Application of Linear Combination Method to Pulsed Neutron Source Measurement at Kyoto University Critical Assembly

The applicability of the linear combination method is experimentally confirmed through the pulsed neutron source (PNS) experiment. The linear combination method reduces the spatial higher-mode (HM) components in neutron flux distribution and provides one representative value of the measurement of the prompt neutron decay constant by the linear combination of the neutron counts obtained in the PNS experiment. The PNS experiment is conducted at Kyoto University Critical Assembly with deuteron-tritium source, and the neutron counts are measured at multiple detector positions. The experiment results show that the dependency of the prompt neutron decay constant on the masking time is dramatically reduced by the linear combination method compared to the conventional method: The HM components are eliminated not only by temporal decay but also by the linear combination. Through the experiment, the linear combination method can be a candidate for a practical measurement method of the prompt neutron decay constant reducing the spatial HM effects.