Identification of neutrino interactions using the DONUT spectrometer

The experimental apparatus used for the first direct observation of the tau neutrino (the DONUT experiment) is described. Its main features consisted of a target system composed of nuclear emulsion targets and scintillation fiber trackers, a magnetic charged-particle spectrometer and detectors for lepton identification. This paper will concentrate on the description of the electronic detectors and their performance in selecting neutrino interactions, making the vertex predictions necessary for locating events in the emulsion target and lepton identification.