Energy: New optics technology opens door to high-resolution atomic-level hard X-ray studies

An international collaboration involving two U.S. Department of Energy national laboratories has demonstrated a way to reach dramatically smaller focal sizes for hard X-rays, opening the door to research with hard X-rays at atomic-scale.

Argonne, Il, June 13, 2015.- For the first time, the full performance at wavelength of a wedged MLL has been characterized and was found to agree well with calculations. An improved efficiency due to wedging was verified together with a measured focus of 26 nm. Verification of the expected improvement in efficiency arising from the wedging constitutes proof of principle that wedging is a viable technology, thereby constituting a significant advancement toward a new frontier in X-ray nanofocusing.

The ability to study materials, environmental, and biological systems at the atomic level with high efficiency is a current roadblock to solving many of today’s greatest scientific challenges in energy, health, security and the environment. Currently, optical efficiency drops dramatically for studies on areas smaller than 10 nm.

This new lens design will make small spot sizes of below 10 nm routine. Coupled with the unique properties of hard x-rays, namely penetration of complex environments and operation in electric and magnetic fields, such optics will enable highest-resolution imaging of systems under in-situ and in-operando conditions, such as operating batteries and catalysts. It could enable the manipulation of the inner workings of matter to understand, engineer, or eliminate defects, improve manufacturing and help develop therapies for disease.The need for this optics technology will grow with the construction of the next-generation of light sources, including the proposed upgraded Advanced Photon Source at Argonne National Laboratory. New synchrotron light sources using multi-bend achromat technology and X-ray Free Electron Lasers create much brighter X-rays with higher fluxes. Wedged MLLs are expected to enable the maximization of this technology at the atomic scale.

The design recipe and process for creating this next-generation of optics lens is outlined in the April issue of the journal Optics Express in the article “Achieving hard X-ray Nano focusing using a wedged multilayer Laue lens.”

“This has been a highly collaborative effort between two U.S. Department of Energy national laboratories to make these lens,” said Xiaojing Huang, lead author and physicist at the National Synchrotron Light Source II at Brookhaven National Laboratory.

Currently, two types of diffractive X-ray optics tools are used: traditional Fresnel zone plates made with lithography-based fabrication processes, and flat-zone MLLs. The initial tests on the first iteration of the new wedged MLL lens design demonstrated a factor of three improvement in overall efficiency at low energies over zone plates and a factor of five improvement in peak efficiency over flat-zone MLLs. The technology promises to work even better at high energies where an order of magnitude improvement is expected over zone plates, and high resolution focusing in areas now out of reach will be enabled. The iterative design process of MLLlens requires three to four designs before the parameters are optimized, and the lens tested in this work was only the first iteration — a proof of concept. Within the year, the team expects to complete the iterative fabrication process and produce a lens capable of spatial resolution below 10 nm, beyond what is achievable even by flat-zone MLLs.

“What is key is the huge leap in efficiency of 25 to 30 percent compared to zone plates at low-energies and the potential ability to reach 90 percent efficiency at 80 keV compared to the maximum possible today of a few percent efficiency with zone plates,” said Ray Conley, an optics fabrication leader at the APS, who conceived of the new design eight years ago.

The lenses were made by researchers from APS and NSLS II at BNL and the Center for Functional Nanomaterials at Brookhaven. Testing was done at the APS beamlines 1-BM-B and 34-ID-C at Argonne with the help of researchers from the London Centre for Nanotechnology and the UK Research Complex at Harwell, Didcot, Oxfordshire. Efficiencies were measured at beamline 1-BM, and the focus size was measured at beamline 34-ID-C. The research was funded by the U.S. Department of Energy, Office of Basic Energy Sciences and the National Science Foundation.

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