Julio Lucas

The European I.FAST project’s Work Package 8 (WP8) initiative focuses on advancing Canted Cosine Theta (CCT) magnet technology using High-Temperature Superconductors (HTS). These magnets aim to revolutionize synchrotron and gantry designs by reducing their size and cost, offering transformative potential for research and hadron therapy. HTS materials enable higher magnetic fields and smaller cryogenic systems compared to Low-Temperature Superconductors (LTS). However, challenges such as cable production, magnet design, and cost-efficiency must be addressed. This work presents the design of a straight HTS CCT magnet capable of achieving a central dipole field of 4 T at an operating temperature of 20 K, using a cable configuration composed of two HTS tapes. A ramp rate of 0.4 T/s is targeted, with a lower initial ramp rate of 0.15–0.2 T/s deemed acceptable for early-stage development. The magnetic design was optimized to ensure high field quality under operational conditions. Heat extraction is managed through a closed-loop cooling system, with 20 K-helium gas flowing through channels digged directly in the body of the magnet. Thermal simulations demonstrate the effectiveness of this cooling approach, ensuring operational stability. Additionally, the paper highlights key assembly procedures and experimental tests conducted for qualifying critical fabrication steps, including cabling and winding. Results from these tests confirm the reliability and robustness of the developed methods, flooring the way for future HTS CCT magnet advancements. The progress presented here represents a significant step toward compact and efficient superconducting magnets, aligning with the project’s goal of fostering innovative solutions for next-generation synchrotrons and gantries.

The European project IFAST's WP8 Innovative Superconducting Magnets aims to develop the technology of Canted Cosine Theta (CCT) magnets wound with High-Temperature Superconductors (HTS). Superconducting magnets could lower the size and cost of synchrotrons and gantries for research and hadron therapy. HTS materials can lead to higher magnetic fields with smaller cryogenic systems than LTS. However, they pose challenges in cable production schemes, magnet design, and cost. The project's final goal is to design a straight CCT-layout magnet with a central dipole field of 4 T, and a ramp rate of 0.4 T/s, but a lower ramp rate of 0.15–0.2 T/s is acceptable for the first step. The paper presents a preliminary design, discussing in particular the protection scheme with the magnet protection solutions for the conductor: one with two and the other with four HTS tapes. Both options generate 4 T of dipole field without an Iron shell, with at least 10 K of margin at an operational temperature of 20 K. To meet the time and budget constraints of the project, a simple cable based on a co-winding of commercial REBCO tapes is proposed. Protection is the most challenging aspect of the design and an adiabatic quench analysis has been used to determine the required thickness of copper stabilizer tapes to mitigate the risk of damaging the magnet during a quench. Finally, the paper evaluates ac and radial current losses during the magnet cycles, discussing the heat distribution and possible solutions for heat extraction.

The Super FRS is a two-stage in flight separator to be built next to the site of GSI, Darmstadt, Germany as part of FAIR (Facility for Anti-proton and Ion Research). Its purpose is to create and separate rare isotope beams and to enable access for very short-lived nuclei. Due to its three branches, a wide variety of experiments can be carried out in frame of the NUSTAR collaboration. Due to the large acceptance needed, the magnets of the Super-FRS have to have a large aperture and therefore only a superconducting solution is feasible. The dipole magnets are of superferric design in which the magnetic field is produced by superconducting coils and shaped by the iron yoke. This warm yoke weighs about 50 tons and stays at room temperature; the cryostat with the superconducting coils is embedded into the yoke. The conceptual design of the dipole was developed by CEA, the manufacturing is done by Elytt Energy (Spain), testing takes place at a dedicated test facility at CERN (Switzerland) by a GSI-team in frame of a collaboration contract. In this work we detail the main design features, the production of the first magnets and their testing results.

MCBXF magnets are nested orbit combined correctors for the upgrade of the LHC. Two prototypes and the first series magnet were manufactured at CIEMAT and assembled at CERN, in the framework of the HL-LHC project. A fine tuning of the inner dipole design was introduced in the first series magnet to improve the mechanical support at the inner dipole coil ends, with a significant performance improvement. The contract to supply the rest of the series magnets, 6 long (MCBXFA) and 11 short (MCBXFB) magnets, has been awarded to the company Elytt Energy. This paper depicts the manufacturing and powering test results of the first MCBXFB magnet produced in Elytt Energy. In order to mitigate risks prior to the assembly of this magnet, a new reassembly of the second prototype magnet with shorter inner coils, according to the above-mentioned fine tuning, has been tested. The results of this powering test are also detailed.

Fusion for Energy (F4E), the European Domestic Agency for the International Thermonuclear Experimental Reactor (ITER), is responsible for the supply of 5 out of the 6 Poloidal Field (PF) Coils: PF2-PF6. One coil, PF1, is being manufactured by the Russian Federation Domestic Agency (RFDA). While the 10 m diameter PF6 was manufactured by the Institute of Plasma Physics Chinese Academy of Sciences (ASIPP) and tested in the cold test facility at Cadarache under a collaboration agreement with F4E; coils PF2-PF5 are currently being manufactured on site, close to the Tokamak building, their size ranging from 17 to 24 m diameter and weights from 200 to 400 T. This article describes the final acceptance tests performed on the coils PF5 and PF6, the testing setup, paying special attention to the tests performed before, after and during the cool-down at 80 K. The tests cover a wide range of aspects of the operation at cryogenic temperatures: ranging from the high voltage electrical insulation performance during the potential fault conditions during plasma operation, leak tightness under vacuum and pressure drop behavior of its hydraulic system during operation with forced flow helium. In addition, we will briefly introduce the results for the current center line (CCL) calculation obtained for PF5 and PF6.

