Profile Measurements in ITER by means of Neutron Spectroscopy, Ion Temperature Diagnostics for Experimental Thermonuclear Fusion Reactors

• Information on ion temperature profiles will be needed for burn optimisation and transport studies in ITER. The feasibility of deriving these profiles for the core plasma (r< 0.75a) directly from the width of measured 14-MeV neutron energy spectra is demonstrated for Maxwellian ion distributions. Neutron energy spectra and fluxes generated under different heating conditions are calculated by means of Monte-Carlo technique. The computation takes the reaction kinematics and the velocity distributions of the reacting ions into account and calculates the resulting neutron energy distribution and flux into a defined collimator. Energy spectra of neutrons emitted along a line-of-sight are superimposed. The associated correction factor, which depends on the measured ion temperature, can be given an analytical form when fitted to code data and is insensitive to large variations in temperature-, density and magnetic flux profile shapes. The accuracy in ion temperature evaluation is expected to be better than ± 10% and can be improved to ± 5% provided information on fuel density profiles are made available.

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