Asphericalizing the Light Collection Mirror for the 200-Point Thomson Scattering Diagnostic Installed on the Large Helical Device

Shown is a possibility to make the image of a laser beam over a distance of 2.5 m, formed by the spherical multi-segment mirror installed in LHD, twice sharper by suitably adjusting the inclination of each segment mirror, which is equivalent to making the mirror surface aspherical. This will further enhance the attractiveness of a mirror-based Thomson scattering system.