A study of the high-energy part of the deuteron spectrum produced by the Frascati 1-MJ plasma focus device is carried out through measurements of (a) the energy distribution of prompt neutrons emitted by D(d, n) and 7Li(d, n) reactions using three time-of-flight spectrometers and (b) the total neutron fluence and the high-energy neutron fluence using silver- and lead-activation counters, respectively. The results clearly confirm the existence of an energetic deuteron beam, Eb = ≤2 to 4≥ MeV, and lower energy streams circulating in the plasma, Es ≅ 100 keV, responsible for the main part of the neutron production through the D(d, n) process, with the ratio of the two components, . The methodology of measurements and of data analysis described represents a definite improvement with respect to those described in previous publications.