CORC® wire is one of the most popular types of high current coated conductor cables. In such a cable, the current sharing by the copper core as well as the current sharing between coated conductors plays a key role for its quench protection. We conducted quench experiments using the simplest configuration, in which one...
The Conductor-On-Round-Core (CORC) is a promising design for obtaining cables made of second-generation high-temperature superconducting (HTS) wires. These cables are primarily intended for high-field magnets, but their small size and excellent current-carrying performance make them an attractive solution for AC power applications as well. The AC loss level is an important factor affecting the...
Coated conductors with magnetic substrates are thin multilayer structures; their high aspect ratio and nonlinear material properties present significant difficulties for numerical simulation. Using the high width-to-thickness ratio of coated conductors we derive an integral formulation for a new model [1] based on an infinitely thin approximation for the superconducting layer and a quasistatic...
In the framework of the studies on high field magnets for future accelerators, a specific project called ASTRACT, involving INFN, CNR/SPIN, ENEA and the University of Genoa, is focused on the effect of transverse strain on the critical current of $Nb_3Sn$ wires. The first phase of the project concerns the effects of strain imposed on $Nb_3Sn$ wires before heat treatment and the development of...
The development of accelerator magnets able to produce magnetic fields beyond those attained in the main magnets of the Large Hadron Collider (LHC) requires the use of conductors with enhanced superconducting properties with respect to the well-known Nb-Ti technology. In the present days, Nb3Sn has become the preferred choice for the windings of such new high-field designs, thanks to its...
The SMC (Short Model Coil) program was started at CERN around 2008 to develop the Nb3Sn technology. The small magnet structure allowed relatively cheap and fast test of various superconducting coils. One of the key questions was the relation between the pre-stress and the magnet’s performance, to measure which dozens of strain gauges were installed on the coil, axial tie-rods and the external...
The most common type of models used to analyzed the design of the toroidal field (TF) coils of tokamaks rely on the homogenized mechanical properties of the winding pack (WP). Such approach simplifies the model and reduces the computational time at the cost of introduced simplifications, the main one being the loss of information on the stress and strain fields inside the WP. In this work a...
Cryogenic devices have to be protected against accidental overpressure by installing pressure relief devices such as valves or rupture discs. The sudden loss of the insulating vacuum is often considered as the major accident, with the highest heat fluxes transmitted to the fluid.
Up to now, the design of safety devices was based on the use of experimentally measured standard heat flux...
The Divertor Tokamak Test (DTT) facility is a fully superconducting tokamak currently being built in the ENEA Frascati laboratories (Italy) to study the power exhaust issue in EU DEMO perspective.
The massive Toroidal Field (TF) magnets require a robust Gravity Support (GS) to sustain their weight. The GS is a stainless steel column in thermal contact at the bottom to the cryostat base at...
Spiral coated conductor cables, in which multiple coated conductors are spirally wound around a circular cross-section metal core, such as CORC-like cables, have advantages such as high mechanical freedom and high current capacity. Such cables are expected to be used in various applications, such as magnets for accelerators and nuclear fusion, and coils for rotating machines and generators....
The Coated Conductor (CC) tapes seem to be prospective for the production of magnets and cables, because of a high upper critical magnetic field as well as temperature, and competitive critical current density in combination with good mechanical properties. On the other hand, the superconducting layer may exhibit high energy dissipation in the external magnetic field because of rather large...
Coherent and accurate modelling in multiple domains of superconducting magnets is challenging as their behavior is usually the result of complex interactions of physical effects on different temporal and spatial scales. However, for example, for the performance analysis of the LHC main dipole circuits, it is important to be consistent across the time- and frequency domains.
A modelling...
The combination of the superconducting and ferromagnetic materials may produce a special kind of magnetic shield, called the magnetic cloak. It offers magnetic shielding while the external magnetic flux lines are not distorted by him. However, because of the presence of the earth's magnetic field, some magnetic flux remains frozen inside the cloak after cooling it down. This phenomenon may be...
