Grazing incidence spectrometer with variable angle of incidence

A grazing incidence spectrometer for the 10-600-A wavelength range equipped with a 1-m concave grating of 600 lines/mm or 3600 lines/mm is described. The angle of incidence can be continuously varied between 89 degrees and 80 degrees This makes it possible to shift the angle of incidence to where the reflected intensity of the wavelength to be measured and the intensity ratio of this wavelength to interfering wavelengths of higher orders are maximized. Spectra of the C V (lambda = 40.73 A) and O VII (lambda = 21.8 A second order) lines show that in fact the second-order spectra can be reduced considerably. For photoelectric registration, twregistration,two independent detectors can be moved along the Rowland circle. The arrangement allows the simultaneous measurement of closely adjacent lines, and it is used to observe the time dependenceof N VI (lambda = 29.08 A) and N VII (lambda = 24.78 A) lines emitted by a thetapinch. The resolution of the instrument, lambda/Deltalambda has been determined to be better than 1600 at 66 A.