Triton burn-up neutron emission in JET low current plasmas

The 14 MeV neutron emission from JET deuterium discharges is analysed on the basis of the information on all neutron diagnostics available on JET. This emission is due to the d + t → α + n reaction, mainly, the triton burn-up process, and is used to determine the fast triton confinement. A simplified model for triton burn-up neutron emission has been used and provides an adequate description of the 14 MeV emission. First orbit triton losses are found to amount to 50%, 20% and 10% at Ip = 1 MA, 2 MA and 3 MA, respectively. Neutron emission spectroscopy measurements with the magnetic proton recoil neutron spectrometer have detected a contribution to the 14 MeV emission due to residual tritium. For the selected (low impurity) discharges analysed in this paper 15% of the 14 MeV emission comes from the residual tritium reactions. It is also found that the residual tritium concentration tends to increase with increasing impurity content.