Periodic Reporting for period 3 - SuperEMFL (Superconducting magnets for the European Magnet Field Laboratory)
Reporting period: 2024-01-01 to 2024-12-31
The magnetic field is a powerful thermodynamic parameter to influence the state of any material system and therefore an outstanding experimental tool for physics, material science and beyond. Higher magnetic fields brought higher resolution for analyzing materials, more opportunities to discover new phases, properties or materials. To go beyond the conventional commercially available superconducting (SC) magnets, very large infrastructures such as the ones gathered within the European Magnetic Field Laboratory (EMFL) are necessary.
The SuperEMFL project was a design study aiming at adding an entirely new dimension to the EMFL through the development of novel SC magnets, using high-temperature superconductor (HTS) materials, that go beyond the commercial offer, providing the European high-field user community with much higher superconducting fields.
In this project, the well-established low-temperature superconductor (LTS) magnet technology is boosted above its limit by the use of high-temperature superconductor (HTS) insert magnets, an emerging technology that can work in fields above 25 T. The Metal-as-Insulation (MI) technology, using no insulation but a metallic tape co-wound with the bare HTS tape, enables a self-protection of the HTS coil by allowing the electrical bypass of defects as well as better mechanical performances in a very compact winding.
The project focused on very precise and challenging targets, the design and implementation of a 32+ T and a 40+ T all-superconducting user magnets within EMFL, combining either a single stack of HTS pancakes with a 19 T/150 mm LTS magnet or two nested HTS coils with a 15 T/ 250 mm LTS magnet. While offering different compromises to comply with the EMFL user needs (peak field, experimental available volume, homogeneity to name a few …) depending on their specialties and their working environment, they brought possibilities of long experiments in a low noise environment at high field currently impossible in existing magnets (field limited in SC magnet while too expensive and noisy in resistive one).
The SuperEMFL project was a design study aiming at adding an entirely new dimension to the EMFL through the development of novel SC magnets, using high-temperature superconductor (HTS) materials, that go beyond the commercial offer, providing the European high-field user community with much higher superconducting fields.
In this project, the well-established low-temperature superconductor (LTS) magnet technology is boosted above its limit by the use of high-temperature superconductor (HTS) insert magnets, an emerging technology that can work in fields above 25 T. The Metal-as-Insulation (MI) technology, using no insulation but a metallic tape co-wound with the bare HTS tape, enables a self-protection of the HTS coil by allowing the electrical bypass of defects as well as better mechanical performances in a very compact winding.
The project focused on very precise and challenging targets, the design and implementation of a 32+ T and a 40+ T all-superconducting user magnets within EMFL, combining either a single stack of HTS pancakes with a 19 T/150 mm LTS magnet or two nested HTS coils with a 15 T/ 250 mm LTS magnet. While offering different compromises to comply with the EMFL user needs (peak field, experimental available volume, homogeneity to name a few …) depending on their specialties and their working environment, they brought possibilities of long experiments in a low noise environment at high field currently impossible in existing magnets (field limited in SC magnet while too expensive and noisy in resistive one).
The work performed during this project covered technical issues starting from the HTS tapes, their windings, to the HTS insert design, its coupling to an LTS magnet, to finally assess the concept of an all-SC EMFL user magnet. It also covered the essential underpinning elements to leverage our design effort ultimately as a major upgrade of the EMFL facilities as the identification of the user needs, cost estimates, possible funding schemes, scenarios for their implementation in relationship with the relevant scientific cases.
Tapes from several suppliers were characterized. The critical current Ic vs. the magnetic field and its orientation is a prominent parameter in the design and dimensioning of the HTS insert as well as the turn-to-turn resistance and the degradation of Ic by strain. Other practical properties such as the delamination strength, joint resistivity and regularity of the winding were also considered to validate a tape. The final choice was a newly developed HTS tape by THEVA with an enhancement of the critical current at low temperature and high magnetic field thanks to artificial pinning. Test coils consisting of an assembly of two double HTS pancakes (named 2 DP coil) were fabricated for testing under high magnetic field close to the foreseen operating condition.
A set of simulation tools has been specifically developed, implemented and bench-marked. Designs have been then carried out, targeting 32 and 40 T, as a set of several HTS insert showing the possibility to prioritize homogeneity, peak field or bore size according to the user requirements. 40 T can be reached with a single stack of pancakes but at the sake of a narrower central space. Only a design with nested coils enables to maximize the space for experiment and to reduce constrains. A simple version was proposed to be fabricated and tested in a large bore resistive magnet as a proof of concept.
The interaction of LTS/HTS parts during a quench and the protection scheme were investigated showing the need for a mechanical reinforcement of the LTS outsert to accommodate the potential large axial forces that may be produced by a quench of the HTS insert.
The interfacing of an HTS insert within an LTS magnet was developed, providing de facto a test bench. A series of quench-test measurements using a first 2DP coil up to 19 T, provided valuable information about the HTS/LTS coupling. Closer to ultimate limits, a second 2DP even quenched at 22.6 T and triggered a quench of the LTS system at 17 T, i.e. at an inductively stored energy of ~ 5 MJ, with no damage for either coils.
Several experiments performed to test a variable temperature insert and its sample environment in such LTS/HTS configuration and a first scientific pilot experiment finalized its assessment as a user magnet.
A user survey and a subsequent workshop showed a strong interest and support of our community with a clear idea of what can be expected and done. Further workshops with other facilities were conducted for dissemination towards other communities such as neutrons, high-power lasers, far-infrared free electron lasers, XFELs and synchrotrons.
