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-mum-thick erbium deuteride target, producing neutrons through the (H(d,n)He)-H-2-He-3 fusion reaction. The neutron flux produced at 0-degrees and incident on nominal 5-g indium samples was determined by the associated particle method. This method employed protons measured from the (H(dp)H)-H-2-H-3 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 In-115m (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 (H(d,n)He)-H-3-He-4 fusion reaction was also obtained through the measured activity of the metastable state In-114m(190.29 keV). The experiment and the measured calibration factors for both reactions are described in the paper.