A High Vacuum Recording Spectrograph for the Study of Radiation from Solids in the 100–800A Range

The two-meter grazing-incidence vacuum spectrograph used by O'Bryan and Skinner for the study of the emission bands of solids has been rebuilt to operate with improved sensitivity and speed. The major modification is the replacement of the photographic plate by a Be–Cu photomultiplier which is designed to traverse the Rowland circle, giving a continuous record of photon-counting rate as a function of a wavelength. With the photomultiplier it is possible to take as many separate curves as desired, subject to x-ray target condition, without opening the spectrograph, which is normally evacuated to better than 10−5 mm Hg. In addition, the sensitivity is increased about a thousandfold; i.e., with a photographic plate, the target current and voltage needed are 10–100 ma and about 3000 v for a one- to three-hour exposure. Using the photomultiplier, however, these values may be reduced to 2–3 ma and 300–500 volts, respectively, and the complete emission band may be recorded in five minutes. The results for aluminum are in excellent agreement with the results of previous authors.