A facilities inventory was conducted for defining the functional requirements for the implementation of all-superconducting user magnets in an EMFL facility and realistically estimating their implementation costs. CNRS has already obtained a national funding to fabricate a prototype whereas HZDR may also fund an HTS insert so that two prototypes may exist in 2027 in Europe.
Tapes from several suppliers were characterized. The critical current Ic vs. the magnetic field and its orientation is a prominent parameter in the design and dimensioning of the HTS insert as well as the turn-to-turn resistance and the degradation of Ic by strain. Other practical properties such as the delamination strength, joint resistivity and regularity of the winding were also considered to validate a tape. The final choice was a newly developed HTS tape by THEVA with an enhancement of the critical current at low temperature and high magnetic field thanks to artificial pinning. Test coils consisting of an assembly of two double HTS pancakes (named 2 DP coil) were fabricated for testing under high magnetic field close to the foreseen operating condition.
A set of simulation tools has been specifically developed, implemented and bench-marked. Designs have been then carried out, targeting 32 and 40 T, as a set of several HTS insert showing the possibility to prioritize homogeneity, peak field or bore size according to the user requirements. 40 T can be reached with a single stack of pancakes but at the sake of a narrower central space. Only a design with nested coils enables to maximize the space for experiment and to reduce constrains. A simple version was proposed to be fabricated and tested in a large bore resistive magnet as a proof of concept.
The interaction of LTS/HTS parts during a quench and the protection scheme were investigated showing the need for a mechanical reinforcement of the LTS outsert to accommodate the potential large axial forces that may be produced by a quench of the HTS insert.
The interfacing of an HTS insert within an LTS magnet was developed, providing de facto a test bench. A series of quench-test measurements using a first 2DP coil up to 19 T, provided valuable information about the HTS/LTS coupling. Closer to ultimate limits, a second 2DP even quenched at 22.6 T and triggered a quench of the LTS system at 17 T, i.e. at an inductively stored energy of ~ 5 MJ, with no damage for either coils.
Several experiments performed to test a variable temperature insert and its sample environment in such LTS/HTS configuration and a first scientific pilot experiment finalized its assessment as a user magnet.
A user survey and a subsequent workshop showed a strong interest and support of our community with a clear idea of what can be expected and done. Further workshops with other facilities were conducted for dissemination towards other communities such as neutrons, high-power lasers, far-infrared free electron lasers, XFELs and synchrotrons.
A facilities inventory was conducted for defining the functional requirements for the implementation of all-superconducting user magnets in an EMFL facility and realistically estimating their implementation costs. CNRS has already obtained a national funding to fabricate a prototype whereas HZDR may also fund an HTS insert so that two prototypes may exist in 2027 in Europe.
The SuperEMFL project has generated specific know-how, models, the design of 32+ and 40+ T all-superconducting user magnets (TRL 7) and a scenario for implementing such equipment and its derivatives within EMFL as main outcomes.
Besides making high-fields more widely available, the use of HTS inserts introduces new experimental possibilities, in particular long duration and very low noise experiments. The large resulting reduction of operating costs for high field experiments will also considerably increase the EMFL capacity to host user experiments. The improvement of the EMFL environmental impact as well as the optimization of resources and energy are some major benefits of the project.
The development of the HTS technology is now widely competitive with projects at 40 T in Europe, the USA and China. We are reaching other communities beyond EMFL through workshops and conferences, which show their strong interest by submitting their own projects to leverage the HTS technology, e.g. neutron beamline facilities, CERN with its Muon Collider project and the fusion community.
The innovation impacts are going beyond the current limit of commercial superconducting fields, to give the industrial partners a competitive advantage, understanding and modeling the quench events in HTS magnets and opening the high magnetic fields as a research tool to the bio- and life sciences. This project is as a showcase for OI LTS outsert and for THEVA tapes.
Several PhD students and post-doctoral fellows have been trained throughout SuperEMFL, increasing their skills and value on the labor market, but also helping to prepare a future generation for HTS technology that will allow Europe to play an important role in this strategic technology. Currently, the fusion start-ups and technical cryogenics companies are fighting to hire skilled manpower.
Besides making high-fields more widely available, the use of HTS inserts introduces new experimental possibilities, in particular long duration and very low noise experiments. The large resulting reduction of operating costs for high field experiments will also considerably increase the EMFL capacity to host user experiments. The improvement of the EMFL environmental impact as well as the optimization of resources and energy are some major benefits of the project.
The development of the HTS technology is now widely competitive with projects at 40 T in Europe, the USA and China. We are reaching other communities beyond EMFL through workshops and conferences, which show their strong interest by submitting their own projects to leverage the HTS technology, e.g. neutron beamline facilities, CERN with its Muon Collider project and the fusion community.
The innovation impacts are going beyond the current limit of commercial superconducting fields, to give the industrial partners a competitive advantage, understanding and modeling the quench events in HTS magnets and opening the high magnetic fields as a research tool to the bio- and life sciences. This project is as a showcase for OI LTS outsert and for THEVA tapes.
Several PhD students and post-doctoral fellows have been trained throughout SuperEMFL, increasing their skills and value on the labor market, but also helping to prepare a future generation for HTS technology that will allow Europe to play an important role in this strategic technology. Currently, the fusion start-ups and technical cryogenics companies are fighting to hire skilled manpower.