Construction of combined CCT demonstrator

I.FAST Innovation Fostering in Accelerator Science and Technology Horizon 2020 Research Infrastructures GA n° 101004730 DELIVERABLE REPORT Construction of combined CCT demonstrator DELIVERABLE: D8.4 Document identifier: IFAST-D8.4 Due date of deliverable: End of the Month 42 (delivered on month 54, October 2025) Justification for delay: Change of Responsibility due to the withdrawal of companies Report release date: 28/10/2025 Work package: WP8: Innovative Superconducting Magnets Lead beneficiary: CIEMAT Document status: Final ABSTRACT This report presents the as-built details of the combined Canted Cosine Theta (CCT) magnet demonstrator based on LTS developed within Task 8.4 of WP8 – Innovative Superconducting Magnets in the I.FAST project. The demonstrator is a straight, two-layer combined CCT magnet designed to achieve a central dipole field of 4 T at 4.2 K, using a Nb-Ti 6 strands + 1 copper core strand cable configuration and targeting a ramp rate of 0.4 T/s. The document describes the final design configuration, conductor and joint characteristics, and manufacturing and assembly procedures. CONSTRUCTION OF COMBINED CCT DEMONSTRATOR Deliverable: D8.4 Date: 28/10/2025 Grant Agreement 101004730 PUBLIC 2 / 20 I.FAST Consortium, 2025 For more information on IFAST, its partners and contributors please see https://ifast-project.eu/ This project has received funding from the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 101004730. IFAST began in May 2021 and will run for 4 years. Delivery Slip Name Partner Date Authored by E. De Matteis, J. Munilla, F. Toral INFN, CIEMAT 28/10/2025 Edited by E. De Matteis, J. Munilla INFN, CIEMAT 28/10/2025 Reviewed by D. Barna WIGNER RCP 28/10/2025 Approved by M. Vretenar and L. Celone on behalf of Steering Committee CERN 28/10/2025 CONSTRUCTION OF COMBINED CCT DEMONSTRATOR Deliverable: D8.4 Date: 28/10/2025 Grant Agreement 101004730 PUBLIC 3 / 20 TABLE OF CONTENTS 1. INTRODUCTION ......................................................................................................................................... 5 2. MAGNET DESIGN OVERVIEW ............................................................................................................... 6 A. ELECTROMECHANICAL MODEL ......................................................................................................... 7 3. CONDUCTOR AND SPLICES ................................................................................................................... 9 4. MAGNET FABRICATION AND ASSEMBLY PROCEDURES ........................................................... 11 5. CONCLUSIONS ......................................................................................................................................... 18 6. REFERENCES ............................................................................................................................................ 20 CONSTRUCTION OF COMBINED CCT DEMONSTRATOR Deliverable: D8.4 Date: 28/10/2025 Grant Agreement 101004730 PUBLIC 4 / 20 Executive summary This report presents the design, fabrication, and assembly of the combined function Canted Cosine Theta (CCT) magnet demonstrator based on LTS, developed within Work Package 8 (WP8) of the I.FAST project. The combined-function Canted Cosine Theta (CCT) superconducting magnet demonstrator developed within the I.FAST Work Package 8 represents a major milestone in European superconducting magnet technology. The collaboration has successfully completed a conceptual design into a fully engineered LTS-based demonstrator, validating the CCT concept for combined dipole and quadrupole fields. This achievement showcases Europe’s capacity to design, manufacture, and assemble compact, mechanically robust accelerator magnets through coordinated research and innovation. The project overcame significant engineering challenges, including the precision machining of complex aluminium-bronze mandrels, the manual winding of multi-strand Nb-Ti cables, and the development of reliable low-resistance splices and wax impregnation techniques. Beyond the technical advances, the work illustrates the strength of cross-institutional collaboration and the engagement of European industry in developing specialized superconducting components. The demonstrator stands as a tangible validation of the CCT architecture and a strategic enabler for future high-field superconducting magnets. It consolidates the technological foundation for nextgeneration accelerators and demonstrates the collective capability, innovation, and coordination driving Europe’s leadership in superconducting magnet R&D. The combined CCT demonstrator is now fully assembled and ready for cryogenic qualification, representing a crucial step toward industrializing CCT technology. CONSTRUCTION