<title>Design and fabrication of the Schwarzschild objective for soft x-ray microscopes</title>

Abstract

The design of the Schwarzschild objective considering an alignment error is discussed and its fabrication for a soft x-ray microscope is described. It is shown that performance degradation of a Schwarzschild objective by an alignment error can be reduced in a heterocentric system, in which the center of a curvature of a concave mirror is not coincident with that of a convex mirror. Objectives with a magnification of 100 and 224 have been fabricated. To complete an indispensable and difficult alignment within the objective itself, the two mirrors are mounted together in the same frame. The alignment errors of the mirrors are detected and their positions are corrected in a newly developed alignment system, which allows the alignment to achieve the tolerance of 0.3 micrometers . The fabrication of Mo/Si multilayers used for the mirrors are also described briefly. A reflectometer using a laser produced plasma source has been developed to measure reflectances of multilayers. The Mo/Si multilayer deposited by magnetron sputtering shows a reflectance over 40% at a wavelength of roughly 135 angstroms.