Theoretical Study On The Energy Structure And Dielectronic Recombination Processes Of Highly Charged Tungsten Ions

Dielectronic Recombination(DR)is one of the most important recombination processes in collisions between electrons and highly charged ions.DR is widely existed in high-temperature astrophysical,laboratory,magnetic,and inertial confinement fusion plasma.The study of DR process is of great significance for the in-depth understanding of ionization balance and energy transport in plasma,as well as the diagnosis of the plasma radiation spectrum,the temperature,and the density of electrons.Tungsten,as the preferred plasmas-facing material of ITER,is used in the strainer.As an impurity,highly charged tungsten ions are separated from the wall and diffused into the fusion plasma.On the one hand,it provided an important means for the diagnosis of the temperature and density of the plasma.On the other hand,the radiation of highly charged tungsten ions will also cause the energy loss of the plasma,resulting in the decrease of plasma temperature.To meet the needs of ITER fusion research,high precision atomic parameters of various highly charged tungsten ions are urgently needed.In this article,under the relativistic distort wave approximation,the energy structure and the DR process of highly charged Phosphorus to Nitrogen-like(W59+-W67+)ions were studied systematically by using the Flexible Atomic Code(FAC)based on relativistic configuration interaction method.The main work includes the following two aspects:Firstly,the DR process in the ground state(3s2 1S0)of Mg-like W62+ion is studied systematically.In the calculation,the resonance excited states(2s2p)73s23lnl',(2s2p)33s2n'1'n"1",(2s2p)73s312n1',and(2s2p)73s31n'1'n"1"(n=3-12,n'=4-5,n"=4-6)of W61+ions are included,in other words,the contribution of DR process and higher-order Trielectronic recombination(TR)process are taken into account.The results showed that the DR spectra of W62+ion are mainly distributed in the range of 1.5-3.0keV.One of the most important resonance peak is mainly from the contribution of(2s2p)73s23l3l' configuration complex.It is very important to consider the electron correlation from the configuration of resonance excitation for the calculation of accurate resonance DR spectrum,which can't be ignored.The DR cross section of W62+ion in the ground state is obtained by using Gaussian convolution(FWHM=50eV).The cross section is compared with Tokyo EBIT measured precision DR spectra.The results showed that the resonant position and relative resonant cross section calculated by theory agree well with the experiment.By applying the n'-3 extrapolation formula to estimate the high n resonance excitation configuration(n=13-1000),we got the rate coefficient of W62+ ion in the plasma environment,and compared with previous Preval,by using AUTOSTRUCTURE code based on tight coupling method results,found that about 12%of deviation between the two,the main reason is the contribution of the TR process is ignored in the calculation of Preval.Secondly,based on the study of Mg-like W62+ ion,similar calculations are adopted,including the consideration of the high-order TR process.In this paper,the DR process of P-like to N-like(W59+-W67+)ion is further studied,and the energy structure,radiation,and Auger rate of all resonance states are calculated.In the resonant recombination LMn(n=3-20)process of W59+-W67+ ions are calculated.The energy structure,resonance strength,and autoionization rate of the resonance state of W64+ and W63+ ions calculated in this paper are in good agreement with the previous theoretical calculations,and the deviation is generally less than 14.2%.For other W59+-W62+ and W65+-W67+ ions,there is no relevant data of resonance state for comparison,and the relevant data of these ions are also given here.In this paper,after further considering the abundance of ions in different charge states,the experimental spectrum in the energy range of 1.5-12keV is simulated.For the low energy region,the theoretical and experimental results are consistent,while for the high energy side,there are deviations in the results,which need further study,including the resonance recombination process of tungsten ions in other charge states and the resonance recombination process of LNn,etc.The calculated rate coefficients of W59+-W67+ iso-nuclear series ions are compared with the theoretical results of Preval et al.,and it is found that the total rate coefficients of iso-nuclear series ions will shift to the high energy side with the decrease of charge state.