OF COMBINED CCT DEMONSTRATOR Deliverable: D8.4 Date: 28/10/2025 Grant Agreement 101004730 PUBLIC 5 / 20 1. Introduction Work Package 8 (WP8) – Innovative Superconducting Magnets – of the H2020–EU project I.FAST pursues a dual objective: to strengthen long-term strategic coordination among European laboratories and industries active in superconducting magnet technologies, and to advance the development and application of High-Temperature Superconductor (HTS) technologies for accelerator systems. Within this framework, WP8 aims to establish a permanent European Strategy Group, open to worldwide collaboration, to define a coherent roadmap for HTS magnet development and to promote stronger industrial involvement in the design and fabrication of superconducting magnets. Among the main technological goals of WP8 is the exploration of the Canted Cosine Theta (CCT) magnet concept using HTS conductors. This effort builds upon a preceding phase based on LowTemperature Superconductor (LTS) technology, which served as a learning platform enabling industrial partners to gain practical experience with the CCT architecture. The baseline parameters of the CCT demonstrators were defined in close coordination with the HITRIplus program, which focuses on developing magnet technologies for hadron therapy applications. To facilitate design, fabrication, and testing while maintaining the essential features of a curved accelerator magnet, both the LTS and HTS demonstrators were designed with a straight geometry. Task 8.4, dedicated to the construction of a combined-function CCT magnet demonstrator based on LTS technology, was led by CIEMAT, with the participation of INFN-LASA, WIGNER RCP, and CERN. Within this task, the consortium translated the conceptual design into a fully engineered and fabricated magnet. The demonstrator was designed to generate a central dipole field of 4 T and a quadrupole gradient of 5 T/m at 4.2 K, using a rope-type Nb-Ti cable composed of six superconducting strands twisted around a copper core and insulated with a double polyester braid. The design accommodates a field ramp rate of 0.2–0.4 T/s, addressing challenges related to heat extraction from the superconductor and the Aluminium-Bronze former. The demonstrator provides a platform for testing the combined dipole–quadrupole function of the CCT concept and for validating AC loss models. The work encompassed the preparation of detailed construction drawings, the definition of manufacturing procedures, and the design and fabrication of dedicated tooling and components. Following the completion of the conceptual design and material procurement, the two formers were produced and qualified through dimensional and metrological verification. The final demonstrator was then assembled through two-layer winding, mechanical integration, and electrical qualification tests, carried out at CIEMAT’s facilities with technical coordination and support from INFN-LASA and WIGNER RCP. This report presents the as-built configuration of the combined-function CCT magnet demonstrator. It provides a detailed description of the final design, the conductor and joint characteristics, the manufacturing and assembly procedures, and the main as-built parameters of the magnet. CONSTRUCTION OF COMBINED CCT DEMONSTRATOR Deliverable: D8.4 Date: 28/10/2025 Grant Agreement 101004730 PUBLIC 6 / 20 2. Magnet Design Overview This section provides an overview of the combined-function superconducting magnet based on the Canted Cosine Theta (CCT) geometry, designed to integrate bending and focusing functions within a single magnetic structure. The detailed design and analysis have been presented in previous publications ([1], [2]); the main parameters are summarized here in Table 1 for reference and completeness. The following section summarizes the final electromechanical model of the demonstrator. Table 1. Main Design Parameters of the combined CCT Dipole Magnet: model vs as-built parameters. Parameter Model As-built (without iron yoke) Central field 4 T 2.8 T Quadrupole 5 T/m 3.7 T/m Operating temperature 4.2 K Cable type Rope cable (6 Nb-Ti + 1 Cu core) with polyester braid Rope insulated diameter 3.15 mm Nominal current 1540 A Stack of cables per groove 14 (2 x 7) Magnet aperture 80 mm Magnet length ≃ 1 m Ramp rate (target) 0.4 T/s Number of turns (per layer) 50 Figure 1. 