NEUTRON EMISSION PROFILE MEASUREMENTS DURING THE 1ST TRITIUM EXPERIMENTS AT JET

During a series of experiments with tritium (T) in deuterium (D) plasm as in the Joint European Torus (JET), the temporal evolution and the t wo dimensional (2-D) spatial profiles of the 2.5 and 14 MeV neutron em issivities from D-D and D-T fusion reactions were inferred from measur ements with the JET neutron emission profile monitor. These experiment s, involving triton production from D-D fusion, beam deposition and di ffusion, D-T fusion, and tritium removed from wall tiles, were investi gated in four plasma scenarios: (i) In high performance deuterium plas mas with deuterium neutral beam injection, the 14 MeV neutron emissivi ty due to triton burnup was observed. (ii) In discharges with 1 % trit ium beam injection, neutron emissivity ratios showed that approximatel y the same deposition profiles resulted from tritium as from deuterium beams. A thermalized tritium diffusion experiment was performed in wh ich the T-D density ratio was found to be spatially constant across th e plasma; in conjunction with similar particle source profiles, this i ndicates that deuterium and tritium have similar particle transport pr operties. (iii) In two high performance discharges for which two of th e sixteen neutral beam sources operated with 100 % tritium, the produc tion rate of 14 MeV neutrons reached 6 X 10(17) n . s-1. The alpha par ticle 2-D birth profile was directly inferred from the measured 14 MeV neutron emissivity profile. Both the axial 14 MeV neutron emissivity and the axial ion temperature saturated before the maximum global emis sion was reached. (iv) During the tritium cleanup phase, residual trit ium entering the plasma produced a spatially constant ratio of tritium to deuterium, confirming the similarity of their particle transport p roperties.