Development of neutron self-indication thermometry at J-PARC

Abstract

ABSTRACT Determining temperatures with small uncertainties is important for neutron thermometry, required for both fundamental science and industrial applications. Conventionally, neutrons transmitted through a sample in shielded materials are detected. The sample temperature is then derived by analyzing the energy dependence of the transmission neutrons at resonances influenced by the Doppler-broadening effect. However, reducing the temperature-determination uncertainty is extremely hard with the conventional method, because it is determined only by the small changes at the resonances, i.e. temperature-sensitive components, compared to the primary neutrons. Therefore, we propose a new thermometry named neutron self-indication thermometry (NSIT), which combines the Doppler-broadening effect with a self-indication technique that irradiates the sample and an indicator containing the same nuclide as the sample. The NSIT can enhance temperature sensitivity by measuring prompt gamma-rays to indirectly obtain the temperature-sensitive components at resonances by employing the same resonance twice. The temperature sensitivity and uncertainty of the NSIT were compared with those of the conventional method by varying the sample temperatures from 23.0°C to 492.6°C. The results demonstrated that the NSIT was approximately 1.6 times more sensitive and had lower uncertainty in determining temperature. These findings highlight the potential of the NSIT as an effective alternative to remote thermometry.