Ti XVII Research Articles

Theoretical Study of Laser Emission for C-Like (Ar XIII), (Ti XVII) and (Fe XXI)

Energy levels, transition probability and oscillator strengths have been calculated for the Ar XIII, Ti XVII and Fe XXI. The configurations included in the calculations are 2s2 2p2, 2s2 2p 3l (l = s, p & d) and 4l (l = s, p, d, & f) of C-like Ar XIII, Ti XVII & Fe XXI which has 69 fine structures by using the fully relativistic flexible atomic code (FAC) program. These data are used in the determination of the reduced population and gain coefficients over a wide range of electron densities from (10+18 to 10+23) and at various plasmas temperatures. The results show that the transitions in Ar18+, Ti22+, and Fe26+ ions are the most promising laser emission lines in the XUV and soft X-ray spectral regions.

Relativistic configuration interaction calculations of energy levels, isotope shifts, hyperfine structures, and transition rates in the 2s22p2–2s2p3 transition array for the carbon-like sequence

Energy levels, fine-structure separations, specific mass shift parameters, isotope shifts, hyperfine interaction constants, Landé gJ-factors and transition probabilities are reported for the 2s22p2–2s2p3 transition array in N II, O III, F IV, Ne V and Ti XVII. Wavefunctions were determined using the multiconfiguration Dirac–Hartree–Fock method with account for valence, core-valence and core–core correlation effects. The transition energies and rates are compared with experimental data and with values from other calculations.

Oscillator strengths for transitions in C-like ions between K XIV and Mn XX

Energy levels and oscillator strengths (transition probabilities) have been calculated for transitions among 46 fine-structure levels of the (1s 2 ) 2s 2 2p 2 , 2s2p 3 , 2p 4 , 2s 2 2p3s, 2s 2 2p3p and 2s 2 2p3d configurations of C-like K XIV, Sc XVI, Ti XVII, V XVIII, Cr XIX and Mn XX using the GRASP code. Configuration interaction and relativistic effects have been included while generating the wavefunctions. Calculated values of energy levels agree within 3% with the experimentally compiled results, and the length and velocity forms of oscillator strengths agree within 20% for a majority of allowed transitions.

CROSS SECTIONS AND RATE COEFFICIENTS FOR EXCITATION OF THE 1s22s22p23PJ → 1s22s22p23PJ′ FINE-STRUCTURE TRANSITIONS IN CARBON-LIKE IONS BY HEAVY PARTICLE IMPACT

We have calculated cross sections for excitation of the fine-structure transitions in carbon-like ions by proton, deuteron, triton, and α-particle impact via a close-coupled impact-parameter method. This technique includes the effects of dipole coupling to the nearby triplet 2s2p3 configuration by means of a polarization potential. We consider the ions N II, O III, Ne V, Mg VII, Si IX, S XI, Ar XIII, Ca XV, Ti XVII, Cr XIX, Fe XXI, and Ni XXIII. Excitation rate coefficients have also been calculated for a range of temperatures.

Theoretical emission line ratios for carbon-like Ti XVII, Cr XIX and Ni XXIII and a comparison with PLT tokamak observations

Recent electron-impact excitation rates for the C-like ions Ti XVII, Cr XIX and Ni XXIII are used to derive electron density sensitive emission line ratios applicable to the ultraviolet spectra of tokamak plasmas. A comparison of these with ratios measured from the Princeton Large Torus (PLT) tokamak reveals good agreement between theory and observation. These results confirm the validity of the atomic data adopted in the line ratio calculations.

Safety factor measurements on the magnetic axis of the Texas experimental tokamak plasma in Ohmic and electron-cyclotron-resonance heated discharges.

