Figure. 1. Groundbreaking X-Ray Lens Provides Incredible Glimpse into the Nanoworld

Paul Scherrer Institute scientists have developed a groundbreaking achromatic lens for X-rays. This allows the X-ray beams to be accurately focused on a single point even if they have different wavelengths. The new lens will make it much easier to study nanostructures using X-rays, according to a paper just published by the researchers in the scientific journal Nature Communications.

Achromatic lenses are essential for producing sharp images in photography and optical microscopes. They ensure that different colors – i.e. light of different wavelengths – have a common focal point. To date, however, achromatic lenses have not been available for X-rays, so that high-resolution X-ray microscopy has only been possible with monochromatic X-rays. In practice, this means that all other wavelengths have to be filtered out of the X-ray beam spectrum and hence only a small portion of the light can effectively be used, resulting in a relatively inefficient image capturing process.[1]

A team of PSI scientists have now solved this problem by successfully developing an achromatic X-ray lens for X-rays. Since X-rays can reveal much smaller structures than visible light, the innovative lens will particularly benefit R&D work in sectors such as microchips, batteries and materials science, among others.

More complex than in the visible range

The fact that it has taken so long to develop an achromat for X-rays may come as a surprise: achromats for visible light have been around for over 200 years. These usually consist of two different materials. The light penetrates the first material and breaks down into its spectral colors – similar to passing through a conventional glass prism. It then goes through a second material to reverse this effect. In physics, the process of separating different wavelengths is called “dispersion”.

“However, this basic principle applied in the visible range does not work in the X-ray range,” explains the physicist Christian David, head of the X-ray optics and applications research group at the Laboratory for X-ray Nanosciences and Technologies at PSI. “For X-rays, there is no pair of materials in which the optical properties differ enough over a wide range of wavelengths for one material to balance the effects of the other. In other words: The scattering of the materials in the X-ray range is too similar.”

Two principles instead of two materials

“The trick was realizing that we could position a second refractive lens in front of our diffractive lens,” says Adam Kubec, lead author of the new study. Until recently, Kubec was a researcher in Christian David’s group and now works at XRnanotech, a spin-off that emerged from PSI’s research in X-ray optics.

“PSI has been a global leader in the manufacture of X-ray lenses for many years,” says David. “We supply special lenses, so-called Fresnel zone plates, for X-ray microscopy at synchrotron light sources worldwide.” [2]

SLS X-ray beam used for testing

To characterise their achromatic X-ray lens, scientists used an X-ray beamline at SLS. One of the methods employed there is a highly developed X-ray microscopy technique called ptychography. "This technique is normally used to examine an unknown sample," says the study's second author, Marie-Christine Zdora, a physicist working in Christian David's research group and an expert in X-ray imaging. "We on the other hand used ptychography to characterise the X-ray beam and thus our achromatic lens." This enabled the scientists to precisely detect the location of the X-ray focal point at different wavelengths.

They additionally tested the new lens using a method where the sample is moved through the focus of the X-ray beam in small raster steps. When the wavelength of the X-ray beam is changed, the images produced with a conventional X-ray lens become very blurred. This, however, does not happen when using the new achromatic lens. "When we eventually got a sharp image of the test sample over a broad range of wave.[3]

References:

1. https://www.gartner.com/en/information-technology/glossary/hyperautomation
2. https://www.automationanywhere.com/rpa/hyperautomation
3. https://www.uipath.com/rpa/hyperautomation
4. https://www.ibm.com/cloud/learn/hyperautomation

Cite this article:

Nithyasri S (2022), Groundbreaking X-Ray Lens Provides Incredible Glimpse Into the Nanoworld, Anatechmaz, pp. 121