X-ray optics laboratory at the ALS: current capabilities, new challenges, and tasks for further development (Conference Presentation)

Abstract

The R&D work on the ALS upgrade to a diffraction limited electron ring, ALS-U, has brought to focus the need for near-perfect x-ray optics, capable of delivering light to experiments without significant degradation of brightness and coherence. The desired quality of the optics is illustrated by the residual surface slope and height errors of <50−100 nrad (rms) and <1−2 nm (rms), respectively. This catalyzes the development at the ALS new ultra-high accuracy metrology methods. Fundamental to the optimization of beamline performance of such x-ray optics, metrology must be capable of characterizing the optics with accuracy even better than the specification. The major limiting factors of the current absolute accuracy are systematic errors inherent to the metrology instruments. Here, we discuss details of work at the Advanced Light Source (ALS) X-Ray Optics Laboratory (XROL) on the development of advanced experimental methods and techniques to suppress, measure, and eliminate the instrumental systematic errors. With examples, we show how the implementation of these methods allows us to significantly improve the capabilities and performance of the existing lab equipment used for characterization and optimal tuning of high quality x-ray optics. We will also review the ALS XROL plans for instrumentation upgrades and development of sophisticated methods for metrology data processing and usage. The discussion will be illustrated with the results of a broad spectrum of measurements of x-ray optics and optical systems performed at the lab. Supported by the U.S. Department of Energy under contract number DE- AC02-05CH11231.