Image evaluation of the one-meter Seya Namioka monochromator at INDUS-1 synchrotron source by ray tracing

A VUV spectroscopic facility for studies in photophysics and photochemistry will be set up at INDUS-1 synchrotron source which is being constructed at the Centre for Advanced Technology, Indore, India. In this facility a toroidal mirror will focus the light originating from the tangent point of the synchrotron source onto the horizontal entrance slit of a one meter Seya Namioka monochromator. The monochromator uses a concave grating having groove density of 2400 lines/mm and rules area of 50 mm x 40 mm. A second toroidal mirror will focus the light emerging from the exit slit of the monochromator on the experimental sample. A ray tracing program has been formulated and spot diagrams have been constructed by plotting the ray intersection points on a plane which contains the exit slit of the monochromator. From the spot diagrams, the spectral image blur has been measured and the resolution has been estimated. It has been found that an average spectral resolution of 1.2 A in the first order can be achieved throughout the wavelength region of 300 A to 2000 A, when the slit width is 100 micrometer and the limiting spectral resolution is 0.5 A due to point source illumination. (author). 14 refs., 7 figs., 2 tabs