Analysis of the circular polarization of a spectral line emission inside plasmas provides a measurement of the poloidal magnetic field on the Texas experimental tokamak (TEXT). Three sets of different polarimeters, using, respectively, the Ti XVII 3834-\AA{} line of the intrinsic titanium impurity and the Li I 6708-\AA{} line of a monoenergetic lithium beam, were developed and operated on TEXT. The safety factor q on the magnetic axis, determined from the measured magnetic field, was found to be near unity in all cases of Ohmically heated sawtoothing and nonsawtoothing discharges, and significantly below unity in the case of electron-cyclotron-resonance heating at the plasma center for high edge q discharges.

Ion temperature measurements in the ATF torsatron using titanium forbidden lines (abstract)

Several forbidden lines of titanium have recently become strong enough to be identified in ATF plasmas in the ultraviolet and in the visible. The increase in intensity has resulted from gettering of the vacuum vessel with titanium both to suppress light impurities and to control hydrogen recycling. Three orders of the forbidden Ti xiv line at 2117.1 Å have been observed in vacuum, and the second and third orders have been observed in air using two different Czerny–Turner spectrometers. Doppler broadening of this line has been used to infer ion temperatures in the interior of ATF plasmas. These data supplement ion temperature measurements employing lines from carbon, nitrogen, and oxygen reported earlier [R. C. Isler et al., Nucl. Fusion 29, 1391 (1989)]. Tentative identifications of other forbidden lines such as Ti vii at 1938.4 Å, Ti xv at 2544.8 Å, Ti xvii at 3370.8 Å and 3834.4 Å, and Ti xviii at 1778.1 Å have also been made. Research was sponsored by the Office of Fusion Energy, U.S. Department of Energy, under contract DE-AC05-84OR21400 with Martin Marietta Energy Systems, Inc.

Scanning polarimeter for measurement of the poloidal magnetic field in a tokamak

The internal magnetic field in a magnetically confined plasma may be deduced from the analysis of circular polarization of spectral lines emitted by the plasma. The theory of the measurement and a detailed design of a polarimeter constructed to measure the poloidal field profile in the Texas Experimental Tokamak (TEXT) are presented. The instrument measures the difference between left-hand and right-hand circularly polarized line profiles, a quantity directly proportional to the magnetic field component in the direction of observation. The high throughput of the Fabry–Perot interferometer employed in this design, combined with efficient light-collecting optics and lock-in detection of the polarization signal, allows measurement of the fractional circular polarization of the magnetic dipole line Ti xvii 3834 Å with an accuracy on the order of 10−3. The line-of-sight averaged poloidal field is determined with uncertainty as small as 50 G. The line emission used in the present measurement is not well localized in the plasma, necessitating the use of a spatial inversion procedure to obtain the local values of the field.

Spectroscopic measurement of the poloidal field profile in the TEXT

The poloidal field profile in the Texas Experimental Tokamak is determined from the analysis of circular polarization of the forbidden (magnetic dipole) line Ti xvii 3834 Å. A high-sensitivity polarimeter measures the difference between right- and left-hand circularly polarized line profiles, a quantity which is directly proportional to the magnitude of the magnetic field component in the direction of observation. The fractional circular polarization smaller than 10−2 can be detected, which allows determining the poloidal magnetic field in the center of the plasma with uncertainty as small as 50 G. The instrumentation is relatively simple and inexpensive. Description of the polarimeter and results of measurement of the poloidal field profile and the safety factor on the tokamak axis are presented.

Ionization and recombination rates for highly ionized titanium ions from time-resolved spectroscopy of tokamak plasmas.

The effective ionization and recombination rate coefficients for Ti xvii--xx were obtained by studying the modulation of line emission by sawtooth oscillations in the TEXT tokamak at the University of Texas. Experimental data are matched with the simulation of titanium-ion emission by a one-dimensional (1D) transport code which includes ionization and recombination processes. The rate coefficients were determined for ${T}_{e}$\ensuremath{\approxeq}600--1100 eV and ${N}_{e}$\ensuremath{\sim}4\ifmmode\times\else\texttimes\fi{}${10}^{13}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$. The ionization rates were about 20% higher than values calculated by Lotz's formula. The recombination rates were about 20% less than theoretical values. The uncertainty of ionization and recombination rate coefficients is estimated to be less than 20% and 60%, respectively. The sensitivity of our method to various parameters, i.e., the diffusion coefficient, convective velocity, and electron temperature, is also discussed.

