Using only a single-crystal piezoelectric thin wafer of lithium niobate (LN) instead of the usual two-part structure, a group from Nagoya University in Japan has created a deformable mirror that changes X-ray beam size by more than 3,400 times. This improved tuning range enhances both imaging and analysis, especially for the X-rays used in industry.
Their technique is based on LN, a material that has piezoelectricity, meaning that it changes its surface shape in response to voltage. Traditional X-ray mirrors are rigid and resistant to being deformed, making it difficult to adapt them to changing experimental conditions in real time, but the new technique can significantly change beam size, making it useful for a range of situations encountered in industry.
"Our technique significantly changes beam size, making it possible to observe samples in various ways," Takato Inoue from the Graduate School of Engineering Department of Materials Physics explained. "We achieved a 3,400-times larger tuning range, which lets users first perform a wide-field overview of a sample and then zoom in on specific regions of interest, massively streamlining workflows."
By changing the shape of the mirror, the operator can fine tune the X-ray to capture an overview of the material or focus on specific areas of interest. However, this is difficult in practice because the mirror often requires two parts to control the size of the beam, limiting its thinness. Instead, making a mirror with a single crystal would allow researchers to maintain thinness and optimize performance.
To make the single-crystal mirror, the researchers focused on LN. When LN is exposed to high levels of heat in a furnace, its polarization structure—a property that dictates how much it deforms—changes. Using this property, they formed the bimorph structure used in mirrors without the need for chemical bonding, massively reducing the thickness of the mirror.
"We developed a mirror with a thickness of only 0.5 mm. This achievement is expected to greatly increase the degree of freedom for all experiments using synchrotron radiation X-rays," Inoue said. "These properties allow it to be used for X-rays as well as in other fields such as high-power lasers used in industry."
The research results were published in the journal Scientific Reports. The research was supported by JST "Emergent Research Support Program (Development of Flexible and Ultra-stable X-ray Microscope, JPMJFR222B)" which started in FY2023.