3D model of the combined CCT magnet demonstrator. CONSTRUCTION OF COMBINED CCT DEMONSTRATOR Deliverable: D8.4 Date: 28/10/2025 Grant Agreement 101004730 PUBLIC 7 / 20 a. ELECTROMECHANICAL MODEL The former and coil geometries were modelled to evaluate their mechanical behaviour under all expected operational conditions. Particular attention was devoted to the analysis of stress and displacement distributions both after cooldown to cryogenic temperature and under energized conditions at nominal current. The finite element model was developed in ANSYS, incorporating the complete former geometry, detailed groove profiles, and the wound coils, with frictional contacts defined between the conductor and the former. Figure 2 presents the resulting stress distribution obtained for the energized load step. As anticipated from previous design studies, no significant stress concentrations are observed. This characteristic is intrinsic to stress-managed coils (including the Canted Cosine Theta (CCT) architecture), where each turn of the winding is independently supported by features of the mechanical structure, counteracting the Lorentz forces. This contrasts with the conventional cosinetheta configuration, in which the Lorentz forces accumulate toward the mid-plane of the coil. Figure 2. Stress (up) and displacements (down) of the coils when modelled at cold and energized conditions inside the grooves with frictional contact. Nevertheless, in the CCT configuration, there exists a potential risk of coil deformation if the walls separating the grooves are insufficiently stiff. This stiffness can be reduced when thin wall sections are used or where the effective wall thickness locally decreases due to the spatial twisting of the conductor path. To account for these effects, the complete 3D geometry of the former was modeled to identify both the peak stress and maximum deformation values across the structure. The cool-down analysis was performed first, simulating thermal contraction to the nominal operating temperature. Subsequently, the Lorentz forces acting on each turn were computed using COMSOL Multiphysics and imported into the ANSYS mechanical model as an additional load step, representing CONSTRUCTION OF COMBINED CCT DEMONSTRATOR Deliverable: D8.4 Date: 28/10/2025 Grant Agreement 101004730 PUBLIC 8 / 20 the magnet in its energized state. This combined simulation enabled a comprehensive evaluation of the mechanical integrity of the system under realistic operating conditions. Finally, the impact of the coil displacements on the magnetic field quality was assessed using RAT software. The results, summarized in Figure 3, illustrate the variation of the field multipoles in the deformed geometry compared to the nominal one. The analysis confirms that the mechanical deformation induced by the Lorentz forces and cool-down contraction remains within acceptable limits, ensuring that the field quality of the magnet is not significantly degraded under operating conditions. Figure 3. Top plots: field quality values up to 10th harmonic, evaluated at 2/3 of the aperture, considering the actual displacements when at cold and energized to nominal current. Bottom plots: differences between the undeformed and deformed values. CONSTRUCTION OF COMBINED CCT DEMONSTRATOR Deliverable: D8.4 Date: 28/10/2025 Grant Agreement 101004730 PUBLIC 9 / 20 3. Conductor and Splices The coil conductor used for the combined-function CCT magnet consists of 14 cables connected in series, as illustrated in Figure 4. Each cable is composed of six Nb-Ti strands (with a diameter of 0.82 mm and a Cu:SC ratio of 1.36, containing 3 microns diameter filaments, manufactured by Bruker EAS) twisted around a central copper strand) and insulated with a double polyester braid, which provides enhanced electrical insulation and mechanical protection. The rope was produced by Texcavi srl. and it was fully characterized at INFN-LASA as reported in [3]. This insulation system is particularly important given the complex geometry of the former and the winding grooves, where local stress concentrations or tight curvature could otherwise lead to insulation damage. Figure 4. Final layout of the rope cable made of 6 Nb-Ti strands twisted on a copper core strand and insulated with a double braid of polyester (right). Stack of 14 cables on the former grooves (left). A critical design aspect of the magnet is the implementation of optimized splices, which play a major role in the overall electrical and thermal performance. Since the 14 cables are connected in series, the transport current crosses 13 splices. Each splice introduces a localized resistive path, and consequently a heat load, that must remain within acceptable limits to prevent thermal instabilities. Moreover, the geometrical compactness of the splices is essential to fit within the limited space available in the splice box and to minimize field perturbations. To validate the design and manufacturing process, a splice mockup test was performed. The overall concept was derived from previous experience in similar superconducting splice developments [4], and the main steps are illustrated in Figure 5. The procedure begins with the removal of the cable insulation, after which the individual strands are aligned flat to prepare for soldering. Each cable is then pre-tinned with an