Variation of neutron yield from a titanium-tritide target during deuterium beam bombardment.

In the laboratory simulation of D-T fusion breeder blankets 14 MeV neutrons are produced by the bombardment of a titanium-tritide target with deuterium ions using accelerating voltages up to 500 keV and beam currents ranging from micro to milliamperes. For the accurate determination of tritium breeding ratios in the experimental assemblies an absolute determination of the total neutron yield over the irradiation period is required. The theoretical and experimental methods used to determine the ion composition of the deuterium beam the changing absolute yields and energy distributions of the neutrons emitted from the target during prolonged irradiation are described using the AAEC 14 MeV neutron generator as a typical example. Analysis of the measured data identified two ion species in the beam of the neutron generator. It was shown that after a 21-hour irradiation of the target with a 250 mu A beam (18.5C) at 200 kV the neutron output from the D-T reaction dropped from an initial value of 2 x 10 1 0 to 4 x 10 8 neutrons per second. The integrated neutron output over this period was estimated to be 2.05 x 10 14 of which about 24 per cent originated from the interaction of monatomic ions and 75 per cent from diatomic ions; less than one per cent arose from D-D reaction