Observation of charge-transfer population of high-nlevels inAr+16from neutral hydrogen in the ground and excited states in a tokamak plasma

X-ray spectra of He-like argon (${\mathrm{Ar}}^{+16\mathrm{}}$) have been obtained for the transitions 1snp→1$s^2$, with 3≤n<∞, from Alcator-C tokamak plasmas. In the periphery of the plasma, the n=9 and 10 and 15<n≤40 levels are observed to be predominantly populated by charge transfer between ${\mathrm{Ar}}^{+17\mathrm{}}$ and intrinsic neutral hydrogen in the ground and first few excited states. Neutral hydrogen density pro- files are deduced from these measurements. The first experimental observations of the reactions ${\mathrm{Ar}}^{+17\mathrm{}}$(1s ${\mathrm{}}^2$S)+${\mathrm{H}}_0^{\mathrm{*}}$(n=2,3) →${\mathrm{Ar}}^{+16\mathrm{}\mathrm{*}}$(1snp ${\mathrm{}}^1$P)+${\mathrm{H}}^{+}$ are presented and their cross sections are estimated.