An investigation of divertor plasma recombination using a molecular collisional-radiative model

Divertor detachment provides an optimal way of managing the power and particle exhaust, which is crucial for reducing the target damage and achieving the steady-state operation of a tokamak. The modeling of divertor detachment poses a significant challenge due to the diverse physics involved, especially molecular kinetics. Additionally, the molecular activated recombination (MAR) is suggested to play a crucial role in divertor detachment since the vibrationally excited hydrogen molecules can create effective pathways for the plasmas to recombine at low temperatures (~2 eV). Here, to understand the effects of molecules on plasma recombination at the target, we couple the atomic collisional-radiative (CR) code FLYCHK lite with molecular features that resolves various vibrational levels of the molecules. The molecular chemical reaction rates are evaluated by all-order methods (computationally expensive and complicated methods), which are required in order to achieve good levels of accuracy for near-neutral species (e.g., a recombining plasma). With the newly developed model that resolves the vibrational levels and reactions accurately, we will be able to show the dominant MAR channels where the plasma recombination is enhanced.