Mo XIV Research Articles

Line identification of extreme ultraviolet spectra of Mo V to Mo XVIII in EAST tokamak

The presence of high-<i>Z</i> impurities in magnetically confined fusion devices has different influences on the confinement property of the plasma due to the high cooling rate of high-<i>Z</i> impurities. The first wall of EAST is equipped with molybdenum tiles, molybdenum particles sputtered from inevitable plasma-wall interaction enter into the plasma and become high-<i>Z</i> impurity. In this paper, four fast-time-response extreme ultraviolet (EUV) spectrometers, a system which is upgraded in the EAST 2021 campaign, are used to monitor the line emission from impurity ions in the 5–500 Å wavelength range simultaneously. The in-situ wavelength calibration is carried out accurately using several well-known emission lines of low- and medium-Z impurity ions. The observed spectral lines are carefully identified based on the National Institute of Standards Technology (NIST) database, previously published experimental data and the time evolution of the normalized line intensity of emission lines from impurity ions. At the lower electron temperature (<i>T</i><sub>e0</sub> = 1.5 keV), the EUV spectra emitted from molybdenum ions in the range of 5–485 Å are systematically identified in EAST discharges accompanied with spontaneous sputtering events. As a result, two unresolved transition arrays of molybdenum spectra composed of Mo<sup>19+</sup>-Mo<sup>24+</sup> (Mo XX-Mo XXV) and Mo<sup>16+</sup>-Mo<sup>29+</sup> (Mo XVII-Mo XXX) are observed in the ranges of 15–30 Å and 65–95 Å. In addition, several spectral lines of lower molybdenum ions of Mo<sup>4+</sup>-Mo<sup>17+</sup> (Mo V-Mo XVIII) in the ranges of 27–60 Å and 120–485 Å are observed and identified on EAST for the first time, including a few strong and isolated forbidden and resonant lines, e.g. Mo XII at 329.414 Å, 336.639 Å and 381.125 Å, Mo XIII at 340.909 Å and 352.994 Å, Mo XIV at 373.647 Å and 423.576 Å, Mo XV at 50.448 Å, 57.927 Å and 58.832 Å. Six spectral lines are newly observed in the range of 27–32 Å, i.e. (27.21 ± 0.01) Å, (27.37 ± 0.01) Å, (28.99 ± 0.01) Å, (30.81 ± 0.01) Å, (31.54 ± 0.01) Å and (31.83 ± 0.01) Å, which may be Mo XV-Mo XVIII spectral lines. As a result, twelve strong and isolated spectral lines are chosen in routine observation for impurity transport physical study. The identification of these spectral lines not only enriches the molybdenum atom database, but also provides a solid experimental data base for magnetically confined devices to study the behavior and transport in core and edge plasmas of high-Z impurity.

Excitation-autoionization, dielectronic recombination and line intensities in highly ionized CuI-like ions

Extended calculations for excitation-autoionization processes in the CuI isoelectronic sequence and for dielectronic recombination in the NiI sequence have been performed. As an example, the results of these computations for molybdenum ions are presented. On the basis of these results one interprets the unexpected weak intensities of the CuI-like Mo XIV 3 d 104 s-3 d 94 s4 f resonant transitions compared to the parent Mo XV 3 d 10-3 d 94 f transitions.

3d-4p transitions in the soft X-ray spectra of Mo XIV and of isoelectric Y to Ag ions, from a low-inductance vacuum spark

Eight lines of 3d 104s-3d 94s4p and 3d 104p-3d 94p 2 transitions of Cu I-like Y XI to Ag XIX ions are identified in the 30–80 Å range of spectra emitted from a low-inductance vacuum spark. Identification is based on isoelectronic analysis and comparison with ab-initio relativistic calculations.

3d–4p Transitions in the zinclike and copperlike ions Y x, xi; Zr xi, xii; Nb xii, xiii; and Mo xiii, xiv

Lines occurring as satellites on the long-wavelength side of the 3d10–3d94p resonance lines of Ni-like ions have been investigated with a low-inductance vacuum spark and a 10.7-m spectrograph for the elements Y, Zr, Nb, and Mo. The lines are interpreted as 3d104s–3d94s4p and 3d104p–3d94p2 transitions in the Cu-like ions Y xi, Zr xii, Nb xiii, and Mo xiv and 3d104s2–3d94s24p transitions in the Zn-like ions Y x, Zr xi, Nb xii, and Mo xiii. The spectra of the Cu-like ions were interpreted by generalized least-squares fits for the energy levels of the sequence of four ions. Thirty-nine levels of 3d94s4p were interpreted simultaneously with a root-mean-square deviation of 122 cm−1; forty-four levels of 3d94p2 were interpreted in the same way with a root-mean-square deviation of 200 cm−1. Line identifications and energy levels were obtained for the 3d107p configuration of the Cu-like ions Y xi–Mo xiv.

The molybdenum spectrum emitted by a tokamak plasma in the 300–500 Å range

Lines belonging to ionization states ranging from Mo VI to Mo XIV have been observed in the Alcator A tokamak plasma. New lines of Mo XIII, among them a forbidden magnetic quadrupole line, have been identified and classified.