eutectic AgSn inside a heated mold (Figure 5.a). The mold, shown before closure in the figure, ensures controlled heating during the process. Once pre-tinning is completed (Figure 5.b), the two cables are positioned inside the mold together with a machined copper plate with a channel for the wires, which provides both mechanical reinforcement and thermal homogeneity for the joint. CONSTRUCTION OF COMBINED CCT DEMONSTRATOR Deliverable: D8.4 Date: 28/10/2025 Grant Agreement 101004730 PUBLIC 16 / 20 Finally, the splices were done and the splice box installed according to the tested procedure already explained. Upper reservoir was finally installed over the top plate shown in Figure 12 (right) to close the mold as shown in Figure 13 (left), the starting point of the impregnation step. Coil impregnation The overall view of the impregnation step is shown at Figure 13 (right). The same structure provides convenient support for the impregnation. The magnet assembly is covered with multilayer insulation. The other systems shown in the Figure are the pumping station (right), and the heating and temperature control system rack (left). The entire mold was leak-tested, and temperature sensors (six in total) were installed also on the outer surfaces of the magnet. Six electrical heaters were installed in between the mold and the insulation. The procedure details for the wax impregnation step were adapted to this specific magnet following previous developments [8] and [9]. The selected wax had a melting temperature of 55ºC, while the temperature setpoint for the heaters during the wax-filling phase was 60ºC. The upper reservoir was designed to keep enough liquid volume of wax to counteract its contraction during the solidification, so the level of melted wax was checked thanks to the translucent pipe in the upper reservoir. Finally, when all the mold is filled with melted wax, the mold was precisely cooled following the state-of-art procedure, from the bottom to the top and from inner to outer radius. This is the best approach to minimize the risk of voids in the impregnated volume, by keeping just one solidification surface moving upwards along the whole process. This is crucial for providing an unblocked path for liquid wax to refill from the upper reservoir to the solidification surface (where the wax contracts during the phase change) to fill any voids. Otherwise, liquid wax volumes could be trapped producing voids upon solidification and contraction. Because of that reason, the solidification step of the impregnation phase is the most critical one. In fact, the short-length mockup magnet made of Cu cables was also tested in advance to gain experience about the procedure. Figure 13. Magnet assembled (left) Wax-impregnation setup of the final demonstrator (right). CONSTRUCTION OF COMBINED CCT DEMONSTRATOR Deliverable: D8.4 Date: 28/10/2025 Grant Agreement 101004730 PUBLIC 17 / 20 Inspection and external supports installation After the impregnation step, the insulation can be dismantled. Additional checks were done at this moment including visual inspection, electrical insulation measurements and wax level at the reservoir once the cover was removed. It was also important to check that no voids were found at the inlet port of the mold (where the liquid wax was injected), no wax at the joints and the outer ports of the upper flange, where the cables are coming out from the mandrel. The excess of wax at the outer surface of the splice box was manually removed. The additional tooling for the impregnation and cooling can be also removed while attached to the supporting structure (Fig. 14, left). Finally, the transportation support was installed (Fig. 14, right). It includes the proper tooling for holding the magnet during a future testing phase, out of the scope of this deliverable (fig. 15). Figure 14. Impregnation tooling being removed from the magnet (left). Manufactured magnet in its holding structure (right). CONSTRUCTION OF COMBINED CCT DEMONSTRATOR Deliverable: D8.4 Date: 28/10/2025 Grant Agreement 101004730 PUBLIC 18 / 20 Figure 15. Combined CCT magnet demonstrator ready for delivery. 