Satellite spectra for heliumlike titanium. II

Abstract

Eu x-ray spectra of heliumlike titanium, Tixxr, from Tokamak Fusion Test Reactor (TFTR) plasmas have been observed with a high-resolution crystal spectrometer and have been used as a diagnostic of central plasma parameters. The data allow detailed comparison with recent theoretical predictions for the Tixxr heliumlike lines and the associated satellite spectrum in the wavelength 0 range from 2.6000 to 2.6400 A. Improved values for the excitation rate coefficients of the Tixxl resonance linc, the intercombination lines, and the forbidden line, and new theoretical results on the wavelengths and transition probabilities for berylliumlike satellites due to transitions of the type 1s 2lnl'-1s2p2l"nl"' with n =2 -4 have been calculated. These data complement the theory given in an earlier paper [F. Bely-Dubau et al. , Phys. Rev. A 26, 3459 (1982)]. The experimental data are in excellent agreement with the theoretical predictions for the entire satellite spectrum. For plasmas with electron temperatures, T" in the range from 1.2 to 1.8 keV, there is also good general agreement between theory and experiment for the heliumlike lines of TixxI. The observed intensity ratios of the intercombination and forbidden lines to the resonance line are, however, larger than the predicted values by as much as an order of magnitude for electron temperatures T, & 1.2 keV. The enhancement of these lines is correlated with the abundance of lithiumlike titanium. The experimental data indicate that still other atomic processes, in addition to those considered by the theory, are important for the excitation of these lines. The experimental results are documented to stimu-0 late further analysis. The observed wavelengths agree to within an uncertainty of 0.5 mA with predictions from calculations which include relativistic and radiative corrections up to the third order in a. The central ion temperature and the central toroidal rotation velocity of TFTR plasmas with ohmic and neutral beam heating were obtained from Doppler measurements of the Ti xxr resonance line. %wavelength shifts of the apparent resonance line profile due to unresolved dielectronic satellites, which can be important corrections to Doppler-shift measurements of plasma rotation velocities, have been determined as a function of the ion and electron temperatures and the fitting limits. Results on the electron temperature and the relative charge-state density of lithiumlike and heliumlike titanium were derived from the satellite spectrum and have been interpreted with plasma modeling. These results are of interest for the determination of the ionization equilibrium and the impurity transport.

X-ray observations of central toroidal rotation in ohmic Alcator C-Mod plasmas

“…There are x-ray measurements from intrinsic impurities [9,12], but since the viewing angles in these cases are close to radial, the lower limit for toroidal rotation measurements precludes observation during ohmic discharges. Typical values of the rotation velocity with neutral beam input are in the range of a few x 10' cm/s.…”

A high-resolution imaging x-ray crystal spectrometer for high energy density plasmas

“…The main spectral features have been identified as the main He-like lines w, x, and y and the associated Li-like n = 2 satellites of Ti -see Table I. From a comparison with the He-like Ti spectra from TFTR tokamak plasmas, 8 we conclude that the features of the spectrum shown in Fig. 3 are significantly broadened by opacity broadening and possibly Stark broadening.…”

“…4 in Ref. 8. The absence of the line z indicates that the plasma density was so high that the 2s level was depopulated by ion and electron collisions rather than by radiative 2s-1s transitions.…”

Effect of strongly coupled plasma on the magnetic dipolar and quadrupolar transitions of two-electron ions

“…The singlet-triplet transitions in two-electron ions originating from magnetic dipole (M1) and magnetic quadrupole (M2) interactions are of great importance for solar flare and solar coronal studies, for the diagnostic determination of astrophysical and magnetically confined tokamak plasmas, [1][2][3][4][5][6][7] also for the details of evolution in fusion plasmas 8 and estimating their radiative power loss as well as for the study of light matter interactions mediated by the strong magnetic field. [9][10][11][12] The importance of the relative intensities of M1 and M2 transitions of helium like ions for the estimation of electron density in hot plasma has been explicitly shown by Gabriel and Jordan.…”