Radiative recombination data for tungsten ions: III.  W14+W23+

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Highlights

  • Radiative recombination data for ten tungsten ions W14+–W23+ are presented.

  • Photoionization cross sections are also given.

  • Calculations are fully relativistic including all multipoles of the radiative field.

  • We use the Dirac–Fock method to obtain the electron wave functions.

  • The data are required for diagnostics and modeling fusion plasmas studied in ITER.

Abstract

This paper completes the cycle of our calculations of the radiative recombination and photoionization data for tungsten ions. Presented here are the photoionization and radiative recombination cross sections, radiative recombination rate coefficients, and radiated power loss rate coefficients for ten tungsten impurity ions from W14+ to W23+. These data are required in diagnostics and modeling fusion plasmas studied in such devices as ITER, ASDEX Upgrade, and EBIT. Partial photoionization cross sections have been fitted by an analytical expression with five fit parameters tabulated here. Total radiative recombination cross sections are presented in the electron energy range from 1 eV to ∼80 keV. Radiative recombination rates and radiated power loss rates are given in the temperature range from 104  K to 109  K. Calculations have been performed on the basis of the fully relativistic treatment of photoionization and radiative recombination taking into account all significant multipoles of the radiative field. Electron wave functions have been obtained by the Dirac–Fock method with the proper consideration of the electron exchange. The relativistic Maxwell–Jüttner distribution of continuum electrons has been used in calculations of radiative recombination rates and radiated power loss rates. This decreases values of the rates noticeably at a high temperature as compared to the usual non-relativistic Maxwell–Boltzmann distribution.

Introduction

The present paper completes our calculations for database involving the radiative recombination (RR) and photoionization data for tungsten ions  [1], [2], [3], [4], [5]. The database includes total RR cross sections (RRCS), fit parameters for partial photoionization cross sections (PCS), as well as partial and total RR rate coefficients (RR rates) and radiated power loss rate coefficients (RPL rates). Tabulated here are the data for additional ten tungsten ions from W14+ to W23+. Tungsten is assumed to be the plasma-facing material in modern tokamak reactors  [6], [7], [8]. Taking into consideration that the RR process and the reverse photoionization process are important mechanisms influencing the equilibria and the thermal balance of fusion plasmas, data on RR and photoionization for tungsten impurity ions are required for modeling and diagnostics of plasmas produced in the reactors.

Section snippets

Method of calculations

Method of calculations and its advantages have been described in detail in papers  [1], [2], [9] and in a book chapter  [3]. Here we remind that the calculations are based on the fully relativistic treatment of photoionization and RR. All significant multipoles of the radiative field are taken into account. We use the average-configuration Dirac–Fock method with the exact consideration of the electron exchange for calculations of the bound and continuum electron wave functions. Values of RR

Results and discussion

Fig. 1, Fig. 2, Fig. 3 demonstrate total RRCS, RR rates, and RPL rates, respectively, for four representative tungsten ions in the charge range 14q23. As is seen, curves σtot(Ek) and αtot(Ek) for ions with q20 have noticeable bends in the range ∼100–300 eV. This tendency brings into existence minima and maxima in theEk-dependence of σtot and αtot for the further low-charged tungsten ions (see  [1], data of Table 1 for W6+). As is evident from Fig. 3, the behavior of total RPL rates is

Conclusions

New accurate data on RR and photoionization are presented for ten tungsten impurity ions in the range W14+ W23+. The calculations complete the cycle of the RR and photoionization data for tungsten ions. Our database includes in aggregate RRCS, PCS, and RR/RPL rates for 61 tungsten ions from W14+ to the bare nucleus as well as RRCS and PCS for the ion W6+. The data are necessary for diagnostics and modeling fusion plasmas investigated in such devices as ITER, ASDEX Upgrade, and EBIT.

In all our

Acknowledgment

This work was funded through the International Atomic Energy Agency under Contract No. 16357/RBF which is gratefully acknowledged.

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