Evidence of non-thermal processes in a 1-MJ plasma focus device by analysing the neutron spectra

The spectrum of neutrons from the 1-MJ Plasma Focus of Frascati, in the 90° direction, has been analysed. The spectra have been determined by the time-of-flight method, with a resolution of about 0.12 MeV (∼5%). The presence of secondary peaks, at both sides of a 2.45-MeV peak, constitutes new evidence that a relevant fraction (∼0.5) of the neutron yield is due to non-thermal processes. The interpretation of the secondary peaks by means of beam-target models requires complex beam configurations, such as one or more circular loops or a pattern of divergent beams.