Bendable X-ray Optics at the ALS: Design, Tuning, Performance and Applications - eScholarship

BENDABLE X-RAY OPTICS AT THE ALS: DESIGN, TUNING, PERFORMANCE AND APPLICATIONS V. V. Yashchuk,* ) M. N. Church, J. W. Knight, M. Kunz, A. A. MacDowell, W. R. McKinney, N. Tamura, T. Warwick Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA We review the development at the Advanced Light Source (ALS) of bendable x- ray optics widely used for focusing of beams of soft and hard x-rays – Fig. 1. Figure 1: An example of a bendable optic used at ALS beamline 5.0.2. The mirror with a 900mm long substrate is shown on the Long Trace Profiler (LTP) optical table to be adjusted to the desired spherical shape with radius of curvature of about 2300 m. Typically, the focusing is divided in the tangential and sagittal directions into two elliptically cylindrical reflecting elements, the so-called Kirkpatrick-Baez (KB) pair [1]. Because fabrication of elliptical surfaces is complicated, the cost of directly fabricated tangential elliptical cylinders is often prohibitive. This is in contrast to flat optics, that are simpler to manufacture and easier to measure by conventional interferometry. The figure of a flat substrate can be changed by placing torques (couples) at each end. Equal couples form a tangential cylinder, and unequal couples can approximate a tangential ellipse or parabola. We review the nature of the bending, requirements and approaches to the mechanical design, and describe a technique developed at the ALS Optical Metrology