Interpretation of capillary discharge EUV pinhole images using a ray-tracing code

A three-dimensional numerical ray-tracing code has been developed to consider the effects of optical refraction at VUV and extreme ultraviolet (EUV) wavelengths in the pinhole imaging of capillary discharge plasmas. An experimental pinhole imaging system is modelled and results are compared to images recorded from a fast ablative discharge in short polyethylene capillary. Refractive effects are only observed for electron densities greater than 3x1025 m-3 at the longest wavelengths. Thus it can be concluded that, for this experiment, electron density profiles can be obtained from pinhole image, and the ring structure observed in experiment is not due to refraction. (author)