Development of neutron measurement system for nd/nt fuel ratio measurement in ITER experiments

The possibility of measurement of fuel ratio from the DT/DD reaction ratio with a neutron spectrometer in the International Thermonuclear Experimental Reactor was studied. The results of neutron transport calculations using the Monte Carlo N-particle [MCNP, a general Monte Carlo N-particle transport code, version 4C, LA-13709, edited by J. F. Briesmeister, Los Alamos National Laboratory, 2000] code system indicated the possibility of DD spectrum separation from the scattered/energy-degraded neutrons derived from DT neutrons by selection of the measurement location and collimator design. A time-of-flight spectrometer was used in this study. An experiment using DD and DT neutrons from an accelerator was conducted at the Japan Atomic Energy Agency Fusion Neutronics Source facility. Using a sophisticated circuit with three discriminators for the first detector, separation of DD and DT neutron components of the spectrum in the megahertz region was confirmed experimentally. (c) 2006 American Institute of Physics.