Evaluation of uncertainty in DD neutron yield diagnosis by indium activation

The measurement principle of DD neutron yield diagnosis by indium activation is introduced, and the uncertainty sources of neutron yield diagnosis are analyzed. The measurement uncertainty of DD neutron yield consists of the sensitivity calibrating uncertainty, the net-count uncertainty of radioactive rays, the measurement uncertainty of the solid angle and the random error of the activation system. The calibrating uncertainties of activation sensitivity are determined by such causes including the neutron energy variety in the accelerator neutron source and the measurement error of background neutron of accelerator room. The influence of cosmic rays on the net-count measurement of radioactive rays is analyzed. The main uncertainty source of neutron yield diagnosis in different magnitude range is given, and the improved method of the calibrated activation sensitivity is introduced. The uncertainty of neutron yield diagnosis is calculated based on the experimental data. The result shows that the relative standard uncertainty of the activation system which is calibrated on the accelerator using the associated particle method is 4.3%. When the neutron yield is below 1010, the measurement uncertainty is higher than 7%, and it is mainly caused by the net-count error of radioactive rays. The measurement uncertainty is lower than 7% when the neutron yield is higher than 1010, and it is mainly caused by the uncertainty of calibrated sensitivity.