Development of technology for vacuum ultraviolet plane grating monochromator to be used with XUV synchrotron source of INDUS I

Abstract

The plane grating monochromator is to be used with the 480 MeV ((lambda) _c equals 61 angstroms) consists of a, plane grating, plane mirror (500 mm × 50 mm) and an ellipsoidal mirror (300 mm × 50 mm, & semi-major axis 39935.7 mm, semi-minor axis 378.84 mm and eccentricity is 0.999955 viz center of the mirror x equals 38433.772 mm, y equals 102.920 mm). The technology for fabricating the plane mirror and the ellipsoidal mirror is being developed at Photonics Division, Indian Institute of Astrophysics. The optical requirement for these mirrors in terms of tangent error better than 1 sec of arc and the micro roughness better than 5Å is dictated by the design parameters of the monochromator. With these specifications in mind Zerodur substrate material has been chosen in the first phase of the development. For the fabrication of the ellipsoidal mirror a new machine has been designed and fabricated for different stages of grinding, polishing and figuring. The flat and the ellipsoidal mirror are in the final stages of figuring. The paper presents the technology development for manufacturing of these mirrors and the measurement procedures adopted during the fabrication. Problem areas have also been discussed.