SWLS: the superconducting magnet designed and built at CNPEM

The Superconducting Wavelength Shifter will be installed at Sirius and will generate synchrotron light for the future Sussuarana beamline

The beamlines currently in operation at Sirius already enable investigations ranging from proteins and advanced materials to fossils and archaeological heritage. However, there are areas of research that require more energetic X-rays, which are essential for studying dense materials or heavy elements. To make this type of experiment possible in Brazil, Sirius needs a solution that is unprecedented in the country.

The Superconducting Wavelength Shifter, or simply SWLS, is a superconducting magnet that will be installed in the Sirius storage ring. It will create an extremely energetic X-ray beam, capable of exceeding 150 keV, and will enable the implementation and operation of Sussuarana, a new beamline dedicated to studies in materials science, metallurgy, and engineering applications

This is the first time Brazil is designing and manufacturing a superconducting magnet for a fourth-generation accelerator. The development brings together engineers, physicists, and technicians from the CNPEM’s Technology Unit (DAT) and represents a milestone in the country’s technological sovereignty in a field dominated by only a few nations.

What is the purpose of the SWLS?

Sirius is a large-scale facility capable of producing electromagnetic radiation in a controlled manner, known as synchrotron light. This radiation is used to investigate the composition and structure of matter in its many forms, with applications in virtually all areas of knowledge. To fulfill this purpose, the Sirius accelerators keep electrons circulating in stable orbits and traveling at relativistic speeds. And whenever these electrons are deflected by magnetic fields and forced to follow a curved path, they emit synchrotron light.

In some sections of the ring, so-called insertion devices are installed—magnets that produce intense and highly controlled magnetic fields to manipulate the trajectory of electrons in the accelerator in order to generate high-intensity synchrotron light with specific energy or polarization characteristics.

The SWLS will be one of these devices, but with a unique feature: it will use superconducting coils cooled to temperatures below 5 Kelvin (approximately –268 °C) to generate a magnetic field greater than 6 Teslas, more than twice as strong as the most powerful magnets currently in operation at Sirius. Such an intense field causes the electrons to emit much more energetic and penetrating radiation, ideal for studying very dense materials, which is especially interesting for areas such as metallurgy.

Insertion devices such as the SWLS cannot disturb the quality of the electron beam circulating in the accelerator—they must be “transparent” to the rest of the machine. To achieve this, the SWLS needs to create a very narrow and well-controlled magnetic field, acting within a confined region.

Superconducting technology designed in Brazil

The core of the SWLS is formed by three pairs of magnetic poles, each with coils made from niobium-titanium (NbTi) wire, the same material used in components of large accelerators such as the Large Hadron Collider (LHC) in Switzerland. The development of CNPEM’s capabilities for the design and construction of the superconducting magnet began in 2021, in partnership with the European Organization for Nuclear Research (CERN), under a CNPEM/CERN cooperation agreement signed in 2020.

Superconducting materials are capable of carrying continuous electric current without any losses—something that only occurs when they remain at extremely low temperatures. To reach this operating regime, the magnet will be housed inside a cryostat and cooling will be provided by four cryocoolers—mechanical refrigerators capable of continuously removing heat and keeping the coils cold while the accelerators are in operation. An important characteristic of this type of operation is the absence of liquid helium consumption, which reduces the operating cost of the device.

Keeping a superconductor stable is not a simple task. If any point of the component heats up too much (above 6 Kelvin), the material loses its superconductivity, leading to what is known as a quench—a sudden transition in which the material returns to behaving like a normal conductor. When this happens, the current that previously flowed without losses begins to generate heat rapidly, which can cause damage to components. To prevent this, the SWLS is equipped with advanced electronic systems capable of detecting anomalies and diverting the electrical energy to special resistors.

The manufacturing of the SWLS superconducting coils was carried out at CNPEM itself, using precision engineering processes comparable to those adopted in the world’s leading laboratories. The niobium-titanium wire is carefully wound in layers, impregnated with special resins, and cured to form a rigid and stable block. Each coil is then tested under cryogenic conditions to verify its performance before integration into the final assembly. Mastery of the entire process, from conception to commissioning of the components, consolidates national expertise in advanced technologies such as cryogenics, applied superconductivity, and high-sensitivity instrumentation.

The SWLS will be installed at Sirius to serve the Sussuarana beamline, which is expected to operate in the highest energy range of the complex. The new beamline will enable experimental techniques capable of penetrating thick samples and complex metallic structures, expanding analytical potential for research in metallurgy, structural engineering, geosciences, energy, and advanced materials. With it, Brazilian and international researchers will have access to a set of capabilities previously unavailable in Latin America.