Versuche mit einem tiefgekühlten Zwillingsholkathoden-Interferometer—Spektrometer—II. Das optische System

The optical arrangement consists of a double beam imaging system an interferometer spectrometer attached to it. The two cathode spots are projected by the imaging system to the flip-flop mirror in the optical axis of the interferometer. One of the two cathode spots can be projected either to the slit of a spectroscope or to that of a spectrograph, respectively, for preliminary observation. For measuring the intensity ratios, neutral wedges are built into the imaging system. The principal component of the system is a piezo-electrically controlled Fabry—Perot interferometer spectrometer. The deparallelisation of the Fabry—Perot mirrors during the scanning, caused by the “fatigue” of the piezo-electrical system, was eliminated using suitable circuits. The good performance of the interferometer was checked by measuring of the finesse and resolution of selected spectral lines of different spectral lamps and the resonance radiation of a He---Ne gas laser. The optical set-up is suitable for general spectroscopic and spectrographic observations, for measuring radial intensity distributions, for obtaining high resolution spectra and for the determination of intensity ratios in the radiation of the twin hollow cathode source in the visible spectral range.