Fizeau interferometer system for fast high resolution studies of spectral line shapes

A monochromator∕Fizeau interferometer∕intensified CCD camera system is described that was developed for the measurement of the shape of spectral lines that are rapidly time varying. The most important operating parameter that determines the performance of the instrument is the size of the entrance aperture as this determines both the light throughput and the effective interferometer wavelength resolution. This paper discusses, both theoretically and experimentally, the effect of the finite source area on the instrumental resolution to assist in optimizing the choice of this parameter. A second effect that often produces a practical limit to the quality of the spectra is drift of the interferometer plates. Measurements of the shapes of spectral lines of ions and atoms ejected from the cathode spot of continuous and pulsed cathodic arcs are presented to demonstrate the utility of this instrument.