Wavefront closed-loop correction for X-ray microfocusing active optics

Automatic alignment of a synchrotron beamline by Hartmann technique was performed, in the soft X-ray range (E = 3 keV, lambda = 0.414 nm), using a 4-actuators Kirkpatrick-Baez (KB) active optic. A system imaging the KB focal spot and a soft X-ray Hartmann wave-front sensor were used alternatively to control the KB. The beam corrected with the help of the imaging system was used to calibrate the wave-front sensor. With both closed loops, we focused the beam into a 6.8x9 mu m(2) FWHM focal spot. Closed-loop corrections are limited by the optical quality of the imaging system.