A Simple Grating Calibrator for the Visible and Vacuum Ultraviolet

Abstract

A calibrator is described for absolute efficiency measurements of concave diffraction gratings in the visible and ultraviolet region of the spectrum. The absence of lenses and mirrors in the optical path reduces many of the problems inherent in previous attempts at absolute efficiency measurements. The calibrator employs an entrance slit, concave grating, and photomultiplier in the Seya-Namioka geometry, with the added provision that the multiplier may be placed at the entrance slit to record the intensity of the monochromatic light incident on the grating. The ratio of multiplier current readings at the normal and entrance-slit positions is the grating efficiency at that wavelength. Efficiency curves showing the effects of polarization and grating blaze have been obtained over a spectral region ranging from 6500 Å to 900 Å.