Zeeman effect polarimetry of Ti XVII 3834 Å line in the Texas Experimental Tokamak

We present the first measurement of a tokamak plasma internal magnetic field based on the analysis of polarization of Zeeman components of a magnetic dipole transition in heavy impurity ion. The circular polarization of the Ti XVII 3834 Å line is studied. The values of the component of the toroidal magnetic field in the direction of observation are measured for several observation angles and good agreement with expected values is found. The result indicates that the method may be useful for measuring the local magnetic field and in particular, the poloidal component of the field, in a tokamak.

C I Isoelectronic Sequence: Observations of 2sm2pn-2sm-1 2pn+1 Intersystem Transitions and Improved Measurements for CI XII, K XIV, Ca XV, Sc XVI, Ti XVII, and V XVIII

Spectra of C1 through V (excluding Ar) were produced with a 1 GW (15 ns) pulse from a Nd-glass laser impinging on solid targets and observed with a 10.7-m grazing incidence spectrograph. Strong 2sm2pn-2sm-1 2pn+1 transition arrays in the C I isoelectronic sequence were recorded, from which intersystem lines were identified and improved wavelength measurements of allowed lines were made. Hartree-Fock calculations of the radial integrals were compared with those obtained from least squares fits of the energy levels of this sequence.

Comment on the magnetic dipole lines of highly ionized titanium

A magnetic dipole line in the ground configuration of Ti XVIII has been identified and the accuracy of previous measurements of Ti XIV, XV, and XVII lines has been significantly improved.Received 16 June 1980DOI:https://doi.org/10.1103/PhysRevA.22.2278©1980 American Physical Society

A theoretical study of the np k configurations

An up-to-date picture of the known np 2 and np 3 configurations is presented by plotting the reduced energy ϵ against ψ = ξ p /(5 F 2 + ξ p ) according to Edlén. It is concluded that the p 2 level values of S XI, Sc XVI, Ti XVII, V XVIII, Ni XV and Te III, and the p 3 level values of Al VII, Si VIII, P IX, Cl X, Se II and Xe IV need to be improved. Edlén's (1972) work on n = 2 and Svensson's (1971) work on n = 3 give a very satisfactory fit to our ψ-ϵ graphs. The ( F 2 - ξ p ) V s ψ graphs enable us to study coupling variations along the same and different isoelectronic sequences. The Z-dependence of the ground intervals 4 s 2 4 p 4 have been studied theoretically for the first time. The level values are represented, within less than 0.2% error, by semi-empirical formulae having 3–5 adjusted parameters and are based on data obtained from laboratory observations. The results provide means for checking laboratory and astrophycial identifications and measurements.

Spectral classifications in the Fe XIX to Fe XXIII isoelectronic sequences

Emission lines are classified belonging to 2s22pn-2s2pn+1 transition arrays in the ions Ti XVII, V XVII to XX, Mn XVIII, MN XIX, Fe XIX and Fe XX. The source of these ions is the plasma produced at metallic surfaces irradiated with a neodymium laser beam with a focused power density in the range of 1012 to 1013 W cm-2 at the target surface. The data reported can be applied to the interpretation of solar flare spectra.

Carbon-Like Spectra of Sc xvi, Ti xvii, and V xviii in the Range 16–22 Å

The carbon-like spectra of Sc xvi, Ti xvii, and V xviii are reported for the first time. We have classified 44 new lines in the region 16–22 Å. Some previously unidentified lines of Cl xii and Ar xiii are also classified. We extrapolated the levels of the ground configuration 2s2 2p2 by several methods and compared the calculations with the experimental results.