Ne IX and Ne X spectra on the JET tokamak

Abstract

Observations of H-like Ne x and He-like Ne IX soft X-ray emission line spectra have been made on the JET (Joint European Torus) tokamak. Recently calculated electron impact excitation rates for He-like neon are used in the derivation of the electron temperature sensitive line ratios G=((x+y+z)/w), R1=(1s3p1P1 to 1s2 1S0/w Lyalpha /w, and the electron density sensitive ratio R=(z/(x+y)), where w, x, y and z are the resonance line (1s2p 1P1 to 1s21S0), intercombination (1s2p3P2,1 to 1s2 1S0) and forbidden lines (1s2s3S1 to 1s21S0) respectively and Lyalpha is the H-like Lymanalpha , transition. Extensive modelling is carried out to allow for non-coronal conditions due to diffusion effects in these calculations, which are compared with experimental ratios from JET, where independent temperature and density measurements are available. Departures from equilibrium are found for both ohmic and additionally heated plasmas, resulting in significant changes to the G and Lyalpha /w ratios. The R ratio is approaching its upper density limit and is relatively unaffected by non-coronal conditions. Good agreement between the experimental and calculated ratios is found, giving an indication of the accuracy of the combination of the atomic data and transport employed in the calculations.