Multi-scattering time-of-flight neutron spectrometer for deuterium to tritium fuel ratio measurement in fusion experimental reactors

A time-of-flight (TOF) neutron spectrometer has potential as a fuel ratio (nD/nT) measurement system in the International Thermonuclear Experimental Reactor (ITER). A new neutron spectrometer is proposed to monitor the fuel ratio in the core of the ITER plasma. This system is based on a conventional TOF method and is composed of a water cell and a few tens of scintillator pairs. The water cell is inserted before the first scintillator of the TOF system and serves as a neutron scattering material. A trial experiment demonstrates the feasibility of this system for detecting trace-DD neutrons within a DT neutron beam. The system responses to DT and DD neutrons are also presented.