Calculations of Grating Efficiency in the Soft X-Ray Region*

Abstract

Modified expressions for reflection coefficients are derived for the purpose of predicting the energy distribution among spectral orders produced by a grating at near grazing incidence. Predictions carried out under reasonable simplifying assumptions are compared with experimental data obtained by the use of a grating with 30 000 lines/in. set at a grazing angle of 4.64°. Experimental evidence indicates that in the particular arrangement first-order spectra begin to have appreciable intensity at about 60 A, while second and third orders become observable at 100 A and 150 A, respectively. At 110 A, the fraction of the incident energy present in the first- and second-order spectra is 5.4% and 1.5%, respectively. The calculations are in good general agreement with the observed response of the grating.