Visit to Argonne National Laboratory -1/3-
Commercial Applications of High-Energy Physics:
X-Ray Lensing
Overview
Large-scale research facilities such as X-ray synchrotron facilities and X-ray free-electron laser (FEL) are important investments that have a very significant scientific and technological impact. Today, there are currently over 35 facilities around the world with nearly 900 beamlines and experimental stations. These are powerful tools that allow researchers to probe materials down to molecular and atomic levels and to reactions that take place very quickly. These extraordinary facilities enable, scientists and engineers to achieve transformative technology such as creating next-generation battery materials, developing life-saving drugs, fabricating strong building materials, and transforming information systems. The economic benefits of these facilities leads to intense global competition in this market.
Figure 1: (Left) As of 2021, there are over 35 synchrotron facilities existent or planned worldwide with five in the US. (Right): The total number of synchrotron beamlines has nearly doubled in the past two decades.
The ability to use these ultrabright and coherent X-ray sources is limited by the ability to focus, monochromate, and manipulate X-rays with appropriate optics. X-ray optics technology usually lags source technology and thus limits use of even today’s X-ray sources. For instance, high-precision and coherence-preserving mirrors are critical components of almost every beamline. However, mirror perfection is limited by manufacturing precision, mechanical mounting, and thermal management. The most advanced mirror technologies are currently in Japan. Refractive optics such as compound refractive lenses (CRLs) are another example. Their strength as compact, in-line, stable, easily aligned, and coherence-preserving optics have been recognized worldwide. As a result, most beamlines have CRLs equipped as standard components for experiments such as X-ray photon correlation spectroscopy, X-ray microscope, high-energy imaging/diffraction, etc. The demand of the CRLs is skyrocketing with the prosperous growth of next-generation synchrotron sources.
At Argonne National Laboratory, scientists have invented a method of fabricating high-quality polymer-based refractive X-ray optics with a recently developed single-photon polymerization lithography technique. These X-ray optics have been demonstrated to exhibit extraordinary performance in focusing coherent X-rays and preserving X-ray wavefronts and thus will find great potential in diffraction-limiting applications. X-ray optics that function on the principle of reflection or diffraction, such as Kirkpatrick-Baez (KB) mirrors, Bragg crystal monochromators, multilayer Laue lenses, Fresnel zone plates etc., can be fabricated with the needed precision to meet certain diffraction-limiting requirements for focusing and beam collimating purposes. At the Advanced Photon Source (APS) at Argonne National Laboratory one imaging beamline requires two transfocators (a device comprising multiple sets of CRLs) and a bendable KB mirror system are equipped in order to provide focusing schemes for energy-tunable coherent experiments. Now consider that are about 60 beamlines at APS, and nearly 900 total beamlines at synchrotron radiation facilities around the world. (The demand for refractive optics will be even higher if one includes the X-ray free-electron laser (FEL) facilities and laboratory X-ray instruments.)
Figure 2. Top: CAD model of an array of two-dimensional (2D) compound refractive lenses are used for 2D focusing of X-rays. Bottom: Near-field X-ray imaging of polymer 2D lenses printed using single photon lithography.
Figure 3. X-ray lensing using additively manufactured concave arrays at the Advanced Photon Source (APS), Argonne National Labs., Lemont, IL. The hutch in the photograph is at one of ~30 beamlines available at the APS.