Revised 6p^2P_1/2 level of Mo xiv

New observations of the 4s–6p transitions of Mo xiv have led to a revised identification for the 4d2D3/2–6p2P1/2 transition and a revised value for the 6p2P1/2 level.

EUV spectra of Mo XIV to Mo XXIX

Observations of the EUV spectra of Mo XIV to Mo XXIX have been made in the wavelength region from 5 to 50 nm by foil excitation of 22 to 200 MeV Mo ion beams. The results are compared with spectra observed in tokamak plasmas and light sources and with theoretical predictions.

Diagrammatic many-body perturbation theory applied to highly ionized atoms of the copper isoelectronic sequence

Many-body diagrammatic perturbation theory has been applied to the calculation of ionization energies and multiplet strengths for two highly ionized atoms of the copper isoelectronic sequence. A unified Hartree-Fock zeroth-order Hamiltonian the eigenfunctions of which include both open- and closed-shell orbitals has been constructed for systems with a single open shell. Correlation energies for the excited $4p$ states as well as the ground $4s$ states of Kr VIII and Mo XIV were computed by means of individual basis sets generated for each state. The distribution of the $3l\ensuremath{-}4{l}^{\ensuremath{'}}$ correlation energy among second- and higher-order terms differed significantly for the two ions. In Mo XIV, most of the correlation energy was concentrated in second-order, with small third-order effects. In Kr VIII, however, second-order results were substantially changed by higher-order diagrams, particularly in the case of the $4p$ state. Correlated multiplet strengths for the $4s^{2}S\ensuremath{-}4p^{2}P$ resonance transition were computed, including first-order corrections to the Hartree-Fock zeroth-order wave functions for both initial and final states. The results of these calculations are in excellent agreement with those of recent multiconfiguration Hartree-Fock calculations.

Spectrum and energy levels of thirteen-times ionized molybdenum (Mo xiv)

The spectrum of Mo xiv was observed with a low-inductance spark and a laser-produced plasma in the region from 70 to 630 A on the10.7-m grazing-incidence spectrograph at NBS. From the identification of 35 lines, a system of 22 energy levels was determined. The level system (Cu i isoelectronic sequence, 3d10nl) includes the series ns (n = 4–6), np (n = 4–6), nd (n = 4,5), nf(n = 4–6), and ng (n = 5–7). The observed energy levels are compared with Hartree-Fock calculations. The ionization energy is determined from the ng series (n = 5–7) to be 2 440 600 ± 300 cm−3 (302.60 ± 0.04 eV).

4s−4pResonance Transitions in Highly Charged Cu- and Zn-like Ions

The $4s\ensuremath{-}4p$ resonance transitions in the copperlike and zinclike ions from Rb to Mo have been observed by means of a low-inductance open spark and a 10.7-m grazing-incidence spectrograph. Lines belonging to highly charged ions could be distinguished by their abnormally large widths. The observations confirm the identification of the resonance lines of Mo xiii and Mo xiv in the Princeton University $\mathrm{ST}$ tokamak by Hinnov, Johnson, Meservey, and Dimock.

Energy Levels and Transition Probabilities in Mo XIV

An investigation is made of the energy levels in Mo XIV (Cu I isoelectronic sequence). Published material is combined with previously unreported measurements to obtain reasonably accurate energies for terms with n = 4, 5, 6, 7 and 8. For the ionization limit we find the value 2 441 ± 2 kK. These data are used to calculate transition probabilities, oscillator strengths and radiative lifetimes for a large number of transitions by means of a numerical Coulomb approximation procedure.

Highly Stripped Ions (Up to Mo XXXIII) and Forbidden Mo Lines in the Soft X-Ray Spectrum from TFR Tokamak

The spectrum of the TFR Tokamak has been observed in the range 5-100 Å. Identification of Mo XIV to Mo XXXIII lines originating from the limiter was achieved by comparison with the Mo spectrum emitted from a low-inductance vacuum spark, and with relativistic calculations. Some of the TFR lines were identified as forbidden transitions (electric quadrupole). The appearance of these lines depending on plasma parameters is discussed.

Electrical resistivity of neon plasmas in a Tokamak

In ST Tokamak discharges with hydrogen or helium as the working gas the measured plasma resistance is usually found to be slight but consistently larger (1.1-1.5 times) than the resistance calculated from measured electron temperature and ionic charge radial profiles. The discrepancy has been ascribed tentatively to undetected high-Z material (Mo or W) from the aperture limiter. Recent experiments with neon, with effective ionic charge Z=9-10 in the discharge, do show good agreement between measured and calculated resistance. In other respects the behaviour of the neon discharge differs only slightly and in the expected direction from hydrogen or helium discharges: larger power input, higher electron temperature, and higher radiation losses. Also, measurement of the intensities of the recently discovered resonance lines of Mo XIII and Mo XIV do indicate a molybdenum concentration in the discharges of the ST Tokamak that is adequate to account for the above mentioned discrepancies in the resistance of H and He plasmas.