Relativistic Theoretical Study On The Dielectronic Recombination Of High Charged Tungsten Ions

The knowledge of accurate dielectronic recombination (DR) rates of heavy ions is crucial for the study of ionization balance of highly ionized elements in hot plasmas. The process therefore plays an important role in the theoretical modeling of plasmas, whether in the laboratory or in astrophysical sources such as the solar corona. This knowledge is also essential for the research of X-ray lasers especially for calculating the populating and depopulating of lasing levels.Tungsten will be used for a certain plasma-facing components in the divertor region of the International Thermonuclear Experimental Reactor (ITER), and will also be used for the diagnostics of the erosion of heavy species into the plasma. For divertor plasma modeling and radiative cooling studies, accurate atomic data for highly ionized tungsten ions are essential, especially data on recombination processes that are a major source of radiation losses.We calculate the dielectronic recombination rate coefficients of W³⁷⁺ ions by using the Flexible Atomic Code (FAC). The results are presented for total DR rate coefficients of the temperature from 1 to 5×10⁴ eV. It shows that the contribution from 4p subshell excitation dominates in the whole energy region, it larger than 4d subshell excitation near one order of magnitude. DR rate coefficients from 4s, 4p and 4d subshell excitations increase with the decreasing electron temperature in the low temperature. The contribution from 3d shell excitation play an additional important role in the total DR rate coefficients at high temperature, and the relative contributions from 3s, 3p and 3d subshell excitations increase smoothly with the increasing temperature. The relative contribution fromâ–³n = 2 core excitation increases smoothly with increasing temperature and is about 20% at 5500 eV. The radiative recombination (RR) and three-body recombination (TBR) rate coefficients, which are also two important recombination processes in plasmas. The results show that the DR rate coefficients are great than the RR rate coefficients and TBR rate coefficients for the whole energy region. Clearly, DR is predominate the ionization balance.Detailed calculations of DR rate coefficients of W⁴⁶⁺, W⁴⁴⁺ and W³⁸⁺ ions by using the Flexible Atomic Code (FAC). For W⁴⁶⁺ ions, when electron temperature kT_e>5 eV, the contribution from 3d subshell excitation dominates. And for W⁴⁴⁺ ions, the contribution from 4s subshell excitation dominates at low electron temperature and 3d subshell excitation dominates at higher electron temperature. For W³⁸⁺ ions, the contribution from 4p subshell excitation dominates in the whole energy region, and 3d shell excitation play an additional important role in the total DR rate coefficients at high temperature. The relative contribution fromâ–³n = 2 core excitation is about 26%,22.5% and 21% at 50000 eV, respectively.