Time-resolved heliumlike titanium spectra from the JIPP-T-II-U tokamak

Time-resolved measurements of Ti x x i–Ti x i x x-ray line spectra from an ohmically heated plasma with neon puffing in the JIPP-T-II-U tokamak were made with a high-resolution crystal spectrometer. The spectral data were analyzed by the use of a collisional radiative model which includes the cascade contributions from highly excited states as well as the recombination processes. We have fitted the observed spectra with synthetic calculations taking all the possible lines into account. From the intensity ratios of the satellite lines to the resonance line, the electron temperature $T_e$ was obtained every 20 ms. The result indicates that the plasma is in an ionizing phase at the beginning, reaches nearly an equilibrium around 80 ms, and then turns into a recombination phase, thereafter following the decrease of the electron temperature. The observed intensity ratios $I_x$/$I_w$ and $I_y$/$I_w$ were always found to be more than twice as large as the theoretical ones. The discrepancies increased in the later period of the plasma after $T_e$ decreased, in contrast to the result by Bitter et al. [Phys. Rev. A 32, 3011 (1985)], who found large discrepancies in the early phase of the discharge when $T_e$ was low. However, the experimental data of $I_z$/$I_w$ are in good agreement with calculations when we include the inner-shell ionization of Li-like ions. We investigated the contribution of ion-ion charge-exchange processes on the ion abundances and the line intensities.