Excitation rate coefficient measurements of Cu xiii and Cu xvii ions

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The absolute excitation rate coefficients for Cu xiii and Cu xvii optically allowed transitions have been measured using the Texas Experimental Tokamak (TEXT) tokamak. Cu is injected by the laser-ablation method at a time when the plasma has attained steady-state temperature and density profiles. The absolute intensities of the magnetic-dipole-forbidden transitions within the Cu xiii 3s²3p⁵ and the Cu xvii 3s²3p ground configurations are measured. The intensities of optically allowed vacuum-ultraviolet lines within the 3p⁴3d-3p⁵ transition array of Cu xiii and within the 3d-3p transition array of Cu xvii are measured with a 2.2-m grazing incidence spectrometer. This instrument is radiometrically calibrated in situ by using the branching-ratio technique. The absolute excitation rate coefficients are deduced from these measurements, assuming coronal equilibrium, optically thin line emission, and statistical population within the ground configuration. The experimental rate coefficients for these transition arrays are found to be 2.84×{}10^-8 cm³ s^-1 for Cu xiii at an electron temperature of 127 eV and 3.5×{}10^-8 cm³ s^-1 for Cu xvii at an electron temperature of 240 eV. These results are in good agreement with excitation rate coefficients computed in a distorted-wave approximation. The estimated uncertainty in the experimental values is ±{}70%.