| Dielectronic Recombination(DR)process of highly charged ions is a very important atomic process for high-temperature astrophysical,laboratory and magnetic fusion plasmas.Tungsten is by far the heaviest element used in magnetic fusion as the plasma-facing material in present fusion device,namely the International Thermonuclear Experimental Reactor(ITER).The electron temperature of ITER’s plasma core is expected by design to achieve values of 20-30 ke V,and in that case,many highly charged ions of tungsten,such as W60+-W66+ are dominant.Accurate atomic data,including information on atomic transitions with wavelengths,line intensities and cross sections for ionization,excitation and recombination for a large range of charge states of tungsten are important and needed to develop diagnostics for measuring tungsten concentrations in fusion.In this article,the energy structures,radiative and auger properties,and the DR process are studied for the highly charged ions W66+-W60+ by using the the relativistic configuration interaction(RCI)approach and the multi-configuration Dirac-Fock(MCDF)theoretical methods.Main results include the following two parts:In the first part,using the FAC code based on the RCI method,the energy levels of W63+ ion related to the DR process of W64+ ion are systematically calculated.The important double excited states of LMn(n=3-20)and LNn’(n’=4-15)resonant series are included.To test our calculations,the GRASP code based on the MCDF method are also used for LMM-DR process,the agreement results are obtained with the FAC calculations.Compared with the results from NIST and EBIT measurements,the difference is less than 0.15%.It is found that the Breit and QED effects is important,which will increase the energy eigenvalue nearly 680 e V for the ground state of W63+.Detailed identification and analysis are performed for the stronger resonant peaks belong to each of the resonant series,it is showed that the LMM-DR spectrum is the strongest.Due to the strong relativistic effect,The DR spectra from 2p3/2 and 2p1/2 double excited states are distributed in different energy regions.The DR cross sections is obtained for the ground state of W64+ ion in the wide energy region 1.0-12 ke V by using Gaussian convolution with FWHF=50e V,ground state By using the same resolution(FWHM=50e V)as the EBIT experiment in Tokyo,Japan,was performed on the calculated DR strengths.The DR spectrum of the 1-12 ke V energy region was obtained and compared with the experimentally measured DR spectrum.The results showed that the theoretical results of this article can simulate and identify the resonance peaks belonging to the W64+ ion in the experimental spectrum very well.In the second part,the strongest LMM-DR processes are systematically studied for the iso-nuclear series ions of W66+-W60+.Our calculated energy levels and ionization energies are in good agreement with the NIST data.It is found that the radiative rates are larger than Auger rates for most of the double-excited state related with LMM-DR process that is typical of highly ionized atom.The DR spectrum and Auger transition spectrum are quite similar for the different highly charged tungsten ions.Considering the abundance for different charged tungsten ions existed in EBIT experiment,we obtained the total theoretical DR spectra and compared with the experimental spectrum measured on Tokyo-EBIT for 1-5 ke V electron energy regions.For most of the observed resonance peaks,our results are consistent with the experimental spectra.However,for the spectrum at higher energies,the theoretical cross-section is smaller than the experiment observing,that will be further studied in the further by considering such as the radiative recombination process,the contribution from other highly charged ions of tungsten,and accuracy abundance of different ions in EBIT experiment. |
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