Abstract
The performance of ellipsoidal mirrors, which can be used to focus soft X-rays to nanometer spots, has not yet been
optimized. Development of the surface profiler used in the fabrication process is a key step toward improving the
performance of such mirrors. Because ellipsoidal mirrors have a complex geometry, our group has developed the
following two-step process for their fabrication. First, a master mandrel with the inverse shape is prepared, after which
the ellipsoidal mirror is fabricated by replicating the surface using an electroforming method. In this study, we develop a
surface profiler for the master mandrel using multiple displacement sensors and motorized stages. One displacement
sensor is used to measure the surface profile and the others are used to measure the motion errors of the stages. The
longitudinal surface profiles of the mandrel could be measured with a repeatability of 1.58 nm (RMS). Based on the
measured shape error profile, shape correction processing was conducted using elastic emission machining (EEM),
which is an ultra-precision technique. After performing EEM three times, the shape error of the mandrel improved from
20.5 nm (RMS) to 4.2 nm (RMS).
