Measurements of the neutron source strength at DIII-D

A set of neutron counters and a pair of scintillators measure the 2.5 MeV neutron emission produced by the DIII-D tokamak. The neutron counter set provides a large dynamic range (∼7 orders of magnitude) while the scintillators provide the very fast resolution needed for studying transient events. The counters are absolutely calibrated in situ with a252Cf source and the scintillators are cross calibrated to the counters. The historic variations in the emission measured by the various detectors have been compared and are consistent within the estimated accuracy of the absolute calibration (15%). In the discharges with the highest emission levels (2.4×1016n/s), the signals from the neutron counters and the scintillators agree well. Comparisons with other diagnostics also corroborate the neutron measurements. © 1997 American Institute of Physics.