Research with x-ray, soft x-ray, and EUV wavelengths opens doors to exploration at the nanoscale. Modern synchrotron light sources, which are incredibly bright at these wavelengths, unlock new possibilities for investigations of materials properties that have never been possible before. Yet despite remarkable advances in the source technologies, beamline optics have not kept pace.

Reasonable estimates place the brightness losses from aberrated or misaligned focusing optics anywhere from 10-100×, varying from beamline to beamline. The primary reason for the significant losses is the great challenge of performing surface metrology and in situ alignment with nano-scale tolerances. Aside from scattering, the light is there, it's just not being focused properly. Twenty-first century beamlines are still using 20th century alignment techniques, where the feedback is an order of magnitude less sensitive than necessary.

Our goal is to leverage existing successful techniques from other fields, and to develop new ideas into working optical metrology and alignment methods surpassing the state of the art. Accurate metrology is the cornerstone of active-focusing beamline optics, an idea already being pursued by other leading groups.

How it works. To reach the level of nano-focusing, feedback is the key. The focused beam-spot itself is too small to characterize accurately. We use the powerful class of optical techniques known as interferometry and wavefront sensing to detect, characterize, and correct subtle distortions in the mirror surface that cause optical aberrations. Different tests are suitable for different situations. We are developing a series of tests, with increasing sensitivity, to be applied in series during alignment. The different methods all share compatible hardware, enabling detailed inter-comparison and unprecedented learning opportunities. The methods we develop and perfect can be exported to beamlines worldwide.

View the Project Poster From the 2010 ALS Users' Meeting [4.7 MB]

Our Team. Co-PIs, Valeriy Yashchuk and Kenneth Goldberg have been working in the field of short wavelength optical system metrology for many years. Yaschuk (ALS) is a world leader in the development of instrumentation and methods for the ex situ alignment and characterization of synchrotron optics. Goldberg (CXRO) performed pioneering work in EUV interferometry: in situ, at-wavelength testing and aligning of the highest resolution photolithography lenses ever created. This project merges their expertise bringing new techniques in metrology and coherent optics to enable the next generation of higher-performing synchrotron optical systems.

The project's core team members also include post-baccalaureate fellow, Daniel Merthe; post-doctoral fellow, Sheng (Sam) Yuan; beamline associate, Rich Celestre; and ESG deputy group leader, Tony Warwick. Additional collaborators include senior technician, Greg Morrison; staff scientist, Wayne McKinney; CXRO project scientist, Iacopo Mochi; engineering associate, Nathan Smith; graduate student research associate, James Macdougall; and many others from within The Advanced Light Source (ALS), and The Center for X-Ray Optics (CXRO).

LDRD Sponsorship. This project is funded by LBNL's Laboratory Directed Research and Development (LDRD) program. Looking beyond the near-term improvement of Advanced Light Source beamline optics metrology, this work supports the long term goals of providing optics for the Next Generation Light Source (NGLS). NGLS beamline optics specifications are anticipated to exceed today's fabrication and alignment metrology limits. Developing, proving, and refining new, ultra-high-accuracy, in situ x-ray metrology techniques is an essential step for meeting the scientific and engineering challenges the NGLS represents.