''NODUS''-a sensitive new instrument for analyzing the composition of surfaces.

A novel type of ion-scattering spectrometer for analyzing the composition of surfaces is described. By means of a specially designed cylindrical mirror analyzer the sensitivity of the instrument is increased by two or three orders of magnitude as compared with that of equipment used hitherto. The increased sensitivity allows analyses to be performed using extremely low ion doses. Under these conditions, destruction of the surface is negligible. The use of a differential pumping system guarantees UHV conditions at the target, thus minimizing contamination.