5. Conclusions The development of the combined-function Canted Cosine Theta (CCT) superconducting magnet demonstrator within the framework of the I.FAST Work Package 8 marks an important milestone in advancing European competence in superconducting magnet technology. This effort successfully translated a conceptual design—originating from the High-Temperature Superconductor (HTS) research strategy—into a fully engineered and fabricated demonstrator based on Low-Temperature Superconductor (LTS) technology. The project not only validated the CCT concept for combined dipole and quadrupole magnetic functions but also deepened the collective design, manufacturing, and integration capabilities of participating institutions and industrial partners. From a technical perspective, the magnet represents a significant step in the practical realization of compact, efficient, and mechanically stable accelerator magnets. The project overcame key manufacturing challenges, particularly the production of highly complex aluminium-bronze mandrels with three-dimensional winding grooves and thin-wall sections. The successful machining of these components, the precise hand-winding of multi-strand Nb-Ti rope cables, and the implementation of optimized low-resistance splices all demonstrate a high level of engineering excellence. Moreover, the wax-impregnation process, developed and tested through mockups, ensured the mechanical CONSTRUCTION OF COMBINED CCT DEMONSTRATOR Deliverable: D8.4 Date: 28/10/2025 Grant Agreement 101004730 PUBLIC 19 / 20 stability and void-free insulation of the coils (an essential step for reliable operation under cryogenic conditions). Figure 16. Superconducting magnets team at CIEMAT with the CCT demonstrator. The collaborative nature of this work was fundamental to its success. This CCT demonstrator was designed from the very first concept to the manufacturing details, within the framework of the WP8 I.FAST project, which tasks (from 8.1 to 8.4) were led by INFN-LASA, CERN, Wigner and/or CIEMAT. Moreover, it also took advantage of another European Project HITRIPLUS, in which the WP8 was also devoted to design and produce a CCT magnet (in this case a curved one), so natural synergies were found. This integrated approach not only combined diverse expertise across institutions but also strengthened Europe’s capacity to produce complex superconducting systems through joint innovation and knowledge sharing. The development, refinement, and qualification of custom tooling, manufacturing procedures, and quality verification protocols exemplify the cooperative spirit that underpins the I.FAST initiative. This work was also a great opportunity for the involved European companies, even when they are not part of the consortium, because they developed the required processes for manufacturing under the guidance of the I.FAST team. There is no doubt that this experience produced high value know-how in the superconducting magnets field, for example on complex parts manufacturing like the mandrels of the layer jumps. This demonstrator serves as both a technological achievement and a strategic enabler. It offers a concrete validation platform for CCT magnet design principles, enabling reliable benchmarking of mechanical, electrical, and magnetic behavior under realistic operating conditions. Furthermore, it provides a valuable reference for the forthcoming integration of HTS conductors in similar CCT CONSTRUCTION OF COMBINED CCT DEMONSTRATOR Deliverable: D8.4 Date: 28/10/2025 Grant Agreement 101004730 PUBLIC 20 / 20 architectures, paving the way toward future accelerator applications such as those envisioned in the HITRIplus program for hadron therapy. In summary, this project highlights not only the maturation of CCT magnet technology but also the effectiveness of international collaboration in tackling multidisciplinary engineering challenges. The result is a demonstrator that embodies the long-term vision of a coordinated European effort to advance superconducting magnet R&D—bridging design innovation, industrial capability, and scientific excellence. 6. References [1] E. De Matteis, G. Ceruti, S. Mariotto, M. Priolie S. Sorti, “Conceptual Design of combined CCT in LTS”, Zenodo, feb. 2022. doi: 10.5281/zenodo.6389851. [2] F. Toral et al. “Status of Nb-Ti CCT Magnet EU Programs for Hadron Therapy”. IEEE Transactions on Applied Superconductivity, Vol. 34, No. 5, August 2024. [3] E. De Matteis, I.FAST WP8 members, “Characterization of the first length of superconductor for low losses”, Zenodo, gen. 2022. doi: 10.5281/zenodo.5901601. [4] J. Á. García-Matos et al., "Engineering Design and Fabrication of the Nested Orbit Corrector Prototype for HL-LHC," in IEEE Transactions on Applied Superconductivity, vol. 29, no. 5, pp. 1-5, Aug. 2019, Art no. 4002205, doi: 10.1109/TASC.2019.2897233. [5] J. Munilla et al. “Fabrication of a straight canted cosine-theta prototype magnet for hadron therapy”, Sat-Mo-Po.01-05, MT29 conference, https://indico.cern.ch/event/1431972 [6] E. De Matteis et al. “Construction readiness of combined CCT demonstrator”, Zenodo doi: 10.5281/zenodo.11125447 [7] E. De Matteis et al. “Construction of the combined formers for CCT winding”, Zenodo doi: 10.5281/zenodo.17135549 [8] D. Barna et al. “Training-free performance of the wax-impregnated SuShi septum magnet”. 2024 Supercond. Sci. Technol. 37 045006 [9] D. Arbelaez et al. “Training-free demonstration of a 5.4 T Nb3Sn Canted–Cosine–Theta accelerator dipole impregnated with paraffin wax” 2024 Supercond. Sci. Technol. 37 065015