Experimental Methods For Optimal Tuning Of Bendable Mirrors For Diffraction-Limited Soft X-Ray Focusing

We report on hands-on experimental methods developed at the Advanced Light Source (ALS) for optimal tuning of mechanically bendable x-ray mirrors for diffraction-limited soft x-ray nano-focusing. For ex situ tuning of the benders for optimal beam-line performance, we use a revised version of the method of characteristic functions recently developed at the ALS optical metrology laboratory. At-wavelength optimal tuning of bendable optics consists of a series of wavefront-sensing tests with increasing accuracy and sensitivity, including modified scanning-slit Hartmann tests. The methods have been experimentally validated at ALS test beamline 5.3.1 and the micro-diffraction beamline 12.3.2 in applications to optimally set bendable Kirkpatrick-Baez mirrors designed for sub-micron focusing.