Next generation ion therapy magnets both for gantry and for accelerator (synchrotron) are under investigation in a recently launched European collaboration that, in the frame of the European H2020 HITRI plus and I.FAST programmes, has obtained some funding for work packages on superconducting magnets. Design and technology of superconducting magnets will be developed for ion therapy synchrotron and -especially- gantry, taking as reference beams of 430 MeV/nucleon ions (C-ions) with 10 ¹⁰ ions/pulse. The magnets are about 60–90 mm diameter, 4 to 5 T peak field with a field change of about 0.3 T/s and good field quality. The paper will illustrate the organization of the collaboration and the technical program. Various superconductor options (LTS, MgB ₂ or HTS) and different magnet shapes, like classical CosTheta or innovative Canted CosTheta (CCT), with curved multifunction (dipole and quadrupole), are under evaluation, CCT being the baseline. These studies should provide design inputs for a new superconducting gantry design for existing facilities and, on a longer time scale, for a brand-new hadron therapy centre to be placed in the South East Europe (SEEIIST project).

It has long been known that the ellipse normally used to model the phase space extension of a beam in linear dynamics may be represented by a complex number which can be interpreted similarly to a complex impedance in electrical circuits, so that classical electrical methods might be used for the design of such beam transport lines. However, this method has never been fully developed, and only the transport transformation of single particular elements, like drift spaces or quadrupoles, has been presented in the past. In this paper, we complete the complex formalism of linear beam dynamics by obtaining a general differential equation and solving it, to show that the general transformation of a linear beam line is a complex Moebius transformation. This result opens the possibility of studying the effect of the beam line on complete regions of the complex plane and not only on a single point. Taking advantage of this capability of the formalism, we also obtain an important result in the theory of the transport through a periodic line, proving that the invariant points of the transformation are only a special case of a more general structure of the solution, which are the invariant circles of the one-period transformation. Among other advantages, this provides a new description of the betatron functions beating in case of a mismatched injection in a circular accelerator.

The last acceleration stage of the deuteron beam of the LIPAc linear accelerator is provided by eight superconducting cavities in a cryomodule (SRF Linac). Each cavity needs a magnet package, which consists of a solenoid for beam focusing and two vertical and horizontal dipole correctors for beam steering. The superconducting coils are fed by vapour cooled current leads. The beam position monitor is part of the magnet helium vessel. The series fabrication of eight sets of magnets and current leads has been performed by Elytt Energy, under CIEMAT follow-up. This paper describes the final design used for production, the main challenges addressed during fabrication, together with the quality control procedure, acceptance tests and qualification criteria to validate both the magnets and current leads. Currently some activities are being performed in the magnet helium vessels for improvement of surfaces for handling inside the clean room and reducing the risk of presence of particulate contaminations in the beam tube.

It has long been known that the ellipse normally used to model the phase space extension of a beam in linear dynamics may be represented by a complex number which can be interpreted similarly to a complex impedance in electrical circuits, so that classical electrical methods might be used for the design of such beam transport lines. However, this method has never been fully developed, and only the transport transformation of single particular elements, like drift spaces or quadrupoles, has been presented in the past. In this paper, we complete the complex formalism of linear beam dynamics by obtaining a general differential equation and solving it, to show that the general transformation of a linear beam line is a complex Moebius transformation. This result opens the possibility of studying the effect of the beam line on complete regions of the complex plane and not only on a single point. Taking advantage of this capability of the formalism, we also obtain an important result in the theory of the transport through a periodic line, proving that the invariant points of the transformation are only a special case of a more general structure of the solution, which are the invariant circles of the one-period transformation. Among other advantages, this provides a new description of the betatron functions beating in case of a mismatched injection in a circular accelerator.

In many micro- and nano-scale technological applications high sensitivity displacement sensors are needed, especially in ultraprecision metrology and manufacturing. In this work a new way of sensing displacement based on radio frequency resonant cavities is presented and experimentally demonstrated using a first laboratory prototype. The principle of operation of the new transducer is summarized and tested. Furthermore, an electronic interface that can be used together with the displacement transducer is designed and proved. It has been experimentally demonstrated that very high and linear sensitivity characteristic curves, in the range of some kHz/nm; are easily obtainable using this kind of transducer when it is combined with a laboratory network analyzer. In order to replace a network analyzer and provide a more affordable, self-contained, compact solution, an electronic interface has been designed, preserving as much as possible the excellent performance of the transducer, and turning it into a true standalone positioning sensor. The results obtained using the transducer together with a first prototype of the electronic interface built with cheap discrete elements show that positioning accuracies in the micrometer range are obtainable using this cost-effective solution. Better accuracies would also be attainable but using more involved and costly electronics interfaces.