Theoretical Investigation On The Structure And Radiative Transition Properties Of W⁵⁴⁺ Ion

Tungsten(W)was selected as the cover material of the ITER first wall and the diver-tor due to its favorable thermal engineering and stable physical properties,such as high melting point and thermal conductivity,low sputtering for tritium and deuterium,low tritium deuterium retention rate etc..However,tungsten impurity ions might inevitably be produced during the interaction between the edge plasma and cover material.These impurity ions may be transported to the fusion core plasma,and be ionized further to produce highly charged W ions.But therse highly charged W ions can't be fully ionized,even in the high temperature fusion core plasma.These highly charged W ions will possi-bly cause large radiation loss by emitting high energy photons,which will lead to plasma disruption if the relative concentration of W ions in the core plasma is higher than about 10-5.Thus,evaluation,monitoring and controlling of tungsten impurity ions flow is very crucial to achieve and retain a stable fusion.Nevertheless,tiny amount of tungsten im-purity ions can also provide us with plenty of information about fusion plasmas such as electron density,electron temperature and ion temperature by their spectrum.Thus,it is indispensable to study the atomic structures and transition properties of various tungsten ions.Multi-configuration Dirac-Fock(MCDF)theory and restricted active space method(RAS)which implemented by the GRASP2K package are employed to study the structures and transition properties of the ground state configuration(3d2)and the first excited con-figuration(3p53d3)of W54+ ion,based on the electron correlation effects,Breit interaction and quantum electrodynamics effects(QED)are fully considered.The electron correlation effects of Valence-valence(VV),Core-valence(CV)and Core-core(CC)from {3s,3p,3d} orbitals,Breit interaction and QED effects of W54+ ion were investigated firstly by restricted active space method.The different electron correlation effects from {3s,3p} orbitals,Breit interaction and QED effects were shown play an im-portant role on the structures and transition properties of ground state configuration and the first excited configuration for W54+ ion.A reliable electron correlation model which can be employed to calculate the the struc-tures and transition data of ground state configuration and the first excited configuration for W54+ ion was constructed.The energy levels,lifetime ald electric dipole(E1),mag-netic dipole(M1),electric quadrupole(E2)and Magnetic quadrupole(M2)transition data(transition wavelengths,probabilities and oscillator strengths)among the energy levels were calculated in the present work.And the results were analyzed and discussed in detail.Firstly,the convergence property of M1,E2,E1 transition wavelength and probabilities with the systematic extension of active orbital sets was analyzed.The results indicate the convergence of transition wavelengths and probabilities is good with the increase of active orbital sets layer by layer,when all VV,CV and CC correlation effects from {3s,3p,3d}orbitals were considered.Secondly,comparing with the available experimental observation values,the present results are in good agreement with it.But compared with the theoret-ical values,the calculated results between us have some differences.It mainly due to the correlation effects from {3s,3p} orbitals and orbitals of higher main quantum number were omitted by other.It further indicates that the correlation effects from {3s,3p} orbitals and extend the active space until the calculation results convergent are very important.A set of accurate and comprehensive atomic data were calculated,when the electron correla-tion effects,Breit interaction and QED effects were considered sufficiently and effectively.These data are of great significance to investigate the structures and emissive characters etc.Moreover,in present work:(1)the correlation model used in the calculations is rea-sonable and efficient,which can be used to calculate the atomic structures of ground sate configuration and the first excited configuration for W54+ ion.So,in general,the similar correlation models may be employed to calculate the other ions of Ca-like isoelectonic se-quence.(2)the experiment results were verified and some newly,strong transition were predicted which were likely to be observed by some appropriate plasma or experiment conditions.In addition,it was found that a few E1 transitions which have large transi-tion probabilities in the range of previous EBIT observation haven't been observed.These spectral lines were analyzed by using simple collisional-radiative model base on FAC(Flex-ible Atomic Code).(3)The configuration mixing under the jj coupling for excited state levels in W54+ ion is strong,so the configuration wavefunctions having major components of atomic state wavefunction were together employed to mark the energy levels,which resolve the question of levels label disorder and distinguish two experimental Spectral lines which have the same label for the initial and final state designation.Finally,based on the above research,a large number of atomic data for W54+ ion were predicted.The 119 fine structure levels of ground state configurat,ion and the first excited configuration for W54+ ion,466 E1,2879 M1,4202 E2 and 660 M2 transition data between these levels were calculated.According to the comparison with the experimental and theoretical results and the discussion to the consistency of transition probabilities in Babushkin and Coulomb,the accuracy of atomic data were evaluated.The atomic data calculated in the present work approach the accuracy desired in the plasma modeling.