Study of ND$_{\mathrm{3}}$-enhanced MAR processes in D$_{\mathrm{2}}$-N$_{\mathrm{2}}$ plasmas to induce plasma detachment

The Molecular Assisted Recombination (MAR) process is thought to be a main channel of volumetric recombination to induce the plasma detachment operation. Authors have focused on a new plasma recombination process supported by ammonia molecules, which will be formed by impurity seeding of N$_{\mathrm{2}}$ for controlling divertor plasma temperature and heat loads in ITER. This ammonia-enhanced MAR process would occur throughout two steps. In this study, the first step of the new MAR process is investigated in low density plasmas (N$_{\mathrm{e}} \quad \approx $ 10$^{\mathrm{16}}$ m$^{\mathrm{-3}}$, T$_{\mathrm{e}} \quad \approx $ 4 eV) fueled by D$_{\mathrm{2}}$ and N$_{\mathrm{2}}$. Ion and neutral densities are measured by a calibrated Electrostatic Quadrupole Plasma (EQP) analyzer, combination of an ion energy analyzer and mass spectrometer. The EQP shows formation of ND$_{\mathrm{3}}$ during discharges. Ion densities calculated by a rate equation model are compared with experimental results. We find that the model can reproduce the observed ion densities in the plasma. The model calculation shows that the dominant neutralization channel of D$_{\mathrm{x}}^{\mathrm{+}}$ (x$=$1-3) ions in the volume is the formation of ND$_{\mathrm{y}}^{\mathrm{+}}$ (y$=$3 or 4) throughout charge/D$^{\mathrm{+}}$ exchange reactions with ND$_{\mathrm{3}}$. Furthermore, high density plasmas (N$_{\mathrm{e}} \quad \approx $ 10$^{\mathrm{16}}$ m$^{\mathrm{-3}})$ have been achieved to investigate electron-impact dissociative recombination processes of formed ND$_{\mathrm{y}}^{\mathrm{+}}$, which is the second step of this MAR process.