Basic study on development of neutron spectrometer based on multiple-scattering TOF for D/T burning ratio measurement

Asai, Keisuke*; Naoi, Norihiro*; Iguchi, Tetsuo*; Watanabe, Kenichi*; Kawarabayashi, Jun*; Konno, Chikara  

We have been developing a time-of-flight neutron spectrometer to measure the fuel ratio in burning plasma core. This system consists of a water cell and a pair of scintillators. The water cell is inserted before the scintillator pair. The pair of scintillators is used to measure the flight time of the scattered neutron from the water cell. Elastic scattering with hydrogen nuclei in the water cell enhances the DD/DT neutron ratio and make the detection of DD neutron easier. We have considered the system configuration by Monte Carlo simulations and clarified the expected measurement accuracy and time resolution in the upper region of the ITER DT phase. This system is expected to achieve a time resolution of a few seconds with 20% accuracy for a measurement of the intensity ratio of DD/DT neutron at the ITER full power operation.