Influence of Impurity Concentration on Plasma Confinement in D-3He Fusion Reaction

Plasma confinement along with ash and impurity existence in magnetic fusion devices has been a challenge for researchers. By employing a 0-dimensional model containing power balance and alpha particle balance equations, a numerical analysis is conducted on plasma conditions. The ratio of particle confinement time (τHe) to energy confinement time (τE) is defned by ρ∗ that plays a crucial role in determining the efficiency of He exhaust. The study evaluated the tolerance of burning and ignited D-3He fusion plasma towards impurity concentrations fimp. Various impurity species, including Li, Be, C, N, O, Ne, Ar, Kr, and W, are considered, with impurity radiation losses and ash poisoning integrated into the equations. We used the coronal model with coefficients provided by ADAS database for calculation of impurity radiation in high-temperature D-3He plasma. We examined the impact of impurity ions on D-3He fusion gain Q and power crossing separatrix PSEP, finding that even minor impurities can affect fusion performance, and high-Z impurities significantly reduce fusion gain and increase radiative power loss. For relative concentration of impurities such as Ar, Kr, and W exceeding 0.04, D-3He plasma burn becomes impossible. An increase in the impurity concentration leads to higher burn temperature along with a reduced ρ∗ value. Furthermore, the study explores the interplay between impurity concentration, He ash, and fusion plasma ignition equilibrium. It is concluded that achieving ignition at constant ratio of ρ∗ is not feasible in D-3He plasma when relative concentration of tungsten fW exceeds 4.7 × 10−5. The critical relative concentration of considered impurities in D-3He plasma environment to access ignition at different ρ∗ values are obtained. The study emphasizes that the maximum value of the triple product of low-Z impurities and high-Z impurities has the highest difference. Insight from this study contribute to the continuous efforts to optimize tokamak power plants performance among impurity and ash-related challenges.