Charge-exchange measurements of d-d triton distribution functions in high-power neutral beam heating on JT-60U

We present the first results of the fusion triton measurements in JT-60U using the MeV energy range neutral particle analyzer (NPA). An energy distribution of slowing-down fusion tritons has been obtained during the experiments of high-power neutral beam injection (NBI). We associate a dominant mechanism of triton neutralization with charge-exchange (CX) on the plasma residual neutral deuterium and on the hydrogen-like carbon impurity ions. To determine a contribution of these processes in triton neutralization the simplified steady-state balance of carbon impurity ions is considered. The spectrum of slowing-down triton is modelled using the analytical solution of the simplified zero-dimensional Fokker-Planck equation. A good agreement between the experiment with the model is demonstrated.