Metrology in the fabrication of nested elliptical KB mirrors

A pair of nanoscale-focusing KirKpatrick-Baez (KB) mirrors used at a hard X-ray synchrotron beamline was produced. Other than traditional sequential arrangement of KB mirrors, the pair of mirrors was set-up side-by-side and perpendicular to each other in a compact nested configuration with large demagnification and flux in focusing X-ray beam. The nested mirror system produced a 2D focal spot about 150 nm in both horizontal and vertical directions with either polychromatic or monochromatic beam [1]. The challenge in fabrication of the mirrors was to preserve the super polished surface of one of the mirror substrates along its useful edge where the X-rays reflect and also to produce best elliptical surface corresponding the design parameters with profile-coating technique. In this paper we mainly describe metrology in the fabrication processes of the mirrors.