Density and Temperature Correlations in the SOL; Implications for Gas Puff Imaging of Turbulence

Using a two‐dimensional turbulence model, a strong linear correlation is found between density and electron temperature within scrape‐off layer fluctuations. This has important implications for gas puff image interpretation for two commonly used lines, Dα and HeI (587.6 nm). Dα emission responds approximately linearly to proportional changes in the underlying plasma density and electron temperature, making image interpretation relatively straightforward. However, above ∼25 eV, HeI (587.6 nm) emission is approximately constant with proportional changes in density and electron temperature, so underlying plasma perturbations may go unseen. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)