Speaker
Description
The modeling and spectral interpretation of carbon impurities in laboratory fusion plasmas requires accurate electron-impact ionization and excitation data. The rate of ionization is often dominated by ionization from metastable and excited states, with low charge states of carbon also requiring non-perturbative quantum mechanical calculations. For such data to be useful, it needs to be coupled with accurate atomic data for electron-impact excitation. Thus, we aim to update the electron-impact ionization and excitation data available for neutral carbon (C I). We generalize the approach taken for hydrogen by Badnell (2008), and expand upon the use of the Dirac Atomic R-matrix Codes (DARC) in a similar way to the R-matrix with Pseudostates (RMPS) approach for the ionization of multi-electron systems. This allows both ionization and excitation rates to be calculated from the same initial target structure. The ionization cross sections from two distinct C I targets show good agreement with experimental data and other theoretical calculations for the ground level of C I. In addition, the DARC R-matrix with Pseudostates (DRMPS) method allows for non-perturbative level-resolved excited state ionization cross sections to be calculated, which we present for the lowest lying 42 levels of C I. Our level-resolved excitation collision strengths are in alignment with other theoretical sources. The availability of both electron-impact excitation and ionization rates allows for the determination of effective ionization rates through collisional radiative calculations. We show that for the temperatures and densities applicable to magnetically confined plasmas, the ionization contributions from excited levels have a non-trivial effect on the effective ionization rate coefficients of C I. The good agreement of both the ionization and excitation data with available measurements and other theoretical calculations provides confidence in the new DRMPS approach, demonstrating that it can be used for non-hydrogenic systems.