Abstract
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 4He recoil detectors. The cross-calibration factor for the channel with the widest dynamic range is 2.5×10−13 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 1013–1018 neutrons/s). The response 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 γ 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.
Highlights
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
Since the startup of D-T operations at TFTR, in December 1993, accurate measurement of 14 MeV neutrons is of paramount importance
Time-resolved measurements of 14 MeV neutron emission are essential for insight into the tritium transport in tokamak plasmas and for determination of the peak fusion power
Summary
Since the startup of D-T operations at TFTR, in December 1993, accurate measurement of 14 MeV neutrons is of paramount importance. Silicon diodes were used for time-resolved measurements of D-T neutrons produced by 1 MeV tritons on JETa and DIII-D.3. They provided clear 14 MeV neutron emission data from the first trace tritium experiments at JET, when the D-D neutron emission was about five times stronger than the D-T emission. Such measurements are possible because the ?Si(n ,p)a’Al and %i(n, cr)25Mg nuclear reactions have an effective threshold of -7 MeV, being insensitive to the 2.5 MeV D-D neutrons.
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