Regression Approach for Acquiring a Quantitative Guidance toward Updating the Deuterium-Deuterium Fusion Neutron Emission Rate in the Large Helical Device

Abstract

A regression approach has been adopted to acquire a quantitative guidance for updating the total neutron emission rate (S_n) in the Large Helical Device (LHD) with employing the externally controllable parameters such as heating power and plasma density. A deduced regression expression is worthwhile to understand for the contribution of an individual parameter during high S_n discharges, and then to be exploited in the experiment planning to update the record S_n value in LHD in the coming campaigns. It was found that S_n in high S_n discharges in LHD is expressed as S_n = 10^14.25 × n_{e_avg}^0.52 × P_N-NB^0.69 × P_P-NB^0.37, where n_{e_avg}, P_N-NB, and P_P-NB represent the line-averaged electron density [10¹⁹ m⁻³] and the injection power of negative and positive ions based neutral beam injection [MW], respectively. This expression shows that, among three parameters, P_N-NB is essential for achieving high S_n in this employed high S_n discharge database.