<RESEARCH REPORT>Time resolved heliumlike titanium spectra from JIPP T-IIU tokamak

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Time resolved measurements of TiXXI-TiXIX X-ray line spectra from an ohmically heated plasma with neon puffing in the JIPP T-IIU tokamak were measured with a high resolution crystal spectrometer. The spectral data were analysed 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 temperatures 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 turned 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 more than twice larger than 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. 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 to the ion abundances and the line intensities.
核融合科学研究所の論文