Absolute calibration of a total yield indium activation detector for DD and DT neutrons

Progress in Z‐pinch experiments at Sandia’s Saturn facility have underscored a need for an absolute yield measurement for DD fusion neutrons. The technique chosen for making this absolute yield measurement was neutron activation of indium metal samples. To calibrate the technique, a 175‐keV deuteron beam was allowed to impinge on a 3.0‐μm‐thick erbium deuteride target, producing neutrons through the 2H(d,n)3He fusion reaction. The neutron flux produced at 0° and incident on nominal 5‐g indium samples was determined by the associated particle method. This method employed protons measured from the 2H(d,p)3H reaction to infer the neutron flux produced. After neutron irradiation, the activity of the indium samples was measured with a Ge gamma‐ray detector. The total activity of the metastable state 115m In (336.23 keV) was measured, compared with the total incident flux, and a calibration factor (indium counts/neutron/gram of indium) determined. For completeness, a calibration factor for DT neutrons from the 3H(d,n)4He fusion reaction was also obtained through the measured activity of the metastable state 114m In(190.29 keV). The experiment and the measured calibration factors for both reactions are described in the paper.