Measurement of wavelengths with phosphor storage image plates on a grazing incidence spectrograph

We recorded the spectra emitted by a Ne/Mg Penning discharge and by sliding spark discharges of Y and Mo in the 150-450 A range with phosphor storage image plates on a 10.7 m grazing incidence spectrograph. To obtain better conformance of the image plates to the focal surface of the concave grating, the plates were mounted on the curved surface with a backing of flexible steel plates. The exposed plates were read by a rotary drum scanner. With these techniques we achieved a wavelength accuracy of approximately 0.003 A. This is comparable to what is normally obtained with photographic plates on this instrument.