An apparatus has been built for the study of energy distributions of reflected and secondary ions emitted from smooth and atomically clean monocrystalline metal surfaces upon bombardment with very low intensity noble gas ion beams (<10 nA cm^-2) in the energy range 0.5-10 keV. This paper is related to the description of the apparatus construction. Basic design features and operation principles are discussed. Experimental procedures are also described, among which those having to do with the generation and maintenance of ideal target conditions are considered to be especially important. The system performance is discussed on the basis of some preliminary experimental results.