Time dependent neutron emission rate analysis for neutral-beam-heated deuterium plasmas in a helical system and tokamaks

A neutron emission rate analysis code called FBURN, based on the classical energetic ion confinement assumption with radial diffusion, is developed for the time-dependent analysis of the total neutron emission rate (S-n) in neutral beam (NB) heated deuterium plasmas. The time trend of S-n evaluated by FBURN shows good agreement with the S-n measured by the neutron flux monitor on the deuterium operation of the Large Helical Device. The dependence of S-n on line-averaged electron density (n(e)_(avg)) has a peak at n(e)_(avg) of around 2.5 x 10(19) m(-3) in both experiment and calculation. Here, the absolute value of S-n evaluated by calculation agrees with that obtained in experiments within a factor of two. A time trend analysis of S-n in an electron cyclotron heated plasma with a short pulse NB injection is performed. The analysis shows that the diffusion coefficient of co-going transit beam ions is 0.2 to 0.3 m(2) s(-1). In addition, the diffusion coefficient of helically trapped beam ions decreases from 5 to 3 m(2) s(-1) with the inward shift of the magnetic axis position. Time-resolved analysis of the triton burnup experiment shows that the diffusion coefficient of tritons is around 0.15 m(2) s(-1). It is found that the diffusion coefficients of the beam and tritons are of a similar value as obtained in JT-60U. The trend of the triton burnup ratio on the n(e)_(avg) calculated by the FBURN agrees with the experiments. The results suggest that the decrease of the triton burnup ratio with the increase of n(e)_(avg) is due to the shorter slowing down time of tritons by the decrease of the electron temperature, and the increase of the triton burnup ratio with the increase of n(e)_(avg) is due to the diffusion of tritons. Time trend analysis of S-n in the Korea Superconducting Tokamak Advanced Research and the Experimental Advanced Superconducting Tokamak plasmas with a short pulse NB injection is performed. The time trend of S-n is successfully reproduced by FBURN.