TFTR experiments with 2% tritium beam fuelling

Tritium has been injected into TFTR supershots using a gas feed containing 2% tritium and 98% deuterium in one or more neutral beam sources. A total of 38 beam-injected tritium shots required about 400 Ci of tritium, of which less than 5% actually entered the plasma. The ratio of D-T to D-D neutron rates varied from about 0.5 to 4.5. A peak neutron rate of 7.7 × 10¹⁶ D-T n/s together with 1.7 × 10¹⁶ D-D n/s was attained with eight 2% tritium beams delivering 18.7 MW. The measured D-T neutron rates are extrapolated to fusion powers in 50:50 D-T operation with similar plasma parameters. The experiments have also provided data for the D-T calibration of neutron and lost alpha particle detectors and for optimizing tritium beam injection. With the aid of a multichannel neutron collimator, these experiments have enabled the comparison of radial profiles of D-T neutron production and global neutron output with the predictions of simulation codes.