A detector system based on partially depleted silicon surface barrier detectors and fast front-end electronics has been built and cross calibrated to a set of absolutely calibrated 'He recoil detectors. The cross-calibration factor for the channel with the widest dynamic range is 2.5X lo-r3 counts per 14 MeV source neutron. These data agree well with the independent neutron activation data. The new detector system covers a large dynamic range (corresponding to 1O13-1O's neutrons/s). The

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... is linear, except at the highest count rates where the detector dead time (-200 ns) causes departure from linearity. The noise discrimination against 2.5 MeV neutrons and y pileup is excellent. Measurements of D-T neutrons from a tritium gas puff experiment as well as from a high-power D-T discharge in the TFTR tokamak are presented. 0 1995 American Institute of Physics.