ITER relevant developments in neutron diagnostics during the JET Trace Tritium campaign

During the JET Trace Tritium campaign a few new neutron diagnostic systems were deployed under different plasma scenarios to provide information on the total neutron emission and its spatial and energy distribution. The 14 MeV neutron yield was measured with a chemical vapour deposited (CVD) diamond detector. Comparison with the JET 14 MeV monitors (Si diodes) illustrates the good performance of the CVD device. Key information on the tritium transport and the behaviour of fast particles in the plasma was obtained from the spatially and temporally measurements of neutron emission from the upgraded neutron profile cameras which also provide an independent measure of the total neutron yield. Spatial asymmetries in the neutron emission were observed which is evidence for the influence of fast particles on the plasma. With regard to the energy distribution of the neutron emission, a spectrometer based on a liquid organic scintillator with n-γ pulse shape discrimination (PSD) features was installed. The results demonstrate that such system can operate in real fusion experiments as compact broadband neutron (1.5 MeV < E_n < 20 MeV) spectrometer with high energy resolution. A fast transient recorder has been successfully applied for digital pulse shape discrimination (DPSD) of neutron and gamma events acquired with an organic scintillator at high count rate operation (MHz range). The experience gained at JET indicates that these neutron measurement systems are suitable for large fusion devices such as JET-EP and ITER where fusion neutron diagnostics will play an increasingly important role.