MONOCHROMATOR WITH SIMPLE GRATING ROTATION AND HOLOGRAPHIC GRATING ON TOROIDAL MOUNT FOR VACUUM UV

Abstract:  CURRENTLY AVAILABLE MONOCHROMATORS WITH CONCAVE GRATINGS WHICH ARE OPERATED BY SIMPLY ROTATING THE GRATING, SHOW A RAPID DECREASE IN THE VACUUM ULTRAVIOLET (AT WAVELENGTHS LONGER THAN 800 A) BECAUSE OF RELATIVELY SMALL ANGLES OF INCIDENCE AT WHICH THESE DEVICES ARE OPERATED. AT HIGH INCIDENCE ANGLES LOW EFFICIENCY CAUSED BY ASTIGMATISM, ACCOMPANIED BY AN EQUIVALENT REDUCTION IN ENERGY THROUGHPUT OCCURS. EFFORTS TO CORRECT THIS ASTIGMATISM IN PART BY USING A HOLOGRAPHIC GRATING ARE DESCRIBED. HOWEVER, FOR SHORT WAVELENGTHS AT GRAZING INCIDENCE, A SPHERICAL CONCAVE HOLOGRAPHIC GRATING CANNOT HAVE MUCH EFFECT ON THE ASTIGMATISM. THIS HAS LED TO THE USE OF TOROIDAL BLANKS, WHICH MINIMIZE ASTIGMATISM OVER THE ENTIRE SPECTRAL RANGE. THE DESIGN AND TESTING OF MONOCHROMATOR WHICH UTILIZES A TOROIDAL BLANK IS DESCRIBED.