La première lentille à neutrons au monde permet d'accorder une attention particulière aux structures à l'intérieur des matériaux et des objets

Researchers at the Paul Scherrer Institute (PSI) in Switzerland have unveiled the world’s first achromatic neutron lens, marking a major breakthrough in neutron imaging technology. The innovation allows for the creation of sharp, magnified images of internal structures within materials and objects from distances up to several meters, overcoming a long-standing limitation in the field. A test image of a 3-millimeter-wide PSI logo, captured six meters from the detector, demonstrated the lens’s ability to deliver unprecedented clarity. Without the lens, achieving similar resolution would have required placing the object within centimeters, or even millimeters, of the detector. The development, published in Nature Communications, introduces a novel approach to neutron optics. Neutron imaging, commonly conducted at facilities like the Swiss Spallation Neutron Source SINQ, relies on beams of neutrons that pass through materials to reveal their internal composition. Unlike X-rays, which are effective for imaging dense materials, neutrons possess a unique sensitivity to light elements such as hydrogen and lithium. This property makes them particularly valuable for studying complex systems like batteries, polymers, and biological tissues. However, the inherent difficulty in manipulating neutron beams has historically restricted the potential of neutron imaging. One of the primary challenges in neutron imaging stems from the nature of neutron beams themselves. These beams consist of neutrons with varying wavelengths, complicating efforts to focus them effectively. Traditional methods rely on placing samples near detectors to maintain image quality, limiting both the resolution and the types of objects that can be studied. The new lens, designed to address this issue, functions as an achromatic neutron lens. It is capable of focusing a wide range of neutron wavelengths to a single focal point, enabling high-resolution imaging without proximity constraints. “This lack of such a lens has held back neutron imaging for decades,” explains Joan Vila-Comamala, a scientist leading the research team at PSI. “Now that we have it, it becomes possible to follow processes inside equipment such as furnaces, cryostats or pressure cells. It also opens the path to neutron microscopy, making it possible to produce magnified images of an object and reveal more detail.” The lens achieves resolutions below 20 micrometers, allowing for detailed examination of structures that were previously inaccessible. To demonstrate the capabilities of the new lens, the researchers imaged a commercial lithium-ion battery. By positioning the battery six meters away from the detector, they successfully magnified the layered structure of the wound electrode assembly by a factor of seven. This achievement highlights the potential of the technology to enable real-time observation of internal material behavior under operational conditions. Such capability could prove invaluable in fields ranging from energy storage to materials science. Mano Raj Dhanalakshmi Veeraraj, the study’s lead author and a Ph.D. student at PSI, emphasizes that the development represents more than just improved resolution. “This is just the beginning,” he states. “We already see ways to improve the lens. The key point is not simply resolution, but a completely new way of acquiring images.” With this advancement, neutron imaging facilities worldwide stand poised to expand their applications, offering new opportunities for scientific discovery and industrial inspection. The implications of this work extend beyond traditional imaging, potentially transforming how researchers analyze complex systems and monitor dynamic processes in controlled environments. As the technology continues to evolve, the impact of this world-first innovation promises to be profound.